WO2018148866A1

WO2018148866A1 - False alarm rate suppression for polar codes

Info

Publication number: WO2018148866A1
Application number: PCT/CN2017/073488
Authority: WO
Inventors: Gaojin Wu; Changlong Xu; Chao Wei; Jilei Hou
Original assignee: Qualcomm Incorporated
Priority date: 2017-02-14
Filing date: 2017-02-14
Publication date: 2018-08-23

Abstract

Methods, systems, and devices for wireless communication are described for false alarm rate suppression for polar codes. A list decoder may determine a path metric for each of multiple paths through a code tree for decoding a polar-encoded codeword, wherein a portion of each of the path metrics corresponds to at least one frozen bit in the polar-encoded codeword. A false alarm suppressor may determine a modified path metric for each of the paths by excluding the respective portion corresponding to the at least one frozen bit and determine a check metric for at least one of the paths based at least in part on the modified path metrics. An error detector may perform an error detecting algorithm on a bit sequence corresponding to the at least one of the plurality of paths based at least in part on the check metric satisfying a threshold.

Description

FALSE ALARM RATE SUPPRESSION FOR POLAR CODES

BACKGROUND

The following relates generally to wireless communication, and more specifically to false alarm rate suppression for polar codes.

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 code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, and orthogonal frequency division multiple access (OFDMA) systems, (e.g.， a Long Term Evolution (LTE) system, or a New Radio (NR) system) . A wireless multiple-access communications system may include a number of base stations or access network nodes, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE) .

Data transmission, however, often involves sending data over a noisy communication channel. To combat noise, a transmitter may encode code blocks using error correcting codes that introduce redundancy in the code block so that transmission errors may be detected and corrected. Some examples of encoding algorithms with error correcting codes include convolutional codes (CCs) , low-density parity-check (LDPC) codes, and polar codes. A polar code is an example of a linear block error correcting code and is the first coding technique to provably achieve channel capacity. Even when using error correcting codes, false alarms remain an issue when transmitting over a noisy communication channel. A false alarm may occur when a receiver decodes a received signal to determine that a particular bit sequence was transmitted, when a different bit sequence or no bit sequence was actually sent. Existing implementations do not adequately address false alarm rates.

SUMMARY

The described techniques relate to improved methods, systems, devices, or apparatuses that support false alarm rate suppression for polar codes. Generally, the described techniques provide for generating a check metric that is a function of path metrics of a list decoder that have been modified for determining whether to perform error detection. In an example, a receiver, such as a base station or UE, may include a list decoder, a false alarm suppressor, and an error detector. During decoding of a polar-encoded codeword, the list decoder may identify a list size number of paths through a code tree as candidate paths based at least in part on respective path metrics for each of the paths. A false alarm suppressor may generate modified path metrics by excluding a contribution to the path metrics of frozen bits, and may find a minimum of the modified path metrics. The false alarm suppressor may generate a check metric that is a function of the minimum modified path metric and a statistical value of the modified path metrics. The false alarm suppressor may compare the check metric to a threshold and determine whether to pass a bit sequence associated with a candidate path to an error detector. Beneficially, the examples described herein may suppress false alarms and are robust to signal to noise (SNR) variations.

A method of wireless communication is described. The method may include determining a path metric for each of a plurality of paths through a code tree for decoding a polar-encoded codeword, wherein a portion of each of the path metrics corresponds to at least one frozen bit in the polar-encoded codeword, determining a modified path metric for each of the plurality of paths by excluding the respective portion corresponding to the at least one frozen bit in each of the plurality of paths, determining a check metric for at least one of the plurality of paths based at least in part on the modified path metrics, and performing an error detecting algorithm on a bit sequence corresponding to the at least one of the plurality of paths based at least in part on the check metric satisfying a threshold.

An apparatus for wireless communication is described. The apparatus may include means for determining a path metric for each of a plurality of paths through a code tree for decoding a polar-encoded codeword, wherein a portion of each of the path metrics corresponds to at least one frozen bit in the polar-encoded codeword, means for determining a modified path metric for each of the plurality of paths by excluding the respective portion corresponding to the at least one frozen bit in each of the plurality of paths, means for determining a check metric for at least one of the plurality of paths based at least in part on the modified path metrics, and means for performing an error detecting algorithm on a bit sequence corresponding to the at least one of the plurality of paths based at least in part on the check metric satisfying a threshold.

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 operable to cause the processor to determine a path metric for each of a plurality of paths through a code tree for decoding a polar-encoded codeword, wherein a portion of each of the path metrics corresponds to at least one frozen bit in the polar-encoded codeword, determine a modified path metric for each of the plurality of paths by excluding the respective portion corresponding to the at least one frozen bit in each of the plurality of paths, determine a check metric for at least one of the plurality of paths based at least in part on the modified path metrics, and perform an error detecting algorithm on a bit sequence corresponding to the at least one of the plurality of paths based at least in part on the check metric satisfying a threshold.

A non-transitory computer readable medium for wireless communication is described. The non-transitory computer-readable medium may include instructions operable to cause a processor to determine a path metric for each of a plurality of paths through a code tree for decoding a polar-encoded codeword, wherein a portion of each of the path metrics corresponds to at least one frozen bit in the polar-encoded codeword, determine a modified path metric for each of the plurality of paths by excluding the respective portion corresponding to the at least one frozen bit in each of the plurality of paths, determine a check metric for at least one of the plurality of paths based at least in part on the modified path metrics, and perform an error detecting algorithm on a bit sequence corresponding to the at least one of the plurality of paths based at least in part on the check metric satisfying a threshold.

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 minimum modified path metric and a statistical value of the modified path metrics. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the check metric may be a function of the minimum modified path metric and the statistical value. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the function may be a difference between a constant and a ratio of the minimum modified path metric and the statistical value. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the statistical value of the modified path metrics excludes the minimum modified path metric.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the bit sequence includes at least one information bit.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the at least one of the plurality of paths corresponds to a particular path of the plurality of paths that may have a minimum of the path metrics. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the at least one of the plurality of paths corresponds to a particular path of the plurality of paths that may have a minimum of the modified path metrics.

Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for performing a successive cancellation list (SCL) decoding algorithm for determining the plurality of paths through the code tree, wherein the plurality of paths may be a subset of possible paths through the code tree.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, each of the path metrics may be an accumulation of cost values for traversing a respective one of the plurality of paths, and wherein each of the cost values represent a cost for moving from one node to another node along the respective path in the code tree. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, each of the cost values may be a function of a logarithmic-likelihood ratio, a probability, or a combination thereof.

In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the error detecting algorithm may be a cyclic redundancy check (CRC) algorithm. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the threshold may be a function of a false alarm rate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a system for wireless communication that supports false alarm rate suppression for polar codes in accordance with aspects of the present disclosure.

FIG. 2 illustrates an example of a wireless communication system that supports false alarm rate suppression for polar codes in accordance with aspects of the present disclosure.

FIG. 3 illustrates an example diagram of a decoder that supports false alarm rate suppression for polar codes in accordance with aspects of the present disclosure.

FIG. 4 illustrates an example of a flow diagram that supports false alarm rate suppression for polar codes in accordance with aspects of the present disclosure.

FIG. 5 illustrates an example diagram of a code tree that supports false alarm rate suppression for polar codes in accordance with aspects of the present disclosure.

FIG. 6 illustrates an example diagram of a code tree that supports false alarm rate suppression for polar codes in accordance with aspects of the present disclosure.

FIG. 7 illustrates an example diagram of a code tree that supports false alarm rate suppression for polar codes in accordance with aspects of the present disclosure.

FIGs. 8 through 10 show block diagrams of a device that supports false alarm rate suppression for polar codes in accordance with aspects of the present disclosure.

FIG. 11 illustrates a block diagram of a system including a UE that supports false alarm rate suppression for polar codes in accordance with aspects of the present disclosure.

FIG. 12 illustrates a block diagram of a system including a base station that supports false alarm rate suppression for polar codes in accordance with aspects of the present disclosure.

FIGs. 13 through 14 illustrate methods for false alarm rate suppression for polar codes in accordance with aspects of the present disclosure.

DETAILED DESCRIPTION

The described techniques relate to improved methods, systems, devices, or apparatuses that support false alarm rate suppression for polar codes. Generally, the described techniques provide for calculating a check metric that is a function of modified path metrics for suppressing a false alarm rate.

A polar code is a linear block error correcting code that can achieve channel capacity. Polar encoding may be used as a coding scheme for a control channel, such as an enhanced mobile broadband (eMBB) control channel. Polar code construction is based on multiple recursive concatenation of a kernel code which transforms physical channels into sub-channels. Sub-channels either have high reliability or low reliability. Sub-channels with high reliability are chosen to transmit information bits while low reliability sub-channels transmit frozen bits (e.g.， are set to zero by default) . Selected subsets of the low reliability sub-channels may be used to transmit parity bits. A parity bit may be a bit added to a bit sequence to ensure that a total number of bits in the bit sequence, or portion of the bit sequence, is even or odd (e.g.， total number of ‘1’ bits in the bit sequence is even or odd) . A parity check function at a receiver may use parity bits for error correction and error detection. For instance, a decoder at the receiver performing a list decoding process may use the parity bits to prune paths from a code tree. Only the paths through the code tree that satisfy the parity check function are kept, and the rest are eliminated. A well-constructed parity check polar code increases its minimum-coding-distance, thereby improving code performance.

Regardless of the coding technique used, false alarms are a possibility and are harmful to a communication system. A false alarm occurs when a receiver decodes a received signal to determine that a particular bit sequence was transmitted, when a different bit sequence or no bit sequence was actually sent. For example, a false alarm may occur when a receiver incorrectly detects a control channel, though a control message on that channel is not intended for this UE, or no control message was sent on that channel.

Cyclic redundancy check (CRC) bits may be used to suppress false alarms. For instance, a conventional transmitter may append a cyclic redundancy check (CRC) to information bits in a message being transmitted. A receiver uses the CRC for detecting an error in a received message, thereby lowering a false alarm rate (FAR) . The ability of the CRC to suppress false alarms is a function of the number of bits in the CRC. In some instances, the FAR is function of the number of CRC bits (e.g.，

) . In LTE, a 16-bit CRC is used in downlink control and 8-bit CRC is used in uplink control. False alarm suppression capability increases with CRC length. In spite of CRC’s simplicity and efficiency, CRC bits are overhead to information bits being transmitted. If the same throughput is required, more information subchannels are occupied due to CRC bits.

Parity check bits are another technique for detecting errors. Parity check bits establish correlation across information bits and this correlation may be used to detect errors. If an error happens at one or more information bits, a correlation function at the receiver would use the parity check bits to detect the error due to a parity violation and to penalize a path metric of a successive cancellation list (SCL) decoder. Other techniques can suppress a false alarm rate to some extent. For example, a path metric of a SCL decoder can suppress the false alarm rate.

Conventional FAR techniques are problematic for a number of reasons. For instance, a conventional receiver that includes a non-list decoder, such as a maximum likelihood (ML) decoder, has a certain FAR and a certain block error rate (BLER) . Non-list decoders, however, consider every possible path through a code tree and hence are very computationally expensive to implement. In contrast, list decoders only consider selected paths through a code tree and thus are less computationally expensive to implement. List decoders can also reduce the BLER by way of checking more paths, but also increase the FAR.

In some cases, conventional list decoders output respective path metrics for a list size number of candidate paths and compare a minimum of the respective path metrics to a threshold attempting to decrease the FAR. If the minimum path metric is less than the threshold, then a CRC check is performed on bit sequences corresponding to the candidate paths. Otherwise, the candidate paths are discarded. Using a minimum path metric in this manner has many shortcomings. First, it is not easy to determine an appropriate threshold for comparison to the minimum path metric. A threshold that is too conservative suppresses the FAR but identifies too many possibly good paths as decoding errors. Further, setting the threshold to simultaneously achieve an acceptable FAR and BLER is nearly impossible when the transmitter is not transmitting (e.g.， no control message is sent in a control channel) or requires a receiver to perform blind detection of a control signal format. Often, a control signal format is unknown at the receiver and thus the receiver is required to do blind detection for all possible K lengths of information bits. Moreover, the minimum path metric is sensitive to many factors that are unrelated to the FAR. These factors may include a signal to noise ratio, number of information bits, number of parity bits, and the like. The sensitivity of the minimum path metric value to factors unrelated to the FAR makes it ineffective for controlling the FAR in many scenarios.

The examples described herein overcome the problems with conventional systems by calculating a check metric that is a function of modified path metrics for suppressing a false alarm rate. In an example, a receiver, such as a base station or UE, may include a list decoder, a false alarm suppressor, and an error detector. During decoding of a polar-encoded codeword, the list decoder may identify a list size number of paths through a code tree as candidate paths based at least in part on respective path metrics for each of the paths. A false alarm suppressor may generate modified path metrics by excluding a contribution of frozen bits to the path metrics, and may find a minimum of the modified path metrics. The false alarm suppressor may generate a check metric that is a function of the minimum modified path metric and a statistical value of the modified path metrics. The false alarm suppressor may compare the check metric to a threshold and determine whether to pass a bit sequence of a candidate path associated with the modified or unmodified path metric to an error detector for error checking. Beneficially, the examples described herein may suppress false alarm rates and are robust to SNR variations.

Aspects of the disclosure are initially described in the context of a wireless communications system. The wireless communication system may calculate a check metric that is a function of modified path metrics of a list decoder for suppressing a false alarm rate. Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to false alarm rate suppression for polar codes.

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 LTE (or LTE-Advanced) network, or a New Radio (NR) network. In some cases, wireless communications system 100 may support enhanced broadband communications, ultra-reliable (i.e., mission critical) communications, low latency communications, and communications with low-cost and low-complexity devices.

Transmitters, such as base stations 105 and UEs 115, may apply an error detection algorithm to information bits to generate an error detection code and may generate a payload that includes the error detection code appended to the information bits. A transmitter may perform a polar encoding algorithm on the payload to generate a polar-encoded codeword that is transmitted via a communication channel. The polar-encoded codeword may include information bits, frozen bits, parity check bits, and any combination thereof. In polar encoding, sub-channels with high reliability may be chosen to transmit the information bits and sub-channels with lower reliability may be chosen to transmit the frozen bits (e.g., set to zero by default) . In some examples, the transmitter may select a subset of the frozen bit sub- channels as parity check frozen sub-channels to transmit the parity check bits instead of frozen bits.

Receivers, such as base stations 105 and UEs 115, may receive a signal that includes the polar-encoded codeword, and perform a list decoding algorithm to generate a list size number of candidate paths through a code tree and a path metric for each candidate path. If parity check bits are part of the polar-encoded codeword, the receiver may apply a parity check function using the parity check bits as part of the list decoding algorithm for pruning paths through the code tree. The receiver may determine modified path metrics for the candidate paths that exclude from the respective path metrics the contribution of frozen bits (and optionally the contribution of the parity check bits) . The receiver may generate a check metric that is a function of the modified path metrics. The receiver may compare the check metric to a threshold for determining whether to pass a bit sequence corresponding to a particular one of the candidate paths to an error detector. The threshold may be used to identify false alarm risk and the particular candidate path may be discarded if the threshold is not satisfied. Beneficially, the examples described herein may suppress false alarms and may be robust to SNR variations.

In some instances, the base station 105 may be the transmitter and the UE 115 may be the receiver. In other instances, the UE 115 may be the transmitter and the base station 105 may be the receiver. In further instances, a first base station 105 may be the transmitter and a second base station 105 may be the receiver. In additional instances, a first UE 115 may be the transmitter and a second UE 115 may be the receiver. Devices other than a base station and a receiver may also be one or both of the transmitter and receiver.

Base stations 105 may wirelessly communicate with UEs 115 via one or more base station antennas. Each base station 105 may provide communication coverage for a respective geographic coverage area 110. Communication links 125 shown in wireless communications system 100 may include uplink (UL) transmissions from a UE 115 to a base station 105, or downlink (DL) transmissions, from a base station 105 to a UE 115. Control information and data may be multiplexed on an uplink channel or downlink according to various techniques. Control information and data may be multiplexed on a downlink channel, for example, using time division multiplexing (TDM) techniques, frequency division multiplexing (FDM) techniques, or hybrid TDM-FDM techniques. In some examples, the control information transmitted during a TTI of a downlink channel may be distributed between different control regions in a cascaded manner (e.g.， between a common control region and one or more UE-specific control regions) .

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 station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology. A UE 115 may also be a cellular phone, a personal digital assistant (PDA) , a wireless modem, a wireless communication device, a handheld device, a tablet computer, a laptop computer, a cordless phone, a personal electronic device, a handheld device, a personal computer, a wireless local loop (WLL) station, an Internet of things (IoT) device, an Internet of Everything (IoE) device, a machine type communication (MTC) device, an appliance, an automobile, or the like.

In some cases, a UE 115 may also be able to communicate directly with other UEs (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 coverage area 110 of a cell. Other UEs 115 in such a group may be outside the coverage area 110 of a cell, or 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 independent of a base station 105.

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, i.e., Machine-to-Machine (M2M) communication. M2M or MTC may refer to data communication technologies that allow devices to communicate with one another or a base station without human intervention. For example, M2M or MTC may refer to 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.

In some cases, an MTC device may operate using half-duplex (one-way) communications at a reduced peak rate. MTC devices may also be configured to enter a power saving "deep sleep" mode when not engaging in active communications. In some cases, MTC or IoT devices may be designed to support mission critical functions and wireless communications system may be configured to provide ultra-reliable communications for these functions.

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.， S1, etc. ) . Base stations 105 may communicate with one another over backhaul links 134 (e.g.， X2, etc. ) either directly or indirectly (e.g.， through core network 130) . Base stations 105 may perform radio configuration and scheduling for communication with UEs 115, or may operate under the control of a base station controller (not shown) . In some examples, base stations 105 may be macro cells, small cells, hot spots, or the like. Base stations 105 may also be referred to as eNodeBs (eNBs) 105.

A base station 105 may be connected by an S1 interface to the core network 130. The core network may be an evolved packet core (EPC) , which may include at least one MME, at least one S-GW, and at least one P-GW. The MME may be the control node that processes the signaling between the UE 115 and the EPC. All 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 the Internet, the Intranet, an IP Multimedia Subsystem (IMS) , and a Packet-Switched (PS) Streaming Service (PSS) .

The core network 130 may provide user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. At least some of the network devices, such as base station 105-a 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 a number of UEs 115 through a number of other access network transmission entities, each of which may be an example of 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 in an ultra high frequency (UHF) frequency region using frequency bands from 700 MHz to 2600 MHz (2.6 GHz) , although in some cases WLAN networks may use frequencies as high as 4 GHz. This region may also be known as the decimeter band, since the wavelengths range from approximately one decimeter to one meter in length. UHF waves may propagate mainly by line of sight, and may be blocked by buildings and environmental features. However, the waves may penetrate walls sufficiently to provide service to UEs 115 located indoors. Transmission of UHF waves is characterized by 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. In some cases, wireless communications system 100 may also utilize extremely high frequency (EHF) portions of the spectrum (e.g., from 30 GHz to 300 GHz) . This region may also be known as the millimeter band, since the wavelengths range from approximately one millimeter to one centimeter in length. Thus, EHF antennas 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 (e.g.， for directional beamforming) . However, EHF transmissions may be subject to even greater atmospheric attenuation and shorter range than UHF transmissions.

Thus, wireless communications system 100 may support millimeter wave (mmW) communications between UEs 115 and base stations 105. Devices operating in mmW or EHF bands may have multiple antennas to allow beamforming. That is, a base station 105 may use multiple antennas or antenna arrays to conduct beamforming operations for directional communications with a UE 115. Beamforming (which may also be referred to as spatial filtering or directional transmission) is a signal processing technique that may be used at a transmitter (e.g. a base station 105) to shape and/or steer an overall antenna beam in the direction of a target receiver (e.g. a UE 115) . This may be achieved by combining elements in an antenna array in such a way that transmitted signals at particular angles experience constructive interference while others experience destructive interference.

Multiple-input multiple-output (MIMO) wireless systems use a transmission scheme between a transmitter (e.g. a base station) and a receiver (e.g. a UE) , where both transmitter and receiver are equipped with multiple antennas. Some portions of wireless communications system 100 may use beamforming. For example, 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 for beamforming in its communication with UE 115. Signals may be transmitted multiple times in different directions (e.g.， each transmission may be beamformed differently) . A mmW receiver (e.g.， a UE 115) may try multiple beams (e.g.， antenna subarrays) while receiving the synchronization signals.

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 beamforming or MIMO operation. One or more base station antennas or antenna arrays may be collocated 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 multiple use antennas or antenna arrays to conduct beamforming operations for directional communications with a UE 115.

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 ARQ (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 network device 105-c, network device 105-b, or core network 130 supporting radio bearers for user plane data. At the Physical (PHY) layer, transport channels may be mapped to physical channels.

Time intervals in LTE or NR may be expressed in multiples of a basic time unit (which may be a sampling period of T_s ＝ 1/30, 720, 000 seconds) . Time resources may be organized according to radio frames of length of 10ms (T_f ＝ 307200T_s) , which may be identified by a system frame number (SFN) ranging from 0 to 1023. Each frame may include ten 1ms subframes numbered from 0 to 9. A subframe may be further divided into two . 5ms slots, each of which contains 6 or 7 modulation symbol periods (depending on the length of the cyclic prefix prepended to each symbol) . Excluding the cyclic prefix, each symbol contains 2048 sample periods. In some cases the subframe may be the smallest scheduling unit, also known as a TTI. In other cases, a TTI may be shorter than a subframe or may be dynamically selected (e.g.， in short TTI bursts or in selected component carriers using short TTIs) .

A resource element may consist of one symbol period and one subcarrier (e.g., a 15 KHz frequency range) . A resource block may contain 12 consecutive subcarriers in the frequency domain and, for a normal cyclic prefix in each OFDM symbol, 7 consecutive OFDM symbols in the time domain (1 slot) , or 84 resource elements. The number of bits carried by each resource element may depend on the modulation scheme (the configuration of symbols that may be selected during each symbol period) . Thus, the more resource blocks that a UE receives and the higher the modulation scheme, the higher the data rate may be.

Wireless communications system 100 may support operation on multiple cells or carriers, a feature which may be referred to as carrier aggregation (CA) or multi-carrier operation. A carrier may also be referred to as a component carrier (CC) , a layer, a channel, etc. The terms “carrier, ” “component carrier, ” “cell, ” and “channel” may be used interchangeably herein. A UE 115 may be configured with multiple downlink CCs and one or more uplink CCs for carrier aggregation. 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 bandwidth, shorter symbol duration, shorter transmission time interval (TTIs) , and 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 (where more than one operator is allowed to use the spectrum) . An eCC characterized by wide bandwidth may include one or more segments that may be utilized by UEs 115 that are not capable of monitoring the whole bandwidth or prefer to use a limited 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 subcarrier spacing. A TTI in an eCC may consist of one or multiple symbols. In some cases, the TTI duration (that is, the number of symbols in a TTI) may be variable. 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 is associated with increased subcarrier spacing. A device, such as a UE 115 or base station 105, utilizing eCCs may transmit wideband signals (e.g.， 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 symbols. In some cases, the TTI duration (that is, the number of symbols in a TTI) may be variable.

In some cases, wireless system 100 may utilize both licensed and unlicensed radio frequency spectrum bands. For example, wireless system 100 may employ LTE License Assisted Access (LTE-LAA) or LTE Unlicensed (LTE U) radio access technology or NR technology in an unlicensed band such as the 5Ghz Industrial, Scientific, and Medical (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 the channel is clear before transmitting data. In some cases, operations in unlicensed bands may be based on a carrier aggregation (CA) configuration in conjunction with component carriers (CCs) operating in a licensed band. Operations in unlicensed spectrum may include downlink transmissions, uplink transmissions, or both. Duplexing in unlicensed spectrum may be based on frequency division duplexing (FDD) , time division duplexing (TDD) or a combination of both.

As described herein, the wireless communication system 100 may calculate a check metric that is a function of modified path metrics of a list decoder for suppressing a false alarm rate.

FIG. 2 illustrates an example of a wireless communication system 200 that supports false alarm rate suppression for polar codes in accordance with various aspects of the present disclosure. Wireless communication system 200 may include a base station 105-a and a UE 115-a. Base station 105-a is an example of base station 105 of FIG. 1, and user equipment 115-a is an example of user equipment 115 of FIG. 1.

Base station 105-a may use polar encoding to encode information bits for transmission to UE 115-a via a communication channel 225 (e.g.， a wireless channel) . In other examples, user equipment 115-a may encode data for transmission to base station 105-a or another UE using these same techniques. In further examples, base station 105-a may encode data for transmission to another base station 105-a using these same techniques. Moreover, devices other than base station 105-a and user equipment 115-a may use the techniques described herein.

In the depicted example, base station 105-a may include a data source 205, an error detecting code (EDC) encoder 210, a polar encoder 215, and a modulator 220. The data source 205 may provide an information vector of s information bits to be encoded and transmitted to the UE 115-a. The data source 205 may be coupled to a network, a storage device, or the like. The data source 205 may output the information vector to the EDC encoder 210.

The EDC encoder 210 may apply an error detecting algorithm to the information vector to generate an EDC. The EDC may be a code to enable the UE 115-a to detect an error in the information vector due to, for example, corruption due to noise in a transmission channel 225. In an example, the EDC algorithm may be a cyclic redundancy check (CRC) algorithm and the EDC may be a CRC. The EDC encoder 210 may append the EDC to the information vector to generate a payload. The EDC encoder 210 may output the payload to the polar encoder 215. The polar encoder 215 may perform a polar encoding technique on the payload to generate a polar-encoded codeword. In some examples, the polar encoder 215 may select sub-channels with high reliability to transmit the information bits and sub-channels with lower reliability to transmit the frozen bits (e.g.， set to zero by default) . In some examples, the polar encoder 215 may select a subset of the frozen bit sub-channels as parity check frozen sub-channels to transmit the parity check bits. A parity check bit may be a bit added to ensure that a total number of bits in the bit sequence, or portion of the bit sequence, is even or odd (e.g.， total number of ‘1’ bits in the bit sequence is even or odd) . The polar-encoded codeword may include information bits, parity check bits, frozen bits, or any combination thereof. The modulator 220 may modulate the polar-encoded codeword for transmission via wireless communication channel 225 which may distort the signal carrying the polar-encoded codeword with noise.

The UE 115-a may receive a signal that includes the polar-encoded codeword. In an example, the UE 115-a may include a demodulator 230, a decoder 235, and a data sink 240. The demodulator 230 may receive the signal including the polar-encoded codeword and input the demodulated signal into decoder 235 for decoding of the polar-encoded codeword. The demodulated signal may be, for example, a sequence of logarithmic-likelihood ratio (LLR) values representing a probability value of a received bit being a ‘0’ or a ‘1’ . The decoder 235 may perform a list decoding algorithm on the LLR values and may provide an output. If successfully able to decode the polar-encoded codeword, the decoder 235 may output a bit sequence of the information vector (e.g.， the s information bits input to the EDC encoder 210) to a data sink 240 for use, storage, communication to another device, communication via a network, or the like. Otherwise, the decoder 235 may indicate that decoding was unsuccessful. As noted above, while the example of FIG. 2 describes the base station 105-a performing the encoding and user equipment 115-a performing the decoding, the roles may be reversed. Moreover, devices other than the base station 105-a and the user equipment 115-a may perform the encoding and decoding.

In some instances, a conventional decoder may incorrectly output a bit sequence when in fact a different bit sequence was transmitted or no bit sequence was transmitted (i.e., the received signal is random or noise) . This is referred to as a false alarm. The decoder 235 may calculate a check metric that is a function of modified path metrics for suppressing a false alarm rate, as described below.

FIG. 3 illustrates an example diagram 300 of a decoder 235-a that supports false alarm rate suppression for polar codes in accordance with various aspects of the present disclosure. The decoder 235-a is an example of a decoder 235 of FIG. 2. The decoder 235-a may include a list decoder 305, a false alarm suppressor 310, and an error detector 315. The list decoder 305 may perform a path search algorithm to search a code tree for decoding a received polar-encoded codeword. As explained below in further detail, the list decoder 305 may identify the L best candidate paths through the code tree and a respective path metric for each of the L best candidate paths. The false alarm suppressor 310 may determine modified path metrics for the L best candidate paths that excludes the contribution of frozen bits (and/or parity check bits) to the path metric. The false alarm suppressor 310 may determine a check metric that is a function of the modified path metrics and compare the check metric to a threshold for suppressing a false alarm rate. If the threshold is not satisfied, false alarm suppressor 310 discards some or all of the L best candidate paths and declares a decoding error. If the threshold is satisfied for at least one candidate path, false alarm suppressor 310 provides some or all of the L best candidate paths to the error detector 315 for error checking.

FIG. 4 illustrates an example of a flow diagram 400 that supports false alarm rate suppression for polar codes in accordance with various aspects of the present disclosure. In flow diagram 400, the decoder 235-a may receive a polar-encoded codeword for decoding. The flow diagram 400 also refers to FIGs. 5-7 to illustrate aspects of the decoding process. The flow diagram may begin at 405 and proceed to block 410.

At 410, the list decoder 305 of decoder 235-a may perform a list decoding algorithm (e.g.， an SCL decoding algorithm) and identify L candidate paths through a code tree. The list decoder 305 may be, for example, an SCL decoder or the like. In an example, the list decoder 305 may search for the L best candidate paths through a code tree of all possible paths through the code tree. To do so, the list decoder 305 may determine a path metric for identifying which of the possible candidate paths through a code tree are the L best candidate paths. FIGs. 5-7, described below, provide examples on how to identify the L best candidate paths through a code tree.

FIG. 5 illustrates an example diagram of a code tree 500 that supports false alarm rate suppression for polar codes in accordance with various aspects of the present disclosure. Code tree 500 is a graphical representation of how list decoder 305 performs the list decoding process. The code tree 500 includes multiple nodes 505 and a line between pairs of nodes is referred to herein as a branch 550 (e.g.， branch 550-a connects node 505-a to node 505-b, and branch 550-b connects node 505-a to node 505-i) . Each branch 550 is associated with a possible value for a bit, which may be a ‘1’ or a ‘0’ . Branch 550-a is associated with a bit being a ‘0’ , and branch 550-b is associated with a bit being a ‘1’ . Each branch 550 is also associated with a value for a metric. The metric value may be a cost value representing a cost for proceeding from one node to the next. The metric value may be a function of a LLR value, a probability, or a combination thereof. The metric may be, for example, a distance metric (e.g.， LLR converted to a distance) or a probability metric (e.g.， LLR, etc. ) . The metric may represent a likelihood of moving from one node to the next based on whether the next bit in the sequence is a 1 or a 0. In some instances, the metric may represent a distance value between nodes.

The list decoder 305 may process demapped symbols output by the demodulator 230 and determine the probability (e.g.， LLR value) of whether bits corresponding to the demapped symbols are ‘0s’ or ‘1s’ . The determination of the probability of whether a particular bit value is a ‘0’ or a ‘1’ may also be a function of prior decoding decisions. This process is reflected in the code tree 500.

The list decoder 305 may initially begin at node 505-a and process the LLR values to determine along which branch to procced. At node 505-a, the list decoder 305 may determine the likelihood of whether an LLR value is a ‘0’ or a ‘1’ , and hence may proceed to either node 505-b or node 505-i. Node 505-b may be associated with the first bit being a ‘0’ , and node 505-i may be associated with the first bit being a ‘1’ . Each branch 550-a, 550-b is associated with a value for a metric and the list decoder 305 accumulates the metric values as it traverses branches 550 in the code tree 500 to generate a path metric. Accumulation to form the path metric may involve, for example, adding the metric value of each branch along a path. A path may refer to a particular route between nodes 505 through the code tree 500. The list decoder 305 selects which of the paths is the best using path metrics. The list decoder 305 may also penalize a path metric of a particular path if, for example, the list decoder 305 determines that a parity check along the path has failed at a particular level within the code tree 500. The penalty may be the addition and/or multiplication of a particular amount to the path metric for that path.

In some instances, the list decoder 305 may maintain a respective path metric for every possible path through code tree 500. Retaining path metrics for all possible paths may be computationally expensive and, in other instances, the list decoder 305 may use the path metrics to prune selected paths. For example, the list decoder 305 may have a list size L that limits the number of paths that are maintained at each level of the code tree. To do so, the list decoder 305 may maintain up to L candidate paths at each level, and discard the remaining candidate paths. In an example, FIG. 5 depicts level 0 to level 3. If L ＝ 4, the list decoder 305 may maintain up to 4 paths at each level, and may discard any additional paths. At level 1, there are two possible paths (e.g.， node 505-a to node 505-b, and node 505-a to node 505-i) , and hence the list decoder 305 may maintain both paths. At level 2, there are four possible paths (e.g.， node 505-a to node 505-b to node 505-c, node 505-a to node 505-b to node 505-f, node 505-a to node 505-i to node 505-j, and node 505-a to node 505-i to node 505-m) , and hence the list decoder 305 may maintain all 4 paths. At level three, there are 8 possible paths, and hence the list decoder 305 may maintain 4 of the 8 paths. At each subsequent level the number of possible paths doubles (e.g.， level four has 8 possible paths that reflect the possible nodes to which the 4 starting paths can reach, and so forth) , and the list decoder 305 may maintain 4 of the paths. FIGs. 6-7 depict the process for pruning paths when proceeding from level two to level three.

FIG. 6 illustrates an example diagram of a code tree 600 that supports false alarm rate suppression for polar codes in accordance with various aspects of the present disclosure. As shown, the list decoder 305 is extending the paths 610 from the nodes at level 2 to the nodes at level 3. As depicted, path 610-a includes node 505-a, 505-b, and 505-c, and may be extended to either node 505-d or 505-e. Path 610-b includes node 505-a, 505-b, and 505-f, and may be extended to either node 505-g or 505-h. Path 610-c includes node 505-a, 505-i, and 505-j, and may be extended to either node 505-k or 505-l. Path 610-d includes node 505-a, 505-i, and 505-m, and may be extended to either node 505-n or 505-o.

The list decoder 305 may retain L paths having the best path metrics. The list decoder 305 may use the path metrics, which are accumulated metric values, for determining which paths to keep (e.g.， minimum accumulated distance, highest accumulated probability, etc. ) . For example, the list decoder 305 may add a metric value for the branch proceeding from node 505-c to node 505-d to an accumulated value for path 610-a to determine a path metric to extend path 610-a to node 505-d. The list decoder 305 may make a similar determination for extending all of the paths 610 to any of the nodes in level 3. In this example, the list decoder 305 may have 8 possible paths to the nodes in level 3 and determine a path metric for each of the 8 possible paths. Because L ＝ 4, the list decoder 305 may sort the path metrics (e.g.， from highest to lowest, from lowest to highest, etc. ) and select 4 of the 8 paths that have the best path metric (e.g.， minimum accumulated distance, highest accumulated probability, etc. ) , as shown in FIG. 7.

FIG. 7 illustrates an example diagram of a code tree 700 that supports false alarm rate suppression for polar codes in accordance with various aspects of the present disclosure. As depicted, list decoder 305 retains four of the possible paths. Here, paths 720-a, 720-b, 720-c, and 720-d have the best path metrics and hence are maintained at level 3. As depicted, path 720-a includes node 505-a, 505-b, 505-f, and 505-g. Path 720-b includes node 505-a, 505-i, 505-j, and 505-k. Path 720-c includes node 505-a, 505-i, 505-m, and 505-n. Path 720-d includes node 505-a, 505-i, 505-m, and 505-o. The other paths may be discarded and not used in subsequent analysis. The principles described with respect to FIGs. 5-7 may be extended to a code tree having any number of levels, and the list decoder 305 may select a list size number of candidate paths having the best path metrics through such a code tree.

Referring back to FIG. 4, false alarm suppressor 310 may determine modified path metrics for the L best candidate paths. As noted above, a path metric of each candidate path is an accumulation of metric values for proceeding from one node to the next along the path, and may also include penalties incurred for failing a parity check. As the polar-encoded codeword includes information bits, frozen bits, parity check bits, or any combination thereof, metric values of each of these different types of bits contributes to the path metric. The false alarm suppressor 310 may know the type and location of each bit within the code tree, and may determine modified path metrics that exclude the metric values attributable to frozen bits (and/or parity check bits) .

In an example, a path metric may add the metric values for proceeding from node to node, and the path metric may be a total of the metric values. Because the false alarm suppressor 310 may know which branches in the code tree correspond to each type of bit, the false alarm suppressor 310 may subtract out the metric values of the frozen bits (and optionally of the parity check bits) . In an example with reference to FIG. 7, path 720-a includes node 505-a, node 505-b, node 505-f, and node 505-g and, for example, has a path metric of 0.25. The path metric may be an accumulation of metric values along the path. For example, the branch 550-a between node 505-a and node 505-b (see also FIG. 5) may have a metric value of 0.12, the branch 550-c between node 505-b and node 505-f may have a metric value of 0.08, the branch 550-d between node 505-f and node 505-g may have a metric value of 0.05. The false alarm suppressor 310 may know that branch 550-a corresponds to an information bit, branch 550-c corresponds to a parity check bit, and that branch 550-d corresponds to an frozen bit. The false alarm suppressor 310 may exclude the contribution of the frozen bit by subtracting from the path metric the metric value for branch 550-d (e.g., modified path metric ＝ 0.25 –0.05 ＝ 0.2) . This represents a simplified example. A path typically may include more than one frozen bit and a sum of the metric values of the frozen bits along the path 720 may be subtracted from the path metric of path 720 to obtain the modified path metric.

In other examples, the false alarm suppressor 310 may also exclude the metric values corresponding to frozen bits and parity check bits. The false alarm suppressor 310 may thus determine a modified path metric of a path by subtracting from the path metric the sum of the metric values of the frozen bits along the path and the sum of the of the metric values of the parity check bits along the path. The false alarm suppressor 310 may repeat the process to determine a modified path metric for each of the L candidate paths output by the list decoder 305. In the example of FIG. 7, the false alarm suppressor 310 may determine a modified path metric for path 720-a, a modified path metric for path 720-b, a modified path metric for path 720-c, and a modified path metric for path 720-c.

At 425, the false alarm suppressor 310 may determine a check metric that is a function of the modified path metrics. In an example, the false alarm suppressor 310 may determine a minimum of the modified path metrics for paths 720-a to 720-d and a statistical value of the modified path metrics for paths 720-a to 720-d. The statistical value may be a mean, median, standard deviation, or the like, of the modified path metrics. The check metric may be a function of the minimum path metric and the statistical value. For example, the function may be:

where M is a constant (e.g.， M ＝1) . In some examples, the statistical value may exclude the value of the minimum modified path metric. The check metric may be other functions of the minimum path metric and the statistical value.

Instead of or in addition to determining the check metric using the minimum modified path metric, the check metric may be determined for some or all of the L candidate paths output by the list decoder 305. For example, the function may be:

where M is a constant (e.g.， M ＝1) and k ＝ 1, ... L, where L is an integer that is the list size number of candidate paths output by the list decoder 305. In some examples, the statistical value may exclude the value of the modified path metric of Path P_k.

At 430, the false alarm suppressor 310 may determine whether the check metric satisfies a threshold. The threshold may correspond to, or may be a function of, a desired false alarm rate. The threshold may be a fixed value or may be adjusted based at least in part on feedback indicating the actual false alarm rate. The feedback may be used to increase or decrease the threshold if, for example, the BLER is too high or too low. In an example, the false alarm suppressor 310 may determine that the threshold is not satisfied if the check metric is less than or equal to the threshold, and satisfied if the check metric is greater than the threshold. If not satisfied, the flow diagram 400 may proceed to 435.

At 435, the false alarm suppressor 310 may determine that the candidate path having the minimum modified path metric (or other candidate path being considered) is a false alarm risk due to failing to satisfy the threshold.

At 440, the false alarm suppressor 310 may discard the candidate path. In some instances, the false alarm suppressor 310 may discard all of the candidate paths through the code tree (e.g.， paths 720-a to 720-d in code tree 700) output by the list decoder 305 if the check metric corresponding to the minimum modified path metric fails to satisfy the threshold. In that example, the flow diagram 400 may proceed to 470. In other examples, candidate paths may be discarded on a path by path basis. Thus, the candidate path associated with the minimum modified path metric may be discarded and the flow diagram 400 may return to 425 for generating a check metric for each candidate path. The false alarm suppressor 310 may iteratively determine whether a check metric associated with a particular path satisfies the threshold. Only the candidate paths that fail to satisfy the threshold are discarded at 440. Returning to 430, if the check metric of one or more candidate paths satisfies the threshold, the flow diagram 400 may proceed to 445.

Operations

445, 450, 455, 460, and 465 of flow diagram 400 correspond to performing an error detection function on a bit sequence corresponding to a respective one of the candidate paths until one of the bit sequences passes or all bit sequences fail. In some instances, if the check metric associated with the candidate path having the minimum modified path metric satisfies the threshold at 430, then error detection is performed on the candidate path having the minimum modified path metric and all of the other candidate paths output by list decoder 305. In other instances, error detection is only performed on the candidate paths having a check metric that satisfies the threshold at 430.

At 445, the error detector 315 may receive a bit sequence corresponding to a candidate path and perform an error detection algorithm on the bit sequence. The error detection algorithm may be, for example, a CRC algorithm. In FIG. 7, for example, path 720-a corresponds to the

bit sequence

0, 1, 0.

In some examples, ranking may be used to determine the order in which bit sequences of candidate paths are checked. For example, the error detector 315 may rank the candidate paths according to their unmodified path metrics (e.g.， path metrics output by list decoder 305) and check candidates paths in that order (e.g.， start from candidate path having the lowest accumulated distance metric and proceed in order to the candidate path having the highest accumulated distance metric) . In some cases, the ranking may be according to the modified path metrics. In some other cases, the error detector 315 may determine, for each candidate path, a value that is a function of a modified path metric and an unmodified path metric of that path (e.g.， average, weighted average, median, statistical value, etc. ) , and may rank the candidate paths according to the values. The error detector 315 may also randomly select the order in which error checking is performed on the candidate paths.

As described above, the polar-encoded codeword may be generated by polar encoding a payload that includes an information vector and an EDC. If the bit sequence of a particular path is the same as the bit sequence of the payload, the error detector 315 should be able to parse the bit sequence to recover the information vector and the received EDC. The error detector 315 may then generate a calculated EDC using the parsed information vector by applying the same algorithm to the parsed information vector as applied by the EDC encoder 210. If the calculated EDC is the same as the received EDC, the error detector 315 determines that it was able to successfully able to decode the polar-encoded codeword and outputs, at 455, the bit sequence of the information vector, with or without the EDC. If not the same, the error detector 315 informs the false alarm suppressor 310 of the decoding failure, and the flow diagram 400 proceeds to 460.

At 460, the error detector 315 may discard the bit sequence and, at 465, may determine, in conjunction with the false alarm suppressor 310, whether there are any more candidate paths to check. If yes, the flow diagram 400 proceeds to 460 to check a bit sequence corresponding to a next candidate path (e.g.， in the ranked order) . If all candidate paths have been checked, the flow diagram 400 may proceed to 470.

At 470, the error detector 315 outputs a decoding error. The operations of the flow diagram 400 may be performed in other orders and/or by other components than those described herein. The example described in FIG. 4 uses path metrics for which the best paths have the minimum metrics (e.g.， a distance metric or inverse probability metric) . Where the best path metrics are relatively larger (e.g.， probability metrics) , the function and threshold may be inverted or otherwise adapted to reflect that the maximum path metric is the best path metric.

The examples described herein provide a number of advantages over conventional solutions. The examples described herein are effective in various scenarios in which a false alarm may occur, includes when a received signal only contains noise, a received signal contains a control message addressed to a different receiver, a received signal contains a message other than a control message, or the like. Moreover, the examples described herein may be used for determining a correct control message format (e.g.， information bits length) during blind detection.

Advantageously, the examples described herein are robust to SNR variations as the modified path metric and/or the check metric are less sensitive to SNR variations than conventional solutions. As noted above, a path metric for a candidate path output by a list decoder is accumulation of LLR values of input bits, and hence is dependent on a SNR. The check metric, in comparison, is a ratio of modified path metrics, and the ratio reduces and/or eliminates sensitivity to SNR variations.

The example embodiments may also intelligently suppress a false alarm rate independent of the number of frozen bits (and/or parity check bits) in a polar-encoded codeword. As noted above, the path metric for a candidate path output by a list decoder is a function of the number of frozen bits. In many scenarios, frozen bits outnumber information and parity check frozen bits and hence may contribute a large portion to a path metric for a particular candidate path. Frozen bits, however, are uncorrelated with information bits and hence cannot be used to detect errors in information bits. By generating modified path metrics that exclude the contribution of frozen bits to the path metric, the check metric better reflects errors in the information bits and hence is a better way of identifying false alarm risk.

The example embodiments also may be used to reduce EDC bit overhead. For example, using the techniques described herein using a 12-bit CRC provides a false alarm rate comparable to a 16-bit CRC while maintaining a similar BLER.

FIG. 8 shows a block diagram 800 of a wireless device 805 that supports false alarm rate suppression for polar codes in accordance with various aspects of the present disclosure. Wireless device 805 may be an example of aspects of a user equipment (UE) 115 or base station 105 as described with reference to FIG. 1. Wireless device 805 may include receiver 810, communications manager 815, and transmitter 820. Wireless device 805 may also include a processor. Each of these components may be in communication with one another (e.g.， via one or more buses) .

Receiver 810 may receive a signal that includes a polar-encoded codeword and may pass the signal to other components of the wireless device 805. The receiver 810 may be an example of aspects of the transceiver 1135 described with reference to FIG. 11.

Communications manager 815 may be an example of aspects of the communications manager 1115 described with reference to FIG. 11. Communications manager 815 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 communications manager 815 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 communications manager 815 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, communications manager 815 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, communications manager 815 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.

Communications manager 815 may determine a path metric for each of a set of paths through a code tree for decoding a polar-encoded codeword, where a portion of each of the path metrics corresponds to at least one frozen bit in the polar-encoded codeword, determine a modified path metric for each of the set of paths by excluding the respective portion corresponding to the at least one frozen bit in each of the set of paths, determine a check metric for at least one of the set of paths based on the modified path metrics, and perform an error detecting algorithm on a bit sequence corresponding to the at least one of the set of paths based on the check metric satisfying a threshold.

Transmitter 820 may transmit signals generated by other components of the device. In some examples, the transmitter 820 may be collocated with a receiver 810 in a transceiver module. For example, the transmitter 820 may be an example of aspects of the transceiver 1135 described with reference to FIG. 11. The transmitter 820 may include a single antenna, or it may include a set of antennas.

FIG. 9 shows a block diagram 900 of a wireless device 905 that supports false alarm rate suppression for polar codes in accordance with various aspects of the present disclosure. Wireless device 905 may be an example of aspects of a wireless device 805 or a UE 115 or base station 105 as described with reference to FIGs. 1 and 8. Wireless device 905 may include receiver 910, communications manager 915, and transmitter 920. Wireless device 905 may also include a processor. Each of these components may be in communication with one another (e.g.， via one or more buses) .

Receiver 910 may receive a signal that includes a polar-encoded codeword and may pass the signal to other components of the wireless device 905. The receiver 910 may be an example of aspects of the transceiver 1135 described with reference to FIG. 11.

Communications manager 915 may be an example of aspects of the communications manager 1115 described with reference to FIG. 11. Communications manager 915 may also include list decoder 925, false alarm suppressor 930, and error detector 935.

List decoder 925 may determine a path metric for each of a set of paths through a code tree for decoding a polar-encoded codeword, where a portion of each of the path metrics corresponds to at least one frozen bit in the polar-encoded codeword. List decoder 925 may perform a successive cancellation list (SCL) decoding algorithm for determining the set of paths through the code tree, where the set of paths are a subset of possible paths through the code tree. In some cases, each of the path metrics is an accumulation of cost values for traversing a respective one of the set of paths, and where each of the cost values represent a cost for moving from one node to another node along the respective path in the code tree. In some cases, each of the cost values is a function of a logarithmic-likelihood ratio, a probability, or a combination thereof.

False alarm suppressor 930 may determine a modified path metric for each of the set of paths by excluding the respective portion corresponding to the at least one frozen bit in each of the set of paths. False alarm suppressor 930 may determine a check metric for at least one of the set of paths based on the modified path metrics, and determine a minimum modified path metric and a statistical value of the modified path metrics. In some cases, the check metric is a function of the minimum modified path metric and the statistical value. In some cases, the function is a difference between a constant and a ratio of the minimum modified path metric and the statistical value. In some cases, the statistical value of the modified path metrics excludes the minimum modified path metric. In some cases, the bit sequence includes at least one information bit. In some cases, the at least one of the set of paths corresponds to a particular path of the set of paths that has a minimum of the path metrics. In some cases, the at least one of the set of paths corresponds to a particular path of the set of paths that has a minimum of the modified path metrics. In some cases, the threshold is a function of a false alarm rate.

Error detector 935 may perform an error detecting algorithm on a bit sequence corresponding to the at least one of the set of paths based on the check metric satisfying a threshold. In some cases, the error detecting algorithm is a cyclic redundancy check (CRC) algorithm.

Transmitter 920 may transmit signals generated by other components of the device. In some examples, the transmitter 920 may be collocated with a receiver 910 in a transceiver module. For example, the transmitter 920 may be an example of aspects of the transceiver 1135 described with reference to FIG. 11. The transmitter 920 may include a single antenna, or it may include a set of antennas.

FIG. 10 shows a block diagram 1000 of a communications manager 1015 that supports false alarm rate suppression for polar codes in accordance with various aspects of the present disclosure. The communications manager 1015 may be an example of aspects of a communications manager 815, a communications manager 915, or a communications manager 1115 described with reference to FIGs. 8, 9, and 11. The communications manager 1015 may include list decoder 1020, false alarm suppressor 1025, and error detector 1030. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses) .

List decoder 1020 may determine a path metric for each of a set of paths through a code tree for decoding a polar-encoded codeword, where a portion of each of the path metrics corresponds to at least one frozen bit in the polar-encoded codeword. List decoder 1020 may perform a successive cancellation list (SCL) decoding algorithm for determining the set of paths through the code tree, where the set of paths are a subset of possible paths through the code tree. In some cases, each of the path metrics is an accumulation of cost values for traversing a respective one of the set of paths, and where each of the cost values represent a cost for moving from one node to another node along the respective path in the code tree. In some cases, each of the cost values is a function of a logarithmic-likelihood ratio, a probability, or a combination thereof.

False alarm suppressor 1025 may determine a modified path metric for each of the set of paths by excluding the respective portion corresponding to the at least one frozen bit in each of the set of paths. False alarm suppressor 1025 may determine a check metric for at least one of the set of paths based on the modified path metrics, and determine a minimum modified path metric and a statistical value of the modified path metrics. In some cases, the check metric is a function of the minimum modified path metric and the statistical value. In some cases, the function is a difference between a constant and a ratio of the minimum modified path metric and the statistical value. In some cases, the statistical value of the modified path metrics excludes the minimum modified path metric. In some cases, the bit sequence includes at least one information bit. In some cases, the at least one of the set of paths corresponds to a particular path of the set of paths that has a minimum of the path metrics. In some cases, the at least one of the set of paths corresponds to a particular path of the set of paths that has a minimum of the modified path metrics. In some cases, the threshold is a function of a false alarm rate.

Error detector 1030 may perform an error detecting algorithm on a bit sequence corresponding to the at least one of the set of paths based on the check metric satisfying a threshold. In some cases, the error detecting algorithm is a CRC algorithm.

FIG. 11 shows a diagram of a system 1100 including a device 1105 that supports false alarm rate suppression for polar codes in accordance with various aspects of the present disclosure. Device 1105 may be an example of or include the components of wireless device 805, wireless device 905, or a UE 115 as described above, e.g.， with reference to FIGs. 1, 8 and 9. Device 1105 may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including UE communications manager 1115, processor 1120, memory 1125, software 1130, transceiver 1135, antenna 1140, and I/O controller 1145. These components may be in electronic communication via one or more busses (e.g.， bus 1110) . Device 1105 may communicate wirelessly with one or more base stations 105.

Processor 1120 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 1120 may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into processor 1120. Processor 1120 may be configured to execute computer-readable instructions stored in a memory to perform various functions (e.g., functions or tasks supporting false alarm rate suppression for polar codes) .

Memory 1125 may include random access memory (RAM) and read only memory (ROM) . The memory 1125 may store computer-readable, computer-executable software 1130 including instructions that, when executed, cause the processor to perform various functions described herein. In some cases, the memory 1125 may contain, among other things, a basic input/output system (BIOS) which may control basic hardware and/or software operation such as the interaction with peripheral components or devices.

Software 1130 may include code to implement aspects of the present disclosure, including code to support false alarm rate suppression for polar codes. Software 1130 may be stored in a non-transitory computer-readable medium such as system memory or other memory. In some cases, the software 1130 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 1135 may communicate bi-directionally, via one or more antennas, wired, or wireless links as described above. For example, the transceiver 1135 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver 1135 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 1140. However, in some cases the device may have more than one antenna 1140, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

I/O controller 1145 may manage input and output signals for device 1105. I/O controller 1145 may also manage peripherals not integrated into device 1105. In some cases, I/O controller 1145 may represent a physical connection or port to an external peripheral. In some cases, I/O controller 1145 may utilize an operating system such as

or another known operating system. In other cases, I/O controller 1145 may represent or interact with a modem, a keyboard, a mouse, a touchscreen, or a similar device. In some cases, I/O controller 1145 may be implemented as part of a processor. In some cases, a user may interact with device 1105 via I/O controller 1145 or via hardware components controlled by I/O controller 1145.

FIG. 12 shows a diagram of a system 1200 including a device 1205 that supports false alarm rate suppression for polar codes in accordance with various aspects of the present disclosure. Device 1205 may be an example of or include the components of wireless device 905, wireless device 1005, or a base station 105 as described above, e.g.， with reference to FIGs. 1, 9 and 10. Device 1205 may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including base station communications manager 1215, processor 1220, memory 1225, software 1230, transceiver 1235, antenna 1240, network communications manager 1245, and base station controller 1250. These components may be in electronic communication via one or more busses (e.g.， bus 1210) . Device 1205 may communicate wirelessly with one or more UEs 115.

Base station communications manager 1215 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 base station communications manager 1215 may coordinate scheduling for transmissions to UEs 115 for various interference mitigation techniques such as beamforming or joint transmission. In some examples, base station communications manager 1215 may provide an X2 interface within an Long Term Evolution (LTE) /LTE-A wireless communication network technology to provide communication between base stations 105.

Processor 1220 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 1220 may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into processor 1220. Processor 1220 may be configured to execute computer-readable instructions stored in a memory to perform various functions (e.g.， functions or tasks supporting false alarm rate suppression for polar codes) .

Memory 1225 may include RAM and ROM. The memory 1225 may store computer-readable, computer-executable software 1230 including instructions that, when executed, cause the processor to perform various functions described herein. In some cases, the memory 1225 may contain, among other things, a BIOS which may control basic hardware and/or software operation such as the interaction with peripheral components or devices.

Software 1230 may include code to implement aspects of the present disclosure, including code to support false alarm rate suppression for polar codes. Software 1230 may be stored in a non-transitory computer-readable medium such as system memory or other memory. In some cases, the software 1230 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 1235 may communicate bi-directionally, via one or more antennas, wired, or wireless links as described above. For example, the transceiver 1235 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver 1235 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 1240. However, in some cases the device may have more than one antenna 1240, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

Network communications manager 1245 may manage communications with the core network (e.g.， via one or more wired backhaul links) . For example, the network communications manager 1245 may manage the transfer of data communications for client devices, such as one or more UEs 115.

Base station controller 1250 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 base station controller 1250 may coordinate scheduling for transmissions to UEs 115 for various interference mitigation techniques such as beamforming or joint transmission. In some examples, base station controller 1250 may provide an X2 interface within an LTE/LTE-A wireless communication network technology to provide communication between base stations 105.

FIG. 13 shows a flowchart illustrating a method 1300 for false alarm rate suppression for polar codes in accordance with various aspects of the present disclosure. The operations of method 1300 may be implemented by a UE 115 or base station 105 or its components as described herein. For example, the operations of method 1300 may be performed by a communications manager as described with reference to FIGs. 8 through 10. In some examples, a UE 115 or 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 UE 115 or base station 105 may perform aspects of the functions described below using special-purpose hardware.

At block 1305 the UE 115 or base station 105 may determine a path metric for each of a plurality of paths through a code tree for decoding a polar-encoded codeword, wherein a portion of each of the path metrics corresponds to at least one frozen bit in the polar-encoded codeword. The operations of block 1305 may be performed according to the methods described with reference to FIGs. 1 through 7. In certain examples, aspects of the operations of block 1305 may be performed by a list decoder as described with reference to FIGs. 8 through 10.

At block 1310 the UE 115 or base station 105 may determine a modified path metric for each of the plurality of paths by excluding the respective portion corresponding to the at least one frozen bit in each of the plurality of paths. The operations of block 1310 may be performed according to the methods described with reference to FIGs. 1 through 7. In certain examples, aspects of the operations of block 1310 may be performed by a false alarm suppressor as described with reference to FIGs. 8 through 10.

At block 1315 the UE 115 or base station 105 may determine a check metric for at least one of the plurality of paths based at least in part on the modified path metrics. The operations of block 1315 may be performed according to the methods described with reference to FIGs. 1 through 7. In certain examples, aspects of the operations of block 1315 may be performed by a false alarm suppressor as described with reference to FIGs. 8 through 10.

At block 1320 the UE 115 or base station 105 may perform an error detecting algorithm on a bit sequence corresponding to the at least one of the plurality of paths based at least in part on the check metric satisfying a threshold. The operations of block 1320 may be performed according to the methods described with reference to FIGs. 1 through 7. In certain examples, aspects of the operations of block 1320 may be performed by an error detector as described with reference to FIGs. 8 through 10.

FIG. 14 shows a flowchart illustrating a method 1400 for false alarm rate suppression for polar codes in accordance with various aspects of the present disclosure. The operations of method 1400 may be implemented by a UE 115 or base station 105 or its components as described herein. For example, the operations of method 1400 may be performed by a communications manager as described with reference to FIGs. 8 through 10. In some examples, a UE 115 or 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 UE 115 or base station 105 may perform aspects of the functions described below using special-purpose hardware.

At block 1405 the UE 115 or base station 105 may determine a path metric for each of a plurality of paths through a code tree for decoding a polar-encoded codeword, wherein a portion of each of the path metrics corresponds to at least one frozen bit in the polar-encoded codeword. The operations of block 1405 may be performed according to the methods described with reference to FIGs. 1 through 7. In certain examples, aspects of the operations of block 1405 may be performed by a list decoder as described with reference to FIGs. 8 through 10.

At block 1410 the UE 115 or base station 105 may determine a modified path metric for each of the plurality of paths by excluding the respective portion corresponding to the at least one frozen bit in each of the plurality of paths. The operations of block 1410 may be performed according to the methods described with reference to FIGs. 1 through 7. In certain examples, aspects of the operations of block 1410 may be performed by a false alarm suppressor as described with reference to FIGs. 8 through 10.

At block 1415 the UE 115 or base station 105 may determine a minimum of the modified path metrics and a statistical value of the modified path metrics. The operations of block 1415 may be performed according to the methods described with reference to FIGs. 1 through 7. In certain examples, aspects of the operations of block 1415 may be performed by a false alarm suppressor as described with reference to FIGs. 8 through 10.

At block 1420 the UE 115 or base station 105 may determine a check metric for at least one of the plurality of paths based at least in part on the minimum modified path metric and the statistical value. The operations of block 1420 may be performed according to the methods described with reference to FIGs. 1 through 7. In certain examples, aspects of the operations of block 1420 may be performed by an error detector as described with reference to FIGs. 8 through 10.

At block 1425 the UE 115 or base station 105 may perform an error detecting algorithm on a bit sequence corresponding to the at least one of the plurality of paths based at least in part on the check metric satisfying a threshold. The operations of block 1425 may be performed according to the methods described with reference to FIGs. 1 through 7. In certain examples, aspects of the operations of block 1425 may be performed by a false alarm suppressor as described with reference to FIGs. 8 through 10.

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. Furthermore, 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. The terms “system” and “network” are often used interchangeably. A code division multiple access (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 time division multiple access (TDMA) system may implement a radio technology such as Global System for Mobile Communications (GSM) .

An orthogonal frequency division multiple access (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) . 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are releases of Universal Mobile Telecommunications System (UMTS) that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, NR, and Global System for Mobile communications (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 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.

In LTE/LTE-A networks, including such networks described herein, the term evolved node B (eNB) may be generally used to describe the base stations. The wireless communications system or systems described herein may include a heterogeneous LTE/LTE-A or NR network in which different types of evolved node B (eNBs) provide coverage for various geographical regions. For example, each eNB, gNB or base station may provide communication coverage for a macro cell, a small cell, or other types of cell. The term “cell” may be used to describe a base station, a carrier or component carrier associated with a base station, or a coverage area (e.g.， sector, etc. ) of a carrier or base station, depending on context.

Base stations 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, eNodeB (eNB) , next generation NodeB (gNB) , Home NodeB, a Home eNodeB, or some other suitable terminology. The geographic coverage area for a base station may be divided into sectors making up only a portion of the coverage area. The wireless communications system or systems described herein may include base stations of different types (e.g., macro or small cell base stations) . The UEs described herein may be able to communicate with various types of base stations and network equipment including macro eNBs, small cell eNBs, gNBs, relay base stations, and the like. There may be overlapping geographic coverage areas for different technologies.

A macro cell generally covers a relatively large geographic area (e.g.， several kilometers in radius) and may allow unrestricted access by UEs with service subscriptions with the network provider. A small cell is a lower-powered base station, as compared with a macro cell, that 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 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 having an association with the femto cell (e.g.， UEs in a closed subscriber group (CSG) , UEs 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 (e.g.， component carriers) .

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

The downlink transmissions described herein may also be called forward link transmissions while the uplink transmissions may also be called reverse link transmissions. Each communication link described herein—including, for example,

wireless communications system

100 and 200 of FIGs. 1 and 2—may include one or more carriers, where each carrier may be a signal made up of multiple sub-carriers (e.g.， waveform signals of different frequencies) .

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.

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.

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 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 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. Also, as used herein, including in the claims, “or” as used in a list of items (for example, 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. ”

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 RAM, ROM, electrically erasable programmable read only memory (EEPROM) , 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, digital subscriber line (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.

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:

determining a path metric for each of a plurality of paths through a code tree for decoding a polar-encoded codeword, wherein a portion of each of the path metrics corresponds to at least one frozen bit in the polar-encoded codeword；

determining a modified path metric for each of the plurality of paths by excluding the respective portion corresponding to the at least one frozen bit in each of the plurality of paths；

determining a check metric for at least one of the plurality of paths based at least in part on the modified path metrics； and

performing an error detecting algorithm on a bit sequence corresponding to the at least one of the plurality of paths based at least in part on the check metric satisfying a threshold.
The method of claim 1, further comprising:

determining a minimum modified path metric and a statistical value of the modified path metrics.
The method of claim 2, wherein the check metric is a function of the minimum modified path metric and the statistical value.
The method of claim 3, wherein the function is a difference between a constant and a ratio of the minimum modified path metric and the statistical value.
The method of claim 2, wherein the statistical value of the modified path metrics excludes the minimum modified path metric.
The method of claim 1, wherein the bit sequence includes at least one information bit.
The method of claim 1, wherein the at least one of the plurality of paths corresponds to a particular path of the plurality of paths that has a minimum of the path metrics.
The method of claim 1, wherein the at least one of the plurality of paths corresponds to a particular path of the plurality of paths that has a minimum of the modified path metrics.
The method of claim 1, further comprising:

performing a successive cancellation list (SCL) decoding algorithm for determining the plurality of paths through the code tree, wherein the plurality of paths are a subset of possible paths through the code tree.
The method of claim 1, wherein each of the path metrics is an accumulation of cost values for traversing a respective one of the plurality of paths, and wherein each of the cost values represent a cost for moving from one node to another node along the respective path in the code tree.
The method of claim 10, wherein each of the cost values is a function of a logarithmic-likelihood ratio, a probability, or a combination thereof.
The method of claim 1, wherein the error detecting algorithm is a cyclic redundancy check (CRC) algorithm.
The method of claim 1, wherein the threshold is a function of a false alarm rate.
An apparatus for wireless communication, in a system comprising:

a processor；

memory in electronic communication with the processor； and

instructions stored in the memory and operable, when executed by the processor, to cause the apparatus to:

determine a path metric for each of a plurality of paths through a code tree for decoding a polar-encoded codeword, wherein a portion of each of the path metrics corresponds to at least one frozen bit in the polar-encoded codeword；

determine a modified path metric for each of the plurality of paths by excluding the respective portion corresponding to the at least one frozen bit in each of the plurality of paths；

determine a check metric for at least one of the plurality of paths based at least in part on the modified path metrics； and

perform an error detecting algorithm on a bit sequence corresponding to the at least one of the plurality of paths based at least in part on the check metric satisfying a threshold.
The apparatus of claim 14, wherein the instructions are further executable by the processor to:

determine a minimum modified path metric and a statistical value of the modified path metrics.
The apparatus of claim 15, wherein the check metric is a function of the minimum modified path metric and the statistical value.
The apparatus of claim 16, wherein the function is a difference between a constant and a ratio of the minimum modified path metric and the statistical value.
The apparatus of claim 15, wherein the statistical value of the modified path metrics excludes the minimum modified path metric.
The apparatus of claim 14, wherein the bit sequence includes at least one information bit.
The apparatus of claim 14, wherein the at least one of the plurality of paths corresponds to a particular path of the plurality of paths that has a minimum of the path metrics.
The apparatus of claim 14, wherein the at least one of the plurality of paths corresponds to a particular path of the plurality of paths that has a minimum of the modified path metrics.
The apparatus of claim 14, wherein the instructions are further executable by the processor to:

perform a successive cancellation list (SCL) decoding algorithm for determining the plurality of paths through the code tree, wherein the plurality of paths are a subset of possible paths through the code tree.
The apparatus of claim 14, wherein each of the path metrics is an accumulation of cost values for traversing a respective one of the plurality of paths, and wherein each of the cost values represent a cost for moving from one node to another node along the respective path in the code tree.
The apparatus of claim 23, wherein each of the cost values is a function of a logarithmic-likelihood ratio, a probability, or a combination thereof.
The apparatus of claim 14, wherein the error detecting algorithm is a cyclic redundancy check (CRC) algorithm.
The apparatus of claim 14, wherein the threshold is a function of a false alarm rate.
An apparatus for wireless communication, comprising:

means for determining a path metric for each of a plurality of paths through a code tree for decoding a polar-encoded codeword, wherein a portion of each of the path metrics corresponds to at least one frozen bit in the polar-encoded codeword；

means for determining a modified path metric for each of the plurality of paths by excluding the respective portion corresponding to the at least one frozen bit in each of the plurality of paths；

means for determining a check metric for at least one of the plurality of paths based at least in part on the modified path metrics； and

means for performing an error detecting algorithm on a bit sequence corresponding to the at least one of the plurality of paths based at least in part on the check metric satisfying a threshold.
A non-transitory computer readable medium storing code for wireless communication, the code comprising instructions executable by a processor to:

determine a path metric for each of a plurality of paths through a code tree for decoding a polar-encoded codeword, wherein a portion of each of the path metrics corresponds to at least one frozen bit in the polar-encoded codeword；

determine a modified path metric for each of the plurality of paths by excluding the respective portion corresponding to the at least one frozen bit in each of the plurality of paths；

determine a check metric for at least one of the plurality of paths based at least in part on the modified path metrics； and

perform an error detecting algorithm on a bit sequence corresponding to the at least one of the plurality of paths based at least in part on the check metric satisfying a threshold.