Feedback Channel Mapping and HARQ Report Multiplexing in NR Sidelink Communications

Abstract

The present invention relates to the field of feedback channel mapping and HARQ report multiplexing in new radio sidelink (SL) communications. A method for operating a user equipment (UE) performing SL communications includes providing the UE with a procedure that enables the UE to determine Physical Sidelink Feedback Channel (PSFCH) resources / sequences for Hybrid Automatic Repeat Request (HARQ) reporting for the SL communications. The procedure provides instructions for determining PSFCH resources / sequences for HARQ reporting in a stepwise manner based on first and second characteristics for the SL communications.

Description

[Technical field]

[0001] The present invention relates to the field of Sidelink (SL) communications. In particular, the present invention relates to a method and apparatus for feedback channel mapping and HARQ report multiplexing in New Radio (NR) SL communications. [Background technology]

[0002] In the development of direct device-to-device (D2D) communication under the 3rd generation partnership project (3GPP), also referred to as sidelink (SL) technology, the reliability requirements for successful delivery of safety-related message packets over a direct wireless link, i.e., SL link, for advanced driving use cases are very high, e.g., up to 99.999%. To meet these stringent wireless reliability requirements, the next generation SL technology, which will be based on the latest 5G new radio (NR) standard, will incorporate hybrid automatic repeat request (HARQ) functionality, such as HARQ signaling, which will not only improve the reliability portion of the direct wireless link, but also reduce the latency portion of packet transmission block (TBs) delivery while minimizing the overall use of SL resources.

[0003] Acknowledgement signaling processes such as HARQ signaling are widely used in wireless communication technology (telecommunications) to keep error rates low when transferring data between a network node, such as a base station, and a user equipment (UE). Here, acknowledgement signaling should be used for SL communication even when transferring data directly between UEs without the interference of a network node. The acknowledgement signaling process may determine successful or erroneous reception of a packet TB via SL based on coded bits associated with the packet TB. The HARQ signaling may be referred to as HARQ feedback or HARQ feedback report, where the HARQ feedback report may be transmitted from one UE to another UE using SL communication. For HARQ signaling, a HARQ codebook may be used that associates a bit pattern to the acknowledgement signaling, for example by defining and / or indicating the bit pattern to be used for the acknowledgement signaling.

[0004] In case of D2D communication, this means that the HARQ feedback report may be performed by this UE (Rx-UE) receiving a packet TB transmitted from another UE (Tx-UE) to the Rx-UE. In other words, in case of D2D communication, the HARQ feedback report may be directly transmitted from the Rx-UE to the Tx-UE via the SL, where the HARQ feedback report includes feedback information, such as acknowledgement (ACK) information and / or negative acknowledgement (NACK) information, for the received packet TB. The ACK information in the HARQ feedback report may indicate to the Tx-UE that the corresponding packet TB has been successfully received and decoded by the Rx-UE, and the NACK information in the HARQ feedback report may indicate to the Tx-UE that the Rx-UE has not successfully received and / or decoded the corresponding packet TB. The reason for the failure to successfully receive and / or decode the packet TB may be, for example, that an error has occurred during packet TB transmission or during the encoding and / or decoding process.

[0005] When the Tx-UE receives a HARQ feedback report containing NACK information, the Tx-UE may retransmit each packet TB for which it received NACK information. By retransmitting each packet TB, the Rx-UE can successfully receive and decode the packet TB, thereby improving reliability.

[0006] In addition, by retransmitting only each packet TB for which the Tx-UE has received NACK information, and by not retransmitting packets TB for which the Tx-UE has received ACK information, the delay portion of packet TB delivery can be shortened and the overall usage of SL resources can be minimized.

[0007] However, it is expected that the new HARQ feedback reporting for D2D communication over SL may not be applicable or useful for all communication scenarios, i.e., HARQ reporting may be used only for three specific SL communication cast types, such as unicast (UC) for one-to-one direct communication, connectionless groupcast (CL-GC) with an unknown number of Rx-UEs in a short communication range that may communicate with each other using SL communication, and connection-oriented groupcast (CO-GC) with a fixed or determined number of Rx-UEs in an SL group that may communicate with each other using SL communication.

[0008] To facilitate feedback of HARQ reports, a new Physical Sidelink Feedback Channel (PSFCH) is introduced in the NR SL design for one or more Rx-UEs to feed back ACK and / or NACK results to the Tx-UE. Based on the expected usage for NR SL, where unicast and groupcast communications may not be the only and dominant transmission cast type, the periodicity (N) of PSFCH occurrences in terms of the number of time slots in the resource pool may be 0 (no PSFCH), 1, 2, or 4. It is also expected that due to UE processing capacity constraints, there may be a minimum time difference (K) between a Physical Sidelink Shared Channel (PSSCH) transmission, including the transmission of packet TBs, and its associated PSFCH for HARQ feedback. For example, the minimum time difference between PSSCH and PSFCH transmissions is 2 slots. This means that for the three specific SL communication cast types mentioned above, the shortest time that the Rx-UE may transmit its HARQ report after receiving packet TB during a PSSCH transmission from the Tx-UE is two slots.

[0009] FIG. 1 shows an example of HARQ reporting for PSSCH and PSFCH transmissions when N=1 and K=2. The frequency (Freq.) axis is vertical and the time axis is horizontal, the frequency axis includes subchannels, each consisting of, for example, 10 resource blocks (RBs), and the time axis includes a number of time slots. Within one time slot, there is one PSSCH slot and one PSFCH slot, within the PSSCH slot, some time resources are allocated for PSSCH transmission, and within the PSFCH slot, some time resources are allocated for PSFCH transmission. In addition, within one subchannel, some RBs are allocated for PSSCH transmission, and some RBs are allocated for PSFCH transmission. The HARQ reporting window (HRW) is shown with a dashed line. The size of the HRW is indicated by a parameter N, which in this example is set to 1 (N=1). This means that the HRW contains one PSSCH slot and the PSFCH slot carries a HARQ feedback report for one PSSCH slot, where the minimum time difference is K=2. Thus, the Rx-UE must wait two PSSCH slots after receiving a packet TB in a PSSCH slot in order to send a HARQ feedback report for this packet TB in the PSFCH slot. In Figure 1, the PSFCH time resources in a time slot and the RBs for PSFCH transmission are illustrated by a diamond pattern.

[0010] FIG. 2 shows another example of HARQ reporting for PSSCH and PSFCH transmissions when N=2 and K=2. The same scenario as in FIG. 1 is shown, except that the HRW is different. For N=2, the HRW includes two PSSCH slots, so the PSFCH slot carries HARQ feedback reports for two PSSCH slots. For example, for PSSCH transmissions in time slots (n-3) and (n-2), the corresponding PSFCH transmission opportunity for carrying the HARQ feedback report is time slot (n) to satisfy the constraint of K=2, i.e., to satisfy the minimum time difference of K=2. Thus, when N>1, multiplexing of HARQ feedback reports for multiple PSSCH transmission slots is necessary.

[0011] Figure 3 shows another example of HARQ reporting for PSSCH and PSFCH transmissions when N=4 and K=2. The same scenario as in Figures 1 and 2 is shown, except that the HRW is different. For N=4, the HRW includes four PSSCH slots, so the PSFCH slot carries HARQ feedback reports for four PSSCH slots. For example, for PSSCH transmissions in time slots (n-5), (n-4), (n-3), and (n-2), the corresponding PSFCH transmission opportunity for carrying the HARQ feedback report is time slot (n) to satisfy the constraint of K=2, i.e., to satisfy the minimum time difference of K=2. Again, multiplexing of HARQ feedback reports for multiple PSSCH transmission slots is required when N>1. Summary of the Invention

[0012] technical challenges As mentioned above, for NR SL communication between UEs, e.g., Tx-UE and Rx-UE, HARQ feedback reporting is newly introduced, where a new physical channel, PSFCH, is introduced for HARQ feedback reporting for PSSCH transmissions. As explained with respect to Figures 2 and 3, when N>1, HARQ feedback reporting needs to be multiplexed for multiple PSSCH transmission slots.

[0013] However, so far, no rules have been provided on how to determine the PSFCH resource within a subchannel for PSFCH transmission, and no rules have been defined on the mapping of PSFCH and ACK / NACK multiplexing.

[0014] Therefore, one of the main issues associated with PSFCH design is the multiplexing capability and resource capacity to accommodate HARQ reporting for SL transmissions of different cast types and for HARQ reporting for multiple slots and for multiple UEs per PSFCH transmission / slot.

[0015] Solution According to one aspect, a method for operating a user equipment (UE) performing sidelink (SL) communications includes providing a procedure for the UE to enable the UE to determine Physical Sidelink Feedback Channel (PSFCH) resources / sequences for Hybrid Automatic Repeat Request (HARQ) reporting for the SL communications, the procedure providing instructions for incrementally determining PSFCH resources / sequences for the HARQ reporting based on first and second characteristics for the SL communications.

[0016] According to another aspect, a user equipment (UE) includes a processor and a memory, the memory including instructions executable by the processor, whereby the UE is operated to provide a procedure to enable the UE to determine Physical Sidelink Feedback Channel (PSFCH) resources / sequences for Hybrid Automatic Repeat Request (HARQ) reporting for SL communication, the procedure providing instructions for incrementally determining PSFCH resources / sequences for HARQ reporting based on first and second characteristics for the SL communication. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 shows an example of HARQ reporting for PSSCH and PSFCH transmissions when N=1 and K=2. [Diagram 2] FIG. 2 shows another example of HARQ reporting for PSSCH and PSFCH transmissions when N=2 and K=2. [Diagram 3] FIG. 3 shows an example of HARQ reporting for PSSCH and PSFCH transmissions when N=4 and K=2. [Figure 4] FIG. 4 shows an example of a wireless communication network. [Diagram 5] FIG. 5 shows an exemplary configuration for a network node. [Figure 6] FIG. 6 illustrates an exemplary configuration for user equipment. [Figure 7] FIG. 7 illustrates a method for operating user equipment performing sidelink communication. [Figure 8] FIG. 8 illustrates a flow chart for stepwise decision instructions according to one embodiment. [Figure 9] FIG. 9 shows a configuration of PSSCH resources and PSFCH resources. [Figure 10] FIG. 10 shows the structure of one subchannel in the frequency domain. [Figure 11A] 11A and 11B show different embodiments regarding how the PSFCH resource blocks are allocated in a first step and how a pair / set of PSFCH resources is determined in a second step. [Figure 11B] 11A and 11B show different embodiments regarding how the PSFCH resource blocks are allocated in a first step and how a pair / set of PSFCH resources is determined in a second step. [Figure 12] FIG. 12 illustrates an exemplary PSSCH and PSFCH configuration in which multiple resource blocks in a PSFCH slot are divided into multiple regions according to one embodiment. [Figure 13] FIG. 13 illustrates an exemplary PSSCH and PSFCH configuration in which multiple resource blocks in a PSFCH slot are divided into multiple regions according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] One or more mechanisms described above and in more detail below address technical issues that arise with respect to the newly introduced PSFCH for NR SL communications.

[0019] As mentioned above, so far, no rules are provided on how to determine the PSFCH resource / sequence (PSFCH resource or PSFCH sequence) in the subchannel for PSFCH transmission. In addition, no rules are defined on the mapping of PSFCH and ACK / NACK multiplexing so far. Therefore, one of the main issues related to PSFCH design is the multiplexing ability and resource capacity to accommodate HARQ reports for SL transmissions of different cast types and for HARQ reports for multiple slots and multiple UEs per PSSCH transmission / slot.

[0020] A solution on how to determine PSFCH resources / sequences in subchannels for PSFCH transmission for SL communication is detailed below. For example, for feedback channel mapping and HARQ report multiplexing schemes for sidelink packet TB receiving UEs (Rx-UEs) sending ACK / NACK feedback to packet TB transmitting UEs (Tx-UEs), the objective is to solve the above-mentioned PSFCH capacity and multiplexing problems by adjusting the amount of PSFCH radio resources based on demand and by controlling slots in which transmission cast types with high ACK / NACK feedback amounts may be transmitted, where an increase in control signaling should be avoided. In addition, the objective is to efficiently utilize all PSFCH resources / sequences. To accommodate multiple HARQ reports for different PSFCH transmission slots on a limited set of resource blocks (RBs) for PSFCH from different UEs, a technique of cyclic shifting of PSFCH resources / sequences may be used.

[0021] In the following, any exemplary type of wireless communication network, such as a cellular wireless communication network, or the like, is of interest, and the communication network may include at least one network node and at least one user equipment (UE).

[0022] FIG. 4 illustrates an example of a wireless communication network 400 including a network node 410, a UE 420, and a UE 430. The network nodes and UEs may generally be considered as devices or nodes adapted for wireless and / or radio wave (and / or microwave) frequency communication and / or adapted for communication over an air interface, e.g., according to a communication standard. The network node 410 may be any type of network device or any type of wireless node of a wireless communication network, such as a base station, and / or an eNodeB (eNB), and / or a gNodeB (gNB), and / or a relay node, and / or a micro node or a nano node or a pico node or a femto node, and / or other nodes. The example wireless communication network 400 in FIG. 4 includes one network node and two UEs. However, this is not limiting, and the wireless communication network 400 may include more or fewer network nodes and more or fewer UEs.

[0023] The UEs 420 and 430 may represent end devices for communication using a wireless communication network and / or may be implemented as UEs according to a communication standard such as LTE, NR, or the like. Examples of UEs may include a phone such as a smartphone, a personal communication device, a mobile phone or a mobile terminal, a computer, particularly a laptop, a sensor or a machine with wireless capabilities (and / or adapted for an air interface), particularly MTC (machine type communication, sometimes also referred to as M2M or machine-to-machine), particularly D2D (device-to-device), particularly RSU (Road Side Unit), or a vehicle, particularly adapted for wireless communication. The UE or terminal may be mobile or fixed.

[0024] The network node 410 can transmit any kind of downlink (DL) data to the UEs 420 and 430 via the communication link 440, and the UEs 420 and 430 can transmit any kind of uplink (UL) data to the network node 410 via the communication link 440 (LTE, NR, or the like). Furthermore, the UEs 420 and 430 can exchange data directly between each other using sidelink (SL) signaling via the communication link 450 (Bluetooth, Wi-Fi, or the like). The SL communication is used to support direct communication between the UEs 420 and 430 without the interference of the network node 410. By using the SL communication, the UEs 420 and 430 may operate in several modes, such as D2D, MTC, etc.

[0025] D2D communication in combination with cellular networks offers the advantage of supporting both direct communication between UEs and traditional cellular network based communication, while providing a migration path to, for example, 5G based systems and services.

[0026] The resources allocated for SL may be obtained from the uplink (UL), i.e. from subframes on the UL frequency in Frequency Division Duplex (FDD) or Time Division Duplex (TDD). The UL or SL signaling may be Orthogonal Frequency Division Multiple Access (OFDMA) signaling or Single Carrier Frequency Division Multiple Access (SC-FDMA) signaling. The downlink signaling may in particular be OFDMA signaling. However, the signaling is not limited thereto.

[0027] Signaling may generally include one or more signals and / or one or more symbols. Control information, or control information messages, or corresponding signaling (control signaling) may be transmitted on a control channel, e.g., a physical control channel, which may be a downlink channel or a sidelink channel, possibly for example, where one UE schedules another UE. Acknowledgement signaling, e.g., as a form of HARQ feedback report, may be transmitted by the UE 420 or 430 to the network node 410 on a Physical Uplink Control Channel (PUCCH) and / or on a Physical Uplink Shared Channel (PUSCH) and / or on a HARQ dedicated channel. Also, acknowledgement signaling, e.g. in the form of a HARQ feedback report, may be transmitted by one of the UEs 420 and 430 to the other of the UEs 420 and 430 on a Physical Sidelink Feedback Channel (PSFCH). For example, if the UE 420 transmits a packet TB to the UE 430 via the SL 450 using a Physical Sidelink Shared Channel (PSSCH) transmission (UE 420 is also referred to as a transmitting UE (Tx-UE)), the UE 430 as a receiving UE (Rx-UE) may send a HARQ feedback report back to the UE 420, the HARQ feedback report including acknowledgement (ACK) or negative acknowledgement (NACK) information for the transmitted packet TB. The ACK information may indicate that the UE 430 was able to successfully receive and decode the corresponding packet TB, whereas the NACK information may indicate that the UE 430 was not able to successfully receive and / or decode the corresponding packet TB.When the UE 420 receives NACK information for a particular packet TB, the UE 420 may retransmit the particular packet TB so that the UE 430 can successfully receive and decode the packet TB, thereby improving the reliability of the transmission.

[0028] 5 illustrates an exemplary configuration of a network node 410. The network node 410 may include a processor 510 and a memory 520. The processor 510 may be a processing circuit (which may be referred to as a control circuit) that may include a controller connected to the memory 520. Any module of the network node 410, such as a communication module or a decision module, may be implemented in and / or executable by the processing circuit 510, particularly as a module in a controller. The network node 410 may also include radio circuitry (not shown) providing transmission / reception or transceiver functionality, such as one or more transmitters, and / or one or more receivers, and / or one or more transceivers, where the radio circuitry is connected or connectable to the processing circuitry 510. Antenna circuitry (not shown) of the network node 410 may be connected or connectable to radio circuitry for collecting or transmitting signals and / or amplifying signals. The network node 410 may be configured to implement any of the methods for operating a network node disclosed herein, and in particular the network node 410 may include corresponding circuitry, e.g., processing circuitry and / or modules.

[0029] FIG. 6 shows an exemplary configuration of the UE 430, where the UE is, for example, an Rx-UE. The configuration of the UE 420 is the same as that of the UE 430, and a detailed description of the configuration of the UE 420 is omitted here for the sake of brevity. The UE 430 may include a processor 610 and a memory 620. The processor 610 may be a processing circuit (which may be referred to as a control circuit) that may include a controller connected to the memory 620. Any module of the UE 430, for example, a communication module or a decision module, may be implemented in and / or executable by the processing circuit 610, particularly as a module in a controller. The UE 430 may also include radio circuitry (not shown) providing transmission / reception or transceiver functionality, e.g., one or more transmitters, and / or one or more receivers, and / or one or more transceivers, where the radio circuitry is connected or connectable to the processing circuitry 610. Antenna circuitry (not shown) of the UE 430 may be connected or connectable to the radio circuitry to collect or transmit signals and / or amplify signals. The UE 430 may be configured to implement any method for operating user equipment disclosed herein, and in particular, the UE 430 may include corresponding circuitry, e.g., processing circuitry and / or modules.

[0030] In general, computer program products are contemplated that include instructions that, when executed on, inter alia, processing and / or control circuitry, cause the processing and / or control circuitry to perform and / or control any of the methods described herein. Also contemplated are carrier medium configurations carrying and / or storing computer program products as described herein.

[0031] A carrier medium arrangement may include one or more carrier media. In general, the carrier medium may be accessible and / or readable and / or receivable by a processing or control circuit. Stored data and / or computer program products and / or code may be considered as part of the carried data and / or as part of the program product and / or as part of the code. The carrier medium may generally include a guiding or carrying medium and / or a storage medium. The guiding or carrying medium may be configured to carry and / or store signals, in particular electromagnetic signals, and / or electrical signals, and / or magnetic signals, and / or optical signals. The carrier medium, in particular the guiding or carrying medium, may be configured to guide such signals in order to carry such signals. The carrier medium, in particular the guiding or carrying medium, may include an electromagnetic field, for example radio waves or microwaves, and / or may optionally include an optically transparent material, for example fiberglass, and / or a cable. The storage medium may include at least one memory, which may be volatile or non-volatile, a buffer, a cache, an optical disk, a magnetic memory, a flash memory, and so on.

[0032] As mentioned above, so far, no rules have been defined on how to determine the PSFCH resource for PSFCH transmission, nor on PSFCH mapping and ACK / NACK multiplexing. Thus, to enable proper PSFCH resource determination, PSFCH mapping and ACK / NACK multiplexing, Fig. 7 shows a method for operating a UE performing SL communication, e.g., UE 420 or UE 430 performing SL communication.

[0033] As shown in Fig. 7, the method includes providing a UE with a procedure (S710) enabling the UE to determine a PSFCH resource / sequence for HARQ reporting for SL communication, where the procedure provides instructions for determining a PSFCH resource / sequence for HARQ reporting stepwise based on a first characteristic and a second characteristic for SL communication. The UE may be an Rx-UE that receives a packet TB from a Tx-UE via SL communication and is requested to perform HARQ reporting to the Tx-UE for the received packet TB. The procedure may include a set of rules enabling the UE to autonomously determine the PSFCH resource / sequence.

[0034] For example, the Rx-UE may be instructed by a Sidelink Control Information (SCI) format that schedules the SL communication, in particular the PSSCH reception, to transmit a HARQ report or a PSFCH with HARQ-ACK information in response to the SL communication. The Rx-UE may provide HARQ-ACK information or a HARQ report including an ACK or a NACK, or a HARQ report including only a NACK. The SCI format may include a HARQ feedback enable / disable indicator field, in which case a HARQ report or a PSFCH with HARQ-ACK information is transmitted by the Rx-UE in response to the SL communication, in particular the PSSCH reception, when the HARQ feedback enable / disable indicator has a particular value. For example, if an Rx-UE receives a PSSCH in a resource pool and the HARQ feedback enable / disable indicator field in the associated SCI format, e.g., in SCI format 2-A or 2-B, has value 1, the Rx-UE provides HARQ-ACK information or a HARQ report in a PSFCH transmission in the resource pool.

[0035] Determination or autonomous determination of PSFCH resource / sequence may mean that the UE may determine the PSFCH resource / sequence without receiving control signaling or configuration information from a network node, such as a base station, or from another UE. The UE can determine the PSFCH resource / sequence only by considering the characteristics of the SL communication. Thus, by defining implicit rules for PSFCH mapping and ACK / NACK multiplexing, the need for the Tx-UE or Rx-UE to indicate or inform other UEs in control signaling of the exact location and PSFCH resource / sequence to use for feeding back HARQ reports is eliminated. Thus, the amount of control signaling overhead can be reduced.

[0036] 8 illustrates a flow chart for a stepwise decision instruction according to one embodiment. The stepwise decision instruction may include, as a first step, allocating 810 a PSFCH RB from among a set of RBs based on a first characteristic related to SL communication.

[0037] The instruction for stepwise determination may further include, as a second step, determining a pair / set of multiple PSFCH resources in the assigned PSFCH RB based on a second characteristic related to SL communication (S820), and as a third step, selecting a PSFCH resource / sequence (PSFCH resource or PSFCH sequence) for HARQ reporting from the pair / set of multiple PSFCH resources / sequences based on an ACK decoding result or a NACK decoding result of a PSSCH packet TB received during SL communication (S830). The PSSCH packet TB may be a packet TB transmitted from the Tx-UE to the Rx-UE during a PSSCH slot using SL communication. The ACK decoding result and the NACK decoding result may indicate whether the Rx-UE has successfully received and decoded the PSSCH packet TB. If the Rx-UE can successfully receive and decode the PSSCH packet TB, the PSFCH resource / sequence is selected based on the ACK decoding result. If the Rx-UE cannot receive and / or decode the PSSCH packet TB successfully, the PSFCH resource / sequence is selected based on the NACK decoding result. In other words, a pair / set of PSFCH resources / sequences in an assigned PSFCH RB may refer to one PSFCH resource / sequence assigned for the ACK decoding result and another PSFCH resource / sequence assigned for the NACK decoding result. There may be a set of PSFCH resources with a cyclic shift of 6.

[0038] According to another embodiment, the method for operating a UE may further include transmitting an ACK or NACK decoding result for the HARQ report using the selected PSFCH resource / sequence.

[0039] For example, the UE, as Rx-UE, receives at least one PSSCH packet TB from a further UE, i.e. Tx-UE, via SL communication, where the Rx-UE is requested by the Tx-UE to provide a HARQ report comprising an ACK and / or NACK feedback for the at least one PSSCH packet TB. As mentioned above, the Rx-UE may select a PSFCH resource / sequence for transmitting a HARQ report based on the characteristics of the SL communication, the HARQ report comprising an ACK and / or NACK decoding result for the at least one PSSCH packet TB. Depending on a HARQ reporting window (HRW) indicated by a parameter N, the HARQ report transmitted in one PSFCH slot may comprise an ACK and / or NACK decoding result of a packet TB transmitted in N PSSCH slots. Thus, the HRW, in particular the parameter N of the HRW, indicates the number of PSSCH slots to be reported in the HARQ report transmitted in a PSFCH slot. The Rx-UE may transmit the ACK and / or NACK decoding results using a HARQ report to the Tx-UE for feedback of an acknowledgement for the received one or more PSSCH packets TB.

[0040] FIG. 9 shows the configuration of PSSCH resources and PSFCH resources. In this case, as described with reference to FIG. 1 to FIG. 3, the frequency axis is vertical, and a large number of subchannels having 10 RBs are arranged in the frequency direction, and the time axis is horizontal, and a large number of time slots are arranged in the time direction. In each time slot, for example, in (n-3), (n-2), (n-1), and (n), there is one PSSCH slot and one PSFCH slot, and in the PSSCH slot, some time resources and frequency resources are allocated for PSSCH transmission, and in the PSFCH slot, some time resources and frequency resources are allocated for PSFCH transmission. Here, the HRW is again shown with a dashed line, and N=1. This means that the HRW includes one PSSCH slot, and the PSFCH slot accompanies a HARQ feedback report for one PSSCH slot. The minimum time difference is K=2, which means that Rx-UE must wait two PSSCH slots after receiving packet TB in a PSSCH slot in order to send a HARQ feedback report for this packet in the PSFCH slot. In Fig. 9, the PSFCH time resources in a time slot and RBs as frequency resources for PSFCH transmission are illustrated by a diamond pattern. The time and frequency resources illustrated by downward diagonal lines in Fig. 9 are used for purposes other than PSFCH transmission, not specified further.

[0041] 9 further illustrates the RBs for one PSFCH slot. One PSFCH slot may be for one or two PSFCH symbols, with multiple RBs used for one symbol. When a subchannel includes, for example, 10 RBs, one PSFCH slot may include 10 RBs or fewer RBs, depending on how many RBs in one time slot are used for purposes other than PSFCH transmission, not specified further.

[0042] As mentioned above, the PSFCH RB is allocated from a set of RBs to select a PSFCH resource / sequence within the PSFCH RB. According to an embodiment, the set of RBs may be configured for PSFCH transmission / reception and may be represented as a bitmap. For example, referring again to FIG. 9, the PSFCH RB is determined only from the RBs configured for PSFCH transmission / reception, not from all RBs in the subchannel, i.e., the RBs are indicated by a diamond pattern. The network node may, for example, pre-configure the set of RBs in the subchannel and may send configuration information to the UE for configuring the set of RBs in the subchannel.

[0043] According to one embodiment, the set of RBs may be configured using a SL resource pool configuration or using a SL resource pool pre-configuration, where the SL resource pool configuration or the SL resource pool pre-configuration includes PSFCH resource allocation and HARQ reporting related information. In particular, the SL resource pool configuration may include at least one PSFCH parameter related to time domain allocation, frequency domain allocation, cyclic shift allocation, and / or information regarding connection-oriented groupcast slot allocation. The UE may receive the SL resource pool configuration from a network node, for example using downlink data, or from a pre-configuration. The SL resource pool pre-configuration may be pre-configured in the UE without the UE needing to explicitly receive a configuration from a network node.

[0044] For example, in case of multiplexing of PSFCH mapping and HARQ report in NR SL communication from a first transmitting UE (Tx-UE) transmitting a packet TB via a PSSCH to at least one second UE (Rx-UE) receiving the packet TB, both UEs receive SL resource pool configuration details from either a network configuration or a pre-configuration including PSFCH resources / sequences, as well as HARQ report related information. In addition to the time domain periodicity (N) of occurrence of PSFCH resources in the resource pool and the minimum time difference (K) between a PSSCH transmission and its associated PSFCH for HARQ reporting, the (pre-)configuration information may additionally include one or more of a PSFCH symbol number parameter, a PSFCH starting symbol parameter, an RB allocation parameter, a cyclic shift pair or offset index parameter, and a connection-oriented groupcast slot parameter.

[0045] Thus, the (a priori) configuration information, i.e. the SL resource pool (a priori) configuration information, may include PSFCH parameters related to time domain allocation including a PSFCH symbol number parameter, a PSFCH starting symbol parameter, a periodicity of PSFCH resources in the resource pool and / or a minimum time difference (K), PSFCH parameters related to frequency domain allocation including a PSFCH RB allocation parameter, cyclic shift allocation including a cyclic shift pair or offset index parameter, and / or parameters related to connection-oriented groupcast slot allocation.

[0046] The number of PSFCH symbols parameter may be value 1 or value 2 and may indicate the number of PSFCH symbols in a slot. In particular, the number of PSFCH symbols parameter may define one or two symbols allocated for PSFCH towards the end of the time slot for the Rx-UE to transmit its HARQ report. As can be seen exemplarily in FIG. 9, one or two symbols are allocated towards the end of each time slot (n-3), (n-2), (n-1) and (n). FIG. 10 further illustrates an exemplary configuration of one subchannel, e.g., the exemplary configuration of one subchannel already illustrated in FIG. 9. With reference to FIG. 10, the slot structure for (pre)configured PSFCH resources towards the end of the slot is in the frequency direction, and the last symbol of the time slot is kept empty as a gap symbol (202) for Tx / Rx switching purposes and / or for sidelink / uplink switching purposes. FIG. 10 also illustrates one or two symbols (201), which define the number of PSFCH symbols parameter.

[0047] The PSFCH start symbol parameter may indicate a symbol index in a time slot to which one or more PSFCH symbols are assigned. For example, if there are 14 symbols in a slot, the symbol index may be 0-13. If this parameter is (pre-)configured, both Rx-UE and Tx-UE follow this parameter to transmit and receive PSFCH, respectively. When this parameter is not (pre-)configured, the start symbol for PSFCH will be determined based on the number of PSFCH symbols. For example, assume that there are 14 symbols in one time slot, and the last symbol is always designated as a gap symbol (see gap symbol (202) in FIG. 10) for Tx / Rx switching and / or sidelink / uplink switching. If the number of PSFCH symbols is determined to be two symbols, either (pre-)configured or predefined / fixed, the start symbol in this case will be the 12th symbol (symbol index 11) in the time slot, where the 14th symbol (symbol index 13) is the gap symbol. If only one symbol is allocated for the PSFCH, then the start symbol will be the 13th symbol in the slot (symbol index 12) and again the 14th symbol (symbol index 13) will be the gap symbol.

[0048] Additionally, when the SL resource pool configuration includes a PSFCH symbol number parameter as described above, the PSFCH symbol number parameter indicates the number of PSFCH symbols in the slot, and when the PSFCH symbol number parameter indicates two PSFCH symbols allocated for the PSFCH in the slot, the feedback information is coded and mapped in one symbol and duplicated to the previous symbol. In other words, when two Orthogonal Frequency Division Multiplexing (OFDM) symbols are allocated for the PSFCH, the PSFCH resource / sequence is mapped in one symbol and then duplicated to the previous symbol. This process of copying or duplicating the feedback information to the other symbol is illustrated in FIG. 10 by an arrow with a reference number (203). This means that the transmission signal from the Rx-UE is the same in both symbols when the two symbols are combined, for the purpose of automatic gain control (AGC) and / or reliability improvement in the Tx-UE.

[0049] The granularity of resource allocation for PSFCH may be one RB, and the allocation of PSFCH RBs in a subchannel does not have to be the same as the number of RBs in the subchannel. This is also shown in Figures 9 and 10, where some RBs are used for PSFCH transmission and some other RBs are used for purposes other than PSFCH transmission, and the RBs used for other purposes are indicated by downward diagonal lines. Thus, the RB allocation parameters may define the exact RB or RBs location for PSFCH transmission in the resource pool, where the RB allocation parameters may be represented as a bitmap. As shown in Figure 10, the RBs (204) configured for PSFCH transmission may be allocated contiguously (as illustrated for case (206) in Figure 10) or non-contiguously (as illustrated for case (207) in Figure 10) in the frequency domain (see the RBs indicated by downward diagonal lines in contrast to the RBs used for PSFCH transmission indicated by the diamond pattern) for the purpose of transmitting also other possible signals or channels (205) not used for PSFCH transmission. For example, RBs (205) in a PSFCH symbol that are not allocated for PSFCH transmission may be allocated for transmitting a channel state information reference signal (CSI-RS) in a localized and / or wideband manner depending on the subchannel size, depending on a positioning reference signal (PRS) for positioning and ranging purposes, and / or depending on other PSFCH formats that may be introduced later for future compatibility.

[0050] The cyclic shift pair or cyclic shift offset index parameter may be a value between 1 and 6 or between 0 and 11, respectively. The cyclic shift pair may set the number of pairs of cyclic shift positions or sequences in the PSFCH RB that may be used for HARQ reporting. The cyclic shift offset index may set the initial cyclic shift sequence position or offset to cyclic shift position zero of the HARQ sequence or PSFCH resource in the PSFCH RB that the Rx-UE should use to indicate the ACK or NACK decoding result. When the periodicity (N) of the PSFCH occurrences in the resource pool is greater than 1 (e.g., 2 or 4), the actual initial cyclic shift position to be used for mapping the ACK / NACK information may be further offset based on the PSSCH slot position in the HRW in which one or more packets TB were received.

[0051] The parameters related to the connection-oriented groupcast slot allocation may indicate one or more PSSCH slot positions where the connection-oriented groupcast TB may be transmitted in the HRW. The connection-oriented groupcast TB may be transmitted in a groupcast session where all UEs in the same SL group have knowledge of the group size of the SL group. The UEs in the SL group may be able to communicate with each other using SL communication. This means that all UEs in the same SL group may know other UEs in the same SL group and may communicate with them using SL communication. The parameters related to the connection-oriented groupcast slot allocation may be represented using a bitmap with a size equal to the number of PSSCH slots in the HRW. That is, the bitmap size may be 2 bits when N=2 and 4 bits when N=4.

[0052] As described above in Fig. 8, the instruction for determining the PSFCH resource / sequence for the HARQ report stepwise by the UE, e.g., by the Rx-UE, which has received the packet TB and is requested to feed back the HARQ report to the Tx-UE, includes as a first step, allocating the PSFCH RB from among a set of RBs based on a first characteristic for SL communication (S810), and as a second step, determining a pair / set of PSFCH resources in the allocated PSFCH RB based on a second characteristic for SL communication (S820). Here, Figs. 11A and 11B show different embodiments regarding how the PSFCH RB can be allocated in the first step and how the pair / set of PSFCH resources can be determined in the second step. In other words, Figs. 11A and 11B show additional steps that the first step and the second step may include. The third step described above with reference to FIG. 8 can still be performed thereafter.

[0053] First, the flowchart according to one embodiment shown in FIG. 11A will be described in detail below.

[0054] To allocate a PSFCH RB from the set of RBs, at least one PSFCH RB from the set of RBs is allocated into a subchannel (S811a), and the at least one PSFCH RB in the subchannel may be divided or separated into multiple regions of RBs based on the number of PSSCH slots associated with the PSFCH slot or based on the number of PSSCH slots in the HRW, with each region including at least one RB (S812a). Thus, the at least one PSFCH RB in the subchannel may be divided into multiple regions based on the parameter N of the HRW. When only a PSFCH RB is allocated from the RBs configured for PSFCH transmission, the RBs configured for PSFCH transmission may be divided into multiple regions based on the parameter N of the HRW.

[0055] For example, a band used for sidelink communication is divided into subchannels in the frequency domain, and a subchannel is a group of RBs. As illustrated with respect to Figures 1, 2, 3, 9, and 10, a subchannel may include 10 RBs, and the RBs are used for PSSCH and PSFCH transmissions. An RB may include multiple resource elements per RB, for example 12 resource elements. However, a subchannel may also include more or fewer RBs based on the subchannel configuration. The PSFCH RBs may be RBs used for PSFCH transmissions, and in particular, RBs used for HARQ reporting in a PSFCH slot.

[0056] FIG. 12 shows an exemplary PSSCH and PSFCH configuration in which RBs in a PSFCH slot are divided into regions of RBs according to one embodiment. In FIG. 12, N=4, i.e., the HRW (305) includes four PSSCH slots, and one PSFCH slot carries HARQ reports for up to four PSSCH slots. Thus, the RBs in a subchannel, here the RBs configured for PSFCH transmission in a subchannel, are separated or divided into four regions of RBs, see first region (301), second region (302), third region (303), and fourth region (304). Thus, the separation or division of the regions in this embodiment is based on the number of PSSCH slots in the HRW (305). As another example, if N=1, i.e. there is one PSSCH slot in the HRW, i.e. one PSFCH slot carries a HARQ report for one PSSCH slot, then only one region is needed.

[0057] Each region may include at least one RB. For example, when the total number of RBs in a subchannel is small, each region may include only a few RBs. However, when the total number of RBs in a subchannel is large, each region may include multiple RBs. For example, if a subchannel has a total of 20 PSFCH RBs and a HARQ report needs to be attached for a maximum of 4 PSSCH slots, i.e., N=4, 5 RBs may be allocated equally to each region, for example, the first region (301), the second region (302), the third region (303), and the fourth region (304) as shown in FIG. 12. If it is assumed that each RB can simultaneously carry 12 different PSFCH resources / sequences based on 12 resource elements per RB, and furthermore that each Rx-UE is assigned with 4 resources to represent all possible ACK / NACK combinations for two PSSCH packets TB, then each RB can multiplex HARQ reports for 3 Rx-UEs. This means that the RBs for each region can simultaneously accommodate up to 15 Rx-UEs. The size between the regions in terms of the number of RBs does not necessarily have to be the same, or the total number of RBs per subchannel needs to be evenly distributed across the regions of RBs.

[0058] Furthermore, as shown in FIG. 11A, a region may be selected from among the multiple regions of RBs obtained in S812a based on the slot position at which the corresponding PSSCH was received (S813a). Thus, when N>1, for example, when N=2 or N=4, the RBs in the subchannel are divided into multiple regions of RB>1 (when N=2, it is divided into two regions of RBs, and when N=4, it is divided into four regions of RBs). Here, to select a region from the multiple regions of RBs, the Rx-UE uses the slot position at which the corresponding PSSCH was received. For example, the Rx-UE uses the slot position at which one or more PSSCH packets TB were transmitted, i.e., one or more packets TB transmitted into one or more PSSCH slots were transmitted. In the exemplary configuration shown in FIG. 12, the Rx-UE selects a first region (301) from among the multiple regions of RBs if one or more PSSCH TBs are received in time slot (n-5), selects a second region (302) from among the multiple regions of RBs if one or more PSSCH TBs are received in time slot (n-4), selects a third region (303) from among the multiple regions of RBs if one or more PSSCH TBs are received in time slot (n-3), and selects a fourth region (304) from among the multiple regions of RBs if one or more PSSCH TBs are received in time slot (n-2).

[0059] Then, as shown in Fig. 11A, a PSFCH RB may be selected in the region selected in S813a based on a first characteristic for SL communication (S814a). Then, as shown in S820 of Fig. 8, a pair of PSFCH resources may be selected in the selected region based on a second characteristic for SL communication to determine a pair of PSFCH resources in the PSFCH RB (S821a). The pair of PSFCH resources may be a pair of cyclic shift sequences in the PSFCH RB. After step S821a of Fig. 12, step S830 described with reference to Fig. 8 may be performed.

[0060] The first characteristic related to the SL communication may include at least one of an SL transmission cast type, a member identifier (member ID or member_ID) of the groupcast communication, and a number of PSSCH TBs received during the SL communication.

[0061] According to another embodiment, the first characteristic related to SL communication may include a member ID for groupcast communication, where the member_ID, when available, is used to determine the PSFCH RB within the selected region.

[0062] The second property for SL communication may include at least a (pre-)configured cyclic shift assignment and / or a source identifier (source_ID). For example, the Rx-UE derives a pair / set of PSFCH resources in the PSFCH RB by using a (pre-)configured cyclic shift pair or offset index and / or by using the source_ID of the Tx-UE, in which case a PSFCH resource / sequence from the pair / set of PSFCH resources may be used to transmit the HARQ report.

[0063] The use of the Tx-UE's source_ID in the pair / set of PSFCH resources selection is intended to solve the hidden node problem in SL communication where one Tx-UE is far away from another Tx-UE and both transmit their PSSCH packets TB to the Rx-UE using the same PSSCH slot and subchannel.

[0064] Finally, based on the ACK and / or NACK decoding results for the received one or more PSSCH packets TB, the Rx-UE may select a final PSFCH resource / sequence for representing the HARQ report including the ACK and / or NACK information.

[0065] For example, if a Rx-UE in a groupcast communication, such as a connection-oriented groupcast, is assigned member_ID=10 and receives a PSSCH packet TB in the second PSSCH slot in an HRW of N=4 (as in FIG. 12), the Rx-UE may first select a second region for sending its HARQ report to the Tx-UE thereafter. Since the Tx-UE has only sent one PSSCH packet TB to the Rx-UE and there are 12 PSFCH resources per RB, and up to 6 pairs of ACK / NACK reports are multiplexed, the Rx-UE determines its position to be 10-6=4 in the second RB in the second region. Here, the position refers to the index of a pair of PSFCH resources (cyclic shift sequences) in the PSFCH RB. As mentioned above, there may be 12 PSFCH resources / cyclic shift sequences for multiplexing up to 6 pairs of ACK or NACK results in the PSFCH RB. When the member_ID is 10 and there are a total of 6 pairs in the PSFCH RB, the "pair" index that the Rx-UE should use to send the ACK / NACK report is 10-6=4th pair or position. This can be compared to the mathematical modulo ("mod") operation used in some 3GPP specifications (see, for example, 3GPP TS 36.213 Version 15.10.0, page 499, Table 16.4.1.3-4, Table 16.4.1.3-6, Table 16.4.1.3-8, pages 529 and 531, or 3GPP TS 38.213 Version 15.7.0, pages 49, 57, and 78). If it is assumed that the cyclic shift offset index is (pre-)configured to be zero for this resource pool, then the first pair index in the RB should use PSFCH resource / sequence 0 for ACK information and PSFCH resource / sequence 6 for NACK information.Since Rx-UE is the fourth in the second RB of the second region, it can be derived that PSFCH resource 3 should be used for feeding back ACK information such as an ACK bitmap, and that PSFCH resource 9 should be used for NACK information such as a NACK bitmap.

[0066] As another example, if an Rx-UE has a SL unicast communication session with only one Tx-UE and one Rx-UE in a group, the first RB in the region may always be used by the Rx-UE to feed back its HARQ report to the Tx-UE. Then, a (pre-)configured cyclic shift pair or offset index and / or source_ID of the Tx-UE may determine a pair / set of PSFCH resources in the RB, in which case a PSFCH resource / sequence from the pair / set of PSFCH resources / sequences may be used for ACK and NACK reporting.

[0067] The flowchart shown in FIG. 11B will now be described in detail.

[0068] According to another embodiment, to allocate a PSFCH RB from a set of RBs, at least one PSFCH RB from the set of RBs is allocated into a subchannel (811b), and the at least one PSFCH RB in the subchannel may be divided into multiple regions of RBs based on a SL transmission cast type (not based on the number of PSSCH slots associated with a PSFCH slot, nor based on the number of PSSCH slots in an HRW, as described with respect to FIG. 11A) (S812b), with each region including at least one RB.

[0069] For example, the SL transmission cast types include unicast (UC), connectionless groupcast (CL-GC), and connection-oriented groupcast (CO-GC) for one-to-one direct communication. In this regard, at least one PSFCH RB in a subchannel, e.g., a plurality of RBs in a subchannel configured for PSFCH transmission, may be divided into a first region, a second region, and a third region, where the first region is allocated for HARQ reporting of UC, the second region is allocated for HARQ reporting of CL-GC (SL groupcast communication in which all UEs in the same SL group do not know the size of the SL group), and the third region is allocated for HARQ reporting of CO-GC (groupcast communication in which all UEs in the same SL group have knowledge of the SL group size). UEs in an SL group may be able to communicate with each other using SL communication.

[0070] In the case of N=1, as in the previous scenario, there is only one PSSCH slot in one HRW, so the total number of PSFCH RBs in the subchannel does not need to be separated or divided into different regions. Therefore, all RBs allocated for PSFCH transmission in the subchannel may be used for HARQ reports from one or more Rx-UEs. Depending on the cast type of one or more PSSCH TBs transmitted in a slot in the HRW, for a unicast session, only one Rx-UE can feed back its ACK / NACK decoding result in a HARQ report in the PSFCH in the subchannel, or for groupcast communication, multiple Rx-UEs can feed back their HARQ report by sharing RBs and PSFCH resources / sequences.

[0071] In the case of N>1, e.g., in the case of N=2 or N=4, three separate regions may be defined for HARQ reporting for different SL transmission cast types, i.e., unicast, connectionless groupcast, and connection-oriented groupcast, as described above. This is also illustrated in FIG. 13, which shows an exemplary PSSCH and PSFCH configuration in which RBs in a PSFCH slot are divided into regions according to another embodiment. Here, the RBs in a PSFCH slot are divided into three regions based on the SL transmission cast type. The size between each region in terms of the number of RBs does not necessarily have to be the same, or the total number of RBs per subchannel does not have to be distributed evenly between the regions. This can be seen from FIG. 13, where the first region (401) and the second region (402) each include one PSFCH RB, and the third region (403) includes multiple PSFCH RBs.

[0072] In particular, referring to FIG. 13, the PSFCH RBs in the subchannel are divided into three separate regions for three different SL transmission cast types: unicast, connectionless groupcast, and connection-oriented groupcast. For the first two regions (401) and (402), PSFCH RBs may be allocated for the purpose of feedbacking ACK / NACK results of unicast and connectionless groupcast, and the order of allocation of PSFCH RBs is not important. It should be noted that each region is allocated for only one SL transmission cast type (either unicast or connectionless groupcast), and each region may be allocated at least one PSFCH RB. In FIG. 13, each of the first two regions (401) and (402) is allocated with only one PSFCH RB, and one of the regions is used for unicast HARQ reporting and the other region is used for connectionless groupcast HARQ reporting. However, for N=4, each of the first two regions (401) and (402) may include four PSFCH RBs. If N=2, each region may include two PSFCH RBs. For the third region (403), a PSFCH RB is allocated for feeding back the connection-oriented groupcast ACK result / NACK result. The third region (403) may include all remaining RBs not allocated to the first and second regions for PSFCH transmission in the subchannel.

[0073] When there is only one PSFCH RB allocated for a region or cast type, HARQ reports of the same cast type from all PSSCH slots in the HRW (408), e.g., from PSSCH slots (404), (405), (406), and (407), are multiplexed in that PSFCH RB. For example, if all four PSSCH slots contain unicast transmissions and all four PSSCH slots require HARQ reports from their Rx-UEs, then the four HARQ reports may be multiplexed in the same PSFCH RB, e.g., in region (401) or (402).

[0074] Furthermore, as shown in FIG. 11B, an area may be selected from among multiple areas consisting of RBs acquired in S812b based on the SL transmission cast type of the received PSSCH (S813b). For example, if the SL transmission cast type of the received PSSCH is unicast, a first area is selected from among multiple areas consisting of RBs. For example, if the SL transmission cast type of the received PSSCH is connectionless groupcast, a second area is selected from among multiple areas consisting of RBs. And, for example, if the SL transmission cast type of the received PSSCH is connection-oriented groupcast, a third area is selected from among multiple areas consisting of RBs.

[0075] Then, within the selected region, a PSFCH RB may be selected based on a first characteristic related to SL communication (S814b), and a pair / set of PSFCH resources may be determined within the selected region based on a second characteristic related to SL communication (S821b). After step S821b illustrated in FIG. 11B, step S830 of FIG. 8 may be performed.

[0076] According to an embodiment, the region may be further divided into a plurality of sub-regions based on the number of PSSCH slots associated with the PSFCH slot or based on the number of PSSCH slots in the HRW, with each sub-region including at least one RB. A sub-region may be selected from among the plurality of sub-regions based on the slot position at which the PSSCH is received during SL communication. A PSFCH RB may then be selected within the selected sub-region based on a first characteristic related to SL communication. A pair / set of a plurality of PSFCH resources / sequences may then be selected within the selected PSFCH RB based on a second characteristic related to SL communication. However, if the region includes only one RB, such as in the case of the first region (401) and the second region (402) illustrated in FIG. 13, the region will not be divided into a plurality of sub-regions.

[0077] Again, as described above, the first characteristic for SL communication may include at least one of a member identifier (member ID or member_ID) for groupcast communication and the number of transmitted PSFCH packets TBs. For example, when the member_ID for groupcast communication is available, the member_ID is used to select the PSFCH RB.

[0078] Additionally, the second characteristic for the SL communication may include at least a configured cyclic shift pair or offset index and / or a source identifier (source ID or source_ID).

[0079] In this case, a combination of a (pre)configured cyclic shift allocation, e.g., a cyclic shift pair or offset index, and a PSSCH slot position in the HRW may determine the exact pair / set of PSFCH resources / sequences to be used by each Rx-UE in the RB. If the hidden node problem needs to be solved, the source_ID of the Tx-UE may also be considered. When the HRW includes two PSSCH slots (when N=2), two RBs may be allocated for one region or one cast type. When the HRW includes four PSSCH slots (when N=4), four RBs may be allocated for one region or one cast type. In such a case, the HARQ report may be separated into different RBs based on the PSSCH slot position at which one or more TBs are received. In the case of FIG. 13, since each of the first and second regions includes only one RB, the HARQ report does not need to be separated into different RBs based on the PSSCH slot position at which one or more TBs are received.

[0080] As for the third region (403) in FIG. 13, multiple RBs are allocated for feeding back the connection-oriented groupcast ACK result / NACK result. In this case, the third region may be further divided into sub-regions of RBs according to the number of PSSCH slots in the HRW. In the case of N=2, i.e., when there are two PSSCH slots in the HRW, the third region may be divided into two sub-regions (409) and (410), one sub-region for each PSSCH slot. In the case of N=4, i.e., when there are four PSSCH slots in the HRW, the third region may be divided into two or four sub-regions. For example, if the indicated number of PSSCH slots for the connection-oriented groupcast is (pre)configured to be four in the HRW, the multiple RBs in the third region may be divided into four sub-regions, each sub-region designated for one PSSCH slot in the HRW. For example, if there are a total of eight RBs for the third region and the indicated number of PSSCH slots for connection-oriented groupcast is two in the HRW (408) (N=2), the third region may be separated into two sub-regions (409) and (410), and four RBs may be assigned to each sub-region or PSSCH slot (see also FIG. 13). After the sub-regions are clearly divided, the process for the Rx-UE to select a PSFCH RB in the sub-region and select a pair / set of PSFCH resources in the selected PSFCH RB may be the same as when N=1, and in this case, the member_ID of the Rx-UE or sequence in the groupcast, the number of transmitted PSSCH TBs, cyclic shift pair or offset index, and / or the source_ID of the Tx-UE may be used. Then, based on the ACK or NACK decoding result for the received one or more PSSCH TBs, the Rx-UE may determine a PSFCH resource / sequence from a pair / set of multiple PSFCH resources to feed back a HARQ report to the Tx-UE.

[0081] Based on either the process described with respect to Figure 11A or the process described with respect to Figure 11B, the determination of the PSFCH RB and the pair / set of PSFCH resources may be based on a starting subchannel index of the corresponding PSSCH received during SL communication. For example, the determination of the PSFCH RB and the pair / set of PSFCH resources may start from the same starting subchannel index used for the PSSCH received during SL communication.

[0082] A solution on how to determine PSFCH resources / sequences within a subchannel for PSFCH transmission for SL communication has been described in detail above. The above-mentioned PSFCH capacity and multiplexing problem has been solved while avoiding an increase in control signals by adjusting the amount of radio resources for PSFCH based on demand and by controlling the slots in which transmission cast types with high amount of ACK / NACK feedback may be transmitted. In addition, all PSFCH resources are efficiently utilized.

[0083] In addition, the rules regarding PSFCH mapping and ACK / NACK multiplexing are defined above, eliminating the need for the Tx-UE or Rx-UE to indicate or inform other UEs in control signaling of the exact location and PSFCH resource / sequence to use for feeding back HARQ reports, thus reducing the amount of control signaling overhead.

[0084] Furthermore, by allocating designated positions and PSFCH resources / sequences based on PSSCH slots or based on transmission cast type, the problem of needing to reserve PSFCH resources / sequences for ACK / NACK feedback is avoided, and the risk of PSFCH transmission collision is avoided.

[0085] As mentioned above, the network node 410 and the UEs 420 and 430 may use the circuitry described above with respect to Figures 5 and 6 to perform certain operations or processes described herein. These operations may be performed in response to a processing circuit or processor executing software instructions contained in a computer-readable medium, such as a main memory, a ROM, and / or a storage device. A computer-readable medium may be defined as a physical or logical memory device. For example, a logical memory device may include multiple memories in a single physical memory device or may be distributed across multiple physical memory devices. Each of the main memory, ROM, and storage device may include a computer-readable medium having instructions as program code. The software instructions may be loaded into the main memory for another computer-readable medium, such as a storage device, or may be loaded from another device via a communication interface.

[0086] Additionally, software instructions contained in the main memory, when executed on a processing circuit, may cause the processing circuit, including a data processor, to perform the operations or processes described herein. Alternatively, hardwired circuitry may be used in place of or in combination with software instructions to implement the processes and / or operations described herein. Thus, the implementations described herein are not limited to any specific combination of hardware and software.

[0087] The physical entities according to the different embodiments of the present invention, including elements, units, modules, nodes and systems, may constitute or store computer programs including software instructions, whereby when the computer programs are executed on the physical entities, the steps and operations according to the embodiments of the present invention are performed, i.e., the data processing means are caused to perform the operations. In particular, the embodiments of the present invention also relate to computer programs for performing the operations and steps according to the embodiments of the present invention, and further to any computer readable medium having stored thereon a computer program for performing the methods described above.

[0088] When the term module is used, there is no limitation as to how these elements may be distributed or how these elements may be assembled. That is, the components, modules, units of the network node 410 and the UEs 420 and 430 may be distributed into different software and hardware components or into other devices to provide the intended functions. Also, multiple separate elements and modules may be assembled to provide the intended functions. For example, the elements, modules, and functions of the node may be embodied by a microprocessor and memory similar to the node, including a bus, a processing unit, a main memory, a ROM, etc. The microprocessor may be programmed to perform the above operations, which may be stored as instructions in the memory.

[0089] Furthermore, the elements, modules, and units of the apparatus may be implemented in hardware, software, Field Programmable Gate Arrays (FPGAs), application-specific integrated circuits (ASICs), firmware, or the like.

[0090] It will be apparent to those skilled in the art that various modifications and variations can be made to the substance and method of the present invention, as well as to structure of the present invention, without departing from the scope or spirit of the invention.

[0091] While the present invention has been described with reference to specific embodiments and examples, which are intended in all respects to be illustrative and not restrictive, those skilled in the art will recognize that many different combinations of hardware, software, and / or firmware will be suitable for practicing the present invention.

[0092] Moreover, other implementations of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only. To this end, it will be understood that inventive aspects lie in less than all features of a single foregoing disclosed embodiment or configuration. Accordingly, the true scope and spirit of the invention is indicated by the following claims.

Claims

1. 1. A method for operating a user equipment (UE) performing sidelink (SL) communication, comprising: performing, by the UE, a procedure enabling the UE to determine Physical Sidelink Feedback Channel (PSFCH) resources for Hybrid Automatic Repeat Request (HARQ) reporting for the SL communication; The procedure is used to determine the PSFCH resource for the HARQ report based on a first characteristic and a second characteristic related to the SL communication, The procedure includes: determining a PSFCH resource block (RB) from among a set of RBs based on the first characteristic for the SL communication; determining a set of PSFCH resources within the determined PSFCH RB based on the second characteristic for the SL communication; selecting the PSFCH resource for HARQ reporting from the set of multiple PSFCH resources based on an acknowledgement (ACK) decoding result or a negative acknowledgement (NACK) decoding result of a Physical Sidelink Shared Channel (PSSCH) packet transport block (TB) received during the SL communication; The set of RBs is configured using an SL resource pool configuration, the SL resource pool configuration including PSFCH resource allocation and HARQ report related information; the SL resource pool configuration includes at least one PSFCH parameter related to a time domain allocation, a frequency domain allocation, or a cyclic shift allocation; The method comprises: allocating at least one PSFCH RB from the set of RBs into a subchannel; - dividing the at least one PSFCH RB in the sub-channel into a number of regions of RBs based on a number of Physical Sidelink Shared Channel (PSSCH) slots associated with the PSFCH slot or based on a number of PSSCH slots within a HARQ reporting window (HRW), with each region including at least one RB; selecting a region from among the plurality of regions of RBs based on a slot position in which a corresponding PSSCH is received; selecting the PSFCH RB within the selected region based on the first characteristic for the SL communication; determining the set of PSFCH resources within the selected region based on the second characteristic related to the SL communication; The first characteristic related to the SL communication includes a member ID for groupcast communication, the member ID being used to determine the PSFCH RB within the selected region when available; The method, wherein the second characteristic related to the SL communication includes at least a configured cyclic shift allocation and / or a source identification (ID) of a transmitting UE communicating with the UE.

2. The method of claim 1, further comprising: transmitting an ACK or NACK decoding result for the HARQ report using the PSFCH resource.

3. 2. The method of claim 1, wherein the set of RBs is configured for transmission and reception of a PSFCH and is represented as a bitmap.

4. The method of claim 1 , further comprising receiving the SL resource pool configuration from a network node or from a pre-configured in the UE.

5. 2. The method of claim 1, wherein the determination of the at least one PSFCH RB and the set of PSFCH resources is based on a starting subchannel index of the corresponding PSFCH received during the SL communication.

6. A user equipment (UE) configured to implement a method according to any one of claims 1 to 5.

7. A computer-readable storage medium containing instructions, comprising: The instructions, when executed by a computer, cause the computer to: A computer readable storage medium implementing the method according to any one of claims 1 to 5.

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