Patent Description:
<NUM> systems can use polar coded transmissions, in particular for control messages. For example, <CIT> discloses generating a codeword using a polar code and transmitting a packet including at least one codeword indicated by a repetition order when bit repetition is needed. The repetition order is determined based on at least one of channel polarization or channel quality information.

In "<NPL>), maximum mother code lengths are proposed for DL and UL channels based on message size.

The invention relates to a wireless transmit/receive unit in accordance with independent claim <NUM> and a method in accordance with independent claim <NUM>. Further embodiments are covered by the dependent claims.

A detailed description of illustrative embodiments will now be described with reference to the various Figures. Although this description provides a detailed example of possible implementations, it should be noted that the details are intended to be exemplary and in no way limit the scope of the application.

A fifth generation of mobile communications technologies may be referred to as <NUM>. Ultra Reliable and Low latency Communications (URLLC) may be performed for <NUM> New Radio (NR). <NUM> may use one or more of the following. For example, <NUM> may use one or more of Enhanced Mobile Broadband (eMBB), Massive Machine Type Communications (mMTC), and/or URLLC. Requirements (e.g., different requirements) may exist for one or more of the mobile communication technologies. For example, higher data rate, higher spectrum efficiency, low power, higher energy efficiency, lower latency, and/or higher reliability may be requirements for one or more of the mobile communication technologies.

Commercial deployment of URLLC may be applied to, for example, factory automation, remote tele-surgery, real time mobile control and vehicle-to-vehicle applications, etc. In URLLC, requirements on availability and/or reliability of transmission may be emphasized, which may mean low error probability and/or low outage rate may be targets. One or more URLLC related KPIs may apply, for example, including one or more of the following. For URLLC, the target for user plane latency may be <NUM> for UL and/or <NUM> for DL. The target for reliability may be <NUM>-<NUM>, for example, within <NUM>.

The block error rate (BLER) for data transmission may be targeted at <NUM>%, for example, for LTE. The eNB may be in control of one or more (e.g., all) of resource allocation and/or scheduling. The transport format may be designated as a resource block and/or a Transmission Time Interval (TTI) whose length may be <NUM> in duration.

Hybrid ARQ (HARQ) for URLLC may be performed. For example, because of URLLC's requirements of high reliability and low latency, a one-shot transmission may suffer from low spectral efficiency. The inefficiency may be because (e.g., to guarantee a low error rate) a shot scheme may be conservative (e.g., may need to be conservative) in terms of bandwidth (BW) allocation, for example, so that the packet may be delivered successfully (e.g., delivered successfully, even under poor conditions, such as fading conditions). The WTRU's long-term signal-to-interference-plus-noise ratio (SINR) (e.g., geometry) may be known. If the WTRU's long-term SINR (e.g., geometry) is unknown, the transmission scheme may be conservative (e.g., may need to be conservative). In a time varying interference scenario (e.g., where an interference value may be unpredictable on top of channel fading), high reliability may not be achieved with one shot transmission and (e.g., at the same time) a number (e.g., reasonable number) of WTRUs may not be supported for the mixed traffic of URLLC and/or eMBB. HARQ schemes may not be conservative (e.g., may not be required to be conservative), for example, on initial transmission. The HARQ schemes may allocate less bandwidth on the initial transmission and/or deliver the packet (e.g., deliver the packet successfully) under one or more (e.g., most) channel conditions. The HARQ schemes may use re-transmissions to take care of the worst fading conditions.

In NR, channel coding designed for data channels of NR may support incremental redundancy (IR) and/or chase combining (CC) HARQ. The Incremental Freezing (IF) HARQ may be based on the polarization theory that part of the information bits may be re-transmitted on more reliable positions than in the previous transmissions. IR-HARQ scheme with Polar code may be desired for URLLC.

Polar coding may be performed. For example, a polar code may be adopted for control channel coding. Polar codes may be capacity achieving codes. Polar codes may be linear block codes, for example, with low encoding and/or decoding complexity, a low error floor, and/or explicit construction schemes.

A (N, K) polar code may be used. K may be the information block length. N may be the coded block length. The value N may be set as a power of <NUM>, e.g., N = <NUM>n for some integer n. Polar codes may be linear block codes. The generator matrix of a polar code may be expressed by GN = BNF⊗n, where BN may be the bit-reversal permutation matrix, (. )⊗n may denote the n-th Kronecker power, and/or <MAT>. In one or more polar codes, the BN may be ignored at the encoder side (e.g., for simplicity) and/or the bit-reversal operation may be performed at the decoder side. <FIG> shows an example of F⊗<NUM>. The codeword of polar code may be given by <MAT>.

A successive cancellation (SC) decoding scheme may be performed. Some decoding schemes may be developed based on SC decoding, for example, the successive cancellation list (SCL) decoding and/or Cyclic Redundancy Check (CRC)-Aided SCL decoding.

A CA (CRC-Aided) polar code may be a polar code with CRC-Aided successive cancellation list (SCL) decoder. In the CRC-aided decoding, the CRC bits may be used to select a codeword (e.g., the final codeword) from a list of candidate codewords at the end of the decoding. The CRC bits may be designed and/or used for error correction purpose (e.g., not for the traditional error detection). The CRC bits may fulfill a portion of the error detection.

Code constructions of polar codes may be performed. The polar codes may be structured, for example, in terms of encoding and/or decoding. The design of a polar code (e.g., a good polar code) may depend on the mapping of the K information bits to the N input bits of the polar encoder <MAT>. The K information bits may be put on the K best bit channels. The remaining N - K input bits (e.g., which may not be mapped from the information bits) may be frozen bits and/or may be set as <NUM>. The set of the positions for frozen bits may be called frozen set <IMG>.

The determination of bit channels (e.g., the best bit channels) may vary and/or may depend on channel conditions (e.g., real channel conditions). In determining the set of frozen channels, bit channels (e.g., all bit channels) may be ranked, for example, based on their reliabilities. The reliable bit channels may be good bit channels and/or the less reliable bit channels may be bad bit channels.

There may be one or more ways to calculate the reliability of a bit channel. For example, the Bhattacharyya bounds, the Monte-Carlo estimation, the full transition probability matrices estimation, and/or the Gaussian approximation may be used to calculate the reliabilities of bit channels. The ways (e.g., the different ways) to calculate the reliability of the bit channel may have one or more (e.g., different) computation complexities and/or may apply to one or more (e.g., different) channel conditions. In the ways to calculate the reliability of the bit channel, a parameter design signal to Noise ratio (SNR) may be selected, for example, before starting the calculation of reliabilities.

Ways may be used to calculate the rank of the bit channel, for example, that do not depend on the design SNR. For example, the rank sequence generated from a formula and/or expanded from a small sequence may be used to calculate the rank of the bit channel and/or may not depend on the design SNR.

Once the rank of the bit channels is determined, the information bits may be placed at high reliable bit channels and/or the low reliable bit channels may be used for frozen bits, such as shown in the example provided on <FIG>.

Polar encoding may be performed for URLLC Data. A polar code (e.g., polar coding) may be used for control channels (e.g., UCI and DCI), for example, for an NR eMBB. A polar code may be used for control channels (e.g., UCI and DCI) and/or a low-density parity-check (LDPC) code may be used for data channels. Low-density parity-check (LDPC) codes may include (e.g., suffer) error floor issues and/or may be incompatible (e.g., unfit) for the reliability requirement of URLLC data.

Polar encoding (e.g., a polar coding system) may be used for URLLC data. For a data channel, HARQ may be supported (e.g., may need to be supported). Polar coding (e.g., a polar coding system) may be used for a control channel and/or may not support (e.g., may not need to support) HARQ. One or more of a design for polar encoding, rate matching, or HARQ may be provided for URLLC data channel (e.g., may be needed for URLLC data channel).

Resource allocation may be used for URLLC data. URLLC data may use (e.g., require) low latency and/or high reliability. Polar encoding and/or rate matching may be performed, for example, to use low latency and/or high reliability. A resource allocation (e.g.. , additional resource allocation) may be used to support the transmissions of URLLC data.

URLLC polar encoding may be performed. Limited buffer rate matching may not be used for URLLC communications.

A mother code length may be determined. A polar code with a fixed mother code length (e.g., equal to N bits) may be applied. In examples, a URLLC transmission may be targeted to high reliable data (e.g., low code rate). With low code rates and/or support for HARQ, a maximum mother code length may be used for the polar encoding. The maximum mother code length N may depend on the WTRU category, capability, and/or data quality of service (QoS). The maximum mother code length for high capable WTRUs may be larger than for low capable WTRUs. For example, for data with low latency requirements, the maximum mother code length may be shorter than for data without a low latency requirement.

A polar code with variable mother code lengths may be applied. The mother code length N may depend on one or more of the following: payload size K, code rate R, a number of bits to be initially transmitted M, a maximum number of retransmissions RVmax, WTRU category or capability, or data QoS. The mother code length may be configured, e.g., using Radio Resource Control (RRC) signaling.

Information bits set may be determined and/or mapped. Information bits set determination in one-stage polar encoding may be performed. Before the polar encoding, e.g., using Arikan kernel, the information bits set I and/or the frozen bits set F may be determined (e.g., first determined). The union of information bits set and/or frozen bits set may be a set of integers, for example, from <NUM> to N-<NUM>. The payload (e.g., with or including CRC bits) may be mapped to the information bits set I. The frozen bits set F may be (e.g., may always be) <NUM>'s.

The information bits set may be larger than the original payload (e.g., with or including CRC bits) size K. The information bits set may be larger than the original payload (e.g., with CRC) size K, for example, to support the information bits expansion (e.g., which may produce a plurality of (e.g., different) redundancy versions for IR-HARQ transmissions). The information bits set cardinality |I| > K may depend on the used polar code sequence, payload size K, code rate R, rate matchings (e.g., rate matchings used), and/or the maximum number of retransmissions RVmax. Deriving information bits set and/or mapping the information bits to the information bits set may include one or more of the following. If the maximum mother code length is N and maximum number of retransmissions RVmax is <NUM> or <NUM>, the reliability ranking of N bits is given by Q<NUM> < Q<NUM> < ··· < QN-<NUM>. Qi may be the bit channel index corresponding to the i-th least reliable bit channel. The information bits set cardinality |I| may be determined by (N - j), for example, where j may be the index such that <MAT>.

The set {Qj, Qj+<NUM>,. , QN-<NUM>} may include K bit channels, for example, with indices larger than, or equal to, <MAT>.

One or more approaches may be used to determine an information bits set. The information bits set may be of the same cardinality as the payload size. The information bits set may be of a different (e.g., larger) cardinality than the payload size.

Information bits set may have the same length as the payload. Depending on the rate matching schemes, frozen bits (e.g., some frozen bits) may be predetermined. Using the reliability order from a polar code sequence, the K most reliable bit channels (e.g., which may not be pre-frozen) may be set as the information bits set, and/or the K payload bits may be mapped (e.g., mapped one-by-one) to the information bits set.

The information bits set I may be of a larger size than the payload K. For example, if the information bits set I is of larger size than the payload K, the mapping from K payload bits to the information bits set may be a one-to-many mapping. One or more of the following may apply for the case where the information bits set is larger than the payload. The N bit channels of polar code may be divided (e.g., sequentially equally divided) by y parts, where y may be a power of <NUM> and/or may depend on the maximum number of re-transmissions RVmax. K payload bits (e.g., all the K payload bits) may be mapped to the last part (e.g., N/y) of the bit channels. The last part of the bit channels may be the last block of (N/ y) bit channels (e.g., bit channels (y-<NUM>)/y*N, (y-<NUM>)/y*N+<NUM>,. , N-<NUM>). One or more (e.g., a portion) of the K payload bits may be mapped to the other (y - <NUM>) parts. One or more (e.g., each) parts of the bit channels may correspond to a redundancy version (e.g., a predefined redundancy version), e.g., each respective part may correspond to a respective redundancy version.

The mapping of the K payload bits to the last part of the bit channels may be similar to legacy mapping. The mapping may depend on the selected rate matching scheme. Bit channels (e.g., some bit channels) may be pre-freezed, for example, due to the punctured bits at the outputs.

The second to last part may refer to the second to last block of N/y bit channels (e.g., bit channels (y-<NUM>)/y*N, (y-<NUM>)/y*N+<NUM>,. , (y-<NUM>)/y*N-<NUM>). The information bits set in the second to last part mapping may be selected from the set of bit channels {Qj, Qj+<NUM>,. , QN-<NUM>}, for example, whose indices may be between <MAT> and <MAT>. There may be L bit channels and/or the bit channel set may be denoted by <IMG>. Mapping L payload bits to the bit channels may be performed in one or more of the following ways.

The L information bits may be selected from the K total information bits, for example, which may be mapped to the least reliable bit channels in the last part of the polar encoder. The L selected information bits may be mapped to the bit channel set <IMG>, for example, according to the bit channels' (e.g., reverse) reliability order. In examples, if an information bit is mapped to the least reliable bit channel (e.g., in the last part of the polar encoder), the information bit may be mapped to the most reliable bit channel in <IMG>. In examples, if an information bit is mapped to the least reliable bit channel (e.g., in the last part of the polar encoder), the information bit may be mapped to the least reliable bit channel in <IMG>.

The L information bits may be selected from the K total information bits, for example, which may be mapped to the smallest indices bit channels in the last part of the polar encoder. The L selected information bits may be mapped to the bit channel set <IMG>, for example, in an order (e.g., a natural index order). For example, if an information bit is mapped to the first bit channel (e.g., in the last part of the polar encoder), the information bit may be mapped to the first bit channel in <IMG>. The early termination capability of the distributed CRC scheme may be maintained. If an information bit is mapped to the first bit channel in the last part of the polar encoder, the information bit may be mapped to the last bit channel in <IMG>.

The third to last part mapping may be performed. The information bits set may be selected from the set of bit channels {Qj, Qj+<NUM>,. , QN-<NUM>}, for example, whose indices may be between <MAT> and <MAT>. There may be L' bit channels and/or the bit channel set may be denoted by <IMG>. L' payload bits may be mapped to the bit channels in one or more of the following ways. The L information bits may be selected from K information bits, for example, which may be mapped to unreliable (e.g., the least reliable) bit channels in the second to last part of the polar encoder. The L selected information bits may be mapped to the bit channel set <IMG>, for example, based on the reliability order of the bit channels the L information bits are mapped to in the second to last part mapping. (e.g., their reverse reliability order). For example, an information bit may be mapped to the most reliable information bit channel in the second to last part. If the information bit is mapped to the most reliable information bit channel in the second to last part, the same information bit may be mapped to the least reliable bit channel in S for the third to last part mapping. An information bit may be mapped to the least reliable information bit channels in the second to last part. If the information bit is mapped to the least reliable information bit channels in the second to last part, the same information bit may be mapped to the most reliable bit channel in S for the third to last part mapping.

The L information bits may be selected from K information bits, for example, which may be mapped to the smallest indices bit channels in the second to last part of the polar encoder. The L selected information bits may be mapped to the bit channel set <IMG>, for example, in a natural index order.

Mapping of one or more of the other parts may follow the mapping provided herein. For example, mapping of one or more of the other parts may follow the example illustrated for the mapping for the third to last part.

Information bits set determination in two-stage polar encoding may be performed. In the above, a single mother code length-N polar encoding may be applied. A two-stage polar encoding may be used. In the first stage (e.g., based on K and R), one or more (e.g., several) small polar codes may be used in parallel. For example, y polar encoders may be used, where each polar encoder may use a length N/y. y may be a power of <NUM>. The size of y may depend on K and R. For the last polar encoder, the mapping of K payload bits to the N/y bit channels may be performed (e.g., performed by considering the rate matching and the pre-frozen bits). For the first (y - <NUM>) polar encoders, the mapping of payload bits to the N/y bit channels may be different from the last polar encoder. Part (e.g., only part) of the payload bits may be mapped to the (y - <NUM>) polar encoders.

The output of the y polar encoders may be processed (e.g., further processed) in the second stage. An Arikan kernel may be applied, for example, as a block-wise operation, where a (e.g., each) of the y polar encoders may be treated as a block. For example, y = <NUM> and ai, i = <NUM>,. ,<NUM> may be the coded bits of the i-th polar encoder of length N/<NUM>. The outputs of the second stage processing may be <MAT>.

Circular buffer and rate matching may be performed (e.g., associated with URLLC). One or more of the following may apply. Saving polar encoded bits to a circular buffer may be performed. Bit selection for rate matching may be performed. Saving partial polar encoded bits to a circular buffer may be performed. Circular buffer design to support up to two retransmissions may be provided. Configuration and control signaling for URLLC HARQ may be performed.

Polar encoded bits may be saved in a circular buffer. Before saving, for example, the coded bits may be reordered. The bit reordering may support multiple rate matching schemes and/or IR-HARQ operations. There may be one or more (e.g., three) categories of rate matchings, including one or more of the following: shortening, puncturing, and/or repetition. Shortening may achieve the best BLER performance, for example, at high code rates (e.g., ><NUM>/<NUM>). The puncturing rate matching may achieve the best BLER performance, for example, at low code rates. Repetition may achieve good BLER performance, for example, at low code rates. The number of bits (e.g., the total number of bits) for transmission may be larger than a power of two. For example, the number of bits for transmission may be <NUM>, which is larger than <NUM> (<NUM><NUM>).

The performance range (e.g., a good performance range) of shortening may not lie in the URLLC supported coding range. Shortening may not be used in the rate matching.

The coded bits may be interleaved , for example, before the coded bits are saved to circular buffer. The coded bits may be interleaved , e.g., so that a puncturing may be supported by operations of the circular buffer.

If a split natural puncturing is supported, the coded bits may be separated (e.g., sequentially separated equally) to <NUM> sub-blocks. The middle two sub-blocks may be bit-wised interlaced, for example, before saving them to a circular buffer. If sub-block based puncturing is supported, the coded bits may be sequentially separated equally to p sub-blocks, say, b<NUM>, b<NUM>,. , bp-<NUM>. The sub-blocks may be interleaved by a pattern. The bits within a sub-block may be interleaved or may not be interleaved.

Part-wise interleaving may be performed. For example, in polar encoding, a (e.g., each) polar encoder may be of mother code length N/y bits. y may depend on a maximum number of retransmissions. The N coded bits may be separated (e.g., sequentially separated) to y parts. The coded bits interleaving operations may be applied on a (e.g., each) part (e.g., of N/y coded bits). <FIG> shows an example of the part-wise interleaving operations, where y may be equal to <NUM>. One or more (e.g., each) parts in <FIG> may correspond to a redundancy version (RV). Coded bits (e.g., each of the N/<NUM> coded bits) may be interleaved, for example, independent of other coded bits. Within a (e.g., each) part, sub-block wise interleaving and/or middle interlacing of interleaving may be applied. The design of the interleaving pattern may take into account that shortening may not be applied for URLLC data. The bottom coded bits (e.g., within each part) may be transmitted (e.g., may always be transmitted). The bottom coded bits may not be interleaved (e.g., may not need to be interleaved). For example, the sub-block interleaving may be applicable (e.g., may only be applicable) to the front coded bits. The interleaved bits of a (e.g., each) part may be saved to circular buffer sequentially.

Global-wise interleaving may be performed. The interleaving may be applied across the coded bits (e.g., all the N coded bits) (e.g., may be applied across all the parts). <FIG> shows an example of the global-wise interleaving operations, where the coded bits (e.g., all the N coded bits) may be interleaved globally. The sub-block wise interleaving may be applied. The design of the interleaving pattern may follow a reliability rule. For example, the encoded bits corresponding to low reliable bit channels (e.g., within each of the small polar encoder) may be interleaved to the front of circular buffer, for example, while the encoded bits corresponding to high reliable bit channels may be interleaved to the bottom of circular buffer.

Bit selection for rate matching may be performed. <FIG> shows an example bit selection from a circular buffer. <FIG> shows an example bit selection from a circular buffer with more than <NUM> self-decodable RV.

The interleaved bits may be saved to a circular buffer. The circular buffer reading may be in reverse order. For example, the reading from the circular buffer may be from the bottom of the circular buffer for the initial transmission RV0. The starting point of a (e.g., each) redundancy version may be uniformly distributed over N coded bits. For example, as shown in <FIG>, the starting point for RV1 may be at <MAT>, the starting point for RV2 may be at <MAT>, and/or the starting point for RV3 may be at <MAT>.

To support HARQ (e.g., adaptive HARQ), the starting point of an (e.g., each) RV may be adjusted. The starting point of an RV (e.g., other than RV0) may be set such that the RV is self-decodable. For example, as shown as RV3 in <FIG>, the starting point of the RV may cover the last quarter of the N coded bits.

A circular buffer and rate matching scheme (e.g., with alternate or complimentary features) may be provided. Partial polar encoded bits may be saved to a circular buffer. In circular buffer and rate matching operations described herein, the N encoded bits (e.g., all the N encoded bits) may be saved to the circular buffer. Less than N encoded bits may be saved to the circular buffer. Saving less than N encoded bits to the circular buffer may be used when (e.g., only when) puncturing is used and/or when the repetition is not used. The number of bits to be saved to the circular buffer may be as low as M bits, for example, which may be a number of bits to be transmitted in the initial transmissions. This may apply to the CC-HARQ case. For IR-HARQ cases, the number of bits to be saved to the circular buffer may be as high as M · RVmax.

<FIG> shows example circular buffer operations, for example, where part (e.g., only part) of the coded bits may be saved to the buffer. To support the puncturing scheme, for example, the latter portion (e.g., only the latter portion) of the encoded bits may be saved (e.g., saved to a circular buffer).

A portion (e.g., the same portion) of the bits in a (e.g., each) part may be saved to a circular buffer. This may work for a non-adaptive HARQ. For example, there may be g sub-blocks in part i, denoted by Pi,<NUM>,. After sub-block wise interleaving, a subset D of {<NUM>,. , g} (e.g., only a subset D of {<NUM>,. , g}) of the sub-blocks may be saved to the circular buffer, for example, {Pi,l, l ∈ D}. The subset may be applied to one or more (e.g., all) of the parts.

A portion (e.g., a different portion) of the bits in a (e.g., each) part may be saved to a circular buffer. This may work for adaptive HARQ. For example, one or more (e.g., each) part i may have its own subset Di of {<NUM>,. , g} of the sub-blocks to be saved to the circular buffer, for example, {Pi,l, l ∈ Di}.

The cardinality of the subset D and/or Di may depend on the rate matching output size of one or more (e.g., each) transmissions.

A circular buffer design may support one or more (e.g., two) retransmissions. The maximum number of retransmissions may be less than <NUM>, e.g., due to the low latency requirements for URLLC transmissions. For example, a maximum of <NUM> transmissions may be supported for URLLC data. The adaptive HARQ may be used. For example, the retransmission may have more coded bits than the initial transmission. An example of the supportive circular buffer may be as in <FIG>. The last quarter of the coded bits may be interleaved, and/or the first three quarter of the coded bits may be interleaved (e.g., interleaved independently). This scheme may be used with the example scheme shown in <FIG>.

The bit selection from the circular buffer may have (e.g., may only have) two starting positions, as shown in the example provided on <FIG>.

One or more circular buffers may be used to support IR-HARQ transmissions.

Configuration and control signaling for URLLC HARQ may be performed. For URLLC data transmissions, CC-HARQ and/or IR-HARQ may be supported. In examples, CC-HARQ (e.g., only CC-HARQ) may be supported for URLLC data transmissions. A WTRU may support (e.g., may only support) CC-HARQ due to WTRU capability and/or category. A WTRU capability and/or category may be configured (e.g., statically configured) by an RRC signaling message. Table <NUM> may be defined for HARQ support (e.g., different HARQ support), for example, for WTRU categories (e.g., different WTRU categories). A WTRU may require IR-HARQ support. For example, if a WTRU supports (e.g., is required to support) high data rates, the WTRU may have (e.g., may need to have) IR-HARQ support. A WTRU may apply (e.g., may only apply) CC-HARQ. For example, a WTRU may apply (e.g., may only apply) CC-HARQ if a WTRU does not support (e.g., is not required to support) high data rates.

A WTRU may (e.g. may only) support CC-HARQ, for example, for one or more predefined data types and/or QoS. Supporting CC-HARQ (e.g., only supporting CC-HARQ ) may be achieved by a high layer semi-static configuration. For example, RRCConnectionReconfiguration or RRCConnectionEstablishment may include information on operational HARQ types.

As an example, the following may be added to the RRCConectionReconfiguration message. RRCConnectionReconfiguration ::= SEQUENCE {
URLLC HARQ ENUMERATED {CC, CC-IR}.

Dynamic configuration of HARQ types may be supported. For example, the DCI and/or UCI may include a flag indicating whether an IR-HARQ scheme is supported, e.g., in the transmission of the TB. The field of RV order may be saved in the DCI or UCI, for example, because the field of RV may not be needed if CC-HARQ (e.g., only CC-HARQ) is supported.

A DCI format may include one or more of the following fields, for example, to support URLLC HARQ. The DCI format may include an IR-HARQ support flag (e.g., a <NUM> bit flag); a redundancy version (e.g., <NUM> bits), for example, used if the IR-HARQ support flag is set on; a new data indicator (e.g., <NUM> bit); a modulation and coding scheme (e.g., <NUM> bits or <NUM> bits if high order modulation is not supported and less items in MCS table for URLLC (e.g., less items in MCS table for URLLC than in MCS table for eMBB)); a HARQ process number (e.g., <NUM> bits); an identifier for DCI formats (e.g., <NUM> bit); and/or a frequency and time domain resource assignment.

Fields (e.g., different fields) in a DCI format (e.g., existing DCI format) may be re-interpreted, for example, because a field (e.g., a new field, such as IR-HARQ support flag) may be introduced and/or a field length may be reduced. For example, a modulation and coding scheme field may be reduced from <NUM> bits to <NUM> bits (e.g., considering a high order modulation may not be supported and/or less items or entries may be included in the MCS table for URLLC). The redundancy version may be valid if (e.g., only if) the IR-HARQ support flag is ON. The CC-HARQ may be supported (e.g., may always be supported), for example, if the IR-HARQ support flag is ON or OFF. The redundancy version may be (e.g., may always be) equal to <NUM>, for example, if CC-HARQ (e.g., only CC-HARQ) is supported.

Adaptive mother code length determination for polar decoding may be performed. Polar encoding, rate matching, and/or HARQ for URLLC data transmissions may be performed, for example, as described herein. A receiver may obtain the modulation symbols for the URLLC data transmissions. The receiver may obtain the log-likelihood ratio (LLR) of bits from the current transmission, for example, by demodulation.

The transmitter may apply a mother code length (e.g., a maximum mother code length) for polar encoding, for example, as described herein. The polar decoding may not use (e.g., may not have to use) the same mother code length as the polar encoding, for example, based on the polar code properties that the latter part of the encoded bits may not be affected by the upper part of the information bits.

The decoder may use a mother code length that is different (e.g., shorter) than the mother code length used by the transmitter. For example, the transmitter may generate as many encoded bits as possible. The encoded bits (e.g., all of the encoded bits) may not be sent to the receiver. The receiver may select a proper mother code length for decoding, for example, based on how many bits are received.

An adaptive mother code length may be applied for polar decoding. The determination of the mother code length may depend on the status of the circular buffer. A one-stage polar encoding scheme may be used, for example, as described herein. The receiver may check the circular buffer status, for example, after receiving demodulated symbols and/or storing LLRs (e.g., the corresponding LLRs) into the circular buffer. The maximum mother code length may be N bits. The latter part of the circular buffer at the receiver may be filled in (e.g., may be filled in first), for example, as described herein. L may be the smallest index of the filled LLR in the circular buffer. The mother code length for polar decoding may be calculated based on L. For example, if <MAT> <MAT> then the mother code length for polar decoding may be selected as N · <NUM>-l.

For example, N = <NUM>. If L = <NUM>, the mother code length for polar decoding may be selected as N · <NUM>-<NUM> = <NUM>.

An example rate dematching and polar decoding is shown in <FIG>. One or more of the following may be performed.

The demodulated symbols (e.g., LLRs) from a transmission may be combined (e.g., soft combined) with the existing values in the circular buffer. For example, the LLR of a bit may be demodulated (e.g., demodulated to a value A1) in a first reception and/or decoding attempt. The LLR of the same bit may be demodulated (e.g., demodulated to A2) in a second reception and/or decoding attempt. The average of the LLRs (e.g., A1 and A2) may be used for the decoding of the bit. The combined LLRs may be saved in the circular buffer. The smallest index with a filled LLR value may be determined, for example, from the current status of the circular buffer. The formula denoted by (*) may be used to calculate the mother code length for polar decoding. The polar decoding may be applied, for example, using the selected mother code length. If one or more LLRs in the circular buffer is not filled for the current polar decoding, the default value of <NUM> may be used, for example, because in the puncturing rate matching scheme the punctured bit may be <NUM> or <NUM> (e.g., with equal probability).

Resource allocation for URLLC data may be performed. The re-ordered bits may be converted to modulation symbols. The modulation symbols may be mapped to frequency and/or time resources. For example, the resource mapping may be frequency first and time second. The resource mapping may be time first and frequency second.

The symbols may be partitioned from a (e.g., each) code block (CB) to several groups and/or the groups may be distributed over one or more (e.g., the entire) resources. The number of partitioned groups may be identical for initial transmissions and re-transmissions. The number of partitioned groups may depend on the data QoS and/or data size. For example, for large size data, the number of partitions may be large. For data with high reliability requirements, the number of partitions may be large.

The group size may be identical for one or more (e.g., all) CBs. The unified group size may facilitate the resource mapping of the groups.

The distribution of the groups may provide one or more of the following features. The groups (e.g., all the groups) may be within the same OFDM symbol, for example, to facilitate the prompt decoding. The groups (e.g., all the groups) may be mapped to frequency locations (e.g., different frequency locations) from the groups' previous transmissions, for example, to achieve the frequency diversity. No overlap, or less overlap, on the frequency domain may occur between the initial transmission and the retransmissions, for example, for the same CB.

A fixed group distribution pattern may be applied. The pattern may be a function of an RV index, a CB index, and/or a CBG index.

Although the features and elements described herein consider LTE, LTE-A, New Radio (NR), and/or <NUM> specific protocols, it should be understood that the features and elements described herein are not restricted to LTE, LTE-A, New Radio (NR), and/or <NUM> specific protocols and may also be applicable to other wireless systems.

Claim 1:
A wireless transmit/receive unit (WTRU), comprising:
a processor configured at least in part to:
encode, using a polar coder, information bits input to a number of bit channels of the polar coder to obtain encoded bits, wherein the number of bit channels depends at least on a maximum number of retransmissions and wherein the polar coder uses a variable mother code length that is based at least on the maximum number of retransmissions; and
transmit encoded bits.