WO2020057477A1

WO2020057477A1 - A polar code design for physical downlink control channel re-transmission

Info

Publication number: WO2020057477A1
Application number: PCT/CN2019/106081
Authority: WO
Inventors: Changlong Xu; Liangming WU; Kai Chen; Jian Li; Hao Xu
Original assignee: Qualcomm Incorporated
Priority date: 2018-09-20
Filing date: 2019-09-17
Publication date: 2020-03-26
Also published as: WO2020056679A1

Abstract

Methods, systems, and devices for wireless communications are described. Some wireless systems support polar encoding for physical downlink control channel (PDCCH) transmissions. In these systems, a base station may encode downlink control information (DCI) to obtain a set of mother code bits and load the bits into a circular buffer. The base station may select a set of coded bits from the buffer for transmission in a PDCCH transmission. The base station may additionally send a re-transmission including a different set of coded bits from the buffer. These sets of coded bits for the two transmissions may correspond to two different ranges of bits in the circular buffer, where the two ranges are contiguous. Additionally, the base station may adaptively change the aggregation level for the second transmission based on channel conditions. A receiving device may combine the transmissions for decoding, achieving chase combining and incremental redundancy (IR) gains.

Description

A POLAR CODE DESIGN FOR PHYSICAL DOWNLINK CONTROL CHANNEL RE-TRANSMISSION

CROSS REFERENCES

The present Application for Patent claims priority to International Patent Application No. PCT/CN2018/106737 to Xu et al., titled “A POLAR CODE DESIGN FOR PHYSICAL DOWNLINK CONTROL CHANNEL RE-TRANSMISSION, ” filed September 20, 2018, assigned to the assignee hereof, and expressly incorporated by reference in its entirety herein.

BACKGROUND

The following relates generally to wireless communications, and more specifically to polar coding.

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

In some wireless communications systems, wireless devices may utilize error-correcting codes (e.g., polar codes) for encoding transmissions, such as physical downlink control channel (PDCCH) transmissions. These devices may also implement combining information from multiple transmissions corresponding to a same mother code to improve decoding. However, such a process may require maintaining the same aggregation level and sending identical bits for all re-transmissions of PDCCH information to guarantee that soft- combining of the transmissions is supported. Accordingly, the system may not adapt to changing channel conditions between each PDCCH transmission for the same mother code. Furthermore, receiving devices (e.g., UEs) cannot achieve any incremental redundancy (IR) gain from the re-transmissions.

SUMMARY

The described techniques relate to improved methods, systems, devices, and apparatuses that support a polar code design for physical downlink control channel (PDCCH) re-transmission. Generally, the described techniques provide for soft-combining of multiple PDCCH transmissions for improved decoding at a user equipment (UE) . In a wireless system, a base station may polar encode downlink control information (DCI) to obtain a set of mother code bits and may load the mother code bits into a circular buffer. The base station may select a first set of coded bits from the circular buffer for transmission in a first PDCCH transmission. Furthermore, the base station may select a second set of coded bits from the circular buffer for re-transmission in a second PDCCH transmission. These two sets of coded bits may correspond to two different ranges of bits in the circular buffer, where the two ranges are contiguous. For example, the base station may start selecting the second set of coded bits from the circular buffer where it ended selection of the first set of coded bits. Additionally, the base station may adaptively change the aggregation level for the second transmission based on changing channel conditions. Accordingly, the base station may select a new codeword size based on the updated aggregation level but may reuse the same set of mother code bits loaded in the circular buffer. A receiving device (e.g., a UE) may receive the first and second transmissions and may combine information (e.g., log-likelihood ratios (LLRs) ) from the transmissions to improve decoding. For example, soft-combining the LLRs for two transmissions corresponding to different bits from a same mother code may result in incremental redundancy (IR) gain during the decoding process.

A method for wireless communications is described. The method may include performing a polar encoding process on a set of information bits to determine a set of mother code bits, loading the set of mother code bits into a circular buffer, determining a first set of coded bits for transmission of the set of information bits, where the first set of coded bits corresponds to bits of the circular buffer in a first range from a first starting point to a first ending point of the circular buffer, and transmitting the first set of coded bits in a first transmission. The method may further include determining a second set of coded bits different from the first set of coded bits for re-transmission of the set of information bits, where the second set of coded bits corresponds to bits of the circular buffer in a second range from a second starting point to a second ending point of the circular buffer, where the second range and the first range are contiguous on the circular buffer, and transmitting the second set of coded bits in a second transmission.

An apparatus for wireless communications is described. The apparatus may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to perform a polar encoding process on a set of information bits to determine a set of mother code bits, load the set of mother code bits into a circular buffer, determine a first set of coded bits for transmission of the set of information bits, where the first set of coded bits corresponds to bits of the circular buffer in a first range from a first starting point to a first ending point of the circular buffer, and transmit the first set of coded bits in a first transmission. The instructions may be further executable by the processor to cause the apparatus to determine a second set of coded bits different from the first set of coded bits for re-transmission of the set of information bits, where the second set of coded bits corresponds to bits of the circular buffer in a second range from a second starting point to a second ending point of the circular buffer, where the second range and the first range are contiguous on the circular buffer, and transmit the second set of coded bits in a second transmission.

Another apparatus for wireless communications is described. The apparatus may include means for performing a polar encoding process on a set of information bits to determine a set of mother code bits, loading the set of mother code bits into a circular buffer, determining a first set of coded bits for transmission of the set of information bits, where the first set of coded bits corresponds to bits of the circular buffer in a first range from a first starting point to a first ending point of the circular buffer, and transmitting the first set of coded bits in a first transmission. The apparatus may further include means for determining a second set of coded bits different from the first set of coded bits for re-transmission of the set of information bits, where the second set of coded bits corresponds to bits of the circular buffer in a second range from a second starting point to a second ending point of the circular buffer, where the second range and the first range are contiguous on the circular buffer, and transmitting the second set of coded bits in a second transmission.

A non-transitory computer-readable medium storing code for wireless communications is described. The code may include instructions executable by a processor to perform a polar encoding process on a set of information bits to determine a set of mother code bits, load the set of mother code bits into a circular buffer, determine a first set of coded bits for transmission of the set of information bits, where the first set of coded bits corresponds to bits of the circular buffer in a first range from a first starting point to a first ending point of the circular buffer, and transmit the first set of coded bits in a first transmission. The code may further include instructions executable by the processor to determine a second set of coded bits different from the first set of coded bits for re-transmission of the set of information bits, where the second set of coded bits corresponds to bits of the circular buffer in a second range from a second starting point to a second ending point of the circular buffer, where the second range and the first range are contiguous on the circular buffer, and transmit the second set of coded bits in a second transmission.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining a first aggregation level for the first transmission, where a size of the first set of coded bits may be based on the first aggregation level, and determining a second aggregation level for the second transmission, where a size of the second set of coded bits may be based on the second aggregation level.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining a mother code size for the set of mother code bits based on the first aggregation level.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the first aggregation level for the first transmission is different than the second aggregation level for the second transmission and the mother code size for the set of mother code bits is the same for both the first transmission and the second transmission. In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the mother code size may be determined further based on a size of the set of information bits.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the second aggregation level is equal to the first aggregation level and the size of the second set of coded bits is equal to the size of the first set of coded bits. In other examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the second aggregation level is greater than the first aggregation level and the size of the second set of coded bits is greater than the size of the first set of coded bits. In yet other examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the second aggregation level is lower than the first aggregation level and the size of the second set of coded bits is less than the size of the first set of coded bits.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, determining the first aggregation level and determining the second aggregation level may include identifying a channel quality measurement corresponding to a channel for the first transmission, where the first aggregation level may be based on the identified channel quality measurement, and identifying an updated channel quality measurement corresponding to the channel for the second transmission, where the second aggregation level may be based on the identified updated channel quality measurement.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the channel quality measurement, the updated channel quality measurement, or both may be based on a received sounding reference signal (SRS) , a received periodic or aperiodic channel quality indicator (CQI) , a channel estimation procedure, or a combination thereof.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the first set of coded bits and the second set of coded bits may be collected in a same direction along the circular buffer. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the first starting point, the first ending point, or both of the circular buffer may be based on a shortening process, puncturing process, repetition process, or combination thereof.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the first set of coded bits, the second set of coded bits, or both include subsets of the set of mother code bits. In other examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the first set of coded bits, the second set of coded bits, or both include the set of mother code bits and a repeated portion of the set of mother code bits.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, determining the second set of coded bits different from the first set of coded bits for re-transmission of the set of information bits may include operations, features, means, or instructions for receiving a negative acknowledgment (NACK) message in response to the first transmission and determining to transmit the second transmission based on the NACK message.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the first transmission and the second transmission include PDCCH transmissions.

A method of wireless communications is described. The method may include receiving, in a first transmission associated with a set of information bits, first information corresponding to a first set of coded bits of a first candidate codeword, where the first set of coded bits corresponds to bits of a circular buffer in a first range from a first starting point to a first ending point of the circular buffer, the circular buffer associated with a mother code length, and receiving, in a second transmission associated with the set of information bits, second information corresponding to a second set of coded bits of a second candidate codeword, where the second set of coded bits corresponds to bits of the circular buffer in a second range from a second starting point to a second ending point of the circular buffer, where the second range and the first range are contiguous on the circular buffer. The method may further include combining the first information and the second information to obtain combined information, performing a polar decoding process on the combined information according to the mother code length, and determining the set of information bits based on the polar decoding process.

An apparatus for wireless communications is described. The apparatus may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to receive, in a first transmission associated with a set of information bits, first information corresponding to a first set of coded bits of a first candidate codeword, where the first set of coded bits corresponds to bits of a circular buffer in a first range from a first starting point to a first ending point of the circular buffer, the circular buffer associated with a mother code length, and receive, in a second transmission associated with the set of information bits, second information corresponding to a second set of coded bits of a second candidate codeword, where the second set of coded bits corresponds to bits of the circular buffer in a second range from a second starting point to a second ending point of the circular buffer, where the second range and the first range are contiguous on the circular buffer. The instructions may be further executable by the processor to cause the apparatus to combine the first information and the second information to obtain combined information, perform a polar decoding process on the combined information according to the mother code length, and determine the set of information bits based on the polar decoding process.

Another apparatus for wireless communications is described. The apparatus may include means for receiving, in a first transmission associated with a set of information bits, first information corresponding to a first set of coded bits of a first candidate codeword, where the first set of coded bits corresponds to bits of a circular buffer in a first range from a first starting point to a first ending point of the circular buffer, the circular buffer associated with a mother code length, and receiving, in a second transmission associated with the set of information bits, second information corresponding to a second set of coded bits of a second candidate codeword, where the second set of coded bits corresponds to bits of the circular buffer in a second range from a second starting point to a second ending point of the circular buffer, where the second range and the first range are contiguous on the circular buffer. The apparatus may further include means for combining the first information and the second information to obtain combined information, performing a polar decoding process on the combined information according to the mother code length, and determining the set of information bits based on the polar decoding process.

A non-transitory computer-readable medium storing code for wireless communications is described. The code may include instructions executable by a processor to receive, in a first transmission associated with a set of information bits, first information corresponding to a first set of coded bits of a first candidate codeword, where the first set of coded bits corresponds to bits of a circular buffer in a first range from a first starting point to a first ending point of the circular buffer, the circular buffer associated with a mother code length, and receive, in a second transmission associated with the set of information bits, second information corresponding to a second set of coded bits of a second candidate codeword, where the second set of coded bits corresponds to bits of the circular buffer in a second range from a second starting point to a second ending point of the circular buffer, where the second range and the first range are contiguous on the circular buffer. The code may further include instructions executable by the processor to combine the first information and the second information to obtain combined information, perform a polar decoding process on the combined information according to the mother code length, and determine the set of information bits based on the polar decoding process.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, combining the first information and the second information to obtain the combined information may include operations, features, means, or instructions for soft-combining a first set of LLRs corresponding to the first information with a second set of LLRs corresponding to the second information to obtain a combined set of LLRs corresponding to the combined information.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, soft-combining the first set of LLRs corresponding to the first information with the second set of LLRs corresponding to the second information further may include operations, features, means, or instructions for adding LLRs from the first set of LLRs to LLRs from the second set of LLRs that correspond to same positions in the circular buffer.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the first set of LLRs corresponds to a first subset of bits of the circular buffer, the second set of LLRs corresponds to a second subset of bits of the circular buffer and the combined set of LLRs may have a length equal to the mother code length based on the soft-combining.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for performing an unsuccessful polar decoding process on the first information, where performing the polar decoding process on the combined information may be based on the unsuccessful polar decoding process.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting a NACK message in response to the first transmission based on the unsuccessful polar decoding process, where the second transmission may be received based on the NACK message.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the first candidate codeword corresponds to a first aggregation level and a size of the first set of coded bits may be based on the first aggregation level and the second candidate codeword corresponds to a second aggregation level and a size of the second set of coded bits may be based on the second aggregation level. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the mother code length may be based on the first aggregation level.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the first aggregation level is different than the second aggregation level. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the mother code length may be further based on a size of the set of information bits.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the first aggregation level may be based on a channel quality measurement corresponding to a channel for the first transmission and the second aggregation level may be based on an updated channel quality measurement corresponding to the channel for the second transmission.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGs. 1 and 2 illustrate examples of wireless communications systems that support polar code designs for physical downlink control channel (PDCCH) re-transmission in accordance with aspects of the present disclosure.

FIG. 3 illustrates an example of a device that supports a polar code design for PDCCH re-transmission in accordance with aspects of the present disclosure.

FIGs. 4A, 4B, and 4C illustrate examples of circular buffer procedures that support a polar code design for PDCCH re-transmission in accordance with aspects of the present disclosure.

FIG. 5 illustrates an example of a process flow that supports a polar code design for PDCCH re-transmission in accordance with aspects of the present disclosure.

FIGs. 6 and 7 show block diagrams of devices that support a polar code design for PDCCH re-transmission in accordance with aspects of the present disclosure.

FIG. 8 shows a block diagram of a PDCCH polar code manager that supports a polar code design for PDCCH re-transmission in accordance with aspects of the present disclosure.

FIG. 9 shows a diagram of a system including a device that supports a polar code design for PDCCH re-transmission in accordance with aspects of the present disclosure.

FIGs. 10 and 11 show block diagrams of devices that support a polar code design for PDCCH re-transmission in accordance with aspects of the present disclosure.

FIG. 12 shows a block diagram of a PDCCH polar code manager that supports a polar code design for PDCCH re-transmission in accordance with aspects of the present disclosure.

FIG. 13 shows a diagram of a system including a device that supports a polar code design for PDCCH re-transmission in accordance with aspects of the present disclosure.

FIGs. 14 through 18 show flowcharts illustrating methods that support a polar code design for PDCCH re-transmission in accordance with aspects of the present disclosure.

DETAILED DESCRIPTION

In some wireless communications systems (e.g., fifth generation (5G) enhanced mobile broadband (eMBB) systems) , wireless devices may utilize error-correcting codes, such as polar codes, for encoding transmissions. For example, base stations may perform polar coding to encode physical downlink control channel (PDCCH) transmissions, and user equipment (UEs) may perform polar decoding processes to decode the PDCCH information. In some cases, a base station may transmit multiple PDCCH transmissions for the same set of downlink control information (DCI) bits for improved decoding reliability at the UE. Each of these PDCCH transmissions (e.g., the original PDCCH transmission and a PDCCH re-transmission) may contain a different set of coded bits for the DCI bits. That is, when a base station encodes the DCI bits to obtain a set of encoded bits (i.e., mother code bits) , the base station may perform rate-matching on these mother code bits to determine which bits to transmit. To support variable aggregation levels and incremental redundancy (IR) at a receiving UE, the base station may use different ranges of bits from these mother code bits for transmission in the different PDCCH transmissions.

A base station transmitting control information may determine a first aggregation level for the PDCCH based on channel conditions or channel quality measurements. The base station may select a number of coded bits for transmission based on this aggregation level. Additionally, the base station may determine a size of a mother code to use for polar encoding based on the aggregation level, the number of coded bits for transmission, the number of information bits to encode, or some combination of these parameters. The base station may encode the information bits corresponding to DCI into mother code bits using a polar code. These mother code bits may be loaded into a bit buffer (e.g., a circular buffer) which the base station may use for selecting coded bits for transmission. For example, starting at a pre-determined starting point and moving along the circular buffer according to a set direction (e.g., in a first direction corresponding to a successive cancellation (SC) decoding order for the polar code or a second direction that is opposite the first direction) , the base station may select a number of bits corresponding to the determined number of coded bits for transmission. The base station may transmit these coded bits for transmission in a first PDCCH transmission to a receiving device (e.g., a UE) .

The base station may determine to transmit a re-transmission of the PDCCH information in a second PDCCH transmission. This determination may be based on receiving a negative acknowledgment (NACK) from the UE, based on not receiving a positive acknowledgment (ACK) from the UE, based on a configuration of the base station or the UE, or based on some combination of these. For the re-transmission, the base station may measure the channel (or receive channel measurements from the UE) and determine an updated aggregation level for the re-transmission. In some cases, this updated aggregation level may be the same as the first aggregation level. However, in other cases, the updated aggregation level may be higher or lower than the first aggregation level. The base station may determine an updated number of coded bits for transmission based on this updated aggregation level. However, the base station may maintain the same mother code size (e.g., corresponding to the first aggregation level, the first number of coded bits, or both) to support soft-combining at a receiving device. The base station may reuse the circular buffer loaded with the mother code bits for this re-transmission.

The base station may transmit a different set of coded bits in the second PDCCH transmission as compared to the first PDCCH transmission. However, both sets of bits may correspond to the same information bits and are selected from the same set of mother code bits loaded in the circular buffer. Rather than starting at the same starting point as for the first transmission, the base station may select the coded bits for the second transmission from the circular buffer starting where the first set of selected coded bits ended. In this way, the range of bits from the circular buffer used for the second transmission may be contiguous to the range of bits used for the first transmission. By selecting contiguous sets of bits for the first and second transmissions, a UE receiving the transmissions may achieve IR gains during the decoding process by soft-combining information from the two transmissions. In this way, the polar code design described herein may support improved decoding reliability at a UE for PDCCH information. Additionally, the base station may adaptively adjust the aggregation levels for PDCCH re-transmissions according to current channel conditions.

Aspects of the disclosure are initially described in the context of wireless communications systems. Additional aspects are described with reference to a device for polar encoding and decoding, circular buffer procedures, and a process flow. Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to a polar code design for PDCCH re-transmission.

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

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

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

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

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

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

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

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

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

Base stations 105 may communicate with the core network 130 and with one another. For example, base stations 105 may interface with the core network 130 through backhaul links 132 (e.g., via an S1, N2, N3, or other interface) . Base stations 105 may communicate with one another over backhaul links 134 (e.g., via an X2, Xn, or other interface) either directly (e.g., directly between base stations 105) or indirectly (e.g., via core network 130) .

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Some wireless communications systems 100 may support polar encoding of PDCCH transmissions from a base station 105 to one or more UEs 115. The PDCCH transmissions may contain encoded DCI bits (e.g., polar encoded DCI bits) indicating control information for a UE 115. In some cases, a base station 105 may transmit multiple PDCCH transmissions for the same set of DCI bits for improved decoding at the UE 115. For example, each of these PDCCH transmissions (e.g., the original PDCCH transmission and one or more PDCCH re-transmissions) may contain a different set of coded bits for the DCI bits. That is, when a base station 105 encodes the DCI bits to obtain a set of encoded bits (i.e., mother code bits) , the base station 105 may perform rate-matching on these mother code bits to determine which bits to transmit. To support both chase combining and IR at a receiving UE 115, the base station 105 may use different ranges of bits from these mother code bits for transmission in the different PDCCH transmissions.

In one specific example, the base station 105 may load a bit buffer (e.g., a circular buffer) with the mother code bits and may select bits out of the bit buffer-starting at a pre-determined starting point or a starting point that is based on the bits selected for a previous PDCCH transmission-until the base station 105 has selected the correct number of bits for a determined codeword size. Selecting the correct number of bits may involve the base station 105 selecting a subset of the bits from the bit buffer or selecting one or more full revolutions of bits from the bit buffer such that the resulting codeword contains at least some repeated mother code bits. For each PDCCH re-transmission, the base station 105 may start selecting bits from the buffer at an index where the base station 105 ended the bit selection process for the previous PDCCH transmission. For each PDCCH re-transmission, the base station 105 may measure the downlink channel and adaptively adjust an aggregation level for transmission according to the current channel quality or conditions, but the base station 105 may reuse the same set of mother code bits in order to support soft-combining at a receiving UE 115. A UE 115 receiving the multiple PDCCH transmissions may combine the received information to improve the decoding reliability for the PDCCH transmissions and may determine the correct DCI bits based on the combined decoding process.

FIG. 2 illustrates an example of a wireless communications system 200 that supports a polar code design for PDCCH re-transmission in accordance with aspects of the present disclosure. The wireless communications system 200 may be an example of a wireless communications system 100 as described with reference to FIG. 1. The wireless communications system 200 may include base station 105-a and UE 115-a, which may be examples of the corresponding devices described with reference to FIG. 1. Base station 105-a may provide network coverage for geographic area 110-a and may communicate with UE 115-a. For example, base station 105-a may transmit control information and data to UE 115-a on the downlink 205. In some cases, base station 105-a may encode a PDCCH transmission 210 using an error-correcting code, such as a polar code, and may transmit the PDCCH transmission 210 on the downlink 205 to UE 115-a. Base station 105-a may additionally transmit one or more PDCCH re-transmissions 215 to UE 115-a for improved decoding reliability at UE 115-a.

In some systems (e.g., systems operating in a 5G eMBB scenario) , base stations 105 and UEs 115 may handle PDCCH transmissions 210 encoded using polar codes. For example, base station 105-a may determine a set of information bits for transmission, where the information bits indicate DCI. Base station 105-a may polar encode the set of information bits to obtain a set of mother code bits. The size of the set of mother code bits may be based on the aggregation level for the PDCCH transmission 210. For example, base station 105-a may select an aggregation level to use for transmission based on the downlink 205 channel (e.g., based on a set of channel condition thresholds and a measured, indicated, or estimated channel condition for the downlink 205 channel) . The selected aggregation level may correspond to a certain size of codeword that can be transmitted by base station 105-a, a certain size of mother code for encoding, or both. For example, an aggregation level one (AL1) transmission may use a shorter mother code length and a shorter codeword length than an aggregation level four (AL4) transmission.

Base station 105-a may load the determined set of mother code bits into a circular buffer. The size of the circular buffer can correspond to the size of the mother code. In some cases, the mother code bits are loaded into the circular buffer according to an order for decoding of bit channels of the polar code corresponding to the set of mother code bits. The mother code bits may be selected from the circular buffer in such a manner to achieve puncturing or repetition. For example, base station 105-a may use puncturing or repetition for rate-matching a transmission to a size of an aggregation level that is different from the size of the mother code. That is, base station 105-a may transmit a set of coded bits of a different size than the set of mother code bits. Base station 105-a may select the coded bits for transmission from the circular buffer and may transmit the selected bits in a polar encoded PDCCH transmission 210. In some cases (e.g., if the number of bits for transmission is less than the mother code size) , base station 105-a may select a subset of the mother code bits from the circular buffer. In other cases (e.g., if the number of bits for transmission is greater than the mother code size) , base station 105-a may select at least the entire set of mother code bits and may additionally select a set of repeated mother code bits for transmission.

UE 115-a may receive the PDCCH transmission 210 and may attempt to decode the information contained in the transmission. In some cases, UE 115-a may fail to decode the PDCCH transmission 210 (e.g., due to poor channel quality, consistent or bursty interference on the channel, etc. ) . To improve the reliability of the polar decoding process at UE 115-a, base station 105-a may transmit a PDCCH re-transmission 215 on the downlink 205 channel. The PDCCH transmission 210 and the PDCCH re-transmission 215 may support soft-combining at UE 115-a, which can achieve an IR gain at UE 115-a for the decoding process. Base station 105-a may use a same set of mother code bits for selecting the codewords for the PDCCH transmission 210 and the PDCCH re-transmission 215 in order to support soft-combining, as the coded bits for different mother codes may not support soft-combining at a receiving device (e.g., even if the different mother codes are determined from a same set of information bits) . As such, base station 105-a may reuse the circular buffer loaded with the set of mother code bits for the PDCCH re-transmission 215.

Despite keeping the mother code the same for the PDCCH transmission 210 and the PDCCH re-transmission 215, base station 105-a may adaptively change the aggregation level for the re-transmission. For example, base station 105-a may determine an updated channel quality measurement for the downlink 205 channel and may select an updated aggregation level for the PDCCH re-transmission 215 adaptive to any changes to the channel. While base station 105-a may not change the size of the mother code according to this updated aggregation level, base station 105-a may change the size of the codeword for transmission. For example, base station 105-a may select a different number of coded bits from the circular buffer for the PDCCH re-transmission 215 than was selected for the PDCCH transmission 210. Additionally, base station 105-a may select different ranges of bits for transmission from the circular buffer to achieve IR gain at a receiving device. In one example, to support selecting different ranges of bits, base station 105-a may select bits from the circular buffer starting at a first starting point and ending at a first ending point for the PDCCH transmission 210 and may select bits starting at a second starting point for the PDCCH re-transmission 215, where the second starting point is equal to or contiguous to the first ending point. This allows the ranges of bits selected for the PDCCH transmission 210 and for the PDCCH re-transmission 215 to be contiguous in the circular buffer of mother code bits. These ranges may or may not overlap on the circular buffer depending on the size of the mother code and the lengths of the PDCCH transmission 210 and PDCCH re-transmission 215 codewords.

Base station 105-b may transmit the PDCCH re-transmission 215 to UE 115-a on the downlink 205 channel. UE 115-a may receive the PDCCH re-transmission 215 and may combine information from the PDCCH re-transmission 215 with information received in the PDCCH transmission 210. For example, UE 115-a may determine log-likelihood ratios (LLRs) for each of the transmissions and may combine the LLRs to determine a combined set of LLRs. UE 115-a may use these combined LLRs for the polar decoding process. In some cases, based on the combined information, UE 115-a may successfully decode the transmissions and may determine the set of information bits encoded in the PDCCH transmissions.

FIG. 3 illustrates an example of a device 300 that supports a polar code design for PDCCH re-transmission in accordance with aspects of the present disclosure. In some examples, the device 300 may be implemented by aspects of a

wireless communications system

100 or 200. The device 300 may be any device within a wireless communications system that performs an encoding or decoding process (e.g., using an error-correcting code, such as a polar code) . For example, device 300 may be an example of a UE 115 or a base station 105 as described with reference to FIGs. 1 and 2. A base station 105 transmitting a polar encoded PDCCH transmission may be an example of a device 300 including at least a memory 305, an encoder 310, and a transmitter 315. A UE 115 receiving the polar encoded PDCCH transmission may be an example of a device 300 including at least a receiver 315, a decoder 310, and a memory 305.

As illustrated, device 300 may include a memory 305, an encoder/decoder 310, and a transmitter/receiver 315. First bus 320 may connect memory 305 to encoder/decoder 310 and second bus 325 may connect encoder/decoder 310 to transmitter/receiver 315. In some cases, device 300 may have data stored in memory 305 to be transmitted to another device, such as a UE 115 or base station 105. To initiate the transmission process, device 300 may retrieve from memory 305 the data for transmission. For a PDCCH transmission, the data for transmission may include downlink control data for a UE 115 or a set of UEs 115. The data may include a number of payload bits, ‘A, ’ which may be 1s or 0s, provided from memory 305 to encoder/decoder 310 via first bus 320. In some cases, these payload bits may be combined with a number of error checking bits (e.g., cyclic redundancy check (CRC) bits) , ‘C, ’ to form a total set of information bits, ‘A+C. ’ The number of information bits may be represented as a value ‘K, ’ as shown (e.g., K=A+C) . For PDCCH transmissions, this number of information bits, K, or the number of payload bits, A, may be based on the selected DCI format. The encoder/decoder 310 may implement a polar code with a block length, ‘N, ’ for encoding the information bits, where N may be different than or the same as K. Such a polar code may be referred to as an (N, K) polar code. In some cases, the bits not allocated as information bits (e.g., N –K bits) may be assigned as frozen bits or parity check bits. Frozen bits may be bits with a default value known to both the encoding and decoding devices 300 (e.g., bits with a default bit value of 0) . Parity check bits may be calculated based on one or more information bits K and may support early termination of a decoding process.

The encoder 310 may perform the polar encoding process on the K information bits to determine a set of mother code bits of length N. The number of mother code bits, N, in this resulting mother code may be a power of 2 to support the polar encoding process. Some possible mother code sizes include N=32, 64, 128, 256, 512, or 1024 bits, among other mother code sizes. However, the transmitter 315 may transmit a set of coded bits with a size, ‘E, ’ that can be different from the size of the set of polar encoded bits in the mother code, N. In some cases, the number of coded bits for transmission is based on an aggregation level for the transmission. The encoder 310 may select the number of mother code bits N and a corresponding polar code of block length N based on the determined aggregation level, the number of information bits for transmission, or both.

For example, the device 300 may determine the mother code size N based on a set of equations, rules, or lookup tables. In one example, equations for determining the mother code size N may be based on the number of information bits K (e.g., for a PDCCH transmission, the downlink control information (DCI) size) , the number of coded bits for transmission E (e.g., which in turn may be based on the channel conditions, aggregation level, or both) , a minimum coding rate, ‘R _min, ’ supported by the device 300 or encoder 310, a maximum power of two, ‘n _max, ’ corresponding to a maximum mother code size supported by the device 300 or encoder 310, or a combination of these input parameters. The device 300 may determine the mother code size N according to:

If

and K/E＜9/16, then

else

end if, (1)

n=min {n ₁, n ₂, n _max} , (3)

N=2 ⁿ, (4)

where the minimum supported coding rate may equal 1/8 (i.e., R _min=1/8) and the maximum power of two for the maximum mother code size may equal 9 (i.e., n _max=9 for a maximum mother code size of 512 bits) .

If the number of coded bits for transmission are pre-defined for different aggregation levels, then these equations may be converted into a set rules for different combinations of aggregation level and number of information bits. In one specific example, the number of coded bits for transmission for a device 300 may be 108 for AL1, 216 for aggregation level two (AL2) , 432 for AL4, 864 for aggregation level eight (AL8) , and 1728 for aggregation level sixteen (AL16) . In this example, based on the above equations and limits of R _min=1/8 and n _max=9 (i.e., N _max=512) , the mother code size N equals 128 for AL1, 256 for AL2 or for AL4, AL8, and AL16 if the number of information bits K is less than 32, and 512 for AL4, AL8, and AL16 if the number of information bits K is greater than or equal to 32. In this way, the encoder 310 may receive a set of information bits and an aggregation level for transmission (e.g., based on a current channel quality or other channel conditions) , and the encoder 310 may determine a mother code size N for the polar encoding process.

The device 300 (e.g., at the transmitter 315 or encoder 310) may load these N polar encoded bits into a circular buffer of size N and may use the circular buffer to determine the E coded bits for transmission. For example, if E＜N, the device 300 may select a subset of the mother code bits in the circular buffer for transmission. If E=N, the device 300 may select the full set of mother code bits for transmission. If E＞N, the device 300 may select the full set of mother code bits and an additional portion of repeated mother code bits for transmission. The transmitter 315 may transmit these E coded bits for transmission over the channel (e.g., the channel measured to determine the aggregation level for the transmission) to another device 300.

In some cases, the transmitter 315 may additionally transmit a number of re-transmissions of the encoded information bits to the receiving device 300. The device 300 may re-transmit the information based on receiving a NACK message from the receiving device, based on not receiving an ACK message from the receiving device (e.g., during a monitoring window) , or based on a configuration of the device 300. For example, some devices 300 may automatically transmit one or more re-transmissions for a same set of information bits for improved reliability. In some cases, this automatic re-transmission may be based on the channel conditions (e.g., if a channel quality is below a certain channel quality threshold, the device 300 may automatically re-transmit encoded information bits) . In some cases, the re-transmissions may be the same as the original transmission. For example, the device 300 may re-send the same coded bits in a second transmission as in the first transmission to support chase combining at a receiving device 300. However, in other cases, the device 300 may transmit a different set of coded bits in the second transmission than in the first transmission to achieve IR gains at the receiving device 300. For example, the device 300 may select a first range of bits from the circular buffer for the first transmission and may select a second range of bits contiguous to the first range of bits from the circular buffer for the re-transmission. If these ranges overlap for a portion of the circular buffer, this re-transmission technique supports both chase combining and IR at a receiving device 300. The transmitter 315 may transmit the first transmission and the re-transmission (s) to the receiving device 300, and the receiving device 300 may receive the transmissions at a receiver 315 and may pass the received information along to a decoder 310 for polar decoding.

In some wireless systems, encoder/decoder 310 may be an example of an SC or a successive cancellation list (SCL) decoder. A UE 115 or base station 105 may receive a transmission including a codeword at receiver 315 and may send the transmission to the SCL decoder (e.g., encoder/decoder 310) . The SCL decoder may determine input LLRs for the bit channels of the received codeword. During decoding, the SCL decoder may determine decoded LLRs based on these input LLRs, where the decoded LLRs correspond to each bit channel of the polar code. These decoded LLRs may be referred to as bit metrics. In some cases, if the LLR is zero or a positive value, the SCL decoder may determine the corresponding bit is a 0 bit, and a negative LLR may correspond to a 1 bit. The SCL decoder may use the bit metrics to determine the decoded bit values.

The SCL decoder may employ multiple concurrent SC decoding processes. Each SC decoding process may decode the codeword sequentially (e.g., in order of the bit channel indices, in a U-domain) . Due to the combination of multiple SC decoding processes, the SCL decoder may calculate multiple decoding path candidates. For example, an SCL decoder of list size ‘L’ (i.e., the SCL decoder has L SC decoding processes) may calculate L decoding path candidates, and a corresponding reliability metric (e.g., a path metric) for each decoding path candidate. The path metric may represent a reliability of a decoding path candidate or a probability that the corresponding decoding path candidate is the correct set of decoded bits. The path metric may be based on the determined bit metrics and the bit values selected at each bit channel. The SCL decoder may have a number of levels equal to the number of bit channels in the mother code length. At each level (e.g., for information bits) , each decoding path candidate may select either a 0 bit or a 1 bit based on a path metric of the 0 bit and the 1 bit. The SCL decoder may select a decoding path candidate based on the path metrics and may output the bits corresponding to the selected decoding path as the decoded sets of bits. For example, the SCL decoder may select the decoding paths with the highest path metrics for error checking, and the decoder 310 may determine a successfully decoded path candidate based on a result of the error checking process.

In some cases, the decoder 310 (e.g., an SC or SCL decoder) may support soft-combining of transmissions for improved decoding. For example, if a transmitter/receiver 315 of a device 300 receives one or more re-transmissions for the same set of information bits using the same mother code, the transmitter/receiver 315 or decoder 310 may combine information received in the original transmission and any number of the re-transmissions to improve the likelihood of successfully decoding the information bits. This combining of information may involve soft-combining the input LLRs for the different transmissions to determine a set of combined LLRs. If a first transmission and a re-transmission include different coded bits (e.g., due to the transmitting device 300 using two different ranges of mother code bits from the circular buffer) , the receiver 315 or decoder 310 may determine LLRs for a greater number of bits than the E transmitted bits. That is, if N＞E＞N/2, with a single re-transmission and using contiguous ranges of bits from the circular buffer, a receiving device 300 may determine input LLRs for the entire set of mother code bits of size N. The receiving device 300 may additionally determine more reliable input LLRs for at least a portion of the bits due to chase combining. For example, if the receiver 315 receives input LLRs for bit channels corresponding to a same bit of the set of mother code bits in the transmissions, the receiver 315 may add the two input LLRs to determine a more reliable combined input LLR, and the decoder 310 may use the more reliable combined input LLR for polar decoding. The decoder 310 may determine the set of information bits based on combining the information received in the original transmission with information received in one or more re-transmissions, and in some cases the device 300 may store this received set of information bits of size K in the memory 305.

FIGs. 4A, 4B, and 4C illustrate examples of circular buffer procedures 400 that support polar code designs for PDCCH re-transmissions in accordance with aspects of the present disclosure. The circular buffer procedures 400 are illustrated with example buffer lengths N and codeword sizes E for illustrative purposes. However, many other buffer lengths N and codeword sizes E may support similar circular buffer procedures 400. For example, in one specific case, a system may support values of N=128 bits and E=108 bits for AL1, N=256 bits and E=216 bits for AL2, N=256 bits or N=512 bits and E=432 bits for AL4, N=256 bits or N=512 bits and E=864 bits for AL8, and N=256 bits or N= 512 bits and E=1728 bits for AL16.

In FIG. 4A, the circular buffer procedure 400-acorresponds to determining coded bits for a PDCCH re-transmission at a same aggregation level. For example, a wireless device, such as a base station 105, may determine a set of information bits for transmission. These information bits may be examples of DCI bits or may be based on DCI bits for a PDCCH transmission. The base station 105 may additionally determine an aggregation level for transmission. In some cases, the aggregation level may be determined based on channel conditions. For example, the base station 105 may determine the channel conditions for the PDCCH and may select a relatively higher aggregation level if the channel conditions are poor (e.g., below one or more thresholds, such as a channel quality threshold) or a relatively lower aggregation level if the channel conditions are good (e.g., above one or more thresholds, such as a channel quality threshold) . In one specific example, the base station 105 may store four channel quality threshold values in memory and may compare a current channel condition measurement to the four threshold values. If the measured current channel condition value is above the highest threshold, the base station 105 may select AL1 for transmission on the measured channel. If the measured value is below the highest threshold but above the second highest threshold, the base station 105 may select AL2. Similarly, the base station 105 may select AL4, AL8, or AL16 based on comparing the measured current channel condition value to the other channel quality threshold values. These channel quality threshold values may be static or dynamic values (e.g., based on the information to transmit, capabilities or configurations of the base station 105 or a receiving device, the number of re-transmissions already sent, etc. ) . The base station 105 may determine a number of coded bits for transmission, E, based on the aggregation level. Additionally or alternatively, the base station 105 may determine a number of mother code bits for polar encoding, N. The base station 105 may polar encode the information bits to determine a set of N mother code bits 405. The base station 105 may load these N mother code bits 405 into a circular buffer 410 to determine the coded bits for transmission.

For a first transmission, the base station 105 may select a first set of coded bits 425-a for transmission from the mother code bits loaded in the circular buffer 410. How the bits are loaded into the buffer or which order the bits are selected may be based on a rate-matching procedure used by the base station 105. For example, depending on whether the base station 105 performs shortening (e.g., reduction of the effective mother code length) , the base station 105 may adjust which bits are loaded into which slots in the circular buffer 410. The base station 105 may select E coded bits for transmission, where E is based on the aggregation level for the transmission. In some cases, the base station 105 may select the first E bits loaded into the circular buffer 410, starting at a first starting point 415-a of the circular buffer and ending with a first ending point 420-a. The range defined by this first starting point 415-a and this first ending point 420-a has a length of E bits and can be shorter or longer than the mother code length, N (or, in some specific examples, may be the same length as the mother code length N) . As illustrated, the value of E may be smaller than the value of N. As such, the selected first set of coded bits 425-a may be a subset of the set of N mother code bits 405 loaded into the circular buffer 410 (e.g., where the subset is defined by the range from the first starting point 415-a of the circular buffer 410 to the first ending point 420-a of the circular buffer 410) . The base station 105 (e.g., an encoder or transmitter of the base station 105) may select the bits for transmission from the circular buffer in a pre-determined direction (e.g., where clockwise in the illustrated example may correspond to an SC decoding direction-or counterclockwise) . The base station 105 may transmit the first set of coded bits 425-a for transmission over the channel.

The base station 105 may determine to transmit a second transmission containing a second set of coded bits 425-b for transmission. The base station 105 may perform this second transmission based on receiving a NACK in response to the first set of coded bits 425-a, based on the absence of an ACK in response to the first set of coded bits 425-a, or based on a configuration of the base station 105 (e.g., the base station 105 may be configured to automatically perform one or more re-transmissions for a set of information bits) . The base station 105 may determine an updated aggregation level for the channel. For example, the aggregation level for the PDCCH may change based on changing channel conditions. In a first example, the aggregation level for the second transmission may be the same as the aggregation level for the first transmission. As such, the number of coded bits 425 for transmission for the first transmission and the re-transmission may stay the same.

The base station 105 may use the same set of N mother code bits 405 loaded into the circular buffer 410 for the re-transmission. By using the same set of N mother code bits 405, the base station 105 may ensure that the two transmissions support soft-combining at a receiver. In this first example, the size of the mother code and the corresponding mother code bits correspond to the aggregation level for both the first transmission and the second transmission, as the two transmissions share a same aggregation level. However, rather than transmit the same set of coded bits 425, the base station 105 may select a different set of coded bits 425-b for transmission in the second transmission. To support a maximum or optimized IR gain with the re-transmission, the base station 105 may select a range of bits for transmission that is contiguous with the range of bits for the first transmission. The base station 105 may select a set of coded bits 425-b according to a second starting point 415-b and a second ending point 420-b. The second starting point 415-b may be equal to or contiguous to the first ending point 420-a. For example, if the first ending point 420-a for the first transmission is at bit index 15, the second starting point 415-b for the second transmission can be at bit index 16 in the circular buffer 410. As illustrated, the first ending point 420-a is after bit index 15 (i.e., before bit index 16) and the second starting point 415-b is correspondingly before bit index 16 (i.e., after bit index 15) . The second ending point 420-b is selected based on the second starting point 415-b and the size, E, of the set of coded bits 425-b for re-transmission. The base station 105 may collect the data from the circular buffer 410 for transmission in the same direction along the circular buffer 410 for the first transmission and the second transmission. For example, because the base station 105 selected the first set of coded bits 425-a for the first transmission in a clockwise direction from the first starting point 415-auntil the E number of coded bits were selected (e.g., until the first ending point 420-a) , the base station 105 may similarly select the second set of coded bits 425-b for the second transmission in the clockwise direction from the second starting point 415-b until E coded bits are selected (e.g., until the second ending point 420-b) . In some cases, the base station 105 may store a marker to indicate the first ending point 420-a and may access the first ending point 420-abased on this marker when preparing the second set of coded bits 425-b for transmission. The base station may transmit the second set of E coded bits 425-b as a re-transmission of the same set of polar encoded information bits, where the original transmission (i.e., the first transmission) and the re-transmission (i.e., the second transmission) contain different sets of coded bits 425.

A wireless device (e.g., a UE 115) receiving both the first transmission and the second transmission may combine information received in each of the transmissions to improve the polar decoding process. As illustrated in FIG. 4A, by combining information from the first set of coded bits 425-a and the second set of coded bits 425-b, a receiving device may determine information about each bit in the set of N mother code bits 405, even though the number of coded bits, E, included in each transmission is less than N. For example, by starting the range of bits selected from the circular buffer 410 at different points in the circular buffer 410, the base station 105 transmits each bit in the circular buffer 410 in at least one of the transmissions, and some bits are transmitted in both of the transmissions. In this way, the receiving device may determine input LLRs corresponding to each bit in the set of mother code bits by combining the information received in the two transmissions and may polar decode the combined information to determine the encoded set of information bits. For example, as illustrated, the receiving device (e.g., a UE 115 receiving PDCCH transmissions) may identify one input LLR for a set of bits (e.g., bits corresponding to bit indices 8–15 of the circular buffer 410 in the first set of coded bits 425-a and bits corresponding to bit indices 16–23 of the circular buffer 410 in the second set of coded bits 425-b) and two input LLRs for another set of bits (e.g., bits corresponding to bit indices 0–7 of the circular buffer 410 in the first and second sets of coded bits 425-a and 425-b) . The receiving device may add the input LLRs received for a same bit to determine a combined input LLR and may use the combined input LLR in the polar decoding process. In some cases, these combined input LLRs may be referred to as “additive” LLRs. By soft-combining the received input LLRs for the two transmissions, the receiving device may obtain an additional IR gain, as incremental coded bits (e.g., the bits corresponding to bit indices 16–23 of the circular buffer 410) are selected for the second transmission that were not selected for the first transmission. Additionally, the receiving device may obtain a chase combining gain by combining the input LLRs for the repeated sections of the circular buffer 410 transmitted in each of the two sets of coded bits 425 (e.g., the bits corresponding to bit indices 0–7 of the circular buffer 410) .

In FIG. 4B, the circular buffer procedure 400-b corresponds to determining coded bits for a PDCCH re-transmission at a greater aggregation level. A transmitting device (e.g., a base station 105) may determine to transmit a first polar encoded transmission for a set of K information bits. The base station 105 may load a circular buffer 410 with a set of N mother code bits 405 determined based on the information bits and may transmit a first transmission according to a first aggregation level as described above with reference to FIG. 4A. Additionally, the base station 105 may determine to transmit a second transmission that is a re-transmission for the set of K information bits. The base station 105 may determine an updated channel quality measurement for the second transmission, for example, based on a received sounding reference signal (SRS) from a receiving device, a received periodic or aperiodic channel quality indicator (CQI) from the receiving device, a channel estimation procedure performed by the base station 105, or a combination of these or some similar channel quality determination procedures. The base station 105 may determine an aggregation level for the second transmission based on the updated channel quality measurement for the transmission channel. In a second example, the channel quality may deteriorate between the first transmission and the second transmission as indicated by a change in the channel quality measurement. In this example, the base station 105 may determine a second aggregation level for the second transmission that is greater than the first aggregation level for the first transmission. Alternatively, the base station 105 may determine to re-transmit using a higher aggregation level based on a receiving device (e.g., a UE 115) failing to decode the first transmission. In this case, the base station 105 may use different aggregation levels despite no significant change to the channel conditions (or independent of any change to the channel conditions) .

This higher aggregation level for the second transmission may indicate or correspond to a larger mother code size, N ₂ (e.g., where N ₂ is larger than the mother code size used to load the circular buffer 410, N) and a larger size of coded bits 425-c for re-transmission, E ₂ (e.g., where E ₂ is larger than the number of coded bits 425-a for the first transmission, E) . For example, the number of coded bits, the number of mother code bits, or both may be determined according to a set of equations, rules, or lookup tables that depend on the aggregation level. However, rather than using this larger mother code size, N ₂, the base station 105 may reuse the circular buffer 410 loaded with N mother code bits 410 for the first transmission. In this way, the first and second transmissions may use the same mother code size and the same mother code bits despite the different aggregation levels, supporting soft-combining of the transmissions at a receiver or decoder.

As described above, the second starting point 415-b for selecting the second set of coded bits 425-c for the second transmission is equal or contiguous to the first ending point 420-a for selecting the first set of coded bits 425-a for the first transmission. The base station 105 may select bits from the circular buffer 410 for transmission starting at the second starting point 415-b until E ₂ bits have been selected. This may correspond to the range of bits starting at the second starting point 415-b and ending with the second ending point 420-c. The bits for the second transmission may be selected from the circular buffer 410 in the same direction (e.g., clockwise) as for the first transmission. As illustrated, in some cases, the value of E ₂ may be greater than the value of N (i.e., the number of coded bits 425-c for transmission is greater than the number of mother code bits loaded into the circular buffer 410) . In these cases, the second set of coded bits 425-c for re-transmission may include the full set of N mother code bits 405 and an additional portion of repeated mother code bits. As illustrated, the second set of coded bits 425-c for re-transmission may include every bit from the circular buffer 410 at least once and may include the bits corresponding to bit indices 16 and 17 twice (e.g., once at the beginning of the codeword and once at the end of the codeword) .

A receiving device (e.g., a UE 115) receiving the first set of coded bits 425-a and the second set of coded bits 425-c may perform a similar procedure as described above with reference to FIG. 4A to obtain a soft-combining gain from the two transmissions. For example, because the same mother code and mother code size is used for each transmission (and despite the difference in the number of actually transmitted bits) , the receiving device may combine information from each of the transmissions to determine combined information about the full set of mother code bits. For example, by combining the input LLRs for the received first and second transmissions, the UE 115 may determine additive LLRs for the bits corresponding to bit indices 0–15 based on combining information from the two transmissions and for the bits corresponding to bit indices 16 and 17 based on repeated LLRs in the second transmission. Additionally, the UE 115 may determine input LLRs for the bits corresponding to bit indices 18–23 based on the second transmission. The UE 115 may use this combined information for polar decoding and may improve the reliability of determining the polar encoded set of information bits based on combining the input LLRs for the two transmissions of different sizes.

In FIG. 4C, the circular buffer procedure 400-c corresponds to determining coded bits for a PDCCH re-transmission at a lower aggregation level. A transmitting device (e.g., a base station 105) may determine to transmit a first polar encoded transmission for a set of K information bits. The base station 105 may load a circular buffer 410 with a set of N mother code bits 405 determined based on the information bits and may transmit a first transmission according to a first aggregation level as described above with reference to FIG. 4A. Additionally, the base station 105 may determine to transmit a second transmission that is a re-transmission for the set of K information bits. The base station 105 may determine an updated channel quality measurement for the second transmission and may adaptively determine an aggregation level for the second transmission based on this updated channel quality measurement. In a third example, the channel quality may improve between the first transmission and the second transmission as indicated by a change in the channel quality measurement. In this example, the base station 105 may determine a second aggregation level for the second transmission that is lower than the first aggregation level for the first transmission.

This lower aggregation level for the second transmission may indicate or correspond to a smaller mother code size, N ₂ (e.g., where N ₂ is smaller than the mother code size used to load the circular buffer 410, N) and a smaller size of coded bits 425-d for re-transmission, E ₂ (e.g., where E ₂ is smaller than the number of coded bits 425-a for the first transmission, E) . For example, the number of coded bits, the number of mother code bits, or both may be determined according to the set of equations, rules, or lookup tables that depend on the aggregation level. However, rather than using the smaller mother code size, N ₂, the base station 105 may reuse the circular buffer 410 loaded with N mother code bits 410 for the first transmission. In this way, the first and second transmissions may use the same mother code size and the same mother code bits despite the different aggregation levels, supporting soft-combining of the transmissions at a receiving device.

As described above, the second starting point 415-b for selecting the second set of coded bits 425-d for the second transmission may be equal or contiguous to the first ending point 420-a for selecting the first set of coded bits 425-a for the first transmission. The base station 105 may select bits from the circular buffer 410 for transmission starting at the second starting point 415-b until E ₂ bits have been selected. This may correspond to the range of bits starting at the second starting point 415-b and ending with the second ending point 420-d. The bits for the second transmission may be selected from the circular buffer 410 in the same direction (e.g., clockwise) as for the first transmission. As illustrated, the second set of coded bits 425-d for re-transmission may include fewer bits than the first set of coded bits 425-a for transmission. However, based on the second starting point 415-b being different than the first starting point 415-a, the two transmissions support IR at a receiving device. In some cases, the two transmissions may also support chase combining of some bits.

The receiving device (e.g., a UE 115) receiving the first set of coded bits 425-a and the second set of coded bits 425-d may perform a similar procedure as described above with respect to FIG. 4A to obtain a soft-combining gain from the two transmissions. For example, because the same mother code and mother code size is used for each transmission (and despite the difference in the number of actually transmitted bits) , the receiving device may combine information from each of the transmissions to determine combined information about the set of mother code bits. For example, by combining the input LLRs for the received first and second transmissions, the UE 115 may determine incremental LLRs for the bits corresponding to bit indices 16–23 that were not indicated in the first transmission. Additionally, in the specific case illustrated, the UE 115 may determine additive LLRs for the bits corresponding to bit indices 0–3 based on combining information from the two transmissions. In some cases (e.g., if E+E ₂＜N) , the UE 115 may not receive input LLRs corresponding to each bit in the mother code when combining the first and second transmissions. In these cases, the UE 115 may still achieve an IR gain from combining the two transmission (but may not achieve a chase combining gain) , improving the reliability of decoding. In some examples, the base station 105 may transmit further re-transmissions such that the UE 115 can determine input LLRs for each bit in the circular buffer 410.

In an alternative technique to the one described above with respect to FIG. 4C, the system may not use a lower aggregation level for the second transmission than is used for the first transmission. For example, even if the base station 105 identifies improved channel conditions for the re-transmission, the base station 105 may select an aggregation level that is at least as high as the aggregation level selected for the first transmission. Operating such that the aggregation level of the second transmission is not less than the aggregation level of the first transmission may ensure that the block error rate (BLER) for the combined transmissions meets a certain BLER threshold.

Additionally, as illustrated, in each circular buffer procedure 400 described the same first transmission is sent by the base station 105. In some cases, the base station 105 may use a set first starting point 415-a and a set direction for selecting the bits from the buffer to support backwards compatibility. That is, a UE 115 not configured to receive the re-transmission at a different aggregation level or with a different range of bits may still correctly receive the first set of coded bits 425-ain the first transmission and may attempt to decode at least this first transmission to determine the information bits.

FIG. 5 illustrates an example of a process flow 500 that supports a polar code design for PDCCH re-transmission in accordance with aspects of the present disclosure. The process flow 500 may include a base station 105-b and a UE 115-b, which may be examples of the corresponding devices described with reference to FIGs. 1 and 2. Additionally, base station 105-b and UE 115-b may be examples of devices 300 as described with reference to FIG. 3. Alternative examples of the following may be implemented, where some steps are performed in a different order than described or are not performed at all. In some cases, steps may include additional features not mentioned below, or further steps may be added.

At 505, base station 105-b may determine a first aggregation level for a first transmission. In some cases, base station 105-b may determine the first aggregation level by identifying a channel quality measurement corresponding to a channel for the first transmission and selecting the aggregation level based on the channel quality measurement. This channel quality measurement may be based on a received SRS (e.g., received from UE 115-b) , a received periodic or aperiodic CQI, a channel estimation procedure performed by base station 105-b, or some combination of these.

At 510, base station 105-b may perform a polar encoding process on a set of information bits (e.g., corresponding to DCI bits) to determine a set of mother code bits. Base station 105-b may load the set of mother code bits into a circular buffer. In some cases, base station 105-b determines the mother code size based on the first aggregation level. The mother code size may additionally be determined based on a size of the set of information bits.

At 515, base station 105-b may determine a first set of coded bits for transmission of the set of information bits. Base station 105-b may select the coded bits for transmission from the circular buffer in a first range from a first starting point to a first ending point of the circular buffer. In some cases, the size of the first set of coded bits is based on the first aggregation level. This first set of coded bits can contain a subset of the mother code bits, the entire set of mother code bits, or the entire set of mother code bits with a repeated portion of the set of mother code bits. In some examples, the first starting point, the first ending point, or both may be based on a shortening process, a puncturing process, a repetition process, or some combination of these or other rate-matching processes.

At 520, base station 105-b may transmit the first set of coded bits in a first transmission. This first transmission may be an example of a PDCCH transmission. UE 115-b may receive, in this first transmission, a first candidate codeword, including first information corresponding to the first set of coded bits. In some cases, at 525, UE 115-b may attempt to polar decode the first transmission based on the received first information. The polar decoding process may be unsuccessful, and UE 115-b may transmit a NACK message at 530 in response to the first transmission received from base station 105-b.

At 535, base station 105-b may determine to re-transmit the set of information bits. In some cases, base station 105-b may automatically re-transmit the set of information bits in a second transmission based on a configuration of the base station 105-b or the identified channel conditions. In some other cases, base station 105-b may trigger the re-transmission due to receiving a NACK message from UE 115-b or due to not receiving an ACK message from UE 115-b during an ACK monitoring window. Base station 105-b may determine a second aggregation level for the second transmission. In some cases, the second aggregation level is determined based on identifying an updated channel quality measurement corresponding to the channel for the second transmission. The second aggregation level can be the same as the first aggregation level or can be different than the first aggregation level (e.g., higher or lower than the first aggregation level) .

At 540, base station 105-b may determine a second set of coded bits different from the first set of coded bits for the re-transmission by selecting coded bits for transmission from the circular buffer in a second range from a second starting point to a second ending point of the circular buffer. This second range may be contiguous to the first range on the circular buffer, such that the second starting point is the same as or contiguous to the first ending point. The size of the second set of coded bits may be based on the second aggregation level. If the second aggregation level is equal to the first aggregation level, the size of the second set of coded bits may be equal to the size of the first set of coded bits. If the second aggregation level is greater than the first aggregation level, the size of the second set of coded bits may be greater than the size of the first set of coded bits. If the second aggregation level is lower than the first aggregation level, the size of the second set of coded bits may be less than the size of the first set of coded bits. The bits for the first set of coded bits and for the second set of coded bits may be selected from the circular buffer according to a same direction (e.g., clockwise or counter-clockwise) . As with the first set of coded bits, this second set of coded bits can contain a subset of the mother code bits, the entire set of mother code bits, or the entire set of mother code bits with a repeated portion of the set of mother code bits.

At 545, base station 105-b may transmit the second set of coded bits in a second transmission to UE 115-b. This second transmission may be an example of a PDCCH re-transmission. UE 115-b may receive, in this second transmission, a second candidate codeword, including second information corresponding to the second set of coded bits.

At 550, UE 115-b may combine the first information and the second information to obtain combined information. This combining may involve UE 115-b soft-combining a first set of LLRs corresponding to the first information with a second set of LLRs corresponding to the second information to obtain a combined set of LLRs corresponding to the combined information. UE 115-b may combine the LLRs by adding LLRs from the first set of LLRs to LLRs from the second set of LLRs that correspond to same positions in the circular buffer (e.g., in a chase combining procedure) . In some cases, the first set of LLRs may correspond to a first subset of bits from the circular buffer, the second set of LLRs may correspond to a second subset of bits from the circular buffer, and the combined set of LLRs may have a length equal to the mother code length based on the soft-combining procedure (e.g., including an IR procedure) , where the combined LLRs correspond to the full set of bits in the circular buffer.

At 555, UE 115-b may perform a polar decoding process on the combined information (e.g., the combined set of LLRs) according to the mother code length. UE 115-b may determine the set of information bits based on the polar decoding procedure. In some cases, UE 115-b may fail to determine the information bits when decoding just the first PDCCH transmission but may successfully determine the information bits based on the chase combining and IR gains achieved from soft-combining the information from the PDCCH transmission with the information from the PDCCH re-transmission and decoding this combined information.

FIG. 6 shows a block diagram 600 of a device 605 that supports a polar code design for PDCCH re-transmission in accordance with aspects of the present disclosure. The device 605 may be an example of aspects of a UE 115 as described herein. The device 605 may include a receiver 610, a PDCCH polar code manager 615, and a transmitter 620. The device 605 may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses) .

The receiver 610 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to a polar code design for PDCCH re-transmission, etc. ) . Information may be passed on to other components of the device 605. The receiver 610 may be an example of aspects of the transceiver 920 described with reference to FIG. 9. The receiver 610 may utilize a single antenna or a set of antennas.

The PDCCH polar code manager 615 may receive, in a first transmission associated with a set of information bits, first information corresponding to a first set of coded bits of a first candidate codeword, where the first set of coded bits corresponds to bits of a circular buffer in a first range from a first starting point to a first ending point of the circular buffer, the circular buffer associated with a mother code length. The PDCCH polar code manager 615 may additionally receive, in a second transmission associated with the set of information bits, second information corresponding to a second set of coded bits of a second candidate codeword, where the second set of coded bits corresponds to bits of the circular buffer in a second range from a second starting point to a second ending point of the circular buffer, where the second range and the first range are contiguous on the circular buffer. The PDCCH polar code manager 615 may combine the first information and the second information to obtain combined information, perform a polar decoding process on the combined information according to the mother code length, and determine the set of information bits based on the polar decoding process. The PDCCH polar code manager 615 may be an example of aspects of the PDCCH polar code manager 910 described herein.

The actions performed by the PDCCH polar code manager 615 as described herein may be implemented to realize one or more potential advantages. For example, combining information from the first and second transmissions in order to perform a polar decoding process may allow a UE 115 to achieve chase combining and IR gains. Specifically, using different ranges from the circular buffer for the PDCCH transmissions may support the UE 115 receiving supplemental mother code bits (e.g., a full set of mother code bits) and receiving multiple input LLRs corresponding to a same mother code bit. The chase combining and IR gains may result in improved decoding reliability at the UE 115.

Based on performing the polar decoding process on combined information, a processor of the UE 115 (e.g., a processor controlling the receiver 610, the PDCCH polar code manager 615, the transmitter 620, etc. ) may reduce processing resources used for downlink reception. For example, the polar code design for PDCCH re-transmissions described herein may improve decoding reliability at the UE 115. As such, the UE 115 may reduce the number of reception and decoding processes performed to successfully receive information from a base station 105 (e.g., by reducing the number of PDCCH retransmissions) . Reducing the number of reception and decoding processes may reduce a number of times the processor ramps up processing power and turns on processing units to handle downlink message reception and decoding. Furthermore, reducing the number of re-transmission processes performed by the base station 105 may reduce the signaling overhead on the downlink control channel. In addition, the base station 105 may reduce the amount of resources used for transmissions (e.g., using a lower aggregation level) based on increased reliability of reception by the UE 115, in some cases.

The PDCCH polar code manager 615, or its sub-components, may be implemented in hardware, code (e.g., software or firmware) executed by a processor, or any combination thereof. If implemented in code executed by a processor, the functions of the PDCCH polar code manager 615, or its sub-components may be executed by a general-purpose processor, a digital signal processor (DSP) , an application-specific integrated circuit (ASIC) , a field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in the present disclosure.

The PDCCH polar code manager 615, or its 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 components. In some examples, the PDCCH polar code manager 615, or its sub-components, may be a separate and distinct component in accordance with various aspects of the present disclosure. In some examples, the PDCCH polar code manager 615, or its sub-components, may be combined with one or more other hardware components, including but not limited to an input/output (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.

The transmitter 620 may transmit signals generated by other components of the device 605. In some examples, the transmitter 620 may be collocated with a receiver 610 in a transceiver module. For example, the transmitter 620 may be an example of aspects of the transceiver 920 described with reference to FIG. 9. The transmitter 620 may utilize a single antenna or a set of antennas.

FIG. 7 shows a block diagram 700 of a device 705 that supports a polar code design for PDCCH re-transmission in accordance with aspects of the present disclosure. The device 705 may be an example of aspects of a device 605 or a UE 115 as described herein. The device 705 may include a receiver 710, a PDCCH polar code manager 715, and a transmitter 740. The device 705 may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses) .

The receiver 710 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to a polar code design for PDCCH re-transmission, etc. ) . Information may be passed on to other components of the device 705. The receiver 710 may be an example of aspects of the transceiver 920 described with reference to FIG. 9. The receiver 710 may utilize a single antenna or a set of antennas.

The PDCCH polar code manager 715 may be an example of aspects of the PDCCH polar code manager 615 as described herein. The PDCCH polar code manager 715 may include a codeword reception component 720, a combining component 725, a polar decoding component 730, and a bit determination component 735. The PDCCH polar code manager 715 may be an example of aspects of the PDCCH polar code manager 910 described herein.

The codeword reception component 720 may receive, in a first transmission associated with a set of information bits, first information corresponding to a first set of coded bits of a first candidate codeword, where the first set of coded bits corresponds to bits of a circular buffer in a first range from a first starting point to a first ending point of the circular buffer, the circular buffer associated with a mother code length. The codeword reception component 720 may additionally receive, in a second transmission associated with the set of information bits, second information corresponding to a second set of coded bits of a second candidate codeword, where the second set of coded bits corresponds to bits of the circular buffer in a second range from a second starting point to a second ending point of the circular buffer, where the second range and the first range are contiguous on the circular buffer.

The combining component 725 may combine the first information and the second information to obtain combined information. The polar decoding component 730 may perform a polar decoding process on the combined information according to the mother code length. The bit determination component 735 may determine the set of information bits based on the polar decoding process.

The transmitter 740 may transmit signals generated by other components of the device 705. In some examples, the transmitter 740 may be collocated with a receiver 710 in a transceiver module. For example, the transmitter 740 may be an example of aspects of the transceiver 920 described with reference to FIG. 9. The transmitter 740 may utilize a single antenna or a set of antennas.

FIG. 8 shows a block diagram 800 of a PDCCH polar code manager 805 that supports a polar code design for PDCCH re-transmission in accordance with aspects of the present disclosure. The PDCCH polar code manager 805 may be an example of aspects of a PDCCH polar code manager 615, a PDCCH polar code manager 715, or a PDCCH polar code manager 910 described herein. The PDCCH polar code manager 805 may include a codeword reception component 810, a combining component 815, a polar decoding component 820, a bit determination component 825, an LLR soft-combining component 830, and a NACK component 835. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses) .

The codeword reception component 810 may receive, in a first transmission associated with a set of information bits, first information corresponding to a first set of coded bits of a first candidate codeword, where the first set of coded bits corresponds to bits of a circular buffer in a first range from a first starting point to a first ending point of the circular buffer, the circular buffer associated with a mother code length. The codeword reception component 810 may additionally receive, in a second transmission associated with the set of information bits, second information corresponding to a second set of coded bits of a second candidate codeword, where the second set of coded bits corresponds to bits of the circular buffer in a second range from a second starting point to a second ending point of the circular buffer, where the second range and the first range are contiguous on the circular buffer.

In some cases, the first candidate codeword corresponds to a first aggregation level and a size of the first set of coded bits is based on the first aggregation level. The second candidate codeword may correspond to a second aggregation level and a size of the second set of coded bits is based on the second aggregation level. In some cases, the mother code length is based on the first aggregation level. In some cases, the mother code length is further based on a size of the set of information bits. In some examples, the first aggregation level is different than the second aggregation level.

In some cases, the second aggregation level is equal to the first aggregation level and the size of the second set of coded bits is equal to the size of the first set of coded bits. In other cases, the second aggregation level is greater than the first aggregation level and the size of the second set of coded bits is greater than the size of the first set of coded bits. In yet other cases, the second aggregation level is lower than the first aggregation level and the size of the second set of coded bits is less than the size of the first set of coded bits.

In some cases, the first aggregation level is based on a channel quality measurement corresponding to a channel for the first transmission and the second aggregation level is based on an updated channel quality measurement corresponding to the channel for the second transmission. The first transmission and the second transmission may be examples of PDCCH transmissions.

The combining component 815 may combine the first information and the second information to obtain combined information. In some cases, combining the first information and the second information to obtain the combined information involves an LLR soft-combining component 830 soft-combining a first set of LLRs corresponding to the first information with a second set of LLRs corresponding to the second information to obtain a combined set of LLRs corresponding to the combined information. In some examples, the LLR soft-combining component 830 may add LLRs from the first set of LLRs to LLRs from the second set of LLRs that correspond to same positions in the circular buffer. In some cases, the first set of LLRs corresponds to a first subset of bits of the circular buffer, the second set of LLRs corresponds to a second subset of bits of the circular buffer, and the combined set of LLRs has a length equal to the mother code length based on the soft-combining.

The polar decoding component 820 may perform a polar decoding process on the combined information according to the mother code length. In some examples, the polar decoding component 820 may perform an unsuccessful polar decoding process on the first information, where performing the polar decoding process on the combined information is based on the unsuccessful polar decoding process. The NACK component 835 may transmit a NACK message in response to the first transmission based on the unsuccessful polar decoding process, where the second transmission is received based on the NACK message.

The bit determination component 825 may determine the set of information bits based on the polar decoding process.

FIG. 9 shows a diagram of a system 900 including a device 905 that supports a polar code design for PDCCH re-transmission in accordance with aspects of the present disclosure. The device 905 may be an example of or include the components of a device 605, a device 705, or a UE 115 as described herein. The device 905 may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including a PDCCH polar code manager 910, an I/O controller 915, a transceiver 920, an antenna 925, memory 930, and a processor 940. These components may be in electronic communication via one or more buses (e.g., bus 945) .

The PDCCH polar code manager 910 may receive, in a first transmission associated with a set of information bits, first information corresponding to a first set of coded bits of a first candidate codeword, where the first set of coded bits corresponds to bits of a circular buffer in a first range from a first starting point to a first ending point of the circular buffer, the circular buffer associated with a mother code length. Furthermore, the PDCCH polar code manager 910 may receive, in a second transmission associated with the set of information bits, second information corresponding to a second set of coded bits of a second candidate codeword, where the second set of coded bits corresponds to bits of the circular buffer in a second range from a second starting point to a second ending point of the circular buffer, where the second range and the first range are contiguous on the circular buffer. The PDCCH polar code manager 910 may combine the first information and the second information to obtain combined information, perform a polar decoding process on the combined information according to the mother code length, and determine the set of information bits based on the polar decoding process.

The I/O controller 915 may manage input and output signals for the device 905. The I/O controller 915 may also manage peripherals not integrated into the device 905. In some cases, the I/O controller 915 may represent a physical connection or port to an external peripheral. In some cases, the I/O controller 915 may utilize an operating system such as

or another known operating system. In other cases, the I/O controller 915 may represent or interact with a modem, a keyboard, a mouse, a touchscreen, or a similar device. In some cases, the I/O controller 915 may be implemented as part of a processor. In some cases, a user may interact with the device 905 via the I/O controller 915 or via hardware components controlled by the I/O controller 915.

The transceiver 920 may communicate bi-directionally, via one or more antennas, wired, or wireless links as described above. For example, the transceiver 920 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver (e.g., a wireless transceiver at a base station 105 or another UE 115) . The transceiver 920 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 925. However, in some cases the device may have more than one antenna 925, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

The memory 930 may include random-access memory (RAM) and read-only memory (ROM) . The memory 930 may store computer-readable, computer-executable code 935 including instructions that, when executed, cause the processor to perform various functions described herein. In some cases, the memory 930 may contain, among other things, a basic I/O system (BIOS) which may control basic hardware or software operation such as the interaction with peripheral components or devices.

The processor 940 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, the processor 940 may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into the processor 940. The processor 940 may be configured to execute computer-readable instructions stored in a memory (e.g., the memory 930) to cause the device 905 to perform various functions (e.g., functions or tasks supporting a polar code design for PDCCH re-transmission) .

The code 935 may include instructions to implement aspects of the present disclosure, including instructions to support wireless communications. The code 935 may be stored in a non-transitory computer-readable medium such as system memory or other type of memory. In some cases, the code 935 may not be directly executable by the processor 940 but may cause a computer (e.g., when compiled and executed) to perform functions described herein.

FIG. 10 shows a block diagram 1000 of a device 1005 that supports a polar code design for PDCCH re-transmission in accordance with aspects of the present disclosure. The device 1005 may be an example of aspects of a base station 105 as described herein. The device 1005 may include a receiver 1010, a PDCCH polar code manager 1015, and a transmitter 1020. The device 1005 may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses) .

The receiver 1010 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to a polar code design for PDCCH re-transmission, etc. ) . Information may be passed on to other components of the device 1005. The receiver 1010 may be an example of aspects of the transceiver 1320 described with reference to FIG. 13. The receiver 1010 may utilize a single antenna or a set of antennas.

The PDCCH polar code manager 1015 may perform a polar encoding process on a set of information bits to determine a set of mother code bits, load the set of mother code bits into a circular buffer, determine a first set of coded bits for transmission of the set of information bits, where the first set of coded bits corresponds to bits of the circular buffer in a first range from a first starting point to a first ending point of the circular buffer, and transmit the first set of coded bits in a first transmission. Furthermore, the PDCCH polar code manager 1015 may determine a second set of coded bits different from the first set of coded bits for re-transmission of the set of information bits, where the second set of coded bits corresponds to bits of the circular buffer in a second range from a second starting point to a second ending point of the circular buffer, where the second range and the first range are contiguous on the circular buffer and may transmit the second set of coded bits in a second transmission. The PDCCH polar code manager 1015 may be an example of aspects of the PDCCH polar code manager 1310 described herein.

The actions performed by the PDCCH polar code manager 1015 as described herein may be implemented to realize one or more potential advantages. For example, a base station 105 determining coded bits for re-transmissions using a same set of mother code bits but different circular buffer ranges may support chase combining and IR gains at a UE 115. The chase combining and IR gains may result in improved decoding reliability at the UE 115. As such, the base station 105 may reduce a number of re-transmissions used to successfully send DCI to the UE 115 over the downlink control channel.

Based on determining coded bits for re-transmissions using a same set of mother code bits but different circular buffer ranges, a processor of the base station 105 (e.g., a processor controlling the receiver 1010, the PDCCH polar code manager 1015, the transmitter 1020, etc. ) may reduce processing resources used for downlink transmission. For example, the polar code design for PDCCH re-transmissions described herein may improve decoding reliability at the UE 115. As such, the base station 105 may reduce the number of downlink transmission processes performed to successfully send information to the UE 115 (e.g., over a downlink control channel) . Reducing the number of transmission processes may reduce a number of times the processor ramps up processing power and turns on processing units to handle downlink message transmission. Furthermore, reducing the number of re-transmission processes performed by the base station 105 may reduce the signaling overhead on the downlink control channel.

The PDCCH polar code manager 1015, or its sub-components, may be implemented in hardware, code (e.g., software or firmware) executed by a processor, or any combination thereof. If implemented in code executed by a processor, the functions of the PDCCH polar code manager 1015, or its sub-components may be executed by a general-purpose processor, a DSP, an ASIC, an FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in the present disclosure.

The PDCCH polar code manager 1015, or its 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 components. In some examples, the PDCCH polar code manager 1015, or its sub-components, may be a separate and distinct component in accordance with various aspects of the present disclosure. In some examples, the PDCCH polar code manager 1015, or its 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.

The transmitter 1020 may transmit signals generated by other components of the device 1005. In some examples, the transmitter 1020 may be collocated with a receiver 1010 in a transceiver module. For example, the transmitter 1020 may be an example of aspects of the transceiver 1320 described with reference to FIG. 13. The transmitter 1020 may utilize a single antenna or a set of antennas.

FIG. 11 shows a block diagram 1100 of a device 1105 that supports a polar code design for PDCCH re-transmission in accordance with aspects of the present disclosure. The device 1105 may be an example of aspects of a device 1005 or a base station 105 as described herein. The device 1105 may include a receiver 1110, a PDCCH polar code manager 1115, and a transmitter 1140. The device 1105 may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses) .

The receiver 1110 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to a polar code design for PDCCH re-transmission, etc. ) . Information may be passed on to other components of the device 1105. The receiver 1110 may be an example of aspects of the transceiver 1320 described with reference to FIG. 13. The receiver 1110 may utilize a single antenna or a set of antennas.

The PDCCH polar code manager 1115 may be an example of aspects of the PDCCH polar code manager 1015 as described herein. The PDCCH polar code manager 1115 may include a polar encoding component 1120, a buffer loading component 1125, a bit selector 1130, and a codeword transmission component 1135. The PDCCH polar code manager 1115 may be an example of aspects of the PDCCH polar code manager 1310 described herein.

The polar encoding component 1120 may perform a polar encoding process on a set of information bits to determine a set of mother code bits. The buffer loading component 1125 may load the set of mother code bits into a circular buffer.

The bit selector 1130 may determine a first set of coded bits for transmission of the set of information bits, where the first set of coded bits corresponds to bits of the circular buffer in a first range from a first starting point to a first ending point of the circular buffer. The codeword transmission component 1135 may transmit the first set of coded bits in a first transmission.

The bit selector 1130 may additionally determine a second set of coded bits different from the first set of coded bits for re-transmission of the set of information bits, where the second set of coded bits corresponds to bits of the circular buffer in a second range from a second starting point to a second ending point of the circular buffer, and where the second range and the first range are contiguous on the circular buffer. The codeword transmission component 1135 may additionally transmit the second set of coded bits in a second transmission.

The transmitter 1140 may transmit signals generated by other components of the device 1105. In some examples, the transmitter 1140 may be collocated with a receiver 1110 in a transceiver module. For example, the transmitter 1140 may be an example of aspects of the transceiver 1320 described with reference to FIG. 13. The transmitter 1140 may utilize a single antenna or a set of antennas.

FIG. 12 shows a block diagram 1200 of a PDCCH polar code manager 1205 that supports a polar code design for PDCCH re-transmission in accordance with aspects of the present disclosure. The PDCCH polar code manager 1205 may be an example of aspects of a PDCCH polar code manager 1015, a PDCCH polar code manager 1115, or a PDCCH polar code manager 1310 described herein. The PDCCH polar code manager 1205 may include a polar encoding component 1210, a buffer loading component 1215, a bit selector 1220, a codeword transmission component 1225, an aggregation level determination component 1230, a mother code sizing component 1235, a channel measurement component 1240, and a NACK component 1245. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses) .

The polar encoding component 1210 may perform a polar encoding process on a set of information bits to determine a set of mother code bits. The buffer loading component 1215 may load the set of mother code bits into a circular buffer.

The bit selector 1220 may determine a first set of coded bits for transmission of the set of information bits, where the first set of coded bits corresponds to bits of the circular buffer in a first range from a first starting point to a first ending point of the circular buffer. The bit selector 1220 may additionally determine a second set of coded bits different from the first set of coded bits for re-transmission of the set of information bits, where the second set of coded bits corresponds to bits of the circular buffer in a second range from a second starting point to a second ending point of the circular buffer, where the second range and the first range are contiguous on the circular buffer. The first set of coded bits and the second set of coded bits can be collected in a same direction along the circular buffer.

In some cases, the first starting point, the first ending point, or both are based on a shortening process, puncturing process, repetition process, or combination thereof. In some cases, the first set of coded bits, the second set of coded bits, or both include subsets of the set of mother code bits. In other cases, the first set of coded bits, the second set of coded bits, or both include the set of mother code bits and a repeated portion of the set of mother code bits.

The codeword transmission component 1225 may transmit the first set of coded bits in a first transmission and may transmit the second set of coded bits in a second transmission. The first transmission and the second transmission may be examples of PDCCH transmissions.

The aggregation level determination component 1230 may determine a first aggregation level for the first transmission, where a size of the first set of coded bits is based on the first aggregation level, and may determine a second aggregation level for the second transmission, where a size of the second set of coded bits is based on the second aggregation level.

The mother code sizing component 1235 may determine a mother code size for the set of mother code bits based on the first aggregation level. In some cases, the mother code size is determined further based on a size of the set of information bits. In some cases, the first aggregation level for the first transmission is different than the second aggregation level for the second transmission. However, in these cases, the mother code size for the set of mother code bits can be the same for both the first transmission and the second transmission.

In some examples, determining the first and second aggregation levels involves a channel measurement component 1240 identifying a channel quality measurement corresponding to a channel for the first transmission, where the first aggregation level is based on the identified channel quality measurement, and identifying an updated channel quality measurement corresponding to the channel for the second transmission, where the second aggregation level is based on the identified updated channel quality measurement. In some cases, the channel quality measurement, the updated channel quality measurement, or both are based on a received SRS, a received periodic or aperiodic CQI, a channel estimation procedure, or a combination thereof.

In some examples, determining the second set of coded bits is based on a NACK component 1245 receiving a NACK message in response to the first transmission and determining to transmit the second transmission based on the NACK message.

FIG. 13 shows a diagram of a system 1300 including a device 1305 that supports a polar code design for PDCCH re-transmission in accordance with aspects of the present disclosure. The device 1305 may be an example of or include the components of a device 1005, a device 1105, or a base station 105 as described herein. The device 1305 may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including a PDCCH polar code manager 1310, a network communications manager 1315, a transceiver 1320, an antenna 1325, memory 1330, a processor 1340, and an inter-station communications manager 1345. These components may be in electronic communication via one or more buses (e.g., bus 1350) .

The PDCCH polar code manager 1310 may perform a polar encoding process on a set of information bits to determine a set of mother code bits, load the set of mother code bits into a circular buffer, determine a first set of coded bits for transmission of the set of information bits, where the first set of coded bits corresponds to bits of the circular buffer in a first range from a first starting point to a first ending point of the circular buffer, and transmit the first set of coded bits in a first transmission. The PDCCH polar code manager 1310 may additionally determine a second set of coded bits different from the first set of coded bits for re-transmission of the set of information bits, where the second set of coded bits corresponds to bits of the circular buffer in a second range from a second starting point to a second ending point of the circular buffer, and where the second range and the first range are contiguous on the circular buffer, and transmit the second set of coded bits in a second transmission.

The network communications manager 1315 may manage communications with the core network 130 (e.g., via one or more wired backhaul links) . For example, the network communications manager 1315 may manage the transfer of data communications for client devices, such as one or more UEs 115.

The transceiver 1320 may communicate bi-directionally, via one or more antennas, wired, or wireless links as described above. For example, the transceiver 1320 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver (e.g., located at a UE 115) . The transceiver 1320 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 1325. However, in some cases the device may have more than one antenna 1325, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

The memory 1330 may include RAM, ROM, or a combination thereof. The memory 1330 may store computer-readable code 1335 including instructions that, when executed by a processor (e.g., the processor 1340) cause the device to perform various functions described herein. In some cases, the memory 1330 may contain, among other things, a BIOS which may control basic hardware or software operation such as the interaction with peripheral components or devices.

The processor 1340 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, the processor 1340 may be configured to operate a memory array using a memory controller. In some cases, a memory controller may be integrated into processor 1340. The processor 1340 may be configured to execute computer-readable instructions stored in a memory (e.g., the memory 1330) to cause the device 1305 to perform various functions (e.g., functions or tasks supporting a polar code design for PDCCH re-transmission) .

The inter-station communications manager 1345 may manage communications with other base station 105 and may include a controller or scheduler for controlling communications with UEs 115 in cooperation with other base stations 105. For example, the inter-station communications manager 1345 may coordinate scheduling for transmissions to UEs 115 for various interference mitigation techniques such as beamforming or joint transmission. In some examples, the inter-station communications manager 1345 may provide an X2 interface within an LTE/LTE-A wireless communication network technology to provide communication between base stations 105.

The code 1335 may include instructions to implement aspects of the present disclosure, including instructions to support wireless communications. The code 1335 may be stored in a non-transitory computer-readable medium such as system memory or other type of memory. In some cases, the code 1335 may not be directly executable by the processor 1340 but may cause a computer (e.g., when compiled and executed) to perform functions described herein.

FIG. 14 shows a flowchart illustrating a method 1400 that supports a polar code design for PDCCH re-transmission in accordance with aspects of the present disclosure. The operations of method 1400 may be implemented by a base station 105 or its components as described herein. For example, the operations of method 1400 may be performed by a PDCCH polar code manager as described with reference to FIGs. 10 through 13. In some examples, a base station may execute a set of instructions to control the functional elements of the base station to perform the functions described below. Additionally or alternatively, a base station may perform aspects of the functions described below using special-purpose hardware.

At 1405, the base station may perform a polar encoding process on a set of information bits to determine a set of mother code bits. The operations of 1405 may be performed according to the methods described herein. In some examples, aspects of the operations of 1405 may be performed by a polar encoding component as described with reference to FIGs. 10 through 13.

At 1410, the base station may load the set of mother code bits into a circular buffer. The operations of 1410 may be performed according to the methods described herein. In some examples, aspects of the operations of 1410 may be performed by a buffer loading component as described with reference to FIGs. 10 through 13.

At 1415, the base station may determine a first set of coded bits for transmission of the set of information bits, where the first set of coded bits corresponds to bits of the circular buffer in a first range from a first starting point to a first ending point of the circular buffer. The operations of 1415 may be performed according to the methods described herein. In some examples, aspects of the operations of 1415 may be performed by a bit selector as described with reference to FIGs. 10 through 13.

At 1420, the base station may transmit the first set of coded bits in a first transmission. The operations of 1420 may be performed according to the methods described herein. In some examples, aspects of the operations of 1420 may be performed by a codeword transmission component as described with reference to FIGs. 10 through 13.

At 1425, the base station may determine a second set of coded bits different from the first set of coded bits for re-transmission of the set of information bits, where the second set of coded bits corresponds to bits of the circular buffer in a second range from a second starting point to a second ending point of the circular buffer, and where the second range and the first range are contiguous on the circular buffer. The operations of 1425 may be performed according to the methods described herein. In some examples, aspects of the operations of 1425 may be performed by a bit selector as described with reference to FIGs. 10 through 13.

At 1430, the base station may transmit the second set of coded bits in a second transmission. The operations of 1430 may be performed according to the methods described herein. In some examples, aspects of the operations of 1430 may be performed by a codeword transmission component as described with reference to FIGs. 10 through 13.

FIG. 15 shows a flowchart illustrating a method 1500 that supports a polar code design for PDCCH re-transmission in accordance with aspects of the present disclosure. The operations of method 1500 may be implemented by a base station 105 or its components as described herein. For example, the operations of method 1500 may be performed by a PDCCH polar code manager as described with reference to FIGs. 10 through 13. In some examples, a base station may execute a set of instructions to control the functional elements of the base station to perform the functions described below. Additionally or alternatively, a base station may perform aspects of the functions described below using special-purpose hardware.

At 1505, the base station may determine a first aggregation level for a first transmission, where a size of a first set of coded bits is based on the first aggregation level. The operations of 1505 may be performed according to the methods described herein. In some examples, aspects of the operations of 1505 may be performed by an aggregation level determination component as described with reference to FIGs. 10 through 13.

At 1510, the base station may determine a mother code size for a set of mother code bits based on the first aggregation level. The operations of 1510 may be performed according to the methods described herein. In some examples, aspects of the operations of 1510 may be performed by a mother code sizing component as described with reference to FIGs. 10 through 13.

At 1515, the base station may perform a polar encoding process on a set of information bits to determine the set of mother code bits. The operations of 1515 may be performed according to the methods described herein. In some examples, aspects of the operations of 1515 may be performed by a polar encoding component as described with reference to FIGs. 10 through 13.

At 1520, the base station may load the set of mother code bits into a circular buffer. The operations of 1520 may be performed according to the methods described herein. In some examples, aspects of the operations of 1520 may be performed by a buffer loading component as described with reference to FIGs. 10 through 13.

At 1525, the base station may determine the first set of coded bits for transmission of the set of information bits, where the first set of coded bits corresponds to bits of the circular buffer in a first range from a first starting point to a first ending point of the circular buffer. The operations of 1525 may be performed according to the methods described herein. In some examples, aspects of the operations of 1525 may be performed by a bit selector as described with reference to FIGs. 10 through 13.

At 1530, the base station may transmit the first set of coded bits in the first transmission. The operations of 1530 may be performed according to the methods described herein. In some examples, aspects of the operations of 1530 may be performed by a codeword transmission component as described with reference to FIGs. 10 through 13.

At 1535, the base station may determine a second aggregation level for a second transmission, where a size of a second set of coded bits is based on the second aggregation level. The operations of 1535 may be performed according to the methods described herein. In some examples, aspects of the operations of 1535 may be performed by an aggregation level determination component as described with reference to FIGs. 10 through 13.

At 1540, the base station may determine the second set of coded bits different from the first set of coded bits for re-transmission of the set of information bits, where the second set of coded bits corresponds to bits of the circular buffer in a second range from a second starting point to a second ending point of the circular buffer, and where the second range and the first range are contiguous on the circular buffer. The operations of 1540 may be performed according to the methods described herein. In some examples, aspects of the operations of 1540 may be performed by a bit selector as described with reference to FIGs. 10 through 13.

At 1545, the base station may transmit the second set of coded bits in the second transmission. The operations of 1545 may be performed according to the methods described herein. In some examples, aspects of the operations of 1545 may be performed by a codeword transmission component as described with reference to FIGs. 10 through 13.

FIG. 16 shows a flowchart illustrating a method 1600 that supports a polar code design for PDCCH re-transmission in accordance with aspects of the present disclosure. The operations of method 1600 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 1600 may be performed by a PDCCH polar code manager as described with reference to FIGs. 6 through 9. In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the functions described below. Additionally or alternatively, a UE may perform aspects of the functions described below using special-purpose hardware.

At 1605, the UE may receive, in a first transmission associated with a set of information bits, first information corresponding to a first set of coded bits of a first candidate codeword, where the first set of coded bits corresponds to bits of a circular buffer in a first range from a first starting point to a first ending point of the circular buffer, the circular buffer associated with a mother code length. The operations of 1605 may be performed according to the methods described herein. In some examples, aspects of the operations of 1605 may be performed by a codeword reception component as described with reference to FIGs. 6 through 9.

At 1610, the UE may receive, in a second transmission associated with the set of information bits, second information corresponding to a second set of coded bits of a second candidate codeword, where the second set of coded bits corresponds to bits of the circular buffer in a second range from a second starting point to a second ending point of the circular buffer, where the second range and the first range are contiguous on the circular buffer. The operations of 1610 may be performed according to the methods described herein. In some examples, aspects of the operations of 1610 may be performed by a codeword reception component as described with reference to FIGs. 6 through 9.

At 1615, the UE may combine the first information and the second information to obtain combined information. The operations of 1615 may be performed according to the methods described herein. In some examples, aspects of the operations of 1615 may be performed by a combining component as described with reference to FIGs. 6 through 9.

At 1620, the UE may perform a polar decoding process on the combined information according to the mother code length. The operations of 1620 may be performed according to the methods described herein. In some examples, aspects of the operations of 1620 may be performed by a polar decoding component as described with reference to FIGs. 6 through 9.

At 1625, the UE may determine the set of information bits based on the polar decoding process. The operations of 1625 may be performed according to the methods described herein. In some examples, aspects of the operations of 1625 may be performed by a bit determination component as described with reference to FIGs. 6 through 9.

FIG. 17 shows a flowchart illustrating a method 1700 that supports a polar code design for PDCCH re-transmission in accordance with aspects of the present disclosure. The operations of method 1700 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 1700 may be performed by a PDCCH polar code manager as described with reference to FIGs. 6 through 9. In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the functions described below. Additionally or alternatively, a UE may perform aspects of the functions described below using special-purpose hardware.

At 1705, the UE may receive, in a first transmission associated with a set of information bits, first information corresponding to a first set of coded bits of a first candidate codeword, where the first set of coded bits corresponds to bits of a circular buffer in a first range from a first starting point to a first ending point of the circular buffer, the circular buffer associated with a mother code length. The operations of 1705 may be performed according to the methods described herein. In some examples, aspects of the operations of 1705 may be performed by a codeword reception component as described with reference to FIGs. 6 through 9.

At 1710, the UE may receive, in a second transmission associated with the set of information bits, second information corresponding to a second set of coded bits of a second candidate codeword, where the second set of coded bits corresponds to bits of the circular buffer in a second range from a second starting point to a second ending point of the circular buffer, where the second range and the first range are contiguous on the circular buffer. The operations of 1710 may be performed according to the methods described herein. In some examples, aspects of the operations of 1710 may be performed by a codeword reception component as described with reference to FIGs. 6 through 9.

At 1715, the UE may combine the first information and the second information to obtain combined information by soft-combining a first set of LLRs corresponding to the first information with a second set of LLRs corresponding to the second information to obtain a combined set of LLRs corresponding to the combined information. The operations of 1715 may be performed according to the methods described herein. In some examples, aspects of the operations of 1715 may be performed by an LLR soft-combining component as described with reference to FIGs. 6 through 9.

At 1720, the UE may perform a polar decoding process on the combined information (i.e., the combined LLRs) according to the mother code length. The operations of 1720 may be performed according to the methods described herein. In some examples, aspects of the operations of 1725 may be performed by a polar decoding component as described with reference to FIGs. 6 through 9.

At 1725, the UE may determine the set of information bits based on the polar decoding process. The operations of 1725 may be performed according to the methods described herein. In some examples, aspects of the operations of 1725 may be performed by a bit determination component as described with reference to FIGs. 6 through 9.

FIG. 18 shows a flowchart illustrating a method 1800 that supports a polar code design for PDCCH re-transmission in accordance with aspects of the present disclosure. The operations of method 1800 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 1800 may be performed by a PDCCH polar code manager as described with reference to FIGs. 6 through 9. In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the functions described below. Additionally or alternatively, a UE may perform aspects of the functions described below using special-purpose hardware.

At 1805, the UE may receive, in a first transmission associated with a set of information bits, first information corresponding to a first set of coded bits of a first candidate codeword, where the first set of coded bits corresponds to bits of a circular buffer in a first range from a first starting point to a first ending point of the circular buffer, the circular buffer associated with a mother code length. The operations of 1805 may be performed according to the methods described herein. In some examples, aspects of the operations of 1805 may be performed by a codeword reception component as described with reference to FIGs. 6 through 9.

At 1810, the UE may perform an unsuccessful polar decoding process on the first information. The operations of 1810 may be performed according to the methods described herein. In some examples, aspects of the operations of 1810 may be performed by a polar decoding component as described with reference to FIGs. 6 through 9.

At 1815, the UE may receive, in a second transmission associated with the set of information bits, second information corresponding to a second set of coded bits of a second candidate codeword, where the second set of coded bits corresponds to bits of the circular buffer in a second range from a second starting point to a second ending point of the circular buffer, and where the second range and the first range are contiguous on the circular buffer. The operations of 1815 may be performed according to the methods described herein. In some examples, aspects of the operations of 1815 may be performed by a codeword reception component as described with reference to FIGs. 6 through 9.

At 1820, the UE may combine the first information and the second information to obtain combined information. The operations of 1820 may be performed according to the methods described herein. In some examples, aspects of the operations of 1820 may be performed by a combining component as described with reference to FIGs. 6 through 9.

At 1825, the UE may perform a polar decoding process on the combined information according to the mother code length, where performing the polar decoding process on the combined information is based on the unsuccessful polar decoding process. The operations of 1825 may be performed according to the methods described herein. In some examples, aspects of the operations of 1825 may be performed by a polar decoding component as described with reference to FIGs. 6 through 9.

At 1830, the UE may determine the set of information bits based on the polar decoding process. The operations of 1830 may be performed according to the methods described herein. In some examples, aspects of the operations of 1830 may be performed by a bit determination component as described with reference to FIGs. 6 through 9.

Described below are a number of embodiments of methods, systems or apparatuses including means for implementing methods or realizing apparatuses, non-transitory computer-readable medium storing instructions executable by one or more processors to cause the one or more processors to implement methods, and systems including one or more processors and memory coupled with the one or more processors storing instructions executable by the one or more processors to cause the system or apparatus to implement methods. It is to be understood that these are just some examples of possible embodiments, and other examples will be readily apparent to those skilled in the art without departing from the scope of the disclosure.

Embodiment 1: A method for wireless communications, comprising: receiving, in a first transmission associated with a set of information bits, first information corresponding to a first set of coded bits of a first candidate codeword, where the first set of coded bits corresponds to bits of a circular buffer in a first range from a first starting point to a first ending point of the circular buffer, the circular buffer associated with a mother code length; receiving, in a second transmission associated with the set of information bits, second information corresponding to a second set of coded bits of a second candidate codeword, where the second set of coded bits corresponds to bits of the circular buffer in a second range from a second starting point to a second ending point of the circular buffer, where the second range and the first range are contiguous on the circular buffer; combining the first information and the second information to obtain combined information; performing a polar decoding process on the combined information according to the mother code length; and determining the set of information bits based on the polar decoding process.

Embodiment 2: The method of embodiment 1, where combining the first information and the second information to obtain the combined information comprises: soft-combining a first set of LLRs corresponding to the first information with a second set of LLRs corresponding to the second information to obtain a combined set of LLRs corresponding to the combined information.

Embodiment 3: The method of embodiment 2, where soft-combining the first set of LLRs corresponding to the first information with the second set of LLRs corresponding to the second information further comprises: adding LLRs from the first set of LLRs to LLRs from the second set of LLRs that correspond to same positions in the circular buffer.

Embodiment 4: The method of either of embodiments 2 or 3, where: the first set of LLRs corresponds to a first subset of bits of the circular buffer; the second set of LLRs corresponds to a second subset of bits of the circular buffer; and the combined set of LLRs has a length equal to the mother code length based on the soft-combining.

Embodiment 5: The method of any of embodiments 1 to 4, further comprising: performing an unsuccessful polar decoding process on the first information, where performing the polar decoding process on the combined information may be based on the unsuccessful polar decoding process.

Embodiment 6: The method of embodiment 5, further comprising: transmitting a NACK message in response to the first transmission based on the unsuccessful polar decoding process, where the second transmission may be received based on the NACK message.

Embodiment 7: The method of any of embodiments 1 to 6, where: the first candidate codeword corresponds to a first aggregation level and a size of the first set of coded bits may be based on the first aggregation level; and the second candidate codeword corresponds to a second aggregation level and a size of the second set of coded bits may be based on the second aggregation level.

Embodiment 8: The method of embodiment 7, where the mother code length is based on the first aggregation level.

Embodiment 9: The method of embodiment 8, where the first aggregation level is different than the second aggregation level.

Embodiment 10: The method of either of embodiments 8 or 9, where the mother code length is further based on a size of the set of information bits.

Embodiment 11: The method of either of embodiments 7 or 8, where: the second aggregation level is equal to the first aggregation level; and the size of the second set of coded bits is equal to the size of the first set of coded bits.

Embodiment 12: The method of any of embodiments 7 to 9, where: the second aggregation level is greater than the first aggregation level; and the size of the second set of coded bits is greater than the size of the first set of coded bits.

Embodiment 13: The method of any of embodiments 7 to 9, where: the second aggregation level is lower than the first aggregation level; and the size of the second set of coded bits is less than the size of the first set of coded bits.

Embodiment 14: The method of any of embodiments 7 to 13, where: the first aggregation level may be based on a channel quality measurement corresponding to a channel for the first transmission; and the second aggregation level may be based on an updated channel quality measurement corresponding to the channel for the second transmission.

Embodiment 15: The method of any of embodiments 1 to 14, where the first transmission and the second transmission include PDCCH transmissions.

Embodiment 16: An apparatus comprising at least one means for performing a method of any of embodiments 1 to 15.

Embodiment 17: An apparatus for wireless communications comprising a processor; memory in electronic communication with the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to perform a method of any of embodiments 1 to 15.

Embodiment 18: A non-transitory computer-readable medium storing code for wireless communications, the code comprising instructions executable by a processor to perform a method of any of embodiments 1 to 15.

Embodiment 19: A method for wireless communications, comprising: performing a polar encoding process on a set of information bits to determine a set of mother code bits; loading the set of mother code bits into a circular buffer; determining a first set of coded bits for transmission of the set of information bits, where the first set of coded bits corresponds to bits of the circular buffer in a first range from a first starting point to a first ending point of the circular buffer; transmitting the first set of coded bits in a first transmission; determining a second set of coded bits different from the first set of coded bits for re-transmission of the set of information bits, where the second set of coded bits corresponds to bits of the circular buffer in a second range from a second starting point to a second ending point of the circular buffer, where the second range and the first range are contiguous on the circular buffer; and transmitting the second set of coded bits in a second transmission.

Embodiment 20: The method of embodiment 19, further comprising: determining a first aggregation level for the first transmission, where a size of the first set of coded bits may be based on the first aggregation level; and determining a second aggregation level for the second transmission, where a size of the second set of coded bits may be based on the second aggregation level.

Embodiment 21: The method of embodiment 20, further comprising: determining a mother code size for the set of mother code bits based on the first aggregation level.

Embodiment 22: The method of embodiment 21, where: the first aggregation level for the first transmission is different than the second aggregation level for the second transmission; and the mother code size for the set of mother code bits is the same for both the first transmission and the second transmission.

Embodiment 23: The method of either of embodiments 21 or 22, where the mother code size may be determined further based on a size of the set of information bits.

Embodiment 24: The method of either of embodiments 20 or 21, where: the second aggregation level is equal to the first aggregation level; and the size of the second set of coded bits is equal to the size of the first set of coded bits.

Embodiment 25: The method of any of embodiments 20 to 23, where: the second aggregation level is greater than the first aggregation level; and the size of the second set of coded bits is greater than the size of the first set of coded bits.

Embodiment 26: The method of any of embodiments 20 to 23, where: the second aggregation level is lower than the first aggregation level; and the size of the second set of coded bits is less than the size of the first set of coded bits.

Embodiment 27: The method of any of embodiments 20 to 26, where determining the first aggregation level and determining the second aggregation level comprise: identifying a channel quality measurement corresponding to a channel for the first transmission, where the first aggregation level is based on the identified channel quality measurement; and identifying an updated channel quality measurement corresponding to the channel for the second transmission, where the second aggregation level is based on the identified updated channel quality measurement.

Embodiment 28: The method of embodiment 27, where the channel quality measurement, the updated channel quality measurement, or both may be based on a received SRS, a received periodic or aperiodic CQI, a channel estimation procedure, or a combination thereof.

Embodiment 29: The method of any of embodiments 19 to 28, where the first set of coded bits and the second set of coded bits are collected in a same direction along the circular buffer.

Embodiment 30: The method of any of embodiments 19 to 29, where the first starting point, the first ending point, or both of the circular buffer are based on a shortening process, puncturing process, repetition process, or combination thereof.

Embodiment 31: The method of any of embodiments 19 to 30, where the first set of coded bits, the second set of coded bits, or both include subsets of the set of mother code bits.

Embodiment 32: The method of any of embodiments 19 to 30, where the first set of coded bits, the second set of coded bits, or both include the set of mother code bits and a repeated portion of the set of mother code bits.

Embodiment 33: The method of any of embodiments 19 to 32, where determining the second set of coded bits different from the first set of coded bits for re-transmission of the set of information bits comprises: receiving a NACK message in response to the first transmission; and determining to transmit the second transmission based on the NACK message.

Embodiment 34: The method of any of embodiments 19 to 33, where the first transmission and the second transmission include PDCCH transmissions.

Embodiment 35: An apparatus comprising at least one means for performing a method of any of embodiments 19 to 34.

Embodiment 36: An apparatus for wireless communications comprising a processor; memory in electronic communication with the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to perform a method of any of embodiments 19 to 34.

Embodiment 37: A non-transitory computer-readable medium storing code for wireless communications, the code comprising instructions executable by a processor to perform a method of any of embodiments 19 to 34.

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

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

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

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

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

Information and signals described herein may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the 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 herein can be implemented using software executed by a processor, hardware, firmware, hardwiring, or combinations of any of these. Features implementing functions may also be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations.

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

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

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

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

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

Claims

A method for wireless communications, comprising:

receiving, in a first transmission associated with a set of information bits, first information corresponding to a first set of coded bits of a first candidate codeword, wherein the first set of coded bits corresponds to bits of a circular buffer in a first range from a first starting point to a first ending point of the circular buffer, the circular buffer associated with a mother code length;

receiving, in a second transmission associated with the set of information bits, second information corresponding to a second set of coded bits of a second candidate codeword, wherein the second set of coded bits corresponds to bits of the circular buffer in a second range from a second starting point to a second ending point of the circular buffer, wherein the second range and the first range are contiguous on the circular buffer;

combining the first information and the second information to obtain combined information;

performing a polar decoding process on the combined information according to the mother code length; and

determining the set of information bits based at least in part on the polar decoding process.
The method of claim 1, wherein combining the first information and the second information to obtain the combined information comprises:

soft-combining a first set of log-likelihood ratios (LLRs) corresponding to the first information with a second set of LLRs corresponding to the second information to obtain a combined set of LLRs corresponding to the combined information.
The method of claim 2, wherein:

the first set of LLRs corresponds to a first subset of bits of the circular buffer;

the second set of LLRs corresponds to a second subset of bits of the circular buffer; and

the combined set of LLRs has a length equal to the mother code length based at least in part on the soft-combining.
The method of claim 1, further comprising:

performing an unsuccessful polar decoding process on the first information, wherein performing the polar decoding process on the combined information is based at least in part on the unsuccessful polar decoding process.
The method of claim 4, further comprising:

transmitting a negative acknowledgment (NACK) message in response to the first transmission based at least in part on the unsuccessful polar decoding process, wherein the second transmission is received based at least in part on the NACK message.
The method of claim 1, wherein:

the first candidate codeword corresponds to a first aggregation level and a size of the first set of coded bits is based at least in part on the first aggregation level; and

the second candidate codeword corresponds to a second aggregation level and a size of the second set of coded bits is based at least in part on the second aggregation level.
The method of claim 6, wherein the mother code length is based at least in part on the first aggregation level.
The method of claim 6, wherein:

the second aggregation level is equal to the first aggregation level and the size of the second set of coded bits is equal to the size of the first set of coded bits;

the second aggregation level is greater than the first aggregation level and the size of the second set of coded bits is greater than the size of the first set of coded bits; or

the second aggregation level is lower than the first aggregation level and the size of the second set of coded bits is less than the size of the first set of coded bits.
The method of claim 6, wherein:

the first aggregation level is based at least in part on a channel quality measurement corresponding to a channel for the first transmission; and

the second aggregation level is based at least in part on an updated channel quality measurement corresponding to the channel for the second transmission.
The method of claim 1, wherein the first transmission and the second transmission comprise physical downlink control channel (PDCCH) transmissions.
A method for wireless communications, comprising:

performing a polar encoding process on a set of information bits to determine a set of mother code bits;

loading the set of mother code bits into a circular buffer;

determining a first set of coded bits for transmission of the set of information bits, wherein the first set of coded bits corresponds to bits of the circular buffer in a first range from a first starting point to a first ending point of the circular buffer;

transmitting the first set of coded bits in a first transmission;

determining a second set of coded bits different from the first set of coded bits for re-transmission of the set of information bits, wherein the second set of coded bits corresponds to bits of the circular buffer in a second range from a second starting point to a second ending point of the circular buffer, wherein the second range and the first range are contiguous on the circular buffer; and

transmitting the second set of coded bits in a second transmission.
The method of claim 11, further comprising:

determining a first aggregation level for the first transmission, wherein a size of the first set of coded bits is based at least in part on the first aggregation level; and

determining a second aggregation level for the second transmission, wherein a size of the second set of coded bits is based at least in part on the second aggregation level.
The method of claim 12, further comprising:

determining a mother code size for the set of mother code bits based at least in part on the first aggregation level.
The method of claim 13, wherein:

the first aggregation level for the first transmission is different than the second aggregation level for the second transmission; and

the mother code size for the set of mother code bits is the same for both the first transmission and the second transmission.
The method of claim 12, wherein:

the second aggregation level is equal to the first aggregation level and the size of the second set of coded bits is equal to the size of the first set of coded bits;

the second aggregation level is greater than the first aggregation level and the size of the second set of coded bits is greater than the size of the first set of coded bits; or

the second aggregation level is lower than the first aggregation level and the size of the second set of coded bits is less than the size of the first set of coded bits.
The method of claim 12, wherein determining the first aggregation level and determining the second aggregation level further comprise:

identifying a channel quality measurement corresponding to a channel for the first transmission, wherein the first aggregation level is based at least in part on the identified channel quality measurement; and

identifying an updated channel quality measurement corresponding to the channel for the second transmission, wherein the second aggregation level is based at least in part on the identified updated channel quality measurement.
The method of claim 11, wherein the first starting point, the first ending point, or both of the circular buffer are based at least in part on a shortening process, puncturing process, repetition process, or combination thereof.
The method of claim 11, wherein determining the second set of coded bits different from the first set of coded bits for re-transmission of the set of information bits comprises:

receiving a negative acknowledgment (NACK) message in response to the first transmission; and

determining to transmit the second transmission based at least in part on the NACK message.
An apparatus for wireless communications, comprising:

a processor;

memory in electronic communication with the processor; and

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

receive, in a first transmission associated with a set of information bits, first information corresponding to a first set of coded bits of a first candidate codeword, wherein the first set of coded bits corresponds to bits of a circular buffer in a first range from a first starting point to a first ending point of the circular buffer, the circular buffer associated with a mother code length;

receive, in a second transmission associated with the set of information bits, second information corresponding to a second set of coded bits of a second candidate codeword, wherein the second set of coded bits corresponds to bits of the circular buffer in a second range from a second starting point to a second ending point of the circular buffer, wherein the second range and the first range are contiguous on the circular buffer;

combine the first information and the second information to obtain combined information;

perform a polar decoding process on the combined information according to the mother code length; and

determine the set of information bits based at least in part on the polar decoding process.
The apparatus of claim 19, wherein the instructions to combine the first information and the second information to obtain the combined information are executable by the processor to cause the apparatus to:

soft-combine a first set of log-likelihood ratios (LLRs) corresponding to the first information with a second set of LLRs corresponding to the second information to obtain a combined set of LLRs corresponding to the combined information.