WO2019061319A1

WO2019061319A1 - Narrowband physical random access channel capacity enhancement

Info

Publication number: WO2019061319A1
Application number: PCT/CN2017/104459
Authority: WO
Inventors: Peng Cheng; Hao Xu; Chao Wei; Wanshi Chen; Alberto Rico Alvarino; Le LIU; Xiao Feng Wang; Umesh PHUYAL
Original assignee: Qualcomm Incorporated
Priority date: 2017-09-29
Filing date: 2017-09-29
Publication date: 2019-04-04

Abstract

Methods, systems, and devices for wireless communications are described for enhancing narrowband physical random access channel (PRACH) capacity. To gain system access, a user equipment (UE) may identify, based on a preamble index, a set of PRACH resources having a specific hopping pattern. The UE may modify a single-tone random access (RACH) preamble transmission to increase the PRACH capacity by improving multiplexing capabilities at a base station. In some cases, the UE may perform a frequency shift on the RACH preamble to a shifted tone for transmission, either based on randomly selecting a shift value or based on a repetition index of the RACH preamble. In other cases, the UE may apply an orthogonal cover code (OCC) or a scrambling bit sequence to spread the single-tone RACH preamble. These techniques may improve UE multiplexing at the base station, and accordingly may increase the narrowband PRACH capacity.

Description

NARROWBAND PHYSICAL RANDOM ACCESS CHANNEL CAPACITY ENHANCEMENT

BACKGROUND

The following relates generally to wireless communication, and more specifically to narrowband physical random access channel (NPRACH) capacity enhancement.

Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power) . Examples of such multiple-access systems include fourth generation (4G) systems such as a Long Term Evolution (LTE) systems or LTE-Advanced (LTE-A) systems, and fifth generation (5G) systems which may be referred to as New Radio (NR) systems. These systems may employ technologies such as code division multiple access (CDMA) , time division multiple access (TDMA) , frequency division multiple access (FDMA) , orthogonal frequency division multiple access (OFDMA) , or discrete Fourier transform-spread-OFDM (DFT-S-OFDM) . A wireless multiple-access communications system may include a number of base stations or network access nodes, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE) .

In some wireless communications systems, a UE may initialize a system access procedure by transmitting an NPRACH or random access (RACH) preamble message in the physical random access channel (PRACH) . However, as the UE has yet to gain access to the base station, these PRACH resources may be shared with any other UEs attempting to access the system. In such a contention-based system, large numbers of UEs attempting to access the system simultaneously using the limited resources of the PRACH may result in collisions, unreliable system access procedures, and increased latency in the wireless communications system.

SUMMARY

The described techniques relate to improved methods, systems, devices, or apparatuses that support increasing physical random access channel (PRACH) capacity for single-tone preambles. Generally, the described techniques apply symbol spreading or frequency offsets to single-tone preambles. A user equipment (UE) may select a preamble index (e.g., randomly or pseudo-randomly) , and may identify PRACH resources associated with a hopping pattern. For example, the PRACH resources for each repetition may include multiple symbol groups, and may have variable hops between groups. The PRACH resources may frequency hop according to a cell-specific hopping pattern. The UE may select a preamble bit sequence or frequency offset to apply to the single-tone preamble transmitted on the identified PRACH resources. Preamble bit sequences may be of different lengths and each bit of the sequence may be applied to one symbol, a subset of contiguous symbols, or the sequence may be repeated and each bit cyclically applied to symbols of the single-tone preamble. Each symbol group may have one cyclic prefix, or additional cyclic prefixes may be inserted (e.g., one cyclic prefix for each subset of contiguous symbols or one cyclic prefix for each symbol) . The preamble bit sequences may be orthogonal cover codes (OCCs) .

In some cases, the single-tone preambles may have a sub-carrier spacing that is associated with a symbol length, where the single-tone preamble includes multiple symbols per symbol group. The frequency offsets may be determined by a frequency delta determined by the symbol period and number of symbols in each symbol group. Thus, a set of frequency offsets that are interstitial to the sub-carrier spacing may be used that are orthogonal to each other because of the length of the symbol group. UEs using the frequency offset may select (e.g., randomly or pseudo-randomly) one from the set of frequency offsets including a zero frequency offset (e.g., corresponding to frequencies used by legacy devices) , or not including the zero offset. In some cases, the preamble bit sequence or frequency offset may be associated with a different random access radio network temporary identifier (RA-RNTI) , the preamble index may depend on the preamble bit sequence or frequency offset, or a field of a random access response message may include a value corresponding to the preamble bit sequence or frequency offset.

A method of wireless communication is described. The method may include identifying, based at least in part on a preamble index, a set of PRACH resources for system access using a single-tone random access preamble, the set of PRACH resources having a frequency hopping pattern. The method may further include determining a preamble bit sequence for the system access, applying the preamble bit sequence to one or more symbols of the single-tone random access preamble to obtain a spread single-tone random access preamble, and transmitting the spread single-tone random access preamble for the system access in the set of PRACH resources.

An apparatus for wireless communication is described. The apparatus may include means for identifying, based at least in part on a preamble index, a set of PRACH resources for system access using a single-tone random access preamble, the set of PRACH resources having a frequency hopping pattern. The apparatus may further include means for determining a preamble bit sequence for the system access, means for applying the preamble bit sequence to one or more symbols of the single-tone random access preamble to obtain a spread single-tone random access preamble, and means for transmitting the spread single-tone random access preamble for the system access in the set of PRACH resources.

Another apparatus for wireless communication is described. The apparatus may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to identify, based at least in part on a preamble index, a set of PRACH resources for system access using a single-tone random access preamble, the set of PRACH resources having a frequency hopping pattern. The instructions may be further executable by the processor to determine a preamble bit sequence for the system access, apply the preamble bit sequence to one or more symbols of the single-tone random access preamble to obtain a spread single-tone random access preamble, and transmit the spread single-tone random access preamble for the system access in the set of PRACH resources.

A non-transitory computer-readable medium for wireless communication is described. The non-transitory computer-readable medium may include instructions executable by a processor to identify, based at least in part on a preamble index, a set of PRACH resources for system access using a single-tone random access preamble, the set of PRACH resources having a frequency hopping pattern. The instructions may be further executable by the processor to determine a preamble bit sequence for the system access, apply the preamble bit sequence to one or more symbols of the single-tone random access preamble to obtain a spread single-tone random access preamble, and transmit the spread single-tone random access preamble for the system access in the set of PRACH resources.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, applying the preamble bit sequence to the one or more symbols of the single-tone random access preamble comprises applying each bit value of the preamble bit sequence to a corresponding symbol of the single-tone random access preamble.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the preamble bit sequence comprises an orthogonal cover code (OCC) scrambling sequence. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, a bit length of the preamble bit sequence may be equal to a symbol length of the single-tone random access preamble.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, a bit length of the preamble bit sequence may be less than a symbol length of the single-tone random access preamble, and wherein applying each bit value of the preamble bit sequence to the corresponding symbol of the plurality of repetitions of the single-tone random access preamble comprises cyclically applying each bit value of a plurality of cycles of the preamble bit sequence to corresponding symbols of the single-tone random access preamble.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, each symbol group of the single-tone random access preamble comprises a cyclic prefix prior to each symbol of the symbol group. In other examples of the method, apparatus, and non-transitory computer-readable medium described above, each symbol group of the single-tone random access preamble comprises a single cyclic prefix.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, applying the preamble bit sequence to the one or more symbols of the single-tone random access preamble comprises applying each bit value of the preamble bit sequence to a contiguous subset of symbols of the single-tone random access preamble. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the single-tone random access preamble comprises a cyclic prefix prior to each contiguous subsets of symbols of the single-tone random access preamble.

Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for determining the preamble bit sequence based at least in part on a table stored in memory, a UE identifier, a base sequence seed, a coverage level grouping, or any combination thereof.

Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for randomly generating the preamble index associated with the spread single-tone random access preamble. Some examples of the method, apparatus, and non-transitory computer- readable medium described above may further include processes, features, means, or instructions for determining resources for transmitting the spread single-tone random access preamble, the preamble bit sequence, or both based at least in part on the preamble index and a preamble generator function.

Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for identifying a random access preamble response associated with the spread single-tone random access preamble based at least in part on an RNTI corresponding to the preamble bit sequence or on a field of the random access preamble response corresponding to the preamble bit sequence.

An additional method of wireless communication is described. The method may include determining a plurality of PRACH resource sets for system access, each of the plurality of PRACH resource sets associated with a frequency hopping pattern； receiving a spread single-tone random access preamble over a PRACH resource set of the plurality of PRACH resource sets, the spread single-tone random access preamble spread with one of a plurality of preamble bit sequences； and transmitting a random access preamble response in response to the received spread single-tone random access preamble, wherein the random access preamble response is based at least in part on the one of the plurality of preamble bit sequences used for the spread single-tone random access preamble.

An apparatus for wireless communication is described. The apparatus may include means for determining a plurality of PRACH resource sets for system access, each of the plurality of PRACH resource sets associated with a frequency hopping pattern； means for receiving a spread single-tone random access preamble over a PRACH resource set of the plurality of PRACH resource sets, the spread single-tone random access preamble spread with one of a plurality of preamble bit sequences； and means for transmitting a random access preamble response in response to the received spread single-tone random access preamble, wherein the random access preamble response is based at least in part on the one of the plurality of preamble bit sequences used for the spread single-tone random access preamble.

Another apparatus for wireless communication is described. The apparatus may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to determine a plurality of PRACH resource sets for system access, each of the plurality of PRACH resource sets associated with a frequency hopping pattern； receive a spread single-tone random access preamble over a PRACH resource set of the plurality of PRACH resource sets, the spread single-tone random access preamble spread with one of a plurality of preamble bit sequences； and transmit a random access preamble response in response to the received spread single-tone random access preamble, wherein the random access preamble response is based at least in part on the one of the plurality of preamble bit sequences used for the spread single-tone random access preamble.

A non-transitory computer-readable medium for wireless communication is described. The non-transitory computer-readable medium may include instructions executable by a processor to determine a plurality of PRACH resource sets for system access, each of the plurality of PRACH resource sets associated with a frequency hopping pattern； receive a spread single-tone random access preamble over a PRACH resource set of the plurality of PRACH resource sets, the spread single-tone random access preamble spread with one of a plurality of preamble bit sequences； and transmit a random access preamble response in response to the received spread single-tone random access preamble, wherein the random access preamble response is based at least in part on the one of the plurality of preamble bit sequences used for the spread single-tone random access preamble.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the random access preamble response comprises a preamble index to be decoded using an RNTI, wherein the RNTI may be based at least in part on the one of the plurality of preamble bit sequences.

Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for determining a preamble index based at least in part on a preamble generator function, the one of the plurality of preamble bit sequences, and resources used for receiving the spread single-tone random access preamble.

Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for transmitting system information comprising an indication of the plurality of preamble bit sequences. Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for transmitting system information comprising an indication of one or more group indexes associated with different coverage levels for a cell, wherein the one of the plurality of preamble bit sequences may be based at least in part on a group index of the one or more group indexes.

A further method of wireless communication is described. The method may include identifying, based at least in part on a preamble index, a set of PRACH resources for system access using a single-tone random access preamble, the set of PRACH resources having a frequency hopping pattern. The method may further include selecting a frequency offset value from a plurality of frequency offset values and transmitting the single-tone random access preamble for the system access in the set of PRACH resources according to the frequency hopping pattern and the selected frequency offset value.

An apparatus for wireless communication is described. The apparatus may include means for identifying, based at least in part on a preamble index, a set of PRACH resources for system access using a single-tone random access preamble, the set of PRACH resources having a frequency hopping pattern. The apparatus may further include means for selecting a frequency offset value from a plurality of frequency offset values and means for transmitting the single-tone random access preamble for the system access in the set of PRACH resources according to the frequency hopping pattern and the selected frequency offset value.

Another apparatus for wireless communication is described. The apparatus may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to identify, based at least in part on a preamble index, a set of PRACH resources for system access using a single-tone random access preamble, the set of PRACH resources having a frequency hopping pattern. The instructions may be further executable by the processor to select a frequency offset value from a plurality of frequency offset values and transmit the single-tone random access preamble for the system access in the set of PRACH resources according to the frequency hopping pattern and the selected frequency offset value.

A non-transitory computer-readable medium for wireless communication is described. The non-transitory computer-readable medium may include instructions executable by a processor to identify, based at least in part on a preamble index, a set of PRACH resources for system access using a single-tone random access preamble, the set of PRACH resources having a frequency hopping pattern. The instructions may be further executable by the processor to select a frequency offset value from a plurality of frequency offset values and transmit the single-tone random access preamble for the system access in the set of PRACH resources according to the frequency hopping pattern and the selected frequency offset value.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, selecting the frequency offset value comprises selecting the frequency offset value from a plurality of orthogonal frequency shift values for the single-tone random access preamble.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, a first type of UEs may be associated with a first tone spacing for transmission of single-tone random access preambles, wherein the plurality of frequency offset values correspond to frequency shifts interstitial to the first tone spacing. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the plurality of frequency offset values comprises a zero offset value.

Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for receiving, from a base station, an indication of the plurality of orthogonal frequency shift values.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, selecting the frequency offset value comprises selecting the frequency offset value based at least in part on the frequency hopping pattern and a repetition number of the single-tone random access preamble.

Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for randomly generating the preamble index associated with the single-tone random access preamble, wherein selecting the frequency offset value may be based at least in part on the preamble index and a preamble generator function.

Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for identifying a random access preamble response associated with the single-tone random access preamble based at least in part on an RNTI corresponding to the selected frequency offset value or on a field of the random access preamble response corresponding to the selected frequency offset value.

A further method of wireless communication is described. The method may include determining a plurality of PRACH resource sets for system access, each of the plurality of PRACH resource sets associated with a frequency hopping pattern； receiving a single-tone random access preamble over a PRACH resource set of the plurality of PRACH resource sets, the single-tone random access preamble transmitted using the frequency hopping pattern and one of a plurality of frequency offset values； and transmitting a random access preamble response in response to the received single-tone random access preamble, wherein the random access preamble response is based at least in part on the one of the plurality of frequency offset values used for transmission of the single-tone random access preamble.

An apparatus for wireless communication is described. The apparatus may include means for determining a plurality of PRACH resource sets for system access, each of the plurality of PRACH resource sets associated with a frequency hopping pattern； means for receiving a single-tone random access preamble over a PRACH resource set of the plurality of PRACH resource sets, the single-tone random access preamble transmitted using the frequency hopping pattern and one of a plurality of frequency offset values； and means for transmitting a random access preamble response in response to the received single-tone random access preamble, wherein the random access preamble response is based at least in part on the one of the plurality of frequency offset values used for transmission of the single-tone random access preamble.

Another apparatus for wireless communication is described. The apparatus may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to determine a plurality of PRACH resource sets for system access, each of the plurality of PRACH resource sets associated with a frequency hopping pattern； receive a single-tone random access preamble over a PRACH resource set of the plurality of PRACH resource sets, the single-tone random access preamble transmitted using the frequency hopping pattern and one of a plurality of frequency offset values； and transmit a random access preamble response in response to the received single-tone random access preamble, wherein the random access preamble response is based at least in part on the one of the plurality of frequency offset values used for transmission of the single-tone random access preamble.

A non-transitory computer-readable medium for wireless communication is described. The non-transitory computer-readable medium may include instructions executable by a processor to determine a plurality of PRACH resource sets for system access, each of the plurality of PRACH resource sets associated with a frequency hopping pattern； receive a single-tone random access preamble over a PRACH resource set of the plurality of PRACH resource sets, the single-tone random access preamble transmitted using the frequency hopping pattern and one of a plurality of frequency offset values； and transmit a random access preamble response in response to the received single-tone random access preamble, wherein the random access preamble response is based at least in part on the one of the plurality of frequency offset values used for transmission of the single-tone random access preamble.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the random access preamble response comprises a preamble index to be decoded using an RNTI, wherein the RNTI may be based at least in part on the one of the plurality of frequency offset values.

Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for determining a preamble index based at least in part on a preamble generator function, the one of the plurality of frequency offset values, and resources used for receiving the single-tone random access preamble.

Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for transmitting system information comprising an indication of the plurality of frequency offset values.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the plurality of frequency offset values correspond to orthogonal frequency shifts of the single-tone random access preamble.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGs. 1 and 2 illustrate examples of systems for wireless communication that support narrowband physical random access channel (NPRACH) capacity enhancement in accordance with aspects of the present disclosure.

FIG. 3 illustrates an example of a process for increasing NPRACH capacity based on tone granularity that supports NPRACH capacity enhancement in accordance with aspects of the present disclosure.

FIG. 4 illustrates an example of orthogonal cover code (OCC) spreading that supports NPRACH capacity enhancement in accordance with aspects of the present disclosure.

FIG. 5 illustrates an example of symbol-level spreading that supports NPRACH capacity enhancement in accordance with aspects of the present disclosure.

FIG. 6 illustrates an example of symbol set-level spreading that supports NPRACH capacity enhancement in accordance with aspects of the present disclosure.

FIG. 7 illustrates an example of symbol-level sequence spreading that supports NPRACH capacity enhancement in accordance with aspects of the present disclosure.

FIGs. 8 and 9 illustrate examples of process flows that support NPRACH capacity enhancement in accordance with aspects of the present disclosure.

FIGs. 10 through 12 show block diagrams of a device that supports NPRACH capacity enhancement in accordance with aspects of the present disclosure.

FIG. 13 illustrates a block diagram of a system including a UE that supports NPRACH capacity enhancement in accordance with aspects of the present disclosure.

FIGs. 14 through 16 show block diagrams of a device that supports NPRACH capacity enhancement in accordance with aspects of the present disclosure.

FIG. 17 illustrates a block diagram of a system including a base station that supports NPRACH capacity enhancement in accordance with aspects of the present disclosure.

FIGs. 18 through 21 illustrate methods for NPRACH capacity enhancement in accordance with aspects of the present disclosure.

DETAILED DESCRIPTION

Some wireless communications systems may support increasing physical random access channel (PRACH) capacity for single-tone preambles. The PRACH capacity may be increased using symbol spreading or frequency offsets. Implementing symbol spreading or frequency offsets may allow for increased multiplexing of user equipment (UEs) , resulting in a greater channel capacity for the PRACH. Many wireless communications systems may include both “legacy” UEs (e.g., UEs not configured to use these techniques) and “enhanced” UEs (e.g., UEs enhanced to use these techniques) . The following methods and techniques may support both of these types of UEs, where the enhanced UEs may utilize the increased capacity of the PRACH.

A UE may select a preamble index (e.g., randomly or pseudo-randomly) , and may identify PRACH resources associated with a hopping pattern. For example, the PRACH resources for each repetition may include multiple symbol groups, and may have variable hops between groups. The PRACH resources may frequency hop according to a cell-specific hopping pattern. To implement symbol spreading or frequency offsets in the PRACH, the UE may select a preamble bit sequence or frequency offset to apply to the single-tone preamble transmitted on the identified PRACH resources. Preamble bit sequences may be of different lengths and each bit of the sequence may be applied to one symbol, a subset of contiguous symbols, or the sequence may be repeated and each bit cyclically applied to symbols of the single-tone preamble. Each symbol group may have one cyclic prefix, or additional cyclic prefixes may be inserted (e.g., one cyclic prefix for each subset of contiguous symbols or one cyclic prefix for each symbol) . The preamble bit sequences may be orthogonal cover codes (OCCs) .

Aspects of the disclosure are initially described in the context of wireless communications systems. Additional aspects are described with respect to processes and spreading techniques for increasing NPRACH capacity. Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to narrowband physical random access channel capacity enhancement.

FIG. 1 illustrates an example of a wireless communications system 100 in accordance with various aspects of the present disclosure. The wireless communications system 100 includes base stations 105, UEs 115, and a core network 130. In some examples, the wireless communications system 100 may be a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A) network, or a New Radio (NR) network. In some cases, wireless communications system 100 may support enhanced broadband communications, ultra-reliable (e.g., mission critical) communications, low latency communications, or communications with low-cost and low-complexity devices.

Base stations 105 may wirelessly communicate with UEs 115 via one or more base station antennas. Base stations 105 described herein may include or may be referred to by those skilled in the art as a base transceiver station, a radio base station, an access point, a radio transceiver, a NodeB, an eNodeB (eNB) , a next-generation Node B or giga-nodeB (either of which may be referred to as a gNB) , a Home NodeB, a Home eNodeB, or some other suitable terminology. Wireless communications system 100 may include base stations 105 of different types (e.g., macro or small cell base stations) . The UEs 115 described herein may be able to communicate with various types of base stations 105 and network equipment including macro eNBs, small cell eNBs, gNBs, relay base stations, and the like.

Each base station 105 may be associated with a particular geographic coverage area 110 in which communications with various UEs 115 is supported. Each base station 105 may provide communication coverage for a respective geographic coverage area 110 via communication links 125, and communication links 125 between a base station 105 and a UE 115 may utilize one or more carriers. Communication links 125 shown in wireless communications system 100 may include uplink transmissions from a UE 115 to a base station 105, or downlink transmissions, from a base station 105 to a UE 115. Downlink transmissions may also be called forward link transmissions while uplink transmissions may also be called reverse link transmissions.

The geographic coverage area 110 for a base station 105 may be divided into sectors making up only a portion of the geographic coverage area 110, and each sector may be associated with a cell. For example, each base station 105 may provide communication coverage for a macro cell, a small cell, a hot spot, or other types of cells, or various combinations thereof. In some examples, a base station 105 may be movable and therefore provide communication coverage for a moving geographic coverage area 110. In some examples, different geographic coverage areas 110 associated with different technologies may overlap, and overlapping geographic coverage areas 110 associated with different technologies may be supported by the same base station 105 or by different base stations 105. The wireless communications system 100 may include, for example, a heterogeneous LTE/LTE-A or NR network in which different types of base stations 105 provide coverage for various geographic coverage areas 110.

The term “cell” refers to a logical communication entity used for communication with a base station 105 (e.g., over a carrier) , and may be associated with an identifier for distinguishing neighboring cells (e.g., a physical cell identifier (PCID) , a virtual cell identifier (VCID) ) operating via the same or a different carrier. In some examples, a carrier may support multiple cells, and different cells may be configured according to different protocol types (e.g., machine-type communication (MTC) , narrowband Internet-of-Things (NB-IoT) , enhanced mobile broadband (eMBB) , or others) that may provide access for different types of devices. In some cases, the term “cell” may refer to a portion of a geographic coverage area 110 (e.g., a sector) over which the logical entity operates.

UEs 115 may be dispersed throughout the wireless communications system 100, and each UE 115 may be stationary or mobile. A UE 115 may also be referred to as a mobile device, a wireless device, a remote device, a handheld device, or a subscriber device, or some other suitable terminology, where the “device” may also be referred to as a unit, a station, a terminal, or a client. A UE 115 may also be a personal electronic device such as a cellular phone, a personal digital assistant (PDA) , a tablet computer, a laptop computer, or a personal computer. In some examples, a UE 115 may also refer to a wireless local loop (WLL) station, an Internet of Things (IoT) device, an Internet of Everything (IoE) device, or an MTC device, or the like, which may be implemented in various articles such as appliances, vehicles, meters, or the like.

Some UEs 115, such as MTC or IoT devices, may be low cost or low complexity devices, and may provide for automated communication between machines (e.g., via Machine-to-Machine (M2M) communication) . M2M communication or MTC may refer to data communication technologies that allow devices to communicate with one another or a base station 105 without human intervention. In some examples, M2M communication or MTC may include communications from devices that integrate sensors or meters to measure or capture information and relay that information to a central server or application program that can make use of the information or present the information to humans interacting with the program or application. Some UEs 115 may be designed to collect information or enable automated behavior of machines. Examples of applications for MTC devices include smart metering, inventory monitoring, water level monitoring, equipment monitoring, healthcare monitoring, wildlife monitoring, weather and geological event monitoring, fleet management and tracking, remote security sensing, physical access control, and transaction-based business charging.

Some UEs 115 may be configured to employ operating modes that reduce power consumption, such as half-duplex communications (e.g., a mode that supports one-way communication via transmission or reception, but not transmission and reception simultaneously) . In some examples half-duplex communications may be performed at a reduced peak rate. Other power conservation techniques for UEs 115 include entering a power saving “deep sleep” mode when not engaging in active communications, or operating over a limited bandwidth (e.g., according to narrowband communications) . In some cases, UEs 115 may be designed to support critical functions (e.g., mission critical functions) , and a wireless communications system 100 may be configured to provide ultra-reliable communications for these functions.

In some cases, a UE 115 may also be able to communicate directly with other UEs 115 (e.g., using a peer-to-peer (P2P) or device-to-device (D2D) protocol) . One or more of a group of UEs 115 utilizing D2D communications may be within the geographic coverage area 110 of a base station 105. Other UEs 115 in such a group may be outside the geographic coverage area 110 of a base station 105, or be otherwise unable to receive transmissions from a base station 105. In some cases, groups of UEs 115 communicating via D2D communications may utilize a one-to-many (1: M) system in which each UE 115 transmits to every other UE 115 in the group. In some cases, a base station 105 facilitates the scheduling of resources for D2D communications. In other cases, D2D communications are carried out between UEs 115 without the involvement of a base station 105.

Base stations 105 may communicate with the core network 130 and with one another. For example, base stations 105 may interface with the core network 130 through backhaul links 132 (e.g., via an S1 or other interface) . Base stations 105 may communicate with one another over backhaul links 134 (e.g., via an X2 or other interface) either directly (e.g., directly between base stations 105) or indirectly (e.g., via core network 130) .

The core network 130 may provide user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. The core network 130 may be an evolved packet core (EPC) , which may include at least one mobility management entity (MME) , at least one serving gateway (S-GW) , and at least one Packet Data Network (PDN) gateway (P-GW) . The MME may manage non-access stratum (e.g., control plane) functions such as mobility, authentication, and bearer management for UEs 115 served by base stations 105 associated with the EPC. User IP packets may be transferred through the S-GW, which itself may be connected to the P-GW. The P-GW may provide IP address allocation as well as other functions. The P-GW may be connected to the network operators IP services. The operators IP services may include access to the Internet, Intranet (s) , an IP Multimedia Subsystem (IMS) , or a Packet-Switched (PS) Streaming Service.

At least some of the network devices, such as a base station 105, may include subcomponents such as an access network entity, which may be an example of an access node controller (ANC) . Each access network entity may communicate with UEs 115 through a number of other access network transmission entities, which may be referred to as a radio head, a smart radio head, or a transmission/reception point (TRP) . In some configurations, various functions of each access network entity or base station 105 may be distributed across various network devices (e.g., radio heads and access network controllers) or consolidated into a single network device (e.g., a base station 105) .

Wireless communications system 100 may operate using one or more frequency bands, typically in the range of 300 MHz to 300 GHz. Generally, the region from 300 MHz to 3 GHz is known as the ultra-high frequency (UHF) region or decimeter band, since the wavelengths range from approximately one decimeter to one meter in length. UHF waves may be blocked or redirected by buildings and environmental features. However, the waves may penetrate structures sufficiently for a macro cell to provide service to UEs 115 located indoors. Transmission of UHF waves may be associated with smaller antennas and shorter range (e.g., less than 100 km) compared to transmission using the smaller frequencies and longer waves of the high frequency (HF) or very high frequency (VHF) portion of the spectrum below 300 MHz.

Wireless communications system 100 may also operate in a super high frequency (SHF) region using frequency bands from 3 GHz to 30 GHz, also known as the centimeter band. The SHF region includes bands such as the 5 GHz industrial, scientific, and medical (ISM) bands, which may be used opportunistically by devices that can tolerate interference from other users.

Wireless communications system 100 may also operate in an extremely high frequency (EHF) region of the spectrum (e.g., from 30 GHz to 300 GHz) , also known as the millimeter band. In some examples, wireless communications system 100 may support millimeter wave (mmW) communications between UEs 115 and base stations 105, and EHF antennas of the respective devices may be even smaller and more closely spaced than UHF antennas. In some cases, this may facilitate use of antenna arrays within a UE 115. However, the propagation of EHF transmissions may be subject to even greater atmospheric attenuation and shorter range than SHF or UHF transmissions. Techniques disclosed herein may be employed across transmissions that use one or more different frequency regions, and designated use of bands across these frequency regions may differ by country or regulating body.

In some cases, wireless communications system 100 may utilize both licensed and unlicensed radio frequency spectrum bands. For example, wireless communications system 100 may employ License Assisted Access (LAA) , LTE-Unlicensed (LTE-U) radio access technology, or NR technology in an unlicensed band such as the 5 GHz ISM band. When operating in unlicensed radio frequency spectrum bands, wireless devices such as base stations 105 and UEs 115 may employ listen-before-talk (LBT) procedures to ensure a frequency channel is clear before transmitting data. In some cases, operations in unlicensed bands may be based on a CA configuration in conjunction with CCs operating in a licensed band (e.g., LAA) . Operations in unlicensed spectrum may include downlink transmissions, uplink transmissions, peer-to-peer transmissions, or a combination of these. Duplexing in unlicensed spectrum may be based on frequency division duplexing (FDD) , time division duplexing (TDD) , or a combination of both.

In some examples, base station 105 or UE 115 may be equipped with multiple antennas, which may be used to employ techniques such as transmit diversity, receive diversity, multiple-input multiple-output (MIMO) communications, or beamforming. For example, wireless communications system 100 may use a transmission scheme between a transmitting device (e.g., a base station 105) and a receiving device (e.g., a UE 115) , where the transmitting device is equipped with multiple antennas and the receiving devices are equipped with one or more antennas. MIMO communications may employ multipath signal propagation to increase the spectral efficiency by transmitting or receiving multiple signals via different spatial layers, which may be referred to as spatial multiplexing. The multiple signals may, for example, be transmitted by the transmitting device via different antennas or different combinations of antennas. Likewise, the multiple signals may be received by the receiving device via different antennas or different combinations of antennas. Each of the multiple signals may be referred to as a separate spatial stream, and may carry bits associated with the same data stream (e.g., the same codeword) or different data streams. Different spatial layers may be associated with different antenna ports used for channel measurement and reporting. MIMO techniques include single-user MIMO (SU-MIMO) where multiple spatial layers are transmitted to the same receiving device, and multiple-user MIMO (MU-MIMO) where multiple spatial layers are transmitted to multiple devices.

Beamforming, which may also be referred to as spatial filtering, directional transmission, or directional reception, is a signal processing technique that may be used at a transmitting device or a receiving device (e.g., a base station 105 or a UE 115) to shape or steer an antenna beam (e.g., a transmit beam or receive beam) along a spatial path between the transmitting device and the receiving device. Beamforming may be achieved by combining the signals communicated via antenna elements of an antenna array such that signals propagating at particular orientations with respect to an antenna array experience constructive interference while others experience destructive interference. The adjustment of signals communicated via the antenna elements may include a transmitting device or a receiving device applying certain amplitude and phase offsets to signals carried via each of the antenna elements associated with the device. The adjustments associated with each of the antenna elements may be defined by a beamforming weight set associated with a particular orientation (e.g., with respect to the antenna array of the transmitting device or receiving device, or with respect to some other orientation) .

In one example, a base station 105 may use multiple antennas or antenna arrays to conduct beamforming operations for directional communications with a UE 115. For instance, some signals (e.g. synchronization signals, reference signals, beam selection signals, or other control signals) may be transmitted by a base station 105 multiple times in different directions, which may include a signal being transmitted according to different beamforming weight sets associated with different directions of transmission. Transmissions in different beam directions may be used to identify (e.g., by the base station 105 or a receiving device, such as a UE 115) a beam direction for subsequent transmission and/or reception by the base station 105. Some signals, such as data signals associated with a particular receiving device, may be transmitted by a base station 105 in a single beam direction (e.g., a direction associated with the receiving device, such as a UE 115) . In some examples, the beam direction associated with transmissions along a single beam direction may be determined based at least in in part on a signal that was transmitted in different beam directions. For example, a UE 115 may receive one or more of the signals transmitted by the base station 105 in different directions, and the UE 115 may report to the base station 105 an indication of the signal it received with a highest signal quality, or an otherwise acceptable signal quality. Although these techniques are described with reference to signals transmitted in one or more directions by a base station 105, a UE 115 may employ similar techniques for transmitting signals multiple times in different directions (e.g., for identifying a beam direction for subsequent transmission or reception by the UE 115) , or transmitting a signal in a single direction (e.g., for transmitting data to a receiving device) .

A receiving device (e.g., a UE 115, which may be an example of a mmW receiving device) may try multiple receive beams when receiving various signals from the base station 105, such as synchronization signals, reference signals, beam selection signals, or other control signals. For example, a receiving device may try multiple receive directions by receiving via different antenna subarrays, by processing received signals according to different antenna subarrays, by receiving according to different receive beamforming weight sets applied to signals received at a plurality of antenna elements of an antenna array, or by processing received signals according to different receive beamforming weight sets applied to signals received at a plurality of antenna elements of an antenna array, any of which may be referred to as “listening” according to different receive beams or receive directions. In some examples a receiving device may use a single receive beam to receive along a single beam direction (e.g., when receiving a data signal) . The single receive beam may be aligned in a beam direction determined based at least in part on listening according to different receive beam directions (e.g., a beam direction determined to have a highest signal strength, highest signal-to-noise ratio, or otherwise acceptable signal quality based at least in part on listening according to multiple beam directions) .

In some cases, the antennas of a base station 105 or UE 115 may be located within one or more antenna arrays, which may support MIMO operations, or transmit or receive beamforming. For example, one or more base station antennas or antenna arrays may be co-located at an antenna assembly, such as an antenna tower. In some cases, antennas or antenna arrays associated with a base station 105 may be located in diverse geographic locations. A base station 105 may have an antenna array with a number of rows and columns of antenna ports that the base station 105 may use to support beamforming of communications with a UE 115. Likewise, a UE 115 may have one or more antenna arrays that may support various MIMO or beamforming operations.

In some cases, wireless communications system 100 may be a packet-based network that operate according to a layered protocol stack. In the user plane, communications at the bearer or Packet Data Convergence Protocol (PDCP) layer may be IP-based. A Radio Link Control (RLC) layer may in some cases perform packet segmentation and reassembly to communicate over logical channels. A Medium Access Control (MAC) layer may perform priority handling and multiplexing of logical channels into transport channels. The MAC layer may also use hybrid automatic repeat request (HARQ) to provide retransmission at the MAC layer to improve link efficiency. In the control plane, the Radio Resource Control (RRC) protocol layer may provide establishment, configuration, and maintenance of an RRC connection between a UE 115 and a base station 105 or core network 130 supporting radio bearers for user plane data. At the Physical (PHY) layer, transport channels may be mapped to physical channels.

In some cases, UEs 115 and base stations 105 may support retransmissions of data to increase the likelihood that data is received successfully. HARQ feedback is one technique of increasing the likelihood that data is received correctly over a communication link 125. HARQ may include a combination of error detection (e.g., using a cyclic redundancy check (CRC) ) , forward error correction (FEC) , and retransmission (e.g., automatic repeat request (ARQ) ) . HARQ may improve throughput at the MAC layer in poor radio conditions (e.g., signal-to-noise conditions) . In some cases, a wireless device may support same-slot HARQ feedback, where the device may provide HARQ feedback in a specific slot for data received in a previous symbol in the slot. In other cases, the device may provide HARQ feedback in a subsequent slot, or according to some other time interval.

Time intervals in LTE or NR may be expressed in multiples of a basic time unit, which may, for example, refer to a sampling period of T_s ＝ 1/30, 720, 000 seconds. Time intervals of a communications resource may be organized according to radio frames each having a duration of 10 milliseconds (ms) , where the frame period may be expressed as T_f ＝ 307, 200 T_s. The radio frames may be identified by a system frame number (SFN) ranging from 0 to 1023. Each frame may include 10 subframes numbered from 0 to 9, and each subframe may have a duration of 1 ms. A subframe may be further divided into 2 slots each having a duration of 0.5 ms, and each slot may contain 6 or 7 modulation symbol periods (e.g., depending on the length of the cyclic prefix prepended to each symbol period) . Excluding the cyclic prefix, each symbol period may contain 2048 sampling periods. In some cases a subframe may be the smallest scheduling unit of the wireless communications system 100, and may be referred to as a transmission time interval (TTI) . In other cases, a smallest scheduling unit of the wireless communications system 100 may be shorter than a subframe or may be dynamically selected (e.g., in bursts of shortened TTIs (sTTIs) or in selected component carriers using sTTIs) .

In some wireless communications systems, a slot may further be divided into multiple mini-slots containing one or more symbols. In some instances, a symbol of a mini-slot or a mini-slot may be the smallest unit of scheduling. Each symbol may vary in duration depending on the subcarrier spacing or frequency band of operation, for example. Further, some wireless communications systems may implement slot aggregation in which multiple slots or mini-slots are aggregated together and used for communication between a UE 115 and a base station 105.

The term “carrier” refers to a set of radio frequency spectrum resources having a defined physical layer structure for supporting communications over a communication link 125. For example, a carrier of a communication link 125 may include a portion of a radio frequency spectrum band that is operated according to physical layer channels for a given radio access technology. Each physical layer channel may carry user data, control information, or other signaling. A carrier may be associated with a pre-defined frequency channel (e.g., an E-UTRA absolute radio frequency channel number (EARFCN) ) , and may be positioned according to a channel raster for discovery by UEs 115. Carriers may be downlink or uplink (e.g., in an FDD mode) , or be configured to carry downlink and uplink communications (e.g., in a TDD mode) . In some examples, signal waveforms transmitted over a carrier may be made up of multiple sub-carriers (e.g., using multi-carrier modulation (MCM) techniques such as OFDM or DFT-s-OFDM) .

The organizational structure of the carriers may be different for different radio access technologies (e.g., LTE, LTE-A, NR, etc. ) . For example, communications over a carrier may be organized according to TTIs or slots, each of which may include user data as well as control information or signaling to support decoding the user data. A carrier may also include dedicated acquisition signaling (e.g., synchronization signals or system information, etc. ) and control signaling that coordinates operation for the carrier. In some examples (e.g., in a carrier aggregation configuration) , a carrier may also have acquisition signaling or control signaling that coordinates operations for other carriers.

Physical channels may be multiplexed on a carrier according to various techniques. A physical control channel and a physical data channel may be multiplexed on a downlink carrier, for example, using time division multiplexing (TDM) techniques, frequency division multiplexing (FDM) techniques, or hybrid TDM-FDM techniques. In some examples, control information transmitted in a physical control channel may be distributed between different control regions in a cascaded manner (e.g., between a common control region or common search space and one or more UE-specific control regions or UE-specific search spaces) .

A carrier may be associated with a particular bandwidth of the radio frequency spectrum, and in some examples the carrier bandwidth may be referred to as a “system bandwidth” of the carrier or the wireless communications system 100. For example, the carrier bandwidth may be one of a number of predetermined bandwidths for carriers of a particular radio access technology (e.g., 1.4, 3, 5, 10, 15, 20, 40, or 80 MHz) . In some examples, each served UE 115 may be configured for operating over portions or all of the carrier bandwidth. In other examples, some UEs 115 may be configured for operation using a narrowband protocol type that is associated with a predefined portion or range (e.g., set of subcarriers or RBs) within a carrier (e.g., “in-band” deployment of a narrowband protocol type) .

In a system employing MCM techniques, a resource element may consist of one symbol period (e.g., a duration of one modulation symbol) and one subcarrier, where the symbol period and subcarrier spacing are inversely related. The number of bits carried by each resource element may depend on the modulation scheme (e.g., the order of the modulation scheme) . Thus, the more resource elements that a UE 115 receives and the higher the order of the modulation scheme, the higher the data rate may be for the UE 115. In MIMO systems, a wireless communications resource may refer to a combination of a radio frequency spectrum resource, a time resource, and a spatial resource (e.g., spatial layers) , and the use of multiple spatial layers may further increase the data rate for communications with a UE 115.

Devices of the wireless communications system 100 (e.g., base stations 105 or UEs 115) may have a hardware configuration that supports communications over a particular carrier bandwidth, or may be configurable to support communications over one of a set of carrier bandwidths. In some examples, the wireless communications system 100 may include base stations 105 and/or UEs that can support simultaneous communications via carriers associated with more than one different carrier bandwidth.

Wireless communications system 100 may support communication with a UE 115 on multiple cells or carriers, a feature which may be referred to as carrier aggregation (CA) or multi-carrier operation. A UE 115 may be configured with multiple downlink CCs and one or more uplink CCs according to a carrier aggregation configuration. Carrier aggregation may be used with both FDD and TDD component carriers.

In some cases, wireless communications system 100 may utilize enhanced component carriers (eCCs) . An eCC may be characterized by one or more features including wider carrier or frequency channel bandwidth, shorter symbol duration, shorter TTI duration, or modified control channel configuration. In some cases, an eCC may be associated with a carrier aggregation configuration or a dual connectivity configuration (e.g., when multiple serving cells have a suboptimal or non-ideal backhaul link) . An eCC may also be configured for use in unlicensed spectrum or shared spectrum (e.g., where more than one operator is allowed to use the spectrum) . An eCC characterized by wide carrier bandwidth may include one or more segments that may be utilized by UEs 115 that are not capable of monitoring the whole carrier bandwidth or are otherwise configured to use a limited carrier bandwidth (e.g., to conserve power) .

In some cases, an eCC may utilize a different symbol duration than other CCs, which may include use of a reduced symbol duration as compared with symbol durations of the other CCs. A shorter symbol duration may be associated with increased spacing between adjacent subcarriers. A device, such as a UE 115 or base station 105, utilizing eCCs may transmit wideband signals (e.g., according to frequency channel or carrier bandwidths of 20, 40, 60, 80 MHz, etc. ) at reduced symbol durations (e.g., 16.67 microseconds) . A TTI in eCC may consist of one or multiple symbol periods. In some cases, the TTI duration (that is, the number of symbol periods in a TTI) may be variable.

Wireless communications systems such as an NR system may utilize any combination of licensed, shared, and unlicensed spectrum bands, among others. The flexibility of eCC symbol duration and subcarrier spacing may allow for the use of eCC across multiple spectrums. In some examples, NR shared spectrum may increase spectrum utilization and spectral efficiency, specifically through dynamic vertical (e.g., across frequency) and horizontal (e.g., across time) sharing of resources.

In some wireless communications systems, UEs 115 may initiate system access procedures by transmitting RACH preamble messages. A UE 115 may identify, based on a randomly-generated preamble index or a preamble index signaled by a base station 105, a set of PRACH resources having a specific frequency hopping pattern. The UE 115 may transmit a single-tone RACH preamble in the PRACH resources to gain system access. In some cases, the UE 115 may modify the single-tone RACH preamble transmission to increase the PRACH capacity (e.g., by improving UE 115 multiplexing at the base station 105) . In some cases, the UE 115 may perform a frequency shift on the RACH preamble transmission, based on either a randomly selected a shift value or based on a repetition index of the RACH preamble. In other cases, the UE may apply a scrambling or OCC sequence or a preamble bit sequence to spread the single-tone RACH preamble. These modifications to the single-tone RACH preamble transmission may introduce additional levels of preamble separation, which may allow for increased potential UE 115 multiplexing at the base station 105.

FIG. 2 illustrates an example of a wireless communications system 200 that supports NPRACH capacity enhancement in accordance with various aspects of the present disclosure. The wireless communications system 200 may include base station 105-a covering geographic area 110-a and UE 115-a, which may be examples of a base station 105, a geographic coverage area 110-a, and a UE 115, as described with reference to FIG. 1. Base station 105-a may transmit to UE 115-a over downlink transmission link 205, and UE 115-a may transmit to base station 105-a over uplink transmission link 210. To gain system access, UE 115-a may transmit an NPRACH transmission 215 on uplink transmission link 210. The NPRACH transmission 215 may include one or more RACH preamble repetitions 220, which may be examples of single-tone RACH preambles. In some cases, a single-tone RACH preamble may be referred to as a RACH preamble message, a RACH initial message, a RACH Message 1 (Msg1) , or some similar term. In some cases, UE 115-a may modify the single-tone RACH preamble to increase NPRACH capacity.

In some wireless systems (e.g., narrowband internet-of-things (NB-IoT) systems) , a base station 105 may manage system access for a large number of UEs 115 in a geographic coverage area 110. For example, to support massive machine type communications (mMTC) , base station 105-a may provide system access for one million UEs 115—or more—per square kilometer. Such a large number of UEs 115 may result in latency issues within the wireless communications system 200. Base station 105-a may have a latency threshold or latency requirement for mMTC. For example, a latency requirement may specify a maximum 10 second latency for a 20 byte packet measured at a maximum coupling loss (MCL) (e.g., 164 dB), for a significant majority of the UEs 115, such as 99％of the served UEs 115. To meet such a latency threshold, the wireless communications system 200 may implement NPRACH capacity enhancements for single-tone NPRACH transmissions. These NPRACH capacity enhancements may allow base station 105-a to increase the potential multiplexing of UEs 115, reducing system access latency for the wireless communications system 200.

The NPRACH capacity enhancements may be applied to random hopping, repetition-based NPRACH design. For example, in such an NPRACH design, a UE 115, such as UE 115-a, may determine PRACH resources to use for system access. UE 115-a may transmit an NPRACH transmission 215 on uplink transmission link 215 in the determined PRACH resources. In some cases, an NPRACH transmission 215 may include one or more RACH preamble repetitions 220, each of which may be associated with a repetition index. For example, RACH preamble repetition 220-a may be associated with a first repetition index, RACH preamble repetition 220-b may be associated with a second, RACH preamble repetition 220-c may be associated with third, and RACH preamble repetition 220-d may be associated with a fourth, as each of these transmissions may be associated with a same system access procedure and preamble index.

UE 115-a may transmit the RACH preamble repetitions 220 at different frequencies based on random hopping. For example, UE 115-a may begin transmitting RACH preamble repetition 220-c at one tone, and may begin transmitting RACH preamble repetition 220-d at a different tone, the tones separated by frequency hop value 225. In some cases, frequency hop value 225 may be a random or pseudo-random multiple of a configured hop value (e.g., 3.75 kHz) . In certain example, these random hopping values may be cell-specific random hopping values between RACH preamble repetitions 220. Additionally or alternatively, RACH preamble repetitions 220 may have a maximum frequency hop value 225, for example, based on the PRACH resources (e.g., a maximum hop of 12 tones) .

Each RACH preamble repetition 220 may include a number of symbol groups 230. As illustrated, the RACH preamble repetitions 220 may each contain four symbol groups 230. A symbol group 230 may include one or more cyclic prefixes 235 and one or more symbols 240 (e.g., one preceding cyclic prefix 235, followed by five symbols 240, as illustrated) . The cyclic prefixes 235 and symbols 240 may share a common length (e.g., 266.67 μs) , or may have different lengths (e.g., 66.67 μs for a cyclic prefix 235 and 266.67 μs for a symbol 240) . The symbol groups 230 may be transmitted at certain tones (e.g., 3.75 kHz tones) based on random frequency selection or hopping. For example, a first symbol group 230 of the RACH preamble repetition 220 may be transmitted at a randomly or pseudo-randomly selected tone within the PRACH resources. The second symbol group 230 may hope up or down 1 tone from the first symbol group 230. Similarly, the third and fourth symbol groups 230 may be separated by a frequency hop value 245 of 1 tone. However, the second and third symbol groups 230 may be separated by a frequency hop value 250 of 6 tones. These frequency hop values 245 and 250 are given as examples, and other frequency hop values may be implemented between symbol groups 230. In some cases, the determination whether to hop up or down tones may be a random or pseudo-random determination by the UE 115, or may be a function of the index of the current tone within a set of tones.

In some cases, the symbols 240 in each symbol group 230 may be modulated by a constant value (e.g., a symbol group 230 may be an example of sinusoidal signal with a frequency an integer multiple of a tone spacing such as 3.75 kHz. However, because of the length of the symbol group 230, symbol groups 230 that are adjacent by the tone spacing of 3.75 kHz may have intermediate frequency locations that are also orthogonal to the symbol groups 230 if transmitted with the same length.

In a first aspect, base station 105-a and UE 115-a may enhance the NPRACH capacity using the PRACH tone granularity. For example, base station 105 may randomly or pseudo-randomly select a frequency shift value from a set of frequency shift values. Based on the selected frequency shift value, UE 115-a may shift the frequency resources for the NPRACH transmission 215 or a RACH preamble repetition 220. For example, UE 115-a may shift the transmissions to either a different tone, or some intermediate tone. For example, based on the possible frequency shift values, each initial tone for an NPRACH transmission 215 may correspond to a number of potential shifted tones, that may have a smaller inter-tone spacing than the initial tones. This may provide increased multiplexing of UEs 115 based on the number of potential frequency shift values to select from.

In a second aspect, base station 105-a and UE 115-a may enhance the NPRACH capacity using OCC spreading. UE 115-a may apply an orthogonal scrambling sequence to RACH preamble repetitions 220, so that multiple UEs 115 may transmit RACH preambles 220 in the same time-frequency resources. For example, for an OCC of length four, base station 105-a may multiplex RACH preamble transmissions for four UEs 115 in same resources based on code domain orthogonality. Accordingly, implementing OCCs may provide increased multiplexing of UEs 115 based on the length of the selected OCC.

In a third aspect, base station 105-a and UE 115-a may enhance the NPRACH capacity using preamble bit sequences. UE 115-a may select a preamble bit sequence for spreading RACH preamble repetitions 220. In some cases, UE 115-a may perform symbol-level spreading by applying each bit of the preamble bit sequence to a corresponding symbol 240 of the RACH preamble repetition 220. In other cases, UE 115-a may perform symbol set-level spreading by applying each bit of the preamble bit sequence to a set of symbols 240 of the RACH preamble repetition 220. In yet other cases, UE 115-a may perform symbol-level sequence spreading by applying the preamble bit sequence cyclically to the RACH preamble repetition 220. In some cases, this may provide increased multiplexing of UEs 115 based on the number of bits in the preamble bit sequence.

In the second or third aspects, base station 105-a may separate UEs 115 into several groups based on coverage. For example, UEs 115 in different coverage levels may use or be assigned different groups of scrambling, OCC, or bit sequences. Base station 105-a may indicate a group index for one or more UEs 115 for different coverage levels in a transmission of system information.

In a fourth aspect, base station 105-a and UE 115-a may enhance the NPRACH capacity using pattern-specific repetition hopping patterns. In some cases, a wireless communications system 200 may implement cell-specific random frequency hopping between RACH preamble repetitions 220. Base station 105-a and UE 115-a may additionally implement pattern-specific repetition frequency hopping. This additional hopping pattern may add another dimension to RACH preamble separation. Base station 105-a may increase UE 115 multiplexing based on detecting the different hopping patterns. For example, UEs 115 may implement an additional X tone offset based on the cell-specific hopping pattern used by the UE 115 and the repetition index of the RACH preamble repetition 220. For example, different repetition indexes may correspond to different values of X. Some possible values for X may include 1, 2, or 4, or any other number of tones supported for frequency hopping, and UE 115-a may hop either up or down based on the pattern-specific repetition hopping pattern. In some cases, base station 105-a and UE 115-a may have a maximum tone offset, X_max (e.g., the tone offset may be less than 6 tones) .

In some cases, pattern-specific repetition hopping patterns may be implemented in wireless communications systems 200 with infrequent UE 115 traffic, a large number of repetitions, or both. Base station 105-a and UE 115-a may transmit signals to indicate the additional hopping pattern. In some cases, both base station 105-a and UE 115-a may include a preamble index calculation function that receives time-frequency resources and an additional hopping pattern index as inputs, and outputs a preamble index or identifier. In other cases, the preamble index or identifier may be based on the additional hopping pattern index and a PRACH preamble.

Similar to above, base station 105-a and UE 115-a may transmit signals to indicate a frequency shift index, an OCC index, or a bit sequence index. In some cases, base station 105-a and UE 115-a may each include a preamble index generation function, which may take time-frequency resources for transmitting the NPRACH transmission 215 or RACH preamble repetitions 220 as input, along with an index of the indexes listed above, and may output a preamble index. Based on both containing this generation function, base station 105-a and UE 115-a may each be able to determine preamble indexes, frequency shift indexes, OCC indexes, or bit sequence indexes. In other cases, base station 105-a and UE 115-a may implement preamble indexes dependent on frequency shift indexes, OCC indexes, or bit sequence indexes and a PRACH preamble. In yet other cases, the wireless devices may use different RA-RNTIs for different index values (e.g., associated with a frequency shift, OCC, or bit sequence) . Additionally or alternatively, base station 105-a may include a field in a RACH preamble response, which may be transmitted in response to a RACH preamble repetition 220, that indicates the frequency shift index, the OCC index, or the bit sequence index.

In some cases, base station 105-a may signal information on downlink transmission link 205 for enhancing NPRACH capacity. For example, base station 105-a may transmit a PRACH or NPRACH order in downlink control information (DCI) . UE 115-a may detect the DCI, and may transmit the NPRACH transmission 215 based on the order. The NPRACH order may include a field indicating a narrowband physical downlink control channel (NPDCCH) order, a field indicating a starting number of repetitions, a field indicating a tone index, or some combination of these or other additional fields. For example, to implement enhanced NPRACH capacity, base station 105-a may include one or more additional fields. The additional fields may indicate one or more frequency shift indexes for UEs 115, an OCC index, a bit sequence index, an additional hopping pattern index, or any combination of these fields. UE 115-a may transmit the NPRACH transmission 215 based on the received parameters, which may implement one or more of the above described techniques for NPRACH capacity enhancement.

FIG. 3 illustrates an example of process 300 for increasing NPRACH capacity based on tone granularity that supports NPRACH capacity enhancement in accordance with various aspects of the present disclosure. The process 300 may include multiple steps for determining new NPRACH tone locations 335, which may provide for enhanced NPRACH capacity by utilizing an NPRACH tone granularity. The process 300 may be performed by a wireless device, such as a UE 115 described with reference to FIGs. 1 and 2.

At 305, a UE 115 may randomly or pseudo-randomly select a frequency resource for NPRACH transmission. The frequency resource may be selected based on a PRACH configuration signaled by a base station 105 (e.g., in a system information block (SIB) or in downlink control information (DCI) ) . Each symbol group of an NPRACH transmission repetition, such as symbol groups 230 described with reference to FIG. 2, may be an example of a signal allocated at a certain tone for single-tone transmission. At 310, the UE 115 may perform NPRACH signal generation to generate this signal. In some cases, any UEs 115 within a cell may utilize a same NPRACH signal generator. For example, as illustrated, the signal generation may be independent of the frequency shift selection, so UEs 115 configured to select a frequency shift and UEs 115 not configured to select a frequency shift may implement the same NPRACH signal generation process. The NPRACH signal generator may generate a single-tone RACH preamble, and may assign the single-tone RACH preamble to a tone. For example, for the common NPRACH signal generator, the single-tone RACH preamble may be assigned to one of the previous NPRACH tone locations 330, which may be separated by a standard tone spacing 345, such as 3.75 kHz.

At 315, the UE 115 may randomly or pseudo-randomly select a frequency shift value from a set of possible frequency shift values. The set of possible frequency shift values may contain a number of shifts, which in some cases may be uniformly distributed in the frequency domain based on an enhanced tone spacing 350. For example, if the UE 115 selects from a set of five frequency shift values, the values may include [-2 - 1 0 1 2] *0.75 kHz for an enhanced tone spacing 350 of 0.75 kHz (i.e., potential frequency shifts of -1.5, -0.75, 0, 0.75, or 1.5 kHz from an initial tone) . At 320, the UE 115 may apply the selected frequency shift to the generated NPRACH signal, shifting the signal from the initial tone to a shifted tone. As illustrated in FIG. 3, the set of five frequency shift values described above may correspond to shifting a signal from an initial tone positioned at previous NPRACH tone location 340 to one of new NPRACH tone locations 335 or new NPRACH tone location 340 (e.g., in the case where a zero offset value is selected) . These new NPRACH tone locations 335 and 340 may correspond to orthogonal signals. At 325, the UE 115 may transmit the NPRACH signal in the shifted frequency resources.

In some cases, a UE 115 configured to perform random frequency shift selection may contain an indication (e.g., in a table stored in memory) of the set of possible frequency shift values. In other cases, a base station 105 may transmit an indication of the set of possible frequency shift values to the UE 115. In such cases, the indication of the frequency shift values may be transmitted in system information, and in some cases the frequency shift values may be cell-specific.

Some wireless systems may include one or more UEs 115 configured to select a random frequency shift, along with one or more UEs 115 not configured for random frequency shifts (e.g., referred to as “legacy” UEs 115) . In these systems, legacy UEs 115 may not apply frequency shifts to NPRACH signals (i.e., may use a “frequency shift” value of 0, which may be referred to as a zero offset value, or may skip the operations of 315 and 320) , regardless of an intended cell for the NPRACH signal. Additionally, in these systems, UEs 115 configured to perform the random frequency shift may or may not share the zero offset value. That is, the “frequency shift” value of 0 may or may not be included in the set of possible frequency shift values. Alternatively, the UEs 115 may either select from the full set of possible frequency shift values, or may select from a subset of the set of possible frequency shift values not including the 0 “frequency shift” value. A base station 105 may perform UE 115 multiplexing based on the frequency shifts. The number of possible frequency shift values may correspond to the improvement in UE 115 multiplexing (e.g., a system with five possible frequency shift values may provide five times more potential UE 115 multiplexing) .

FIG. 4 illustrates an example of OCC spreading 400 that supports NPRACH capacity enhancement in accordance with various aspects of the present disclosure. The OCC spreading 400 may be performed by a wireless device, such as a UE 115 as described with reference to FIGs. 1 and 2. For an NPRACH transmission 405 including multiple RACH preamble repetitions 410, the UE 115 may perform symbol spreading using an OCC 415 (e.g., using cover code values of +1/-1/+1/-1, as illustrated) to introduce orthogonality in the code domain. Accordingly, a base station 105 may multiplex RACH preambles from multiple UEs 115 in the same time-frequency resources based on the code domain orthogonality.

For example, UEs 115 may utilize a number of RACH preamble repetitions 410 (e.g., four repetitions) . The UEs 115 may implement an OCC 415 or scrambling sequence of length X. In some cases, the number of repetitions and the length, X, of the OCC 415 may be equal. For example, as illustrated, the UEs 115 may perform orthogonal spreading on four RACH preamble repetitions 410 using a scrambling sequence [1, -1, 1, -1] . In some cases, the orthogonality may be obtained by determining a tensor product 420 of the set of repetitions and the OCC 415. Implementing an X-length OCC 415 may increase NPRACH capacity by X times. For example, the potential multiplexing based on the OCC 415 is illustrated in graph 425. Resources 430-a may be utilized by a first UE 115 for RACH preamble transmission (e.g., using four repetitions 410) , while resources 430-b, 430-c, and 430-d may be used by a second, third, and fourth UE 115, respectively. As these four sets of resources 430 are orthogonal in the code domain, a base station 105 may multiplex the RACH preambles of the UEs 115 in same time-frequency resources. In some cases, the potential values for X may be based on a channel coherence time or frequency offset. For example, for a frequency offset of less than 10 Hz, the OCC 415 length X may be selected (e.g., by a base station 105, UE 115, or based on a set configuration) from a set of values between 6 and 10.

In some cases, a UE 115 may determine to implement an OCC 415 based on a coverage level of the UE 115. For example, a UE 115 in deep coverage (e.g., a UE 115 with a number of repetitions greater than some threshold number of repetitions) may determine to implement an OCC 415. Implementing OCCs 415 for UEs 115 in deep coverage may provide NPRACH capacity enhancement for these UEs 115. In some cases, UEs 115 in deep coverage may need longer NPRACH access than other UEs 115, so the UEs 115 in deep coverage may receive a greater benefit from using an OCC 415. In other cases, any UE 115 within a cell may utilize an OCC 415 for initiating a system access procedure.

A UE 115 may perform OCC 415 sequence generation to determine the OCC 415 to use for OCC spreading 400. In some cases, the UE 115 may determine the OCC 415 based on an indication of potential OCCs 415 (e.g., in a table in memory) , and may select one OCC 415 from the set of potential OCCs 415 (e.g., based on a random or pseudo-random process, based on a cell identifier, based on a UE 115 identifier, etc. ) . In other cases, the UE 115 may determine the OCC 415 based on a generation function, which may take a UE identifier, a base sequence seed, or both as inputs, and may output an OCC 415 for OCC spreading 400.

FIG. 5 illustrates an example of symbol-level spreading 500 that supports NPRACH capacity enhancement in accordance with various aspects of the present disclosure. Symbol-level spreading 500 may be performed on a RACH preamble 505, which may be an example of one repetition within an NPRACH transmission. The RACH preamble 505 may include multiple symbol groups 510, each including one or more cyclic prefixes 515 and one or more symbols 520, and spaced in time and frequency, for example, as described with reference to FIG. 2. Symbol-level spreading 500 may utilize a bit sequence, which may be referred to as a preamble bit sequence or a multiplexing preamble bit sequence. For a given bit sequence length, a base station 105 may increase UE 115 multiplexing by that amount. For example, as illustrated, a bit sequence of length 20 may increase potential UE 115 multiplexing by 20 times.

The bit sequence may introduce an additional dimension to a RACH preamble 505. A UE 115 performing symbol-level spreading 500 may apply spreading on a symbol-by- symbol basis. For example, each bit 525 of the bit sequence may be applied to a single symbol 520 of the RACH preamble 505, for example, using a tensor product 530. For example, as illustrated, a -1 value for the first bit 530 of the bit sequence may be applied to the first symbol 520 of the first symbol group 510. For the symbol-level spreading 500 to be successful, a UE 115 may maintain a one-to-one ratio between bits 525 in the bit sequence and symbols 520 in the RACH preamble 505. In some cases, to determine or generate the bit sequence, a UE 115 may include an indication of the possible sequences (e.g., in a table in memory) , and may select one sequence from the set of possible sequences (e.g., based on a random or pseudo-random process, based on a cell identifier, etc. ) . In other cases, the UE 115 may determine the bit sequence based on a sequence generation function, which may take a UE identifier, a base sequence seed, or both as inputs, and may output a bit sequence for symbol spreading.

In some cases, to handle the symbol-level spreading 500, a UE 115 may implement a frame structure where a cyclic prefix 515 is inserted before each symbol 520 of the RACH preamble. Such a frame structure may allow for performing a fast Fourier transform (FFT) operation while applying the bit sequence for symbol-level spreading 500. For example, in contrast, some NPRACH frame structures may include a single preceding cyclic prefix followed by multiple symbols in each symbol group. In these cases, a receiver may use a portion of each symbol as the cyclic prefix for the following symbol. However, performing scrambling on the symbol group will result in phase rotation. A receiver receiving the scrambled symbol group may not be able to perform FFT processing, as the receiver may not be able to determine if the portion of each symbol can properly function as the cyclic prefix for the following symbol. In some cases, this may also result in loss of orthogonality at the receiver for different subcarriers. Accordingly, inserting a cyclic prefix 515 before each symbol 520 may avoid the issues of phase rotation.

FIG. 6 illustrates an example of symbol set-level spreading 600 that supports NPRACH capacity enhancement in accordance with various aspects of the present disclosure. Symbol set-level spreading 600 may be performed on a RACH preamble 605, which may be an example of one repetition within an NPRACH transmission. The RACH preamble 605 may include multiple symbol groups 610, each including one or more cyclic prefixes 615 and one or more symbols 620, and spaced in time and frequency, for example, as described with reference to FIG. 2. Symbol set-level spreading 600 may utilize a bit sequence, which may be referred to as a preamble bit sequence or a multiplexing preamble bit sequence. For a given bit sequence length, a base station 105 may increase UE 115 multiplexing by that amount. For example, as illustrated, a bit sequence of length 8 may increase potential UE 115 multiplexing by 8 times.

As opposed to symbol-level spreading 500, as described above, symbol set-level spreading 600 may apply spreading on a symbol set-by-symbol set basis. For example, each bit 625 of the bit sequence may be applied to a single symbol set 635 of RACH preamble 605, for example, using a tensor product 630. To support FFT operations, a UE 115 implementing symbol set-level spreading 600 may use a frame structure where a cyclic prefix 615 is inserted before each symbol set 635. Since a same bit 625 is applied to each symbol 620 of a symbol set 635, these symbols 620 will not experience phase rotation, and therefore a portion of a symbol 620 of a symbol set 635 may function as the cyclic prefix for the following symbol 620. Accordingly, for RACH preambles 605 with equal numbers of symbols 620, implementing symbol set-level spreading 600 as opposed to symbol-level spreading 500 may decrease the cyclic prefix 615 overhead in the transmission, but also decreases the potential UE 115 multiplexing factor. In some cases, a UE 115 may determine how to apply a bit sequence based on the tradeoff between cyclic prefix overhead and UE 115 multiplexing factor. For example, in some cases, the UE 115 may determine whether to perform symbol-level spreading 500 or symbol set-level spreading 600, or may determine a size of the symbol sets 635 for symbol set-level spreading 600, based on a threshold cyclic prefix overhead or a threshold UE 115 multiplexing factor.

In some cases, to determine or generate the bit sequence, a UE 115 may include an indication of the possible sequences (e.g., in a table in memory) , and may select one sequence from the set of possible sequences (e.g., based on a random or pseudo-random process, based on a cell identifier, etc. ) . In other cases, the UE 115 may determine the bit sequence based on a sequence generation function, which may take a UE identifier and a base sequence seed as inputs, and may output a bit sequence for symbol spreading.

FIG. 7 illustrates an example of symbol-level sequence spreading 700 that supports NPRACH capacity enhancement in accordance with various aspects of the present disclosure. Symbol-level sequence spreading 700 may be performed on a RACH preamble 705, such as RACH preambles 705-a and 705-b, which may be examples of single repetitions within NPRACH transmissions. For example, RACH preamble 705-a may be transmitted by a first UE 115, and RACH preamble 705-b may be transmitted by a second UE 115. RACH preambles 705 may include multiple symbol groups 710, each including one or more cyclic prefixes 715 and one or more symbols 720, and spaced in time and frequency, for example, as described with reference to FIG. 2. Symbol-level sequence spreading 700 may utilize a bit sequence 725, which may be referred to as a preamble bit sequence or a multiplexing preamble bit sequence. In some cases, different UEs 115 or different symbol groups may utilize different bit sequences 725 (e.g., a first UE 115 may utilize bit sequence 725-a and a second UE 115 may utilize bit sequence 725-b) . Implementing symbol-level sequence spreading 700 may improve UE 115 multiplexing at a base station 105, but may also increase the decoding complexity at a receiver of the base station 105.

For symbol-level sequence spreading 700, a UE 115 may apply each bit of the bit sequence 725 to one symbol 720 of a RACH preamble 705. A bit sequence 725 may or may not include a same number of bits as a RACH preamble 705 or symbol group 710 includes symbols 720. For example, the bit sequence 725 may include fewer bits than the RACH preamble 705 includes symbols 720. In these cases, the UE 115 may repeat at least a portion of the bit sequence 725 to perform symbol spreading on all of the symbols 720 of the RACH preamble 705. For example, if bit sequence 725-a has a sequence length of four bits, a UE 115 may repeat bit sequence 725-a one and a half times to apply symbol spreading the ten symbols 720 shown in FIG. 7 for RACH preamble 705-a. In one example, the bits of bit sequence 725-a may be defined as [1, -1, -1, 1] . In this case, a UE 115 may apply the bits [1, - 1, -1, 1, 1, -1, -1, 1, 1, -1] to the ten symbols 720 shown for RACH preamble 705-a, for example, using a tensor product 730.

In some examples, different bit sequences 705 for different UEs 115 or symbol groups may be selected based on each other. For example, if bit sequence 725-a is [1, -1, -1, 1], as described above, bit sequence 725-b may include bits to provide orthogonality with bit sequence 725-a. For example, the bits of bit sequence 725-b may be defined as [-1, -1, 1, 1] , such that the product of bit sequence 725-a and bit sequence 725-b is 0. Accordingly, for performing symbol-level sequence spreading 700 on RACH preamble 705-b, a second UE 115 may apply the bits [-1, -1, 1, 1, -1, -1, 1, 1, -1, -1] to the ten symbols 720 shown for RACH preamble 705-b.

In some cases, based on the symbol-level sequence spreading 700, a UE 115 may implement a frame structure where a cyclic prefix 715 is inserted at the start of each symbol group 710 of the RACH preamble 705. Such a frame structure may allow for performing a fast Fourier transform (FFT) operation while applying the bit sequence for symbol-level sequence spreading 700, and in some cases may reduce a cyclic prefix 715 overhead as compared to symbol-level spreading 500 or symbol set-level spreading 600.

Similar to above, in some cases to determine or generate the bit sequence 725, a UE 115 may include an indication of the possible bit sequences 725 (e.g., in a table in memory) , and may select one bit sequence 725 from the set of possible bit sequences 725 (e.g., based on a random or pseudo-random process, based on a cell identifier, based on a UE 115 identifier, etc. ) . In other cases, the UE 115 may determine the bit sequence 725 based on a sequence generation function, which may take a UE identifier and a base sequence seed as inputs, and may output a bit sequence 725 for symbol spreading.

FIG. 8 illustrates an example of a process flow 800 that supports NPRACH capacity enhancement in accordance with various aspects of the present disclosure. The process flow 800 may include base station 105-b and UE 115-b, which may be examples of a base station 105 and a UE 115 as described with reference to FIGs. 1 and 2. The process flow 800 may illustrate techniques for increasing NPRACH capacity using bit sequences (e.g., a scrambling sequence or an OCC) .

At 805, base station 105-b may determine one or more PRACH resource sets for system access, where each of the one or more PRACH resource sets is associated with a frequency hopping pattern. In some cases, base station 105-b may transmit an indication of the one or more PRACH resource sets at 810 in system information. In some cases, UE 115-b may detect and decode the system information.

At 815, UE 115-b may identify, based on a preamble index, a set of PRACH resources for system access using a single-tone RACH preamble, where the set of PRACH resources has a certain frequency hopping pattern. In some cases, UE 115-b may randomly generate the preamble index associated with the set of PRACH resources.

At 820, UE 115-b may determine a preamble bit sequence for the system access, and may apply the determined preamble bit sequence to one or more symbols of the single-tone RACH preamble to obtain a spread single-tone RACH preamble. In some cases, UE 115-b may apply each bit value of the preamble bit sequence to a corresponding symbol of the single-tone RACH preamble. If the bit length of the preamble bit sequence is less than the symbol length of the single-tone RACH preamble, UE 115-b may cyclically apply each bit value of repeated cycles of the preamble bit sequence to corresponding symbols of the single- tone RACH preamble. In other cases, UE 115-b may apply each bit of the preamble bit sequence to a subset of contiguous symbols of the single-tone RACH preamble. In one example, the preamble bit sequence may be an example of an OCC scrambling sequence.

At 825, UE 115-b may transmit the resulting spread single-tone RACH preamble in the identified set of PRACH resources for system access with base station 105-b. Base station 105-b may monitor the determined one or more PRACH resource sets for any signals, and may detect and receive the spread single-tone RACH preamble from UE 115-b.

At 830, base station 105-b may transmit a RACH preamble response to UE 115-b in response to the received spread single-tone RACH preamble. The RACH preamble response may be based on the preamble bit sequence used by UE 115-b for symbol spreading on the single-tone RACH preamble. In some cases, the RACH preamble response may include a preamble index determined based on the preamble bit sequence (and a preamble generator function, for example) . In other cases, the preamble index may be encoded using an RNTI associated with the preamble bit sequence. UE 115-b may receive the RACH preamble response, and may determine that the RACH preamble response is in response to the spread single-tone RACH preamble transmitted at 825 based on an associated RNTI, a preamble bit sequence field in the RACH preamble response, the preamble index indicated in the RACH preamble response, or some combination of these parameters.

FIG. 9 illustrates an example of a process flow 900 that supports NPRACH capacity enhancement in accordance with various aspects of the present disclosure. The process flow 900 may include base station 105-c and UE 115-c, which may be examples of a base station 105 and a UE 115 as described with reference to FIGs. 1 and 2. The process flow 900 may illustrate techniques for increasing NPRACH capacity using frequency offsets (e.g., a random frequency shift or a pattern-specific repetition hopping pattern) .

At 905, base station 105-c may determine one or more PRACH resource sets for system access, where each of the one or more PRACH resource sets is associated with a frequency hopping pattern. In some cases, base station 105-c may transmit an indication of the one or more PRACH resource sets at 910 in system information. In some cases, UE 115-c may detect and decode the system information.

At 915, UE 115-c may identify, based on a preamble index, a set of PRACH resources for system access using a single-tone RACH preamble, where the set of PRACH resources has a certain frequency hopping pattern. In some cases, UE 115-c may randomly generate the preamble index associated with the set of PRACH resources.

At 920, UE 115-c may select a frequency offset value from a set of frequency offset values. In some cases, the set of frequency offset values may be orthogonal frequency shift values for the single-tone RACH preamble. In other cases, UE 115-c may select the frequency offset value based on the frequency hopping pattern and a repetition number of the single-tone RACH preamble.

At 925, UE 115-c may transmit the single-tone RACH preamble for system access in the identified set of PRACH resources according to the frequency hopping pattern and the selected frequency offset value. Base station 105-c may monitor the determined one or more PRACH resource sets for any signals, and may detect and receive the single-tone RACH preamble from UE 115-c in frequency resources according to the frequency hopping pattern and the selected frequency offset value.

At 930, base station 105-c may transmit a RACH preamble response to UE 115-c in response to the received single-tone RACH preamble. The RACH preamble response may be based on the frequency offset value used by UE 115-c for transmitting the single-tone RACH preamble. In some cases, the RACH preamble response may include a preamble index determined based on the frequency offset value (and a preamble generator function, for example) . In other cases, the preamble index may be encoded using an RNTI associated with the frequency offset value. UE 115-c may receive the RACH preamble response, and may determine that the RACH preamble response is in response to the single-tone RACH preamble transmitted at 925 based on an associated RNTI, a frequency offset value field in the RACH preamble response, the preamble index indicated in the RACH preamble response, or some combination of these parameters.

FIG. 10 shows a block diagram 1000 of a wireless device 1005 that supports narrowband physical random access channel capacity enhancement in accordance with aspects of the present disclosure. Wireless device 1005 may be an example of aspects of a UE 115 as described herein. Wireless device 1005 may include receiver 1010, UE NPRACH capacity module 1015, and transmitter 1020. Wireless device 1005 may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses) .

Receiver 1010 may receive information 1025 such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to narrowband physical random access channel capacity enhancement, etc. ) . For example, receiver 1010 may demodulate signals received over monitored time-frequency resources, and may decode the demodulated signals to obtain bits that indicate the information 1025. Receiver 1010 may then pass this information, as information 1030, on to other components of the device. The receiver 1010 may be an example of aspects of the transceiver 1335 described with reference to FIG. 13. The receiver 1010 may utilize a single antenna or a set of antennas.

UE NPRACH capacity module 1015 may be an example of aspects of the UE NPRACH capacity module 1315 described with reference to FIG. 13. UE NPRACH capacity module 1015 and/or at least some of its various sub-components may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions of the UE NPRACH capacity module 1015 and/or at least some of its various sub-components may be executed by a general-purpose processor, a digital signal processor (DSP) , an application-specific integrated circuit (ASIC) , an field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in the present disclosure. The UE NPRACH capacity module 1015 and/or at least some of its various sub-components may be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations by one or more physical devices. In some examples, UE NPRACH capacity module 1015 and/or at least some of its various sub-components may be a separate and distinct component in accordance with various aspects of the present disclosure. In other examples, UE NPRACH capacity module 1015 and/or at least some of its various sub-components may be combined with one or more other hardware components, including but not limited to an I/O component, a transceiver, a network server, another computing device, one or more other components described in the present disclosure, or a combination thereof in accordance with various aspects of the present disclosure.

UE NPRACH capacity module 1015 may identify, based on a preamble index, a set of PRACH resources for system access using a single-tone random access preamble, the set of PRACH resources having a frequency hopping pattern. For example, UE NPRACH capacity module 1015 may identify the resources based on information 1030 received from receiver 1010. In some cases, UE NPRACH capacity module 1015 may additionally determine a preamble bit sequence for the system access, apply the preamble bit sequence to one or more symbols of the single-tone random access preamble to obtain a spread single-tone random access preamble, and transmit the spread single-tone random access preamble for the system access in the set of PRACH resources. In other case, UE NPRACH capacity module 1015 may select a frequency offset value from a set of frequency offset values, and transmit the single-tone random access preamble for the system access in the set of PRACH resources according to the frequency hopping pattern and the selected frequency offset value. For transmitting, UE NPRACH capacity module 1015 may send bits 1035 corresponding to the single-tone random access preamble to transmitter 1020 for transmission.

Transmitter 1020 may transmit signals 1040 generated by other components of the device. For example, transmitter 1020 may encode bits 1035 that indicate the single-tone random access preamble, identify time-frequency resources over which the single-tone random access preamble is to be transmitted, and modulate the transmission over the identified time-frequency resources. In some examples, the transmitter 1020 may be collocated with a receiver 1010 in a transceiver module. For example, the transmitter 1020 may be an example of aspects of the transceiver 1335 described with reference to FIG. 13. The transmitter 1020 may utilize a single antenna or a set of antennas.

FIG. 11 shows a block diagram 1100 of a wireless device 1105 that supports narrowband physical random access channel capacity enhancement in accordance with aspects of the present disclosure. Wireless device 1105 may be an example of aspects of a wireless device 1005 or a UE 115 as described with reference to FIG. 10. Wireless device 1105 may include receiver 1110, UE NPRACH capacity module 1115, and transmitter 1120. Wireless device 1105 may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses) .

Receiver 1110 may receive information 1150 such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to narrowband physical random access channel capacity enhancement, etc. ) . Information 1155 may be passed on to other components of the device. The receiver 1110 may be an example of aspects of the transceiver 1335 described with reference to FIG. 13. The receiver 1110 may utilize a single antenna or a set of antennas.

UE NPRACH capacity module 1115 may be an example of aspects of the UE NPRACH capacity module 1315 described with reference to FIG. 13. UE NPRACH capacity module 1115 may also include PRACH resource identifier 1125, bit sequence component 1130, spreading component 1135, RACH preamble component 1140, and frequency offset component 1145.

PRACH resource identifier 1125 may identify, based on a preamble index, a set of PRACH resources for system access using a single-tone random access preamble, the set of PRACH resources having a frequency hopping pattern. For example, PRACH resource identifier 1125 may identify the PRACH resources based on information 1155 received from receiver 1110. In some cases, each symbol group of the single-tone random access preamble includes a cyclic prefix prior to each symbol of the symbol group. In some cases, each symbol group of the single-tone random access preamble includes a single cyclic prefix. In other cases, the single-tone random access preamble includes a cyclic prefix prior to each contiguous subsets of symbols of the single-tone random access preamble. PRACH resource identifier 1125 may send

information

1160, 1175, and 1180 indicting the set of PRACH resources for system access to other components of the device.

Bit sequence component 1130 may receive the information 1160 from PRACH resource identifier 1125, and may determine a preamble bit sequence for the system access. For example, bit sequence component 1130 may determine the preamble bit sequence based on a table stored in memory, a UE identifier, a base sequence seed, a coverage level grouping, or any combination thereof. In some cases, the preamble bit sequence includes an OCC scrambling sequence. In some cases, a bit length of the preamble bit sequence is equal to a symbol length of the single-tone random access preamble. Bit sequence component 1130 may send the preamble bit sequence 1165 to spreading component 1135.

Spreading component 1135 may receive preamble bit sequence 1165 from bit sequence component 1130, and may apply the preamble bit sequence to one or more symbols of the single-tone random access preamble to obtain a spread single-tone random access preamble. In some cases, applying the preamble bit sequence to the one or more symbols of the single-tone random access preamble includes applying each bit value of the preamble bit sequence to a corresponding symbol of the single-tone random access preamble. In some cases, a bit length of the preamble bit sequence is less than a symbol length of the single-tone random access preamble, and applying each bit value of the preamble bit sequence to the corresponding symbol of the set of repetitions of the single-tone random access preamble includes cyclically applying each bit value of a set of cycles of the preamble bit sequence to corresponding symbols of the single-tone random access preamble. In other cases, applying the preamble bit sequence to the one or more symbols of the single-tone random access preamble includes applying each bit value of the preamble bit sequence to a contiguous subset of symbols of the single-tone random access preamble. Spreading component 1135 may send bits 1170 indicating the resulting spread single-tone random access preamble to RACH preamble component 1140.

RACH preamble component 1140 may receive the bits 1170 indicating the spread single-tone random access preamble and the information 1175 indicting the set of PRACH resources for system access, and may transmit the spread single-tone random access preamble for the system access in the set of PRACH resources.

Frequency offset component 1145 may receive the information 1180 indicting the set of PRACH resources, and may select a frequency offset value from a set of frequency offset values. In some cases, selecting the frequency offset value includes selecting the frequency offset value from a set of orthogonal frequency shift values for the single-tone random access preamble. In some cases, a first type of UEs are associated with a first tone spacing for transmission of single-tone random access preambles, where the set of frequency offset values correspond to frequency shifts interstitial to the first tone spacing. In some cases, the set of frequency offset values includes a zero offset value. Frequency offset component 1145 may send bits 1185 indicating the selected frequency offset value to RACH preamble component 1140.

RACH preamble component 1140 may additionally or alternatively receive the bits 1185 indicating the selected frequency offset, and may receive the information 1175 indicting the set of PRACH resources for system access, and RACH preamble component 1140 may transmit the single-tone random access preamble for the system access in the set of PRACH resources according to the frequency hopping pattern and the selected frequency offset value. For transmitting, RACH preamble component 1140 may send bits 1190 corresponding to the single-tone random access preamble to transmitter 1120 for transmission.

Transmitter 1120 may transmit signals 1195 generated by other components of the device. For example, transmitter 1120 may encode bits 1190 that indicate the single-tone random access preamble, identify time-frequency resources over which the single-tone random access preamble is to be transmitted, and modulate the transmission over the identified time-frequency resources. In some examples, the transmitter 1120 may be collocated with a receiver 1110 in a transceiver module. For example, the transmitter 1120 may be an example of aspects of the transceiver 1335 described with reference to FIG. 13. The transmitter 1120 may utilize a single antenna or a set of antennas.

FIG. 12 shows a block diagram 1200 of a UE NPRACH capacity module 1215 that supports narrowband physical random access channel capacity enhancement in accordance with aspects of the present disclosure. The UE NPRACH capacity module 1215 may be an example of aspects of a UE NPRACH capacity module 1015, a UE NPRACH capacity module 1115, or a UE NPRACH capacity module 1315 described with reference to FIGs. 10, 11, and 13. The UE NPRACH capacity module 1215 may include PRACH resource identifier 1220, bit sequence component 1225, spreading component 1230, RACH preamble component 1235, frequency offset component 1240, preamble index component 1245, RACH response component 1250, frequency set identifier 1255, and repetition component 1260. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses) .

PRACH resource identifier 1220 may identify, based on a preamble index, a set of PRACH resources for system access using a single-tone random access preamble, the set of PRACH resources having a frequency hopping pattern. In some cases, each symbol group of the single-tone random access preamble includes a cyclic prefix prior to each symbol of the symbol group. In some cases, each symbol group of the single-tone random access preamble includes a single cyclic prefix. In some cases, the single-tone random access preamble includes a cyclic prefix prior to each contiguous subsets of symbols of the single-tone random access preamble.

Bit sequence component 1225 may determine a preamble bit sequence for the system access. In some examples, bit sequence component 1225 may determine the preamble bit sequence based on a table stored in memory, a UE identifier, a base sequence seed, a coverage level grouping, or any combination thereof. In some cases, the preamble bit sequence includes an OCC scrambling sequence. In some cases, a bit length of the preamble bit sequence is equal to a symbol length of the single-tone random access preamble.

Spreading component 1230 may apply the preamble bit sequence to one or more symbols of the single-tone random access preamble to obtain a spread single-tone random access preamble. In some cases, applying the preamble bit sequence to the one or more symbols of the single-tone random access preamble includes applying each bit value of the preamble bit sequence to a corresponding symbol of the single-tone random access preamble. In some cases, a bit length of the preamble bit sequence is less than a symbol length of the single-tone random access preamble, where applying each bit value of the preamble bit sequence to the corresponding symbol of the set of repetitions of the single-tone random access preamble may include cyclically applying each bit value of a set of cycles of the preamble bit sequence to corresponding symbols of the single-tone random access preamble. In other cases, applying the preamble bit sequence to the one or more symbols of the single-tone random access preamble includes applying each bit value of the preamble bit sequence to a contiguous subset of symbols of the single-tone random access preamble. RACH preamble component 1235 may transmit the spread single-tone random access preamble for the system access in the set of PRACH resources.

Frequency offset component 1240 may select a frequency offset value from a set of frequency offset values. In some cases, selecting the frequency offset value includes selecting the frequency offset value from a set of orthogonal frequency shift values for the single-tone random access preamble. In some cases, a first type of UEs are associated with a first tone spacing for transmission of single-tone random access preambles, where the set of frequency offset values correspond to frequency shifts interstitial to the first tone spacing. In some cases, the set of frequency offset values includes a zero offset value. RACH preamble component 1235 may transmit the single-tone random access preamble for the system access in the set of PRACH resources according to the frequency hopping pattern and the selected frequency offset value.

Preamble index component 1245 may randomly generate the preamble index associated with the spread single-tone random access preamble. In some cases, preamble index component 1245 may determine resources for transmitting the spread single-tone random access preamble, the preamble bit sequence, or both based on the preamble index and a preamble generator function. In some cases, preamble index component 1245 may randomly generate the preamble index associated with the single-tone random access preamble, where selecting the frequency offset value is based on the preamble index and a preamble generator function.

RACH response component 1250 may identify a random access preamble response associated with the spread single-tone random access preamble or the single-tone random access preamble based on an RNTI corresponding to the preamble bit sequence, the selected frequency offset value, or on a field of the random access preamble response corresponding to the preamble bit sequence or the selected frequency offset value.

Frequency set identifier 1255 may receive, from a base station, an indication of the set of orthogonal frequency shift values. Repetition component 1260 may select the frequency offset value based on the frequency hopping pattern and a repetition number of the single-tone random access preamble.

FIG. 13 shows a diagram of a system 1300 including a device 1305 that supports narrowband physical random access channel capacity enhancement in accordance with aspects of the present disclosure. Device 1305 may be an example of or include the components of wireless device 1005, wireless device 1105, or a UE 115 as described above, e.g., with reference to FIGs. 10 and 11. Device 1305 may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including UE NPRACH capacity module 1315, processor 1320, memory 1325, software 1330, transceiver 1335, antenna 1340, and I/O controller 1345. These components may be in electronic communication via one or more buses (e.g., bus 1310) . Device 1305 may communicate wirelessly with one or more base stations 105.

Processor 1320 may include an intelligent hardware device, (e.g., a general-purpose processor, a DSP, a central processing unit (CPU) , a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof) . In some cases, processor 1320 may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into processor 1320. Processor 1320 may be configured to execute computer-readable instructions stored in a memory to perform various functions (e.g., functions or tasks supporting narrowband physical random access channel capacity enhancement) .

Memory 1325 may include random access memory (RAM) and read only memory (ROM) . The memory 1325 may store computer-readable, computer-executable software 1330 including instructions that, when executed, cause the processor to perform various functions described herein. In some cases, the memory 1325 may contain, among other things, a basic input/output system (BIOS) which may control basic hardware or software operation such as the interaction with peripheral components or devices.

Software 1330 may include code to implement aspects of the present disclosure, including code to support narrowband physical random access channel capacity enhancement. Software 1330 may be stored in a non-transitory computer-readable medium such as system memory or other memory. In some cases, the software 1330 may not be directly executable by the processor but may cause a computer (e.g., when compiled and executed) to perform functions described herein.

Transceiver 1335 may communicate bi-directionally, via one or more antennas, wired, or wireless links as described above. For example, the transceiver 1335 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver 1335 may also include a modem to modulate the packets and provide the modulated packets to the antennas for transmission, and to demodulate packets received from the antennas.

In some cases, the wireless device may include a single antenna 1340. However, in some cases the device may have more than one antenna 1340, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

I/O controller 1345 may manage input and output signals for device 1305. I/O controller 1345 may also manage peripherals not integrated into device 1305. In some cases, I/O controller 1345 may represent a physical connection or port to an external peripheral. In some cases, I/O controller 1345 may utilize an operating system such as

or another known operating system. In other cases, I/O controller 1345 may represent or interact with a modem, a keyboard, a mouse, a touchscreen, or a similar device. In some cases, I/O controller 1345 may be implemented as part of a processor. In some cases, a user may interact with device 1305 via I/O controller 1345 or via hardware components controlled by I/O controller 1345.

FIG. 14 shows a block diagram 1400 of a wireless device 1405 that supports narrowband physical random access channel capacity enhancement in accordance with aspects of the present disclosure. Wireless device 1405 may be an example of aspects of a base station 105 as described herein. Wireless device 1405 may include receiver 1410, base station NPRACH capacity module 1415, and transmitter 1420. Wireless device 1405 may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses) .

Receiver 1410 may receive information 1425 such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to narrowband physical random access channel capacity enhancement, etc. ) . Information 1430 may be passed on to other components of the device. The receiver 1410 may be an example of aspects of the transceiver 1735 described with reference to FIG. 17. The receiver 1410 may utilize a single antenna or a set of antennas.

Base station NPRACH capacity module 1415 may be an example of aspects of the base station NPRACH capacity module 1715 described with reference to FIG. 17. Base station NPRACH capacity module 1415 and/or at least some of its various sub-components may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions of the base station NPRACH capacity module 1415 and/or at least some of its various sub-components may be executed by a general-purpose processor, a DSP, an ASIC, an FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in the present disclosure. The base station NPRACH capacity module 1415 and/or at least some of its various sub-components may be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations by one or more physical devices. In some examples, base station NPRACH capacity module 1415 and/or at least some of its various sub-components may be a separate and distinct component in accordance with various aspects of the present disclosure. In other examples, base station NPRACH capacity module 1415 and/or at least some of its various sub-components may be combined with one or more other hardware components, including but not limited to an I/O component, a transceiver, a network server, another computing device, one or more other components described in the present disclosure, or a combination thereof in accordance with various aspects of the present disclosure.

Base station NPRACH capacity module 1415 may determine a set of PRACH resource sets for system access, each of the set of PRACH resource sets associated with a frequency hopping pattern. In some cases, base station NPRACH capacity module 1415 may receive (e.g., received as information 1430 from receiver 1410) a spread single-tone random access preamble over a PRACH resource set of the set of PRACH resource sets, the spread single-tone random access preamble spread with one of a set of preamble bit sequences, and may transmit a random access preamble response in response to the received spread single-tone random access preamble, where the random access preamble response is based on the one of the set of preamble bit sequences used for the spread single-tone random access preamble. In other cases, the base station NPRACH capacity module 1415 may receive (e.g., received as information 1430 from receiver 1410) a single-tone random access preamble over a PRACH resource set of the set of PRACH resource sets, the single-tone random access preamble transmitted using the frequency hopping pattern and one of a set of frequency offset values, and may transmit a random access preamble response in response to the received single-tone random access preamble, where the random access preamble response is based on the one of the set of frequency offset values used for transmission of the single-tone random access preamble. For transmitting, base station NPRACH capacity module 1415 may send bits 1435 corresponding to a random access preamble response to transmitter 1420 for transmission.

Transmitter 1420 may transmit signals 1440 generated by other components of the device. In some examples, the transmitter 1420 may be collocated with a receiver 1410 in a transceiver module. For example, the transmitter 1420 may be an example of aspects of the transceiver 1735 described with reference to FIG. 17. The transmitter 1420 may utilize a single antenna or a set of antennas.

FIG. 15 shows a block diagram 1500 of a wireless device 1505 that supports narrowband physical random access channel capacity enhancement in accordance with aspects of the present disclosure. Wireless device 1505 may be an example of aspects of a wireless device 1405 or a base station 105 as described with reference to FIG. 14. Wireless device 1505 may include receiver 1510, base station NPRACH capacity module 1515, and transmitter 1520. Wireless device 1505 may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses) .

Receiver 1510 may receive information 1545 such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to narrowband physical random access channel capacity enhancement, etc. ) . For example, receiver 1510 may monitor time-frequency resources for signals, for example, based on a set of PRACH resource sets indicated to receiver 1510 in information 1540. Information 1550, based on received, demodulated, and decoded signals, may be passed on to other components of the device. The receiver 1510 may be an example of aspects of the transceiver 1735 described with reference to FIG. 17. The receiver 1510 may utilize a single antenna or a set of antennas.

Base station NPRACH capacity module 1515 may be an example of aspects of the base station NPRACH capacity module 1715 described with reference to FIG. 17. Base station NPRACH capacity module 1515 may also include PRACH resource component 1525, RACH preamble component 1530, and RACH response component 1535.

PRACH resource component 1525 may determine a set of PRACH resource sets for system access, each of the set of PRACH resource sets associated with a frequency hopping pattern. PRACH resource component 1525 may send information 1540 to receiver 1510 indicating the set of PRACH resource sets for system access.

RACH preamble component 1530 may receive a spread single-tone random access preamble over a PRACH resource set of the set of PRACH resource sets, the spread single-tone random access preamble spread with one of a set of preamble bit sequences. In other cases, RACH preamble component 1530 may receive a single-tone random access preamble over a PRACH resource set of the set of PRACH resource sets, the single-tone random access preamble transmitted using the frequency hopping pattern and one of a set of frequency offset values. In some cases, the set of frequency offset values correspond to orthogonal frequency shifts of the single-tone random access preamble. RACH preamble component 1530 may receive these preambles in information 1550 from receiver 1510, and may send information 1555 indicating these single-tone random access preambles to RACH response component 1535.

RACH response component 1535 may receive information 1555 indicating a single-tone random access preamble. Based on this information 1555, in some cases, RACH response component 1535 may transmit a random access preamble response in response to the received spread single-tone random access preamble, where the random access preamble response is based on the one of the set of preamble bit sequences used for the spread single-tone random access preamble. In other cases, based on this information 1555, RACH response component 1535 may transmit a random access preamble response in response to the received single-tone random access preamble, where the random access preamble response is based on the one of the set of frequency offset values used for transmission of the single-tone random access preamble. In some cases, the random access preamble response includes a preamble index to be decoded using an RNTI, where the RNTI is based on the one of the set of preamble bit sequences or on the one of the set of frequency offset values. For transmitting, RACH response component 1535 may send bits 1560 corresponding to the random access preamble response to transmitter 1520 for transmission.

Transmitter 1520 may transmit signals 1565 generated by other components of the device. In some examples, the transmitter 1520 may be collocated with a receiver 1510 in a transceiver module. For example, the transmitter 1520 may be an example of aspects of the transceiver 1735 described with reference to FIG. 17. The transmitter 1520 may utilize a single antenna or a set of antennas.

FIG. 16 shows a block diagram 1600 of a base station NPRACH capacity module 1615 that supports narrowband physical random access channel capacity enhancement in accordance with aspects of the present disclosure. The base station NPRACH capacity module 1615 may be an example of aspects of a base station NPRACH capacity module 1715 described with reference to FIGs. 14, 15, and 17. The base station NPRACH capacity module 1615 may include PRACH resource component 1620, RACH preamble component 1625, RACH response component 1630, preamble index component 1635, and system information component 1640. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses) .

PRACH resource component 1620 may determine a set of PRACH resource sets for system access, each of the set of PRACH resource sets associated with a frequency hopping pattern.

In some cases, RACH preamble component 1625 may receive a spread single-tone random access preamble over a PRACH resource set of the set of PRACH resource sets, the spread single-tone random access preamble spread with one of a set of preamble bit sequences. In other cases, RACH preamble component 1625 may receive a single-tone random access preamble over a PRACH resource set of the set of PRACH resource sets, the single-tone random access preamble transmitted using the frequency hopping pattern and one of a set of frequency offset values. In some cases, the set of frequency offset values correspond to orthogonal frequency shifts of the single-tone random access preamble.

In some cases, RACH response component 1630 may transmit a random access preamble response in response to the received spread single-tone random access preamble, where the random access preamble response is based on the one of the set of preamble bit sequences used for the spread single-tone random access preamble. In other cases, RACH response component 1630 may transmit a random access preamble response in response to the received single-tone random access preamble, where the random access preamble response is based on the one of the set of frequency offset values used for transmission of the single-tone random access preamble. In some cases, the random access preamble response includes a preamble index to be decoded using an RNTI, where the RNTI is based on the one of the set of preamble bit sequences. In other cases, the random access preamble response includes a preamble index to be decoded using an RNTI, where the RNTI is based on the one of the set of frequency offset values.

In some cases, preamble index component 1635 may determine a preamble index based on a preamble generator function, the one of the set of preamble bit sequences, and resources used for receiving the spread single-tone random access preamble. In other cases, preamble index component 1635 may determine a preamble index based on a preamble generator function, the one of the set of frequency offset values, and resources used for receiving the single-tone random access preamble.

System information component 1640 may transmit system information including an indication of the set of preamble bit sequences, transmit system information including an indication of one or more group indexes associated with different coverage levels for a cell, where the one of the set of preamble bit sequences is based on a group index of the one or more group indexes, or transmit system information including an indication of the set of frequency offset values.

FIG. 17 shows a diagram of a system 1700 including a device 1705 that supports narrowband physical random access channel capacity enhancement in accordance with aspects of the present disclosure. Device 1705 may be an example of or include the components of base station 105 as described above, e.g., with reference to FIG. 1. Device 1705 may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including base station NPRACH capacity module 1715, processor 1720, memory 1725, software 1730, transceiver 1735, antenna 1740, network communications manager 1745, and inter-station communications manager 1750. These components may be in electronic communication via one or more buses (e.g., bus 1710) . Device 1705 may communicate wirelessly with one or more UEs 115.

Processor 1720 may include an intelligent hardware device, (e.g., a general-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof) . In some cases, processor 1720 may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into processor 1720. Processor 1720 may be configured to execute computer-readable instructions stored in a memory to perform various functions (e.g., functions or tasks supporting narrowband physical random access channel capacity enhancement) .

Memory 1725 may include RAM and ROM. The memory 1725 may store computer-readable, computer-executable software 1730 including instructions that, when executed, cause the processor to perform various functions described herein. In some cases, the memory 1725 may contain, among other things, a BIOS which may control basic hardware or software operation such as the interaction with peripheral components or devices.

Software 1730 may include code to implement aspects of the present disclosure, including code to support narrowband physical random access channel capacity enhancement. Software 1730 may be stored in a non-transitory computer-readable medium such as system memory or other memory. In some cases, the software 1730 may not be directly executable by the processor but may cause a computer (e.g., when compiled and executed) to perform functions described herein.

Transceiver 1735 may communicate bi-directionally, via one or more antennas, wired, or wireless links as described above. For example, the transceiver 1735 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver 1735 may also include a modem to modulate the packets and provide the modulated packets to the antennas for transmission, and to demodulate packets received from the antennas.

In some cases, the wireless device may include a single antenna 1740. However, in some cases the device may have more than one antenna 1740, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

Network communications manager 1745 may manage communications with the core network (e.g., via one or more wired backhaul links) . For example, the network communications manager 1745 may manage the transfer of data communications for client devices, such as one or more UEs 115.

Inter-station communications manager 1750 may manage communications with other base station 105, and may include a controller or scheduler for controlling communications with UEs 115 in cooperation with other base stations 105. For example, the inter-station communications manager 1750 may coordinate scheduling for transmissions to UEs 115 for various interference mitigation techniques such as beamforming or joint transmission. In some examples, inter-station communications manager 1750 may provide an X2 interface within an Long Term Evolution (LTE) /LTE-Awireless communication network technology to provide communication between base stations 105.

FIG. 18 shows a flowchart illustrating a method 1800 for narrowband physical random access channel capacity enhancement in accordance with aspects of the present disclosure. The operations of method 1800 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 1800 may be performed by a UE NPRACH capacity module as described with reference to FIGs. 10 through 13. In some examples, a UE 115 may execute a set of codes to control the functional elements of the device to perform the functions described below. Additionally or alternatively, the UE 115 may perform aspects of the functions described below using special-purpose hardware.

At 1805 the UE 115 may identify, based at least in part on a preamble index, a set of PRACH resources for system access using a single-tone random access preamble, the set of PRACH resources having a frequency hopping pattern. For example, the UE 115 may identify time-frequency resources over which an SIB or DCI signal indicating the preamble index may be transmitted from a base station 105. The UE 115 may demodulate the transmission over those time-frequency resources and decode the demodulated transmission to obtain bits that indicate the preamble index. In other cases, the UE 115 may randomly or pseudo-randomly select the preamble index from a list of preamble indexes stored in memory. Based on information stored in memory (e.g., a list of preamble indexes and corresponding PRACH resources) , the UE 115 may determine the set of PRACH resources for system access. This set of PRACH resources may correspond to time-frequency resources for transmitting a signal indicating the single-tone random access preamble. The operations of 1805 may be performed according to the methods described herein. In certain examples, aspects of the operations of 1805 may be performed by a PRACH resource identifier as described with reference to FIGs. 10 through 13.

At 1810 the UE 115 may determine a preamble bit sequence for the system access. For example, the UE 115 may determine the preamble bit sequence based on information bits of the SIB or DCI, as described above. In other cases, the UE 115 may generate the preamble bit sequence using a random process, such as a random number generation technique. In other cases, the UE 115 may select the preamble bit sequence from a list of possible preamble bit sequences stored in memory, where the selection may be based on an identifier of the UE 115, a base sequence seed, a received coverage level index (e.g., received in the SIB or DCI as described above) , or some combination of these parameters. The operations of 1810 may be performed according to the methods described herein. In certain examples, aspects of the operations of 1810 may be performed by a bit sequence component as described with reference to FIGs. 10 through 13.

At 1815 the UE 115 may apply the preamble bit sequence to one or more symbols of the single-tone random access preamble to obtain a spread single-tone random access preamble. For example, the UE 115 may modify bits indicating the single-tone random access preamble by combining the bits with the preamble bit sequence. In some cases, combining the bits may involve performing tensor multiplication, exclusive or (XOR) functions, or similar techniques for determining an output bit based on two input bits. The bits output from the combination of the single-tone random access preamble bits and the preamble bit sequence may indicate the spread single-tone random access preamble. The operations of 1815 may be performed according to the methods described herein. In certain examples, aspects of the operations of 1815 may be performed by a spreading component as described with reference to FIGs. 10 through 13.

At 1820 the UE 115 may transmit the spread single-tone random access preamble for the system access in the set of PRACH resources. For example, the UE 115 may encode the bits indicating the spread single-tone random access preamble. The UE 115 may then modulate the transmission using these encoded bits over the time-frequency resources corresponding to the set of PRACH resources. This transmission may initiate a system access procedure between the UE 115 and a base station 105. The operations of 1820 may be performed according to the methods described herein. In certain examples, aspects of the operations of 1820 may be performed by a RACH preamble component as described with reference to FIGs. 10 through 13.

FIG. 19 shows a flowchart illustrating a method 1900 for narrowband physical random access channel capacity enhancement in accordance with aspects of the present disclosure. The operations of method 1900 may be implemented by a base station 105 or its components as described herein. For example, the operations of method 1900 may be performed by a base station NPRACH capacity module as described with reference to FIGs. 14 through 17. In some examples, a base station 105 may execute a set of codes to control the functional elements of the device to perform the functions described below. Additionally or alternatively, the base station 105 may perform aspects of the functions described below using special-purpose hardware.

At 1905 the base station 105 may determine a plurality of PRACH resource sets for system access, each of the plurality of PRACH resource sets associated with a frequency hopping pattern. For example, in some cases, the base station 105 may determine the plurality of PRACH resource sets based on a configuration stored in memory of the base station 105. In other cases, the base station 105 may determine the plurality of PRACH resource sets based on measuring a channel quality of the PRACH (e.g., the base station 105 may monitor the time-frequency resources corresponding to the PRACH, demodulate received signals over these time-frequency resources, and decode the demodulated signals to obtain bits indicating information about the channel quality) and selecting one or more PRACH resources or configurations based on the determined channel quality. The operations of 1905 may be performed according to the methods described herein. In certain examples, aspects of the operations of 1905 may be performed by a PRACH resource component as described with reference to FIGs. 14 through 17.

At 1910 the base station 105 may receive a spread single-tone random access preamble over a PRACH resource set of the plurality of PRACH resource sets, the spread single-tone random access preamble spread with one of a plurality of preamble bit sequences. For example, the base station 105 may identify time-frequency resources over which the random access preamble message may be transmitted from a UE 115. The time-frequency resources may correspond (e.g., may be part of a resource set, or may be a frequency-shifted version of a resource set) to the plurality of PRACH resource sets determined by the base station 105. The base station 105 may demodulate the transmission over those time-frequency resources and decode the demodulated transmission to obtain bits that indicate the spread single-tone random access preamble. In some cases, demodulating and decoding the bits may be based on the one of a plurality of preamble bit sequences associated with the transmission. The operations of 1910 may be performed according to the methods described herein. In certain examples, aspects of the operations of 1910 may be performed by a RACH preamble component as described with reference to FIGs. 14 through 17.

At 1915 the base station 105 may transmit a random access preamble response in response to the received spread single-tone random access preamble, wherein the random access preamble response is based at least in part on the one of the plurality of preamble bit sequences used for the spread single-tone random access preamble. For example, the base station 105 may encode bits that indicate the random access preamble response, identify time-frequency resources over which the random access preamble response is to be transmitted, and modulate the transmission over the identified time-frequency resources. The operations of 1915 may be performed according to the methods described herein. In certain examples, aspects of the operations of 1915 may be performed by a RACH response component as described with reference to FIGs. 14 through 17.

FIG. 20 shows a flowchart illustrating a method 2000 for narrowband physical random access channel capacity enhancement in accordance with aspects of the present disclosure. The operations of method 2000 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 2000 may be performed by a UE NPRACH capacity module as described with reference to FIGs. 10 through 13. In some examples, a UE 115 may execute a set of codes to control the functional elements of the device to perform the functions described below. Additionally or alternatively, the UE 115 may perform aspects of the functions described below using special-purpose hardware.

At 2005 the UE 115 may identify, based at least in part on a preamble index, a set of PRACH resources for system access using a single-tone random access preamble, the set of PRACH resources having a frequency hopping pattern. For example, the UE 115 may identify time-frequency resources over which an SIB or DCI signal indicating the preamble index may be transmitted from a base station 105. The UE 115 may demodulate the transmission over those time-frequency resources and decode the demodulated transmission to obtain bits that indicate the preamble index. In other cases, the UE 115 may randomly or pseudo-randomly select the preamble index from a list of preamble indexes stored in memory. Based on information stored in memory (e.g., a list of preamble indexes and corresponding PRACH resources) , the UE 115 may determine the set of PRACH resources for system access. This set of PRACH resources may correspond to time-frequency resources for transmitting a signal indicating the single-tone random access preamble. The operations of 2005 may be performed according to the methods described herein. In certain examples, aspects of the operations of 2005 may be performed by a PRACH resource identifier as described with reference to FIGs. 10 through 13.

At 2010 the UE 115 may select a frequency offset value from a set of frequency offset values. For example, the UE 115 may determine the set of frequency offset values based on decoded information bits of the SIB or DCI, as described above. In other cases, the UE 115 may contain indications of the set of frequency offset values in memory. The UE 115 may select a frequency offset from the set using a random process, such as a random number generation technique. In other cases, the UE 115 may select the frequency offset value based on information received from the base station 105, or may select the frequency offset value based on some selection function dependent on an identifier of the UE 115, an identifier of the base station 105, a repetition index for the single-tone random access preamble, the frequency hopping pattern for the identified set of PRACH resources, or some combination of these inputs. The operations of 2010 may be performed according to the methods described herein. In certain examples, aspects of the operations of 2010 may be performed by a frequency offset component as described with reference to FIGs. 10 through 13.

At 2015 the UE 115 may transmit the single-tone random access preamble for the system access in the set of PRACH resources according to the frequency hopping pattern and the selected frequency offset value. For example, the UE 115 may encode bits indicating the single-tone random access preamble. The UE 115 may then modulate the transmission using these encoded bits over time-frequency resources, where the time-frequency resources may correspond to a frequency-shifted version of time-frequency resources associated with the set of PRACH resources. This transmission may initiate a system access procedure between the UE 115 and a base station 105. The operations of 2015 may be performed according to the methods described herein. In certain examples, aspects of the operations of 2015 may be performed by a RACH preamble component as described with reference to FIGs. 10 through 13.

FIG. 21 shows a flowchart illustrating a method 2100 for narrowband physical random access channel capacity enhancement in accordance with aspects of the present disclosure. The operations of method 2100 may be implemented by a base station 105 or its components as described herein. For example, the operations of method 2100 may be performed by a base station NPRACH capacity module as described with reference to FIGs. 14 through 17. In some examples, a base station 105 may execute a set of codes to control the functional elements of the device to perform the functions described below. Additionally or alternatively, the base station 105 may perform aspects of the functions described below using special-purpose hardware.

At 2105 the base station 105 may determine a plurality of PRACH resource sets for system access, each of the plurality of PRACH resource sets associated with a frequency hopping pattern. For example, in some cases, the base station 105 may determine the plurality of PRACH resource sets based on a configuration stored in memory of the base station 105. In other cases, the base station 105 may determine the plurality of PRACH resource sets based on measuring a channel quality of the PRACH (e.g., the base station 105 may monitor the time-frequency resources corresponding to the PRACH, demodulate received signals over these time-frequency resources, and decode the demodulated signals to obtain bits indicating information about the channel quality) and selecting one or more PRACH resources or configurations based on the determined channel quality. The operations of 2105 may be performed according to the methods described herein. In certain examples, aspects of the operations of 2105 may be performed by a PRACH resource component as described with reference to FIGs. 14 through 17.

At 2110 the base station 105 may receive a single-tone random access preamble over a PRACH resource set of the plurality of PRACH resource sets, the single-tone random access preamble transmitted using the frequency hopping pattern and one of a plurality of frequency offset values. For example, the base station 105 may identify time-frequency resources over which the random access preamble message may be transmitted from a UE 115. The time-frequency resources may correspond (e.g., may be part of a resource set, or may be a frequency-shifted version of a resource set) to the plurality of PRACH resource sets determined by the base station 105. The base station 105 may demodulate the transmission over those time-frequency resources and decode the demodulated transmission to obtain bits that indicate the single-tone random access preamble. The operations of 2110 may be performed according to the methods described herein. In certain examples, aspects of the operations of 2110 may be performed by a RACH preamble component as described with reference to FIGs. 14 through 17.

At 2115 the base station 105 may transmit a random access preamble response in response to the received single-tone random access preamble, wherein the random access preamble response is based at least in part on the one of the plurality of frequency offset values used for transmission of the single-tone random access preamble. For example, the base station 105 may encode bits that indicate the random access preamble response, identify time-frequency resources over which the random access preamble response is to be transmitted, and modulate the transmission over the identified time-frequency resources. The operations of 2115 may be performed according to the methods described herein. In certain examples, aspects of the operations of 2115 may be performed by a RACH response component as described with reference to FIGs. 14 through 17.

It should be noted that the methods described above describe possible implementations, and that the operations and the steps may be rearranged or otherwise modified and that other implementations are possible. Further, aspects from two or more of the methods may be combined.

Techniques described herein may be used for various wireless communications systems such as code division multiple access (CDMA) , time division multiple access (TDMA) , frequency division multiple access (FDMA) , orthogonal frequency division multiple access (OFDMA) , single carrier frequency division multiple access (SC-FDMA) , and other systems. A CDMA system may implement a radio technology such as CDMA2000, Universal Terrestrial Radio Access (UTRA) , etc. CDMA2000 covers IS-2000, IS-95, and IS-856 standards. IS-2000 Releases may be commonly referred to as CDMA2000 1X, 1X, etc. IS-856 (TIA-856) is commonly referred to as CDMA2000 1xEV-DO, High Rate Packet Data (HRPD) , etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. A TDMA system may implement a radio technology such as Global System for Mobile Communications (GSM) .

An OFDMA system may implement a radio technology such as Ultra Mobile Broadband (UMB) , Evolved UTRA (E-UTRA) , Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi) , IEEE 802.16 (WiMAX) , IEEE 802.20, Flash-OFDM, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunications System (UMTS) . LTE and LTE-Aare releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, NR, and GSM are described in documents from the organization named “3rd Generation Partnership Project” (3GPP) . CDMA2000 and UMB are described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2) . The techniques described herein may be used for the systems and radio technologies mentioned above as well as other systems and radio technologies. While aspects of an LTE or an NR system may be described for purposes of example, and LTE or NR terminology may be used in much of the description, the techniques described herein are applicable beyond LTE or NR applications.

A macro cell generally covers a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs 115 with service subscriptions with the network provider. A small cell may be associated with a lower-powered base station 105, as compared with a macro cell, and a small cell may operate in the same or different (e.g., licensed, unlicensed, etc. ) frequency bands as macro cells. Small cells may include pico cells, femto cells, and micro cells according to various examples. A pico cell, for example, may cover a small geographic area and may allow unrestricted access by UEs 115 with service subscriptions with the network provider. A femto cell may also cover a small geographic area (e.g., a home) and may provide restricted access by UEs 115 having an association with the femto cell (e.g., UEs 115 in a closed subscriber group (CSG) , UEs 115 for users in the home, and the like) . An eNB for a macro cell may be referred to as a macro eNB. An eNB for a small cell may be referred to as a small cell eNB, a pico eNB, a femto eNB, or a home eNB. An eNB may support one or multiple (e.g., two, three, four, and the like) cells, and may also support communications using one or multiple component carriers.

The wireless communications system 100 or systems described herein may support synchronous or asynchronous operation. For synchronous operation, the base stations 105 may have similar frame timing, and transmissions from different base stations 105 may be approximately aligned in time. For asynchronous operation, the base stations 105 may have different frame timing, and transmissions from different base stations 105 may not be aligned in time. The techniques described herein may be used for either synchronous or asynchronous operations.

Information and signals described herein may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

The various illustrative blocks and modules described in connection with the disclosure herein may be implemented or performed with a general-purpose processor, a digital signal processor (DSP) , an application-specific integrated circuit (ASIC) , a field-programmable gate array (FPGA) or other programmable logic device (PLD) , discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration) .

The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Other examples and implementations are within the scope of the disclosure and appended claims. For example, due to the nature of software, functions described above can be implemented using software executed by a processor, hardware, firmware, hardwiring, or combinations of any of these. Features implementing functions may also be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations.

Computer-readable media includes both non-transitory computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A non-transitory storage medium may be any available medium that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, non-transitory computer-readable media may comprise random-access memory (RAM) , read-only memory (ROM) , electrically erasable programmable read only memory (EEPROM) , flash memory, compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special- purpose computer, or a general-purpose or special-purpose processor. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL) , or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, include CD, laser disc, optical disc, digital versatile disc (DVD) , floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above are also included within the scope of computer-readable media.

As used herein, including in the claims, “or” as used in a list of items (e.g., a list of items prefaced by a phrase such as “at least one of” or “one or more of” ) indicates an inclusive list such that, for example, a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A and B and C) . Also, as used herein, the phrase “based on” shall not be construed as a reference to a closed set of conditions. For example, an exemplary step that is described as “based on condition A” may be based on both a condition A and a condition B without departing from the scope of the present disclosure. In other words, as used herein, the phrase “based on” shall be construed in the same manner as the phrase “based at least in part on. ”

In the appended figures, similar components or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If just the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label, or other subsequent reference label.

The description set forth herein, in connection with the appended drawings, describes example configurations and does not represent all the examples that may be implemented or that are within the scope of the claims. The term “exemplary” used herein means “serving as an example, instance, or illustration, ” and not “preferred” or “advantageous over other examples. ” The detailed description includes specific details for the purpose of providing an understanding of the described techniques. These techniques, however, may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described examples.

The description herein is provided to enable a person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the scope of the disclosure. Thus, the disclosure is not limited to the examples and designs described herein, but is to be accorded the broadest scope consistent with the principles and novel features disclosed herein.

Claims

A method for wireless communication, comprising:

identifying, based at least in part on a preamble index, a set of physical random access channel (PRACH) resources for system access using a single-tone random access preamble, the set of PRACH resources having a frequency hopping pattern；

determining a preamble bit sequence for the system access；

applying the preamble bit sequence to one or more symbols of the single-tone random access preamble to obtain a spread single-tone random access preamble； and

transmitting the spread single-tone random access preamble for the system access in the set of PRACH resources.
The method of claim 1, wherein applying the preamble bit sequence to the one or more symbols of the single-tone random access preamble comprises:

applying each bit value of the preamble bit sequence to a corresponding symbol of the single-tone random access preamble.
The method of claim 2, wherein the preamble bit sequence comprises an orthogonal cover code (OCC) scrambling sequence.
The method of claim 2, wherein a bit length of the preamble bit sequence is equal to a symbol length of the single-tone random access preamble.
The method of claim 2, wherein a bit length of the preamble bit sequence is less than a symbol length of the single-tone random access preamble, and wherein applying each bit value of the preamble bit sequence to the corresponding symbol of the plurality of repetitions of the single-tone random access preamble comprises:

cyclically applying each bit value of a plurality of cycles of the preamble bit sequence to corresponding symbols of the single-tone random access preamble.
The method of claim 2, wherein each symbol group of the single-tone random access preamble comprises a cyclic prefix prior to each symbol of the symbol group.
The method of claim 2, wherein each symbol group of the single-tone random access preamble comprises a single cyclic prefix.
The method of claim 1, wherein applying the preamble bit sequence to the one or more symbols of the single-tone random access preamble comprises:

applying each bit value of the preamble bit sequence to a contiguous subset of symbols of the single-tone random access preamble.
The method of claim 8, wherein the single-tone random access preamble comprises a cyclic prefix prior to each contiguous subsets of symbols of the single-tone random access preamble.
The method of claim 1, further comprising:

determining the preamble bit sequence based at least in part on a table stored in memory, a user equipment (UE) identifier, a base sequence seed, a coverage level grouping, or any combination thereof.
The method of claim 1, further comprising:

randomly generating the preamble index associated with the spread single-tone random access preamble； and

determining resources for transmitting the spread single-tone random access preamble, the preamble bit sequence, or both based at least in part on the preamble index and a preamble generator function.
The method of claim 1, further comprising:

identifying a random access preamble response associated with the spread single-tone random access preamble based at least in part on a radio network temporary identifier (RNTI) corresponding to the preamble bit sequence or on a field of the random access preamble response corresponding to the preamble bit sequence.
A method for wireless communication, comprising:

determining a plurality of physical random access channel (PRACH) resource sets for system access, each of the plurality of PRACH resource sets associated with a frequency hopping pattern；

receiving a spread single-tone random access preamble over a PRACH resource set of the plurality of PRACH resource sets, the spread single-tone random access preamble spread with one of a plurality of preamble bit sequences； and

transmitting a random access preamble response in response to the received spread single-tone random access preamble, wherein the random access preamble response is based at least in part on the one of the plurality of preamble bit sequences used for the spread single-tone random access preamble.
The method of claim 13, wherein the random access preamble response comprises a preamble index to be decoded using a radio network temporary identifier (RNTI) , wherein the RNTI is based at least in part on the one of the plurality of preamble bit sequences.
The method of claim 13, further comprising:

determining a preamble index based at least in part on a preamble generator function, the one of the plurality of preamble bit sequences, and resources used for receiving the spread single-tone random access preamble.
The method of claim 13, further comprising:

transmitting system information comprising an indication of the plurality of preamble bit sequences.
The method of claim 13, further comprising:

transmitting system information comprising an indication of one or more group indexes associated with different coverage levels for a cell, wherein the one of the plurality of preamble bit sequences is based at least in part on a group index of the one or more group indexes.
A method for wireless communication, comprising:

identifying, based at least in part on a preamble index, a set of physical random access channel (PRACH) resources for system access using a single-tone random access preamble, the set of PRACH resources having a frequency hopping pattern；

selecting a frequency offset value from a plurality of frequency offset values； and

transmitting the single-tone random access preamble for the system access in the set of PRACH resources according to the frequency hopping pattern and the selected frequency offset value.
The method of claim 18, wherein selecting the frequency offset value comprises:

selecting the frequency offset value from a plurality of orthogonal frequency shift values for the single-tone random access preamble.
The method of claim 19, wherein a first type of user equipment (UEs) are associated with a first tone spacing for transmission of single-tone random access preambles, and wherein the plurality of frequency offset values correspond to frequency shifts interstitial to the first tone spacing.
The method of claim 20, wherein the plurality of frequency offset values comprises a zero offset value.
The method of claim 19, further comprising:

receiving, from a base station, an indication of the plurality of orthogonal frequency shift values.
The method of claim 18, wherein selecting the frequency offset value comprises:

selecting the frequency offset value based at least in part on the frequency hopping pattern and a repetition number of the single-tone random access preamble.
The method of claim 18, further comprising:

randomly generating the preamble index associated with the single-tone random access preamble, wherein selecting the frequency offset value is based at least in part on the preamble index and a preamble generator function.
The method of claim 18, further comprising:

identifying a random access preamble response associated with the single-tone random access preamble based at least in part on a radio network temporary identifier (RNTI) corresponding to the selected frequency offset value or on a field of the random access preamble response corresponding to the selected frequency offset value.
A method for wireless communication, comprising:

determining a plurality of physical random access channel (PRACH) resource sets for system access, each of the plurality of PRACH resource sets associated with a frequency hopping pattern；

receiving a single-tone random access preamble over a PRACH resource set of the plurality of PRACH resource sets, the single-tone random access preamble transmitted using the frequency hopping pattern and one of a plurality of frequency offset values； and

transmitting a random access preamble response in response to the received single-tone random access preamble, wherein the random access preamble response is based at least in part on the one of the plurality of frequency offset values used for transmission of the single-tone random access preamble.
The method of claim 26, wherein the random access preamble response comprises a preamble index to be decoded using a radio network temporary identifier (RNTI) , wherein the RNTI is based at least in part on the one of the plurality of frequency offset values.
The method of claim 26, further comprising:

determining a preamble index based at least in part on a preamble generator function, the one of the plurality of frequency offset values, and resources used for receiving the single-tone random access preamble.
The method of claim 26, further comprising:

transmitting system information comprising an indication of the plurality of frequency offset values.
The method of claim 26, wherein the plurality of frequency offset values correspond to orthogonal frequency shifts of the single-tone random access preamble.
An apparatus for wireless communication, comprising:

means for identifying, based at least in part on a preamble index, a set of physical random access channel (PRACH) resources for system access using a single-tone random access preamble, the set of PRACH resources having a frequency hopping pattern；

means for determining a preamble bit sequence for the system access；

means for applying the preamble bit sequence to one or more symbols of the single-tone random access preamble to obtain a spread single-tone random access preamble； and

means for transmitting the spread single-tone random access preamble for the system access in the set of PRACH resources.
The apparatus of claim 31, wherein the means for applying the preamble bit sequence to the one or more symbols of the single-tone random access preamble comprises:

means for applying each bit value of the preamble bit sequence to a corresponding symbol of the single-tone random access preamble.
The apparatus of claim 32, wherein the preamble bit sequence comprises an orthogonal cover code (OCC) scrambling sequence.
The apparatus of claim 32, wherein a bit length of the preamble bit sequence is equal to a symbol length of the single-tone random access preamble.
The apparatus of claim 32, wherein the means for a bit length of the preamble bit sequence is less than a symbol length of the single-tone random access preamble, and wherein applying each bit value of the preamble bit sequence to the corresponding symbol of the plurality of repetitions of the single-tone random access preamble comprises:

means for cyclically applying each bit value of a plurality of cycles of the preamble bit sequence to corresponding symbols of the single-tone random access preamble.
The apparatus of claim 32, wherein each symbol group of the single-tone random access preamble comprises a cyclic prefix prior to each symbol of the symbol group.
The apparatus of claim 32, wherein each symbol group of the single-tone random access preamble comprises a single cyclic prefix.
The apparatus of claim 31, wherein the means for applying the preamble bit sequence to the one or more symbols of the single-tone random access preamble comprises:

means for applying each bit value of the preamble bit sequence to a contiguous subset of symbols of the single-tone random access preamble.
The apparatus of claim 38, wherein the single-tone random access preamble comprises a cyclic prefix prior to each contiguous subsets of symbols of the single-tone random access preamble.
The apparatus of claim 31, further comprising:

means for determining the preamble bit sequence based at least in part on a table stored in memory, a user equipment (UE) identifier, a base sequence seed, a coverage level grouping, or any combination thereof.
The apparatus of claim 31, further comprising:

means for randomly generating the preamble index associated with the spread single-tone random access preamble； and

means for determining resources for transmitting the spread single-tone random access preamble, the preamble bit sequence, or both based at least in part on the preamble index and a preamble generator function.
The apparatus of claim 31, further comprising:

means for identifying a random access preamble response associated with the spread single-tone random access preamble based at least in part on a radio network temporary identifier (RNTI) corresponding to the preamble bit sequence or on a field of the random access preamble response corresponding to the preamble bit sequence.
An apparatus for wireless communication, comprising:

means for determining a plurality of physical random access channel (PRACH) resource sets for system access, each of the plurality of PRACH resource sets associated with a frequency hopping pattern；

means for receiving a spread single-tone random access preamble over a PRACH resource set of the plurality of PRACH resource sets, the spread single-tone random access preamble spread with one of a plurality of preamble bit sequences； and

means for transmitting a random access preamble response in response to the received spread single-tone random access preamble, wherein the random access preamble response is based at least in part on the one of the plurality of preamble bit sequences used for the spread single-tone random access preamble.
The apparatus of claim 43, wherein the random access preamble response comprises a preamble index to be decoded using a radio network temporary identifier (RNTI) , wherein the RNTI is based at least in part on the one of the plurality of preamble bit sequences.
The apparatus of claim 43, further comprising:

means for determining a preamble index based at least in part on a preamble generator function, the one of the plurality of preamble bit sequences, and resources used for receiving the spread single-tone random access preamble.
The apparatus of claim 43, further comprising:

means for transmitting system information comprising an indication of the plurality of preamble bit sequences.
The apparatus of claim 43, further comprising:

means for transmitting system information comprising an indication of one or more group indexes associated with different coverage levels for a cell, wherein the one of the plurality of preamble bit sequences is based at least in part on a group index of the one or more group indexes.
An apparatus for wireless communication, comprising:

means for identifying, based at least in part on a preamble index, a set of physical random access channel (PRACH) resources for system access using a single-tone random access preamble, the set of PRACH resources having a frequency hopping pattern；

means for selecting a frequency offset value from a plurality of frequency offset values； and

means for transmitting the single-tone random access preamble for the system access in the set of PRACH resources according to the frequency hopping pattern and the selected frequency offset value.
The apparatus of claim 48, wherein the means for selecting the frequency offset value comprises:

means for selecting the frequency offset value from a plurality of orthogonal frequency shift values for the single-tone random access preamble.
The apparatus of claim 49, wherein a first type of user equipment (UEs) are associated with a first tone spacing for transmission of single-tone random access preambles, and wherein the plurality of frequency offset values correspond to frequency shifts interstitial to the first tone spacing.
The apparatus of claim 50, wherein the plurality of frequency offset values comprises a zero offset value.
The apparatus of claim 49, further comprising:

means for receiving, from a base station, an indication of the plurality of orthogonal frequency shift values.
The apparatus of claim 48, wherein the means for selecting the frequency offset value comprises:

means for selecting the frequency offset value based at least in part on the frequency hopping pattern and a repetition number of the single-tone random access preamble.
The apparatus of claim 48, further comprising:

means for randomly generating the preamble index associated with the single-tone random access preamble, wherein selecting the frequency offset value is based at least in part on the preamble index and a preamble generator function.
The apparatus of claim 48, further comprising:

means for identifying a random access preamble response associated with the single-tone random access preamble based at least in part on a radio network temporary identifier (RNTI) corresponding to the selected frequency offset value or on a field of the random access preamble response corresponding to the selected frequency offset value.
An apparatus for wireless communication, comprising:

means for determining a plurality of physical random access channel (PRACH) resource sets for system access, each of the plurality of PRACH resource sets associated with a frequency hopping pattern；

means for receiving a single-tone random access preamble over a PRACH resource set of the plurality of PRACH resource sets, the single-tone random access preamble transmitted using the frequency hopping pattern and one of a plurality of frequency offset values； and

means for transmitting a random access preamble response in response to the received single-tone random access preamble, wherein the random access preamble response is based at least in part on the one of the plurality of frequency offset values used for transmission of the single-tone random access preamble.
The apparatus of claim 56, wherein the random access preamble response comprises a preamble index to be decoded using a radio network temporary identifier (RNTI) , wherein the RNTI is based at least in part on the one of the plurality of frequency offset values.
The apparatus of claim 56, further comprising:

means for determining a preamble index based at least in part on a preamble generator function, the one of the plurality of frequency offset values, and resources used for receiving the single-tone random access preamble.
The apparatus of claim 56, further comprising:

means for transmitting system information comprising an indication of the plurality of frequency offset values.
The apparatus of claim 56, wherein the plurality of frequency offset values correspond to orthogonal frequency shifts of the single-tone random access preamble.
An apparatus for wireless communication, comprising:

a processor；

memory in electronic communication with the processor； and

instructions stored in the memory and executable by the processor to cause the apparatus to:

identify, based at least in part on a preamble index, a set of physical random access channel (PRACH) resources for system access using a single-tone random access preamble, the set of PRACH resources having a frequency hopping pattern；

determine a preamble bit sequence for the system access；

apply the preamble bit sequence to one or more symbols of the single-tone random access preamble to obtain a spread single-tone random access preamble； and

transmit the spread single-tone random access preamble for the system access in the set of PRACH resources.
The apparatus of claim 61, wherein the instructions to apply the preamble bit sequence to the one or more symbols of the single-tone random access preamble are executable by the processor to cause the apparatus to:

apply each bit value of the preamble bit sequence to a corresponding symbol of the single-tone random access preamble.
The apparatus of claim 62, wherein the preamble bit sequence comprises an orthogonal cover code (OCC) scrambling sequence.
The apparatus of claim 62, wherein a bit length of the preamble bit sequence is equal to a symbol length of the single-tone random access preamble.
The apparatus of claim 62, wherein the instructions to a bit length of the preamble bit sequence is less than a symbol length of the single-tone random access preamble, and wherein applying each bit value of the preamble bit sequence to the corresponding symbol of the plurality of repetitions of the single-tone random access preamble are executable by the processor to cause the apparatus to:

cyclically apply each bit value of a plurality of cycles of the preamble bit sequence to corresponding symbols of the single-tone random access preamble.
The apparatus of claim 62, wherein each symbol group of the single-tone random access preamble comprises a cyclic prefix prior to each symbol of the symbol group.
The apparatus of claim 62, wherein each symbol group of the single-tone random access preamble comprises a single cyclic prefix.
The apparatus of claim 61, wherein the instructions to apply the preamble bit sequence to the one or more symbols of the single-tone random access preamble are executable by the processor to cause the apparatus to:

apply each bit value of the preamble bit sequence to a contiguous subset of symbols of the single-tone random access preamble.
The apparatus of claim 68, wherein the single-tone random access preamble comprises a cyclic prefix prior to each contiguous subsets of symbols of the single-tone random access preamble.
The apparatus of claim 61, wherein the instructions are further executable by the processor to cause the apparatus to:

determine the preamble bit sequence based at least in part on a table stored in memory, a user equipment (UE) identifier, a base sequence seed, a coverage level grouping, or any combination thereof.
The apparatus of claim 61, wherein the instructions are further executable by the processor to cause the apparatus to:

randomly generate the preamble index associated with the spread single-tone random access preamble； and

determine resources for transmitting the spread single-tone random access preamble, the preamble bit sequence, or both based at least in part on the preamble index and a preamble generator function.
The apparatus of claim 61, wherein the instructions are further executable by the processor to cause the apparatus to:

identify a random access preamble response associated with the spread single-tone random access preamble based at least in part on a radio network temporary identifier (RNTI) corresponding to the preamble bit sequence or on a field of the random access preamble response corresponding to the preamble bit sequence.
An apparatus for wireless communication, comprising:

a processor；

memory in electronic communication with the processor； and

instructions stored in the memory and executable by the processor to cause the apparatus to:

determine a plurality of physical random access channel (PRACH) resource sets for system access, each of the plurality of PRACH resource sets associated with a frequency hopping pattern；

receive a spread single-tone random access preamble over a PRACH resource set of the plurality of PRACH resource sets, the spread single-tone random access preamble spread with one of a plurality of preamble bit sequences； and

transmit a random access preamble response in response to the received spread single-tone random access preamble, wherein the random access preamble response is based at least in part on the one of the plurality of preamble bit sequences used for the spread single-tone random access preamble.
The apparatus of claim 73, wherein the random access preamble response comprises a preamble index to be decoded using a radio network temporary identifier (RNTI) , wherein the RNTI is based at least in part on the one of the plurality of preamble bit sequences.
The apparatus of claim 73, wherein the instructions are further executable by the processor to cause the apparatus to:

determine a preamble index based at least in part on a preamble generator function, the one of the plurality of preamble bit sequences, and resources used for receiving the spread single-tone random access preamble.
The apparatus of claim 73, wherein the instructions are further executable by the processor to cause the apparatus to:

transmit system information comprising an indication of the plurality of preamble bit sequences.
The apparatus of claim 73, wherein the instructions are further executable by the processor to cause the apparatus to:

transmit system information comprising an indication of one or more group indexes associated with different coverage levels for a cell, wherein the one of the plurality of preamble bit sequences is based at least in part on a group index of the one or more group indexes.
An apparatus for wireless communication, comprising:

a processor；

memory in electronic communication with the processor； and

instructions stored in the memory and executable by the processor to cause the apparatus to:

identify, based at least in part on a preamble index, a set of physical random access channel (PRACH) resources for system access using a single-tone random access preamble, the set of PRACH resources having a frequency hopping pattern；

select a frequency offset value from a plurality of frequency offset values； and

transmit the single-tone random access preamble for the system access in the set of PRACH resources according to the frequency hopping pattern and the selected frequency offset value.
The apparatus of claim 78, wherein the instructions to select the frequency offset value are executable by the processor to cause the apparatus to:

select the frequency offset value from a plurality of orthogonal frequency shift values for the single-tone random access preamble.
The apparatus of claim 79, wherein a first type of user equipment (UEs) are associated with a first tone spacing for transmission of single-tone random access preambles, and wherein the plurality of frequency offset values correspond to frequency shifts interstitial to the first tone spacing.
The apparatus of claim 80, wherein the plurality of frequency offset values comprises a zero offset value.
The apparatus of claim 79, wherein the instructions are further executable by the processor to cause the apparatus to:

receive, from a base station, an indication of the plurality of orthogonal frequency shift values.
The apparatus of claim 78, wherein the instructions to select the frequency offset value are executable by the processor to cause the apparatus to:

select the frequency offset value based at least in part on the frequency hopping pattern and a repetition number of the single-tone random access preamble.
The apparatus of claim 78, wherein the instructions are further executable by the processor to cause the apparatus to:

randomly generate the preamble index associated with the single-tone random access preamble, wherein selecting the frequency offset value is based at least in part on the preamble index and a preamble generator function.
The apparatus of claim 78, wherein the instructions are further executable by the processor to cause the apparatus to:

identify a random access preamble response associated with the single-tone random access preamble based at least in part on a radio network temporary identifier (RNTI) corresponding to the selected frequency offset value or on a field of the random access preamble response corresponding to the selected frequency offset value.
An apparatus for wireless communication, comprising:

a processor；

memory in electronic communication with the processor； and

instructions stored in the memory and executable by the processor to cause the apparatus to:

determine a plurality of physical random access channel (PRACH) resource sets for system access, each of the plurality of PRACH resource sets associated with a frequency hopping pattern；

receive a single-tone random access preamble over a PRACH resource set of the plurality of PRACH resource sets, the single-tone random access preamble transmitted using the frequency hopping pattern and one of a plurality of frequency offset values； and

transmit a random access preamble response in response to the received single-tone random access preamble, wherein the random access preamble response is based at least in part on the one of the plurality of frequency offset values used for transmission of the single-tone random access preamble.
The apparatus of claim 86, wherein the random access preamble response comprises a preamble index to be decoded using a radio network temporary identifier (RNTI) , wherein the RNTI is based at least in part on the one of the plurality of frequency offset values.
The apparatus of claim 86, wherein the instructions are further executable by the processor to cause the apparatus to:

determine a preamble index based at least in part on a preamble generator function, the one of the plurality of frequency offset values, and resources used for receiving the single-tone random access preamble.
The apparatus of claim 86, wherein the instructions are further executable by the processor to cause the apparatus to:

transmit system information comprising an indication of the plurality of frequency offset values.
The apparatus of claim 86, wherein the plurality of frequency offset values correspond to orthogonal frequency shifts of the single-tone random access preamble.
A non-transitory computer-readable medium storing code for wireless communication, the code comprising instructions executable by a processor to:

identify, based at least in part on a preamble index, a set of physical random access channel (PRACH) resources for system access using a single-tone random access preamble, the set of PRACH resources having a frequency hopping pattern；

determine a preamble bit sequence for the system access；

apply the preamble bit sequence to one or more symbols of the single-tone random access preamble to obtain a spread single-tone random access preamble； and

transmit the spread single-tone random access preamble for the system access in the set of PRACH resources.
The non-transitory computer-readable medium of claim 91, wherein the instructions to apply the preamble bit sequence to the one or more symbols of the single-tone random access preamble are executable by the processor to:

apply each bit value of the preamble bit sequence to a corresponding symbol of the single-tone random access preamble.
The non-transitory computer-readable medium of claim 92, wherein the preamble bit sequence comprises an orthogonal cover code (OCC) scrambling sequence.
The non-transitory computer-readable medium of claim 92, wherein a bit length of the preamble bit sequence is equal to a symbol length of the single-tone random access preamble.
The non-transitory computer-readable medium of claim 92, wherein the instructions to a bit length of the preamble bit sequence is less than a symbol length of the single-tone random access preamble, and wherein applying each bit value of the preamble bit sequence to the corresponding symbol of the plurality of repetitions of the single-tone random access preamble are executable by the processor to:

cyclically apply each bit value of a plurality of cycles of the preamble bit sequence to corresponding symbols of the single-tone random access preamble.
The non-transitory computer-readable medium of claim 92, wherein each symbol group of the single-tone random access preamble comprises a cyclic prefix prior to each symbol of the symbol group.
The non-transitory computer-readable medium of claim 92, wherein each symbol group of the single-tone random access preamble comprises a single cyclic prefix.
The non-transitory computer-readable medium of claim 91, wherein the instructions to apply the preamble bit sequence to the one or more symbols of the single-tone random access preamble are executable by the processor to:

apply each bit value of the preamble bit sequence to a contiguous subset of symbols of the single-tone random access preamble.
The non-transitory computer-readable medium of claim 98, wherein the single-tone random access preamble comprises a cyclic prefix prior to each contiguous subsets of symbols of the single-tone random access preamble.
The non-transitory computer-readable medium of claim 91, wherein the instructions are further executable by the processor to:

determine the preamble bit sequence based at least in part on a table stored in memory, a user equipment (UE) identifier, a base sequence seed, a coverage level grouping, or any combination thereof.
The non-transitory computer-readable medium of claim 91, wherein the instructions are further executable by the processor to:

randomly generate the preamble index associated with the spread single-tone random access preamble； and

determine resources for transmitting the spread single-tone random access preamble, the preamble bit sequence, or both based at least in part on the preamble index and a preamble generator function.
The non-transitory computer-readable medium of claim 91, wherein the instructions are further executable by the processor to:

identify a random access preamble response associated with the spread single-tone random access preamble based at least in part on a radio network temporary identifier (RNTI) corresponding to the preamble bit sequence or on a field of the random access preamble response corresponding to the preamble bit sequence.
A non-transitory computer-readable medium storing code for wireless communication, the code comprising instructions executable by a processor to:

determine a plurality of physical random access channel (PRACH) resource sets for system access, each of the plurality of PRACH resource sets associated with a frequency hopping pattern；

receive a spread single-tone random access preamble over a PRACH resource set of the plurality of PRACH resource sets, the spread single-tone random access preamble spread with one of a plurality of preamble bit sequences； and

transmit a random access preamble response in response to the received spread single-tone random access preamble, wherein the random access preamble response is based at least in part on the one of the plurality of preamble bit sequences used for the spread single-tone random access preamble.
The non-transitory computer-readable medium of claim 103, wherein the random access preamble response comprises a preamble index to be decoded using a radio network temporary identifier (RNTI) , wherein the RNTI is based at least in part on the one of the plurality of preamble bit sequences.
The non-transitory computer-readable medium of claim 103, wherein the instructions are further executable by the processor to:

determine a preamble index based at least in part on a preamble generator function, the one of the plurality of preamble bit sequences, and resources used for receiving the spread single-tone random access preamble.
The non-transitory computer-readable medium of claim 103, wherein the instructions are further executable by the processor to:

transmit system information comprising an indication of the plurality of preamble bit sequences.
The non-transitory computer-readable medium of claim 103, wherein the instructions are further executable by the processor to:

transmit system information comprising an indication of one or more group indexes associated with different coverage levels for a cell, wherein the one of the plurality of preamble bit sequences is based at least in part on a group index of the one or more group indexes.
A non-transitory computer-readable medium storing code for wireless communication, the code comprising instructions executable by a processor to:

identify, based at least in part on a preamble index, a set of physical random access channel (PRACH) resources for system access using a single-tone random access preamble, the set of PRACH resources having a frequency hopping pattern；

select a frequency offset value from a plurality of frequency offset values； and

transmit the single-tone random access preamble for the system access in the set of PRACH resources according to the frequency hopping pattern and the selected frequency offset value.
The non-transitory computer-readable medium of claim 108, wherein the instructions to select the frequency offset value are executable by the processor to:

select the frequency offset value from a plurality of orthogonal frequency shift values for the single-tone random access preamble.
The non-transitory computer-readable medium of claim 109, wherein a first type of user equipment (UEs) are associated with a first tone spacing for transmission of single-tone random access preambles, and wherein the plurality of frequency offset values correspond to frequency shifts interstitial to the first tone spacing.
The non-transitory computer-readable medium of claim 110, wherein the plurality of frequency offset values comprises a zero offset value.
The non-transitory computer-readable medium of claim 109, wherein the instructions are further executable by the processor to:

receive, from a base station, an indication of the plurality of orthogonal frequency shift values.
The non-transitory computer-readable medium of claim 108, wherein the instructions to select the frequency offset value are executable by the processor to:

select the frequency offset value based at least in part on the frequency hopping pattern and a repetition number of the single-tone random access preamble.
The non-transitory computer-readable medium of claim 108, wherein the instructions are further executable by the processor to:

randomly generate the preamble index associated with the single-tone random access preamble, wherein selecting the frequency offset value is based at least in part on the preamble index and a preamble generator function.
The non-transitory computer-readable medium of claim 108, wherein the instructions are further executable by the processor to:

identify a random access preamble response associated with the single-tone random access preamble based at least in part on a radio network temporary identifier (RNTI) corresponding to the selected frequency offset value or on a field of the random access preamble response corresponding to the selected frequency offset value.
A non-transitory computer-readable medium storing code for wireless communication, the code comprising instructions executable by a processor to:

determine a plurality of physical random access channel (PRACH) resource sets for system access, each of the plurality of PRACH resource sets associated with a frequency hopping pattern；

receive a single-tone random access preamble over a PRACH resource set of the plurality of PRACH resource sets, the single-tone random access preamble transmitted using the frequency hopping pattern and one of a plurality of frequency offset values； and

transmit a random access preamble response in response to the received single-tone random access preamble, wherein the random access preamble response is based at least in part on the one of the plurality of frequency offset values used for transmission of the single-tone random access preamble.
The non-transitory computer-readable medium of claim 116, wherein the random access preamble response comprises a preamble index to be decoded using a radio network temporary identifier (RNTI) , wherein the RNTI is based at least in part on the one of the plurality of frequency offset values.
The non-transitory computer-readable medium of claim 116, wherein the instructions are further executable by the processor to:

determine a preamble index based at least in part on a preamble generator function, the one of the plurality of frequency offset values, and resources used for receiving the single-tone random access preamble.
The non-transitory computer-readable medium of claim 116, wherein the instructions are further executable by the processor to:

transmit system information comprising an indication of the plurality of frequency offset values.
The non-transitory computer-readable medium of claim 116, wherein the plurality of frequency offset values correspond to orthogonal frequency shifts of the single-tone random access preamble.