CN116325976A - Synchronization signals in a shared spectrum of a cellular network - Google Patents

Abstract

Various transmission patterns are provided for transmission of synchronization signals in an OFDM cellular communication system utilizing beam scanning techniques. In the pattern, at least one OFDM symbol gap is provided between bursts of each synchronization signal to allow switching between beams.

Description

Synchronization signals in a shared spectrum of a cellular network

Technical Field

The following disclosure relates to transmission of synchronization signals, and in particular to transmission of such signals when a base station performing beam scanning is operating in a shared transmission spectrum.

Background

Wireless communication systems, such as third generation (3G) mobile phone standards and technologies, are well known, and the third generation partnership project (3 GPP) has developed such 3G standards and technologies, and generally, third generation wireless communications have been developed to the extent that macrocell mobile phone communications are supported, communication systems and networks have been developed toward broadband and mobile systems.

In a cellular wireless communication system, a User Equipment (UE) is connected to a radio access network (Radio Access Network, RAN) by a wireless link. The RAN includes a set of base stations (base stations) providing radio links to UEs located in cells covered by the base stations and includes an interface to a Core Network (CN) having a function of controlling the overall Network. It is understood that the RAN and CN each perform a corresponding function with respect to the entire network. For convenience, the term "cellular network" will be used to represent a combination of RAN and CN, but it will be understood that the term is also used to represent various systems for performing the disclosed functions.

The third generation partnership project has evolved a so-called Long Term Evolution (LTE) system, an evolved universal mobile telecommunications system regional radio access network (E-UTRAN), for a mobile access network of one or more macro cells supported by base stations called enodebs or enbs (evolved nodebs). Recently, LTE has evolved further to so-called 5G or New Radio (NR) systems, where one or more cells are supported by a base station called a gNB. When NR is proposed, an orthogonal frequency division multiplexing (Orthogonal Frequency Division Multiplexed, OFDM) physical transport format is utilized.

The NR protocol is intended to provide the option of operating in the unlicensed radio frequency range (referred to as NR-U). While operating in the unlicensed radio band, the gNB and UE must compete for physical medium/resource access with other devices. For example, wi-Fi, NR-U, and LAA may use the same physical resources.

The trend in wireless communication is toward services that provide lower latency and higher reliability. For example, NR is aimed at supporting Ultra-reliable and low-latency communication (URLLC), while large-scale Machine-type communication (mctc) is aimed at providing low latency and high reliability for small data packets (typically 32 bytes). A user plane delay of 1ms has been proposed with a reliability of 99.99999% and in terms of the physical layer, a packet loss ratio of 10 has been proposed ^-5 Or 10 ^-6 Is provided.

The mctc service aims to support a large number of devices with an energy efficient communication channel over a long lifetime. In this case, data transmission with each device is sporadic and infrequently performed. For example, a cell may support thousands of devices.

The following disclosure relates to various improvements to cellular wireless communication systems.

Disclosure of Invention

The present invention is defined in the claims, wherein a method of transmitting SS/PBCH bursts in an OFDM transmission system operating in frequency range 2 (FR 2) and utilizing beam scanning techniques is provided, said method comprising the steps of: selecting a plurality of starting positions to transmit the SS/PBCH burst, wherein the plurality of starting positions are selected so that a gap of at least one OFDM symbol exists between adjacent SS/PBCH bursts; and transmitting a plurality of SS/PBCH bursts, wherein each SS/PBCH burst begins at one of the selected plurality of starting locations.

The system uses a subcarrier spacing of 120 kHz.

The plurality of start positions is set at OFDM symbol number 4,9,15,20 +28 x n, where n=0, 1,..15, reference symbol index 0 corresponds to the first symbol of the first slot in the field transmitting the SS/PBCH block.

The plurality of start positions is set at OFDM symbol number 2,8,15,20 +28 x n, where n=0, 1,..15, reference symbol index 0 corresponds to the first symbol of the first slot in the field transmitting the SS/PBCH block.

The plurality of start positions is set at OFDM symbol number 4,9,15,20 +28 x n, where n=0, 1,2,..19, reference symbol index 0 corresponds to the first symbol of the first slot in the field transmitting the SS/PBCH block.

The system uses a subcarrier spacing of 240 kHz.

The plurality of start positions is located at OFDM symbol number 8,14,20,32,38,44 +56 x n, where n=0, 1,2,..10, reference symbol index 0 corresponds to the first symbol of the first slot in the field transmitting the SS/PBCH block.

The plurality of start positions is located at OFDM symbol number 8,14,20,32,38,44 +56 x n, where n=0, 1,2,..19, reference symbol index 0 corresponds to the first symbol of the first slot in the field transmitting the SS/PBCH block.

The plurality of start positions is set at OFDM symbol number 8,16,32,44 +56 n, where n=0, 1,2,..15, reference symbol index 0 corresponds to the first symbol of the first slot in the field transmitting the SS/PBCH block.

The plurality of start positions is located at OFDM symbol number 8,16,32,44 +56 x n, where n=0, 1,2,..19, reference symbol index 0 corresponds to the first symbol of the first slot in the field transmitting the SS/PBCH block.

The system uses a subcarrier spacing of 480 kHz.

The plurality of start positions is located at OFDM symbol number {4,12,20} +28 x n, where n=0, 1,2,..21, reference symbol index 0 corresponds to the first symbol of the first slot in the field of the transmission SS/PBCH block.

The plurality of start positions is set at OFDM symbol number 16,32,40,64,72,88 +112, where n=0, 1,2,..10, reference symbol index 0 corresponds to the first symbol of the first slot in the field transmitting the SS/PBCH block.

The system uses a subcarrier spacing of 960 kHz.

The plurality of start positions is set at OFDM symbol number 8,20,32,44 +56 n, where n=0, 1,2,..15, reference symbol index 0 corresponds to the first symbol of the first slot in the field transmitting the SS/PBCH block.

The plurality of start positions is set at OFDM symbol number 32,44,64,76,88,128,144,156,176,188 +224 x n, where n=0, 1,2,..6, reference symbol index 0 corresponds to the first symbol of the first slot in the field transmitting the SS/PBCH block.

The method further comprises the step of transmitting an indication of the plurality of start positions.

The plurality of start positions are transmitted in the payload of the PBCH.

The reserved bits of the MIB payload are used as part of the indication of the plurality of start positions.

The number of the plurality of start positions is not more than 128.

The PBCH DMRS indicates at least a portion of the plurality of starting positions.

The plurality of start positions are indicated by SS/PBCH candidate indexes.

Drawings

Further details, aspects and embodiments of the invention are described below, by way of example only, with reference to the accompanying drawings. For simplicity and clarity, elements in the figures have been shown and are not necessarily drawn to scale. For ease of understanding, the same reference numerals are included in the various figures.

Fig. 1 shows selected elements of a cellular communication system; a kind of electronic device with high-pressure air-conditioning system

Fig. 2 to 5 show exemplary transmission modes.

Detailed Description

Those skilled in the art will recognize and appreciate that the specific details of the examples described are merely illustrative of some embodiments and that the teachings set forth herein are applicable in a variety of alternative configurations.

Fig. 1 shows a schematic diagram of three base stations (e.g., enbs or gnbs, depending on the particular cellular network standard and terminology) forming a cellular network. Typically, each base station will be deployed by a cellular network operator to provide geographic coverage for UEs in the area. These base stations form a radio area network (Radio Area Network, RAN). Each base station provides radio signal coverage for UEs in its area or cell. These base stations are interconnected by an X2 interface and connected to the core network by an S1 interface. As will be appreciated, only a few basic details are shown here to facilitate exemplary explanation of the critical features of a cellular network. The interfaces and component names associated with fig. 1 for providing a PC5 interface between multiple UEs for side-chain (SL) communication are merely for example, and different systems operating on the same principles may use different nomenclature.

Each base station includes hardware and software for implementing RAN functions including functions to communicate with the core network and other base stations, the piggybacking of control and data signals between the core network and the UEs, and maintaining or maintaining wireless communications of the UEs associated with each base station. The core network includes hardware and software for implementing network functions such as management and control of the overall network, and routing of calls and data.

Various techniques for transmitting synchronization signals in a cellular network are listed below, which may be particularly suitable for use with larger subcarrier spacing in a shared transmission spectrum.

The UE uses a cell search procedure to synchronize time and frequency with the cell, which also detects the physical layer cell identity of the cell. Synchronization is accomplished based on the primary synchronization signal (Primary Synchronisation Signal, PSS) and the secondary synchronization signal (Secondary Synchronisation Signal, SSS) transmitted by the base station receiving the cell. The base station transmits physical broadcast channels (Physical Broadcast Channel, PBCH), PSS, and SSs in consecutive symbols of the SS/PBCH block. PSS and SSS enable the UE to synchronize with the base station/cell, PBCH is decoded to provide basic system information to enable the UE to complete configuration and initiate communication. The format of SS/PBCH blocks is specified in TS 38.211. The burst of SS/PBCH blocks has a time span of 5 milliseconds during which the base station may transmit SS/PBCH blocks for the active beam. The SS/PBCH block of the active beam is always limited to this 5 millisecond burst window. The transmission mode of SS/PBCH blocks is specified in TS 38.213.

The base station may operate in a beam-based mode in which transmissions are made on beams in a particular direction, rather than using omni-directional transmissions. In Frequency Range 1 (Frequency Range 1, FR 1), it has been proposed to support up to 8 beams, while in Frequency Range 2 (FR 2) up to 64 beams are supported. Due to limitations on the device (especially in FR 2), the base station may not be able to transmit on all beams simultaneously, and thus may utilize beam scanning operations, where transmissions are made sequentially on each beam (or subset of beams). When operating with beam scanning, each beam may transmit its own SS/PBCH block to ensure that the UE receives the signal and synchronization can be achieved.

The standard specifies that the UE determines the system timing by determining a system frame number (system frame number, SFN), a flag of the semi-radio frame, and a beam index. The beam index corresponds to the position of a given SS/PBCH block in a given field in an SS/PBCH burst. The terms "beam index" and "SS/PBCH block candidate location index" are used synonymously hereinafter. Upon successful decoding of the PBCH, the SFN, field flag and beam index become available at the UE, the PBCH being part of the SS/PBCH block transmitted by the base station. The PBCH is used to transmit a master information block (master information block, MIB) received from a higher layer, to which the physical layer adds some additional information in the form of a PBCH payload. The radio frame identity indicated by a 10-bit SFN (denoted as bits s0 to s 9) is ensured by transmitting the 6 most significant bits (most significant bit, MSB) s4 to s9 in the MIB payload. MIB payloads are transport blocks provided from the medium access control (medium access control, MAC) layer to the physical layer. The four least significant bits (least significant bit, LSB) s0 to s3 and field flag bits of the SFN are transmitted as part of the PBCH payload. The physical layer adds the PBCH payload to the MIB payload and transmits the combined MIB payload and PBCH payload through the PBCH after the physical layer processes.

For beam index identification, 6 bits b0-b5 are needed to indicate the maximum 64 beams allowed by FR2.3 (or the position of SS/PBCH in the burst), where LSB b0-b2 is transmitted using PBCH demodulation reference symbols (demodulation reference symbol, DMRS) by modulating the initialization sequence used to generate the DMRS. The 3 MSBs b3 to b5 are transmitted as part of the PBCH payload that the physical layer adds to the MIB. More than 6 bits or bits may be used to allow the number of beam or SS/PBCH candidate locations to be increased.

In order to make it possible to use beam scanning and allow transmission of SS/PBCH blocks, a suitable transmission mode is required, in particular for operation of the FR2 unlicensed spectrum, which requires a suitable channel access procedure to share the transmission resources.

The following provides a design of SS/PBCH bursts that enables synchronization of UEs when operating in a shared FR2 spectrum for beam scanning. And, a specific transmission mode is disclosed below to avoid overlapping with scheduled transmission, and an increased number of SS/PBCH candidate locations may be further provided to solve the problem of channel uncertainty in the shared spectrum.

For operation on the 6GHz unlicensed spectrum, the channel access procedure for transmitting SS/PBCH blocks employs a certain duration under the following conditions: (i) no unicast data, (ii) at most 1 millisecond during transmission, and (iii) a burst duty cycle of at most 1/20 is found. For the 6GHz spectrum, 3gpp ts37.213 has specified using a DL channel access procedure of type 2A for transmission of SS/PBCH blocks with non-unicast information, wherein the base station will sense for an interval of at least 25 microseconds.

The 25 microsecond period is divided into 16 microsecond periods (sensing at the beginning), followed by a 9 microsecond sensing time slot. These parameters are intended to ensure fair coexistence with Wi-Fi devices that use a short inter-frame space (Short Interframe Space, SIFS) of 16 microseconds and one basic sensing time slot of 9 microseconds for frequencies around 6 GHz. SIFS is a period of time that the Wi-Fi system uses to indicate a delay during which the receiving device processes a received frame and responds to indicate the correct reception of a data packet as part of a hybrid-automatic repeat request (HARQ) mechanism. The SIFS period is also used when the receiving device participates in a channel access procedure in a request-to-send (request-to-send) and clear-to-send (clear-to-send) procedure.

To avoid interrupting ongoing communications within the SIFS gap, the Wi-Fi system allows a priority channel access procedure comprising a SIFS period and at least one sensing time slot. Thus, even a preferential transmission, e.g., from a Wi-Fi access point, may only start after SIFS plus one sensing slot, which ensures that ongoing communication between a pair of devices that may have one SIFS gap is not disrupted.

For 802.11ad enhanced functionality operating in the 60GHz region, the SIFS period has been updated to 3 microseconds and the duration of the sensing time slot has been updated to 5 microseconds, as defined in section 21.12.4 of section 11 of the associated Wi-Fi standard.

The 802.11ad adjusted timing may be applied to cellular channel access procedures to ensure fair coexistence. Thus, the UE may use a channel sensing period of at least 8 microseconds before proceeding with SS/PBCH transmission. This 8 microsecond period is a combination of a SIFS period of 3 microseconds and a sensing time slot of 5 microseconds.

This 8 microsecond interval is divided into two intervals, a 3 microsecond interval, followed by a 5 microsecond interval. The base station may transmit SS/PBCH without unicast data only if it detects that both time intervals are idle (i.e., the energy detected on the channel during both time intervals is below a specified energy detection threshold). Other conditions, such as duty cycle and maximum channel occupancy time, may also be employed if required by the relevant regulations. The sensing may be performed omnidirectionally or directionally.

The new reference timing described in 802.11ad can also be used for deterministic channel access for cellular operation. When a base station or UE gains channel access over a shared spectrum, there is a gap of at least 3 microseconds (because one device starts transmitting over the channel acquired by the other device, or because the same device transmits after a gap), requiring the device to perform channel sensing for 3 microseconds. This channel sensing is equivalent to type 2B channel sensing suitable for 60GHz operation.

Similarly, if channel access has been achieved and there is a gap of less than 3 microseconds, transmission can be resumed without channel sensing. This behavior is allowed because in the absence of a sensing period of at least 3 microseconds, no device should acquire a channel and therefore should not start any transmission in a gap of less than 3 microseconds. This channel sensing is equivalent to type 2C channel sensing suitable for 60GHz operation, considering coexistence with 802.11ad devices.

As described above, when beam scanning is used, the base station does not transmit on all beams simultaneously, which means that there is a gap of variable time period in each beam direction when another beam is used. During the time of these gaps on transmission, other devices may have acquired the channel to begin transmission, and therefore, should perform a channel access procedure of at least 8 microseconds as described above before beginning transmission on a new beam, even if channel access has been previously acquired. As described above, the sensing may be performed omnidirectionally or directionally. This applies to the transmission of SS/PBCH blocks for a given beam.

The standard allows high frequency operation using a subcarrier spacing of 60KHz or greater. Version 15 (Rel-15) has been standardized for the pattern of SS/PBCH blocks of the SCS of 120kHz and 240kHz, with 240kHz being used only for SS/PBCH block transmission and not for data transmission. For higher frequency operation, where the carrier bandwidth may be very large (GHz), a larger SCS may be needed to help solve the problem of large-size FFT, which may become a bottleneck as the number of subcarriers becomes very large. In this regard, for FR2, it may be advantageous to select a fairly large SCS of up to 960kHz or even 1920 kHz. This would require designing a new SS/PBCH block mode to be compatible with the transmission of SS/PBCH blocks in different beam directions and possibly allow different SCS to be used for the transmission of SS/PBCH blocks and other control and data.

Wi-Fi and its corresponding high frequency technology WiGig (which includes the 802.11ad standard) follow the "listen before talk" channel access procedure for operation in unlicensed spectrum. For coexistence in a shared unlicensed spectrum, the cellular base station may apply equivalent procedures. Current designs for SS/PBCH block transmissions for SCS at 120kHz and 240kHz have SS/PBCH blocks sent consecutively from different beams. This is attractive for operation in licensed spectrum, where SS/PBCH blocks can be compressed to a shorter time span, thus maximizing flexibility in scheduling/control over the remaining time. However, when operating in unlicensed spectrum, as described above, a channel access procedure may be required before transmission begins on a new beam, thus impeding continuous transmission between beams. The channel access procedure discussed above may be appropriate before starting transmission on a beam where there is already a gap in transmission.

Described below is a design of SS/PBCH block transmission in a beam-based transmission system. These designs are independent of the particular type of channel access procedure at beam switching. The proposed design provides containment of beam switching delays and associated transitions that may affect the detection probability of SS/PBCH blocks transmitted without sufficient gaps for beam switching. The disclosed techniques employ SS/PBCH block bursts with time gaps between consecutive SS/PBCH blocks. There is thus provided a method of transmitting synchronisation signals from a base station on a plurality of beams, wherein the signals are arranged in bursts with a time gap between signals transmitted on each beam.

When operating at 120kHz SCS, each OFDM symbol is approximately 8.9 microseconds. The indicated 8 microsecond sensing time period can thus be accommodated in the gap of 1 OFDM symbol (at 120 kHz). At 240kHz, each OFDM symbol is approximately 4.5 microseconds, so 2 OFDM symbols are required to allow a sensing period of 8 microseconds. Similarly, 4 and 8 OFDM symbols are required for SCS at 480kHz and 960kHz, respectively, for channel sensing for a period of at least 8 microseconds.

Described below is the design of SS/PBCH block bursts for SCS of 120kHz to 960 kHz. All designs presented here ensure a minimum gap for channel sensing prior to beam switching. Furthermore, since the SCS of SS/PBCH blocks may be different from the SCS of control/data, these designs strive to maximize the opportunity for DL and UL control for different parameter sets (SCS). DL control is typically sent in the first few symbols of one slot in the control (data) parameter set, helping the base station to schedule resources for DL and UL transmissions. UL control is typically arranged in the last few symbols of a slot to help the base station receive HARQ feedback and UL control information.

Fig. 2 shows two proposed designs (D1-120 and D2-120) of SS/PBCH block mode for a 120kHz subcarrier spacing. The goal of this design is to harmonize the operation of SS/PBCH blocks transmitted using 120kHz and maximize the possibility of DL/UL control transmission opportunities for SCS starting from 60 kHz. The 60kHz is chosen because these lower SCS's of 15kHz and 30kHz only allow use at the lower frequency range FR1 in 3 GPP. Figure 2 shows one slot (14 symbols) of a 60kHz SCS, spanning 28 and 56 symbols for 120kHz and 240kHz SCS, respectively. The first 3 rows show symbols from 60kHz to 120kHz SCS, with the applicable SCS being noted in the first column. For the SCS in each corresponding row, the first two symbols have been highlighted to show possible downlink control transmissions and the last two symbols have been highlighted to show possible uplink control transmissions. The two rows at the bottom provide proposed designs (D1-120 and D2-120) for the SS/PBCH block mode of the 120kHz SCS.

In FIG. 2, designed for D1-120, the candidate locations are:

·D1_120＝{4,9,15,20}+28*n

·n＝0,1,2,...,15

the design D1-120 in fig. 2 is such that there is at least one OFDM symbol gap between successive SS/PBCH blocks, which provides more than 8 microseconds for channel sensing to occur after beam switching. This design avoids any overlap with 60kHz SCS DL and UL control. This provides 1 non-overlapping DL and UL control for two slots of the 120kHz SCS. This also provides gaps at symbols 13 and 14, which allows single symbol UL control and single symbol DL control to be implemented separately. This provides control opportunities for DL and UL halves for SCS at 240 kHz.

In FIG. 2, designed for D2-120, the candidate locations are:

·D2_120＝{2,8,15,20}+28*n

·n＝0,1,2,...,15

this design (D2-120) also has at least one OFDM symbol gap between each SS/PBCH block, thus providing at least 8 microseconds to perform channel sensing between successive beams. In addition to having a similar gap introduction as d1_120, d2_120 has a different compromise in terms of overlap with the control position. Since only a single symbol of the control resource set is allowed, DL control can be transmitted within a single symbol. Conversely, for UL control, there is a need for a switching gap, a time advance, and uplink control transmission on at least one symbol. With this difference in UL and DL control, the positions of the first two SS/PBCH candidates are slightly shifted in d2_120 to overlap with the 60KHz DL control in part. The 60kHz DL control transmission at the beginning of a slot has no overlap for only the first symbol, but there are more DL and UL control transmission opportunities for the SCS of 120 and 240kHz, as shown in fig. 2.

The design of fig. 2 provides 4 SS/PBCH blocks for each slot (0.25 microseconds) of the 60kHz SCS. Thus, within 5 milliseconds (the duration of an SS/PBCH burst), there are 80 candidate SS/PBCH block locations.

The first 64 SS/PBCH block candidate locations may be used when the transmission carrier is part of the licensed spectrum. And when the transmission carrier is part of the shared unlicensed spectrum, the location of the SS/PBCH block may not be used because of channel access uncertainty (i.e., channel sensing when switching to a new beam detects a transmission). If certain locations are not available due to lack of channel access, additional SS/PBCH candidate locations may be provided for utilization within the burst span. Each SS/PBCH block may be identified with its beam index so that the UE may be provided with the necessary information to be able to determine the complete system timing information.

These designs allow all candidate locations of the SS/PBCH to be used for transmission within a 5 ms window. This is reserved because 5 milliseconds has been defined as the period of the SS/PBCH burst. If this burst period is modified, the same approach can be used to make additional locations available to the SS/PBCH by utilizing all locations matching it in the updated burst period.

For the proposed designs, each design provides 2 SS/PBCH block candidate locations in one 120KHz slot. Since the SCS at 120kHz in 5 milliseconds has 40 slots, this design will provide a total of 80 SS/PBCH candidate locations. Thus, candidate locations for designs D1-120 of 120kHz SCS are:

·D1_120＝{4,9,15,20}+28*n

·n＝0,1,2,...,19

the only difference is the possible value of n, here from 0 to 19. The same variation is also applicable to the second design D2-120 in FIG. 2. Of these 80 locations, the beam index (or more precisely, the index of the SS/PBCH candidate location) will require 7 bits. In the conventional design, there are 6 bits to use to transmit an index of one of the 64 beams, 3 bits are transmitted using the PBCH DMRS, and 3 bits are transmitted as the PBCH payload. The proposed design for 120kHz SCS in fig. 2 requires the transmission of an additional bit so that the UE can determine the system timing information. Techniques for transmitting beam indices (or SS/PBCH candidate location indices) are disclosed below.

Fig. 3 shows a proposed design of SS/PBCH block mode for 240kHz subcarrier spacing. The goal of these designs is to coexist with SS/PBCH blocks transmitted using 120kHz to maximize the probability of DL/UL control transmission opportunities for SCS starting at 60 kHz. Fig. 3 shows a slot (14 symbols) of 60kHz SCS, corresponding in time to 28 symbols of 120kHz SCS and 56 symbols of 240kHz SCS, respectively. The first 3 rows show symbols from 60kHz to 120kHz SCS, with the relevant SCS noted in the first column. For the SCS in each corresponding row, the first two symbols have been highlighted to show possible downlink control transmissions and the last two symbols have been highlighted to show possible uplink control transmissions. The two rows at the bottom provide proposed designs (D1-240 and D2-240) for the SS/PBCH block mode of the 240kHz SCS.

For 240kHz SCS, the candidate locations for the first design (D1-240) of FIG. 3 are:

·D1_240＝{8,14,20,32,38,44}+56*n

·n＝0,1,2,...,10

where in implementing 64 beams, for n=10, only the first 4 candidate SS/PBCH locations are used.

This design (D1-240 of fig. 4) is with at least two OFDM symbol gaps between consecutive SS/PBCH blocks, which provides more than 8 microseconds for channel sensing between transmissions of consecutive beams. This design avoids overlap with 60kHz and 120kHz SCS DL and UL control opportunities. For the 4 slots of 240kHz SCS shown in fig. 3, this provides that there are 3 control opportunities in the 4 DL without overlap and 3 control opportunities in the 4 UL without overlap. One advantage of this design is that it provides 6 SS/PBCH candidate locations in 250 microseconds, and thus 64 SS/PBCH candidate locations in less than 2.75 milliseconds. Adapting all SS/PBCH candidate locations in a shorter time increases the flexibility of data/control transmissions in the beam where the user is located, thereby increasing system efficiency.

For unlicensed spectrum, this possibility of unavailability of SS/PBCH locations due to channel uncertainty can be compensated by making all candidate locations available within the SS/PBCH burst period. For designs D1-240 in FIG. 4, there are 120 positions within 5 milliseconds. These candidate locations are as follows:

·D1_240＝{8,14,20,32,38,44}+56*n

·n＝0,1,2,...,19

For 120 candidate locations, 7 bits are required to convey the beam index (or index of SS/PBCH candidate locations). This means that there is one bit in addition to the conventional design of 64 beam positions in release 15 (Rel-15)/16 (Rel-16) of 3 GPP.

The candidate locations for the second design D2-240 of 240kHz SCS in FIG. 4 are:

·D2_240＝{8,16,32,44}+56*n

·n＝0,1,2,...,15

a first advantage of this design (D2-240) is that the minimum distance between two consecutive SS/PBCH blocks is at least 4 OFDM symbols of 240kHz SCS. This means that the design can be used for other situations or for operating frequencies where the channel sensing period is longer. The minimum gap of 4 OFDM symbols of 240kHz SCS means that even 16 microsecond sensing time can be accommodated. Another advantage of this design is that it overlaps zero with any DL/UL control opportunity from the 60kHz SCS parameter set to the 240kHz SCS parameter set. Therefore, the design has no limitation on DL/UL control, making system operation more convenient, and has no limitation on scheduled transmission or HARQ feedback transmission in uplink direction, which is very valuable for services with strict requirements on delay.

For the unlicensed case, all possible SS/PBCH candidate locations that fit within the SS/PBCH burst window may be used. In this unauthorized case, the candidate locations for this design are:

·D2_240＝{8,16,32,44}+56*n

·n＝0,1,2,...,19

This provides 80 candidate locations for SS/PBCH transmission, which requires an indication of the beam index (SS/PBCH candidate location index), which needs to include an indication of 7 bits or bits.

Fig. 4 shows the design of SS/PBCH block bursts for a 480kHz subcarrier spacing. This design supports the transmission of SS/PBCH blocks using 480kHz SCS while fully allowing the opportunity for DL/UL control transmission of all SCS starting from 60 kHz. Fig. 4 shows that one slot (14 symbols) of the 60kHz SCS corresponds to 4 slots of the 240kHz SCS. This figure is made up of four sub-pictures stacked on top of each other, where each sub-picture shows one slot of 240kHz SCS.

For each sub-graph in fig. 4, the first 5 rows show symbols from 60kHz to 960kHz SCS, with the relevant SCS noted in the first column. For SCS in each corresponding row, the first two symbols in a slot have been highlighted to show possible downlink control transmissions and the last two symbols have been highlighted to show possible uplink control transmissions. The two rows at the bottom provide two proposed designs (D1-480 and D2-480) of the SS/PBCH block burst of 480kHz SCS.

The design of fig. 4 has a gap of at least 4 symbols between consecutive SS/PBCH blocks, which allows for channel access periods of up to 8 microseconds. The first design (D1-480) is suitable for cases where the data/control SCS is 240KHz or greater because it is constructed in a manner that does not consider the DL/UL control positions of the 60 and 120kHz SCS. This design does not overlap with the DL/UL control of 240kHz SCS, but overlaps with half of all DL/UL control positions of 480kHz SCS.

For 480kHz SCS, candidate locations for designs D1-480 of FIG. 4 are:

·D1_480＝{4,12,20}+28*n

·n＝0,1,2,...,21

for n=21, only the first candidate location is used to implement 64 SS/PBCH candidate locations.

For the unlicensed case, all SS/PBCH locations may be used within a burst span of 5 milliseconds, so n will range from 0 to 79, providing 240 SS/PBCH candidate locations. This would require an 8 bit indication to indicate SS/PBCH candidate locations.

The second design (D2-480) of fig. 4 is more inclusive and ensures that there is no overlap of DL/control opportunities starting from the control/data SCS of 60kHz at the cost of reduced SS/PBCH density per unit time. This design overlaps with DL/UL control zeros for 60, 120, 240kHz SCS, while the overlap with DL/UL control opportunities for 480 and 960kHz SCS is very limited.

For 480kHz SCS, the candidate locations for the second design (D2-480) of FIG. 4 are:

·D2_480＝{16,32,40,64,72,88}+112*n

·n＝0,1,2,...,10

where for n=10, the first 4 candidate locations are used to implement 64 SS/PBCH candidate locations.

For the unlicensed case, n is from 0 to 19, providing 120 SS/PBCH candidate locations. This would require an indication of 7 bits to indicate SS/PBCH candidate locations.

The main feature of the design d2_480 is that smooth coexistence can be achieved when the system allows any subcarrier spacing from 60KHz for DL/UL control and data transmission. D1_480, on the other hand, is designed without consideration of overlap with 60KHz and 120KHz subcarrier spacing. This allows d1_480 to have a higher SS/PBCH density in time and SS/PBCH bursts to be completed in a shorter time, thereby improving system efficiency.

The basic principle behind the first design d1_480 is that d1_480 may become a fairly excellent design, for example, if the system is operated in such a way that 480KHz and 960KHz subcarrier spacing is only used for SS/PBCH, while data and control is 240KHz or higher. On the other hand, d2—480 is a better choice if it is necessary to ensure that the subcarrier spacing from 60KHz coexist with all the subcarrier spacing of FR 2.

Fig. 5 shows a proposed design of SS/PBCH block burst for 960kHz subcarrier spacing. Fig. 5 shows that one slot (14 symbols) of the 60kHz SCS corresponds to 4 slots of the 240kHz SCS. Fig. 6 is composed of four sub-graphs stacked on top of each other, wherein each sub-graph shows one slot of 240kHz SCS.

For each sub-graph, the first 5 rows show symbols from 60kHz to 960kHz SCS, with the relevant SCS noted in the first column. For SCS in each corresponding row, the first two symbols in a slot have been highlighted to show possible downlink control transmissions and the last two symbols have been highlighted to show possible uplink control transmissions. The two rows at the bottom provide two proposed designs for SS/PBCH block burst of 960kHz SCS.

The design of fig. 5 (d1_960 and d2_960) has a gap of at least 8 symbols between consecutive SS/PBCH blocks, which allows for channel access periods of up to 8 microseconds. The first design is applicable where the data/control SCS is at least 240KHz or greater, because it is constructed in a manner that does not take into account the DL/UL control location of the 60/120kHz SCS. This design does not overlap with DL/UL control of 240, 480 and 960kHz SCS. This advantageously allows this subset of SCS (240, 480 and 960 kHz) to be used for SS/PBCH and control/data without overlapping or limiting DL/UL control opportunities due to SS/PBCH transmissions.

For 960kHz SCS, candidate locations for the first design D1-960 of FIG. 5 are:

·D1_960＝{8,20,32,44}+56*n

n=0, 1,2,..15 (to yield 64 beams)

For the unlicensed case, n is from 0 to 79, providing 320 SS/PBCH candidate locations. This would require a 9 bit indication to indicate SS/PBCH candidate locations. To cover the overhead, only the first 256 candidate positions may be allowed, which may be indicated using 8-bit signaling.

The second design (D2-960) of fig. 5 ensures that there is no overlap of DL/control opportunities starting from the control/data SCS of 60kHz, at the cost of reduced SS/PBCH density per unit time. This design overlaps with DL/UL control zero for all SCS from 60kHz to 960 kHz. Therefore, if all SCSs are considered necessary for DL/UL control, this may be a good choice.

For 960kHz SCS, the candidate locations for the second design D2-960 of FIG. 5 are:

·D2_960＝{32,44,64,76,88,128,144,156,176,188}+224*n

·n＝0,1,2,...,6

where for n=6, the first 4 candidate positions are used.

For the unlicensed case, n is from 0 to 19, providing 200 SS/PBCH candidate locations. This would require an 8 bit indication to indicate SS/PBCH candidate locations.

When the data/control SCS is 240KHz or greater, the reader will recognize that the design of D1_480 and D1_960 have been optimized for construction. These designs may be suitable to limit system operation for control and data to the case of SCS of 240KHz or greater. The other two designs d2_480 and d2_960 of these SCSs reduce the SS/PBCH density in time, but allow operation in any SCS starting from 60KHz, thus there is no limitation on the use of data/control SCS.

As noted above, the terms "beam index" and "SS/PBCH block candidate location index" are used synonymously herein. The objective of the following disclosure is to transmit an index of each SS/PBCH candidate location so that a UE decoding each SS/PBCH block can determine the SS/PBCH candidate location in an SS/PBCH burst. Based on this determined location, the UE may determine complete system timing information by combining the location with the SFN and field flags. As described above, various SS/PBCH burst designs are proposed that increase the number of candidate locations, thus allowing for channel access uncertainty. This may increase the size of the SS/PBCH candidate location index.

For example, for the case where the maximum number of beams is 64 (6 bits of SS/PBCH candidate index indication are required), the proposed design for 120kHz SCS increases the number of possible candidate locations to 80, which requires 7 bits of indication. In all SS/PBCH burst designs above for 120kHz SCS to 960kHz SCS, an indication of 7, 8 or 9 bits is required. In the conventional design of PBCH, 3 LSBs are carried in the PBCH DMRS and 3 MSBs are carried in the PBCH payload, which are generated and added by the physical layer. The following disclosure discusses a method of communicating SS/PBCH candidate locations, which may be particularly suitable for burst design as discussed above.

The indication of the location may be provided by the payload of the PBCH. Additional bits of the SS/PBCH candidate index may be added to the PBCH payload as the MSB is added to the PBCH payload. This increases the size of the physical layer generated PBCH payload from 8 bits to 9, 10 or 11 bits, i.e. by 1, 2 or 3 bits, respectively. Although adding additional bits is technically simple, the processing of the physical layer must be modified. In conventional designs, an 8-bit PBCH payload would be added to a 24-bit MIB payload, so that there would be a 32-bit combined payload, on which the physical layer is processed and applied. If the number of bits increases above 32, many aspects of physical layer processing, such as scrambling, CRC addition, interleaving, etc., may require extensive redesign, which may be unattractive due to the high complexity.

To avoid an increase in payload size, reserved bits of the MIB payload may be utilized to add one bit to the candidate location index indication. The size of the candidate location index can thus be increased by 1 bit (from 64 locations to 128 locations) without increasing the data to be transferred or redesigning the physical layer processing. This can be achieved by limiting the use of up to 128 candidate locations in the design, which in practice can accommodate more than 128 locations.

In another example, the PBCH DMRS may be used to indicate SS/PBCH candidate indexes. In conventional designs, 3 LSBs of the SS/PBCH candidate index are carried by the PBCH DMRS by selecting 8 possible DMRS sequences. The number of DMRS sequences may be increased to the required number to transmit additional bits of the SS/PBCH candidate index. For example, 16 or 32 DMRS sequences may be used to accommodate 1 or 2 additional bits of the SS/PBCH candidate index, respectively. For this strategy, it is not necessary to increase the number of DMRS sequences to 32 for all SCS. In practice, to avoid the blind decoding of DMRS sequences by the UE becoming too complex, only the SS/PBCH candidate location indication requires 8-bit SCS to use 32 sequences. The PBSCH DMRS of the remaining DMRS sequences may use only 16 DMRS sequences.

In the SS/PBCH burst designs set forth above, the 120kHz and 240kHz designs require only 7 bits for SS/PBCH candidate location indication, while the 480kHz and 960kHz SCS designs require more than 7 bits. Thus, a base station transmitting SS/PBCH blocks at 120kHz or 240kHz SCS will use only 16 PBCH DMRS sequences, while more PBCH DMRS sequences are used for 480kHz and 960kHz SCS.

For designs that can accommodate more than 128 locations in one SS/PBCH burst, a tradeoff can be achieved by limiting the maximum number of SS/PBCH candidate locations to the first 128 locations. This makes it possible to uniformly use 7-bit indications of SS/PBCH block positions, which can be achieved by increasing the number of possible DMRS sequences to 16. This may be a good tradeoff of additional timing flexibility and limited increased DMRS decoding complexity.

For the 6-bit SS/PBCH candidate location indication denoted b0 to b5, bits b0 to b2 are transmitted on the PBCH DMRS and bits b3 to b5 are transmitted on the PBCH payload in the conventional design. In the case of 7-bit SS/PBCH candidate location indications (denoted b0 through b 6), one approach is to use conventional bit mapping for the first 6 bits and add the MSB (i.e., b 6) to the indication provided by the DMRS sequence. This means that the DMRS will carry 4 bits (b 0 to b2 and b 6), while the PBCH payload will carry b3 to b5. One possible disadvantage of this design is that neighboring SS/PBCH candidate locations will use the same PBCH DMRS, thereby affecting the quality of detection. To overcome this problem, 4 LSBs, i.e., bits b0 to b3, are mapped to the PBCH DMRS and may be transmitted through 16 possible PBCH DMRS sequences, while 3 MSBs, i.e., b4 to b6, may be added to the PBCH payload.

If more than 1 bit needs to be added to the existing SS/PBCH candidate location indication of 6 bits, a hybrid scheme of the above two methods may be employed in which DMRS indication and payload indication are used simultaneously such that the number of bits transmitted increases by more than 3. For example, if an SS/PBCH location index supporting 8 bits is required, two additional bits need to be transmitted as compared to the conventional 6-bit design. 1 additional bit may be transmitted on the PBCH as a payload (using the techniques described above), and 1 bit may be transmitted by increasing the number of DMRS sequences to 16 (using the techniques described above). In addition, this hybrid scheme can accommodate a greater number of SS/PBCH candidate locations.

The discussion above of proposed SS/PBCH block designs is primarily in the context of unlicensed spectrum, as channel sensing is to be done at the beam switching instant, but the reader will appreciate that these designs can also be applied seamlessly to licensed spectrum. This facilitates unified adoption of the same SS/PBCH burst design for licensed and unlicensed spectrum. Another advantage is that the designs presented herein help to better digest transients caused by beam switching transients, which might otherwise degrade the quality of the continuously transmitted SS/PBCH blocks.

The scheme discussed above may replace existing designs for licensed spectrum for 120KHz and 240KHz SCS, or the proposed scheme may be used only for unlicensed shared spectrum. The devices know whether they are operating in licensed or unlicensed spectrum and can therefore use the appropriate scheme without creating a mix.

Various methods are presented herein to indicate the number of increased SS/PBCH block candidate locations in an SS/PBCH burst. The problem of additional SS/PBCH candidate locations is mainly set in the context of unlicensed shared spectrum to accommodate more locations than the maximum number of beams to compensate for the uncertainty of channel access. This design may be seamlessly applicable if the number of beams in the licensed or unlicensed spectrum increases to more than 64, requiring SS/PBCH candidate locations containing more than 6 bits.

Release 15 of 3GPP NR has limited the length of the burst to a half frame period, i.e. 5 milliseconds. This basically means that all candidate positions for a given frequency range always match this 5 millisecond period. The design presented herein provides a symbol position starting with reference symbol 0. Consistent with existing designs, this reference symbol 0 is considered the first symbol of a field. Nevertheless, for higher frequency operations, the symbol time will become very small with the use of very large SCS. This may result in a burst length changing from 5 milliseconds to a smaller time interval. The proposed design is still valid even if the burst length is changed to a different time length. Symbol 0 (reference point) in the proposed design needs to be mapped to a new reference symbol as a minor adjustment to achieve a design suitable for any new burst time length. Changes in burst time length may also affect the total number of candidate locations for the unlicensed spectrum carrier.

The proposed design provides 64 candidate locations, and currently 3GPP has decided to support up to 64 beams in FR2 and FR2 extensions up to 71 GHz. The reader will appreciate that the proposed SS/PBCH burst design can be easily adapted to achieve a smaller or greater number of SS/PBCH candidate locations. While the first 32 or 16 candidate positions in the proposed design may be used in order to achieve a smaller number of beam positions, such as 32 or 16. To achieve a design with a number of more than 64 beams, ultimately using more SS/PBCH block locations, additional locations may multiplex the proposed design to obtain the desired number of candidate locations.

It is apparent that the above disclosure includes methods for a base station to transmit the signals discussed herein on an appropriate beam for reception by a UE. For example, the disclosure includes the steps of: transmitting a synchronization signal at a first candidate location on a first beam, switching to a second beam and performing a channel access procedure for the second beam, and then transmitting a second synchronization signal at a second candidate location on the second beam.

Although not shown in detail, any device or means forming part of the network may comprise at least a processor, a memory unit and a communication interface, wherein the processor unit, the memory unit and the communication interface are configured to perform the method of any aspect of the invention. Further options and choices are described below.

The signal processing functions of embodiments of the present invention, particularly the gNB and the UE, may be implemented using computing systems or architectures known to those skilled in the relevant art. Computing systems such as desktop, laptop or notebook computers, hand-held computing devices (PDAs, cell phones, palmtop computers, etc.), mainframes, servers, clients, or any other type of special or general purpose computing device as may be desired or appropriate for a given application or environment may be used. The computing system may include one or more processors, which may be implemented using a general-purpose or special-purpose processing engine (e.g., microprocessor, microcontroller, or other control module).

The computing system may also include a main memory, such as Random Access Memory (RAM) or other dynamic memory, for storing instructions and information to be executed by the processor. Such main memory may also be used for storing temporary variables and other intermediate information to be executed by the processor during execution of instructions. The computing system similarly may include a Read Only Memory (ROM) or other static storage device for storing static information and instructions for the processor.

The computing system may also include an information storage system, which may include, for example, a media drive and a removable storage interface. The media drive may include a drive or other mechanism to support fixed or removable storage media, such as a hard disk drive, floppy disk drive, magnetic tape drive, optical disk drive, compact Disk (CD) or Digital Video Drive (DVD) read or write drive (R or RW), or other removable or fixed media drive. Storage media may include, for example, hard disk, floppy disk, magnetic tape, optical disk, CD or DVD, or other fixed or removable medium that is read by and written to by media drives. The storage medium may include a computer-readable storage medium having particular computer software or data stored therein.

In alternative embodiments, the information storage system may include other similar components for allowing computer programs or other instructions or data to be loaded into the computing system. Such components may include, for example, removable storage units and interfaces such as program cartridges and cartridge interfaces, removable memory (e.g., flash memory or other removable memory modules) and memory slots, and other removable storage units and interfaces that allow software and data to be transferred from the removable storage unit to the computing system.

The computing system may also include a communication interface. Such a communication interface may be used to allow software and data to be transferred between the computing system and external devices. Examples of communication interfaces may include modems, network interfaces (such as ethernet or other NIC cards), communication ports (such as, for example, universal Serial Bus (USB) ports), PCMCIA slots and cards, and so forth. Software and data transferred via the communications interface are in the form of signals which may be electronic, electromagnetic and optical or other signals capable of being received by the communications interface medium.

In this document, the terms "computer program product," "computer-readable medium," and the like may be used to generally refer to tangible media, such as memory, storage devices, or storage units. These and other forms of computer-readable media may store one or more instructions for use by a processor, including a computer system, to cause the processor to perform specified operations. Such instructions, generally referred to as "computer program code" (which may be grouped in the form of computer programs or other groupings), when executed, enable the computing system to perform functions of embodiments of the present invention. Note that the code may directly cause the processor to perform the specified operations, be compiled to do so, and/or be combined with other software, hardware, and/or firmware elements (e.g., libraries for performing standard functions) to do so.

The non-transitory computer readable medium may include at least one of the group consisting of: hard disks, CD-ROMs, optical storage devices, magnetic storage devices, read-only memory, programmable read-only memory, erasable programmable read-only memory, electrically erasable programmable read-only memory, and flash memory. In embodiments where the elements are implemented using software, the software may be stored in a computer readable medium and loaded into a computing system using, for example, a removable storage drive. The control modules (in this example, software instructions or executable computer program code) when executed by a processor in a computer system cause the processor to perform the functions of the invention as described herein.

Furthermore, the inventive concept may be applied to any circuit for performing signal processing functions within a network element. It is further envisioned that a semiconductor manufacturer may utilize the inventive concepts in designing stand-alone devices such as Application Specific Integrated Circuits (ASICs) or microcontrollers of Digital Signal Processors (DSPs) and/or any other subsystem elements, for example.

It will be appreciated that the above description has described embodiments of the invention with reference to a single processing logic for clarity. However, the inventive concept may equally be implemented by a number of different functional units and processors to provide signal processing functionality. Thus, references to specific functional units are only to be seen as references to suitable means for providing the described functionality rather than indicative of a strict logical or physical structure or organization.

Aspects of the invention may be implemented in any suitable form including hardware, software, firmware or any combination of these. The invention may alternatively be implemented at least in part as computer software running on one or more data processors and/or digital signal processors or as a configurable module component such as an FPGA device.

Thus, the elements and components of an embodiment of the invention may be physically, functionally and logically implemented in any suitable way. Indeed the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units. Although the present invention has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the invention is limited only by the appended claims. Furthermore, while certain features have been described in connection with specific embodiments, those skilled in the art will recognize that different features of the described embodiments may be combined in accordance with the invention. In the claims, the term "comprising" does not exclude the presence of other elements or steps.

Furthermore, although individually listed, a plurality of means, elements or method steps may be implemented by e.g. a single unit or processor. Furthermore, although individual features may be included in different claims, these may possibly be advantageously combined, and the inclusion in different claims does not imply that a combination of features is not feasible and/or advantageous. Moreover, the inclusion of a feature in one category of claims does not imply a limitation to this category but rather indicates that the feature is equally applicable to other claim categories as appropriate.

Furthermore, the order of features in the claims does not imply any specific order in which the features must be performed and in particular the order of individual steps in a method claim does not imply that the steps must be performed in that order. Rather, the steps may be performed in any suitable order. Furthermore, singular references do not exclude a plurality. Thus, references to "a," "an," "the first," "the second," etc. do not exclude a plurality.

Although the present invention has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the invention is limited only by the appended claims. Furthermore, while certain features have been described in connection with specific embodiments, those skilled in the art will recognize that different features of the described embodiments may be combined in accordance with the invention. In the claims, the term "comprising" does not exclude the presence of other elements.

Claims (22)

1. A method of transmitting SS/PBCH bursts in an OFDM transmission system operating in frequency range 2 (FR 2) and utilizing beam scanning techniques, the method comprising the steps of: selecting a plurality of starting positions to transmit the SS/PBCH burst, wherein the plurality of starting positions are selected so that a gap of at least one OFDM symbol exists between adjacent SS/PBCH bursts; and transmitting a plurality of SS/PBCH bursts, wherein each SS/PBCH burst begins at one of the selected plurality of starting locations.

2. The method of claim 1, wherein the system uses a subcarrier spacing of 120 kHz.

3. The method of claim 2, wherein the plurality of start positions are set at OFDM symbol number {4,9,15,20} +28 x n, where n = 0,1,..15, reference symbol index 0 corresponding to a first symbol of a first slot in a field transmitting an SS/PBCH block.

4. The method of claim 2, wherein the plurality of start positions are set at OFDM symbol number {2,8,15,20} +28 x n, where n = 0,1,..15, reference symbol index 0 corresponding to a first symbol of a first slot in a field transmitting an SS/PBCH block.

5. The method of claim 2, wherein the plurality of start positions are set at OFDM symbol number 4,9,15,20 +28 x n, where n = 0,1,2,..19, reference symbol index 0 corresponding to a first symbol of a first slot in a field transmitting an SS/PBCH block.

6. The method of claim 1, wherein the system uses a subcarrier spacing of 240 kHz.

7. The method of claim 6, wherein the plurality of start positions are set at OFDM symbol number {8,14,20,32,38,44} +56 x n, where n = 0,1,2,..10, reference symbol index 0 corresponding to a first symbol of a first slot in a field transmitting an SS/PBCH block.

8. The method of claim 6, wherein the plurality of start positions are set at OFDM symbol number {8,14,20,32,38,44} +56 x n, where n = 0,1,2,..19, reference symbol index 0 corresponding to a first symbol of a first slot in a field transmitting an SS/PBCH block.

9. The method of claim 6, wherein the plurality of start positions are set at OFDM symbol number {8,16,32,44} +56 x n, where n = 0,1,2,..15, reference symbol index 0 corresponding to a first symbol of a first slot in a field transmitting an SS/PBCH block.

10. The method of claim 6, wherein the plurality of start positions are set at OFDM symbol number {8,16,32,44} +56 x n, where n = 0,1,2,..19, reference symbol index 0 corresponding to a first symbol of a first slot in a field transmitting an SS/PBCH block.

11. The method of claim 1, wherein the system uses a subcarrier spacing of 480 kHz.

12. The method of claim 11, wherein the plurality of start positions are set at OFDM symbol number {4,12,20} +28 x n, where n = 0,1,2,..21, reference symbol index 0 corresponding to a first symbol of a first slot in a field transmitting an SS/PBCH block.

13. The method of claim 11, wherein the plurality of start positions are set at OFDM symbol number 16,32,40,64,72,88 +112, where n = 0,1,2,..10, reference symbol index 0 corresponding to a first symbol of a first slot in a field transmitting an SS/PBCH block.

14. The method of claim 1, wherein the system uses a subcarrier spacing of 960 kHz.

15. The method of claim 14, wherein the plurality of start positions are set at OFDM symbol number 8,20,32,44} +56 x n, where n = 0,1,2,..15, reference symbol index 0 corresponding to a first symbol of a first slot in a field transmitting an SS/PBCH block.

16. The method of claim 14, wherein the plurality of start positions are set at OFDM symbol number 32,44,64,76,88,128,144,156,176,188 +224 x n, where n = 0,1,2,..6, reference symbol index 0 corresponding to a first symbol of a first slot in a field transmitting an SS/PBCH block.

17. A method as claimed in any one of the preceding claims, further comprising the step of transmitting an indication of the plurality of start positions.

18. The method of claim 17, wherein the plurality of starting locations are transmitted with a payload of a PBCH.

19. The method of claim 18, wherein reserved bits of MIB payload are used as part of the indication of the plurality of starting positions.

20. The method of any one of claims 17 to 19, wherein the number of the plurality of starting positions is not more than 128.

21. The method of any one of claims 17 to 20, wherein PBCH DMRS indicates at least a portion of the plurality of starting positions.

22. The method of any of claims 17 to 21, wherein the plurality of start positions are indicated by SS/PBCH candidate indexes.

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