Method and apparatus for transmitting sidelink feedback in a wireless communication system

Abstract

A method and apparatus for transmitting sidelink feedback in a wireless communication system. In an example, a first user equipment receives, in a first timing, a sidelink transmission from a second user equipment associated with enabled sidelink hybrid automatic repeat request feedback. The first user equipment attempts to access a channel for transmission of sidelink hybrid automatic repeat request feedback in a first feedback resource in a second timing. The sidelink hybrid automatic repeat request feedback is in response to the sidelink transmission. The attempt to access the channel for transmission of the sidelink hybrid automatic repeat request feedback in the first feedback resource fails. The first user equipment performs channel access for a second feedback resource. The second feedback resource is within a window and / or within a predefined duration of the first timing or the second timing. In response to successfully performing the channel access, the first user equipment performs sidelink feedback transmission of the sidelink hybrid automatic repeat request feedback to the second user equipment in the second feedback resource.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to wireless communication networks, and more particularly, to methods and apparatus for transmitting sidelink feedback in a wireless communication system. BACKGROUND

[0002] With the rapid increase in demand to communicate large amounts of data to and from mobile communication devices, traditional mobile voice communication networks are evolving into networks that communicate with Internet Protocol (IP) data packets. This IP data packet communication can provide IP-borne voice, multimedia, multicast, and pointcast communication services to users of mobile communication devices.

[0003] An exemplary network structure is the Evolved Universal Terrestrial Radio Access Network (E-UTRAN). The E-UTRAN system can provide high data throughput in order to enable the IP-borne voice and multimedia services described above. Currently, the 3GPP standards organization is discussing new next generation (e.g., 5G) radio technologies. Therefore, changes to the current body of 3GPP standards are currently being submitted and considered in order to evolve and complete the 3GPP standards. SUMMARY

[0004] According to the present disclosure, one or more apparatuses and / or methods are provided. In an example from the perspective of a first User Equipment (UE) performing sidelink communication in a sidelink resource pool, the first UE receives a sidelink transmission from a second UE, wherein the sidelink transmission is associated with enabled sidelink Hybrid Automatic Repeat Request (HARQ) feedback. The first UE attempts to access a channel for transmission of sidelink HARQ feedback in a first feedback resource. The sidelink HARQ feedback is in response to the sidelink transmission. The attempt to access the channel for transmission of sidelink HARQ feedback in the first feedback resource fails. The first UE performs channel access for a second feedback resource. The second feedback resource is within a window. The channel access for the second feedback resource is successfully performed. In response to successfully performing the channel access for the second feedback resource, the first UE performs sidelink HARQ feedback to the sidelink feedback transmission of the second UE in the second feedback resource.

[0005] In an example from the perspective of a first UE performing sidelink communication in a sidelink resource pool from a second UE, the first UE receives a sidelink transmission from the second UE in a first timing, where the sidelink transmission is associated with enabled sidelink HARQ feedback. The first UE attempts to access a channel for transmission of sidelink HARQ feedback in a first feedback resource in a second timing. The sidelink HARQ feedback is in response to the sidelink transmission. The attempt to access the channel for transmission of sidelink HARQ feedback in the first feedback resource fails. The first UE performs channel access for a second feedback resource. The second feedback resource is within a predefined duration of the first timing or the second timing. The channel access for the second feedback resource is successfully performed. In response to successfully performing the channel access for the second feedback resource, the first UE performs sidelink feedback transmission of the sidelink HARQ feedback to the second UE in the second feedback resource. BRIEF DESCRIPTION OF DRAWINGS

[0006] Figure 1 A diagram of a wireless communication system is shown in accordance with one example embodiment.

[0007] Figure 2 is a block diagram of a transmitter system (also referred to as an access network) and a receiver system (also referred to as a user equipment or UE) in accordance with one example embodiment.

[0008] Figure 3 is a functional block diagram of a communication system in accordance with one example embodiment.

[0009] Figure 4 is a functional block diagram of a program code of Figure 3 in accordance with one example embodiment.

[0010] Figure 5 is a diagram showing an example scenario associated with a first UE receiving a physical sidelink control channel (PSCCH) and / or a physical sidelink shared channel (PSSCH) from a second UE in accordance with one example embodiment.

[0011] Figure 6 is a diagram showing a periodicity for a physical sidelink feedback channel (PSFCH) in accordance with one example embodiment.

[0012] Figure 7 is a diagram showing a configuration of a fixed frame period (FFP) and / or a slot in accordance with one example embodiment.

[0013] Figure 8 is a flowchart in accordance with one example embodiment.

[0014] Figure 9 is a flowchart in accordance with one example embodiment.

[0015] Figure 10 is a flow diagram in accordance with one example embodiment.

[0016] Figure 11 is a flow diagram in accordance with one example embodiment.

[0017] Figure 12 is a flow diagram in accordance with one example embodiment.

[0018] Figure 13 is a flow diagram in accordance with one example embodiment.

[0019] Figure 14 is a flow diagram in accordance with one example embodiment. DETAILED DESCRIPTION

[0020] The example wireless communication systems and apparatuses described below employ wireless communication systems that support broadcast services. Wireless communication systems are widely deployed to provide various types of communication such as voice, data, and so on. These systems can be based on code division multiple access (CDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), the 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) wireless access, 3GPP LTE-A or LTE-Advanced, 3GPP2 Ultra Mobile Broadband (UMB), WiMax, 3GPP New Radio (NR) wireless access for 5G, or some other modulation techniques.

[0021] In particular, the example wireless communication system devices described below can be designed to support one or more standards, such as the standard provided by a consortium named “3rd Generation Partnership Project,” referred to herein as a 3GPP, including: 3GPP TS 38.321 V16.5.0 (2021-06) 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NR; Medium Access Control (MAC) protocol specification (Release 16); 3GPP TS 38.212 V16.6.0 (2021-06) 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NR; Multiplexing and channel coding (Release 16); 3GPP TS 38.213 V16.6.0 (2021-06) 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NR; Physical Layer Procedures for Control (Release 16); 3GPP TS 38.214 V16.6.0 (2021-06) 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NR; Physical Layer Procedures for Data (Release 16); 3GPP TS 37.213 V17.0.0 (2021-12) 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Physical Layer Procedures for Shared Spectrum Channel Access (Release 17); Mohammed Hirzallah, Marwan Krunz, Balkan Kecicioglu, and Belal Hamzeh, Unlicensed 5G New Radio: Challenges and Evaluation, 2020 IEEE Transactions on Cognitive Communications and Networking, from the Internet <URL: https: / / arxiv.org / pdf / 2012.10937.pdf> <DOI: 10.1109 / TCCN.2020.3041851 retrieved; 3GPP TR 38.889 V16.0.0 (2018-12) 3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Study on NR-based access to unlicensed spectrum (Release 16); 3GPP TS 38.331 V16.5.0 (2021-06) 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NR; Radio Resource Control (RRC) protocol specification (Release 16); 3GPP TS 38.300 V16.6.0 (2021-06) 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NR; NR and NG-RAN Overall Description; Stage 2 (Release 16); RP-213678, New WID on NR sidelink evolution. The standards and documents listed above are expressly incorporated herein in their entireties by reference.

[0022] Figure 1A multiple access wireless communication system according to one or more embodiments of the present disclosure is presented. An access network 100 (AN) includes multiple antenna groups, wherein one antenna group includes 104 and 106, another antenna group includes 108 and 110, and yet another antenna group includes 112 and 114. In Figure 1 In general, only two antennas are shown for each antenna group, but each antenna group can utilize more or less antennas. An access terminal 116 (AT) is in communication with antennas 112 and 114, where antennas 112 and 114 transmit information to access terminal 116 over forward link 120 and receive information from access terminal 116 over reverse link 118. AT 122 is in communication with antennas 106 and 108, where antennas 106 and 108 transmit information to AT 122 over forward link 126 and receive information from AT 122 over reverse link 124. In a frequency-division duplexing (FDD) system, communication links 118, 120, 124 and 126 can use different frequencies for communication. For example, forward link 120 can use a different frequency than that used by reverse link 118.

[0023] The antennas and / or the areas in which they are designed to communicate are often referred to as a sector of the access network. In embodiments, the antenna groups can each be designed to communicate with access terminals in a sector of the area covered by access network 100.

[0024] In communication over forward links 120 and 126, the transmitting antennas of access network 100 can utilize beamforming to improve the signal-to-noise ratio of forward links for different access terminals 116 and 122. Also, an access network using beamforming to transmit to access terminals dispersed randomly through its coverage area causes less interference to access terminals in neighboring cells than an access network transmitting through a single antenna to all its access terminals.

[0025] An access network (AN) can be a fixed station or base station used for communicating with the terminals and can also be called an access point, Node B, Base Station, Enhanced Base Station, eNodeB (eNB), Next Generation NodeB (gNB), or some other terminology. An access terminal (AT) can also be called user equipment (UE), a wireless communication device, terminal, access terminal, or some other terminology.

[0026] Figure 2Embodiments of a transmitter system 210 (also referred to as an access network) and a receiver system 250 (also referred to as an access terminal (AT) or user equipment (UE)) in a multiple-input and multiple-output (MIMO) system 200 are presented. At the transmitter system 210, traffic data for a number of data streams can be provided from a data source 212 to a transmit (TX) data processor 214.

[0027] In one embodiment, each data stream is transmitted over a respective transmit antenna. The TX data processor 214 formats, codes, and interleaves the traffic data for each data stream based on a particular coding scheme selected for that data stream to provide coded data.

[0028] The coded data for each data stream can be multiplexed with pilot data using orthogonal frequency division multiplexing (OFDM) techniques. The pilot data is typically a known data pattern that is processed in a known manner and can be used at the receiver system to estimate the channel response. The multiplexed pilot and coded data for each data stream is then modulated (i.e., symbol mapped) based on a particular modulation scheme (e.g., binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), M-ary phase-shift keying (M-PSK), or M-ary quadrature amplitude modulation (M-QAM)) selected for that data stream to provide modulation symbols. Instructions executed by the processor 230 can determine the data rate, coding, and / or modulation for each data stream.

[0029] The modulation symbols for the data streams can then be provided to a TX MIMO processor 220, which can further process the modulation symbols (e.g., for OFDM). The TX MIMO processor 220 then provides N T modulation symbol streams to N T transmitters (TMTR) 222a through 222t, respectively. In certain embodiments, the TX MIMO processor 220 applies beam-forming weights to the symbols of the data streams and to the antenna from which the symbol is being transmitted.

[0030] Each transmitter 222 receives and processes a corresponding symbol stream to provide one or more analog signals, and further modulates (e.g., amplifies, filters, and / or up-converts) the analog signals to provide modulated signals suitable for transmission via a MIMO channel. Then, signals can be transmitted from N... T Antennas 224a to 224t transmit N from transmitters 222a to 222t. T A modulated signal.

[0031] At receiver system 250, via N R Antennas 252a to 252r receive the transmitted modulated signal and can provide the signal received from each antenna 252 to a corresponding receiver (RCVR) 254a to 254r. Each receiver 254 can adjust (e.g., filter, amplify, and downconvert) the corresponding received signal, digitize the adjusted signal to provide a sample, and / or further process the sample to provide a corresponding "received" symbol stream.

[0032] Next, the RX data processor 260 from N R Each receiver 254 receives and processes N based on specific receiver processing technology. R Each received symbol stream provides N T Each detected symbol stream. The RX data processor 260 can then demodulate, deinterleave, and / or decode each detected symbol stream to recover the service data used for the data stream. The processing performed by the RX processor 260 can complement the processing performed by the TX MIMO processor 220 and TX data processor 214 at the transmitter system 210.

[0033] Processor 270 can periodically determine which pre-decoding matrix to use (discussed below). Processor 270 formulates a reverse link message including the matrix index part and the rank part.

[0034] The reverse link message may include various types of information about the communication link and / or the received data stream. The reverse link message may then be processed by the TX data processor 238 (which may also receive service data from several data streams from the data source 236), modulated by the modulator 280, regulated by the transmitters 254a to 254r, and / or transmitted back to the transmitter system 210.

[0035] At transmitter system 210, the modulated signal from receiver system 250 is received by antenna 224, conditioned by receiver 222, demodulated by demodulator 240, and processed by RX data processor 242 to extract the reverse link message transmitted by receiver system 250. Next, processor 230 can determine which pre-decoding matrix to use to determine beamforming weights, and then process the extracted message.

[0036] Figure 3 An alternative simplified functional block diagram of a communication device according to one embodiment of the disclosed subject matter is presented. Figure 3 As shown, the communication device 300 in the wireless communication system can be used to achieve... Figure 1 UE (or AT) 116 and 122 or Figure 1 The communication device 300 includes a base station (or AN) 100, and the wireless communication system can be an LTE system or an NR system. The communication device 300 may include an input device 302, an output device 304, a control circuit 306, a central processing unit (CPU) 308, a memory 310, program code 312, and a transceiver 314. The control circuit 306 executes the program code 312 in the memory 310 via the CPU 308, thereby controlling the operation of the communication device 300. The communication device 300 can receive signals input by a user via the input device 302 (e.g., a keyboard or keypad) and can output images and sounds via the output device 304 (e.g., a display or speaker). The transceiver 314 is used to receive and transmit wireless signals, transmit received signals to the control circuit 306, and wirelessly output signals generated by the control circuit 306. Alternatively, the communication device 300 in a wireless communication system can also be used. Figure 1 AN 100 in the middle.

[0037] Figure 4 This is an embodiment based on the disclosed subject matter. Figure 3 The diagram shows a simplified block diagram of program code 312. In this embodiment, program code 312 includes an application layer 400, a layer 3 portion 402, and a layer 2 portion 404, and is coupled to a layer 1 portion 406. Layer 3 portion 402 can perform radio resource control. Layer 2 portion 404 can perform link control. Layer 1 portion 406 can perform and / or implement physical connections.

[0038] 3GPP TS 38.321V16.5.0 discusses sidelink (SL) data reception and / or transmission (e.g., associated with NR). One or more sections of 3GPP TS 38.321V16.5.0 are quoted below:

[0039] 5.22SL-SCH Data Transmission

[0040] 5.22.1 SL-SCH data transfer

[0041] 5.22.1.1 SL grant reception and SCI transfer

[0042] The sidelink grant is received dynamically on PDCCH, configured semi-statically by RRC or autonomously selected by the MAC entity. The MAC entity, with a sidelink grant on an active SL BWP, determines a set of PSSCH durations in which the transfer of SCI occurs, and a set of PSSCH durations in which the transfer of SL-SCH associated with the SCI occurs.

[0043] If the MAC entity has been configured to use sidelink resource allocation mode 2 to transfer using resource pools in a carrier based on sensing or random selection as indicated in TS 38.331 [5] or TS 36.331

[21] , the MAC entity shall, for each sidelink process: ....

[0045] NOTE 2: In case at least one logical channel configured with sl-HARQ-FeedbackEnabled is set to enabled, the MAC entity expects that PSFCH is always configured by RRC for at least one resource pool.

[0046] 1> if the MAC entity has selected a sidelink grant to create a (multiple) transfer(s) corresponding to a single MAC PDU, and if SL data is available in a logical channel, or a SL-CSI report is triggered:

[0047] 2> if SL data is available in a logical channel:

[0048] 3> if sl-HARQ-FeedbackEnabled is set to enabled for the logical channel:

[0049] 4> select among the resource pools any resource pool configured to use PSFCH resources;

[0050] 3> else:

[0051] 4> select among the resource pools any resource pool; ....

[0053] 2> perform TX resource selection (reselection) check on the selected resource pool as specified in clause 5.22.1.2;

[0054] 2> if TX resource selection (reselection) is triggered due to TX resource selection (reselection) check:

[0055] 3> select the number of HARQ retransmissions from the allowed number in sl-MaxTxTransNumPSSCH contained in sl-PSSCH-TxConfigList configured by RRC, and the highest priority of the allowed logical channel(s) on the carrier if configured by RRC and the CBR measured by lower layers according to clause 5.1.27 of TS 38.215

[24] if CBR measurement is available or the corresponding sl-defaultTxConfigIndex configured by RRC if CBR measurement is not available from the overlapping allowed number in sl-MaxTxTransNumPSSCH indicated in sl-CBR-PriorityTxConfigList; ...

[0057] 3> randomly select time and frequency resources for one transmission opportunity from the resources indicated by the physical layer according to the amount of selected frequency resources and the remaining PDB of the available SL data in the allowed logical channel(s) on the carrier and / or latency requirement of triggered SL-CSI report as specified in clause 8.1.4 of TS 38.214 [7];

[0058] 3> if one or more HARQ retransmissions are selected:

[0059] 4> if there are remaining available resources in the resources indicated by the physical layer according to clause 8.1.4 of TS 38.214 [7] for more transmission opportunities:

[0060] 5> randomly select time and frequency resources for one or more transmission opportunities from the available resources according to the amount of selected frequency resources, the selected number of HARQ retransmissions and the remaining PDB of the available SL data in the allowed logical channel(s) on the carrier and / or latency requirement of triggered SL-CSI according to clause 8.1.4 of TS 38.214 [7] by ensuring a minimum time gap between any two selected resources in case PSFCH is configured for this resource pool and retransmission resources can be indicated by the time resource assignment of the previous SCI according to clause 8.3.1.1 of TS 38.212 [9];

[0061] 5> consider the first occurring transmission opportunity in time as initial transmission opportunity and the other transmission opportunities as retransmission opportunities;

[0062] 5> consider all transmission opportunities as selected sidelink grant;

[0063] 3> else:

[0064] 4> consider the set as selected sidelink grant;

[0065] 3> use the selected sidelink grant to determine the PSCCH duration and the PSSCH duration according to TS 38.214 [7].

[0066] 1> if the selected sidelink grant is available for the (re)transmission(s) of the MAC PDU that has been positively acknowledged as specified in clause 5.22.1.3.3:

[0067] 2> clear the PSCCH duration and the PSSCH duration corresponding to the (re)transmission(s) of the MAC PDU from the selected sidelink grant.

[0068] For the selected sidelink grant, the minimum time gap between any two selected resources includes:

[0069] - the time gap between the end of the last symbol of the PSSCH transmission of the first resource and the start of the first symbol of the corresponding PSFCH reception determined by sl-MinTimeGapPSFCH and sl-PSFCH-Period for the resource pool; and

[0070] - the PSFCH reception and processing plus the time needed for sidelink retransmission preparation including necessary physical channel multiplexing and any TX-RX / RX-TX switching time.

[0071] The MAC entity shall, for each PSSCH duration:

[0072] 1> for each sidelink grant occurring within this PSSCH duration:

[0073] …

[0074] 2> if the MAC entity has been configured with sidelink resource allocation mode 1:

[0075] …

[0076] 2> else:

[0077] …

[0078] 3> if the MAC entity decides not to use the selected sidelink grant for the next PSSCH duration:

[0079] 4> set the resource reservation interval to 0 ms.

[0080] 3> else:

[0081] 4> set the resource reservation interval to the selected value.

[0082] …2> for this PSSCH duration, deliver the sidelink grant, the selected MCS and the associated HARQ information to the sidelink HARQ entity.

[0083] 5.22.1.3 Sidelink HARQ operation

[0084] 5.22.1.3.1 Sidelink HARQ entity

[0085] The MAC entity contains at most one sidelink HARQ entity for transmitting on the SL-SCH, maintaining multiple parallel sidelink processes.

[0086] The maximum number of transmitting sidelink processes associated with a sidelink HARQ entity is 16. A sidelink process can be configured for transmitting multiple MAC PDUs. For transmitting multiple MAC PDUs in sidelink resource allocation mode 2, the maximum number of transmitting sidelink processes associated with a sidelink HARQ entity is 4.

[0087] A delivered sidelink grant and its associated sidelink transmission information are associated with a sidelink process. One TB is supported per sidelink process.

[0088] For each sidelink grant, the sidelink HARQ entity shall:

[0089] 1> if the MAC entity determines that the sidelink grant is for initial transmission, as specified in clause 5.22.1.1; or

[0090] 1> if the sidelink grant is a configured sidelink grant and no MAC PDU is obtained in sl-PeriodCG of the configured sidelink grant:

[0091] 2> (re)associate the sidelink process to this grant and for the associated sidelink process:

[0092] NOTE 1A: The sidelink HARQ entity shall associate the selected sidelink grant to the sidelink process determined by the MAC entity.

[0093] 3> obtain a MAC PDU to transmit from the multiplexing and assembly entity, if present;

[0094] 3> if a MAC PDU for transmission has been obtained:

[0095] 4> if a HARQ process ID has been set for the sidelink grant:

[0096] 5> (re)associate the HARQ process ID corresponding to the sidelink grant to the sidelink process;

[0097] NOTE 1a: There is a one-to-one mapping between a HARQ process ID and a sidelink process in the MAC entity configured in sidelink resource allocation mode 1.

[0098] 4> The sidelink transmission information of the TB for the source and destination pair of the MAC PDU is determined as follows:

[0099] 5> The source Layer-1 ID is set to the 8 LSBs of the source Layer-2 ID of the MAC PDU;

[0100] 5> The destination Layer-1 ID is set to the 16 LSBs of the destination Layer-2 ID of the MAC PDU;

[0101] 5> The sidelink process is (re-)associated to the sidelink process ID;

[0102] NOTE 1b: How the UE determines the sidelink process ID in the SCI depends on the UE implementation for NR sidelink.

[0103] 5> The NDI is considered toggled compared to the value of the previous transmission corresponding to the sidelink identification information and the sidelink process ID of the MAC PDU and is set to the toggled value;

[0104] 5> The cast type indicator is set to one of broadcast, groupcast and unicast indicated by upper layers;

[0105] 5> If HARQ feedback has been enabled for the MAC PDU according to clause 5.22.1.4.2;

[0106] 6> The HARQ feedback enabled / disabled indicator is set to enabled.

[0107] 5> Otherwise:

[0108] 6> The HARQ feedback enabled / disabled indicator is set to disabled.

[0109] 5> The priority is set to the value of the highest priority of the logical channels (if present) and the MAC CEs (if contained) in the MAC PDU;

[0110] 5> If HARQ feedback is enabled for groupcast:

[0111] 6> If both the group size and the member ID are provided by upper layers and the group size is not larger than the number of candidate PSFCH resources associated with this sidelink grant:

[0112] 7> Select Ack-Nack or Negative-Only Ack.

[0113] 6> Otherwise:

[0114] 7> Select Negative-Only Ack.

[0115] …

[0116] 4> deliver the MAC PDU of the TB, the sidelink grant and the sidelink transmission information to the associated sidelink process;

[0117] 4> indicate to the associated sidelink process to trigger a new transmission.

[0118] 3> else:

[0119] 4> clear the HARQ buffer of the associated sidelink process.

[0120] 1> else (i.e. retransmission):

[0121] 2> if the HARQ process ID corresponding to the sidelink grant received on PDCCH, the configured sidelink grant or the selected sidelink grant is associated to a sidelink process with empty HARQ buffer; or

[0122] 2> if the HARQ process ID corresponding to the sidelink grant received on PDCCH is not associated to any sidelink process:

[0123] 3> ignore the sidelink grant.

[0124] 2> else:

[0125] 3> identify the sidelink process associated with this grant and for the associated sidelink process:

[0126] 4> deliver the sidelink grant of the MAC PDU to the associated sidelink process;

[0127] 4> indicate to the associated sidelink process to trigger a retransmission.

[0128] 5.22.1.3.1a Sidelink process

[0129] A sidelink process is associated with a HARQ buffer.

[0130] A new transmission and a retransmission are performed on the resources indicated in the sidelink grant specified in clause 5.22.1.1 with the MCS selected as specified in clause 8.1.3.1 of TS 38.214 [7] and in clause 5.22.1.1.

[0131] If the sidelink HARQ entity requests a new transmission, the sidelink process shall:

[0132] 1> store the MAC PDU in the associated HARQ buffer;

[0133] 1> store the sidelink grant received from the sidelink HARQ entity;

[0134] 1> generate the transmission as specified below.

[0135] If the sidelink HARQ entity requests retransmission, the sidelink procedure shall:

[0136] 1> store the sidelink grant received from the sidelink HARQ entity;

[0137] 1> generate the transmission as described below.

[0138] To generate the transmission, the sidelink procedure shall:

[0139] 1> if there is no uplink transmission; or

[0140] 1> if the MAC entity is able to perform the uplink transmission and the sidelink transmission simultaneously at the time of the transmission; or

[0141] 1> if another MAC entity and the MAC entity are able to perform the uplink transmission and the sidelink transmission simultaneously at the time of the transmission, respectively; or

[0142] 1> if there is a MAC PDU in uplink for which the transmission will be done for this duration, except from the MAC PDU prioritized from Msg3 buffer, MSGA buffer or as specified in clause 5.4.2.2, and the sidelink transmission is prioritized over the uplink transmission:

[0143] 2> instruct the physical layer to transmit SCI with associated sidelink transmission information according to the stored sidelink grant;

[0144] 2> instruct the physical layer to generate the transmission according to the stored sidelink grant;

[0145] 2> if HARQ feedback has been enabled for the MAC PDU according to clause 5.22.1.4.2:

[0146] 3> instruct the physical layer to monitor the PSFCH for the transmission and perform PSFCH reception as specified in clause 5.22.1.3.2.

[0147] 5.22.1.3.2 PSFCH reception

[0148] The MAC entity shall, for each PSSCH transmission:

[0149] 1> if an acknowledgement corresponding to the PSSCH transmission in clause 5.22.1.3.1a is obtained from the physical layer:

[0150] 2> pass the acknowledgement to the corresponding sidelink HARQ entity for the sidelink procedure;

[0151] 1> else:

[0152] 2> pass a negative acknowledgement to the corresponding sidelink HARQ entity for the sidelink procedure;

[0153] 1> if a PSSCH transmission occurs for a pair of source Layer-2 ID and destination Layer-2 ID corresponding to a PC5-RRC connection that has been established by upper layers:

[0154] 2> perform a HARQ-based sidelink RLF detection procedure as specified in clause 5.22.1.3.3.

[0155] 5.22.1.4 Multiplexing and combining

[0156] For a PDU associated with one SCI, the MAC shall consider only logical channels with the same source Layer-2 ID-destination Layer-2 ID pair for one of unicast, groupcast and broadcast associated with the SCI. Multiple transmissions for different sidelink procedures can be performed independently in different PSSCH durations.

[0157] 5.22.1.4.1.2 Selection of logical channels

[0158] For each SCI corresponding to a new transmission, the MAC entity shall:

[0159] 1> select a destination associated to one of unicast, groupcast and broadcast with at least one of the MAC CE and logical channel with the highest priority among the logical channels and MAC CEs for the SL grant associated to the SCI, if present, that satisfy all of the following conditions:

[0160] 2> SL data is available for transmission; and

[0161] 2> SBj> 0 if there is any logical channel with SBj> 0; and

[0162] 2> sl-configuredGrantType1Allowed is set to true if the SL grant is a configured grant Type 1, if configured; and

[0163] 2> sl-AllowedCG-List contains a configured grant index associated to the SL grant, if configured; and

[0164] 2> sl-HARQ-FeedbackEnabled is set to disabled if PSFCH is not configured for the SL grant associated to the SCI.

[0165] 1> select a logical channel among the logical channels belonging to the selected destination that satisfy all of the following conditions:

[0166] 2> SL data is available for transmission; and

[0167] 2> if configured, sl-ConfiguredGrantType1Allowed is set to true if the SL grant is a configured grant Type 1; and

[0168] 2> if configured, sl-AllowedCG-List contains configured grant indices associated to SL grants; and

[0169] 3> if PSFCH is configured for the sidelink grant associated to the SCI:

[0170] 4> if sl-HARQ-FeedbackEnabled is set to enabled for the highest priority logical channel that meets the above conditions, sl-HARQ-FeedbackEnabled is set to enabled; or

[0171] 4> if sl-HARQ-FeedbackEnabled is set to disabled for the highest priority logical channel that meets the above conditions, sl-HARQ-FeedbackEnabled is set to disabled.

[0172] 3> else:

[0173] 4> sl-HARQ-FeedbackEnabled is set to disabled.

[0174] 5.22.1.4.2 Multiplexing of MAC control elements and MAC SDUs

[0175] The MAC entity shall multiplex the MAC CEs and the MAC SDUs in a MAC PDU according to clause 5.22.1.4.1 and 6.1.6.

[0176] 5.22.2 SL-SCH data reception

[0177] 5.22.2.1 SCI reception

[0178] The SCI indicates whether there is a transmission on SL-SCH and provides related HARQ information. The SCI consists of two parts: 1st stage SCI on PSCCH and 2nd stage SCI on PSSCH as specified in clause 8.1 of TS 38.214 [7].

[0179] The MAC entity shall:

[0180] 1> for each PSCCH duration during which the MAC entity monitors PSCCH:

[0181] 2> if a 1st stage SCI has been received on PSCCH:

[0182] 3> determine the set of PSSCH durations in which reception of the 2nd stage SCI and transport block using the received part of the SCI takes place;

[0183] 3> if a 2nd stage SCI for this PSSCH duration has been received on the PSSCH:

[0184] 4> store the SCI as the SCI valid for the PSSCH duration corresponding to the transmission of the transport block and associated HARQ information and QoS information;

[0185] 1> for each PSSCH duration for which the MAC entity has a valid SCI:

[0186] 2> deliver the SCI and associated sidelink transmission information to the sidelink HARQ entity.

[0187] 5.22.2.2 Sidelink HARQ operation

[0188] 5.22.2.2.1 Sidelink HARQ entity

[0189] There is at most one sidelink HARQ entity at the MAC entity for the reception of SL-SCH, maintaining multiple parallel sidelink processes.

[0190] Each sidelink process is associated with a SCI in which the MAC entity is interested. This interest is determined by the sidelink identification information of the SCI. The sidelink HARQ entity directs the sidelink transmission information and associated TB received on the SL-SCH to the corresponding sidelink process.

[0191] The number of reception sidelink processes associated with the sidelink HARQ entity is defined in TS 38.306 [5].

[0192] For each PSSCH duration, the sidelink HARQ entity shall:

[0193] 1> for each SCI valid within this PSSCH duration:

[0194] 2> if the NDI has toggled compared to the value of the previous received transmission corresponding to the sidelink identification information and sidelink process ID of the SCI, or this is the first received transmission for the said pair of sidelink identification information and sidelink process ID of the SCI:

[0195] 3> if there is a sidelink process associated with the sidelink identification information and sidelink process ID of the SCI:

[0196] 4> consider the sidelink process as not occupied;

[0197] 4> clear the soft buffer of the sidelink process.

[0198] 3> allocate the TB received from the physical layer to the unoccupied sidelink process along with the associated sidelink identification information and sidelink process ID;

[0199] 3> associate the sidelink process with the sidelink identification information and sidelink process ID of this SCI and consider this transmission as a new transmission.

[0200] 1> for each sidelink process:

[0201] 2> if for the sidelink process, the NDI has not toggled compared to the value of the previously received transmission corresponding to the sidelink identification information and sidelink process ID of the SCI according to its associated SCI:

[0202] 3> allocate the TB received from the physical layer to the sidelink process and consider this transmission as a retransmission.

[0203] NOTE 2: A single sidelink process can only be (re-)associated to a single combination of sidelink identification information and sidelink process ID at a time, and a single combination of sidelink identification information and sidelink process ID can only be (re-)associated to a single sidelink process at a time.

[0204] 5.22.2.2.2 Sidelink process

[0205] For each PSSCH duration in which a transmission occurs for a sidelink process, receive one TB and associated HARQ information from the sidelink HARQ entity.

[0206] For each received TB and associated sidelink transmission information, the sidelink process shall:

[0207] 1> if this is a new transmission:

[0208] 2> attempt to decode the received data.

[0209] 1> else, if this is a retransmission:

[0210] 2> if the data of this TB has not been successfully decoded:

[0211] 3> instruct the physical layer to combine the received data with the data currently in the soft buffer for this TB and attempt to decode the combined data.

[0212] 1> if the data attempted to be decoded by the MAC entity is successfully decoded for this TB; or

[0213] 1> if the data for this TB was successfully decoded before:

[0214] 2> if this is the first successful decoding of data for this TB:

[0215] 3> if this TB is associated to unicast, the DST field of the decoded MAC PDU subheader is equal to the 8 MSB of any of the source Layer-2 IDs of the UE, with the 16 LSB equal to the Destination ID in the corresponding SCI, and the SRC field of the decoded MAC PDU subheader is equal to the 16 MSB of any of the destination Layer-2 IDs of the UE, with the 8 LSB equal to the Source ID in the corresponding SCI; or

[0216] 3> if this TB is associated to groupcast or broadcast, and the DST field of the decoded MAC PDU subheader is equal to the 8 MSB of any of the destination Layer-2 IDs of the UE, with the 16 LSB equal to the Destination ID in the corresponding SCI:

[0217] 4> pass the decoded MAC PDU to the disassembly and demultiplexing entity;

[0218] 2> consider the sidelink process as not occupied.

[0219] 1> else:

[0220] 2> instruct the physical layer to replace the data in the soft buffer used for this TB with the data the MAC entity attempted to decode.

[0221] 1> if HARQ feedback is enabled by the SCI: ....

[0223] 2> if negative-acknowledgement or unicast is indicated by the SCI according to clause 8.4.1 of TS 38.212 [9]:

[0224] 3> if the data the MAC entity attempted to decode is successfully decoded for this TB, or the data of this TB was successfully decoded before:

[0225] 4> instruct the physical layer to generate an acknowledgement of the data in this TB.

[0226] 3> else:

[0227] 4> instruct the physical layer to generate a negative acknowledgement of the data in this TB.

[0228] 5.22.2.3 Disassembly and demultiplexing

[0229] The MAC entity shall disassemble and demultiplex the MAC PDU as defined in clause 6.1.6.

[0230] 3GPP TS 38.212 V16.6.0 discusses Downlink Control Information (DCI) formats, Configured Grant Uplink Control Information (CG-UCI), and Sidelink Control Information (SCI) formats (e.g., associated with NR). One or more sections of 3GPP TS 38.212 V16.6.0 are quoted below:

[0231] 8.3.1.1 SCI format 1-A

[0232] SCI format 1-A is used to schedule PSSCH and 2nd stage SCI on PSSCH

[0233] The following information is conveyed by means of SCI format 1-A:

[0234] - Priority - 3 bits as specified in [12, TS 23.287] clause 5.4.3.3 and [8, TS 38.321] clause 5.22.1.3.1.

[0235] - Frequency resource assignment - bits when the value of the higher layer parameter sl-MaxNumPerReserve is configured to 2; otherwise bits when the value of the higher layer parameter sl-MaxNumPerReserve is configured to 3 as defined in [6, TS 38.214] clause 8.1.5.

[0236] - Time resource assignment - 5 bits when the value of the higher layer parameter sl-MaxNumPerReserve is configured to 2; otherwise 9 bits when the value of the higher layer parameter sl-MaxNumPerReserve is configured to 3 as defined in [6, TS 38.214] clause 8.1.5.

[0237] - Resource reservation period - bits as defined in [5, TS 38.213] clause 16.4, where N rsv_period is the number of entries in the higher layer parameter sl-ResourceReservePeriodList, provided that the higher layer parameter sl-MultiReserveResource is configured; otherwise 0 bits.

[0238] - DMRS pattern - bits as defined in [4, TS 38.211] clause 8.4.1.1.2, where N 模式 is the number of DMRS patterns configured by the higher layer parameter sl-PSSCH-DMRS-TimePatternList.

[0239] - 2nd stage SCI format-2 bits as defined in Table 8.3.1.1-1.

[0240] - Beta_offset indicator - 2 bits as provided by the higher layer parameters sl-BetaOffsets2ndSCI and Table 8.3.1.1-2.

[0241] - Number of DMRS ports - 1 bit as defined in Table 8.3.1.1-3.

[0242] - Modulation and coding scheme - 5 bits as defined in [6, TS 38.214] clause 8.1.3.

[0243] - Additional MCS table indicator - 1 bit if one MCS table is configured by the higher layer parameter sl-Additional-MCS-Table; 2 bits if two MCS tables are configured by the higher layer parameter sl-Additional-MCS-Table; otherwise 0 bits as defined in [6, TS 38.214] clause 8.1.3.1.

[0244] - PSFCH overhead indication - 1 bit as defined in [6, TS 38.214] clause 8.1.3.2, conditioned on the higher layer parameter sl-PSFCH-Period = 2 or 4; otherwise 0 bits.

[0245] - Reserved - number of bits as determined by the higher layer parameter sl-NumReservedBits with the value set to zero.

[0246] Table 8.3.1.1-1: 2nd stage SCI format

[0247] Values for the 2nd stage SCI format field 2nd stage SCI format 00 SCI format 2-A 01 SCI format 2-B 10 Reserved 11 Reserved

[0248] 8.4.1.1 SCI format 2-A

[0249] SCI format 2-A is used for decoding PSSCH by HARQ operation when the HARQ-ACK information contains ACK or NACK, when the HARQ-ACK information contains only NACK or when there is no feedback of HARQ-ACK information.

[0250] The following information is conveyed with the help of SCI format 2-A:

[0251] - HARQ process number - 4 bits.

[0252] - New data indicator - 1 bit.

[0253] - Redundancy version - 2 bits as defined in Table 7.3.1.1.1-2.

[0254] - Source ID - 8 bits, as defined in [6, TS 38.214] clause 8.1.

[0255] - Destination ID - 16 bits, as defined in [6, TS 38.214] clause 8.1.

[0256] - HARQ feedback enabled / disabled indicator - 1 bit, as defined in [5, TS 38.213] clause 16.3.

[0257] - Broadcast type indicator - 2 bits, as defined in Table 8.4.1.1-1 and [6, TS 38.214] clause 8.1.

[0258] - CSI request - 1 bit, as defined in [6, TS 38.214] clause 8.2.1 and [6, TS 38.214] clause 8.1.

[0259] Table 8.4.1.1-1: Broadcast type indicator

[0260]

[0261] The following clauses one or more sections of 3GPP TS 38.213 V16.6.0 are quoted below:

[0262] 16 UE procedures for sidelink

[0263] …

[0264] 16.3 UE procedures for reporting HARQ-ACK on sidelink

[0265] A UE can be indicated to transmit PSFCH with HARQ-ACK information in response to a PSSCH reception by a SCI format scheduling the PSSCH reception in one or more of the sub-channels from a number of sub-channels. The UE provides HARQ-ACK information containing ACK or NACK or NACK only.

[0266] A number of slots in a resource pool in a periodicity of PSFCH transmission occasion resources can be provided to a UE by sl-PSFCH-Periodicity. If the number is zero, PSFCH transmission from the UE in the resource pool is disabled.

[0267] A UE expects that a slot has a PSFCH transmission occasion resource if where is defined in [6, TS 38.214] and T' maxis the number of slots belonging to the resource pool within 10240 ms according to [6, TS 38.214] and is provided by sl-PSFCH-Period.

[0268] The UE can be indicated by higher layers not to transmit PSFCH in response to PSSCH reception [11, TS 38.321].

[0269] If the UE receives a PSSCH in a resource pool and the HARQ feedback enable / disable indicator field in the associated SCI format 2-A or SCI format 2-B has a value of 1 [5, TS 38.212], the UE provides HARQ-ACK information in PSFCH transmission in the resource pool. The UE transmits the PSFCH in the first slot that contains a PSFCH resource and is at least numberOfSlotsPSFCH slots after the last slot of the PSSCH reception provided by sl-MinTimeGapPSFCH.

[0270] The UE is provided by sl-PSFCH-RB-Set a set of PRBs in the resource pool for PSFCH transmission in the PRBs of the resource pool. For a number N subch of subchannels for the resource pool provided by sl-NumSubchannel and a number of PSSCH slots associated with a PSFCH slot that is less than or equal to , the UE allocates PRBs from the set of PRBs to slot i among the PSSCH slots associated with the PSFCH slot and subchannel j, where and the allocation starts in ascending order of i and continues in ascending order of j. The UE expects to be a multiple of .

[0271] The second OFDM symbol l' for PSFCH transmission in a slot is defined as l' = startSLsymbols + lengthSLsymbols - 2.

[0272] 16.3.1 UE procedure for receiving HARQ-ACK on sidelink

[0273] A UE indicated to transmit HARQ feedback for a PSSCH scheduled by a SCI format 2-A or a SCI format 2-B attempts to receive an associated PSFCH according to PSFCH resources determined as described in clause 16.3. The UE determines an ACK or NACK value of HARQ-ACK information provided in each PSFCH resource as described in [10, TS 38.133]. The UE does not determine both an ACK value and a NACK value for a PSFCH resource.

[0274] For each PSFCH reception occasion from a number of PSFCH reception occasions, the UE generates HARQ-ACK information to report to higher layers. To generate the HARQ-ACK information, the UE can be indicated by a SCI format to perform one of

[0275] - If the UE receives a PSFCH associated with a SCI format 2-A with a cast type indicator field value of “10”, then

[0276] - report to higher layers HARQ-ACK information with a value same as the value of the HARQ-ACK information determined by the UE from the PSFCH reception

[0277] - If the UE receives a PSFCH associated with a SCI format 2-A with a cast type indicator field value of “01”, then

[0278] - If the UE determines from each identity M ID of the number of PSFCH reception occasions in the PSFCH resources from at least one PSFCH reception occasion determines an ACK value, report to higher layers an ACK value as described in clause 16.3; otherwise, report to higher layers a NACK value

[0279] - If the UE receives a PSFCH associated with a SCI format 2-B or a SCI format 2-A with a cast type indicator field value of “11”, then

[0280] - If the UE determines for a PSFCH reception occasion that a PSFCH reception does not exist, report to higher layers an ACK value; otherwise, report to higher layers a NACK value

[0281] The following references one or more portions of 3GPP TS 38.214 V16.6.0 (e.g., associated with NR):

[0282] 8 Physical Sidelink Shared Channel Related Procedures

[0283] A UE can be configured by higher layers with one or multiple sidelink resource pools. A sidelink resource pool can be used for transmission of PSSCH as described in clause 8.1, or for reception of PSSCH as described in clause 8.3, and can be associated with sidelink resource allocation mode 1 or sidelink resource allocation mode 2.

[0284] In frequency domain, a sidelink resource pool consists of sl-NumSubchannel contiguous subchannels. A subchannel consists of sl-SubchannelSize consecutive PRBs, where sl-NumSubchannel and sl-SubchannelSize are higher layer parameters.

[0285] A set of slots that can belong to a sidelink resource pool is denoted by , where

[0286] -

[0287] - the slot index is relative to slot#0 of the radio frame corresponding to SFN 0 or DFN 0 of the serving cell,

[0288] - the set contains all slots except the slots,

[0289] -...

[0290] - the slots in the set are arranged in increasing order of slot index.

[0291] A UE determines the set of slots assigned to a sidelink resource pool as follows:

[0292] - using the bitmap associated with the resource pool , where the length L of the bitmap is bitmap configured by higher layers.

[0293] - if b k′ = 1, the slot belongs to the set, where k' = k mod L bitmap .

[0294] - the slots in the set are re-indexed such that the indices i of the remaining slots are consecutive {0, 1,..., T' max -1}, where T' max is the number of slots remaining in the set.

[0295] 8.1.4 UE procedure for determining the subset of resources to report to higher layers in PSSCH resource selection under sidelink resource allocation mode 2

[0296] In resource allocation mode 2, the higher layer can request the UE to determine a subset of resources from which the higher layer will select resources for a PSSCH / PSCCH transmission. To trigger this procedure, in slot n, the higher layer provides the following parameters for this PSSCH / PSCCH transmission:

[0297] - a resource pool from which resources will be reported;

[0298] - a L1 priority, prio TX ;

[0299] - a remaining packet delay budget;

[0300] - a number of sub-channels, L, to be used for the PSSCH / PSCCH transmission in the slot subCH ;

[0301] - optionally, a resource reservation interval, P rsvp_TX , in ms.

[0302] The following higher layer parameters have an impact on this procedure:

[0303] - sl-SelectionWindowList: an internal parameter T 2min is set to the corresponding value from the higher layer parameter sl-SelectionWindowList for a given value of prio TX .

[0304] - sl-Thres-RSRP-List: this higher layer parameter provides an RSRP threshold for each combination (p i , p j ) where p i is the value of the priority field in the received SCI format 1-A and p j is the priority of the transmission for which the UE selects resources; for a given invocation of this procedure, p j = prio TX .

[0305] - sl-RS-ForSensing: selects whether the UE uses PSSCH-RSRP or PSCCH-RSRP measurements as defined in clause 8.4.2.1.

[0306] - sl-ResourceReservePeriodList

[0307] - sl-SensingWindow: an internal parameter T0 is defined as the number of slots corresponding to sl-SensingWindow ms.

[0308] - sl-TxPercentageList: a list of internal parameters X defined as the conversion from percentage to ratio of sl-TxPercentageList (prio TX ) TX )

[0309] Resource reservation interval P rsvp_TX is converted from millisecond units to logical slot units, resulting in P' according to clause 8.1.7 rsvp_TX .

[0310] NOTE:

[0311] denotes the set of slots belonging to the sidelink resource pool and is defined in clause 8.

[0312] Using the following steps:

[0313] 1) Candidate single-slot resources R x，y are defined as the set of L subCH consecutive sub-channels with sub-channel x + j in slot , where j = 0,..., L subCH - 1. The UE shall assume that any set of L subCH consecutive sub-channels contained in the corresponding resource pool within the time interval [n + T1, n + T2] corresponds to one candidate single-slot resource, where

[0314] The selection of T depends on the UE implementation, where is defined in slots in Table 8.1.4-2, where μ SL is the SCS configuration of the SL BWP;

[0315] If T 2min is shorter than the remaining packet delay budget (in slots), then T2 depends on the UE implementation, where T 2min ≤ T2 ≤ remaining packet delay budget (in slots); otherwise T2 is set to the remaining packet delay budget (in slots).

[0316] The total number of candidate single-slot resources is denoted by M total .

[0317] 2) The sensing window is defined by the range of slots , where T0 is defined above and is defined in slots in Table 8.1.4-1, where μ SLConfigure the SCS for the SL BWP. The UE should monitor time slots belonging to the sidelink resource pool within the sensing window, except for time slots where its own transmissions occur. The UE will perform the actions in subsequent steps based on the decoded PSCCH and measured RSRP in these time slots.

[0318] 3) Internal parameter Th(p) i p j The value is set to the corresponding RSRP threshold indicated by the i-th field in the sl-Thres-RSRP-List, where i = p i +(p j -1)*8.

[0319] 4) Set S A It is initialized as a set of all candidate single-slot resources.

[0320] 5) The UE should be from set S A Exclude any candidate single-slot resource R x，y This is provided that it meets all of the following conditions:

[0321] -UE did not monitor the time slot in step 2

[0322] - For any periodic value followed by a higher-level parameter sl-ResourceReservePeriodList and a time slot having a 'Resource Reservation Period' field set to said periodic value. The assumed SCI format 1-A, which receives and indicates all sub-channels of the resource pool in this time slot, will satisfy condition c in step 6.

[0323] 5a) If set S A The remaining candidate single-slot resources R x，y The number is less than X·M total Then, as in step 4, set S A Initialize it as a set of all candidate single-slot resources.

[0324] 6) The UE should be from set S A Exclude any candidate single-slot resource R x，y This is provided that it meets all of the following conditions:

[0325] a) UE in time slot The received SCI format 1-A is provided, and the 'Resource Reservation Period' field (if present) and 'Priority' field in the received SCI format 1-A are respectively indicated by the value P according to Clause 16.4 of [6, TS 38.213]. rsvp_RX and prio RX ;

[0326] b) The performed RSRP measurement is higher than Th(prio RX , prio TX ) according to clause 8.4.2.1 for received SCI format 1-A

[0327] c) The same SCI format received in slot or when and only when the 'Resource reservation period' field is present in the received SCI format 1-A, it is assumed that the same SCI format received in slot determines the set of resource blocks and slots that overlap with according to clause 8.1.5, where q = 1, 2,..., Q and j = 0, 1,..., C resel - 1. Here, P' rsvp_RX is P rsvp_RX converted to logical slot units according to clause 8.1.7. rsvp_RX If P scal < T rsvp_RX and n' - m ≤ P' where if slot n belongs to the set then otherwise slot is the first slot after slot n that belongs to the set ; otherwise Q = 1. T scal is set to the selected window size T2converted to milliseconds.

[0328] 7) If the number of candidate single-slot resources remaining in the set S A is less than X · M total , then Th(p i , p j ) is increased by 3 dB for each priority value Th(p i , p j ) and the procedure continues with step 4.

[0329] The UE shall report the set S A to the higher layers.

[0330] Table 8.1.4-1: P

[0331]

[0332] Table 8.1.4-2: P

[0333]

[0334] 3GPP TS 37.213 V17.0.0 provides information associated with one or more definitions, one or more abbreviations, channel access procedures, and / or protocols related to channel access procedures in unlicensed spectrum (and / or shared spectrum). One or more sections of 3GPP TS 37.213 V17.0.0 are quoted below:

[0335] 4 Channel access procedures

[0336] 4.0 General

[0337] The following definitions apply to the terms used in the following in this specification, unless otherwise indicated:

[0338] - Channel refers to a carrier or a part of a carrier consisting of a contiguous set of resource blocks (RBs) over which a channel access procedure is performed in a shared spectrum.

[0339] - Channel access procedure is a sensing-based procedure to evaluate the availability of a channel for performing a transmission. The basic unit for sensing is a sensing slot, which has a duration T sl = 9 us. A sensing slot duration T sl is considered as idle, provided that the eNB / gNB or UE senses the channel during the sensing slot duration and determines that the detected power for at least 4 us within the sensing slot duration is less than an energy detection threshold X Thresh . Otherwise, the sensing slot duration T sl is considered as busy.

[0340] - Channel occupancy refers to a transmission by an eNB / gNB / UE on a channel after performing the corresponding channel access procedure in this section.

[0341] - Channel occupancy time refers to the total time for which an eNB / gNB / UE and any eNB / gNB / UE sharing the channel occupancy transmits on the channel after the eNB / gNB / UE performs the corresponding channel access procedure described in this clause. For determining the channel occupancy time, the gap duration is counted in the channel occupancy time in case the transmission gap is less than or equal to 25 us. Channel occupancy time can be shared for transmissions between an eNB / gNB and a corresponding UE.

[0342] - DL transmission burst is defined as a set of transmissions from an eNB / gNB without any gap larger than 16 us. Transmissions from an eNB / gNB separated by a gap larger than 16 us are considered as separate DL transmission bursts. An eNB / gNB can transmit a transmission after a gap within a DL transmission burst without the need to sense the availability of the corresponding channel.

[0343] - An UL transmission burst is defined as a set of transmissions from a UE without any gap larger than 16us. Transmissions from a UE separated by a gap larger than 16us are considered as separate UL transmission bursts. A UE can transmit a transmission after a gap within an UL transmission burst without sensing the availability of the corresponding channel. [...]

[0345] 4.1 Downlink channel access procedure ....

[0347] The gNB performs the channel access procedure in this clause unless the higher layer parameter ChannelAccessMode-r16 is provided and ChannelAccessMode-r16 ='semi-static'.

[0348] 4.1.1 Type 1 DL channel access procedure

[0349] This clause describes the channel access procedure to be performed by the eNB / gNB where the duration spanned by the sensing time slots that are sensed as idle before a downlink transmission is random. This clause applies to the following transmissions:

[0350] - A transmission containing PDSCH / PDCCH / EPDCCH initiated by the eNB, or

[0351] - Any transmission initiated by the gNB.

[0352] The eNB / gNB can transmit one transmission after the first sensing time slot duration T d is sensed as idle and after the counter N is zero in step 4. The counter N is adjusted by sensing the channel for an additional sensing time slot duration according to the following steps:

[0353] 1) Set N = N init , where N init is a random number uniformly distributed between 0 and CW p , and go to step 4;

[0354] 2) If N > 0 and the eNB / gNB chooses to decrement the counter, set N = N - 1;

[0355] 3) Sense the channel in the additional sensing time slot duration, and if the additional sensing time slot duration is idle, go to step 4; otherwise, go to step 5;

[0356] 4) If N = 0, stop; otherwise, go to step 2.

[0357] 5) Sense the channel until an additional defer duration T d is elapsed.upon detecting a busy sensing slot or detecting an additional defer duration T d all sensing slots of T d are idle.

[0358] 6) If the channel is sensed idle during all sensing slot durations T d of the additional defer duration T sl , go to step 4; otherwise, go to step 5.

[0359] If the eNB / gNB has not transmitted a transmission after step 4 in the above procedure, the eNB / gNB can transmit a transmission on the channel provided that the channel is sensed idle at least in the sensing slot duration T sl when the eNB / gNB is ready to transmit, and the channel is sensed idle during all sensing slot durations T d of the defer duration T sl immediately preceding the intended transmission. If the channel is not sensed idle in the sensing slot duration T sl when the eNB / gNB is ready to transmit for the first time after sensing the channel, or if the channel is sensed not idle during any sensing slot duration T d of the defer duration T d immediately preceding the intended transmission, the eNB / gNB proceeds to step 1 after sensing the channel idle during a sensing slot duration of the defer duration T d .

[0360] The defer duration T d consists of a duration T f = 16 us and m p consecutive sensing slot durations T sl immediately following, and T f contains a free sensing slot duration T f at the beginning of T sl .

[0361] The eNB / gNB shall not transmit on the channel for a channel occupancy time T m cot，p exceeding T m cot，p , where the channel access procedure is performed based on the channel access priority class p associated with the eNB / gNB transmission as given in Table 4.1.1-1.

[0362] If the eNB / gNB transmits a discovery burst as described in clause 4.1.2 when N > 0 in the above procedure, the eNB / gNB shall not decrement N during sensing slot durations overlapping with the discovery burst.

[0363] A gNB can transmit a transmission containing a discovery burst using any channel access priority class that satisfies the conditions described in this clause for performing the above procedure.

[0364] The gNB shall use the channel access priority class applicable to the unicast user plane data multiplexed in the PDSCH for performing the above procedure to transmit a transmission containing unicast PDSCH with user plane data.

[0365] For p = 3 and = 4, if it can be guaranteed on a long-term basis (e.g., to the extent of a regulation) that there is no other technology sharing the channel, then T m cot，p = 10 ms, otherwise, T m cot，p = 8 ms.

[0366] Table 4.1.1-1: Channel Access Priority Classes (CAPCs)

[0367] ....

[0369] 4.1.2 Type 2 DL Channel Access Procedure

[0370] This clause describes the channel access procedure to be performed by the eNB / gNB, where the duration of the sensing time slots that are sensed as idle before a downlink transmission is deterministic.

[0371] If the eNB performs a Type 2 DL channel access procedure, it follows the procedure described in clause 4.1.2.1.

[0372] The Type 2A channel access procedure as described in clause 4.1.2.1 is only applicable to the following transmissions performed by the eNB / gNB:

[0373] - a transmission initiated by the eNB containing a discovery burst and not containing a PDSCH, where the transmission duration is at most 1 ms, or

[0374] - a transmission initiated by the gNB with a discovery burst only or with a discovery burst multiplexed with non-unicast information, where the transmission duration is at most 1 ms and the discovery burst duty cycle is at most 1 / 20, or

[0375] - a transmission by the eNB / gNB after a gap of 25us in a shared channel occupancy as described in clause 4.1.3 following a transmission by the UE.

[0376] The Type 2B or Type 2C DL channel access procedure as described in clauses 4.1.2.2 and 4.1.2.3, respectively, is applicable to a transmission by the gNB after a gap of 16us or at most 16us, respectively, in a shared channel occupancy as described in clause 4.1.3 following a transmission by the UE.

[0377] 4.1.2.1 Type 2A DL Channel Access Procedure

[0378] The eNB / gNB can transmit a DL transmission immediately after sensing the channel idle for at least the sensing interval T short_dl = 25 us. T short_dl is composed of a duration T f = 16 us followed immediately by a sensing slot group, and T f includes the sensing slot at the beginning of T f . If both sensing slots of T short_dl are sensed to be idle, the channel is considered idle for T short_dl .

[0379] 4.1.2.2 Type 2B DL channel access procedure

[0380] The gNB can transmit a DL transmission immediately after sensing the channel idle for a duration T f = 16 us. T f includes the sensing slot occurring within the last 9 us of T f . If the channel is sensed to be idle for a total of at least 5 us, with at least 4 us of sensing occurring in the sensing slots, the channel is considered idle for a duration T f .

[0381] 4.1.2.3 Type 2C DL channel access procedure

[0382] When a gNB follows the procedure in this clause for transmitting a DL transmission, the gNB does not sense the channel prior to transmitting the DL transmission. The duration of the corresponding DL transmission is at most 584 us.

[0383] 4.2 Uplink channel access procedure

[0384] A UE performing a transmission on a LAA Scell, an eNB scheduling or configuring a UL transmission for a UE performing a transmission on a LAA Scell, and a UE performing a transmission on a channel and a gNB scheduling or configuring a UL transmission for a UE performing a transmission on a channel shall perform the procedures described in this clause for the UE to access the channel on which the transmission is performed.

[0385] A UE performs the channel access procedures in this clause unless the higher layer parameter ChannelAccessMode-r16 is provided and ChannelAccessMode-r16 ='semi-static'.

[0386] If the UE fails to access the channel prior to an intended UL transmission to the gNB, layer 1 informs the higher layers of the channel access failure.

[0387] 4.2.1 Channel access procedure for uplink transmissions

[0388] A UE can access a channel on which a UL transmission is performed according to one of Type 1 or Type 2 UL channel access procedures. Type 1 channel access procedure is described in clause 4.2.1.1. Type 2 channel access procedure is described in clause 4.2.1.2.

[0389] If the UL grant scheduling a PUSCH transmission indicates Type 1 channel access procedure, the UE shall use Type 1 channel access procedure for transmitting a transmission containing the PUSCH transmission, unless otherwise specified in this clause.

[0390] The UE shall use Type 1 channel access procedure for transmitting a transmission containing an autonomous or configured grant PUSCH transmission on configured UL resources, unless otherwise specified in this clause.

[0391] If the UL grant scheduling a PUSCH transmission indicates Type 2 channel access procedure, the UE shall use Type 2 channel access procedure for transmitting a transmission containing the PUSCH transmission, unless otherwise specified in this clause.

[0392] The UE shall use Type 1 channel access procedure for transmitting SRS transmissions that do not contain a PUSCH transmission. The UL channel access priority class p = 1 in table 4.2.1-1 is used for SRS transmissions that do not contain a PUSCH.

[0393] If a DL assignment triggering SRS but not scheduling a PUCCH transmission indicates Type 2 channel access procedure, the UE shall use Type 2 channel access procedure.

[0394] If the UE sets the ‘COT sharing indication’ in AUL-UCI to ‘1’ in a subframe within an autonomous uplink transmission as described in clause 4.1.3, the total channel occupancy time of the autonomous uplink transmission obtained by the channel access procedure in this clause (including the subsequent DL transmission) shall not exceed T ulm cot，p where T ulm cot，p is given in table 4.2.1-1.

[0395] Table 4.2.1-1: Channel access priority classes (CAPCs) for UL

[0396]

[0397] ....

[0399] 4.2.1.1 Type 1 UL channel access procedure

[0400] This clause describes the channel access procedure to be performed by the UE, where the duration of the sensing time slots that are sensed as idle before a UL transmission is random. This clause applies to the following transmissions:

[0401] - PUSCH / SRS transmission scheduled or configured by eNB / gNB, or

[0402] - PUCCH transmission scheduled or configured by gNB, or

[0403] -Transmissions related to the random access procedure.

[0404] UE can delay duration T d After the channel is first sensed to be idle during the time slot duration and after the counter N is zero in step 4, transmission is carried out using a type 1 channel access procedure. The counter N is adjusted by sensing the channel for the additional time slot duration according to the steps described below.

[0405] 1) Set N = N init Where N init It is evenly distributed in O and CW p A random number between these values ​​is generated, and then proceeds to step 4.

[0406] 2) If N > 0 and the UE selects a decrementing counter, then set N = N - 1;

[0407] 3) Sensing the channel during the additional time slot duration, and if the additional time slot duration is idle, proceed to step 4; otherwise, proceed to step 5.

[0408] 4) If N = 0, stop; otherwise, go to step 2.

[0409] 5) Sensing channel until the additional delay duration T d A busy time slot or an additional delay duration T was detected within the time slot. d All time slots are idle;

[0410] 6) If the additional delay duration T d If the channel is detected to be idle during all time slot durations, proceed to step 4; otherwise, proceed to step 5.

[0411] If the UE has not yet transmitted a UL transmission on the channel where the UL transmission is performed after step 4 in the above procedure, then the UE may transmit a transmission on the channel, provided that when the UE is ready to transmit the transmission, it is at least during the sensing time slot duration T. sl The channel is sensed to be idle, and there is a delay duration T immediately preceding the transmission. d The channel has been sensed to be idle for the entire duration of the time slot. If the UE senses the channel first after it is ready to transmit, during the sensing time slot duration T... sl If no channel idle is detected, or if a delay duration T immediately precedes a scheduled transmission.d is not sensed idle during any of the sensing slot durations, then the UE proceeds to step 1 after a deferral duration T d is sensed idle during a slot duration of T

[0412] the deferral duration T d is composed of a duration T f = 16us followed by m p consecutive slot durations, where each slot duration is T sl = 9us, and T f contains the idle slot duration T f at the beginning of T sl .

[0413] 4.2.1.2 Type 2 UL Channel Access Procedure

[0414] This clause describes a channel access procedure to be performed by a UE, where the duration spanned by the sensing slots that are sensed idle before a UL transmission is deterministic.

[0415] 4.2.1.2.1 Type 2A UL Channel Access Procedure

[0416] If a UE is instructed to perform a Type 2A UL channel access procedure, the UE uses the Type 2A UL channel access procedure for UL transmissions. The UE can transmit a transmission immediately after sensing the channel idle in at least a sensing interval T short_ul = 25us. T short_ul is composed of a duration T f = 16us followed by one sensing slot, and T f contains the sensing slot at the beginning of T f . If both sensing slots of T short_ul are sensed idle, the channel is considered idle in T short_ul .

[0417] 4.2.1.2.2 Type 2B UL Channel Access Procedure

[0418] If a UE is instructed to perform a Type 2B UL channel access procedure, the UE uses the Type 2B UL channel access procedure for UL transmissions. The UE can transmit a transmission immediately after sensing the channel idle in a duration T f = 16us. T f contains the sensing slots occurring in the last 9us of T f . If the channel is sensed idle for a total of at least 5us, with at least 4us of sensing occurring in the sensing slots, the channel is considered idle in the duration T f .

[0419] 4.2.1.2.3 Type 2C UL channel access procedure

[0420] If the UE is indicated to perform Type 2C UL channel access procedure for a UL transmission, the UE does not sense the channel before the transmission. The duration of the corresponding UL transmission is at most 584us.

[0421] 4.3 Channel access procedure for semi-static channel occupancy

[0422] The channel access procedure based on semi-static channel occupancy as described in this clause is intended for environments where the absence of other technologies is guaranteed, e.g. by regulatory levels, privacy venue policies, etc.

[0423] If the gNB provides the UE with the higher layer parameter ChannelAccessMode-r16 = 'SemiStatic' through SIB1 or dedicated configuration for the serving cell, the gNB can initiate a periodic channel occupancy on the channel within the bandwidth of the serving cell every T x starting at an even indexed radio frame at i · T x with a maximum channel occupancy time T y = 0.95T x where T x = period is a higher layer parameter provided in SemiStaticChannelAccessConfig and

[0424] The duration of T z = max(0.05T x , 100us) at the end of one period is referred to as the idle duration of the period.

[0425] If the gNB additionally configures the UE with the higher layer parameter ue- SemiStaticChannelAccessConfig consisting of ue-Period and ue-Offset, the UE can initiate a channel occupancy on the channel within the bandwidth of the serving cell every T u = ue-Period in ms, with a corresponding maximum channel occupancy time T v = 0.95T u . The offset of the periodic channel occupancy is determined by T o = ue-Offfset as the number of symbols from the start of an even indexed radio frame to the start of the first period in which the UE can initiate a channel occupancy in the radio frame. The duration of T w = max(0.05T u at the end of one period.The duration of the idle duration of the period is referred to as the idle duration of the channel occupancy time.

[0426] For determining the channel occupancy time based on the semi-static channel access procedure, the duration of the period excluding any transmission gaps of the idle duration is counted in the channel occupancy time. In the subsequent procedure in this clause, when the gNB or the UE performs sensing for assessing the channel availability, at least T sl = 9us is performed, unless a longer sensing duration is required (e.g., regulatory level), in which case T sl = 16us is performed. When T sl = 16us is performed, the channel is considered idle if the channel is sensed to be idle for a total of at least 5us, with at least 4us of sensing occurring in the last 9us time interval of the sensing duration. The corresponding X Thresh is adjusted as described in clauses 4.1.5 and 4.2.3, respectively.

[0427] 4.3.1 Channel access procedure to initiate channel occupancy

[0428] For semi-static channel occupancy, if ue-SemiStaticChannelAccessConfig is not present, the procedure in clause 4.3.1.1 is followed. Otherwise, the procedure in clause 4.3.1.2 applies.

[0429] 4.3.1.1 Channel occupancy initiated by gNB only

[0430] Channel occupancy initiated by gNB and shared with UEs is subject to the following:

[0431] - The gNB shall transmit a DL transmission burst at the start of the channel occupancy time immediately after sensing the channel to be idle for at least the sensing slot duration T sl . If the channel is sensed to be busy, the gNB shall not perform any transmissions during the current period.

[0432] - If the gap between the DL transmission burst and any previous transmission burst is greater than 16us, the gNB can transmit a DL transmission burst within the channel occupancy time immediately after sensing the channel to be idle for at least the sensing slot duration T sl . If the channel is sensed to be busy, the gNB shall not perform any transmissions during the current period.

[0433] - If the gap between the DL and UL transmission bursts is at most 16us, the gNB can transmit a DL transmission burst after the UL transmission burst within the channel occupancy time without sensing the channel.

[0434] - After detecting a DL transmission burst within a channel occupancy time, a UE can transmit a UL transmission burst as follows:

[0435] - If the gap between the UL and DL transmission bursts is at most 16us, the UE can transmit a UL transmission burst after a DL transmission burst within a channel occupancy time without sensing the channel.

[0436] - If the gap between the UL and DL transmission bursts is more than 16us, then the UE can transmit a UL transmission burst after a DL transmission burst within a channel occupancy time after sensing the channel to be idle within at least a sensing slot duration T sl .

[0437] - A UE can be indicated by a gNB to transmit a UL transmission burst within a channel occupancy time without sensing the channel, or to transmit a UL transmission burst after sensing the channel to be idle within at least a sensing slot duration T sl immediately preceding the end of the transmission.

[0438] - A gNB and a UE shall not transmit any transmissions in a set of consecutive symbols for a duration of at least T z = max(0.05T x , 100us) before the start of the next period.

[0439] 4.3.1.2 Channel occupancy initiated by a gNB or a UE

[0440] 4.3.1.2.1 Channel occupancy initiated by a gNB and a sensing procedure

[0441] If a gNB starts transmitting a DL transmission burst at the start of a period immediately after sensing the channel to be idle for at least a sensing slot duration T sl = 9us, the gNB initiates a channel occupancy in a period of duration T x and ends the transmission of the DL transmission burst before the start of the idle duration of the period. When a UL or DL transmission burst is associated with a channel occupancy initiated by a gNB in the period, the following applies:

[0442] - The UL or DL transmission burst is confined within the period and ends before the start of the idle duration of the period.

[0443] - If the gap between a DL transmission burst and any previous DL transmission burst in the period is more than 16us, the DL transmission burst can be transmitted if the channel is sensed to be idle for at least a sensing slot duration T sl = 9us immediately preceding the DL transmission.

[0444] - If the gap between the UL transmission burst and any previous DL transmission burst in the period is more than 16us, then the UL transmission burst can be transmitted if the channel is sensed idle in at least a sensing slot duration T sl = 9us immediately preceding the UL transmission.

[0445] - If the gap between the UL transmission burst and any previous DL transmission burst in the period is at most 16us, then the UL transmission burst can be transmitted without sensing.

[0446] 4.3.1.2.2 Channel occupancy initiated by the UE and sensing procedure

[0447] If the UE starts transmitting the UL transmission burst immediately after sensing the channel idle in at least a sensing slot duration T sl = 9us at the beginning of the period, the UE initiates a channel occupancy in a period of duration T x and ends the transmission of the UL transmission burst before the beginning of the idle duration of the period. When a UL or DL transmission burst is associated with a channel occupancy initiated by the UE in the period, the following applies:

[0448] - The UL or DL transmission burst is confined within the period and ends before the beginning of the idle duration of the period.

[0449] - If the gap between the UL transmission burst and any previous UL transmission burst in the period is more than 16us, then the UL transmission burst can be transmitted if the channel is sensed idle in at least a sensing slot duration T sl = 9us immediately preceding the UL transmission.

[0450] - If the gap between the DL transmission burst and any previous UL transmission burst in the period is more than 16us, then the DL transmission burst can be transmitted if the channel is sensed idle in at least a sensing slot duration T sl = 9us immediately preceding the DL transmission.

[0451] - If the gap between the DL transmission burst and any previous UL transmission burst in the period is at most 16us, then the DL transmission burst can be transmitted without sensing.

[0452] When a DL transmission burst is associated with a channel occupancy initiated by the UE in a duration T uThe DL transmission burst shall contain unicast user plane data or control information intended for UEs that initiate channel occupancy in the period associated with the DL transmission burst only if the gNB meets the condition that detection of additional DL transmissions at any UE would not be associated with channel occupancy initiated by the gNB following the procedures described in Clauses 4.3.1.2.3 and 4.3.1.2.4. The gNB can include additional transmissions intended to UEs other than the UEs that have initiated channel occupancy in the period or broadcast transmission in the DL transmission burst only if the gNB meets the condition that detection of additional DL transmissions at any UE would not be associated with channel occupancy initiated by the gNB following the procedures described in Clauses 4.3.1.2.3 and 4.3.1.2.4.

[0453] 4.4.5 Transmissions from sensing exemptions

[0454] In regions where channel sensing is required to access the channel for transmission and the regulation allows for short control signaling exemptions, the gNB / UE can transmit the following transmissions on the channel without sensing the channel:

[0455] - Transmission of discovery burst by gNB

[0456] - Transmission of first message in random access procedure by UE

[0457] When a gNB / UE transmits the above transmissions on the channel without sensing by utilizing the above exemptions, the total duration of such transmissions by the gNB / UE shall not occupy the corresponding channel more than 10 ms in any 100 ms interval.

[0458] A brief description of different types of LBT and / or channel access procedures from Unlicensed 5G New Radio: Challenges and Evaluation:

[0459] 2) LTE-LAA / NR-U based systems: To facilitate the operation of 5G NR-U (also known as LTE-LAA) in unlicensed bands, four LBT categories (CAT) are defined:

[0460] • CAT1 - LBT (Type 2C): The gNB can immediately access the channel without performing LBT. The COT can be up to 584 microseconds.

[0461] • CAT2 - LBT (Type 2A and 2B): The NR-U device must sense the channel for a fixed duration, Tfixed. If the channel remains idle during this period, the device can access the channel. In Type 2A, Tfixed is 25 microseconds, while in Type 2B, it is 16 microseconds.

[0462] • CAT3 - LBT: The NR-U device must backoff for a random period of time before accessing the channel. This random period is sampled from a fixed size contention window. The options for CAT3-LBT have been excluded from the specification.

[0463] • CAT4-LBT (Type 1): NR-U devices must back-off with exponential back-off according to the CSMA / CA procedure

[0464] 3GPP TR 38.889 V16.0.0 discusses the target range of the frequency band n46 5150 - 5925 MHz, which can be in unlicensed spectrum and / or can be a Time Division Duplex (TDD) band.

[0465] 4 Regulatory requirements

[0466] Regulatory requirements for the 4.15 GHz band

[0467] The range 5150 - 5925 MHz or parts thereof can potentially be used for licensed-assisted access to unlicensed operation. This represents a large amount of spectrum that can be used by operators to enhance their service provision in licensed bands. The above range can operate under a license-exempt mechanism or ISM, but has to be shared with existing mobile services and other existing services. The quality of service provided by the licensed mechanism can therefore not match. Unlicensed access is therefore considered complementary and does not reduce the need for additional allocations for licensed operation in terms of increasing demand for wireless broadband access.

[0468] Related is the consideration of global (international) ITU-R allocations and technologies provision first. These can be the basis to define globally coordinated bands for LAA and a starting point for requirements and limitations before considering local variations.

[0469] 3GPP TS 38.331 V16.5.0 discusses one or more information elements. The following quotes one or more sections of 3GPP TS 38.331 V16.5.0:

[0470] 6.3.5 Sidelink information elements

[0471] -SL-BWP-Config

[0472] The IE SL-BWP-Config is used to configure UE-specific NR sidelink communication on one specific sidelink bandwidth part.

[0473] SL-BWP-Config information element

[0474]

[0475]

[0476] The following quotes one or more sections of 3GPP TS 38.300 V16.6.0:

[0477] 5.6 Access to shared spectrum

[0478] 5.6.1 Overview

[0479] NR radio access operating with shared spectrum channel access can operate in different modes where the PCell, PSCell or SCell can be in shared spectrum, and the SCell can or can not be configured with uplink. The applicable deployment scenarios are described in Annex B.3.

[0480] The gNB operates in dynamic or semi-static channel access mode as described in TS 37.213

[37] . In both channel access modes, the gNB and UE can apply Listen-Before-Talk (LBT) before performing transmissions on cells configured with shared spectrum channel access. When LBT is applied, the transmitter listens / senses the channel to determine whether the channel is idle or busy, and performs transmission only when the channel is sensed to be idle.

[0481] RP-213678 discusses the application of sidelink techniques on unlicensed bands (e.g., bands n46 / n96 / n102) in order to increase data rates. The following quotes one or more sections of RP-213678:

[0482] 3 Adjustments

[0483] In Rel-16, sidelink communication was developed mainly in RAN to support advanced V2X applications. In Rel-17, SA2 studies and standardizes proximity-based services, including public safety and commercial related services. As part of Rel-17, power saving solutions (e.g., partial sensing, DRX) and inter-UE coordination have been developed in RANI and RAN2 to improve power consumption of battery-limited terminals and reliability of sidelink transmissions.

[0484] While NR sidelink was initially developed for V2X applications, there is growing interest in the industry to extend the applicability of NR sidelink to commercial use cases. For commercial sidelink applications, two key requirements have been identified:

[0485] - Increased sidelink data rates

[0486] - Support for new carrier frequencies for sidelink

[0487] Increased sidelink data rates are motivated by applications such as sensor information (video) sharing between vehicles with high levels of driving automation. Commercial use cases can require data rates in excess of what is possible in Rel-17. Increased data rates can be achieved through support of sidelink carrier aggregation and sidelink on unlicensed spectrum. In addition, increased data rates can be more efficiently supported on FR2 through enhancements to FR2 sidelink operation. While support of new carrier frequencies and larger bandwidths will also allow for improved data rates, the main benefit will come from making sidelink more suitable for a wider range of applications. More specifically, through support of unlicensed spectrum and enhancements in FR2, sidelink will be in a better position to be implemented in commercial devices, as the utilization of ITS bands is limited to ITS safety related applications.

[0488] …

[0489] 4Objectives 1.

[0491] o […]

[0492] 2. Study and specify support for sidelink on unlicensed spectrum for Mode 1 and Mode 2, with Uu operation for Mode 1 limited to licensed spectrum [RAN1, RAN2, RAN4]

[0493] - Channel access mechanisms from NR-U should be re-used for sidelink unlicensed operation

[0494] NR Rel-16 can be the first release for NR sidelink vehicle-to-everything (V2X), and standards (e.g., associated with NR Rel-16) can meet one or more requirements defined by 3GPP Technical Specification Group Services and System Aspects (TSG SA) Working Group 1 (WG1) (SA1). Over time, as more and more devices need higher processing and / or higher data rates, sidelink transmissions on wider frequency resources can be needed. However, current frequency bands that support the PC5 interface and / or sidelink transmissions can not be sufficient. Thus, introducing sidelink transmissions on unlicensed spectrum (e.g., shared spectrum) under large spectrum availability can be a targeted solution. To fairly coexist with the same or different radio access technologies (RATs) or other devices in different technologies in unlicensed spectrum (e.g., WiFi), listen before talk (LBT) can be needed. LBT is an energy detection and / or sensing technique. For example, a device can determine whether a transmission is allowed based on an LBT outcome (which can indicate idle or busy) before the transmission. Unlicensed new radio for Uu interface is discussed in 3GPP TS 37.213 V17.0.0 and / or Unlicensed 5G New Radio: Challenges and Evaluation. There are multiple types of LBT, such as short LBT (e.g., Category 1 LBT (CAT1-LBT), and / or Category 2 LBT (CAT2-LBT)) and / or long LBT (e.g., Category 4 LBT (CAT4-LBT)). For short LBT, a device can be allowed to perform a transmission in the following cases: (i) no LBT (e.g., no LBT can be performed before the transmission) and / or (ii) with a relatively short LBT (e.g., a device can perform a relatively short LBT before the transmission, which can be associated with a duration that is less than a duration of a long LBT). For long LBT, a device can need to perform a transmission with a LBT that has a relatively longer time (e.g., a long LBT can be performed with more sensing slots idle compared to a short LBT, and / or can be performed with a backoff). For sidelink reception, continuously monitoring, receiving, and / or detecting sidelink resources can be an assumption in a sidelink device. Alternatively and / or additionally, there can be multiple channel access modes (e.g., two channel access modes) in unlicensed new radio (NR-U), including (i) semi-static channel access (e.g., a frame-based equipment (FBE)), and / or (ii) dynamic channel access (e.g., a load-based equipment (LBE)). According to 3GPP TS 37.213 V17.0.0, FBE can be intended for environments where the absence of other technologies is guaranteed (e.g., FBE can be beneficial for a network-controlled environment). Due to a network-controlled environment, there can be a radio access network (RAN) (e.g., one RAN) on unlicensed bands, which can be beneficial for network vendors to deploy intelligent factors and support services, which can need higher data rates.

[0495] For FBE in NR-U, a gNB can configure a periodic channel occupancy initiated by the gNB within (e.g., every) a periodicity (denoted as Tx) within (e.g., every) two consecutive radio frames. Each Tx can include a time span Tz = max(0.05 x Tx, 100 microseconds) (e.g., a duration of Tz is equal to a maximum of a first value of 0.05 x Tx and a second value of 100 microseconds) at the end of the Tx. The time span Tz is used to perform LBT for a next periodic Tx. In some instances, the channel occupancy in each Tx can be at most Tx - Tz. The gNB can perform LBT during Tz for determining whether the channel is idle. If the channel is sensed to be idle during Tz (e.g., if an LBT result of an LBT performed during Tz indicates that the channel is idle), the gNB can initiate channel occupancy within a next (e.g., consecutive) Tx. Alternatively and / or additionally, to support latency requirements of ultra-reliable and low latency communications (URLLC), a UE can have a configuration for periodic channel occupancy initiated by the UE within (e.g., every) a second periodicity (denoted as Tu) within (e.g., every) two consecutive radio frames. Each Tu can include a second time span Tz' = max(0.05 x Tu, 100 microseconds) (e.g., a duration of Tz' is equal to a maximum of a first value of 0.05 x Tu and a second value of 100 microseconds) at the end of the Tu. The second time span Tz' is used to perform LBT for a next periodic Tu. In some instances, the channel occupancy in each Tu can be at most Tu - Tz'. The UE can perform LBT during Tz' for determining whether the channel is idle. If the channel is sensed to be idle during Tz' (e.g., if an LBT result of an LBT performed during Tz' indicates that the channel is idle), the UE can initiate channel occupancy within a next (e.g., consecutive) Tu. In some instances, Tx can be an integer and can be a multiple of Tu. The gNB can be allowed to share its occupancy (e.g., channel occupancy) with the UE for performing uplink transmissions (e.g., the gNB can share its occupancy with the UE for performing uplink transmissions) and / or the UE can be allowed to share occupancy (e.g., channel occupancy of the UE) with the gNB for performing downlink scheduling (e.g., the UE can share occupancy with the gNB for performing downlink scheduling). However, there can be a restriction that when the gNB uses occupancy (e.g., channel occupancy) initiated by UE1, a downlink (DL) transmission burst should contain transmissions to UE1.In some instances, for FBE, when a UE detects a gNB’s DL transmission (e.g., the DL transmission can include at least one of a downlink control information (DCI), a channel state information-reference signal (CSI-RS), a DL burst, a synchronization signal (SS), a physical broadcast channel (PBCH), a physical downlink shared channel (PDSCH), etc.), the UE can consider the gNB has an occupation (e.g., a channel occupation) in the current period Tx. If the UE is scheduled and / or configured to perform a UL transmission within the channel occupation in the current period Tx (e.g., the UL transmission is not within the time span Tz in the current period Tx), the UE can perform the UL transmission without LBT or after CAT2-LBT (e.g., CAT2-LBT can be performed in one sensing slot).

[0496] In an instance, in FBE context, there can be a gNB period (e.g., Tx) and a UE period (e.g., Tu). The gNB associated with the gNB period can be associated with a UE-type road side unit (RSU). In an instance, since sidelink resources can be scheduled in licensed spectrum by DCI format 3_0, verifying gNB occupation for the current gNB’s period by detecting a DL transmission can not be sufficient. One issue is to ensure the UE knows whether the scheduled resource from DCI format 3_0 is using the gNB’s period or the UE period (e.g., the UE should know which period to use), and / or how (and / or whether) the UE knows the scheduled resource is associated with a channel occupancy (CO) initiated by the gNB or by the UE (itself) (e.g., the UE should know whether the scheduled resource is associated with a channel occupancy initiated by the gNB or a channel occupancy initiated by the UE). Without resolving this issue, if one of multiple (e.g., up to three) scheduled sidelink resources from DCI format 3_0 is scheduled in an idle duration of the gNB’s period, the UE can be confused whether the UE can use the one sidelink resource to perform a sidelink transmission using the gNB’s period. In some instances, since there can be up to 3 scheduled resources from DCI format 3_0, it can be further discussed whether the UE uses one, some, and / or all of the 3 scheduled resources for sidelink transmission, since the UE can not be able to pass LBT for initiating a CO in some cases. In some instances, when a scheduled resource overlaps with an idle duration, it can be an issue to determine (based on, e.g., UE’s behavior) whether to perform a sidelink transmission on the scheduled resource.

[0497] Another issue is associated with physical sidelink feedback channel (PSFCH) transmissions. In Rel-16, PSFCH resources can be configured (e.g., preconfigured) per resource pool in a periodic manner. In other words, a single PSFCH period of 1, 2, or 4 slots can be configured (e.g., preconfigured) per resource pool, which can mean that there is a PSFCH in the resource pool (e.g., per) 1, 2, or 4 slots. The timing of the PSFCH in the slot with the PSFCH resource can include one or more last symbols that can be used for sidelink transmissions. A slot can include 14 symbols (e.g., symbol indices 0~13), and the last symbol (symbol index 13) can not be available for sidelink transmissions due to its use as a gap for transition. The PSFCH can include 2 symbols, where 1 of the 2 symbols can be used for repetition. The PSFCH can be in symbol index 11 and symbol index 12, which can be the last two available symbols in the slot for sidelink. Using the last two available symbols in the slot for sidelink can benefit from the self-contained slot and / or the short duration (e.g., 2 symbols) of the PSFCH for fast sidelink feedback, and / or can enable reduced interference to physical sidelink control channel (PSCCH) transmissions and / or physical sidelink shared channel (PSSCH) transmissions. There can be symbol index 10 (of the symbols in the slot), which can act as a gap for transition between PSSCH and PSFCH. However, when it comes to sidelink on unlicensed spectrum, when a receiver UE (RX UE) (has received a PSSCH and needs to transmit a PSFCH), the (e.g., only few) options for the RX UE to a CO are (i) use another UE initiated CO, or (ii) use a previously initiated CO (e.g., if available) that covers the PSFCH resource (e.g., due to the PSFCH not aligning to the slot boundary) initiated by the RX UE. Thus, one or more of the techniques provided herein can be implemented to enhance PSFCH transmissions in unlicensed sidelink (SL-U) (e.g., sidelink in unlicensed spectrum).

[0498] In some instances, a sidelink burst (e.g., one sidelink burst) can include one or more sidelink transmissions. In some instances, a time gap between two of the one or more sidelink transmissions is at most a time threshold (e.g., 16 microseconds). For example, there can be a time gap of at most the time threshold between each pair of (consecutive) sidelink transmissions of the one or more sidelink transmissions.

[0499] The concepts of the present disclosure can be that a first UE can transmit sidelink hybrid automatic repeat request (HARQ) feedback on a PSCCH and / or a PSSCH. In some instances, it can be beneficial and / or logical to transmit the sidelink HARQ feedback at the beginning of a fixed frame period (FFP) (rather than transmitting the sidelink HARQ feedback outside of the beginning of the FFP, e.g., in a middle portion of the FFP or at the end of the FFP). However, in some scenarios, it can be difficult to transmit the sidelink HARQ feedback at the beginning of the FFP. In some instances, the first UE can receive a request from a different UE. In some instances, the request from the different UE can indicate (e.g., instruct) the first UE to transmit one or more sidelink HARQ feedbacks on a PSCCH and / or a PSSCH. In some instances, the transmission of the sidelink HARQ feedback on the PSCCH, the PSSCH, and / or a PSFCH can be a retransmission for a (previous) sidelink HARQ feedback. In some instances, the transmission being a retransmission for a (previous) sidelink HARQ feedback can mean that the first UE is not available to transmit the sidelink HARQ feedback on the PSFCH, and thus can need to perform the retransmission to transmit the sidelink HARQ feedback. In some instances, the first UE can transmit the sidelink HARQ feedback on a 1st stage sidelink control information (SCI) (e.g., SCI format 1-A), a 2nd stage SCI (e.g., SCI format 2-X), or a medium access control (MAC) control element (CE) (MAC CE). In some instances, the transmission of the sidelink HARQ feedback (e.g., on the 1st stage SCI, the 2nd stage SCI, or the MAC CE) can be a retransmission after an original PSFCH location for the sidelink HARQ feedback (e.g., the original PSFCH location can be an original PSFCH location that was scheduled for the sidelink HARQ feedback). In some instances, the transmission of the sidelink HARQ feedback (e.g., on the 1st stage SCI, the 2nd stage SCI, or the MAC CE) can be earlier than the original PSFCH location for the sidelink HARQ feedback. In some instances, the transmission CE of the sidelink HARQ feedback (e.g., on the 1st stage SCI, the 2nd stage SCI, or the MAC CE) can provide information related to the one or more sidelink HARQ feedbacks. In some instances, the first UE can perform the transmission CE of the sidelink HARQ feedback (e.g., on the 1st stage SCI, the 2nd stage SCI, or the MAC CE) in response to the request and / or in response to a condition associated with a timer, a counter, and / or a window being satisfied (e.g., the condition can be satisfied when a timer expires, a counter reaches a threshold, a window begins or ends, etc.). In some instances, there can be a logical channel identifier (LCID) (e.g., a particular LCID) for the MAC CE that carries the one or more sidelink HARQ feedbacks.In some instances, a number of sidelink HARQ feedbacks of the one or more sidelink HARQ feedbacks can be based on a fixed and / or pre-defined number. In some instances, a number of sidelink HARQ feedbacks of the one or more sidelink HARQ feedbacks can be based on higher layer signaling and / or configuration. In some instances, a number of sidelink HARQ feedbacks of the one or more sidelink HARQ feedbacks can be based on a number of HARQ processes of a requesting UE (e.g., a number of HARQ processes associated with the requesting UE, which can correspond to a different UE that transmitted a request to the first UE indicating to transmit the one or more sidelink HARQ feedbacks) or a number of HARQ processes of a transmitter UE (TX UE) (e.g., a number of HARQ processes associated with the TX UE), where the transmitter UE corresponds to a UE that transmitted a sidelink transmission associated with (e.g., requested and / or has) the one or more sidelink HARQ feedbacks. In some instances, the first UE and one or more UEs including the TX UE and / or the requesting UE can exchange (e.g., initially exchange) information indicating a number of sidelink HARQ feedbacks of the one or more sidelink HARQ feedbacks (e.g., the first UE can transmit and / or receive information from the TX UE and / or the requesting UE). In some instances, the exchange (e.g., transmission and / or reception of information) can be based on PC5 radio resource control (RRC) signaling. In an instance, assuming the TX UE or the requesting UE has X number of sidelink HARQ processes, the TX UE or the requesting UE can indicate to the first UE that a number of sidelink HARQ feedbacks is at most X (e.g., the TX UE or the requesting UE informs the first UE that a number of sidelink HARQ feedbacks can be at most X number). When the first UE transmits the one or more sidelink HARQ feedbacks, a number of the one or more sidelink HARQ feedbacks can be X. In some instances, X = 16, and thus the first UE can transmit 16 bits corresponding to a sidelink HARQ process number of the TX UE or the requesting UE. In some instances, the one or more sidelink HARQ feedbacks (transmitted in a MAC CE, e.g., one MAC CE) can be transmitted with data associated with the TX UE or the requesting UE. In some instances, the data associated with the TX UE or the requesting UE can correspond to available data associated with one or more logical channels having a destination corresponding to the TX UE or the requesting UE. In some instances, the first UE can transmit a MAC CE (e.g., the one MAC CE) carrying the one or more sidelink HARQ feedbacks without including other data associated with logical channels.In some instances, the first UE can transmit a MAC CE (e.g., the one MAC CE) carrying the one or more sidelink HARQ feedbacks without including other MAC CEs (e.g., the one MAC CE carrying the one or more sidelink HARQ feedbacks can be transmitted in a transmission without transmitting any other MAC CEs in the transmission). In some instances, the first UE can transmit a MAC CE (e.g., the one MAC CE) carrying the one or more sidelink HARQ feedbacks with other MAC CEs (e.g., a sidelink (SL) discontinuous reception (DRX) MAC CE and / or a SL channel state information (CSI) reporting MAC CE). For example, one or more other MAC CEs (in addition to, e.g., the one MAC CE) can be included in the transmission of the one MAC CE carrying the one or more sidelink HARQ feedbacks.

[0500] In some instances, a parameter (e.g., in a pool configuration and / or a PC5 RRC configuration) can indicate whether retransmission of one or more sidelink HARQ feedbacks is supported. In some instances, if the parameter indicates that retransmission of one or more sidelink HARQ feedbacks is not supported, the first UE cannot retransmit a sidelink HARQ feedback on a pool (e.g., a sidelink resource pool associated with the parameter). In some instances, a channel busy ratio (CBR) can be used to enable and / or disable a feature of retransmission of sidelink HARQ feedback. In some instances, if the CBR is above a threshold (and / or if the CBR indicates that a congestion level is above a congestion threshold), the first UE is not allowed to retransmit the one or more sidelink HARQ feedbacks.

[0501] In an instance, the first UE receives PSCCH1, PSSCH1, and / or PSFCH from the second UE. The first UE can determine to transmit sidelink HARQ feedback on the PSFCH in response to the PSCCH1, PSSCH1, and / or PSFCH. However, the first UE can not be available to transmit the sidelink HARQ feedback on the PSFCH. In some instances, the first UE can prioritize PSFCH reception and / or UL transmission over performing PSFCH transmission (e.g., the first UE can prioritize PSFCH reception and / or UL transmission over PSFCH transmission). In some instances, the first UE can be unable to perform LBT for an access channel for transmitting the sidelink HARQ feedback on the PSFCH. In some instances, for contention window size adjustment, sidelink HARQ feedback for the second UE can be beneficial for adjusting the contention window size (e.g., the second UE can use the sidelink HARQ feedback for adjusting the contention window size). In some instances, the first UE can transmit the sidelink HARQ feedback on PSCCH2, PSSCH2, and / or PSFCH. In some instances, PSCCH2 is different from PSCCH1 and / or PSSCH2 is different from PSSCH1. In some instances, PSSCH2 can deliver / transmit / contain the sidelink HARQ feedback with or without data from one or more logical channels (e.g., one or more other logical channels). In this disclosure, the term “deliver / transmit / contain” can refer to delivering, transmitting, and / or containing. In some instances, the one or more logical channels can include a sidelink control channel (SCCH) and / or a sidelink traffic channel (STCH). In some instances, PSSCH2 can deliver / transmit / contain the sidelink HARQ feedback with or without: (i) a MAC CE including a SL CSI report, (ii) a MAC CE including SL DRX related signaling, (iii) a MAC CE including inter-UE coordination information (e.g., information indicating one or more preferred resources and / or one or more non-preferred resources), and / or (iv) a request. In some instances, PSSCH2 can deliver / transmit / contain a new transmission of a TB / MAC PDU. In this disclosure, the term “TB / MAC PDU” can refer to a transport block (TB) and / or a MAC packet data unit (PDU) (MAC PDU). In some instances, PSSCH2 can be a retransmission of a TB / MAC PDU. In some instances, PSCCH2 can schedule the new transmission or the retransmission. In some instances, a new data indicator (NDI) for PSCCH2, PSSCH2, and / or PSFCH can or can not be toggled.

[0502] In some instances, the first UE can transmit the sidelink HARQ feedback on the PSCCH / PSSCH / PSFCH in response to a timer, a counter, and / or a window satisfying (e.g., reaching and / or meeting) a condition. In this disclosure, the term “PSCCH / PSSCH / PSFCH” can refer to PSCCH, PSSCH, and / or PSFCH. In some instances, the condition can be a condition that a timer expires, a counter exceeds a threshold, and / or a timing exceeds a window that can start from an original timing of a PSFCH or from a time (e.g., timing) of an original PSCCH / PSSCH / PSFCH in response to which the sidelink HARQ feedback is responsive. In some instances, the first UE can transmit the sidelink HARQ feedback on the PSCCH / PSSCH / PSFCH without a request from the second UE.

[0503] In some instances, the first UE can reset and / or restart the timer when (e.g., in response to and / or after) the first UE receives the PSCCH / PSSCH / PSFCH (e.g., a retransmission of the PSCCH / PSSCH / PSFCH) from the second UE. In some instances, the first UE can decrease the timer by a value (e.g., 1) when (e.g., in response to and / or after) the first UE does not detect or receive the PSCCH / PSSCH / PSFCH (e.g., a retransmission of the PSCCH / PSSCH / PSFCH) from the second UE in a time unit. In some instances, the time unit can be at least one of: a slot (e.g., one slot) in a sidelink resource pool, 1 millisecond (ms), 1 reservation period value, 1 physical slot (whether or not the slot belongs to, e.g., a sidelink resource pool). Alternatively and / or additionally, whether the first UE performs an action including resetting or restarting the timer can be based on whether the first UE transmits sidelink HARQ feedback on another PSFCH resource (e.g., different from the PSFCH resource of the PSCCH / PSSCH / PSFCH). In some instances, if the first UE can transmit a second sidelink HARQ feedback in response to the retransmission of the PSCCH / PSSCH / PSFCH (e.g., the first UE is able to transmit the second sidelink HARQ feedback due to LBT success), then the first UE can reset and / or restart the timer. In some instances, if the first UE is unable to transmit a second sidelink HARQ feedback in response to the retransmission of the PSCCH / PSSCH / PSFCH (e.g., the first UE is unable to transmit the second sidelink HARQ feedback due to LBT failure again or due to no retransmission of the PSCCH / PSSCH / PSFCH), then the first UE does not start or restart the timer. In some instances, the retransmission of the PSCCH / PSSCH / PSFCH can have the same HARQ process number of the second UE, and can not switch NDI for the retransmission (e.g., whether to switch NDI is based on an NDI field in a SCI scheduling the retransmission and an NDI field in a SCI scheduling an initial / new transmission of the PSCCH / PSSCH / PSFCH for the same TB / MAC PDU). The initial / new transmission can correspond to an initial and / or new transmission, e.g., a transmission that is not a retransmission.

[0504] In some instances, the first UE can set the counter to 0, set the counter to a starting value, or decrease the value of the counter when (e.g., in response to and / or after) the first UE receives a PSCCH / PSSCH / PSFCH (e.g., a retransmission of the PSCCH / PSSCH / PSFCH) from the second UE. In some instances, the first UE increases the counter by a value (e.g., 1) once the first UE does not detect or receive a PSCCH / PSSCH / PSFCH (e.g., a retransmission of the PSCCH / PSSCH / PSFCH) from the second UE in a time unit. In some instances, the time unit can be at least one of: a slot (e.g., one slot) in a sidelink resource pool, 1 ms, 1 reservation period value, 1 physical slot (whether or not the slot belongs to, e.g., a sidelink resource pool). Alternatively and / or additionally, whether the first UE performs the actions including setting the counter to 0, setting the counter to a starting value, or decreasing the value of the counter can be based on whether the first UE transmits sidelink HARQ feedback on another PSFCH resource. In some instances, if the first UE can transmit a second sidelink HARQ feedback in response to a retransmission of the PSCCH / PSSCH / PSFCH (e.g., the first UE is able to transmit the second sidelink HARQ feedback due to LBT success), then the first UE can perform the actions including setting the counter to 0, setting the counter to a starting value, or decreasing the value of the counter. In some instances, if the first UE cannot transmit a second sidelink HARQ feedback in response to a retransmission of the PSCCH / PSSCH / PSFCH (e.g., the first UE is not able to transmit the second sidelink HARQ feedback due to LBT failure again or due to no retransmission of the PSCCH / PSSCH / PSFCH), then the first UE (i) can not set the counter to 0 or a starting value, and / or (ii) can increase the counter by one. In some instances, the threshold value is 32 (e.g., 32 slots). In some instances, the threshold value is a predetermined and / or preconfigured value. In some instances, the retransmission of the PSCCH / PSSCH / PSFCH can have the same HARQ process number of the second UE, and can not switch NDI for the retransmission.

[0505] In some instances, the first UE determines a window starting from a timing of an original PSCCH / PSSCH / PSFCH in response to which the sidelink HARQ feedback is responsive (e.g., the window starts from the timing of the original PSCCH / PSSCH / PSFCH). The timing of the original PSCCH / PSSCH / PSFCH can correspond to (i) an initial timing of the PSCCH and / or PSSCH transmission, or (ii) a timing of the PSFCH in response to the initial timing of the PSCCH / PSSCH transmission (e.g., including a timing of the PSFCH in response to the sidelink HARQ feedback of the PSCCH / PSSCH transmission). For example, the first UE can receive PSCCH1 and / or PSSCH1 from the second UE in slot n. The first UE can determine to transmit sidelink HARQ feedback on a PSFCH in slot m, where the sidelink HARQ feedback is in response to PSCCH1 and / or PSSCH1. In some instances, the window starts from a starting symbol of one of slot n, slot m, slot n+1, or slot m+1 (e.g., a starting timing of the window can be one of slot n, slot m, slot n+1, or slot m+1). In some instances, before an end of the window (e.g., before an ending timing corresponding to a certain time period of the window), if the first UE receives and / or detects PSCCH / PSSCH / PSFCH (e.g., a retransmission of PSCCH / PSSCH / PSFCH) from the second UE, the first UE can determine (e.g., redetermine) a starting timing of the window (e.g., an updated starting timing of the window). In some instances, before an end of the window, if the first UE can transmit sidelink HARQ feedback on another PSFCH resource (e.g., in slot k different from slot n and slot m), the first UE can determine (e.g., redetermine) a starting timing of the window (e.g., an updated starting timing of the window). In some instances, a window length of the window is 32 slots. In some instances, the window length is a predetermined and / or preconfigured value. In some instances, before an end of the window, the first UE can retransmit the sidelink HARQ feedback on another PSFCH resource (e.g., a PSFCH resource different from a PSFCH resource associated with the original PSCCH / PSSCH / PSFCH in response to which the sidelink HARQ feedback is responsive). In some instances, the retransmission of PSCCH / PSSCH / PSFCH can have a same HARQ process number of the second UE, and can not switch NDI for the retransmission.In some instances, the first UE can transmit the sidelink HARQ feedback on the PSCCH / PSSCH / PSFCH at and / or after a time and / or slot corresponding to a sum of the window length and one of slots n, n+1, m, or m+1 (e.g., if the window length is 32 slots and the starting timing of the window is slot n, the first UE can transmit the sidelink HARQ feedback on the PSCCH / PSSCH / PSFCH at and / or after slot n+32).

[0506] In some instances, in response to the timer expiring, the counter reaching the threshold, and / or reaching the end of the window (and / or after the window), the first UE can trigger resource selection for transmitting the sidelink HARQ feedback on the PSCCH / PSSCH / PSFCH. In mode-1 (e.g., sidelink resource allocation mode 1), the first UE can transmit a request to a network node for requesting one or more sidelink resources. In mode-2 (e.g., sidelink resource allocation mode 2), the first UE can select one or more resources (e.g., one or more PSCCH / PSSCH / PSFCH resources) for transmitting the sidelink HARQ feedback based on sensing results (whether the sensing results are determined via full sensing, partial sensing, or no sensing, for example).

[0507] In some instances, transmitting sidelink HARQ feedback on PSCCH / PSSCH / PSFCH can be for a sidelink resource pool without PSFCH (e.g., a first UE can use PSCCH and / or PSSCH for transmitting sidelink HARQ feedback according to the techniques herein when the first UE is configured with a sidelink resource pool without PSFCH). Alternatively and / or additionally, transmitting sidelink HARQ feedback on PSCCH / PSSCH / PSFCH (rather than, for example, using only PSFCH to transmit sidelink HARQ feedback) can be performed for a sidelink resource pool with PSFCH (e.g., a first UE can use PSCCH / PSSCH / PSFCH for transmitting sidelink HARQ feedback according to the techniques herein when the first UE is configured with a sidelink resource pool with PSFCH). In some instances, transmitting sidelink HARQ feedback on PSCCH / PSSCH / PSFCH can be a mix of blind retransmission and HARQ-based retransmission (e.g., a first UE can transmit sidelink HARQ feedback on PSCCH / PSSCH / PSFCH using one or more features of blind retransmission and one or more features of HARQ-based retransmission). In Rel-16 NR V2X, there can be a PSFCH occasion within a time gap between two sidelink slots for PSSCH carrying the same TB in a sidelink resource pool. For example, when a TB is associated with enabled sidelink HARQ feedback, a Rel-16 UE can not perform sidelink transmission on the two sidelink slots if a restriction on PSFCH occasions and / or time gap is not met. However, according to some embodiments of the disclosure, PSCCH / PSSCH / PSFCH can be used to transmit sidelink HARQ feedback, and the restriction can not apply (e.g., the restriction can not prevent a first UE from transmitting sidelink HARQ feedback using PSCCH / PSSCH / PSFCH). In some instances, transmitting sidelink HARQ feedback on PSCCH / PSSCH / PSFCH can be for a UE not prioritizing transmitting PSFCH (e.g., prioritizing UL or PSFCH reception). For example, when a first UE prioritizes UL transmission and / or PSFCH reception over PSFCH transmission, the first UE can use PSCCH / PSSCH / PSFCH for transmitting sidelink HARQ feedback according to the techniques herein. In some instances, transmitting sidelink HARQ feedback on PSCCH / PSSCH / PSFCH can be for a UE performing sidelink transmission on unlicensed spectrum (e.g., frequency bands n46 / n96 / n102). For example, when a first UE performs sidelink transmission on unlicensed spectrum, the first UE can use PSCCH / PSSCH / PSFCH for transmitting sidelink HARQ feedback according to the techniques herein.In some instances, one basic theory is that there can be no idle duration of a previous FFP before a PSFCH (e.g., each PSFCH) because the PSFCH can be in a middle portion of the FFP.

[0508] In some instances, SCI (1st stage SCI or 2nd stage SCI) can provide information indicating whether to use PSSCH and / or PSFCH for delivering and / or transmitting sidelink HARQ feedback.

[0509] In some instances, a SCI (a first stage SCI or a second stage SCI) can provide information indicating whether the SCI and / or a sidelink assignment includes information related to one or more sidelink HARQ feedbacks. In some instances, in response to a TX UE receiving the SCI (e.g., the TX UE can be different from the first UE), the TX UE can identify a HARQ process associated with the SL HARQ feedback (e.g., the TX UE can determine which HARQ process is associated with the SL HARQ feedback). The association of the one or more sidelink HARQ feedbacks (e.g., the sidelink HARQ feedbacks in the SCI and / or the sidelink assignment) with one or more HARQ processes of the TX UE can be based on an explicit indication and / or an implicit indication. For example, the explicit indication and / or the implicit indication can indicate which HARQ process (e.g., of the TX UE) is associated with the sidelink HARQ feedback (in the SCI and / or the sidelink assignment). In instances of the explicit indication, the first UE can indicate a HARQ process number for the SL HARQ feedback (e.g., the first UE can indicate which HARQ process number is for the SL HARQ feedback). In some instances, the HARQ process number for the SL HARQ feedback is based on a HARQ process number of the first UE. Alternatively and / or additionally, the HARQ process number for the SL HARQ feedback can be based on a HARQ process number of the TX UE and / or based on a HARQ process number indicated by a first SCI that schedules a sidelink transmission (e.g., from the TX UE) in response to which the sidelink HARQ feedback is. In instances of the implicit indication, the first UE can transmit a plurality of sidelink HARQ feedbacks associated with a plurality of HARQ process numbers. For example, the plurality of sidelink HARQ feedbacks can include X sidelink HARQ feedbacks, which can be indicated by X bits associated with X HARQ process numbers. The first UE can transmit the X bits. An order of the X bits can be based on an increasing or decreasing order, and / or can be based on one or more HARQ process numbers (e.g., the X HARQ process numbers). For example, the order of the X bits can be based on an increasing or decreasing order of the X HARQ process numbers. In some instances, the HARQ process numbers are based on a HARQ process number of the TX UE and / or based on a HARQ process number indicated by a first SCI that schedules a sidelink transmission (e.g., from the TX UE) in response to which the sidelink HARQ feedback is. Alternatively and / or additionally, the HARQ process numbers can be based on a HARQ process number of the first UE. In an instance, the first UE can receive a first SCI that schedules a sidelink transmission associated with a HARQ process number (HPN) = 2. In an instance, the HPN = 2 indicated by the first SCI can be associated with a HARQ process number of the TX UE (rather than being associated with a HARQ process number of the first UE, for example).It can be appreciated that the first UE can select a HARQ process number of the first UE, e.g., a HARQ process number corresponding to HPN = 3. In some instances, the first UE knows that its own HPN = 3 is associated with the TX UE’s HPN = 2. In some instances, based on the association (e.g., between HPN = 3 associated with the first UE and HPN = 2 associated with the TX UE), when the first UE transmits one or more sidelink HARQ feedbacks, the first UE will set (and / or determine) the TX UE’s HPN = 2 based on the outcome of the first UE’s (its own) HPN = 3. In some instances, for one or more other locations / occasions other than HPN = 2 (e.g., one or more other HPNs other than HPN = 2), if the first UE does not have a received sidelink transmission from the TX UE, the first UE can set a negative acknowledgement (NACK) or nothing (e.g., the UE can set the one or more other locations / occasions to NACK and / or nothing) on the one or more other locations / occasions. In this disclosure, the term “location / occasion” can refer to a location and / or an occasion. In some instances, for one or more other locations / occasions other than HPN = 2 (e.g., one or more other HPNs other than HPN = 2), if the first UE does not have a received sidelink transmission from a UE that transmits a request for sidelink HARQ feedback on PSCCH and / or PSSCH or transmits a request for retransmission of sidelink HARQ feedback, the first UE can set a NACK or nothing (e.g., the UE can set the one or more other locations / occasions to NACK and / or nothing) on the one or more other locations / occasions.

[0510] In some instances, the TX UE and the first UE can have a common understanding regarding a size of X. In some instances, for unicast, the TX UE and the first UE can have PC5-RRC signaling to have the size of X (e.g., the PC5-RRC signaling can be generated to have the size corresponding to X). In some instances, for groupcast, the TX UE and the first UE can have group-specific signaling to have the size of X (e.g., the group-specific signaling can be generated to have the size corresponding to X). In some instances, the size of X can be associated with at least one of a pool, a bandwidth part (BWP), one or more LBT bands, a carrier, a cast type, etc. (e.g., the size of X can be at least one of a pool-specific, a BWP-specific, an LBT band-specific, a carrier-specific, a cast type-specific, etc.).

[0511] In some instances, a first SCI (1st stage SCI or 2nd stage SCI) from a TX UE can provide information indicating whether previous and / or pending sidelink HARQ feedback is requested. In response to the first UE receiving the first SCI, the first UE can transmit one or more sidelink HARQ feedbacks (e.g., on PSSCH and / or PSCCH and / or PSFCH) associated with one or more sidelink HARQ processes. In response to receiving the first SCI, the first UE can transmit one or more NDI associated with the one or more sidelink HARQ processes. Prior to the sidelink transmission, the TX UE can perform sensing on a channel. In some instances, the first SCI schedules the sidelink transmission and requests.

[0512] In some instances, one or more sidelink HARQ feedbacks in response to one or more sidelink transmissions can be transmitted together. In some instances, one or more sidelink HARQ feedbacks transmitted in a same PSCCH and / or a same PSSCH are associated with (e.g., in response to) one or more sidelink transmissions from a same TX UE. Alternatively and / or additionally, one or more sidelink HARQ feedbacks transmitted in a same PSCCH and / or a same PSSCH can be associated with a same source ID (source identity) (e.g., the one or more sidelink HARQ feedbacks can be associated with a same layer 2 source ID). In some instances, one or more sidelink HARQ feedbacks transmitted in a same PSCCH and / or a same PSSCH can not be allowed to be associated with (e.g., in response to) one or more sidelink transmissions from different TX UEs and / or can not be allowed to be associated with different source IDs (e.g., different layer 2 source IDs).

[0513] In some instances, one or more sidelink HARQ feedbacks can be associated with a plurality of sidelink HARQ processes (e.g., in a MAC entity). The plurality of sidelink HARQ processes can correspond to a plurality of HARQ processes (e.g., in a MAC entity) for sidelink. In some instances, one or more sidelink HARQ feedbacks transmitted in a same PSCCH and / or a same PSSCH can be associated with (e.g., in response to) a plurality of sidelink HARQ processes associated with a same source ID (e.g., a same layer 2 source ID). In some instances, one or more sidelink HARQ feedbacks transmitted in a same PSCCH and / or a same PSSCH can not (and / or can not be allowed) to be allowed to be associated with (and / or in response to) sidelink HARQ processes associated with different source IDs (e.g., different layer 2 source IDs).

[0514] Figure 5An example scenario is shown in which a RX UE receives a PSCCH / PSSCH 502 (e.g., a PSCCH and / or a PSSCH) from a TX UE. A first HPN (e.g., “HPN 1”) of the TX UE (e.g., HPN 1 in Figure 5 X (e.g., HPN 1 = X can be the HPN of the TX UE for the PSCCH / PSSCH 502). A second HPN (e.g., “HPN 2”) of the RX UE (e.g., HPN 2 in Figure 5HPN 2) equals Y (e.g., HPN 2=Y can be the HPN of the RX UE for the PSCCH / PSSCH 502). In some instances, the TX UE can transmit an indication of the TX UE’s HPN 1=X to the RX UE (e.g., the PSCCH / PSSCH 502 can include the indication). The RX UE can process 504 the PSCCH / PSSCH 502 based on the RX UE’s HPN 2=Y. In some instances, at 506, the RX UE can fail an LBT (e.g., a sensing result of the LBT can indicate busy) for transmitting SL HARQ feedback (e.g., the SL HARQ feedback can indicate whether the PSCCH / PSSCH 502 is successfully received by the RX UE) on a first PSFCH in response to the PSCCH / PSSCH 502 from the TX UE. In some instances, the RX UE can perform a retransmission 508 of the SL HARQ feedback to the TX UE. In some instances, the RX UE can perform the retransmission 508 in response to a request from the TX UE. In some instances, the SL HARQ feedback is carried by a 1st stage SCI, a 2nd stage SCI, a MAC CE, and / or a second PSFCH (different from the first PSFCH). In some instances, the RX UE transmits Z SL HARQ feedbacks to the TX UE (e.g., the Z SL HARQ feedbacks can be transmitted via the retransmission 508). In some instances, Z can be 16, and the Z SL HARQ feedbacks can include 16 SL HARQ feedbacks associated with 16 of a plurality of HARQ processes of the TX UE. In some instances, in a context where there is no other transmission from the TX UE with other HPNs other than HPN 1=X, the RX UE can set a NACK for the other HPNs. In some instances, the RX UE can set information for HPN 1=X based on a processing result (e.g., a result of processing 504 the PSCCH / PSSCH 502), which can be an acknowledgement (ACK) (indicating an acknowledgement of reception of the PSCCH / PSSCH 502) or a NACK (indicating a negative acknowledgement of reception of the PSCCH / PSSCH 502). The retransmission 508 can be based on the TX UE’s HPN 1=X (rather than, for example, the RX UE’s HPN 2=Y). For example, the retransmission 508 can indicate that the SL HARQ feedback associated with the PSCCH / PSSCH 502 corresponds to the TX UE’s HPN 1=X.In this way, based on the retransmission 508, the TX UE can correlate the SL HARQ feedback to the PSCCH / PSSCH 502 associated with the HPN 1=X of the TX UE (and / or the TX UE can use the retransmission 508 to determine whether the PSCCH / PSSCH 502 was successfully received by the RX UE).

[0515] The concepts of the present disclosure can be having an exemption for PSFCH in an unlicensed spectrum. A network node can provide a configuration that configures an occupancy duration for PSFCH during an interval to be no greater than a threshold. For example, the configuration can satisfy a condition that an occupancy duration for PSFCH during an interval is no greater than a threshold. In an example, the interval can be 100 ms, and the threshold can be 10 ms. In an example, the configuration can satisfy a condition that an occupancy duration for PSFCH is no more than 10 ms during a 100 ms interval. Other values for the interval and / or threshold are within the scope of the present disclosure. The exemption configuration for PSFCH (e.g., a configuration for a network node to have an exemption) can depend on (i) a configuration of a PSFCH periodicity in a sidelink resource pool (e.g., the PSFCH periodicity can be in units of sidelink slots), and / or (ii) a bitmap indicating sidelink slots in the sidelink resource pool. Based on the bitmap, a number of sidelink slots belonging to the sidelink resource pool during the interval can be determined. Based on the PSFCH periodicity, a number of sidelink slots including PSFCH during the interval can be determined. The exemption configuration associated with the network node and the PSFCH (e.g., a configuration for a network node to have an exemption for PSFCH) can satisfy the following equation Alternatively and / or additionally, the exemption configuration associated with the network node and the PSFCH (e.g., a configuration for a network node to have an exemption for PSFCH) can satisfy the following equation In some examples, P corresponds to a PSFCH periodicity. In some examples, S corresponds to a number of sidelink slots belonging to a sidelink resource pool during an interval (e.g., a 100 ms interval). In some examples, Z can correspond to a number of bits in a bitmap having a value of 1 (e.g., Z bits). In some examples, a size of the bitmap is Y bits. In some examples, S% can be based on Z and Y (and / or one or more other values). In some examples, S% can be equal to In some examples, S% can be less than Z / Y. In some examples, there can be one or more candidate values for S and / or S%. Preferably, S and / or S% can be configured (e.g., preconfigured). In some examples, S and / or S% can be configured to (and / or have) a greater than the minimum candidate value (e.g., when the one or more candidate values include a value greater than S and / or S% can be set to the minimum of the one or more candidate values). In some instances, the value of S is the smallest integer value greater than Z / Y x 100. In some instances, for exempt PSFCH transmissions, a configuration for a sidelink resource pool (e.g., an exempt configuration) will satisfy the above equation.

[0516] In a first instance, a 10-bit bitmap (e.g., a bitmap composed of 10 bits) having 6 bits with a value of 1 (e.g., 6 bits of a 10-bit bitmap are set to 1) can be used to configure and / or determine sidelink slots for a sidelink resource pool. In the first instance, when 100 ms includes 100 slots, and there are 60 sidelink slots for a sidelink resource pool, S can be 60 (e.g., S% can correspond to 60 / 100 = 60%). In some instances, a PSFCH periodicity can be at least one of 1, 2, 4 (because, for example, ). ).

[0517] In a second instance, a PSFCH periodicity can be 1 (i.e., P = 1). In some instances, an exempt configuration associated with a PSFCH (e.g., a configuration for exempted PSFCH) will be based on a number of PSFCH slots during a 100 ms interval (or other size interval). In some instances, a number of bits (i.e., Z) on a number of bits (i.e., Y) of a bitmap having a value of 1 should satisfy the following equation If Z and Y cannot satisfy the equation with a PSFCH periodicity of 1, LBT for PSFCH can be performed when a UE needs to transmit a PSFCH (e.g., a PSFCH transmission cannot be exempted from sensing requirements due to not satisfying the equation).

[0518] In some instances, a number of sidelink slots S (e.g., a number of sidelink slots belonging to a sidelink resource pool during a 100 ms interval) can be less than In an instance, S can correspond to 90 (e.g., 90 slots for sidelink). In some instances, a bitmap used to configure and / or determine sidelink slots for a sidelink resource pool includes 6 bits with a value of 1 on a total of 10 bits (e.g., 6 bits of a 10-bit bitmap are set to 1). In some instances, a 100 ms interval can include one or more DL and / or UL slots (e.g., the one or more DL and / or UL slots can not be used for sidelink transmissions). In an instance, may be replaced by the number of sidelink slots (e.g., sidelink slots for a sidelink resource pool) during a 100 ms interval. In an example where S is equal to 90 (e.g., there are 90 sidelink slots belonging to a sidelink resource pool during a 100 ms interval), the PSFCH periodicity can satisfy the following equation (i.e., based on the equation, ). In some examples, the PSFCH periodicity P can be 1, 2, 4.

[0519] In some examples, in accordance with one or more regulations for unlicensed spectrum, an exemption for transmissions in the unlicensed spectrum applies to at most S% of time of the transmissions during a time interval / duration. In one example, a device is not allowed to occupy more than 10 ms in a 100 ms time interval for exempted transmissions (e.g., transmissions exempted from sensing requirements).

[0520] In some instances, the exempted PSFCH can be configured in one or more sidelink slots. In some instances, the one or more sidelink slots are configured (e.g., preconfigured). In some instances, the one or more sidelink slots are for exempted PSFCH. In some instances, the one or more sidelink slots are periodic (e.g., the one or more sidelink slots for exempted PSFCH occur periodically according to a periodicity). In some instances, the one or more sidelink slots are periodic per cluster (e.g., in each period of L slots with periodicity, there are Q consecutive sidelink slots as Q-LBT-exempt for PSFCH transmission). In some instances, a slot available for sidelink (e.g., in a carrier and / or in a sidelink BWP) can be denoted by a logical slot index i. In some instances, slot i mod W = offset can be configured as the one or more (exempted) sidelink slots (e.g., the one or more sidelink slots can correspond to slot i mod W = offset). In some instances, slot i mod W = offset can be reset periodically (e.g., every 100 ms). In some instances, W and / or offset can be configured (e.g., preconfigured) based on carrier signaling (e.g., carrier-specific signaling) and / or sidelink BWP signaling (e.g., sidelink BWP-specific signaling). For example, W and / or offset can be configured for a carrier and / or a sidelink BWP. In an instance, in a 100 ms interval, every 4th slot available for sidelink is indicated and / or configured as an exempted PSFCH slot. In another instance, if there are 90 slots available for sidelink transmission (i = 0, 1…89) in a 100 ms interval, slots i mod 4 = 1 can be exempted PSFCH slots (e.g., slots i = 1, 5, 9…89 can be exempted PSFCH slots). In some instances, the slots available for sidelink transmission are for PSCCH sidelink transmission, PSSCH sidelink transmission, PSFCH sidelink transmission, and / or SL CSI-RS sidelink transmission. In some instances, the slots available for sidelink transmission do not include slots for sidelink synchronization signal (SL-SS) transmission, PBCH transmission, or physical sidelink broadcast channel (PSBCH) transmission.

[0521] In some instances, the one or more sidelink slots can be based on sidelink slots allowed for a carrier or a sidelink BWP. In some instances, the one or more sidelink slots can be based on a periodicity (e.g., W) and an offset (e.g., offset). In some instances, the one or more sidelink slots can be based on a first bitmap (e.g., a particular bitmap). In some instances, the first bitmap can indicate slots that are available for sidelink and can have a PSFCH with an exemption (e.g., transmissions performed in the slots can be exempt from sensing requirements). In some instances, a first sidelink resource pool having one or more configured and / or enabled PSFCH resources includes a first slot and a second slot. In some instances, if the first slot has a PSFCH resource based on a configuration of the first sidelink resource pool, whether the PSFCH resource in the first slot is exempt from LBT is based on whether the first slot is configured and / or indicated as an exempt slot (e.g., if at least one of a signal, a configuration, etc. indicates that the first slot is an exempt slot and / or configures the first slot as an exempt slot, the one or more PSFCH resources in the first slot can be exempt from LBT). In some instances, if the first slot is configured and / or indicated as an exempt slot (e.g., if at least one of a signal, a configuration, etc. indicates that the first slot is an exempt slot and / or configures the first slot as an exempt slot), the UE can transmit a PSFCH in the first slot without performing LBT. In some instances, if the first slot is not configured and / or indicated as an exempt slot (e.g., if at least one of a signal, a configuration, etc. indicates that the first slot is not an exempt slot and / or configures the first slot as not an exempt slot), the UE can perform LBT for accessing a channel for transmitting a PSFCH in the first slot. In some instances, if the second slot does not have a PSFCH resource based on a configuration of the first sidelink resource pool (e.g., if the configuration of the first sidelink resource pool does not configure a PSFCH resource in the second slot), the UE cannot apply the exemption in the second slot even if the second slot is configured and / or indicated as an exempt slot because there is no PSFCH resource in the second slot.

[0522] From a network node perspective, a network node can configure one or more sidelink slots in an interval for PSFCH exemption (e.g., an interval with one or more slots in which PSFCH transmissions can be performed without performing LBT) such that the one or more sidelink slots satisfy a condition that PSFCH in (each of) the one or more sidelink slots in the interval does not span a duration that exceeds a threshold (e.g., 10 ms). In some instances, each of the one or more sidelink slots is considered to have a PSFCH transmission present (whether or not there is an actual PSFCH location, e.g., based on a pool configuration). In some instances, if there is a PSFCH configured in a sidelink resource pool in a sidelink slot that is also from the one or more sidelink slots, then the PSFCH transmission in that slot can be exempt from LBT.

[0523] In some instances, carrier-specific slots (e.g., slots used in association with a carrier) and / or sidelink BWP-specific slots (e.g., slots used in association with a sidelink BWP) can be exempt from LBT for PSFCH transmissions.

[0524] From a PSFCH transmitter perspective, a UE can determine whether to perform LBT for transmitting a PSFCH based at least on a configuration of a carrier-specific slot or a sidelink BWP-specific slot.

[0525] In some instances, when a network node configures one or more sidelink slots in an interval for PSFCH exemption, the network node will consider (e.g., take into account) Uu slots that include signaling allowed for exemption. In some instances, the network will combine the times to have a more conservative or lower number of one or more sidelink slots in an interval for PSFCH exemption. For example, a network node can determine whether an interval for PSFCH exemption includes Uu slots associated with LBT exemption (e.g., Uu slots can include signaling exempt from LBT) and / or a number of Uu slots in the interval associated with LBT exemption. In an instance, if an interval for PSFCH exemption includes Uu slots, then a number of sidelink slots configured by the network node in the interval can be lower compared to an interval for PSFCH exemption that does not include Uu slots. Alternatively and / or additionally, a higher number of Uu slots in the interval can correspond to a lower number of sidelink slots configured by the network node in the interval.

[0526] In some instances, a pool configuration for a sidelink resource pool can be configured and / or enabled with PSFCH exemption, or PSFCH exemption can be deactivated for a pool configuration and / or a sidelink resource pool (e.g., a pool configuration can configure and / or enable PSFCH exemption for a sidelink resource pool, or can deactivate PSFCH exemption for a sidelink resource pool). In some instances, for a sidelink resource pool configured and / or enabled with PSFCH exemption, a network node and / or a pool configuration can configure one or more pool-specific locations (e.g., pool-specific timing) for PSFCH exemption for the sidelink resource pool. In some instances, for a sidelink resource pool not configured and / or enabled with PSFCH resource (e.g., PSFCH periodicity is 0), a network node and / or a pool configuration can not be allowed to provide and / or configure pool-specific locations for PSFCH exemption for the sidelink resource pool (e.g., parameters for configuring pool-specific locations for PSFCH exemption can not exist in the pool configuration). In some instances, pool-specific locations for PSFCH exemption can not be associated with (e.g., can not be used for) all PSFCHs (e.g., all PSFCH transmissions and / or resources) in a sidelink resource pool. In some instances, pool-specific locations for PSFCH exemption can be associated with (e.g., can be used for) a subset of PSFCHs (e.g., a subset of PSFCH transmissions and / or resources) in a sidelink resource pool. In some instances, pool-specific locations for PSFCH exemption can be associated with (e.g., can be used for) all PSFCHs (e.g., all PSFCH transmissions and / or resources) in a sidelink resource pool. In some instances, pool-specific locations for PSFCH can not apply to another sidelink resource pool (e.g., pool-specific locations for PSFCH configured by a pool configuration can only apply to a sidelink resource pool associated with the pool configuration).

[0527] In some instances, the pool-specific location for PSFCH exemption can be based on a sidelink slot in a sidelink resource pool that includes PSFCH resources. In some instances, a sidelink slot in a sidelink resource pool can be denoted as a logical slot index t. In some instances, for every P sidelink slots in the sidelink resource pool that includes PSFCH resources in the sidelink resource pool, t = 0, P, 2P, 3P, 4P. For example, each set of P sidelink slots in a sidelink resource pool can include PSFCH resources of the sidelink resource pool, where the PSFCH resources can be located in the gth sidelink slot of the set of P sidelink slots. In an instance where g is P (e.g., corresponding to the last sidelink slot of the set of P sidelink slots) and P is 100, the sidelink resource pool can include PSFCH resources located at the 100th sidelink slot in the sidelink resource pool (e.g., 100 = 1 x P), PSFCH resources located at the 200th sidelink slot in the sidelink resource pool (e.g., 200 = 2 x P), PSFCH resources located at the 300th sidelink slot in the sidelink resource pool (e.g., 300 = 3 x P), and so on. In some instances, the pool-specific location for PSFCH exemption can be an integer (or non-integer) multiple of P. In some instances, there can be a pool-specific location for PSFCH exemption every M x P sidelink slots in a sidelink resource pool. For example, each set of M x P sidelink slots in a sidelink resource pool can include a pool-specific location for PSFCH exemption, where the pool-specific location for PSFCH exemption can be located at the vth sidelink slot of the set of P sidelink slots. In an instance where v is M x P (e.g., corresponding to the last sidelink slot of the set of M x P sidelink slots), M is 3, and P is 100, the sidelink resource pool can include a pool-specific location for PSFCH exemption located at the 300th sidelink slot in the sidelink resource pool (e.g., 300 = 1 x M x P), a pool-specific location for PSFCH exemption located at the 600th sidelink slot in the sidelink resource pool (e.g., 600 = 2 x M x P), a pool-specific location for PSFCH exemption located at the 900th sidelink slot in the sidelink resource pool (e.g., 900 = 3 x M x P), and so on. In some instances, there can be a pool-specific location for PSFCH exemption every M PSFCH slots in a sidelink resource pool. For example, each set of M PSFCH slots in a sidelink resource pool can include a pool-specific location for PSFCH exemption, where the pool-specific location for PSFCH exemption can be located at the u th PSFCH slot of the set of P PSFCH slots.In instances where v is M (e.g., corresponding to a last PSFCH slot of a set of M PSFCH slots) and M is 3, a sidelink resource pool can include a pool-specific location for PSFCH exemption at a 3rd PSFCH slot (e.g., 3 = 1 x M) in the sidelink resource pool, a pool-specific location for PSFCH exemption at a 6th PSFCH slot (e.g., 6 = 2 x M) in the sidelink resource pool, a pool-specific location for PSFCH exemption at a 9th PSFCH slot (e.g., 9 = 3 x M) in the sidelink resource pool, and so on. In some instances, for every M x P sidelink slots in a sidelink resource pool, there can be Q x P sidelink slots at which there is a pool-specific location for PSFCH exemption. For example, every set of M x P sidelink slots in a sidelink resource pool can include Q x P sidelink slots that each include a pool-specific location for PSFCH exemption. In some instances, for every M PSFCH slots in a sidelink resource pool, there can be Q PSFCH slots at which there is a pool-specific location for PSFCH exemption (e.g., periodic indication per cluster). For example, every set of M PSFCH slots in a sidelink resource pool can include Q PSFCH slots that each include a pool-specific location for PSFCH exemption. In this disclosure, a PSFCH slot in a sidelink resource pool can correspond to a sidelink slot in the sidelink resource pool that includes (e.g., is configured with) one or more PSFCH resources. In some instances, a pool-specific location for PSFCH exemption can be indicated by a bitmap. In some instances, a bitmap can be applicable to PSFCH slots in a sidelink resource pool. For example, a bitmap of “10010” can indicate that every set of 5 PSFCH slots in a sidelink resource pool includes 2 PSFCH slots associated with PSFCH exemption (e.g., in which PSFCH can be exempted for LBT), where the locations of the 2 PSFCH slots can correspond to a first (e.g., initial and / or starting) slot of the set of 5 PSFCH slots and a fourth slot of the set of 5 PSFCH slots (e.g., 3 PSFCH slots after the first slot).

[0528] In some instances, a SL BWP-specific slot format is applied for the SL BWP and / or a carrier-specific slot format is applied for the carrier. In some instances, the symbol position of PSFCH in each slot available for the SL BWP is the same (e.g., each slot available for the SL BWP can have PSFCH at the same symbol position). In some instances, the symbol position of PSFCH in each slot available for the carrier is the same (e.g., each slot available for the carrier can have PSFCH at the same symbol position). In some instances, for each slot available for the SL BWP or the carrier, the symbol position of PSFCH in the slot can be denoted as symbol indices j and j+1 (e.g., j = 11 within a 14-symbol slot with symbol indices 0~13). In some instances, the SL BWP or the carrier can include one or more sidelink resource pools. In some instances, different sidelink resource pools can have different pool-specific locations for PSFCH exemption. In some instances, a slot can belong to a first sidelink resource pool and a second sidelink resource pool. In some instances, different subchannels and / or physical resource blocks (PRBs) in this slot can belong to different sidelink resource pools. In some instances, based on the pool configuration of each sidelink resource pool, there is PSFCH resource in the slot belonging to the first sidelink resource pool and the second sidelink resource pool. In some instances, based on the pool configuration of the first sidelink resource pool and / or the second sidelink resource pool, a slot in the first sidelink resource pool can be associated with PSFCH exemption (e.g., PSFCH in a slot in the first sidelink resource pool can be exempted from LBT requirement according to the pool configuration of the first sidelink resource pool), while a slot in the second sidelink resource pool can not be associated with PSFCH exemption (e.g., PSFCH in a slot in the second sidelink resource pool can not be exempted from LBT requirement according to the pool configuration of the second sidelink resource pool). Alternatively and / or additionally, in an instance, a UE can determine (e.g., consider and / or derive) that a slot in a pool is associated with PSFCH exemption (e.g., exempted from LBT requirement) due to the configuration of another pool (e.g., a slot in the second sidelink resource pool can be determined to be exempted from LBT requirement according to the pool configuration of the first sidelink resource pool), which can satisfy the regulation in the carrier-specific hierarchy. In other words, in some instances, once a sidelink resource pool in a carrier contains one or more slots (and / or locations and / or occasions) for PSFCH exemption, the PSFCH exemption can be applied to the same one or more slots (and / or locations and / or occasions) in another sidelink resource pool in the carrier. In some instances, the first sidelink resource pool and the second sidelink resource pool are in the same carrier. In some instances, the first sidelink resource pool and the second sidelink resource pool are in the same frequency band. In some instances, the first sidelink resource pool and the second sidelink resource pool are in the same LBT frequency band (e.g., 20 MHz).Based on the first sidelink resource pool and the second sidelink resource pool being in the same carrier, the same frequency band, and / or the same LBT frequency band, a PSFCH exemption associated with a slot in the first sidelink resource pool (e.g., the PSFCH exemption associated with the slot can be indicated by the pool configuration of the first sidelink resource pool) can apply to the same slot in the second sidelink resource pool. In some instances, when the first sidelink resource pool and the second sidelink resource pool are in different carriers, different frequency bands, and / or different LBT frequency bands, the PSFCH exemption from the other pool can be prohibited (e.g., if the first sidelink resource pool and the second sidelink resource pool are in different carriers, different frequency bands, and / or different LBT frequency bands, the first UE can not be allowed to apply the PSFCH exemption associated with the first sidelink resource pool to a slot in the second sidelink resource pool).

[0529] In some instances, the signaling for inter-UE coordination information scheme 2 (and / or a collision indication) can be transmitted in (i) the same symbol location of the PSFCH (e.g., the location of the symbol in a slot for the PSFCH) and / or (ii) different frequency resources. In some instances, the PSFCH occasion for inter-UE coordination information scheme 2 (and / or a collision indication) can be in the same symbol as the PSFCH occasion for sidelink HARQ feedback in the same sidelink resource pool. In some instances, if a slot is configured (and / or indicated) as an exempted PSFCH, the signal and / or PSFCH for inter-UE coordination information scheme 2 (and / or a collision indication) in the same slot (and / or the same symbol) can be exempted from LBT (based on, for example, the slot being configured as an exempted PSFCH). In other words, in some instances, a UE can transmit a signal and / or PSFCH for inter-UE coordination information scheme 2 (and / or a collision indication) in a slot configured (and / or indicated) as an exempted PSFCH without performing LBT.

[0530] In some instances, a location and / or occasion for PSFCH exemption (whether or not the location and / or occasion for PSFCH exemption is, for example, pool-specific, carrier-specific, and / or SL BWP-specific) can correspond to (and / or imply) a slot for PSFCH exemption. In some instances, a location and / or occasion for PSFCH exemption (whether or not the location and / or occasion for PSFCH exemption is, for example, pool-specific, carrier-specific, and / or SL BWP-specific) can correspond to (and / or imply) symbols j and j+1 in a slot for PSFCH exemption. In some instances, a location and / or occasion for PSFCH exemption (whether or not the location and / or occasion for PSFCH exemption is, for example, pool-specific, carrier-specific, and / or SL BWP-specific) does not correspond to (and / or does not imply or allow) symbols in a slot for PSFCH exemption other than j and j+1 (which are, for example, configured for PSFCH). In some instances, a location and / or occasion for PSFCH exemption (whether or not the location and / or occasion for PSFCH exemption is, for example, pool-specific, carrier-specific, and / or SL BWP-specific) does not correspond to (and / or does not imply or allow) (i) channels other than PSFCH, and / or (ii) channels that do not overlap with PSFCH (e.g., a signaling signal for inter-UE coordination information scheme 2 signaling and / or PSFCH) in symbols j and j+1 in a slot for exemption. For a slot that is available for sidelink and associated with PSFCH exemption, if there is a PSFCH resource in the slot, the UE can transmit PSFCH in the slot without performing LBT. For a slot that is available for sidelink and associated with PSFCH exemption, if there is one or more PSCCH, PSSCH, CSI-RS, and / or SS-PBCH resource in the slot, the UE can perform LBT for access to a channel for transmission on the one or more resources.

[0531] In some instances, based on the PSFCH exemption discussed in the foregoing description, a UE that can transmit PSFCH (and / or inter-UE coordination information scheme 2 and / or a collision indication) can transmit PSFCH (e.g., in a slot associated with PSFCH exemption) without performing LBT.

[0532] In some instances, based on the PSFCH exemptions discussed in the foregoing description, a UE that can transmit PSFCH (and / or UE-to-UE coordination information scheme 2 and / or a collision indication) can not be configured (and / or allowed) to transmit (and / or can not transmit) PSCCH / PSSCH / SL SS / PBCH / CSI-RS in the same slot associated with the PSFCH exemption without performing LBT. In some instances, the UE should perform LBT for transmitting PSCCH / PSSCH / SL SS / PBCH / CSI-RS. In this disclosure, the term “PSCCH / PSSCH / SL SS / PBCH / CSI-RS” can refer to PSCCH, PSSCH, SL SS, PBCH, and / or CSI-RS.

[0533] Alternatively and / or additionally, if a PSFCH exemption (e.g., discussed in the foregoing description) applies to a slot associated with transmitting SL SS, PBCH, and / or PSBCH, the UE can transmit SL SS, PBCH, and / or PSBCH (e.g., in the slot associated with the PSFCH exemption) without performing LBT. In some instances, the transmission of SL SS, PBCH, and / or PSBCH can include more than 2 symbols in a slot. In some instances, when determining whether to transmit SL SS, PBCH, and / or PSBCH without performing LBT (e.g., in a slot associated with a PSFCH exemption), a requirement that a duration (e.g., an occupancy duration) for transmitting one or more exempted signals and / or channels in an interval be at most a threshold value can be considered.

[0534] The concepts of the present disclosure can be that there is a periodicity (e.g., FFP) for PSFCH. The periodicity for PSFCH can include one or more PSFCHs (e.g., one or more PSFCH occasions / resources), such one or more periodic PSFCHs. The periodicity for PSFCH can include an idle duration, which can be located at the end of the periodicity for PSFCH. The idle duration at the end of the current periodicity for PSFCH can be used for sensing. When the idle duration located at the end of the current periodicity for PSFCH is sensed as idle (e.g., in response to determining that the sensing result indicating the idle duration is idle), the UE (performing sensing during the idle duration) can be allowed to perform (and / or can perform) a PSFCH transmission in the next (consecutive) periodicity for PSFCH. When the idle duration located at the end of the current periodicity for PSFCH is sensed as busy (e.g., in response to determining that the sensing result indicating the idle duration is busy), the UE can not be allowed to perform (and / or can not perform) a PSFCH transmission in the next (consecutive) periodicity for PSFCH. When a first UE receives a sidelink transmission from a second UE, where the sidelink transmission indicates enabled sidelink HARQ feedback, the first UE can determine (e.g., derive) a slot for transmitting sidelink feedback (e.g., SL HARQ on PSFCH, or SL HARQ on PSSCH) based on an association between the slot carrying the sidelink transmission and the slot for transmitting (and / or carrying) the sidelink feedback. The sidelink feedback is in response to the sidelink transmission from the second UE. The first UE can perform sensing on an idle duration of a first periodicity (e.g., a first FFP) for the sidelink feedback, where the first periodicity (and / or the idle duration of the first periodicity) is before a second periodicity (e.g., a second FFP) that includes the derived timing for transmitting the sidelink feedback (e.g., the derived timing can correspond to the slot that the first UE determines for transmitting the sidelink feedback). Based on a sensing result of the sensing performed on the idle duration of the first periodicity (and / or based on other information than the sensing result, for example), the first UE can determine whether to transmit a PSFCH via the derived timing in the second periodicity.

[0535] The first UE can be informed about a Channel Occupancy Time (COT) starter for sidelink feedback and / or PSFCH.

[0536] When the first UE is provided (e.g., by the second UE) information indicating that the COT initiator for the sidelink feedback corresponds to (e.g., is based on) a different UE than the first UE (e.g., the different UE can be the second UE), the first UE can determine (e.g., verify and / or validate) whether there is a second sidelink transmission from the second UE in a slot determined (e.g., derived) by the first UE for transmitting the sidelink feedback (e.g., the first UE determines to transmit the sidelink feedback in the slot). In some instances, the second sidelink transmission is transmitted by the second UE (and / or by one or more other UEs in addition to the second UE). In some instances, one or more destination UEs of the second sidelink transmission include the first UE (and / or one or more other UEs in addition to the first UE). In some instances, the second sidelink transmission can be unicast, groupcast, or broadcast.

[0537] When the first UE is provided (e.g., by the second UE) information indicating that the COT initiator for the sidelink feedback corresponds to (e.g., based on) the first UE, the first UE can determine (e.g., verify and / or validate) whether there is a COT initiated by the first UE that encompasses the timing for transmitting the sidelink feedback. If the first UE has initiated a COT that covers (e.g., overlaps with, such as fully overlaps with) the timing for transmitting the sidelink feedback, the first UE can perform (e.g., further perform) short sensing (e.g., sensing in a duration that is less than a threshold duration) if a gap between the timing for transmitting the sidelink feedback and the timing of a sidelink burst from the first UE is greater than a threshold. In some instances, the sidelink burst corresponds to one or more sidelink transmissions from the first UE, where a gap in the time domain between each pair of (consecutive) sidelink transmissions of the one or more sidelink transmissions is at most a threshold (e.g., there can be at most a 16 microsecond gap between any two consecutive sidelink transmissions in the sidelink burst). If the first UE has not initiated a COT that covers (e.g., overlaps with, such as fully overlaps with) the timing for transmitting the sidelink feedback, the first UE can perform (e.g., further perform) short sensing during an idle duration of a previous period (e.g., a previous FFP) for PSFCH (e.g., the previous period can be before the timing for transmitting the sidelink feedback). Once the first UE determines (e.g., detects and / or checks) that the channel is idle during the idle duration of the previous period for PSFCH (e.g., in response to the determination that the channel is idle), the first UE can transmit the sidelink feedback. In some instances, if the first UE has initiated a COT in a period (e.g., a period for PSSCH, such as a FFP), but the timing of the sidelink feedback is within an idle duration of the period, the first UE can not be allowed to transmit (and / or the first UE can not transmit) the sidelink feedback. In some instances, the first UE not transmitting the sidelink feedback can correspond to the first UE dropping (the transmission of) the sidelink feedback. However, in some instances, the first UE is provided information indicating that the COT initiator is different from the first UE, the first UE can perform sensing and the first UE can transmit the sidelink feedback (e.g., if the sensing result is idle) even if the timing of the sidelink feedback overlaps with an idle duration of the first UE of a period (e.g., a period for PSSCH, such as a FFP) of the first UE.

[0538] A length (e.g., a duration) of a periodicity for PSFCH (e.g., a FFP) can be based on a periodicity of PSFCH (e.g., a periodicity of PSFCH for sidelink HARQ feedback) and / or based on other information in addition to the periodicity of PSFCH. The length of the periodicity for PSFCH can be an integer and / or can correspond to the periodicity of PSFCH (e.g., the length can correspond to an integer number of the periodicity of PSFCH). A symbol offset applied for the periodicity for PSFCH can be based on a symbol location of PSFCH (e.g., a symbol location of PSFCH in a slot) and / or based on other information in addition to the symbol location. A start of the periodicity for PSFCH (e.g., a start time of the periodicity, a start slot of the periodicity, a start symbol of the periodicity) can be based on the symbol offset (and / or based on other information in addition to the symbol offset). The symbol offset can not be configured by a gNB. The symbol offset can be determined (e.g., implicitly determined and / or derived) by a UE based on the symbol location of PSFCH (e.g., a symbol location of PSFCH in a slot). In some instances, the slot is the earliest slot (in a sidelink resource pool) relative to an even-indexed subframe (and / or slot) with a system frame number (SFN) = 0 and / or a direct frame number (DFN) = 0. The UE can determine (e.g., derive) the start of the periodicity for PSFCH based on the symbol offset (and / or based on other information in addition to the symbol offset). For example, the symbol offset can be implicitly determined (e.g., implicitly derived) by the UE based on the symbol location of PSFCH in a slot. In some instances, the slot is the earliest slot (in a sidelink resource pool) relative to an even-indexed subframe (and / or slot) with a SFN and / or a DFN. The UE can determine (e.g., derive) the start of the periodicity for PSFCH based on the symbol offset (and / or based on other information in addition to the symbol offset).

[0539] In some instances, a length of the periodicity for PSFCH can be 1 ms (e.g., the length of the periodicity can always be 1 ms, such as where the periodicity for PSFCH each have a fixed length of 1 ms).

[0540] In some instances, a length of the periodicity for PSFCH can be 1 slot (e.g., the length of the periodicity can always be 1 slot, such as where the periodicity for PSFCH each have a fixed length of 1 slot).

[0541] In some instances, a subcarrier spacing (SCS) for the 1 slot can be based on a SCS of a SL carrier, a SL BWP, and / or a SL resource pool.

[0542] In some instances, a SCS for the 1 slot can be based on a minimum SCS associated with one or more serving SL carriers.

[0543] In some instances, the SCS for the 1 slot can be based on a minimum SCS associated with one or more unlicensed serving SL carriers.

[0544] Figure 6 A diagram showing a periodicity for PSFCH (e.g., PSFCH FFP) is shown. Figure 6 A rectangle filled with diagonal lines shows PSFCH (e.g., PSFCH resources), a rectangle filled with dots shows an idle duration of the periodicity (e.g., FFP), and a rectangle and / or square filled with black shows channel occupancy. In Figure 6 In the shown instance, the symbol offset can correspond to a PSFCH location in a slot (e.g., a timing of PSFCH in a slot). For example, based on a PSFCH starting from symbol 11 of a slot, the symbol offset can be 11. A length of the periodicity for PSFCH (e.g., a length of PSFCH FFP) can be based on (e.g., can be equal to) a periodicity of PSFCH, which in Figure 6 is 2 slots. In Figure 6 In the shown instance, if a RX UE needs to transmit a PSFCH in a slot “Slot 3” in response to a sidelink transmission, the RX UE can perform sensing (e.g., during an idle duration “ID1”) before a FFP “PSFCH FFP 2” (e.g., a FFP for PSFCH) in Slot 3. If a sensing result of the sensing performed by the RX UE is idle, the RX UE can transmit the PSFCH in Slot 3 (e.g., the PSFCH can be transmitted in a PSFCH resource “PSFCH 2” in Slot 3). In some instances, a maximum channel occupancy can correspond to a channel occupancy that occupies 95% (or other amount) of a length of a PSFCH FFP (e.g., Figure 6 shown as a black rectangle “CO1” in Figure 6 In some instances, an end (e.g., an end time position) of a channel occupancy (e.g., for PSFCH) can be limited to an end slot boundary. Alternatively and / or additionally, an end (e.g., an end time position) of a channel occupancy (e.g., for PSFCH) can be limited to an end symbol (e.g., a last symbol, such as a second symbol) of a PSFCH (e.g., in a slot). In some instances, a start (e.g., a start time position) of a channel occupancy (e.g., for PSFCH) can be limited to an initial symbol (e.g., a start symbol before a second symbol) of a PSFCH (e.g., in a slot).

[0545] In some instances, a length of a periodicity (e.g., FFP) for PSFCH can be 1 ms, 2 ms, 2.5 ms, 4 ms, 5 ms, or 10 ms.

[0546] In some instances, a periodicity (e.g., FFP) for PSFCH is fixed and / or specified.

[0547] In some instances, a periodicity (e.g., FFP) for PSFCH can correspond to (e.g., can be based on) a PSFCH to end slot boundary of a slot or a timing to a last symbol (e.g., gap symbol) for sidelink.

[0548] In some instances, a periodicity (e.g., FFP) for PSFCH is configured by a gNB and / or based on a pre-configuration.

[0549] In some instances, a configuration of a periodicity (e.g., FFP) for PSFCH can be associated with a sidelink resource pool configuration.

[0550] In some instances, a configuration of a periodicity (e.g., FFP) for PSFCH can be associated with a SL BWP and / or SL carrier configuration.

[0551] In some instances, a configuration of a periodicity (e.g., FFP) for PSFCH can be common for UEs in a sidelink resource pool (e.g., UEs in a sidelink resource pool can share a same periodicity).

[0552] In some instances, a configuration of a periodicity (e.g., FFP) for PSFCH can be common for UEs in a SL BWP and / or SL carrier (e.g., UEs in a SL BWP and / or SL carrier can share a same periodicity).

[0553] A first UE can have multiple (e.g., two) types of UE FFPs. The multiple types of UE FFPs include a first type of UE FFP and a second type of UE FFP. The first type of UE FFP (e.g., a periodicity for PSFCH) is associated with PSFCH. The second type of UE FFP (e.g., a periodicity for PSSCH) is associated with PSSCH.

[0554] The first UE can have a sidelink communication with the second UE. The sidelink communication can be a unicast sidelink transmission, a groupcast sidelink transmission (including, for example, the second UE within a group of destination UEs), or a broadcast sidelink transmission. The first UE can receive and / or detect a sidelink transmission (e.g., PSCCH and / or PSSCH) from the second UE. The sidelink transmission (e.g., SCI in PSCCH) can indicate (e.g., indicate and / or require) the first UE to transmit sidelink feedback (e.g., sidelink HARQ feedback) in response to the sidelink transmission. The sidelink transmission can further indicate information associated with (e.g., indicate) whether the first UE initiates a COT for transmitting a PSFCH (and / or whether the first UE is a COT initiator for transmitting a PSFCH). The first UE can determine a timing (e.g., a slot) of the PSFCH based on a PSFCH configuration (e.g., a periodicity of the PSFCH) and / or based on an association between a PSSCH and a PSFCH (e.g., the association can correspond to a time gap for processing and / or a HARQ round trip time (RTT) between a PSSCH and a corresponding PSFCH).

[0555] In example scenarios, a first UE can be instructed (e.g., instructed) to initiate a COT for transmitting a PSFCH. In some examples, e.g., in example scenarios where a first UE is instructed (e.g., instructed) to initiate a COT for transmitting a PSFCH, if the first UE has initiated a COT (e.g., in a FFP associated with a second type of UE FFP), the first UE can perform a CAT2-LBT after sensing the channel is idle (e.g., after sensing the channel is idle via a CAT2-LBT performed by the first UE) for performing a PSFCH transmission. In some examples, e.g., in example scenarios where a first UE is instructed (e.g., instructed) to initiate a COT for transmitting a PSFCH, if the first UE has initiated a COT (e.g., in a FFP associated with a first type of UE FFP), the first UE can perform a CAT2-LBT after sensing the channel is idle (e.g., after sensing the channel is idle via a CAT2-LBT) for performing a PSFCH transmission. In some examples, if the channel is sensed as busy (e.g., by performing a CAT2-LBT), the first UE (i) can not transmit a PSFCH in response to a sidelink transmission, (ii) can drop the PSFCH and / or (iii) can store sidelink feedback. In some examples, the first UE can not transmit a PSFCH in response to a sidelink transmission, where the first UE can receive a retransmission of a TB and / or MAC PDU transmitted in the sidelink transmission. In some examples, if there is a second PSFCH in response to the retransmission of the TB and / or MAC PDU, the first UE can transmit the stored sidelink feedback via the second PSFCH. In some examples, the first UE can consider (e.g., further consider) whether a (previously) initiated COT contains a determination timing of the (second) PSFCH. In some examples, when the timing of the (second) PSFCH transmission is within the (previously) initiated COT of the first UE, the first UE can not initiate an (additional) COT for transmitting the (second) PSFCH. In some examples, if the determined timing of the (second) PSFCH is greater than a threshold (e.g., 16us) from a previous sidelink transmission from the first UE, the first UE can transmit the (second) PSFCH in response to (e.g., after) sensing the channel is idle. In some examples, in example scenarios where a first UE is instructed (e.g., instructed) to initiate a COT for transmitting a PSFCH, the first UE will determine (e.g., consider and / or derive) that the determined (second) PSFCH is performed using a COT initiated by the (previously) initiated COT (e.g., initiated by the first UE). In some examples, the previously initiated COT is based on a first type of UE FFP or based on a second type of UE FFP.When the timing of the (second) PSFCH is not within the (previously) initiated COT of the first UE, the first UE can initiate an (additional) COT for transmitting the (second) PSFCH. Since the timing of the one or more PSFCHs is from the start of one or more of the first type of UE FFPs, the first UE can transmit the PSFCH once the first UE senses the channel to be idle (e.g., during the idle duration of the previous consecutive FFP).

[0556] In example scenarios, the first UE can be instructed (e.g., instructed) to use a shared COT from the second UE (e.g., a COT shared by the second UE). In some examples, such as in example scenarios where the first UE is instructed (e.g., instructed) to use a shared COT, the first UE can not initiate a COT associated with a first or second type of UE FFP. The first UE can determine (e.g., verify and / or confirm) whether a COT from the second UE is present in the slot containing the determined PSFCH (e.g., the PSFCH can be determined in response to a sidelink transmission and / or can be determined for transmitting sidelink HARQ feedback in response to a sidelink transmission). In some examples, if the first UE is unable to determine (e.g., verify and / or confirm) that a COT from the second UE is present (e.g., the UE is unable to identify a COT from the second UE in the slot containing the determined PSFCH), the first UE does not transmit a PSFCH in response to the sidelink transmission and / or the first UE can discard the PSFCH. In some examples, the determination (e.g., verification and / or confirmation) of whether a COT from the second UE is present can be based on a determination of whether a sidelink transmission (e.g., a particular sidelink transmission, such as an SCI, PSCCH, PSSCH, and / or PSFCH) from the second UE is present. For example, if the first UE determines to transmit a PSFCH in slot n in response to a sidelink transmission, the first UE can determine (e.g., verify and / or confirm) whether a PSSCH or SCI from the second UE is present in slot n. If the first UE has detected a particular sidelink transmission (e.g., an SCI or PSSCH) from the second UE (e.g., in slot n), the first UE can determine (e.g., verify and / or confirm) that a COT initiated by the second UE is present. In some examples, the first UE can transmit the PSFCH in response to (e.g., after) the first UE senses the channel to be idle.

[0557] In some instances, the second UE can transmit the SCI to the first UE. In some instances, the time resource assignment in the SCI (e.g., indicated by a time resource assignment field in the SCI) and / or the frequency resource assignment in the SCI (e.g., indicated by a time resource assignment field in the SCI) can indicate at most 3 sidelink resources in different slots for one TB. In some instances, the reservation period field in the SCI can indicate one or more future resources based on the indicated reservation period (e.g., indicated by the reservation period field). In some instances, the first UE can receive the SCI in slot n. In some instances, according to the SCI, the first UE can need to perform a sidelink transmission in slot m indicated (and / or derived using) by the SCI. In some instances, when the first UE performs a PSFCH in slot m on one or more symbols different from one or more reserved sidelink resources in slot m from the second UE (e.g., one or more sidelink resources in slot m reserved by the second UE), the first UE can transmit the PSFCH in slot m in response to the first UE detecting and / or receiving the reserved sidelink resources from the second UE in slot m. In some instances, the first UE determines (e.g., verifies and / or validates) whether there is a COT initiated by the second UE in slot m based on whether the first UE detects and / or receives a sidelink transmission (e.g., SCI, PSCCH, PSSCH, and / or PSFCH) from the second UE. In some instances, the information provided by the SCI in slot n does not guarantee the existence of a COT initiated by the second UE covering slot m. In some instances, the validation for a COT initiated by the second UE in slot m is based at least on whether there is a sidelink transmission (e.g., a particular sidelink transmission) from the second UE (e.g., the UE can not determine whether there is a COT initiated by the second UE in slot m based on the SCI received in slot n). In some instances, the destination of the sidelink transmission (e.g., the particular sidelink transmission) from the second UE includes the first UE (and / or one or more other UEs in addition to the first UE). In some instances, the sidelink transmission (e.g., the particular sidelink transmission) from the second UE for determining (e.g., verifying and / or validating) the COT from the second UE can be unicast, groupcast, or broadcast. In some instances, the destination of the sidelink transmission (e.g., the particular sidelink transmission) from the second UE can not include the first UE.

[0558] In some instances, the first UE will check whether there is a COT in slot m from the second UE based on a maximum duration of a COT in the FFP covering slot m. In some instances, the COT covering slot m and / or the COT in slot m can correspond to (and / or be replaced by) a COT covering one or more symbols in slot m according to one or more of the techniques provided herein. In some instances, the first UE can check for a shared COT from the second UE (e.g., for transmitting one or more symbols) based on the one or more symbols in slot m for sidelink (e.g., the one or more symbols can correspond to one or more earlier and / or initial symbols in slot m for sidelink or one or more last symbols in slot m for sidelink). For example, the first UE can only determine (e.g., verify and / or confirm) that there is a COT from the second UE covering (e.g., overlapping, such as fully overlapping) the one or more symbols. In some instances, if the first UE cannot determine (e.g., cannot verify and / or confirm) that there is a COT from the second UE covering (e.g., overlapping, such as fully overlapping) the one or more symbols, the first UE does not transmit a PSFCH in response to a sidelink transmission received from the second UE and / or the first UE can drop the PSFCH.

[0559] In some instances, from the perspective of the first UE, once the first UE knows which initiator’s COT (e.g., a COT initiated by the first UE or a COT initiated by the second UE) will be used for a sidelink transmission (transmitted by the first UE), the first UE can know whether performing a sidelink transmission during the idle duration of the FFP for the COT of the initiator is allowed. For example, if the first UE transmits a PSFCH on a COT initiated by the second UE, the first UE can not be allowed to transmit (and / or not transmit) a sidelink transmission (e.g., any sidelink transmission) during the idle duration of the FFP for the COT associated with the second UE. In some instances, if the first UE transmits a PSFCH on a COT initiated by the second UE, the first UE can transmit a sidelink transmission during the idle duration of the FFP for the COT associated with the first UE. For example, if the first UE transmits a PSFCH on a COT initiated by the first UE, the first UE can not be allowed to transmit (and / or not transmit) a sidelink transmission (e.g., any sidelink transmission) during the idle duration of the FFP for the COT associated with the first UE. In some instances, if the first UE transmits a PSFCH on a COT initiated by the first UE, the first UE can transmit a sidelink transmission during the idle duration of the FFP for the COT associated with the second UE.

[0560] In some instances, the first UE can determine (e.g., verify and / or confirm) whether there is a COT initiated by the second UE based on a time gap between slot n and slot m (and / or based on other information in addition to the time gap). In some instances, when the time gap between slot n and slot m is greater than a time gap threshold (e.g., a length of an FFP), the first UE can not be able to confirm a COT initiated by the second UE for slot m based on the SCI detected in slot n. In some instances, when the time gap between slot n and slot m is less than or equal to the time gap threshold, the first UE can confirm a COT initiated by the second UE for slot m based on the SCI detected in slot n. In some instances, for the time gap between slot n and slot m being less than or equal to the time gap threshold, detecting the SCI in slot n can help the first UE determine (e.g., verify and / or confirm) that there is a COT initiated by the second UE in slot m. In some instances, sensing of a channel in the COT initiated by the second UE can be based on CAT 2 LBT.

[0561] In some instances, the first UE can determine (e.g., verify and / or confirm) whether there is a COT initiated by the second UE based on whether slot n and slot m are in a same FFP or in different FFPs (and / or based on other information in addition to whether slot n and slot m are in a same FFP or in different FFPs). In some instances, when slot n and slot m are in a same FFP (e.g., of the second UE), in response to (e.g., at the time of) the first UE receiving and / or detecting the SCI in slot n, the first UE can determine (e.g., verify and / or confirm) that there is a COT initiated by the second UE that covers slot m (e.g., overlaps with, e.g., fully overlaps with). In some instances, when slot n and slot m are in different FFPs (e.g., of the second UE), in response to (e.g., at the time of) the first UE receiving and / or detecting the SCI in slot n, the first UE can not determine (e.g., can not verify and / or confirm) that there is a COT initiated by the second UE that covers slot m (e.g., overlaps with, e.g., fully overlaps with) based on the SCI detected in slot n. In some instances, the SCI can further indicate whether there is a COT initiated by the second UE. In some instances, the SCI can indicate information of a COT initiator for one or more resources associated with a time resource assignment, a frequency resource assignment, and / or a reservation period field.

[0562] In some instances, a symbol level offset of a FFP for a sidelink UE can be based on a starting symbol for a sidelink in a slot belonging to a sidelink resource pool. In some instances, the starting symbol for a sidelink in a slot can be configured (e.g., preconfigured) via a parameter sl-StartSymbol-r16. In some instances, StartSymbol-r16 can be provided and / or (e.g., preconfigured) as sym0, sym1, sym2, sym3, sym4, sym5, sym6, or sym7.

[0563] The concept of the present disclosure can be that there is an association between a FFP and a sidelink slot in a sidelink resource pool. Since a configuration (e.g., a preconfiguration) can provide a bitmap for indicating sidelink slots in a sidelink resource pool, the sidelink slots in a sidelink resource pool can be physically non-contiguous (and / or can be physically discontinuous) in the time domain.

[0564] In a first embodiment, a length of a FFP is based on a number of slots in a plurality of consecutive slots (e.g., a plurality of consecutive physical slots). In some instances, the length of the FFP can be a minimum or a maximum of (i) a FFP length (e.g., a fixed FFP length, a specified FFP length, and / or a configured (e.g., preconfigured) FFP length), and (ii) a length (e.g., a duration) of the plurality of consecutive (physical) slots. In some instances, the length of the FFP can be a minimum or a maximum of (i) a defined number of slots (e.g., a fixed number of slots, a specified number of slots, and / or a configured (e.g., preconfigured) number of slots), and (ii) a number of slots in the plurality of consecutive (physical) slots. In some instances, the plurality of consecutive (physical) slots is associated with (e.g., belongs to) a sidelink resource pool (e.g., the plurality of consecutive slots can correspond to sidelink slots of a sidelink resource pool). In some instances, according to a bitmap (e.g., provided by a configuration), one cluster can correspond to a number of consecutive 1s in the bitmap, and each cluster can include a same or different number of consecutive 1s. Figure 7 Figures showing configurations of FFPs and / or slots are shown. For example, in Emb1 in Figure 7 In Emb1 in FIG. 6 (e.g., corresponding to the first embodiment), there is a 20-bit bitmap as {11100111100111111000}. The bitmap can indicate (and / or can be used to determine, e.g., derive) which physical slots are associated with (e.g., belong to) a sidelink resource pool (e.g., the bitmap can indicate which physical slots are sidelink slots of a sidelink resource pool). In Emb1 in FIG. 6, the bitmap can indicate that the first 4 slots (e.g., slots 0-3) are associated with (e.g., belong to) a sidelink resource pool (e.g., the bitmap can indicate that the first 4 slots are sidelink slots of a sidelink resource pool). In Emb1 in FIG. 6, the bitmap can indicate that the next 4 slots (e.g., slots 4-7) are associated with (e.g., belong to) a sidelink resource pool (e.g., the bitmap can indicate that the next 4 slots are sidelink slots of a sidelink resource pool). In Emb1 in FIG. 6, the bitmap can indicate that the next 4 slots (e.g., slots 8-11) are associated with (e.g., belong to) a sidelink resource pool (e.g., the bitmap can indicate that the next 4 slots are sidelink slots of a sidelink resource pool). In Emb1 in FIG. 6, the bitmap can indicate that the next 4 slots (e.g., slots 12-15) are associated with (e.g., belong to) a sidelink resource pool (e.g., the bitmap can indicate that the next 4 slots are sidelink slots of a sidelink resource pool). In Emb1 in FIG. 6, the bitmap can indicate that the next 4 slots (e.g., slots 16-19) are associated with (e.g., belong to) a sidelink resource pool (e.g., the bitmap can indicate that the next 4 slots are sidelink slots of a sidelink resource pool). In Emb1 in FIG. 6, the bitmap can indicate that the last 4 slots (e.g., slots 20-23) are associated with (e.g., belong to) a sidelink resource pool (e.g., the bitmap can indicate that the last 4 slots are sidelink slots of a sidelink resource pool). Figure 7In the example shown in FIG. 13, the physical slots corresponding to the sidelink slots of the sidelink resource pool are indicated with “S”. Thus, according to the bitmap of {11100111100111111000}, the physical slots can contain a cluster of three sidelink slots belonging to the sidelink resource pool (labeled with “S”), followed by two slots that are not sidelink slots belonging to the sidelink resource pool, followed by a cluster of four sidelink slots belonging to the sidelink resource pool, followed by two slots that are not sidelink slots belonging to the sidelink resource pool, followed by a cluster of six sidelink slots belonging to the sidelink resource pool, followed by three slots that are not sidelink slots belonging to the sidelink resource pool. In some examples, the PSFCH resources in the sidelink resource pool can occur every 2 sidelink slots of the sidelink resource pool (e.g., there can be a PSFCH resource in every set of 2 sidelink slots of the sidelink resource pool). The first UE FFP can include 3 (physical) slots. The second UE FFP can include 4 (physical) slots. The third UE FFP can include 6 (physical) slots. Alternatively and / or additionally, Figure 7 The last 6 (physical) slots in FIG. 13 can be split into two UE FFPs including 4 (physical) slots and 2 (physical) slots because of a defined maximum length of the FFP (e.g., a fixed maximum length of the FFP, a specified maximum length of the FFP, and / or a configured (e.g., preconfigured) maximum length of the FFP), which can correspond to 4 slots. The first UE can transmit a PSFCH using the 4th sidelink slot in the sidelink resource pool (e.g., Figure 7 “PSFCH 1”) in FIG. 13. The first UE can perform LBT before the second UE FFP. The first UE can determine (e.g., verify and / or confirm) whether there is a COT initiated by the second UE at least in the 4th sidelink slot in this sidelink resource pool. If the first UE cannot determine (e.g., cannot verify and / or confirm) that there is a COT initiated by the second UE (e.g., if the first UE cannot identify a COT initiated by the second UE in the 4th sidelink slot in the sidelink resource pool), the first UE can drop the PSFCH in the 4th sidelink slot in the sidelink resource pool and / or can not transmit the PSFCH. In some examples, the PSFCH in the 4th sidelink slot in this sidelink resource pool can be in response to a sidelink transmission from the second UE, e.g., a PSSCH transmission from the second UE in the 2nd sidelink slot. In some examples, the second UE can be configured (e.g., preconfigured) as a UE-type RSU. Alternatively and / or additionally, the second UE is any UE performing a sidelink transmission in this sidelink resource pool. Alternatively and / or additionally, the second UE and the first UE can belong to a group for groupcast sidelink transmission. Alternatively and / or additionally, the first UE can have a PC5-RRC connection to the second UE.

[0565] In a second embodiment, the length of the FFP can be based on a number of slots in a plurality of consecutive slots (e.g., a plurality of consecutive physical slots). In some instances, the length of the FFP can be further based on a periodicity of PSFCH for the sidelink resource pool. In some instances, the start of the FFP can be based on an initial symbol for SL (e.g., a starting symbol for SL) in a slot, or an initial symbol for PSFCH (e.g., a starting symbol for PSFCH). In some instances, the end of the FFP can be based on a last symbol for SL in a slot, or a symbol before the initial symbol for PSFCH (e.g., the starting symbol for PSFCH), or a last symbol for SL in a last slot in a slot cluster belonging to the sidelink resource pool. In some instances, the initial symbol for SL (e.g., the starting symbol for SL) in a slot can be based on sl-StartSymbol-r16. In some instances, the initial symbol for SL (e.g., the starting symbol for SL) in a slot can be based on a configuration different from sl-StartSymbol-r16. In some instances, the initial symbol for SL (e.g., the starting symbol for SL) in a slot can always be symbol index 0 (e.g., an initial symbol, e.g., a starting symbol, in a slot). In some instances, the last symbol for SL in a slot can be determined (e.g., derived) based on sl-StartSymbol-r16 and sl-LengthSymbols-r16. For example, for sl-StartSymbol-r16 of “sym0” and sl-LengthSymbols-r16 of “sym14”, the last symbol for SL in a slot is symbol index 13. In some instances, sl-StartSymbol-r16 can be “sym0”, “sym1”, “sym2”, “sym3”, “sym4”, “sym5”, “sym6”, and / or “sym7”. In some instances, sl-LengthSymbols-r16 can be “sym7”, “sym8”, “sym9”, “sym10”, “sym11”, “sym12”, “sym13”, and / or “sym14”. For example, in Emb2 in Table 1 (e.g., corresponding to the second embodiment), the initial symbol for SL in a slot is symbol index 0, and the last symbol for SL in a slot is symbol index 13. Figure 7 In Emb2 in Table 1 (e.g., corresponding to the second embodiment), there are four (types of) FFPs with different lengths, denoted as (1), (2), (3), (4). FFP (1) is from symbol index 0 in a sidelink slot with no PSFCH to (and including) a gap symbol before PSFCH in another sidelink slot. FFP (2) is from an initial symbol of PSFCH to (and including) a gap symbol within a sidelink slot. Figure 7A gap (e.g., each with one or more gap symbols) is shown with dots filling a rectangle, and the PSFCH is shown with diagonal lines filling a rectangle. FFP(3) is from symbol index 0 in a sidelink slot with no PSFCH, and e.g., including, a gap symbol in the sidelink slot or another sidelink slot (e.g., the gap symbol can correspond to an ending symbol of the sidelink slot or another sidelink slot belonging to a first cluster of (consecutive physical) slots belonging to a sidelink resource pool). FFP(4) is from symbol index 0 in a sidelink slot with PSFCH (e.g., Figure 7 shown as “PSFCH 1”) to, and e.g., including, a gap symbol before the PSFCH within the sidelink slot. For FFP(4), symbol index 0 is in a sidelink slot with PSFCH (e.g., Figure 7 shown as “PSFCH 1”) to, and e.g., including, a gap symbol before the PSFCH within the sidelink slot. For FFP(4), symbol index 0 is in a sidelink slot with PSFCH (e.g.,

[0566] In a third embodiment, there can be an FFP with a length for a sidelink slot with no PSFCH and / or two FFPs (e.g., with two different lengths) for a sidelink slot with PSFCH. In some instances, the FFP for a sidelink slot with no PSFCH can be based on a number of symbols for SL in the sidelink slot. In some instances, a first FFP for a sidelink slot with PSFCH is based on an initial symbol for SL (e.g., a starting symbol for SL) in the sidelink slot and a gap symbol before the PSFCH. In some instances, the first FFP for a sidelink slot with PSFCH is from the initial symbol for SL (e.g., the starting symbol for SL) in the sidelink slot to, and e.g., including, the gap symbol before the PSFCH. In some instances, a second FFP for a sidelink slot with PSFCH is based on an initial symbol for PSFCH (e.g., a starting symbol for PSFCH) and a last symbol for SL in the sidelink slot. In some instances, the second FFP for a sidelink slot with PSFCH is from the initial symbol for PSFCH (e.g., the starting symbol for PSFCH) to a last symbol for SL within the sidelink slot or a last gap symbol within the sidelink slot. For example, in a sidelink slot with PSFCH (e.g., shown as “PSFCH 1”) in a sidelink slot with PSFCH (e.g., Figure 7In Emb3 (e.g., corresponding to the third embodiment) in FIG. 8, there are three (types of) FFPs with different lengths, denoted as (1'), (2'), (3'). For a sidelink slot without PSFCH (in this sidelink resource pool), FFP (1') is used. For example, FFP (1') can be from the initial symbol of the sidelink slot without PSFCH and, e.g., inclusive of, the last symbol of the sidelink slot without PSFCH. For a sidelink slot with PSFCH (in this sidelink resource pool), FFP (2') and FFP (3') are used. FFP (1') and FFP (2') can be used for COT for PSCCH and / or PSSCH transmission. FFP (3') can be used for COT for PSFCH. According to the third embodiment, sidelink transmission can be performed as soon as the channel is sensed to be free, which can reduce the likelihood of missing PSFCH, since there is a free duration before PSFCH for sensing.

[0567] The fourth embodiment is that each sidelink slot in a sidelink resource pool is a FFP, where 95% of the duration of the slot (e.g., sidelink slot) can be COT and 5% of the duration of the slot can be free duration. In some examples, according to SCS, the last symbol of the (slot and / or FFP) can be a gap symbol that can be suitable for sensing.

[0568] According to the first embodiment, the second embodiment, the third embodiment, and / or the fourth embodiment (and / or a combination of the first embodiment, the second embodiment, the third embodiment, and / or the fourth embodiment), a second UE can transmit a sidelink transmission that requires PSFCH feedback and the sidelink transmission can not include information related to a COT initiator. For a first UE to perform PSFCH (e.g., according to the first embodiment, the second embodiment, the third embodiment, and / or the fourth embodiment), the first UE can perform sensing to determine whether the sidelink transmission is within a COT of the first UE. Figure 7 According to Emb2 and / or Emb3 in FIG. 8, a first UE will initiate a COT for itself for PSFCH transmission.

[0569] In some examples, embodiments disclosed herein, e.g., embodiments described with respect to one or more of the concepts discussed, the first embodiment, the second embodiment, the third embodiment, and / or the fourth embodiment, can be implemented independently and / or separately. Alternatively and / or additionally, combinations of embodiments described herein, e.g., embodiments described with respect to one or more of the concepts discussed, the first embodiment, the second embodiment, the third embodiment, and / or the fourth embodiment, can be implemented. Alternatively and / or additionally, combinations of embodiments described herein, e.g., embodiments described with respect to one or more of the concepts discussed, the first embodiment, the second embodiment, the third embodiment, and / or the fourth embodiment, can be implemented in parallel and / or concurrently.

[0570] The various techniques, embodiments, methods, concepts, and / or alternatives of the present disclosure can be implemented independently and / or separately from one another. Alternatively and / or additionally, the various techniques, embodiments, methods, concepts, and / or alternatives of the present disclosure can be implemented in combination and / or with a single system. Alternatively and / or additionally, the various techniques, embodiments, methods, concepts, and / or alternatives of the present disclosure can be implemented contemporaneously and / or chronologically apart from one another.

[0571] With respect to one or more embodiments herein, such as one or more techniques, apparatuses, concepts, methods, example scenarios, and / or alternatives described above, in some examples, one, some, and / or all instances of “LBT” can be replaced with “channel access procedure.” For example, LBT and / or sensing exemption for sidelink (e.g., LBT and / or sensing exemption for PSFCH) can be replaced with channel access procedure exemption for sidelink, such as for PSFCH (e.g., a UE can be exempted from the requirement to perform a channel access procedure for a sidelink transmission (e.g., a UE can not need to perform a channel access procedure for a sidelink transmission based on the exemption). In some examples, a channel access procedure exemption can be implemented using one or more of the techniques provided herein with respect to implementing an LBT exemption. For example, whether a transmission (e.g., a sidelink transmission) is exempted from a channel access procedure (e.g., a Type 1 channel access procedure) can be determined using one or more of the techniques provided herein with respect to determining whether a sidelink transmission is exempted from an LBT and / or sensing exemption.

[0572] With respect to one or more embodiments herein, in some examples, LBT can be CAT-1, 2, 3, or 4 LBT.

[0573] With respect to one or more embodiments herein, in some examples, an end timing of a sidelink transmission can correspond to (and / or include) an orthogonal frequency-division multiplexing (OFDM) symbol (e.g., a gap symbol) for a gap.

[0574] With respect to one or more embodiments herein, in some examples, a UE can not be able to transmit a sidelink transmission on an OFDM symbol for a gap.

[0575] Alternatively and / or additionally, an end timing of a sidelink transmission can not correspond to (and / or can not include) an OFDM symbol (e.g., a gap symbol) for a gap.

[0576] With respect to one or more embodiments herein, in some examples, a slot in a sidelink resource pool can include an n-th to m-th symbol for sidelink.

[0577] With respect to one or more embodiments herein, in some examples, a gap symbol is an m-th symbol or an (m+1)-th symbol.

[0578] With respect to one or more embodiments herein, in some instances, a PSFCH can be used to convey (e.g., deliver and / or carry) and / or include sidelink HARQ feedback.

[0579] With respect to one or more embodiments herein, in some instances, a PSFCH can be used to convey (e.g., deliver and / or carry) and / or include inter-UE coordination information (e.g., Scheme 2) or resource conflict indication.

[0580] In some instances, one or more of the embodiments herein for conveying (e.g., delivering and / or carrying) and / or including sidelink HARQ feedback (e.g., for a PSFCH) can apply to a PSFCH for conveying (e.g., delivering and / or carrying) and / or including inter-UE coordination information (e.g., Scheme 2 inter-UE coordination information) and / or resource conflict indication. In some instances, the inter-UE coordination information (e.g., Scheme 2) and / or resource conflict indication can be to indicate that a reserved and / or scheduled sidelink resource (e.g., reserved by a TX UE) conflicts (and / or will conflict) with another sidelink resource reserved / scheduled by one or more other UEs. In this case of inter-UE coordination information (e.g., Scheme 2) or resource conflict indication, the UE or first UE conveying the PSFCH is UE-A, and the TX UE can be UE-B. For example, the inter-UE coordination information (e.g., Scheme 2 inter-UE coordination information) and / or resource conflict indication can be conveyed with a PSFCH using one or more of the techniques provided herein with respect to conveying sidelink HARQ feedback using a PSFCH.

[0581] In some instances, one or more of the embodiments herein for conveying (e.g., delivering and / or carrying) and / or including sidelink HARQ feedback (e.g., for a PSFCH) can apply to a PSFCH for one or more other purposes, features, and / or functions (and / or can apply in other applications).

[0582] With respect to one or more embodiments herein, in some instances, a second UE can transmit a unicast sidelink transmission on a shared COT (e.g., initiated by a first UE) if the unicast sidelink transmission is to the first UE.

[0583] With respect to one or more embodiments herein, in some instances, a second UE can transmit a broadcast or groupcast sidelink transmission on a shared COT (e.g., initiated by a first UE) if the broadcast or groupcast sidelink transmission includes a target UE corresponding to the first UE.

[0584] With respect to one or more embodiments herein, in some instances, the second UE does not transmit (and / or is not allowed to transmit) a unicast sidelink transmission on a shared COT (e.g., initiated by the first UE) if the unicast sidelink transmission is not intended for the first UE.

[0585] With respect to one or more embodiments herein, in some instances, the second UE does not transmit (and / or is not allowed to transmit) a broadcast or groupcast sidelink transmission on a shared COT (e.g., initiated by the first UE) if the broadcast or groupcast sidelink transmission does not contain a target UE corresponding to the first UE.

[0586] With respect to one or more embodiments herein, in some instances, the first sidelink transmission is scheduled by a 1st stage SCI and a 2nd stage SCI.

[0587] With respect to one or more embodiments herein, in some instances, a UE performing successful LBT can refer to a UE sensing a channel idle according to a LBT required duration (via LBT).

[0588] With respect to one or more embodiments herein, in some instances, a UE performing LBT failure (and / or a UE failing LBT) can refer to a UE sensing a channel not idle according to a LBT required duration (via LBT) (e.g., the UE senses the channel busy).

[0589] With respect to one or more embodiments herein, in some instances, a UE performing successful LBT can refer to an energy of a channel sensed by the UE (via LBT) being less than or equal to an energy threshold and / or an energy detection threshold.

[0590] With respect to one or more embodiments herein, in some instances, a UE performing LBT failure (and / or a UE failing LBT) can refer to an energy of a channel sensed by the UE (via LBT) being greater than an energy threshold and / or an energy detection threshold.

[0591] With respect to one or more embodiments herein, in some instances, the first sidelink transmission is associated with (e.g., is in) a first sidelink resource pool. In some instances, the second sidelink transmission is associated with (e.g., is in) a second sidelink resource pool. In some instances, the first sidelink resource pool and the second sidelink resource pool are a same pool or different pools. In some instances, the first sidelink resource pool is associated with (e.g., is in) a first carrier / cell. In this disclosure, the term “carrier / cell” can refer to a carrier and / or a cell. In some instances, the second sidelink resource pool is associated with (e.g., is in) a second carrier / cell. In some instances, the first carrier / cell and the second carrier / cell can be a same carrier / cell or different carriers / cells. In some instances, the first carrier / cell is associated with a shared and / or unlicensed spectrum. In some instances, the second carrier / cell is associated with a shared and / or unlicensed spectrum. In some instances, a UE (e.g., the first UE or the second UE) can perform at least one type of LBT or perform sensing (e.g., over one or more sensing slots) prior to performing the sidelink transmission. In some instances, the first UE operates in shared spectrum channel access.

[0592] With respect to one or more embodiments herein, in some instances, the second UE operates in shared spectrum channel access.

[0593] With respect to one or more embodiments herein, in some instances, the apparatus can be a UE or a network node.

[0594] In some instances, in this disclosure, the term “timing” can refer to at least one of a time unit, a slot, a symbol, a time point, a time location, a location, a time domain location, etc.

[0595] In some instances, one, some, and / or all instances of “timing” can be replaced with (and / or used interchangeably with) “time unit,” “slot,” “symbol,” “time point,” “time location,” “location,” and / or “time domain location.”

[0596] Figure 8is a flowchart 800 from the perspective of a first UE according to one example embodiment. In step 805, the first UE receives a sidelink transmission from a second UE, where the second UE provides a second HARQ process number (e.g., of the second UE) for the sidelink transmission, and the sidelink transmission is associated with enabled HARQ (e.g., HARQ feedback is enabled for the sidelink transmission). In step 810, the first UE performs a second sidelink transmission for at least a sidelink HARQ retransmission to the second UE, where the sidelink HARQ (e.g., sidelink HARQ feedback) is responsive to the sidelink transmission. For example, the sidelink HARQ can indicate to the second UE whether the sidelink transmission was successfully received by the first UE.

[0597] In one embodiment, the sidelink HARQ is associated with the second HARQ process number (e.g., of the second UE).

[0598] In one embodiment, the sidelink HARQ is not based on the first HARQ process number of the first UE.

[0599] In one embodiment, the first UE uses (e.g., assigns) the first HARQ process number of the first UE to process the sidelink transmission.

[0600] In one embodiment, the first HARQ process number is different than the second HARQ process number.

[0601] In one embodiment, the first HARQ process number can be the same as the second HARQ process number.

[0602] In one embodiment, one or more of the techniques provided herein inform the second UE which HARQ process number of the second UE is associated with the sidelink HARQ (e.g., retransmitted sidelink HARQ). In an example, the second sidelink transmission of the sidelink HARQ (e.g., the second sidelink transmission for retransmitting the sidelink HARQ) can indicate that the sidelink HARQ is associated with the second HARQ process number of the second UE, which can inform the second UE that the sidelink HARQ corresponds to feedback responsive to the sidelink transmission (associated with the second HARQ process number of the second UE) transmitted by the second UE. In some examples, based on a determination that the HARQ process number of the second UE for the sidelink transmission is the second HARQ process number (e.g., the determination can be based on an indication received by the first UE from the second UE that the sidelink transmission is associated with the HARQ process number), the first UE can indicate to the second UE and via the second sidelink transmission that the sidelink HARQ is associated with the second HARQ process number (rather than the first HARQ process number used by the first UE to process the sidelink transmission).

[0603] In one embodiment, the first UE fails to access and / or occupy the channel (e.g., the first UE fails to access a channel for transmitting a sidelink HARQ feedback in response to a sidelink transmission).

[0604] In one embodiment, the first UE fails to pass an LBT for transmitting a PSFCH in response to a sidelink transmission. For example, an LBT result of an LBT performed by the first UE for transmitting a PSFCH in response to a sidelink transmission (e.g., a PSFCH including a sidelink HARQ feedback in response to a sidelink transmission) can correspond to busy.

[0605] In one embodiment, the number of consecutive slots is based on one or more available slots for sidelink in the SL BWP or in the carrier. The number of consecutive slots can correspond to a number of slots of a set of consecutive sidelink slots available in the SL BWP or in the carrier. In an example, there can be a number of consecutive slots corresponding to “DUDDSSSU”, where “D” denotes a downlink slot, “U” denotes an uplink slot, and “S” denotes a sidelink slot (available for sidelink in the SL BWP or in the carrier). Thus, the set of consecutive slots (available in the SL BWP or in the carrier) can correspond to three sidelink slots “SSS” and / or the number of consecutive slots can be three.

[0606] In one embodiment, lengths of different FFPs in a sidelink resource pool (e.g., a sidelink resource pool including sidelink resources for sidelink transmissions and / or second sidelink transmissions) can be different from each other based on different consecutive numbers of slots in the carrier.

[0607] In one embodiment, the first UE can receive a first request to perform a second sidelink transmission (and / or other sidelink transmissions) for retransmitting at least a sidelink HARQ.

[0608] In one embodiment, the first request is transmitted by a second UE.

[0609] In one embodiment, the first request can be a request for one or more sidelink HARQs associated with a plurality of HARQ process numbers.

[0610] In one embodiment, the first request can be a request for sidelink HARQs associated with all HARQ process numbers (e.g., all HARQ process numbers of the second UE or all HARQ process numbers of a requested UE such as the first UE).

[0611] In one embodiment, the first request can be a request for a subset of sidelink HARQs in a plurality of sidelink HARQs associated with all HARQ process numbers of the second UE.

[0612] In one embodiment, the first request can be a request for sidelink HARQ associated with a HARQ process number (e.g., a particular HARQ process number), e.g., a HARQ process number (e.g., a particular HARQ process number) of the second UE.

[0613] In one embodiment, the first request can indicate a codepoint associated with one or more HARQ process numbers.

[0614] In one embodiment, the first UE and the second UE can have PC5-RRC signaling of each other.

[0615] In one embodiment, the PC5-RRC signaling can have one or more codepoints, and / or each codepoint of the one or more codepoints can indicate one or more HARQ process numbers associated with the requested UE.

[0616] In one embodiment, the first UE maintains an association (e.g., a relationship) between a second HARQ process number of the second UE and a first HARQ process number of the first UE. In an instance, the first UE can determine that the second HARQ process number of the second UE corresponds to the first HARQ process number of the first UE.

[0617] In one embodiment, when the first UE transmits a plurality of sidelink HARQs associated with a plurality of HARQ process numbers, an arrangement (e.g., an order) of the plurality of sidelink HARQs (e.g., an order in which the plurality of sidelink HARQs are arranged in a bitmap) is based on an increasing order of HARQ process numbers of the second UE (e.g., a sidelink HARQ ACK associated with a smaller HARQ process number of the second UE can be arranged ahead of and / or before a sidelink HARQ ACK associated with a larger HARQ process number of the second UE) or a decreasing order of HARQ process numbers of the second UE (e.g., a sidelink HARQ ACK associated with a larger HARQ process number of the second UE can be arranged ahead of and / or before a sidelink HARQ ACK associated with a smaller HARQ process number of the second UE).

[0618] In one embodiment, when the first UE transmits multiple sidelink HARQs associated with multiple HARQ process numbers, the arrangement (e.g., order) of the multiple sidelink HARQs (e.g., the order in which the multiple sidelink HARQs are arranged in a bitmap) is based on an increasing order of HARQ process numbers of the requested UEs of the first UE (e.g., a sidelink HARQ ACK associated with a smaller HARQ process number of a requested UE can be arranged ahead of and / or before a sidelink HARQ ACK associated with a larger HARQ process number of a requested UE) or a decreasing order of HARQ process numbers of the requested UEs of the first UE (e.g., a sidelink HARQ ACK associated with a larger HARQ process number of a requested UE can be arranged ahead of and / or before a sidelink HARQ ACK associated with a smaller HARQ process number of a requested UE).

[0619] In one embodiment, when the first UE transmits multiple sidelink HARQs associated with multiple HARQ process numbers, the arrangement (e.g., order) of the multiple sidelink HARQs (e.g., the order in which the multiple sidelink HARQs are arranged in a bitmap) is based on an order of HARQ process numbers associated with codepoints (e.g., a particular order of HARQ process numbers).

[0620] In one embodiment, the first UE can provide a second HARQ process number (and / or information associated with the second HARQ process number) along with the sidelink HARQ (e.g., the first UE can transmit an indication of the second HARQ process number and the sidelink HARQ in the same transmission, where the transmission can indicate that the sidelink HARQ is associated with the second HARQ process number).

[0621] In one embodiment, the second sidelink transmission for at least retransmitting the sidelink HARQ can be delivered by a PSCCH, a PSSCH, a 1ststage SCI, a 2ndstage SCI, and / or a PSFCH.

[0622] In one embodiment, the second sidelink transmission for at least retransmitting the sidelink HARQ is not delivered by a PSFCH.

[0623] In one embodiment, when the second sidelink transmission for at least retransmitting the sidelink HARQ is delivered by a PSFCH, a PSFCH format used for delivering multiple sidelink HARQs (e.g., a long format of a PSFCH) is used (e.g., the second sidelink transmission can include a transmission according to a PSFCH format, such as a long format of a PSFCH).

[0624] In one embodiment, the first UE triggers resource selection for transmitting sidelink HARQ on PSFCH in response to the timer expiring or the counter reaching the threshold value and / or after the window.

[0625] In one embodiment, the first UE triggers resource selection for transmitting sidelink HARQ on PSFCH based on a determination that the timer expires, the counter satisfies the threshold value, and / or the window elapses (e.g., the current time is after an end of the window).

[0626] In one embodiment, the first UE determines that the window starts at an original timing of PSFCH (e.g., a timing of a PSFCH resource that the first UE failed to access for transmitting sidelink HARQ), and / or at a timing of a PSCCH / PSSCH / PSFCH (e.g., an original PSCCH / PSSCH / PSFCH) in response to which the sidelink HARQ is.

[0627] In one embodiment, the first UE receives PSCCH1, PSSCH1, and / or PSFCH from the second UE in slot n. The first UE can determine to transmit sidelink HARQ feedback on PSFCH in slot m, where the sidelink HARQ feedback is in response to PSCCH1, PSSCH1, and / or PSFCH.

[0628] In one embodiment, the window starts from a start symbol of slot n, slot m, slot n+1, or slot m+1.

[0629] In one embodiment, the first UE retransmits (e.g., in slot k before the window elapses) the sidelink HARQ on another PSFCH resource (e.g., different from the PSFCH resource that the first UE failed to access for transmitting the sidelink HARQ).

[0630] In one embodiment, before the window elapses (e.g., during the window), the first UE can determine a start (e.g., a start timing) of the window (e.g., re-determine an updated version of the start) if the first UE can transmit the sidelink HARQ feedback on another PSFCH resource, e.g., in slot k.

[0631] Referring back to Figure 3 and 4In one example embodiment of the first UE, the apparatus 300 includes program code 312 stored in the memory 310. The CPU 308 can execute the program code 312 to enable the first UE to: (i) receive a sidelink transmission from a second UE, wherein the second UE provides a second HARQ process number for the sidelink transmission, and the sidelink transmission is associated with enabled HARQ, and (ii) perform a second sidelink transmission for at least a sidelink HARQ retransmission to the second UE, wherein the sidelink HARQ is responsive to the sidelink transmission. In addition, the CPU 308 can execute the program code 312 to perform one, some, and / or all of the above actions and steps and / or other actions and steps described herein.

[0632] Figure 9 is a flowchart 900 from the perspective of a first UE according to one example embodiment. In step 905, the first UE performs a sidelink transmission on a cell (e.g., a cell in unlicensed spectrum). In step 910, the first UE receives a sidelink transmission from a second UE. In step 915, the first UE transmits a sidelink HARQ (e.g., sidelink HARQ feedback) in response to the sidelink transmission, wherein the first UE performs LBT exemption from resources (e.g., the resources are associated with LBT exemption and / or the resources can be exempted from LBT requirement) that the first UE uses to transmit the sidelink HARQ.

[0633] Referring back to Figure 3 and 4 In one example embodiment of the first UE, the apparatus 300 includes program code 312 stored in the memory 310. The CPU 308 can execute the program code 312 to enable the first UE to: (i) perform a sidelink transmission on a cell (e.g., a cell in unlicensed spectrum), (ii) receive a sidelink transmission from a second UE, and (iii) transmit a sidelink HARQ in response to the sidelink transmission, wherein the first UE performs LBT exemption from resources that the first UE uses to transmit the sidelink HARQ. In addition, the CPU 308 can execute the program code 312 to perform one, some, and / or all of the above actions and steps and / or other actions and steps described herein.

[0634] Figure 10 is a flowchart 1000 from the perspective of a network node according to one example embodiment. In step 1005, the network node provides (e.g., transmits) a configuration to a first UE, wherein the configuration indicates that a transmission of a sidelink channel / signal is exempted from LBT, wherein a duration (e.g., a time duration) of the LBT exemption for the sidelink channel / signal during an interval is not greater than a threshold. In this disclosure, the term “sidelink channel / signal” can refer to a sidelink channel and / or a sidelink signal.

[0635] Referring back Figure 3 and 4 In one example embodiment of a network node, the apparatus 300 includes program code 312 stored in the memory 310. The CPU 308 can execute the program code 312 to enable the network node to: (i) provide (e.g., transmit) a configuration to a first UE, wherein the configuration indicates that transmission of a sidelink channel / signal is exempt from LBT, wherein a duration (e.g., a time duration) of the LBT exemption for the sidelink channel / signal during an interval is not greater than a threshold. In addition, the CPU 308 can execute the program code 312 to perform one, some and / or all of the above actions and steps and / or other actions and steps described herein.

[0636] Figure 11 is a flowchart 1100 from the perspective of a first UE according to one example embodiment. In step 1105, the first UE receives a configuration (e.g., a pre-configuration), wherein a parameter (e.g., one parameter) in the configuration indicates whether transmission of a sidelink channel / signal is exempt from a requirement to perform a Type 1 channel access procedure. In step 1110, based on the parameter (e.g., based on the indication of the parameter in the configuration), the first UE transmits the sidelink channel / signal without performing the Type 1 channel access procedure. For example, the first UE can transmit the sidelink channel / signal without performing the Type 1 channel access procedure based on the parameter indicating that transmission of the sidelink channel / signal is exempt from the requirement to perform the Type 1 channel access procedure.

[0637] With respect to Figures 9-11 In one embodiment, in response to determining to transmit the sidelink channel / signal without performing the Type 1 channel access procedure (e.g., the determination to transmit the sidelink channel / signal without performing the Type 1 channel access procedure can be based on the parameter, such as a determination that transmission of the sidelink channel / signal is exempt from the requirement to perform the Type 1 channel access procedure), the first UE transmits the sidelink channel / signal without performing the Type 1 channel access procedure.

[0638] In one embodiment, in response to determining to transmit the sidelink channel / signal with the Type 1 channel access procedure (e.g., the determination to transmit the sidelink channel / signal with the Type 1 channel access procedure can be based on the parameter, such as a determination that transmission of the sidelink channel / signal is not exempt from the requirement to perform the Type 1 channel access procedure), the first UE can transmit the sidelink channel / signal with performing the Type 1 channel access procedure (e.g., the first UE can use the Type 1 channel access procedure to perform the transmission of the sidelink channel / signal).

[0639] In one embodiment, a duration (e.g., a duration) of LBT exemption for a sidelink channel / signal during a gap is determined based on a periodicity of the sidelink channel / signal (and / or based on other information, e.g., in addition to the periodicity).

[0640] In one embodiment, the parameter (e.g., the one parameter in the configuration) indicates: (i) a pool-specific subset of locations (e.g., a subset of resources of a sidelink resource pool) for one or more sidelink channels and / or signals (e.g., sidelink channels / signals) for which a requirement exemption from performing a Type 1 channel access procedure, (ii) an LBT band-specific subset of locations (e.g., a subset of resources of an LBT band) for one or more sidelink channels and / or signals (e.g., sidelink channels / signals) for which a requirement exemption from performing a Type 1 channel access procedure, (iii) a carrier-specific subset of locations (e.g., a subset of resources of a carrier) for one or more sidelink channels and / or signals (e.g., sidelink channels / signals) for which a requirement exemption from performing a Type 1 channel access procedure, and / or (iv) a SL BWP-specific subset of locations (e.g., a subset of resources of a SL BWP) for one or more sidelink channels and / or signals (e.g., sidelink channels / signals) for which a requirement exemption from performing a Type 1 channel access procedure.

[0641] In one embodiment, the parameter (e.g., the one parameter in the configuration) indicates: (i) all pool-specific locations (e.g., all resources of a sidelink resource pool) for one or more sidelink channels and / or signals (e.g., sidelink channels / signals) for which a requirement exemption from performing a Type 1 channel access procedure, (ii) all LBT band-specific locations (e.g., all resources of an LBT band) for one or more sidelink channels and / or signals (e.g., sidelink channels / signals) for which a requirement exemption from performing a Type 1 channel access procedure, (iii) all carrier-specific locations (e.g., all resources of a carrier) for one or more sidelink channels and / or signals (e.g., sidelink channels / signals) for which a requirement exemption from performing a Type 1 channel access procedure, and / or (iv) all SL BWP-specific locations (e.g., all resources of a SL BWP) for one or more sidelink channels and / or signals (e.g., sidelink channels / signals) for which a requirement exemption from performing a Type 1 channel access procedure.

[0642] In one embodiment, the parameter indicates a set of locations in a carrier for one or more sidelink channels and / or signals (e.g., sidelink channels / signals) for which a requirement exemption from performing a Type 1 channel access procedure.

[0643] In one embodiment, the parameter (e.g., the indication of the parameter in the configuration) guarantees that an occupancy duration for the sidelink channel / signal during the interval is not greater than a threshold (e.g., the first UE is configured via the parameter to perform the sidelink channel / signal such that the occupancy duration for the sidelink channel / signal during the interval is not greater than the threshold).

[0644] In one embodiment, the configuration (e.g., pre-configuration) is a per-sidelink resource pool, per-SL BWP, or per-carrier configuration. For example, there can be a (e.g., unique) configuration for each sidelink resource pool, each SL BWP, and / or each carrier.

[0645] In one embodiment, the sidelink channel / signal is a PSFCH and / or a sidelink synchronization signal / PBCH block (SL-SSB).

[0646] Referring back to Figure 3 and 4 In one example embodiment of the first UE, the apparatus 300 includes program code 312 stored in the memory 310. The CPU 308 can execute the program code 312 to enable the first UE to: (i) receive a configuration (e.g., a pre-configuration), where a parameter (e.g., one parameter) in the configuration indicates whether a transmission of a sidelink channel / signal is exempted from a requirement to perform a Type 1 channel access procedure, and (ii) transmit the sidelink channel / signal without performing the Type 1 channel access procedure based on the parameter (e.g., based on the indication of the parameter in the configuration). In addition, the CPU 308 can execute the program code 312 to perform one, some, and / or all of the above actions and steps and / or other actions and steps described herein.

[0647] Figure 12 is a flowchart 1200 from the perspective of a first UE according to one example embodiment. In step 1205, the first UE receives a configuration (e.g., a pre-configuration) associated with a sidelink resource pool. In step 1210, the first UE performs a sidelink transmission in an unlicensed cell. In step 1215, the first UE determines whether to transmit a sidelink channel / signal without performing a Type 1 channel access procedure based on whether an occupancy duration for the sidelink channel / signal during an interval is greater than a threshold (and / or based on other information in addition to whether the occupancy duration for the sidelink channel / signal during the interval is greater than the threshold). In some instances, the occupancy duration can correspond to a duration of occupancy by the transmission of the sidelink channel / signal.

[0648] In one embodiment, the occupancy duration for the sidelink channel / signal during the interval is determined based on a configuration (e.g., pre-configuration) associated with timing of the sidelink channel / signal in the sidelink resource pool.

[0649] In one embodiment, if the occupancy duration for the sidelink channel / signal during the interval is not greater than the threshold (e.g., if the duration occupied by the transmission of the sidelink channel / signal during the interval is not greater than the threshold), the first UE can transmit the sidelink channel / signal without performing the Type 1 channel access procedure.

[0650] In one embodiment, if the occupancy duration for the sidelink channel / signal during the interval is greater than the threshold (e.g., if the duration occupied by the transmission of the sidelink channel / signal during the interval is greater than the threshold), the first UE is not configured (and / or not allowed) to transmit the sidelink channel / signal without performing the Type 1 channel access procedure (e.g., the first UE can perform the Type 1 channel access procedure for transmitting the sidelink channel / signal).

[0651] In one embodiment, a subset of the pool-specific locations, a subset of the LBT band-specific locations, a subset of the carrier-specific locations, and / or a subset of the SL BWP-specific locations for the sidelink channel / signal are exempted from (e.g., exempted from performing) the Type 1 channel access procedure.

[0652] In one embodiment, all of the pool-specific locations, all of the LBT band-specific locations, all of the carrier-specific locations, and / or all of the SL BWP-specific locations for the sidelink channel / signal are exempted from (e.g., exempted from performing) the Type 1 channel access procedure.

[0653] Referring back to Figure 3 and 4 In one example embodiment of the first UE, the apparatus 300 includes program code 312 stored in the memory 310. The CPU 308 can execute the program code 312 to enable the first UE to: (i) receive a configuration (e.g., pre-configuration) associated with a sidelink resource pool, (ii) perform a sidelink transmission in an unlicensed cell, and (iii) determine whether to transmit a sidelink channel / signal without performing a Type 1 channel access procedure based on whether an occupancy duration for the sidelink channel / signal during an interval is greater than a threshold. In addition, the CPU 308 can execute the program code 312 to perform one, some, and / or all of the above actions and steps and / or other actions and steps described herein.

[0654] Figure 13is a flowchart 1300 from a first UE's perspective according to one example embodiment. In step 1305, the first UE receives a SCI from a second UE, where the SCI indicates that HARQ feedback is enabled for a scheduled sidelink transmission. In step 1310, based on a configuration (e.g., pre-configuration) of a PSFCH FFP, the first UE performs sensing during an idle duration of the PSFCH FFP prior to a PSFCH resource (e.g., timing of the PSFCH) in response to the scheduled sidelink transmission. In step 1315, if a sensing result of the sensing is idle, the first UE transmits a PSFCH to the second UE.

[0655] In one embodiment, the configuration of the PSFCH FFP is for one or more UEs (e.g., the first UE) in a sidelink resource pool and / or for transmitting one or more PSFCHs (e.g., the PSFCH). For example, the configuration of the PSFCH FFP can be used by the one or more UEs (e.g., the first UE) for transmitting the one or more PSFCHs (e.g., the PSFCH) using the sidelink resource pool (e.g., the sidelink resource pool can be used for transmitting the one or more PSFCHs).

[0656] In one embodiment, the idle duration of the PSFCH FFP is based on a PSFCH periodicity.

[0657] In one embodiment, a maximum channel occupancy according to the PSFCH FFP is based on a number of PSFCH symbols (e.g., 2 symbols) in a slot.

[0658] In one embodiment, the configuration of the PSFCH FFP is pool-specific (e.g., the configuration of the PSFCH FFP can be the same for a pool). For example, transmissions performed using the pool can be performed according to the configuration.

[0659] In one embodiment, the configuration of the PSFCH FFP is SL BWP-specific (e.g., the configuration of the PSFCH FFP can be the same for a SL BWP). For example, transmissions performed using the SL BWP can be performed according to the configuration.

[0660] In one embodiment, the configuration of the PSFCH FFP is carrier-specific (e.g., the configuration of the PSFCH FFP can be the same for a carrier). For example, transmissions performed using the carrier can be performed according to the configuration.

[0661] In one embodiment, the first UE performs sensing based on a configuration of the PSFCH FFP based on the SCI indicating that the COT initiator is the first UE (e.g., the RX UE). Alternatively and / or additionally, the first UE can transmit the PSFCH in response to the sidelink transmission based on the channel occupancy of the own UE when the second UE provides information with COT information is the second UE (or TX UE).

[0662] In one embodiment, the first UE initiates the COT for transmitting the PSFCH when there is no channel occupancy (e.g., overlapping with, such as fully overlapping with) covering the PSFCH.

[0663] In one embodiment, the first UE initiates the COT for transmitting the PSFCH when there is no channel occupancy for the time resources of the PSFCH.

[0664] In one embodiment, the first UE performs sensing before transmitting the PSFCH.

[0665] In one embodiment, if the first UE has a prior channel occupancy (which can cover the timing of the PSFCH, such as overlapping with), the first UE determines whether to transmit the PSFCH with or without sensing based on a time gap between the prior sidelink transmission in the channel occupancy time and the PSFCH (e.g., whether the first UE performs sensing for transmitting the PSFCH can be based on the time gap).

[0666] In one embodiment, when the first UE transmits the SCI and / or PSSCH to the third UE, the first UE is not configured (e.g., the first UE cannot and / or is not allowed) to perform sensing according to the PSFCH FFP.

[0667] In one embodiment, when the first UE transmits the SCI and / or PSSCH to the third UE, the first UE can use a second configuration (e.g., a second pre-configuration) for the PSSCH and / or PSCCH FFP.

[0668] In one embodiment, the second configuration is pool-specific (e.g., the second configuration can be the same for a pool). For example, the transmission performed using the pool can be performed according to the second configuration.

[0669] In one embodiment, the second configuration is SL BWP-specific (e.g., the second configuration can be the same for a SL BWP). For example, the transmission performed using the SL BWP can be performed according to the second configuration.

[0670] In one embodiment, the second configuration is carrier-specific (e.g., the second configuration can be the same for a carrier). For example, transmissions performed using the carrier can be performed in accordance with the second configuration. In one embodiment, the second configuration is common for a group (e.g., for a group of UEs) for groupcast sidelink transmissions. Alternatively and / or additionally, when the first UE performs a groupcast sidelink transmission, the first UE can perform sensing based on the second configuration (e.g., the first UE can perform sensing for the group and / or the second configuration can be for the group).

[0671] In one embodiment, the second configuration is link-specific (e.g., the second configuration is associated with a link, e.g., where the second configuration is used to perform sensing and / or transmissions on the link). Alternatively and / or additionally, the second configuration can be based on PC5-RRC signaling (e.g., between the first UE and the third UE). Alternatively and / or additionally, when the first UE performs a unicast sidelink transmission, the first UE performs sensing based on the second configuration (e.g., for the link).

[0672] In one embodiment, when the second UE provides information indicating that the COT initiator is the second UE (or TX UE), the first UE can transmit a PSFCH in response to a sidelink transmission based on a channel occupancy of the second UE.

[0673] In one embodiment, the PSFCH resource and / or the resource for the sidelink transmission (transmitted by the second UE) is in a shared and / or unlicensed spectrum.

[0674] In one embodiment, a symbol level offset for a PSFCH FFP is based on (e.g., implicitly derived from) a starting symbol for a sidelink in a slot belonging to a sidelink resource pool.

[0675] Referring back to Figure 3 and 4 In one example embodiment of the first UE, the apparatus 300 includes program code 312 stored in the memory 310. The CPU 308 can execute the program code 312 to enable the first UE to: (i) receive SCI from a second UE, where the SCI indicates that HARQ feedback is enabled for a scheduled sidelink transmission, (ii) perform sensing during an idle duration of a PSFCH FFP prior to a PSFCH resource (e.g., timing of the PSFCH) based on a configuration (e.g., pre-configuration) of the PSFCH FFP, where the PSFCH resource is in response to the scheduled sidelink transmission, and (iii) transmit a PSFCH to the second UE if a sensing result of the sensing is idle. In addition, the CPU 308 can execute the program code 312 to perform one, some, and / or all of the above actions and steps and / or other actions and steps described herein.

[0676] Figure 14 is a flow diagram 1400 from the perspective of a first UE according to one example embodiment. In step 1405, the first UE receives, in a first timing, a sidelink transmission from a second UE, where the sidelink transmission is associated with enabled sidelink HARQ feedback. For example, sidelink HARQ feedback functionality can be enabled for the sidelink transmission. For example, based on the sidelink HARQ feedback functionality being enabled for the sidelink transmission, the second UE can expect sidelink HARQ feedback from the first UE for indicating whether the first UE successfully received the sidelink transmission from the second UE. In step 1410, the first UE attempts to access a channel for transmission of the sidelink HARQ feedback in a first feedback resource in a second timing. The attempt to access the channel for transmission of the sidelink HARQ feedback in the first feedback resource fails (e.g., the first UE fails to access the channel for transmitting the sidelink HARQ feedback in the first feedback resource). The sidelink HARQ feedback is responsive to the sidelink transmission. For example, the sidelink HARQ feedback can indicate whether the first UE successfully received the sidelink transmission from the second UE. In step 1415, the first UE performs channel access for a second feedback resource, where the second feedback resource is within a window (e.g., a time of the second feedback resource is during the window) and / or within a predefined duration of the first timing or the second timing (e.g., a time of the second feedback resource is within the predefined duration of the first timing or the second timing). The channel access for the second feedback resource is successfully performed (e.g., the first UE can successfully access the second channel for transmitting the sidelink HARQ feedback using the second feedback resource). In an instance, the channel access can correspond to semi-static channel access and / or dynamic channel access. In step 1420, in response to successfully performing the channel access for the second feedback resource, the first UE performs sidelink feedback transmission of the sidelink HARQ feedback to the second UE in the second feedback resource.

[0677] In an instance where the predefined duration corresponds to a length of 10 ms, the second feedback resource can be within 10 ms of the first timing or the second timing (e.g., between 0 ms and 10 ms after the first timing or the second timing).

[0678] In one embodiment, the first UE receives the sidelink transmission in a first timing. The first timing can correspond to at least one of a time unit, a slot, a symbol, a time point, a time location, a location, a time domain location, etc.

[0679] In one embodiment, the first feedback resource is in a second timing. In one embodiment, the first UE attempts to access the channel (for transmitting the sidelink HARQ feedback) and / or fails to attempt to access the channel (e.g., the first UE fails to access the channel for transmitting the sidelink HARQ feedback) in the second timing. The second timing can correspond to at least one of a time unit, a slot, a symbol, a time point, a time location, a location, a time-domain location, and / or the like.

[0680] In one embodiment, the first UE performs the sidelink feedback transmission (of the sidelink HARQ feedback) in the third timing (in the second feedback resource). The third timing can correspond to at least one of a time unit, a slot, a symbol, a time point, a time location, a location, a time-domain location, and / or the like.

[0681] In one embodiment, the first timing is prior to (e.g., earlier than) the second timing.

[0682] In one embodiment, the second timing is prior to (e.g., earlier than) the third timing.

[0683] In one embodiment, the first UE determines the start of the window based on the first timing or the second timing. In some instances, the window starts from the first timing or the second timing. The start of the window can correspond to at least one of a start time of the window, a start slot of the window (e.g., a slot in which the window starts), a start symbol of the window (e.g., a symbol in which the window starts), and / or the like. In some instances, the start of the window is determined in response to the first timing or the second timing (e.g., in response to receiving the sidelink transmission in the first timing and / or in response to attempting to access and / or failing to access the channel in the second timing). In some instances, a duration (e.g., at least one of a time length, a number of slots, and / or the like) of the window can correspond to a predefined value, e.g., a value determined (e.g., predetermined) and / or configured (e.g., preconfigured) (e.g., the first UE can determine the predefined value prior to the start of the window and / or be configured with the predefined value). In instances in which the predefined value (and / or the duration of the window) corresponds to a time length, and the window starts from a start time (e.g., the first timing or the second timing), the window can extend from the start time to an end time, where the end time can correspond to a sum of the start time and the time length.

[0684] In one embodiment, the predefined duration of the first timing or the second timing includes or means a predefined duration from the first timing or the second timing. The predefined duration (e.g., at least one of a time length, a number of slots, etc.) can correspond to a predefined value, e.g., a value determined (e.g., predetermined) and / or configured (e.g., preconfigured) (e.g., the first UE can determine the predefined value before the first timing or the second timing and / or be configured with the predefined value). In an instance in which the predefined duration is a time length, and the second feedback resource is within the predefined duration of the first timing, the second feedback resource can be within a time span extending from the first timing (e.g., a start time of the time span) to an end time, where the end time can correspond to a sum of the first timing (e.g., the start time) and the time length, where the first UE can determine the predefined duration before the first timing and / or be configured with the predefined duration. In an instance in which the predefined duration is a time length, and the second feedback resource is within the predefined duration of the second timing, the second feedback resource can be within a time span extending from the second timing (e.g., a start time of the time span) to an end time, where the end time can correspond to a sum of the second timing (e.g., the start time) and the time length, where the first UE can determine the predefined duration before the second timing and / or be configured with the predefined duration.

[0685] In one embodiment, the window and / or the predefined duration is associated with (e.g., used for) retransmission of the sidelink HARQ feedback without receiving a signal (e.g., a request, e.g., a request to perform one or more sidelink transmissions) from the second UE. For example, the window and / or the predefined duration can be used by the first UE to retransmit the sidelink HARQ feedback without receiving a signal (e.g., a request) from the second UE. For example, during the window and / or within the predefined duration of the first timing or the second timing (e.g., during a time span associated with the predefined duration), the first UE can perform one or more retransmissions of the sidelink HARQ feedback (and / or one or more retransmissions of one or more other sidelink HARQ feedbacks) without receiving a signal (e.g., a request) from the second UE.

[0686] In one embodiment, the window and / or the predefined duration is associated with (e.g., used for) retransmission of the sidelink HARQ feedback without triggering resource selection. For example, the window and / or the predefined duration can be used by the first UE to retransmit the sidelink HARQ feedback without triggering resource selection (e.g., without triggering and / or performing resource selection for retransmission of the sidelink HARQ feedback). For example, during the window and / or within the predefined duration of the first timing or the second timing (e.g., during a time span associated with the predefined duration), the first UE can perform one or more retransmissions of the sidelink HARQ feedback (and / or one or more retransmissions of one or more other sidelink HARQ feedbacks) without triggering resource selection (e.g., without triggering and / or performing resource selection for retransmission of the sidelink HARQ feedback).

[0687] In one embodiment, the window and / or the time span associated with the predefined duration is different from the channel occupancy time (e.g., the window and / or the time span associated with the predefined duration is not the channel occupancy time).

[0688] In one embodiment, the first UE performs the sidelink feedback transmission of the sidelink HARQ feedback during the window and / or within the predefined duration of the first timing or the second timing (e.g., during a time span associated with the predefined duration).

[0689] In one embodiment, if the third timing is during the window and / or within the predefined duration of the first timing or the second timing (e.g., during a time span associated with the predefined duration), the first UE performs the sidelink feedback transmission of the sidelink HARQ feedback without triggering resource selection (e.g., without triggering and / or performing resource selection for the sidelink feedback transmission of the sidelink HARQ feedback).

[0690] In one embodiment, if the third timing is after the window and / or after the time span associated with the predefined duration, the first UE triggers resource selection for transmitting the sidelink HARQ feedback.

[0691] In one embodiment, the first UE determines whether to trigger resource selection for sidelink feedback transmission of the sidelink HARQ feedback based on whether the third timing is during the window and / or within a predefined duration of the first timing or the second timing (e.g., whether the third timing is during a time span associated with the predefined duration). The first UE can determine to perform the sidelink feedback transmission of the sidelink HARQ feedback without triggering resource selection based on the third timing being during the window and / or within the predefined duration of the first timing or the second timing (e.g., whether the third timing is during the time span associated with the predefined duration). Alternatively and / or additionally, the first UE can determine to trigger resource selection for transmitting the sidelink HARQ feedback based on the third timing being after the window and / or after the time span associated with the predefined duration.

[0692] In one embodiment, the sidelink feedback transmission of the sidelink HARQ feedback is performed using a PSFCH format associated with delivery of multiple sidelink HARQ feedbacks. For example, a PSFCH format (e.g., a long format for a PSFCH used to deliver multiple sidelink HARQ feedbacks) is used for the sidelink feedback transmission of the sidelink HARQ feedback. In an example, the PSFCH format can be associated with a size that is larger than a (smaller) PSFCH format associated with delivery of a single sidelink HARQ feedback.

[0693] In one embodiment, the sidelink feedback transmission of the sidelink HARQ feedback (in the second feedback resource) is a PSFCH transmission (e.g., the sidelink feedback transmission is a PSFCH).

[0694] In one embodiment, the sidelink transmission is scheduled by a SCI (e.g., a SCI received by the first UE). The SCI provides a HARQ process number (e.g., a HARQ feedback process number) for the second UE used for the sidelink transmission. In an example, the sidelink transmission of the sidelink HARQ (in the second feedback resource) can be based on the HARQ process number indicated by the sidelink transmission. In an example, the sidelink HARQ feedback can be indicated (and / or based on) the HARQ process number indicated by the sidelink transmission.

[0695] In one embodiment, a first parameter in the sidelink resource pool indicates whether retransmission of sidelink HARQ feedback is supported (e.g., at least one of supported by the first UE, supported by the second UE, supported by the sidelink resource pool, etc.). For example, the first parameter can configure the first UE to: (i) support (and / or perform) retransmission of sidelink HARQ feedback, or (ii) not support (and / or not perform) retransmission of sidelink HARQ feedback. For example, if the first parameter is a first value, the first UE can be configured to (and / or allowed to) perform retransmission of sidelink HARQ feedback. Alternatively and / or additionally, if the first parameter is a second value, the first UE can be configured not to perform retransmission of sidelink HARQ feedback (and / or the first UE can not be allowed to perform retransmission of sidelink HARQ feedback).

[0696] In one embodiment, a second parameter associated with PC5 RRC signaling between the first UE and the second UE indicates whether retransmission of sidelink HARQ feedback is supported (e.g., at least one of supported by the first UE, supported by the second UE, supported by the sidelink resource pool, etc.). The PC5 RRC signaling can correspond to transmission of one or more PC5 RRC signals between the first UE and the second UE (e.g., the second parameter can be indicated by a signal of the one or more PC5 RRC signals). For example, the second parameter can configure the first UE to: (i) support (and / or perform) retransmission of sidelink HARQ feedback, or (ii) not support (and / or not perform) retransmission of sidelink HARQ feedback. For example, if the second parameter is a first value, the first UE can be configured to (and / or allowed to) perform retransmission of sidelink HARQ feedback. Alternatively and / or additionally, if the second parameter is a second value, the first UE can be configured not to perform retransmission of sidelink HARQ feedback (and / or the first UE can not be allowed to perform retransmission of sidelink HARQ feedback).

[0697] In one embodiment, the first UE determines whether to (i) retransmit sidelink HARQ feedback and / or (ii) perform sidelink feedback transmission of sidelink HARQ feedback in the second feedback resource based on the first parameter and / or the second parameter. In one instance, if the first parameter and / or the second parameter indicates that retransmission of sidelink HARQ feedback is supported (e.g., if the first parameter and / or the second parameter (i) indicates to the first UE that retransmission of sidelink HARQ feedback is supported and / or (ii) configures the first UE to support retransmission of sidelink HARQ feedback), the first UE does not retransmit sidelink HARQ feedback (and / or one or more other sidelink HARQ feedback), and / or the first UE does not perform sidelink feedback transmission of sidelink HARQ feedback in the second feedback resource.

[0698] In one embodiment, the first UE determines a CBR (e.g., a CBR associated with the channel). The CBR can be used to disable and / or enable retransmission of sidelink HARQ feedback. The first UE can determine whether to perform the sidelink feedback transmission of the sidelink HARQ feedback in the second feedback resource based on a comparison of the CBR to a threshold (e.g., based on whether the CBR is greater than the threshold). In some instances, the first UE can determine to perform the sidelink feedback transmission of the sidelink HARQ feedback in the second feedback resource based on the CBR not being greater than the threshold. Alternatively and / or additionally, the first UE can determine not to perform the sidelink feedback transmission of the sidelink HARQ feedback in the second feedback resource based on the CBR being greater than the threshold.

[0699] In one embodiment, the sidelink feedback transmission of the sidelink HARQ feedback in the second feedback resource corresponds to a retransmission of the sidelink HARQ feedback.

[0700] In one embodiment, a third parameter in the sidelink resource pool indicates whether the sidelink feedback transmission of the sidelink HARQ feedback in the second feedback resource is supported (e.g., at least one of supported by the first UE, supported by the second UE, supported by the sidelink resource pool, etc.). For example, the third parameter can configure the first UE to: (i) support (and / or perform) the sidelink feedback transmission of the sidelink HARQ feedback in the second feedback resource, or (ii) not support (and / or perform) the sidelink feedback transmission of the sidelink HARQ feedback in the second feedback resource. For example, if the third parameter is a first value, the first UE can be configured to (and / or allowed to) perform the sidelink feedback transmission of the sidelink HARQ feedback in the second feedback resource. Alternatively and / or additionally, if the third parameter is a second value, the first UE can be configured not to perform the sidelink feedback transmission of the sidelink HARQ feedback in the second feedback resource (and / or the first UE can not be allowed to perform the sidelink feedback transmission of the sidelink HARQ feedback in the second feedback resource).

[0701] In one embodiment, a fourth parameter associated with PC5 RRC signaling between the first UE and the second UE indicates whether sidelink feedback transmission of sidelink HARQ feedback in the second feedback resource is supported (e.g., at least one of supported by the first UE, supported by the second UE, supported by the sidelink resource pool, etc.). The PC5 RRC signaling can correspond to transmission of one or more PC5 RRC signals between the first UE and the second UE (e.g., the fourth parameter can be indicated by a signal of the one or more PC5 RRC signals). For example, the fourth parameter can configure the first UE to: (i) support (and / or perform) sidelink feedback transmission of sidelink HARQ feedback in the second feedback resource, or (ii) not support (and / or perform) sidelink feedback transmission of sidelink HARQ feedback in the second feedback resource. For example, if the fourth parameter is a first value, the first UE can be configured (and / or allowed) to perform sidelink feedback transmission of sidelink HARQ feedback in the second feedback resource. Alternatively and / or additionally, if the fourth parameter is a second value, the first UE can be configured not to perform sidelink feedback transmission of sidelink HARQ feedback in the second feedback resource (and / or the first UE can not be allowed to perform sidelink feedback transmission of sidelink HARQ feedback in the second feedback resource).

[0702] In one embodiment, a CBR (e.g., associated with the channel) is used to deactivate and / or activate sidelink feedback transmission of sidelink HARQ feedback in the second feedback resource. The first UE can determine whether to perform sidelink feedback transmission of sidelink HARQ feedback in the second feedback resource based on a comparison of the CBR to a threshold (e.g., based on whether the CBR is greater than the threshold). In some instances, the first UE can determine to perform sidelink feedback transmission of sidelink HARQ feedback in the second feedback resource based on the CBR not being greater than the threshold. Alternatively and / or additionally, the first UE can determine not to perform sidelink feedback transmission of sidelink HARQ feedback in the second feedback resource based on the CBR being greater than the threshold.

[0703] In one embodiment, the first UE performs sidelink feedback transmission of sidelink HARQ feedback in the second feedback resource in response to failing to access the channel for transmission of sidelink HARQ feedback in the first feedback resource.

[0704] In one embodiment, the first UE performs channel access for the second feedback resource in response to failing to access the channel for transmission of sidelink HARQ feedback in the first feedback resource.

[0705] Referring back to Figure 3 and 4In one example embodiment of the first UE, the apparatus 300 includes program code 312 stored in the memory 310. The CPU 308 can execute the program code 312 to enable the first UE to: (i) receive, in a first timing, a sidelink transmission from a second UE, wherein the sidelink transmission is associated with enabled sidelink HARQ feedback, (ii) attempt to access a channel for transmission of sidelink HARQ feedback in a first feedback resource, wherein the sidelink HARQ feedback is in response to the sidelink transmission, wherein the attempt to access the channel for transmission of sidelink HARQ feedback in the first feedback resource fails, and wherein the first feedback resource is in a second timing, (iii) perform channel access for a second feedback resource, wherein the second feedback resource is within a window and / or within a predefined duration of the first timing or the second timing, and wherein the channel access for the second feedback resource is successfully performed, and (iv) perform, in response to successfully performing the channel access for the second feedback resource, sidelink feedback transmission of the sidelink HARQ feedback to the second UE in the second feedback resource. In addition, the CPU 308 can execute the program code 312 to perform one, some and / or all of the above-mentioned actions and steps and / or other actions and steps described herein.

[0706] A communication apparatus (e.g., a UE, a base station, a network node, etc.) can be provided, where the communication apparatus can include a control circuit, a processor installed in the control circuit, and / or a memory installed in the control circuit and coupled to the processor. The processor can be configured to execute program code stored in the memory to perform the method steps described in Figures 8 to 14 In addition, the processor can execute the program code to perform one, some and / or all of the above-mentioned actions and steps and / or other actions and steps described herein.

[0707] A computer-readable medium can be provided. The computer-readable medium can be a non-transitory computer-readable medium. The computer-readable medium can include a flash memory device, a hard disk drive, a diskette, and / or a memory stick, among others. The computer-readable medium can include processor-executable instructions configured to cause, when executed, a processor to perform one, some and / or all of the method steps shown in Figures 8 to 14 In addition, the processor can execute the program code to perform one, some and / or all of the above-mentioned actions and steps and / or other actions and steps described herein.

[0708] It can be appreciated that one or more of the techniques presented herein can yield one or more benefits, including but not limited to increased efficiency of communications between apparatuses (e.g., UEs, such as UEs communicating in a sidelink). The increased efficiency can be such that UEs are enabled to communicate with one another in a sidelink via sidelink transmissions over an unlicensed spectrum (e.g., a wideband unlicensed spectrum), which can improve throughput. For example, for sidelink transmissions applied over an unlicensed spectrum that can need to coexist fairly with one or more other RATs and / or non-3GPP apparatuses, the techniques provided herein can be used to perform sidelink transmissions under regulation for the unlicensed spectrum. With sidelink transmissions over an unlicensed spectrum, benefits of a wideband unlicensed spectrum can improve throughput.

[0709] Various aspects of the disclosure have been described. It should be apparent that the teachings herein can be embodied in a wide variety of forms and that any specific structure, function, or both being disclosed herein is merely representative. Based on the teachings herein one skilled in the art should appreciate that an aspect disclosed herein can be implemented independently of any other aspects and that an aspect can be implemented both as any aspect described herein and as any combination of described aspects. For example, an apparatus can be implemented using any number of the aspects described herein. In addition, an apparatus can be implemented or a method can be practiced using other structure, functionality, or structure and functionality consistent with the teachings herein. As an example, in some aspects, parallel channels can be established based on a pulse repetition frequency. In some aspects, parallel channels can be established based on a pulse position or offset. In some aspects, parallel channels can be established based on a time hopping sequence. In some aspects, parallel channels can be established based on a pulse repetition frequency, a pulse position or offset, and a time hopping sequence.

[0710] Those skilled in the art will appreciate that information and signals can be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that can be referenced throughout the above description can be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0711] Those of skill would further appreciate that the various illustrative logical blocks, modules, processors, means, circuits, and algorithm steps described in connection with the aspects disclosed herein can be implemented as electronic hardware (e.g., a digital implementation, an analog implementation, or a combination of the two, which can be designed using source coding or some other technique), various forms of program or design code incorporating instructions (which can be referred to herein, for convenience, as "software" or a "software module"), or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality, without reference to a particular

[0712] In addition, various illustrative logical blocks, modules, and circuits described in connection with the aspects disclosed herein can be implemented within or performed by an integrated circuit ("IC"), an access terminal, or an access point. The IC can include 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, electrical components, optical components, mechanical components, or any combination thereof designed to perform the functions described herein, and can execute codes or instructions that reside within the IC, outside of the IC, or both. A general purpose processor can be a microprocessor, but in the alternative, the processor can be any conventional processor, controller, microcontroller, or state machine. A processor can also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0713] It should be understood that any particular order or hierarchy of steps in any disclosed process is an example of an illustrative approach. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the processes can be rearranged, while remaining within the scope of the present disclosure. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented.

[0714] The steps of a method or algorithm described in connection with the aspects disclosed herein can be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module (e.g., including executable instructions and related data) and other data can reside in a data memory such as RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of computer-readable storage medium known in the art. An example storage medium can be coupled to a machine (e.g., a computer processor, which for convenience is also referred to herein as a "processor") such that the processor can read information (e.g., code) from, and write information to, the storage medium. An example storage medium can be integral to the processor. The processor and the storage medium can reside in an ASIC. The ASIC can reside in a user device. In the alternative, the processor and the storage medium can reside as discrete components in a user device. Alternatively, and / or additionally, in some aspects any suitable computer-program product can comprise a computer-readable medium comprising code relating to one or more of the aspects of the present disclosure. In some aspects a computer program product can comprise packaging materials.

[0715] While the disclosed subject matter has been described in connection with various aspects, it will be understood that the disclosed subject matter is capable of further modifications. This application is intended to cover any variations, uses or adaptations of the disclosed subject matter including departures from the present disclosure that come within the scope of the disclosure to the patentable scope of the disclosed subject matter.

[0716] Cross Reference to Related Applications

[0717] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 319,047, filed March 11, 2022, the entire disclosure of which is incorporated herein by reference in its entirety. This application also claims the benefit of U.S. Provisional Patent Application No. 63 / 319,061, filed March 11, 2022, the entire disclosure of which is incorporated herein by reference in its entirety. This application also claims the benefit of U.S. Provisional Patent Application No. 63 / 319,074, filed March 11, 2022, the entire disclosure of which is incorporated herein by reference in its entirety.

Claims

1. A method for a first user equipment to perform sidelink communication in a sidelink resource pool, characterized in that, The method includes: Receive sidelink transmissions from a second user equipment, wherein the sidelink transmissions are associated with enabled sidelink hybrid automatic repeat request feedback; An attempt is made to access the channel for transmission of sidelink hybrid automatic repeat request feedback in the first feedback resource, wherein: The sidelink hybrid automatic repeat request feedback response is transmitted on the sidelink; and The attempt to access the channel for use in the sidelink hybrid automatic repeat request feedback in the first feedback resource failed; Perform channel access for the second feedback resource, wherein: The second feedback resource is within a window, wherein the window is associated with the retransmission of the sidelink hybrid automatic repeat request feedback after a transmission failure; and The channel access for the second feedback resource was successfully executed; and In response to the successful execution of the channel access for the second feedback resource, the sidelink feedback of the sidelink hybrid automatic repeat request feedback in the second feedback resource is transmitted to the second user equipment.

2. The method according to claim 1, characterized in that, At least one of the following exists: The first user equipment receives the side link transmission in the first timing sequence; The first feedback resource is in the second time sequence; The first user equipment executes the sidelink feedback transmission of the sidelink hybrid automatic repeat request feedback in the second feedback resource in the third timing sequence; The first timing sequence precedes the second timing sequence; or The second timing sequence precedes the third timing sequence.

3. The method according to claim 2, characterized in that, At least one of the following exists: The method includes determining the start of the window based on the first timing sequence or the second timing sequence; The duration of the window corresponds to a predefined value; The window is associated with the retransmission of the sidelink hybrid automatic repeat request feedback in the absence of receiving signals from the second user equipment; The window is associated with the retransmission of the sidelink hybrid automatic repeat request feedback without triggering resource selection; The window is different from the channel occupancy time; or The first user equipment performs the sidelink feedback transmission of the sidelink hybrid automatic repeat request feedback during the window.

4. The method according to claim 3, characterized in that, include: Whether to trigger resource selection for the sidelink feedback transmission of the sidelink hybrid automatic repeat request feedback is determined based on whether the third timing is during the window period, wherein the first user equipment determines, based on the third timing, to perform the sidelink feedback transmission of the sidelink hybrid automatic repeat request feedback without triggering resource selection during the window period.

5. The method according to claim 1, characterized in that, At least one of the following exists: The sidelink feedback transmission of the hybrid automatic repeat request feedback is performed using a physical sidelink feedback channel format associated with the delivery of multiple hybrid automatic repeat request feedbacks; or The sidelink feedback transmission of the hybrid automatic repeat request feedback is a physical sidelink feedback channel transmission.

6. The method according to claim 1, characterized in that: The sidelink transmission is scheduled by sidelink control information; and The sidelink control information provides the hybrid automatic repeat request process number for the second user equipment used for sidelink transmission.

7. The method according to claim 1, characterized in that, At least one of the following exists: The first parameter in the sidelink resource pool indicates whether the retransmission of the sidelink hybrid automatic repeat request feedback is supported; A second parameter associated with the PC5 radio resource control signaling between the first user equipment and the second user equipment indicates whether retransmission of the sidelink hybrid automatic repeat request feedback is supported; or The method includes determining whether to perform at least one of the following based on at least one of the first parameter or the second parameter: Retransmit the sidelink hybrid automatic repeat request feedback; or Perform the sidelink feedback transmission of the sidelink hybrid automatic repeat request feedback in the second feedback resource.

8. The method according to claim 7, characterized in that, include: Determine the channel busy ratio, wherein at least one of the following conditions is met: The channel busy ratio is used to disable or enable at least one of the retransmissions of the sidelink hybrid automatic repeat request feedback; The method includes determining whether to perform the sidelink feedback transmission of the sidelink hybrid automatic repeat request feedback in the second feedback resource based on a comparison of the channel busy ratio with a threshold; or The first user equipment determines to perform the sidelink feedback transmission of the sidelink hybrid automatic repeat request feedback in the second feedback resource based on the channel busy ratio not being greater than the threshold.

9. The method according to claim 1, characterized in that: The sidelink feedback transmission of the sidelink hybrid auto-repeat request feedback in the second feedback resource corresponds to the retransmission of the sidelink hybrid auto-repeat request feedback.

10. The method according to claim 1, characterized in that, At least one of the following exists: The first parameter in the sidelink resource pool indicates whether the sidelink feedback transmission in the second feedback resource is supported; or A second parameter associated with the PC5 radio resource control signaling between the first user equipment and the second user equipment indicates whether the sidelink feedback transmission of the sidelink hybrid automatic repeat request feedback in the second feedback resource is supported.

11. The method according to claim 10, characterized in that, include: Determine the channel busy ratio, wherein at least one of the following conditions is met: The channel busy ratio is used to disable or enable at least one of the sidelink feedback transmissions in the second feedback resource, namely the sidelink hybrid automatic repeat request feedback; The method includes determining whether to perform the sidelink feedback transmission of the sidelink hybrid automatic repeat request feedback in the second feedback resource based on a comparison of the channel busy ratio with a threshold; or The first user equipment determines to perform the sidelink feedback transmission of the sidelink hybrid automatic repeat request feedback in the second feedback resource based on the channel busy ratio not being greater than the threshold.

12. The method according to claim 1, characterized in that, At least one of the following exists: The first user equipment, in response to failing to access the channel for the transmission of the sidelink hybrid automatic repeat request feedback in the first feedback resource, performs the sidelink feedback transmission of the sidelink hybrid automatic repeat request feedback in the second feedback resource; or The first user equipment performs channel access for the second feedback resource in response to failure to access the channel for transmission of the sidelink hybrid automatic repeat request feedback in the first feedback resource.

13. A method for a first user equipment to perform sidelink communication in a sidelink resource pool, characterized in that, The method includes: In the first timing sequence, a sidelink transmission from a second user equipment is received, wherein the sidelink transmission is associated with an enabled sidelink hybrid automatic repeat request feedback; An attempt is made to access the channel for transmission of sidelink hybrid automatic repeat request feedback in the first feedback resource, wherein: The sidelink hybrid automatic repeat request feedback response is transmitted on the sidelink; The failure of the attempt to access the channel for the sidelink hybrid automatic repeat request feedback in the first feedback resource; and The first feedback resource is in the second time sequence; Perform channel access for the second feedback resource, wherein: The second feedback resource is within a predefined duration of either the first or second timing sequence, wherein the predefined duration is associated with the retransmission of the sidelink hybrid automatic repeat request feedback after a transmission failure; and The channel access for the second feedback resource was successfully executed; and In response to the successful execution of the channel access for the second feedback resource, the sidelink feedback of the sidelink hybrid automatic repeat request feedback in the second feedback resource is transmitted to the second user equipment.

14. The method according to claim 13, characterized in that, At least one of the following exists: The first user equipment performs the sidelink feedback transmission of the sidelink hybrid automatic repeat request feedback in the third time sequence; The first timing sequence precedes the second timing sequence; or The second timing sequence precedes the third timing sequence.

15. The method according to claim 13, characterized in that, At least one of the following exists: The predefined duration of the first timing sequence or the second timing sequence includes or refers to the predefined duration starting from the first timing sequence or the second timing sequence; or The predefined duration is associated with the retransmission of the sidelink hybrid automatic repeat request feedback without triggering resource selection; or The method includes determining whether to trigger resource selection for the sidelink feedback transmission of the sidelink hybrid automatic repeat request feedback based on whether the sidelink feedback transmission is within the predefined duration of the first timing or the second timing, wherein the first user equipment determines, based on whether the sidelink feedback transmission is within the predefined duration of the first timing or the second timing, to perform the sidelink feedback transmission of the sidelink hybrid automatic repeat request feedback without triggering resource selection.

16. The method according to claim 13, characterized in that, At least one of the following exists: The sidelink feedback transmission of the hybrid automatic repeat request feedback is performed using a physical sidelink feedback channel format associated with the delivery of multiple hybrid automatic repeat request feedbacks; or The sidelink feedback transmission of the hybrid automatic repeat request feedback is a physical sidelink feedback channel transmission.

17. The method according to claim 13, characterized in that, At least one of the following exists: The first parameter in the sidelink resource pool indicates whether the retransmission of the sidelink hybrid automatic repeat request feedback is supported; A second parameter associated with the PC5 radio resource control signaling between the first user equipment and the second user equipment indicates whether retransmission of the sidelink hybrid automatic repeat request feedback is supported; The third parameter in the sidelink resource pool indicates whether the sidelink feedback transmission of the sidelink hybrid automatic repeat request feedback in the second feedback resource is supported; A fourth parameter associated with the PC5 radio resource control signaling between the first user equipment and the second user equipment indicates whether the sidelink feedback transmission of the sidelink hybrid automatic repeat request feedback in the second feedback resource is supported; or The method includes determining whether to perform at least one of the following based on at least one of the first parameter, the second parameter, the third parameter, or the fourth parameter: Retransmit the sidelink hybrid automatic repeat request feedback; or Perform the sidelink feedback transmission of the sidelink hybrid automatic repeat request feedback in the second feedback resource.

18. The method according to claim 13, characterized in that, include: Determine the channel busy ratio, wherein at least one of the following conditions is met: The channel busy ratio is used to disable or enable the retransmission of the sidelink hybrid auto-repeat request feedback or the sidelink feedback transmission of the sidelink hybrid auto-repeat request feedback in the second feedback resource; The method includes determining whether to perform the sidelink feedback transmission of the sidelink hybrid automatic repeat request feedback in the second feedback resource based on a comparison of the channel busy ratio with a threshold; or The first user equipment determines to perform the sidelink feedback transmission of the sidelink hybrid automatic repeat request feedback in the second feedback resource based on the channel busy ratio not being greater than the threshold.

19. The method according to claim 13, characterized in that: The sidelink feedback transmission of the sidelink hybrid auto-repeat request feedback in the second feedback resource corresponds to the retransmission of the sidelink hybrid auto-repeat request feedback.

20. The method according to claim 13, characterized in that, At least one of the following exists: The first user equipment, in response to failing to access the channel for the transmission of the sidelink hybrid automatic repeat request feedback in the first feedback resource, performs the sidelink feedback transmission of the sidelink hybrid automatic repeat request feedback in the second feedback resource; or The first user equipment performs channel access for the second feedback resource in response to failure to access the channel for transmission of the sidelink hybrid automatic repeat request feedback in the first feedback resource.

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