NR SL PSFCH transmission and monitoring

Abstract

The present invention relates to NR SL PSFCH transmission and monitoring, in particular, hybrid automatic repeat request (HARQ) timing may be determined. Physical SL feedback channel (PSFCH) resource pool selection may be performed. A source WTRU may signal (e.g., determine) PSFCH resources based on channel state information (CSI), transmitter (TX)-receiver (RX) distance, and / or CBR. The destination WTRU may determine a sub-channel including the PSFCH resource based on the PSCCH / PSSCH resource and / or the WTRU PHY ID information. One or more resource blocks within a sub-channel for PSFCH transmission may be determined based on the WTRU PHY ID and / or the link ID. A first set of symbols in a time slot may be sensed to detect PSSCH and / or PSSCH + PSFCH transmissions to (e.g., determine) transmit a PSFCH at the end of the time slot without colliding with the PSSCH. Once the PSFCH resources in the shared PSFCH resource pool are not available, the WTRU may switch to a dedicated PSFCH resource pool or mode 1 transmission.

Description

This application is a divisional application of Chinese patent application No. 202080027604.9, filed on April 8, 2020, entitled “NR SL PSFCH Transmission and Monitoring”. The contents of the parent application are incorporated herein by reference. CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 62 / 831,320 filed on April 9, 2019, U.S. Provisional Application No. 62 / 885,926 filed on August 13, 2019, U.S. Provisional Application No. 62 / 908,655 filed on October 1, 2019; U.S. Provisional Application No. 62 / 910,547 filed on October 4, 2019, and U.S. Provisional Application No. 62 / 930,825 filed on November 5, 2019, the contents of which are incorporated herein by reference. Background Art

[0002] Mobile communications using wireless communications continue to develop. The fifth generation may be referred to as 5G. The previous generation (eg, conventional) mobile communications may be, for example, fourth generation (4G) long term evolution (LTE). Summary of the invention

[0003] Hybrid automatic repeat request (HARQ) timing may be determined based on, for example, wireless transmit / receive unit (WTRU) capabilities, subcarrier spacing, transport block (TB) priority information, and / or channel busy ratio (CBR). Physical side link (SL) feedback channel (PSFCH) resource pool selection may be performed, for example, based on quality of service (QoS) requirements and / or CBR. The WTRU may determine PSFCH time and frequency resources. The source WTRU may signal (e.g., determine) PSFCH resources based on, for example, channel state information (CSI), transmitter (TX)-receiver (RX) distance, and / or CBR. The destination WTRU may determine a subchannel including PSFCH resources based on, for example, physical SL control channel (PSCCH) / physical SL shared channel (PSSCH) resources and / or WTRU physical (PHY) identifier (ID) information. One or more resource blocks (RBs) within a subchannel for PSFCH transmission may be determined based on, for example, the WTRU PHY ID and / or link ID. The first set of symbols in a slot may be sensed to detect PSSCH and / or PSSCH+PSFCH transmissions, for example, to (e.g., determine) that PSFCH is sent at the end of the slot without colliding with the PSSCH. For example, upon failure to acquire PSFCH resources in the shared PSFCH resource pool, the WTRU may switch to a dedicated PSFCH resource pool or Mode 1 transmission. PSSCH / PSCCH may be transmitted and received in a PSFCH slot.

[0004] The WTRU may determine the PSFCH resources based on, for example, the cast type and / or the HARQ feedback options. The WTRU may determine the frequency size of the PSFCH resources based on, for example, the bandwidth of the PSSCH. The WTRU may determine the PSFCH resources for PSSCH / PSCCH transmissions in an ACK / NACK based multicast transmission. For example, if the WTRU detects a possible conflict and / or if the WTRU must transmit PSSCH / PSCCH and transmit / receive PSFCH in the same timeslot, the WTRU may perform rate matching / puncturing and / or may adjust the modulation and coding scheme (MCS) used for the transmission. The WTRU may determine the transmission duration of the PSSCH / PSCCH in a timeslot with PSFCH resources, which may be based on, for example, the subchannel index of the PSSCH / PSCCH transmission.

[0005] The WTRU may select a PSFCH resource from a plurality of PSFCH resources corresponding to a PSSCH transmission. The RX WTRU may select a PSFCH resource from a set of PSFCH resources associated with (e.g., one) PSSCH transmission based on, for example, one or more of a preconfiguration, a WTRU L1 source ID, a HARQ ID, or a PSFCH transmission configuration. The WTRU may perform PSFCH blind detection between associated PSFCH resources. The WTRU may determine the PSFCH resources for option 2 multicast transmission based on, for example, ACK and / or NACK. The multicast PSFCH resource determination for option 2 HARQ operation (based on ACK / NACK) may be based on, for example, one or more of a WTRU L1 ID (e.g., source ID / randomly assigned ID), a WTRU TX-RX distance, a minimum communication range requirement, a reference signal received power (RSRP), an area / sub-area ID, a PSFCH power level, a path loss, and the like.

[0006] The WTRU may determine HARQ timing. The WTRU may determine the HARQ timing based on, for example, K and / or N values. The WTRU may use one or more N values, for example, to determine which time slots include PSFCH resources. The WTRU may use one or more K values, for example, to determine the time slots used for PSFCH transmission. For example, when the WTRU receives PSSCH in time slot #n, the WTRU may send HARQ feedback on the first time slot (e.g., which includes PSFCH resources after #n+K time slots). One or more K values ​​may be used. The K value may be determined based on, for example, at least one of the subcarrier spacing of the resource pool, the demodulation reference signal (DM-RS) pattern (e.g., pre-loading or pre-loading + additional DM-RS), the number of symbols of the PSCCH, the QoS of the packet, or the maximum QoS of the resource pool.

[0007] The WTRU may, for example, (e.g., determine) to flush the HARQ buffer based on a (pre)configured period. For example, when the WTRU receives a high priority transmission and / or there are no remaining HARQ transmissions / receptions for a low priority HARQ process, the WTRU may release the low priority HARQ process.

[0008] The WTRU may be configured to select a PSFCH resource. The WTRU may receive a PSFCH resource allocation or be preconfigured with a PSFCH resource allocation. The WTRU may receive an SCI associated with a PSSCH. The WTRU may determine a set of PSFCH resources within the PSFCH resource allocation. The WTRU may select a PSFCH resource within the set of PSFCH resources. The PSFCH resource may be (e.g., one) resource block. The selection may be based on (e.g., at least in part on) an L1 source ID (e.g., indicated in the SCI) and a HARQ process ID (e.g., indicated in the SCI). In one example, the selection of the PSFCH resource may be (e.g., further) based on time slot information and / or a group member ID. The WTRU may (e.g., further) be (pre)configured to, for example, send HARQ ACK / NACK information associated with the PSSCH on the selected PSFCH resource. The set of PSFCH resources within the PSFCH resource allocation may be determined, for example, based on a lowest PSSCH subchannel index and a PSSCH time slot number. There may be a mapping between (e.g., each) subchannel in a PSSCH resource pool and (e.g., one) PSFCH resource in the PSFCH resource allocation (e.g., for a received or preconfigured PSFCH resource). The received or preconfigured PSFCH resource may include a unicast resource and a multicast resource. The determination of the set of PSFCH resources within the PSFCH resource allocation may be based on a broadcast type. The selection of the PSFCH resource within the set of PSFCH resources may be (e.g., further) based on a broadcast type. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1A is a system diagram illustrating an exemplary communication system in which one or more disclosed embodiments may be implemented.

[0010] Figure 1B is a diagram showing that according to an embodiment, Figure 1A A system diagram of an exemplary wireless transmit / receive unit (WTRU) for use within a communication system is shown.

[0011] Figure 1C is a diagram showing that according to an embodiment, Figure 1A A system diagram of an exemplary radio access network (RAN) and an exemplary core network (CN) used within a communication system is shown.

[0012] Figure 1D is a diagram showing that according to an embodiment, Figure 1A A system diagram of another exemplary RAN and another exemplary CN used within the communication system shown.

[0013] Figure 2 Examples of HARQ transmissions using a dedicated PSFCH resource pool and / or a shared PSCCH resource pool are shown.

[0014] Figure 3 An example of multiplexing PSFCH transmission and PSSCH transmission in previously reserved resources is shown.

[0015] Figure 4 Example mapping of PSFCH to PSSCH / PSCCH based on playout type and / or HARQ is shown.

[0016] Figure 5 An example of a WTRU determining PSFCH resources in ACK / NACK based feedback multicast is shown.

[0017] Figure 6 An example of WTRU PSFCH resource determination and transmission for HARQ that may use a shared resource pool is shown.

[0018] Figure 7 An example of WTRU PSFCH detection and transmission for PSFCH occupying 1, 2, and 6 symbols is shown.

[0019] Figure 8 An example of WTRU PSFCH resource determination and monitoring for HARQ that may use a shared resource pool is shown. DETAILED DESCRIPTION

[0020] Figure 1A 1 is a schematic diagram of an exemplary communication system 100 in which one or more disclosed embodiments may be implemented. The communication system 100 may be a multiple access system that provides content such as voice, data, video, messaging, broadcast, etc. to multiple wireless users. The communication system 100 may enable multiple wireless users to access such content by sharing system resources including wireless bandwidth. For example, the communication system 100 may use one or more channel access methods such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single carrier FDMA (SC-FDMA), zero tail unique word DFT-spread OFDM (ZT UW DTS-s OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, and filter bank multi-carrier (FBMC), etc.

[0021] like Figure 1AAs shown, the communication system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, RAN 104 / 113, CN 106 / 115, public switched telephone network (PSTN) 108, Internet 110, and other networks 112, although it should be appreciated that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network components. Each of the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. By way of example, any of the WTRUs 102a, 102b, 102c, 102d may be referred to as a “station” and / or “STA”, which may be configured to transmit and / or receive wireless signals, and may include a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular phone, a personal digital assistant (PDA), a smart phone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watch or other wearable device, a head-mounted display (HMD), a vehicle, a drone, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices working in an industrial and / or automated process chain environment), consumer electronic devices, and devices working on a commercial and / or industrial wireless network, etc. Any of the WTRUs 102a, 102b, 102c, 102d may be interchangeably referred to as a UE.

[0022] The communication system 100 may also include a base station 114a and / or a base station 114b. Each of the base stations 114a, 114b may be any type of device configured to facilitate access to one or more communication networks (e.g., CN 106 / 115, Internet 110, and / or other networks 112) by wirelessly interfacing with at least one of the WTRUs 102a, 102b, 102c, 102d. For example, the base stations 114a, 114b may be a base transceiver station (BTS), a Node B, an eNode B, a Home Node B, a Home eNode B, a gNB, a New Radio (NR) Node B, a site controller, an access point (AP), a wireless router, and the like. Although each of the base stations 114a, 114b is depicted as a single component, it should be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and / or network components.

[0023] The base station 114a may be part of the RAN 104 / 113, and the RAN may also include other base stations and / or network components (not shown), such as a base station controller (BSC), a radio network controller (RNC), a relay node, and the like. The base station 114a and / or the base station 114b may be configured to transmit and / or receive wireless signals on one or more carrier frequencies called cells (not shown). These frequencies may be in a licensed spectrum, an unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide wireless service coverage for a specific geographic area that is relatively fixed or may change over time. A cell may be further divided into cell sectors. For example, a cell associated with the base station 114a may be divided into three sectors. Thus, in one embodiment, the base station 114a may include three transceivers, i.e., each transceiver corresponds to a sector of the cell. In an embodiment, the base station 114a may use multiple-input multiple-output (MIMO) technology, and may use multiple transceivers for each sector of the cell. For example, by using beamforming, signals may be transmitted and / or received in a desired spatial direction.

[0024] The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d over an air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, millimeter wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0025] More specifically, as described above, the communication system 100 may be a multiple access system and may use one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, and SC-FDMA, among others. For example, the base station 114a in the RAN 104 / 113 and the WTRUs 102a, 102b, 102c may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may use Wideband CDMA (WCDMA) to establish the air interface 115 / 116 / 117. WCDMA may include communication protocols such as High Speed ​​Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High Speed ​​Downlink (DL) Packet Access (HSDPA) and / or High Speed ​​UL Packet Access (HSUPA).

[0026] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 116 using Long Term Evolution (LTE) and / or Advanced LTE (LTE-A) and / or Advanced LTE Pro (LTE-A Pro).

[0027] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology that may use new radio (NR) to establish the air interface 116, such as NR radio access.

[0028] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may jointly implement LTE radio access and NR radio access (e.g., using dual connectivity (DC) principles). Thus, the air interface used by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions sent to / from multiple types of base stations (e.g., eNBs and gNBs).

[0029] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.11 (i.e., Wireless Fidelity (WiFi)), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile Communications (GSM), Enhanced Data Rates for GSM Evolution (EDGE), and GSM EDGE (GERAN), among others.

[0030] Figure 1AThe base station 114b in the example may be, for example, a wireless router, a Home NodeB, a Home eNodeB, or an access point, and may use any appropriate RAT to facilitate wireless connectivity in a local area, such as a business location, a residence, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a road, and the like. In one embodiment, the base station 114b and the WTRUs 102c, 102d may establish a wireless local area network (WLAN) by implementing a radio technology such as IEEE 802.11. In an embodiment, the base station 114b and the WTRUs 102c, 102d may establish a wireless personal area network (WPAN) by implementing a radio technology such as IEEE 802.15. In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may establish a picocell or a femtocell by using a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, and the like). As Figure 1A As shown, the base station 114b may be directly connected to the Internet 110. Thus, the base station 114b does not need to access the Internet 110 via the CN 106 / 115.

[0031] The RAN 104 / 113 may be in communication with the CN 106 / 115, which may be any type of network configured to provide voice, data, applications, and / or Voice over Internet Protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have different quality of service (QoS) requirements, such as different throughput requirements, latency requirements, fault tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 / 115 may provide call control, billing services, mobile location-based services, prepaid calls, Internet connectivity, video distribution, etc., and / or may perform advanced security functions such as user authentication. Although in Figure 1A Although not shown, it will be appreciated that the RAN 104 / 113 and / or the CN 106 / 115 may be in direct or indirect communication with other RANs that employ the same RAT or a different RAT as the RAN 104 / 113. For example, in addition to being connected to the RAN 104 / 113 employing NR radio technology, the CN 106 / 115 may also be in communication with another RAN (not shown) employing GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0032] The CN 106 / 115 may also act as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or other networks 112. The PSTN 108 may include a circuit-switched telephone network that provides plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer network devices that use common communication protocols, such as TCP, User Datagram Protocol (UDP), and / or IP in the Transmission Control Protocol / Internet Protocol (TCP / IP) Internet protocol suite. The networks 112 may include wired or wireless communication networks owned and / or operated by other service providers. For example, the networks 112 may include another CN connected to one or more RANs, where the one or more RANs may use the same RAT or a different RAT as the RAN 104 / 113.

[0033] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communication system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks over different wireless links). Figure 1A The illustrated WTRU 102c may be configured to communicate with the base station 114a, which may employ a cellular-based radio technology, and with the base station 114b, which may employ an IEEE 802 radio technology.

[0034] Figure 1B is a system diagram illustrating an exemplary WTRU 102. Figure 1B As shown, the WTRU 102 may include a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a numeric keypad 126, a display / touchpad 128, a non-removable memory 130, a removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and / or peripherals 138. It should be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0035] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors associated with a DSP core, a controller, a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) circuit, any other type of integrated circuit (IC), a state machine, and the like. The processor 118 may perform signal coding, data processing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. Although Figure 1B The processor 118 and the transceiver 120 are depicted as separate components, however it should be appreciated that the processor 118 and the transceiver 120 may also be integrated together in an electronic package or chip.

[0036] The transmit / receive component 122 may be configured to transmit or receive signals to or from a base station (e.g., base station 114a) via the air interface 116. For example, in one embodiment, the transmit / receive component 122 may be an antenna configured to transmit and / or receive RF signals. As an example, in another embodiment, the transmit / receive component 122 may be an emitter / detector configured to transmit and / or receive IR, UV, or visible light signals. In yet another embodiment, the transmit / receive component 122 may be configured to transmit and / or receive RF and light signals. It should be appreciated that the transmit / receive component 122 may be configured to transmit and / or receive any combination of wireless signals.

[0037] Although in Figure 1B 102 as a single component, the WTRU 102 may include any number of transmit / receive components 122. More specifically, the WTRU 102 may employ MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit / receive components 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0038] The transceiver 120 may be configured to modulate signals to be transmitted by the transmit / receive component 122 and to demodulate signals received by the transmit / receive component 122. As described above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers that allow the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11.

[0039] The processor 118 of the WTRU 102 may be coupled to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light emitting diode (OLED) display unit), and may receive user input data from these components. The processor 118 may also output user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. In addition, the processor 118 may access information from and store information in any suitable memory such as the non-removable memory 130 and / or the removable memory 132. The non-removable memory 130 may include a random access memory (RAM), a read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, and the like. In other embodiments, the processor 118 may access information from and store data in memories that are not physically located in the WTRU 102, such as, for example, a server or a home computer (not shown).

[0040] The processor 118 may receive power from the power source 134, and may be configured to distribute and / or control power for use by other components in the WTRU 102. The power source 134 may be any suitable device for powering the WTRU 102. For example, the power source 134 may include one or more dry cell batteries (e.g., nickel-cadmium (Ni-Cd), nickel-zinc (Ni-Zn), nickel-metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, and the like.

[0041] The processor 118 may also be coupled to the GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) related to the current location of the WTRU 102. In addition to or in lieu of the information from the GPS chipset 136, the WTRU 102 may receive location information from a base station (e.g., base stations 114a, 114b) via the air interface 116 and / or determine its location based on the timing of signals received from two or more nearby base stations. It should be appreciated that the WTRU 102 may acquire location information via any suitable positioning method while remaining consistent with an embodiment.

[0042] The processor 118 may also be coupled to other peripheral devices 138, wherein the peripheral devices may include one or more software and / or hardware modules that provide additional features, functions, and / or wired or wireless connectivity. For example, the peripheral devices 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos and / or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, Modules, frequency modulation (FM) radio units, digital music players, media players, video game console modules, Internet browsers, virtual reality and / or augmented reality (VR / AR) devices, and activity trackers, etc. The peripheral device 138 may include one or more sensors, which may be one or more of the following: gyroscopes, accelerometers, Hall effect sensors, magnetometers, orientation sensors, proximity sensors, temperature sensors, time sensors, geographic location sensors, altimeters, light sensors, touch sensors, magnetometers, barometers, gesture sensors, biometric sensors, and / or humidity sensors, etc.

[0043] The WTRU 102 may include a full-duplex radio in which reception or transmission of some or all signals (e.g., associated with specific subframes for UL (e.g., for transmission) and downlink (e.g., for reception)) may be concurrent and / or simultaneous for the radio. A full-duplex radio may include an interference management unit that reduces and / or substantially eliminates self-interference by means of hardware (e.g., chokes) or by signal processing by a processor (e.g., a separate processor (not shown) or by the processor 118). In an embodiment, the WTRU 102 may include a half-duplex radio that transmits and receives some or all signals (e.g., associated with specific subframes for UL (e.g., for transmission) or downlink (e.g., for reception)).

[0044] Figure 1C 1 is a system diagram showing the RAN 104 and the CN 106 according to an embodiment. As described above, the RAN 104 may communicate with the WTRUs 102a, 102b, 102c using an E-UTRA radio technology over the air interface 116. The RAN 104 may also communicate with the CN 106.

[0045] The RAN 104 may include eNode-Bs 160a, 160b, 160c, however it will be appreciated that the RAN 104 may include any number of eNode-Bs while remaining consistent with an embodiment. The eNode-Bs 160a, 160b, 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the eNode-Bs 160a, 160b, 160c may implement MIMO technology. Thus, for example, the eNode-B 160a may use multiple antennas to transmit wireless signals to, and / or receive wireless signals from, the WTRU 102a.

[0046] Each of the eNodeBs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, user scheduling in the UL and / or DL, etc. Figure 1C As shown, the eNode-Bs 160a, 160b, 160c may communicate with each other via an X2 interface.

[0047] Figure 1C The illustrated CN 106 may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (or PGW) 166. Although each of the aforementioned components is described as being part of the CN 106, it should be appreciated that any of these components may be owned and / or operated by an entity other than the CN operator.

[0048] The MME 162 may be connected to each of the eNode-Bs 162a, 162b, 162c in the RAN 104 via an S1 interface and may serve as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, performing bearer activation / deactivation processing, selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c, and the like. The MME 162 may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as GSM and / or WCDMA.

[0049] The SGW 164 may be connected to each of the eNode-Bs 160a, 160b, 160c in the RAN 104 via an S1 interface. The SGW 164 may generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 may also perform other functions, such as anchoring the user plane during an inter-eNB handover, triggering paging processing when DL data is available for the WTRUs 102a, 102b, 102c, and managing and storing the contexts of the WTRUs 102a, 102b, 102c, and the like.

[0050] The SGW 164 may be connected to the PGW 146, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0051] The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. For example, the CN 106 may include or communicate with an IP gateway, such as an IP Multimedia Subsystem (IMS) server, and the IP gateway may serve as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers.

[0052] Although in Figures 1A-1D Although the WTRU is described as a wireless terminal, it should be appreciated that in certain representative embodiments, such a terminal may use a (eg, temporary or permanent) wired communication interface with a communication network.

[0053] In a representative embodiment, the other network 112 may be a WLAN.

[0054] A WLAN using an infrastructure basic service set (BSS) mode may have an access point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP may access or be connected to a distributed system (DS) or other types of wired / wireless networks that send traffic into and / or out of the BSS. Traffic originating from outside the BSS and destined for the STA may arrive through the AP and be delivered to the STA. Traffic originating from the STA and destined for a destination outside the BSS may be sent to the AP for delivery to the corresponding destination. Traffic between STAs within the BSS may be sent through the AP, for example, when the source STA may send traffic to the AP and the AP may deliver traffic to the destination STA. Traffic between STAs within the BSS may be considered and / or referred to as point-to-point traffic. The point-to-point traffic may be sent using a direct link establishment (DLS) between the source and destination STAs (e.g., directly therebetween). In certain representative embodiments, the DLS may use 802.11e DLS or 802.11z channelized DLS (TDLS)). For example, a WLAN using an independent BSS (IBSS) mode does not have an AP, and STAs (eg, all STAs) within or using the IBSS can communicate directly with each other. Here, the IBSS communication mode may sometimes be referred to as an "ad-hoc" communication mode.

[0055] When using the 802.11ac infrastructure mode of operation or a similar mode of operation, the AP may transmit a beacon on a fixed channel (e.g., a primary channel). The primary channel may have a fixed width (e.g., a bandwidth of 20 MHz) or a width that is dynamically set via signaling. The primary channel may be an operating channel of the BSS and may be used by STAs to establish a connection with the AP. In certain representative embodiments, carrier sense multiple access (CSMA / CA) with collision avoidance (e.g., in an 802.11 system) may be implemented. For CSMA / CA, STAs (e.g., each STA) including the AP may sense the primary channel. If a particular STA senses / detects and / or determines that the primary channel is busy, the particular STA may back off. In a specified BSS, there is one STA (e.g., only one station) transmitting at any given time.

[0056] A high throughput (HT) STA may communicate using a 40 MHz wide channel (eg, by combining a 20 MHz wide primary channel with a 20 MHz wide adjacent or non-adjacent channel to form a 40 MHz wide channel).

[0057] Very high throughput (VHT) STA can support channels with widths of 20MHz, 40MHz, 80MHz and / or 160MHz. 40MHz and / or 80MHz channels can be formed by combining continuous 20MHz channels. A 160MHz channel can be formed by combining 8 continuous 20MHz channels or by combining two discontinuous 80MHz channels (this combination can be referred to as an 80+80 configuration). For the 80+80 configuration, after channel coding, the data can be transmitted and passed through a segment parser, which can separate the data into two streams. Inverse Fast Fourier Transform (IFFT) processing and time domain processing can be performed separately on each stream. The stream can be mapped on two 80MHz channels, and the data can be transmitted by the STA performing the transmission. At the receiver of the STA performing the reception, the above operations for the 80+80 configuration can be reversed, and the combined data can be sent to the medium access control (MAC).

[0058] 802.11af and 802.11ah support working modes below 1 GHz. Compared with 802.11n and 802.11ac, the channel working bandwidth and carrier used in 802.11af and 802.11ah are reduced. 802.11af supports 5MHz, 10MHz and 20MHz bandwidths in the TV White Space (TVWS) spectrum, and 802.11ah supports 1MHz, 2MHz, 4MHz, 8MHz and 16MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11ah can support meter type control / machine type communication (MTC) (e.g., MTC devices in macro coverage areas). MTC devices can have certain capabilities, such as limited capabilities including support (e.g., only support) certain and / or limited bandwidths. MTC devices can include a battery, and the battery life of the battery is higher than a threshold (e.g., for maintaining a very long battery life).

[0059] For WLAN systems that can support multiple channels and channel bandwidths (e.g., 802.11n, 802.11ac, 802.11af, and 802.11ah), these systems include channels that can be designated as primary channels. The bandwidth of the primary channel can be equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel can be set and / or limited by a certain STA, where the STA originates from all STAs operating in the BSS that supports the minimum bandwidth operating mode. In the example of 802.11ah, even if the AP and other STAs in the BSS support 2MHz, 4MHz, 8MHz, 16MHz, and / or other channel bandwidth operating modes, for STAs (e.g., MTC-type devices) that support (e.g., only support) 1MHz mode, the width of the primary channel can be 1MHz. Carrier sensing and / or network allocation vector (NAV) settings can depend on the status of the primary channel. If the primary channel is busy (e.g., because a STA (which only supports the 1MHz operating mode) transmits to the AP), then even if most of the available frequency bands remain idle and available for use, the entire available frequency band can be considered busy.

[0060] In the United States, the available frequency band for 802.11ah is 902MHz to 928MHz. In South Korea, the available frequency band is 917.5MHz to 923.5MHz. In Japan, the available frequency band is 916.5MHz to 927.5MHz. Depending on the country code, the total bandwidth available for 802.11ah is 6MHz to 26MHz.

[0061] Figure 1D 1 is a system diagram showing the RAN 113 and the CN 115 according to an embodiment. As described above, the RAN 113 may communicate with the WTRUs 102a, 102b, 102c using NR radio technology over the air interface 116. The RAN 113 may also communicate with the CN 115.

[0062] The RAN 113 may include gNBs 180a, 180b, 180c, though it will be appreciated that the RAN 113 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, 180c may each include one or more transceivers to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, the gNBs 180a, 180b may use beamforming processing to transmit and / or receive signals to and / or from the gNBs 180a, 180b, 180c. Thus, for example, the gNB 180a may use multiple antennas to transmit wireless signals to the WTRU 102a and receive wireless signals from the WTRU 102a. In an embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation technology. For example, gNB 180a may transmit multiple component carriers to WTRU 102a (not shown). A subset of these component carriers may be on unlicensed spectrum, while the remaining component carriers may be on licensed spectrum. In an embodiment, gNBs 180a, 180b, 180c may implement coordinated multi-point (CoMP) technology. For example, WTRU 102a may receive coordinated transmissions from gNB 180a and gNB 180b (and / or gNB 180c).

[0063] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with a scalable digital configuration. For example, the OFDM symbol spacing and / or OFDM subcarrier spacing may be different for different transmissions, different cells, and / or different portions of the radio transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using subframes or transmission time intervals (TTIs) of different or scalable lengths (e.g., containing different numbers of OFDM symbols and / or lasting different absolute time lengths).

[0064] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c without accessing other RANs (e.g., the eNodeBs 160a, 160b, 160c). In a standalone configuration, the WTRUs 102a, 102b, 102c may use one or more of the gNBs 180a, 180b, 180c as mobility anchors. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration, the WTRU 102a, 102b, 102c may communicate / connect to the gNB 180a, 180b, 180c while communicating / connecting to another RAN (e.g., the eNode-B 160a, 160b, 160c). For example, the WTRU 102a, 102b, 102c may communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c in a substantially simultaneous manner by implementing the DC principle. In a non-standalone configuration, the eNode-B 160a, 160b, 160c may act as a mobility anchor for the WTRU 102a, 102b, 102c, and the gNB 180a, 180b, 180c may provide additional coverage and / or throughput to serve the WTRU 102a, 102b, 102c.

[0065] Each of the gNBs 180a, 180b, 180c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, user scheduling in UL and / or DL, support network slicing, dual connectivity, implement interworking between NR and E-UTRA, route user plane data to a user plane function (UPF) 184a, 184b, and route control plane information to an access and mobility management function (AMF) 182a, 182b, and the like. Figure 1D As shown, gNBs 180a, 180b, and 180c can communicate with each other through the Xn interface.

[0066] Figure 1DThe CN 115 shown may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one session management function (SMF) 183a, 183b, and may include a data network (DN) 185a, 185b. Although each of the aforementioned components is described as part of the CN 115, it should be understood that any of these components may be owned and / or operated by an entity other than the CN operator.

[0067] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via the N2 interface and may act as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRU 102a, 102b, 102c, supporting network slicing (e.g., handling different PDU sessions with different requirements), selecting a specific SMF 183a, 183b, managing registration areas, terminating NAS signaling, and mobility management, etc. The AMF 182a, 182b may use network slicing processing to customize the CN support provided to the WTRU 102a, 102b, 102c based on the type of service used by the WTRU 102a, 102b, 102c. As an example, different network slices may be established for different use cases, such as services relying on Ultra Reliable Low Latency (URLLC) access, services relying on enhanced massive mobile broadband (eMBB) access, and / or services for machine type communication (MTC) access, etc. The AMF 182 may provide a control plane function for switching between the RAN 113 and other RANs (not shown) using other radio technologies (e.g., LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies such as WiFi).

[0068] The SMF 183a, 183b may be connected to the AMF 182a, 182b in the CN 115 via the N11 interface. The SMF 183a, 183b may also be connected to the UPF 184a, 184b in the CN 115 via the N4 interface. The SMF 183a, 183b may select and control the UPF 184a, 184b, and may configure traffic routing through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions such as managing and allocating WTRU or UE IP addresses, managing PDU sessions, controlling policy enforcement and QoS, and providing downlink data notifications, etc. The PDU session type may be IP-based, non-IP-based, Ethernet-based, etc.

[0069] The UPF 184a, 184b can be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via the N3 interface, which can provide the WTRUs 102a, 102b, 102c with access to packet-switched networks (e.g., the Internet 110) to facilitate communication between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPF 184, 184b can perform other functions, such as routing and forwarding packets, implementing user plane policies, supporting multi-host PDU sessions, processing user plane QoS, buffering downlink packets, and providing mobility anchor processing, etc.

[0070] The CN 115 may facilitate communications with other networks. For example, the CN 115 may include or may communicate with an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that acts as an interface between the CN 115 and the PSTN 108. In addition, the CN 115 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to the local data network (DN) 185a, 185b via an N3 interface connected to the UPF 184a, 184b and an N6 interface between the UPF 184a, 184b and the DN 185a, 185b and through the UPF 184a, 184b.

[0071] In view of Figures 1A-1D and about Figures 1A-1D In accordance with the corresponding description of the present invention, one or more or all functions described herein in comparison with one or more of the following may be performed by one or more simulation devices (not shown): WTRU 102a-d, base station 114a-b, eNodeB 160a-c, MME 162, SGW 164, PGW 166, gNB 180a-c, AMF 182a-b, UPF 184a-b, SMF 183a-b, DN185ab and / or one or more other devices described herein. These simulation devices may be one or more devices configured to simulate one or more or all functions described herein. For example, these simulation devices may be used to test other devices and / or simulate network and / or WTRU functions.

[0072] The simulation device can be designed to implement one or more tests about other devices in a laboratory environment and / or an operator network environment. For example, the one or more simulation devices can perform one or more or all functions while being implemented and / or deployed as a part of a wired and / or wireless communication network in whole or in part to test other devices inside the communication network. The one or more simulation devices can perform one or more or all functions while being temporarily implemented or deployed as a part of a wired and / or wireless communication network. The simulation device can be directly coupled to other devices to perform the test, and / or can use over-the-air wireless communication to perform the test.

[0073] One or more simulation devices can perform one or more functions, including all functions, while not being implemented or deployed as part of a wired and / or wireless communication network. For example, the simulation device can be used in a test lab and / or a test scenario of a wired and / or wireless communication network that is not deployed (e.g., testing) to implement tests on one or more components. The one or more simulation devices can be test devices. The simulation device can transmit and / or receive data using direct RF coupling and / or wireless communication with the aid of RF circuits (e.g., which can include one or more antennas).

[0074] New Radio (NR) hybrid automatic repeat request (HARQ) transmissions may be performed, for example, associated with a Uu interface, such as uplink unicast, downlink unicast, downlink groupcast, etc. HARQ ACK / NACK information may be sent in a physical uplink control channel (PUCCH). A wireless transmit / receive unit (WTRU) may not (e.g., desire) to transmit more than one PUCCH with HARQ ACK / NACK information in a slot. NR Uu may support five PUCCH formats, such as short PUCCH formats 0 and 2 and long PUCCH formats 1, 3, and 4. A short PUCCH format may assign, for example, one to two symbols for PUCCH transmission. A long PUCCH format may assign, for example, four to 14 symbols for PUCCH transmission. PUCCH format 0 may be sequence-based and the associated frequency resource allocation may be (e.g., fixed at) one resource block (RB).

[0075] The WTRU may determine the PUCCH resources for HARQ transmission, for example, based on a configuration. The configuration may be a semi-static configuration. For example, before radio resource control (RRC) is established, the (e.g., semi-static) configuration may be received, for example, in RRC signaling or a system information block (SIB). The WTRU may be configured with (e.g., up to) four PUCCH resource sets. A PUCCH resource set (e.g., each PUCCH resource set) may include, for example, eight different PUCCH resources. The PUCCH resources may include one or more parameters, such as a resource ID, a PUCCH format, a starting physical resource block (PRB), a number of PRBs (e.g., for format 2 / 3), a starting symbol, a number of symbols, an initial cyclic shift index (e.g., for format 0 / 1), an index and length of an orthogonal cover code (OCC) (e.g., for format 4), etc.

[0076] The configuration may be a dynamic configuration. For example, a configuration (e.g., including a PDSCH-to-HARQ timing indicator and a PUCCH resource indicator) may be received (e.g., dynamically) in a downlink control information (DCI) format 1_0 / 1_1 in an NR physical downlink control channel (PDCCH), which may be associated with an NR physical downlink shared channel (PDSCH) corresponding to the HARQ transmission.

[0077] The WTRU may select a PUCCH resource based on, for example, the PUCCH resource indicator, the number of total control channel elements (CCEs) in a control resource set (CORESET), and / or the first CCE of an associated NR PDCCH (e.g., based on a dynamic configuration). The WTRU may transmit a PUCCH carrying the HARQ information in the selected PUCCH resource within a time slot, which may be determined, for example, based on the PDSCH-HARQ timing indicator.

[0078] HARQ feedback may be supported in NR sidelink (SL) unicast transmissions and multicast SL transmissions. (Pre) configuration may (e.g., be used to) indicate whether SL HARQ feedback is enabled or disabled. For example, if SL HARQ feedback is enabled, there may be conditions under which the SL HARQ feedback is not used. The WTRU may (e.g., in unicast transmissions) perform decoding of a transport block (TB) carried in an associated physical SL shared channel (PSCCH) based on sidelink control information (SCI) received, for example, in the PSSCH. For example, if the decoding of the TB is successful, the WTRU may generate a HARQ ACK, or, for example, if the decoding fails, the WTRU may generate a HARQ NACK. The WTRU may (e.g., subsequently) transmit the generated HARQ ACK / NACK information in a physical SL feedback channel (PSFCH). The time gap between the PSFCH and the associated PSSCH may not be signaled (e.g., explicitly) in the SCI carried in the associated PSCCH.

[0079] One or more (e.g., two) HARQ transmissions may be considered for multicast transmissions. For example, HARQ NACK-only transmissions may be used. For example, if the WTRU fails to decode a TB based on an SCI decoded from an associated PSCCH, the WTRU may transmit a HARQ NACK in the PSFCH. For example, if the WTRU successfully decodes the TB, the WTRU may not perform a HARQ ACK transmission. HARQ NACK-only transmissions may reduce HARQ signaling overhead in multicast transmissions, but may cause various problems (e.g., ambiguity between a successfully received TB and a failed PSCCH decoding). HARQ ACK / NACK transmissions may be used for, for example, multicast HARQ transmissions. HARQ ACK / NACK transmissions may be in accordance with unicast HARQ transmissions disclosed herein.

[0080] NR SL implementation(s) may impose strict requirements on data transmission reliability and latency. NRSL HARQ and PSFCH designs may provide highly reliable resource selection for HARQ transmissions.

[0081] Inter-WTRU conflicts between HARQ and aperiodic transmissions may occur, for example, in Mode 2 SL transmissions. The WTRU may (e.g., in Mode 2 SL transmissions) select transmission resources, for example, based on a sensing mechanism. For example, a sensing mechanism may be implemented for semi-static periodic (SPS) resource reservation (e.g., as used for periodic traffic in vehicular communications such as LTE V2X). This type of long-term sensing may not prevent conflicts between a HARQ transmission and another aperiodic SL transmission using the same resources. In Mode 2 SL transmissions, when the congestion level is high, there may be no available resources for the HARQ transmission within the required HARQ timing.

[0082] In an example, HARQ reception may be limited by half-duplex operation. The WTRU (e.g., due to half-duplex operation) may not be able to receive HARQ transmissions during a transmission period, for example, if the WTRU transmits bursts of non-periodic traffic with low latency requirements, which may result in potential lost HARQ transmissions and / or data transmission delays. The WTRU may adjust the SL transmission set and the associated HARQ reception based on, for example, the delay budget for each TB to be transmitted and / or the HARQ timing for each received TB. For example, the impact of half-duplex on HARQ transmissions may be reduced by more frequent transmit / receive (Tx / Rx) switching. For example, a flexible implementation may be used to avoid unnecessary loss of link capacity, for example, because each Tx / Rx switch may take one symbol out of the SL operation. Introducing more Tx / Rx switches in a time slot may reduce the impact of the half-duplex constraint and / or may reduce the link capacity (e.g., if the WTRU hardware requires dedicated symbols to perform Tx / Rx switches).

[0083] A standalone PSFCH transmission may be performed. For example, if the WTRU has no data to transmit in the buffer and the HARQ transmission is due according to the HARQ timing of the received TB, the WTRU may transmit a standalone PSFCH carrying HARQ ACK / NACK in a timeslot without PSCCH and PSSCH. Various aspects related to, for example, the NR SL PSFCH and timeslot structure implementation may be considered. For example, an appropriate automatic gain control (AGC) stabilization period and / or sufficient AGC gain may be achieved for the PSFCH, for a WTRU expecting a HARQ transmission, and / or for a WTRU performing sensing.

[0084] In an example, intra-WTRU collisions of simultaneous HARQ transmissions may occur. The WTRU may maintain multiple unicast / multicast links. For example, based on the HARQ timing of two or more transmissions, the two or more HARQ transmissions may fall into the same time slot. WTRU processing may be implemented, for example, with respect to how the WTRU prioritizes and multiplexes the HARQ transmissions, how the WTRU adjusts resource allocations and / or transmission parameters, etc., for example, so as to successfully complete all HARQ transmissions.

[0085] The transmitting WTRU may be referred to as the source WTRU. The receiving WTRU may be referred to as the destination WTRU. The following examples may be used herein. The WTRU transmitting the PSSCH and associated PSCCH may be referred to as the source WTRU (e.g., with respect to the HARQ transmission in the PSFCH and the associated data transmission in the PSSCH). The WTRU receiving the PSCCH and PSSCH and sending the associated PSFCH may be referred to as the destination WTRU. The source WTRU and destination WTRU designations may be applied with respect to the direction of the PSSCH transmission.

[0086] The PSFCH resources may be determined. The WTRU may determine the HARQ timing. The WTRU may be (pre)configured with a set of HARQ timings. The HARQ timing may be based on, for example, the PSSCH to HARQ time and / or the HARQ transmission time. Figure 2 An example of HARQ transmission using a dedicated PSFCH resource pool and / or a shared PSCCH resource pool is shown. The PSSCH to HARQ time may be the time between the end of a PSSCH transmission and the start of an associated HARQ transmission (e.g., Figure 2 The HARQ transmission time may be the time used for the associated HARQ transmission (eg, T1). Figure 2 The PSSCH to HARQ time may take into account the time that the WTRU may need to decode the PSCCH and the associated PSSCH with a given TB size (e.g., the maximum configurable TB for SL transmission). The HARQ transmission time may include the time to acquire PSFCH resources and the actual PSFCH transmission (e.g., in Mode 2 operation) and may be limited by the delay budget of the transmitted TB.

[0087] The WTRU may select the HARQ timing for the TB transmission from the (pre)configured HARQ timing set based on, for example, one or more of the WTRU processing capability, the SL subcarrier spacing, the priority information of the TB, and / or the channel busy status. The WTRU may look up these parameters in the (pre)configured mapping and select the corresponding HARQ timing. For example, the mapping may include the PSSCH to HARQ time (T1) for the TB transmission, where T1 may be determined, for example, according to the following equation 1: T1=T WTRU ×(2048+144)×2 -μ ×T s Equation 1 T WTRU μ may be the (pre-)configured WTRU processing capability for decoding the PSCCH and associated PSSCH (e.g., the number of symbols for each SL subcarrier spacing). μ may be the subcarrier spacing of the PSCCH / PSSCH / PSFCH. The SL transmit and receive bandwidth parts (BWP) may be, for example, the same, and the subcarrier spacing of the PSCCH / PSSCH / PSFCH may be, for example, the same. s It can be the duration of one sample specific to the system sampling frequency (e.g., 1 / F s , where F s It can be, for example, 30.72 MHz).

[0088] The mapping may include a HARQ transmission time (T2) for the TB transmission, which is based on, for example, a HARQ timing upper bound based on the latency requirement of the TB (e.g., a packet delay budget (PDB)). The (pre-)configured mapping may indicate the HARQ timing for the (pre-)configured latency requirements (e.g., each requirement) supported by the WTRU (e.g., a low latency TB transmission may be mapped to a low T2). The mapping may include a HARQ transmission time (T2) for the TB transmission, which is based on, for example, an estimate of the time to acquire PSFCH resources at a given measured channel busy ratio (CBR) level. The (pre-)configuration may provide additional time, for example, provided that the final T2 may be lower than the HARQ timing upper bound. In one example, for example, if the measured CBR level is lower than a (pre-)configured threshold, the (pre-)configuration may indicate that there is no additional time (e.g., zero) for resource acquisition, otherwise (e.g., for a high CBR level at or above the threshold), the time slot (e.g., T2) includes, for example, an additional time slot.

[0089] The HARQ timing in the (pre-)configuration may be specified based on the number of slots / mini-slots / symbols, e.g. based on the sum of the PSSCH to HARQ time and the HARQ transmission time value (e.g. T1+T2 with reference to T0).

[0090] The WTRU may include the priority information and CBR value of the TB in the SCI carried in the PSCCH that schedules the PSSCH transmission. The source WTRU and the destination WTRU may obtain related (e.g., identical) HARQ timing, for example, based on a common (pre-)configuration. The source WTRU may monitor the HARQ transmission according to the HARQ timing, for example, between T0+T1 and T0+T1+T2, where T0 may be at the end of the last symbol of the associated PSCCH / PSSCH transmission (e.g., as Figure 2 The destination WTRU may generate a HARQ ACK / NACK before T1 and transmit a PSFCH (eg, carrying the HARQ ACK / NACK) between T0+T1 and T0+T1+T2, for example, according to the same or similar HARQ timing.

[0091] The WTRU may determine the HARQ timing, for example, based on one or more transmission parameters. HARQ feedback may be sent on PSFCH resources. A set of PSFCH resources may be configured in each time slot. The network may, for example, configure PSFCH resources in a subset of time slots for a resource pool. For example, the network may configure one or more of N time slots to include PSFCH resources, where N may be a non-negative integer (e.g., 0, 1, 2, 4). For example, if N=0, the resource pool may not include PSFCH resources. For example, if N=1, multiple time slots (e.g., all time slots) may include PSFCH resources. For example, if N=2, even-numbered time slots or odd-numbered time slots may include PSFCH resources.

[0092] For example, if the WTRU receives sidelink data (e.g., PSSCH and / or PSCCH) in time slot #n, the WTRU may determine a time slot that includes PSFCH resources for the corresponding HARQ transmission. The determined time slot that includes the PSFCH resources may be referred to as time slot #n+a, where a may be the smallest integer greater than or equal to K, for example, under the condition that time slot #n+a includes PSFCH resources.

[0093] In an example, a time slot may be a logical time slot or a physical time slot. A physical time slot may be, for example, a time slot defined as a frame structure. A logical time slot may be, for example, a time slot configured, used and / or numbered for V2X purposes. A logical time slot may be configured as a resource pool (e.g., a Tx or Rx resource pool). A resource pool may be referred to interchangeably with a Tx resource pool, an Rx resource pool, and / or a sidelink resource pool.

[0094] For example, the K value of the resource pool or sidelink transmission can be determined based on one or more sidelink transmission parameters. (One or more) sidelink transmission parameters may include one or more of the following. The sidelink transmission parameters may include, for example, the QoS of the packet (e.g., priority, reliability, data rate, minimum communication range, latency, etc.). A smaller K value may result in a shorter latency and / or higher reliability. The sidelink transmission parameters may include, for example, the subcarrier spacing of the sidelink bandwidth portion. For example, if a smaller subcarrier spacing is used, a smaller K value may be used. For example, K=2 may be used for 15kHz and / or 30kHz subcarrier spacing, and K=3 may be used for 60kHz subcarrier spacing. The sidelink transmission parameters may include, for example, the cyclic prefix length. The sidelink transmission parameters may include, for example, the number of symbols used for and / or configured for PSCCH, PSSCH, and / or PSFCH. The sidelink transmission parameters may include, for example, the time slot length. The sidelink transmission parameters may include, for example, the number of symbols available for sidelink transmission in a time slot. For example, if the number of symbols available for the sidelink in a time slot is less than a threshold, a first K value may be used. For example, if the number of symbols available for the side link in the time slot is equal to or greater than a threshold, a second K value may be used. The side link transmission parameters may include, for example, the number of bandwidth portions configured for the side link in the carrier. The side link transmission parameters may include, for example, a demodulation reference signal (DM-RS) pattern (e.g., only front-end loaded DM-RS or front-end loaded DM-RS with additional DM-RS). For example, if a first DM-RS pattern (e.g., front-end loaded DM-RS) is used, a first K (e.g., smaller) value may be used, and, for example, if a second DM-RS pattern (e.g., front-end loaded DM-RS+additional DM-RS) is used, a second K (e.g., larger) value may be used. The first K value may be less than the second K value.

[0095] The sidelink transmission parameters may include, for example, a transmission power level. The sidelink transmission parameters may include, for example, a power control mode. In an example, a first power control mode may use a maximum transmission power allowed or configured. The second power control may be based on, for example, an open loop power control using a path loss (e.g., a Uu path loss or a SL path loss). In an example, the first power control mode may be based on a Uu path loss, and the second power control mode may be based on a SL path loss.

[0096] The sidelink transmission parameters may include, for example, a congestion level (e.g., CBR). For example, if the CBR is above a threshold, a first K value may be used. For example, if the CBR is below the threshold, a second K value may be used. The first K value may be less than the second K value. For example, if (e.g., when) the CBR is reduced, the resources occupied by the WTRU may be reduced. For example, if the resources occupied by the WTRU are reduced, the congestion level may be reduced. The sidelink transmission parameters may include, for example, a channel occupancy ratio (e.g., CR). For example, if the CR is above a threshold, a first K value may be used, and, for example, if the CR is below the threshold, a second K value may be used. The first K value may be less than the second K value. The sidelink transmission parameters may include, for example, enabling and / or disabling of CSI feedback. The sidelink transmission parameters may include, for example, a subchannel size (e.g., the number of RBs used for a subchannel). The sidelink transmission parameters may include, for example, a (e.g., configured) number of resource pools. The sidelink transmission parameters may include, for example, a (e.g., configured) N value (e.g., one PSFCH resource is included for every N time slots). The sidelink transmission parameters may include, for example, a PSFCH configuration (e.g., short PSFCH or long PSFCH). The sidelink transmission parameters may include, for example, a packet size. For example, if the packet size (e.g., maximum packet size) is less than a threshold for a service, a smaller K value may be used. For example, if the packet size is greater than or equal to the threshold for the service, a larger K value may be used. The sidelink transmission parameters may include, for example, the number of retransmissions. The sidelink transmission parameters may include, for example, a broadcast type (e.g., multicast or unicast). In one example, a first K value may be used for multicast transmissions, while a second K value may be used for unicast transmissions. The sidelink transmission parameters may include, for example, an expected transmission / reception of the WTRU in the UL or another RAT. The WTRU may determine which K value to select. For example, the WTRU may determine which K value to use based on the expected transmission / reception, for example, in the UL or another RAT. In one example, for example, if the WTRU is expected to receive / transmit in a time slot of the UL or LTE RAT that overlaps with a PSFCH transmission of the first K value, the WTRU may change from the first K value to the second K value. The sidelink transmission parameters may include, for example, the Tx-Rx distance between the WTRUs.

[0097] The value of K may be determined based on, for example, WTRU capabilities. For example, a set of K values ​​may be configured (e.g., K={2,3,4,5}), and the WTRU may determine a minimum number of K values ​​based on the WTRU capabilities. WTRU capabilities may be exchanged between WTRUs (e.g., via PC5-RRC), for example, for sidelink unicast and / or multicast transmissions. WTRU capabilities may be reported to the network.

[0098] One or more K values ​​may be used, and a K value may be configured for a resource pool. For example, the one or more K values ​​may include K={2,3,4,5,6}, and one of the K values ​​may be configured for a resource pool. WTRUs (e.g., all WTRUs) in the same resource pool may use the same configured K value. For example, a subset of K values ​​may be used (e.g., allowed to be used) based on one or more of the following. A subset of K values ​​may be used based on, for example, a QoS configured for a resource pool (e.g., a QoS restriction). For example, a resource pool may be configured with a QoS restriction. For example, if the QoS of a packet is lower than the QoS restriction, the packet may not be transmitted on the sidelink resource pool. For example, if the QoS restriction is lower than a threshold, a K value (e.g., all K values) may be configured. For example, if the QoS restriction is higher than a threshold, a subset of K values ​​(e.g., K={2}) may be configured. A subset of K values ​​may be used based on, for example, subcarrier spacing. For example, if the subcarrier spacing configured for a resource pool is higher than a threshold, a subset of K values ​​(e.g., K={4,5}) may be used. For example, if the subcarrier spacing configured for the resource pool is lower than or equal to a threshold, a K value (e.g., all K values) may be used or another subset of K values ​​(e.g., K={2,3}) may be used. A subset of K values ​​may be used based on, for example, a DM-RS pattern. One or more DM-RS patterns (e.g., time density and / or frequency patterns) may be used. A subset of DM-RS patterns may be configured for a resource pool. For example, a subset of K values ​​applicable to the resource pool may be determined based on a set of DM-RS patterns configured for the resource pool. For example, if a front-end loading DM-RS pattern (e.g., only a front-end loading DM-RS pattern) is configured for the resource pool, a smaller K value (e.g., a K value with a smaller value) may be used (e.g., K={2,3}). A front-end loading DM-RS pattern may be referred to as a DM-RS pattern in which a DM-RS symbol is located in the first half of a time slot. For example, if a front-end loading DM-RS pattern with an additional DM-RS pattern is configured for a resource pool, a larger K value (e.g., a K value with a larger value) may be used (e.g., K={4,5,6}). A subset of K values ​​may be used based on, for example, the number of symbols used for PSCCH in a subchannel.The number of symbols used for PSCCH within a subchannel may be predefined, preconfigured and / or determined based on, for example, one or more transmission parameters.

[0099] The subset of K values ​​used for the resource pool may be determined based on, for example, one or more sidelink transmission parameters.

[0100] One or more K values ​​may be configured for a resource pool. The WTRU may determine which of the one or more configured K values ​​to use for sidelink transmissions, for example based on one or more of the following. The WTRU may determine which K value to use for sidelink transmissions based on, for example, one or more sidelink transmission parameters. A (e.g., single) PSSCH / PSCCH transmission may be associated with multiple PSFCH resources. For example, a PSSCH / PSCCH transmission in slot #n may be associated with a PSFCH resource in slot #n+a1 and another PSFCH resource in slot #n+a2. The WTRU may determine which PSFCH resource to use based on, for example, a determined K value. In one example, for example, if K=2 is used, the WTRU may (e.g., determine) to use the PSFCH resource in slot #n+a1. For example, if K=3 is used, the WTRU may (e.g., determine) to use the PSFCH resource in slot #n+a2. A single sidelink transmission (e.g., PSCCH / PSCCH) may be associated with a set of PSFCH resources within slot #n+a. The (e.g., one) PSFCH resource in a timeslot may be determined based on, for example, at least one of an ID (e.g., source ID, destination ID, group member ID), one or more sidelink transmission parameters, and / or the number of member WTRUs in the group. The group member ID may be an ID assigned to the WTRUs in the group for multicast. A subset of K values ​​may be used based on, for example, WTRU capabilities. In one example, WTRU capability information may be reported to the network or exchanged between WTRUs via PC5-RRC, for example, for unicast or multicast. A subset of K values ​​may be used based on, for example, a configuration of N. For example, K may be determined as a function of N.

[0101] The K value may be referred to as, for example, a reference timing for PSFCH resource determination, a HARQ reference timing, a HARQ minimum required time, a minimum required processing time, and / or a PSFCH timing.

[0102] One or more subsets of PSFCH resources may be configured. (E.g., each) subset of PSFCH resources may be associated with a (e.g., a specific) K value and / or a broadcast type (e.g., multicast, unicast). For example, M subsets of PSFCH resources may be configured with M K values ​​(e.g., K = {1, 2, 3, .., M}). (Each) K value may be associated with a subset of PSFCH resources. For example, if (e.g., when) the WTRU determines the K value, the WTRU may determine the PSFCH resources within the relevant subset of PSFCH resources. A subset of PSFCH resources may be referred to as, for example, a PSFCH resource pool. Resources across subsets of PSFCH resources may be mutually exclusive.

[0103] The WTRU may determine a PSFCH resource pool. The WTRU may be (pre)configured with one or more resource pools for PSSCH transmission. The PSSCH frequency resources in the PSSCH resource pool may be sub-channel based. A sub-channel (e.g., each sub-channel) may include a (pre)configured number of RBs. The PSSCH time resources in the PSSCH resource pool may be time slot based. The WTRU may perform PSSCH resource allocation based on a granularity of, for example, sub-channels in the frequency domain and time slots in the time domain. The WTRU may be (pre)configured to apply a PSSCH resource pool for PSFCH resource allocation (e.g., a shared resource pool between PSSCH and PSFCH transmissions).

[0104] A WTRU may be (pre)configured with one or more resource pools for PSFCH transmission. A WTRU that is (pre)configured with resources, resource pools, etc. may describe a WTRU that receives the resources, resource pools, etc., or a WTRU that is preconfigured with the resources, resource pools, etc. A PSFCH resource pool may not overlap with a PSSCH resource pool in frequency (e.g., a dedicated PSFCH resource pool). The WTRU may perform PSFCH resource allocation based on a granularity of, for example, RBs in the frequency domain and symbols in the time domain (e.g., for a shared PSFCH resource pool and a dedicated PSFCH resource pool).

[0105] The WTRU may determine whether a shared or dedicated PSFCH resource pool may be used for HARQ transmission associated with a TB transmission based on, for example, QoS requirements (e.g., ProSe per-packet priority (PPPP), ProSe per-packet reliability (PPPR), and / or PDB) and / or channel busyness (e.g., CBR). For example, if the QoS requirements (e.g., priority (e.g., PPPP) and / or reliability (e.g., PPPR)) of a TB are higher than a (pre)configured threshold, and / or latency (e.g., PDB) is lower than a (pre)configured threshold, the WTRU may select a dedicated PSFCH resource pool for HARQ transmission associated with the TB. For example, if the measured CBR of the dedicated PSFCH resource pool is higher than the CBR of the shared PSFCH resource pool and the difference exceeds a (pre)configured threshold, the WTRU may select the shared PSFCH resource pool for HARQ transmission.

[0106] The WTRU may select a dedicated PSFCH resource pool to apply based on, for example, one or more of the following attributes: a set of contiguous RBs, a QoS requirement threshold (e.g., PPPP, PPPR, and / or PDB), a service type (e.g., unicast and / or multicast), and / or a maximum Doppler frequency supported. For example, one or more attributes may be (pre)configured for each dedicated PSFCH pool. For example, if the QoS requirement for the associated TB transmission is above the threshold, the WTRU may use a dedicated PSFCH pool for HARQ transmission. The WTRU may determine the service type, for example, based on information from a received PSSCH / PSCCH transmission, which may include, for example, a radio network temporary identifier (RNTI) for scrambling a CRC of an SCI for a PSCCH, an SCI format, SCI content, a DM-RS configuration (e.g., type 1 or type 2 mapping, or a DMRS time and / or frequency density for PSCCH and / or PSSCH). The maximum Doppler frequency may be (pre)configured for (e.g., each) dedicated PSFCH resource pool. For example, if the estimated maximum Doppler frequency (eg, the relative Doppler frequencies of the two WTRUs of a link) is lower than the (pre-)configured maximum Doppler frequency, the WTRU may use the PSFCH resource pool.

[0107] The WTRU may include PSFCH resource pool information in the PSCCH scheduling of the PSSCH associated with the HARQ transmission. The PSFCH resource pool information may indicate, for example, whether a dedicated or shared PSFCH resource pool may be applied. For example, if a shared PSFCH resource pool is applied, the WTRU may use the same PSSCH resource pool used for the PSSCH transmission associated with the PSFCH transmission. The PSFCH resource pool information may indicate which dedicated PSFCH resource pool may be selected.

[0108] A bit field in the SCI may provide a set of code points to convey PSFCH resource pool information. The length of this field may depend, for example, on the number of (pre)configured dedicated PSFCH resource pools. In one example, a 2-bit field may indicate a shared PSFCH pool, for example by setting both bits to zero, and may provide an index to a dedicated PSFCH resource pool, for example by setting one or both bits to one.

[0109] The WTRU may determine a PSFCH resource in a dedicated PSFCH resource pool. The WTRU may select a PSFCH resource from the dedicated PSFCH resource pool and / or may determine the attributes of the PSFCH resource that the WTRU needs to select (e.g., the number of RBs). In an example, the WTRU may determine the PSFCH resource based on, for example, a (pre-)configured association between a dedicated PSFCH resource pool and a PSSCH resource pool. The WTRU may determine the PSFCH resource in the dedicated PSFCH resource pool based on, for example, a (pre-)configured association with a PSSCH resource pool for associated PSCCH / PSSCH transmissions. The WTRU may be (pre-)configured with, for example, a mapping between subchannels (e.g., each subchannel) in a PSSCH resource pool and PSFCH resources in the dedicated PSFCH resource pool. A PSSCH subchannel may be mapped to more than one PSFCH resource (e.g., such as Figure 2 The WTRU may determine one or more PSFCH resources in the dedicated PSFCH resource pool based on, for example, the first subchannel used for PSSCH or PSCCH transmission and the mapping. The WTRU may repeat PSFCH transmissions (e.g., which utilize multiple PFSCH resources) in a PSFCH resource (e.g., each PSFCH resource). In a PSFCH resource (e.g., each PSFCH resource), the WTRU may perform sensing at the beginning of a timeslot and, for example, if no conflict is indicated by sensing, make a PSFCH transmission in the same timeslot.

[0110] The WTRU may sense PSFCH resources in a dedicated PSFCH resource pool. A WTRU (e.g., a WTRU that is not the destination of a PSSCH transmission) may decode the PSSCH scheduling information in the SCI in the PSCCH and may determine the associated PSFCH transmission resources. The WTRU may determine the PSFCH resources in a dedicated PSFCH resource pool based on, for example, a PSSCH / PSCCH resource allocation. The WTRU may determine the PSFCH resources that will be reserved for the period between the minimum and maximum (pre) configured HARQ timing. The WTRU may exclude PSSCH resources that may result in the same PSFCH resources in the dedicated PSFCH resource pool during the HAQR timing period to, for example, avoid potential collisions of PSFCH transmissions.

[0111] The WTRU may determine PSFCH resources in a shared PSFCH resource pool. The WTRU may select PSFCH resources from a shared PSFCH resource pool and / or may determine attributes (e.g., number of RBs) of resources that the WTRU may (e.g., need to) select. The WTRU may determine (one or more) subchannels that include PSFCH resources. The source WTRU may determine the PSFCH subchannel based on, for example, a transmission from a destination WTRU. The source WTRU may determine the PSFCH subchannel associated with a PSSCH transmission based on, for example, one or more transmissions (e.g., received from a destination WTRU), which may include, for example, one or more of an RS transmission (e.g., SL-CSI-RS, SL-RLM-RS, etc.), a PSCCH / PSSCH transmission, and / or a HARQ transmission. The WTRU may perform measurements on multiple transmissions, for example, to obtain measurement metrics, including, for example, subband channel quality indicator (CQI), SL-RSRP, L1-RSRP, SL received signal strength indicator (RSSI), signal-to-noise ratio (SNR), etc. The WTRU may select a subchannel for PSFCH transmission (eg, a subchannel with the best subband CQI for HARQ transmission) based on, for example, a measurement metric.

[0112] The source WTRU may determine the PSFCH subchannel, for example, based on sensing. The source WTRU may determine the PSFCH resource associated with the PSSCH, for example, based on sensing results. The source WTRU may select the PSFCH subchannel from available resources determined, for example, by detection within the HARQ timing. For example, the source WTRU may select the earliest available resource within the determined HARQ timing.

[0113] The source WTRU may determine the PSFCH subchannel and the indication in the SCI. The WTRU may (e.g., be (pre)configured to) perform the source WTRU PSFCH subchannel determination (e.g., as disclosed herein) based on, for example, one or more of: PSFCH resource allocation mode, suitability of the destination WTRU transmission, channel busy ratio, TX-RX distance between the source WTRU and the destination WTRU, and / or QoS requirements. The source WTRU may (e.g., be (pre)configured to) perform PSFCH resource allocation.

[0114] For example, if the source WTRU receives a destination WTRU transmission within a (e.g., (pre)configured) period prior to a PSSCH transmission, the source WTRU may determine the PSFCH subchannel. The sum of the length of the period and the HARQ timing of the PSSCH transmission may not exceed the channel coherence time (e.g., channel conditions based on transmissions received during the period may apply at the HARQ timing). For example, for a high mobility WTRU, the period may be short.

[0115] For example, if the measured channel busy ratio (CBR) is below a (pre-)configured threshold, the source WTRU may determine the PSFCH subchannel. The collision probability (eg, collision probability caused by other WTRUs using the same transmission resources) may be low.

[0116] For example, based on, for example, SL measurements (e.g., including SL-RSRP, SL-RSSI, etc.), if the TX-RX distance is below a (pre-)configured threshold, the source WTRU may determine the PSFCH subchannel. For example, if the distance between the source WTRU and the destination WTRU is less than the threshold, the sensing results obtained by the source WTRU and the destination WTRU may become correlated.

[0117] For example, if the QoS requirements (eg, PPPP, PPPR and / or PDB) are above a (pre-)configured threshold, the source WTRU may not perform PSFCH sub-channel determination.

[0118] The WTRU may include PSFCH resource reservation information in the SCI (e.g., which is carried in the PSCCH that schedules the PSSCH corresponding to the HARQ transmission). For example, the source WTRU may indicate the PSFCH subchannel allocation along with other HARQ information (e.g., HARQ process ID) in a bit field in the SCI. The source WTRU's determination of the PSFCH subchannel may result in a reduction in the time required or used by the destination WTRU to acquire PSFCH resources, for example, through sensing. The PSFCH resource reservation in the SCI may be decoded by other WTRUs (e.g., through sensing) (e.g., and may be used to prevent collisions).

[0119] Figure 2An example of HARQ transmission using a dedicated PSFCH resource pool and / or a shared PSCCH resource pool is shown. In the example, a dedicated PSFCH frequency resource allocation may be (pre)configured, such as a dedicated PSFCH resource pool. The dedicated PSFCH frequency resource allocation may include PSFCH frequency resources, such as a set of subchannels and / or RBs that may not be used for PSSCH transmission. In the example, a shared PSFCH frequency resource allocation may be (pre)configured, such as a shared PSFCH resource pool. The shared PSFCH frequency resource allocation may include PSFCH frequency resources, such as a set of subchannels and / or RBs that may be used for PSSCH transmission. In the PSFCH frequency resource allocation, a set of PSFCH frequency resources (e.g., a set of RBs) may be associated with a PSSCH transmission and may be applied to send HARQ feedback corresponding to the PSSCH transmission. Within the associated set of PSFCH frequency resources, the WTRU may determine the PSFCH frequency resources, such as one RB, used for the actual PSFCH transmission. This determination may be based on the WTRU source ID and / or the HARQ process ID.

[0120] The destination WTRU may determine the PSFCH resources based on, for example, the associated PSCCH / PSSCH transmissions. The WTRU may not receive PSFCH resource allocation information for HARQ transmissions in the SCI carried in the PSCCH that schedules the corresponding PSSCH transmissions. The WTRU may determine the PSFCH resource allocation (e.g., when a shared PSFCH resource pool is used) based on, for example, one or more of the following: WTRU physical layer (PHY) ID information (e.g., including source ID, destination ID, HARQ process ID, etc.), link ID information (e.g., including link ID, group ID, service ID, etc.), PSCCH frequency resources (e.g., including PSCCH subchannels and RB allocations), PSSCH frequency resources (e.g., including PSSCH subchannels and RB allocations), DM-RS resources and sequence configurations for PSCCH and PSSCH, related SL transmission QoS parameters (e.g., priority, reliability, latency, and range), (e.g., existing) resource reservations for future PSSCH / RS transmissions to the source WTRU, CBR, and / or the TX-RX distance between the source WTRU and the destination WTRU. For example, link ID information may be used to distinguish between multiple established unicast / multicast transmissions.

[0121] The WTRU may determine a subchannel (e.g., to include PSFCH resources therein) based on, for example, a WTRU PHY ID. The WTRU may determine one or more subchannels (e.g., to include PSFCH resources therein) based on, for example, one or more of a source ID, a destination ID, and / or a HARQ process ID. The WTRU may select a subchannel whose index is equal to the result of an arithmetic operation (e.g., a modulo function) based on, for example, the source ID and / or destination ID and the total number of PSSCH subchannels in the PSSCH resource pool.

[0122] The WTRU may select a subchannel (e.g., to include PSFCH resources therein) based on, for example, PSCCH / PSSCH frequency resources and / or QoS requirements. The WTRU may determine a subset of PSSCH subchannels (e.g., to include PSFCH resources therein) based on, for example, the QoS of the associated TB transmission. The QoS may include one or more QoS parameters (e.g., PPPP, PPPR and / or range). For example, if the QoS is below a (pre)configured threshold, the WTRU may use subchannels of the PSSCH (e.g., starting with the subchannel with the lowest subchannel index among the PSSCH subchannels used by the associated PSFCH transmission). For example, if the QoS is above a (pre)configured threshold, the WTRU may select one or more (e.g., all) PSSCH subchannels (e.g., to include PSFCH resources therein).

[0123] The WTRU may select subchannels (e.g., to include PSFCH resources) based on, for example, PSCCH frequency resources. The WTRU may determine a subset of PSCCH subchannels (e.g., to include PSFCH resources therein) based on, for example, PSCCH subchannel allocations. For example, the WTRU may select (e.g., for a PSFCH transmission) subchannel(s) for an associated PSCCH transmission.

[0124] The WTRU may select a subchannel (e.g., to include PSFCH resources therein) based on, for example, the SL coverage level. The WTRU may determine a subset of PSCCH subchannels (e.g., to include PSFCH resources therein) based on, for example, the SL coverage level. For example, if the TX-RX distance is greater than a (pre-)configured threshold, the WTRU may apply repetition of the associated (one or more) PSFCHs in the selected subchannels (e.g., each selected subchannel). The threshold may be based on, for example, the range used (e.g., required) by the associated TB transmission.

[0125] The WTRU may select a subchannel (e.g., to include PSFCH resources therein) based on, for example, the WTRU PHY ID and / or link ID. The WTRU may determine a PSSCH subchannel (e.g., whose index is equal to the result of an arithmetic operation, such as a modulo function) based on, for example, the PHY ID and / or link ID and the total number of subchannels used by the associated PSSCH.

[0126] The WTRU may select a subchannel (e.g., to include PSFCH resources therein) based on, for example, the CBR. The WTRU may determine the PSSCH subchannel based on, for example, the measured CBR level. For example, if the measured CBR is above a (pre-)configured threshold, the WTRU may select one or more (e.g., all) PSSCH subchannels (e.g., to include PSFCH resources therein).

[0127] The WTRU may determine the HARQ ACK / NACK sequence based on, for example, the WTRU PHY ID. The WTRU may determine the sequence for PSFCH transmission based on, for example, one or more of the HARQ ACK / NACK information, source ID, destination ID, link ID, HARQ process ID, and / or related PSFCH resources (e.g., PSFCH symbol / slot number). The WTRU may determine a cyclic shift index of the HARQ ACK / NACK sequence based on, for example, the HARQ process ID, which may distinguish concurrent PSFCH transmissions to the same source WTRU associated with different TB transmissions. The WTRU may determine the cyclic shift index of the HARQ ACK / NACK sequence based on, for example, the source ID, for example, to distinguish HARQ ACK / NACKs provided to different source WTRUs.

[0128] The WTRU may determine the PSFCH resources, for example, using (e.g., existing) resource reservations for future PSSCH / RS transmissions to the source WTRU. For example, if the reserved resources satisfy the HARQ timing, the WTRU may (e.g., determine) to use one or more (e.g., all) resources that the WTRU has reserved for PSSCH or RS transmissions for HARQ transmission. The WTRU may determine the PSFCH resources (e.g., as disclosed herein) and may multiplex the PSFCH with the scheduled PSSCH transmission.

[0129] Figure 3 An example of multiplexing PSFCH transmission and PSSCH transmission in previously reserved resources is shown. Figure 3As shown, a source WTRU with respect to a PSSCH transmission in time slot n may have received a PSSCH transmission in time slot ny from a destination WTRU which may have reserved resources in time slot x+n for future PSSCH transmissions. The PSSCH transmission in time slot n may have associated HARQ timing in time slot n+x. The source WTRU and destination WTRU may (e.g., determine) to multiplex a PSFCH transmission in a scheduled PSSCH transmission. The source WTRU and destination WTRU may be (pre-)configured with puncturing or rate matching for the PSSCH transmission, for example, to accommodate the PSFCH transmission.

[0130] The WTRU may (e.g., determine) to multiplex the PSFCH with periodic / SPS / aperiodic RS transmissions using reserved resources that satisfy HARQ timing. For example, if multiplexing between PSFCH and RS transmissions is not feasible, the WTRU may be (pre)configured with priority treatment. For example, the WTRU may be (pre)configured to drop RS transmissions and transmit PSFCH in resources reserved for said RS transmissions (e.g., if multiplexing is not feasible).

[0131] The WTRU may determine the PSFCH resources within a subchannel. The PSFCH resources may be defined, determined, configured, and / or used based on, for example, one or more of: one or more (e.g., contiguous or non-contiguous) RBs (e.g., a set of RBs) within a subchannel, carrier, and / or BWP, one or more (e.g., contiguous or non-contiguous) symbols (e.g., a set of symbols) within a slot, one or more transmission sequences (e.g., Zadoff-Chu (ZC) sequences) (e.g., a set of transmission sequences), an associated DM-RS configuration (e.g., type 1 or type 2 DMRS mapping), a scrambling sequence for the DM-RS, and / or an associated orthogonal cover code (OCC) configuration (e.g., the length and / or index of the OCC).

[0132] One or a group of (e.g., contiguous or non-contiguous) RBs within a subchannel, carrier and / or BWP can be indicated, for example, by a starting RB (e.g., the index of the first RB of the PSFCH resource) and / or a bandwidth (e.g., the number of contiguous RBs of the PSFCH resource).

[0133] The symbol may be, for example, a digital Fourier transform spread OFDM (DFT-s-OFDM) or a cyclic prefix OFDM (CPOFDM) symbol. The symbol may be indicated, for example, by a starting symbol (e.g., the index of the first symbol of the PSFCH resource), a duration and / or a length (e.g., the number of consecutive symbols of the PSFCH resource).

[0134] For example, the transmission sequence may be indicated by a cyclic shift index. The density of the DM-RS in frequency and / or time may be different based on, for example, an associated DM-RS configuration. The scrambling sequence may be initialized based on, for example, a subchannel index.

[0135] The WTRU may determine the PSFCH resources (e.g., within a subchannel) based on, for example, one or more of: (pre-)configuration, PHY ID (e.g., source ID, destination ID, HARQ process ID), link ID (e.g., link identifier and / or link index that the WTRU may use to maintain and distinguish between multiple established unicast and multicast transmissions), SCI format type carried in the PSCCH (e.g., unicast SCI and / or multicast SCI), QoS parameters of the associated TB (e.g., priority, reliability, latency and / or range), PSSCH resource configuration (e.g., subchannel size and / or slot duration), and / or PSSCH transmission slot number.

[0136] The PSFCH may occupy one or more symbols and / or RBs. The PFSCH resources may be (pre)configured to use one or more consecutive symbols (e.g., one symbol at symbol #12 or two symbols at symbols #11 and #12) before (e.g., immediately before) the Tx / Rx switching symbol at the end of the slot.

[0137] The WTRU may determine the number of symbols of the PSFCH resource based on, for example, the symbols, RBs and / or CCEs occupied by the associated PSCCH. For example, the WTRU may be (pre)configured with a mapping between the number of symbols and / or RBs of the PSFCH and the number of CCEs used by the PSCCH. For example, a large number of CCEs may be used to schedule a PSCCH for TB transmissions with high range requirements. For example, if the number of CCEs exceeds a (pre)configured threshold, the mapping may indicate that one or more (e.g., all) symbols in the timeslot are used for PSFCH transmissions.

[0138] The WTRU may determine the number of symbols and / or RBs to use for a PSFCH transmission based on, for example, the QoS requirements of the associated TB transmission (e.g., as indicated in the received PSCCH). For example, the WTRU may use multiple symbols for a PSFCH transmission associated with a TB transmission having a PPPP and / or PPPR above a (pre-)configured threshold. The WTRU may apply one or more (e.g., all) symbols in a timeslot to a PSFCH transmission associated with a TB transmission that requires a range (e.g., TX-RX distance) greater than a (pre-)configured threshold.

[0139] The WTRU may determine the PSFCH starting RB based on, for example, a WTRU PHY ID (e.g., source ID, destination ID, and / or link ID). In one example, the WTRU may determine the starting RB index based on, for example, a portion of the PHY / link ID (e.g., one or more most significant bits (MSBs)) and the number of RBs in the subchannel using an arithmetic operation (e.g., a modulo function).

[0140] The WTRU may determine the PSFCH starting RB, for example, based on whether the PSFCH is associated with a unicast transmission or a multicast transmission. For example, the WTRU may be (pre)configured with an RB index offset for a PSFCH transmission associated with a multicast transmission. The PSFCH for unicast transmission may be at the bottom of the subchannel. The PSFCH for multicast transmission may be at the top of the channel.

[0141] The WTRU may determine the PSFCH starting RB based on, for example, the associated PSCCH frequency resource allocation. For example, the WTRU may determine the PSFCH starting RB based on, for example, the starting PSCCH RB and / or the index of the PSSCH subchannel (e.g., including the PSCCH resources). The WTRU may use the RB used by the associated PSCCH for the PSFCH.

[0142] The WTRU may determine the PSFCH starting RB based on, for example, the HARQ process ID. For example, the WTRU may use an RB with the same index as the result of an arithmetic operation (eg, a modulo function) based on, for example, the number of RBs of the subchannel and the number of supported HARQ processes.

[0143] The WTRU may determine the PSFCH starting RB based on, for example, a predefined formula. The predefined formula may include one or more parameters, such as one or more of: PSSCH transmission slot, PSSCH subchannel index, WTRU ID, and / or HARQ process ID.

[0144] The WTRU may select a PSFCH resource from a plurality of PSFCH resources corresponding to a PSSCH transmission (eg, one PSSCH transmission).

[0145] For example, as described herein, a WTRU may determine a set of PSFCH resources associated with a PSSCH transmission (e.g., a PSSCH transmission). For example, a WTRU may determine a set of PSFCH resources that may be located at the same symbol in a timeslot (e.g., a timeslot) and may occupy a plurality of consecutive subchannels (one or more) and / or a plurality of consecutive RBs (one or more) within a subchannel. The WTRU may determine the set of PSFCH resources based on, for example, the timeslot, the frequency allocation of the received PSSCH (e.g., the index of the timeslot), the lowest PSSCH subchannel index, and / or the PSCCH subchannel index.

[0146] The WTRU may select a PSFCH resource (e.g., one PSFCH resource) among the (e.g., determined) PSFCH resources to send HARQ ACK / NACK information corresponding to the received PSSCH. The WTRU may select the PSFCH resource based on, for example, one or more of the following. The WTRU may select the PSFCH resource based on, for example, availability (e.g., based on sensing results). The WTRU may select the PSFCH resource based on, for example, a preconfiguration. The WTRU may select the PSFCH resource based on, for example, an L1 source ID. The WTRU may receive the L1 source ID, for example, in an SCI associated with the PSSCH. The WTRU may select the PSFCH resource based on, for example, a HARQ process ID. The WTRU may receive the HARQ process ID, for example, in an SCI associated with the PSSCH. The WTRU may select the PSFCH resource based on, for example, a PSSCH broadcast type. The WTRU may receive the PSSCH broadcast type, for example, in an SCI associated with the PSSCH. The PSSCH broadcast type may indicate whether the received PSSCH is unicast or multicast. The WTRU may select PSFCH resources, for example, based on whether multiple simultaneous PSFCH transmissions are performed using PSFCH resources within the same PSFCH resource set. Multiple PSSCHs received by the RXWTRU may be associated with the same PSFCH resource set. Multiple PSSCHs may be in the same time slot and different subchannels. Multiple PSSCHs may be in different time slots and the same (one or more) subchannels. The WTRU may select PSFCH resources, for example, based on whether PSSCH is transmitted in the time slot in which the PSFCH resource set is located. The WTRU may select PSFCH resources, for example, based on whether the PSSCH transmission and the PSFCH transmission are for the same WTRU.

[0147] The WTRU may select a preconfigured PSFCH resource from a set of PSFCH resources. The preconfigured PSFCH resource may be, for example, a PSFCH resource with the lowest subchannel index, the highest subchannel index, or a subchannel in the middle of the frequency range occupied by the set of PSFCH resources. In one example, the WTRU may select the PSFCH resources in the order of the lowest subchannel index to the highest subchannel index to the subchannel in the middle of the frequency range occupied by the set of PSFCH resources. The WTRU may select the PSFCH resources using a selection order, for example, depending on which resources are available (e.g., based on sensing results).

[0148] The WTRU may select a PSFCH resource based on the L1 source ID and / or the HARQ ID. The WTRU may determine (eg, calculate) the RB index of the PSFCH resource using a predefined hash function. The L1 source ID and / or the HARQ ID may be an input to the predefined hash function.

[0149] The WTRU may be (pre-)configured with unicast and multicast PSFCH resources within a PSFCH set. The WTRU may select the corresponding PSFCH resource based on, for example, the broadcast type (eg, unicast or multicast) of the PSSCH associated with the PSFCH transmission.

[0150] For example, if (e.g., when) the RX WTRU performs multiple (e.g., simultaneous) PSFCH transmissions, the RX WTRU may (e.g., determine) to use multiple PSFCH resources that occupy consecutive frequency resources. For example, the RX WTRU may transmit the PSFCH transmission in (one or more) adjacent RBs. The RX WTRU may adjust the power level of (e.g., each) PSFCH transmission, for example, to keep the power offset between the PSFCHs within a (pre)configured threshold. The (pre)configured threshold may depend on, for example, the absolute PSFCH power. For example, the RX WTRU may set the PSFCH power level of (e.g., each) PSFCH transmission to be at the highest individual PSFCH power based on, for example, PSFCH power control. Adjacent frequency allocation and PSFCH power adjustment may maintain the WTRU transmission efficiency above a predefined threshold and / or may reduce spurious and intermodulation interference.

[0151] The WTRU may select a PSFCH resource in a subchannel that may be selected for a PSSCH transmission in the same timeslot. For example, the WTRU may transmit a PSSCH transmission in a first portion of a timeslot (e.g., symbol 0 to symbol 11). The WTRU may transmit a PSFCH transmission in a second portion of the timeslot (e.g., the remaining portion). The second portion of the timeslot may include, for example, symbol 12. Symbol 13 of the timeslot may be used for TX / RX switching. For example, if a PSSCH transmission and a PSFCH transmission are for the same WTRU, the WTRU may select a PSFCH resource allocated in (e.g., one) subchannel among multiple subchannels used by the PSSCH transmission. For example, if a PSSCH transmission and a PSFCH transmission are for different WTRUs, the WTRU may select a PSFCH resource allocated in a subchannel that is not included in a PSSCH subchannel. The WTRU may use a gap between a PSSCH transmission and a PSFCH transmission in the timeslot. The gap may, for example, have a duration of one symbol.

[0152] The WTRU may determine the PSFCH resources for option 2 multicast transmission, for example, based on ACK / NACK. In one example, the WTRU may determine the PSFCH resources for option 2 multicast transmission based on one or more of, for example, ACK (e.g., transmitted in a PSFCH transmission), NACK (e.g., transmitted in a PSFCH transmission), and / or the number of HARQ ACK / NACK bits.

[0153] The RX WTRU may determine the PSFCH resources from a set of multicast PSFCH resources. The set of multicast PSFCH resources may be associated with a multicast PSSCH transmission. The RX WTRU may determine the PSFCH resources based on, for example, a combination of the WTRU L1 ID and one or more of the following. The RX WTRU may determine the PSFCH resources based on, for example, a WTRU TX-RX distance. The WTRU TX-RX distance may be the distance between the TX WTRU and the RX WTRU. The WTRU TX-RX distance may be determined by the RX WTRU based on, for example, geographic information carried in a TX WTUPSCCH / PSSCH transmission. The RX WTRU may determine the TX-RX distance based on, for example, TX WTRU geographic information (e.g., geographic coordinates or region ID) received in an SCI associated with a received PSSCH transmission. The RX WTRU may determine the TX-RX distance based on, for example, equivalent geographic information of the RX WTRU itself. The RX WTRU may determine the PSFCH resources based on, for example, a minimum communication range requirement. The minimum communication range requirement may be a distance within which one or more multicast transmission QoS requirements may be met. The minimum communication range (e.g., requirement) may be indicated in an SCI associated with a PSSCH transmission received by the RX WTRU. The RX WTRU may determine the PSFCH resources based on, for example, a reference signal received power (RSRP). The RSRP may include a PSCCH RSRP and / or a PSSCH RSRP. The RSRP may be measured, for example, by the RX WTRU. The RX WTRU may determine the PSFCH resources based on, for example, an area ID. The area ID may include an identification of a geographic area in which the RX WTRU is located. The RX WTRU may derive the area ID based on, for example, an area configuration from one or more higher layers. The RX WTRU may determine the PSFCH resources based on, for example, PSFCH power. The PSFCH power may include a PSFCH power level based on, for example, PSFCH power control. The RX WTRU may determine the PSFCH resources based on, for example, a path loss. The path loss may include a path loss between the TX WTRU and the RX WTRU. The RX WTRU may determine the path loss based on, for example, the PSCCH / PSSCH RSRP and / or the PSCCH / PSSCH transmit power, which may be indicated, for example, in the SCI associated with the received PSSCH transmission. The RX WTRU may determine the PSFCH resources based on, for example, HARQ information. The HARQ information may include, for example, an ACK or NACK (e.g., an ACK or NACK sent in a PSFCH) and / or the number of HARQ ACK / NACK bits.

[0154] The WTRU L1 ID may be a WTRU L1 source / destination ID that is based on, for example, the L2 WTRU ID or a randomly assigned L1 WTRU ID. The L2 WTRU ID may be unique for each WTRU. Using a portion of the L2 WTRU ID (e.g., 8 LSBs) of the L1 WTRU ID may result in collisions. The WTRU L1 ID used to determine the PSFCH resources in a multicast transmission may result in PSFCH resource overlap. For example, if the WTRU L1 ID is randomly assigned, PSFCH resource overlap may occur.

[0155] The WTRU may determine the PSFCH resources based on, for example, the WTRU L1 ID and the WTRU TX-RX distance. For example, the PSFCH resources may be associated with a specific WTRU TX-RX distance range. The RX WTRU may (for example, first) select one or more (for example, all) PSFCH resources associated with the TX-RX distance, and may (for example, subsequently) determine the PSFCH resources among the selected PSFCH resources based on, for example, the WTRU L1 ID. For example, the PSFCH frequency resources (for example, RB indices) may include a modulo function. The modulo function may be based on the WTRU L1 ID and the number of PSFCH resources associated with the TX-RX distance (for example, the total number of all such PSFCH resources). PSFCH resource overlap (for example, caused by WTRU L1 ID collisions) may be reduced, for example, by using a modulo function based on the WTRU L1 ID and the number of PSFCH resources associated with the TX-RX distance. In an example, the RX WTRU may be (pre)configured with a hash function. The hash function may be based on, for example, the WTRU L1 ID and the TX-RX distance.

[0156] The WTRU may determine the PSFCH resources based on, for example, the WTRU TX-RX distance, the minimum communication range requirement and / or the WTRU L1 ID. For example, the PSFCH resources may be associated with a ratio of the WTRU TX-RX distance to the minimum communication range requirement. Multiple PSFCH resources may be associated with multiple RX WTRUs within a distance relative to the minimum communication range (e.g., requirement). The RX WTRU may select the PSFCH resources based on, for example, the WTRU L1 ID of the RX WTRU. In an example, the RX WTRU may be (pre)configured with a hash function. The hash function may be based on, for example, the WTRU L1 ID and the ratio of the WTRU TX-RX distance to the received minimum communication range (e.g., requirement).

[0157] The WTRU may determine the PSFCH resources using a hash function based on, for example, the WTRU source ID and one or more of, for example, RSRP, area ID, PSFCH power level, path loss and / or HARQ information.

[0158] The WTRU may determine the PSFCH time and frequency resources. The WTRU may determine the PSFCH resources and may use the PSFCH resources to feedback the HARQ status of (e.g., one) PSSCH / PSCCH (e.g., one PSSCH / PSCCH transmission). The WTRU may determine the PSFCH resources, for example, based on one or more of the following. The WTRU may determine the PSFCH resources based on, for example, the time and frequency index of the PSSCH / PSCCH. The WTRU may determine the PSFCH resources based on, for example, the broadcast type (e.g., unicast or multicast). The WTRU may determine the PSFCH resources based on, for example, the HARQ feedback type for multicast (e.g., NACK-based feedback or ACK / NACK-based feedback). The WTRU may determine the PSFCH resources based on, for example, a PSFCH hopping pattern. For example, the WTRU may be configured to have a hopping pattern with respect to the PSFCH frequency resources. For example, the frequency position of the PSFCH resources associated with the PSSCH / PSCCH may hop from a first time slot having the PSFCH resources to a second time slot having the PSFCH resources. The WTRU may determine the PSFCH resources based on, for example, the first and / or last subchannel / RB of the PSFCH resources in the resource pool. The WTRU may determine the PSFCH resources based on, for example, the duration and / or bandwidth of the PSSCH / PSCCH transmission.

[0159] Figure 4 Example PSFCH to PSSCH / PSCCH mappings based on broadcast type and HARQ-based options are depicted. The WTRU may determine the PSFCH resources for a PSSCH / PSCCH transmission based on, for example, the broadcast type and / or HARQ feedback options for the PSSCH / PSCCH transmission. For example, the WTRU may be (pre)configured with one or more of the following mappings between the time and frequency indexes of the PSSCH / PSCCH and the associated PSFCH resources in a resource pool. The WTRU may be (pre)configured with the time and frequency indexes of the PSSCH / PSCCH and the PSFCH resource mapping for unicast transmissions. The WTRU may be (pre)configured with the PSFCH resources for NACK-based HARQ feedback multicast transmissions and the time and frequency index mapping of the PSSCH / PSCCH. The WTRU may be (pre)configured with the PSFCH resources for ACK / NACK-based HARQ feedback multicast transmissions and the time and frequency index mapping of the PSSCH / PSCCH.

[0160] The WTRU (e.g., after decoding the PSSCH / PSCCH) may determine the PSFCH resources for the associated PSSCH / PSCCH, e.g., based on the (pre-)configured mapping. Figure 4 As shown), if the PSSCH / PSCCH is multicast, the WTRU can determine the PSFCH resources for the PSSCH / PSCCH based on, for example, the broadcast type and the HARQ feedback option.

[0161] In an example, the WTRU may determine a PSFCH resource for a PSSCH / PSCCH transmission based on, for example, the data QoS. The WTRU may determine (e.g., after decoding the PSCCH / PSSCH) a PSFCH resource for an associated PSCCH / PSSCH, for example, based on a (pre)configured mapping. For example, the WTRU may determine a PSFCH resource that is located at the lowest frequency position in a resource pool and has a maximum number of PSFCH resources for data, where the data is, for example, associated with a priority that is above a threshold (e.g., a preconfigured and / or predetermined priority threshold).

[0162] In an example, the WTRU may determine the frequency size of the PSFCH resource, for example, based on the size of the associated PSSCH / PSCCH resource. For example, the WTRU may be (pre)configured in a resource pool with a mapping between the time and frequency index of the PSSCH / PSCCH resource and the PSFCH resource, which may include one or more RBs. The WTRU may (e.g., then) determine the size (e.g., frequency size) of the PSFCH resource for feedback of the associated PSSCH / PSCCH resource based on, for example, the number of subchannels used for PSSCH / PSCCH transmissions. For example, if the PSSCH / PSCCH resource occupies one subchannel, the PSFCH resource may include one RB. For example, if the PSSCH / PSCCH resource occupies two subchannels, the WTRU may determine that the corresponding PSFCH transmission occupies two RBs (e.g., the PSFCH resource may include two RBs).

[0163] Figure 5An example of a WTRU determining PSFCH resources in an ACK / NACK based feedback multicast is depicted. The WTRU may determine the PSFCH resources for the associated PSSCH / PSCCH for the ACK / NACK based feedback multicast, for example, based on one or more of the following. The WTRU may determine the PSFCH resources for the associated PSSCH / PSCCH for the ACK / NACK based feedback multicast based on, for example, an ID of the WTRU (e.g., an ID). In an example, the WTRU may use the IDs of the WTRUs within the group to determine the order of the WTRUs in the group and select PSFCH resources in the set of PSFCH resources for the group. In an example, for example, in the PSFCH resource determination, the group leader may use, for example, one of the IDs of the WTRUs (e.g., L1, L2, or upper layer IDs) to inform the WTRUs of their order in the group. The order of the WTRUs in the group may be communicated to the WTRUs, for example, via PC5-RRC. The WTRU may determine the PSFCH resources of the associated PSSCH / PSCCH for the ACK / NACK based feedback multicast based on, for example, the size of the PSFCH resources of the group. The WTRU may determine the PSFCH resources of the associated PSSCH / PSCCH for the ACK / NACK based feedback multicast based on, for example, the number of WTRUs in the group.

[0164] The WTRU may determine the PSFCH resources, for example, in a time order, a frequency order, and / or a code order.

[0165] In the example, (for example, Figure 5 As shown), a group of three (3) Rx WTRUs may send an ACK / NACK PSFCH for each PSSCH / PSCCH transmission. The (e.g., each) sub-channel resource used for the PSSCH / PSCCH may be mapped to two (2) PRBs, for example, to send an ACK or NACK status. For example, the (e.g., each) RB may be used by (e.g., one) WTRU for (e.g., one) PSFCH transmission. The first WTRU and the second WTRU may feedback the HARQ status, for example, for a PSSCH / PSCCH transmission in one sub-channel. One or more WTRUs (e.g., all WTRUs) may feedback the HARQ status of the PSSCH / PSCCH, for example, for a PSSCH / PSCCH transmission in two or more sub-channels.

[0166] The WTRU may transmit the PSFCH. The WTRU may, for example, use (e.g., Figure 6 The shared PSFCH resource pool (shown) transmits the PSFCH in one or more (eg, determined) PSFCH resources. Figure 6 An example of WTRU PSFCH resource determination and transmission for HARQ that may use a shared resource pool is shown.

[0167] The WTRU may perform PSFCH sensing and transmission. The WTRU may perform PSFCH detection and transmission in the determined PSFCH subchannel within the HARQ timing (e.g., as Figure 7 shown). Figure 7 Examples of WTRU PSFCH sensing and transmission are shown, for example, for PSFCH occupying 1, 2, and 6 symbols.

[0168] PSFCH sensing and transmission may include, for example, one or more of the following. The WTRU may measure the received power (e.g., RSSI) in a subchannel over a plurality of CP-OFDM symbols at the beginning of a time slot (e.g., the first time slot) of the HARQ timing (e.g., in a time slot of the determined HARQ timing). In one example, Figure 7 As shown, the symbol may be symbol 0-5.

[0169] For example, if the received power is below a (pre-)configured threshold, the WTRU may transmit the PSFCH in the subchannel. For example, if the received power is not below the threshold, the WTRU may decode the SCI and obtain the slot format and / or PSFCH information.

[0170] The WTRU may determine whether there is a PSFCH transmission multiplexed with the PSSCH in a timeslot based on, for example, a PSFCH presence indicator and / or a timeslot format indicator in the SCI. For example, if the PSFCH presence is detected (e.g., the PSFCH transmission does not overlap with the PSSCH portion of the timeslot), the WTRU may transmit the PSFCH. For example, if the PSFCH presence is not detected, the WTRU may evaluate the next subchannel selected for the PSFCH transmission.

[0171] The WTRU may process the next timeslot (eg, if the HARQ timing includes more than one timeslot), which may occur, for example, if one or more (eg, all) subchannels selected for PSFCH transmission in that timeslot are occupied by PSSCH.

[0172] The WTRU may (e.g., if no selected PSFCH subchannel is available within the HARQ timing) apply extended HARQ timing (e.g., assuming that the extended HARQ timing is within the QoS latency requirements) and switch to a dedicated PSFCH resource pool to select a PSFCH resource (e.g., as disclosed herein).

[0173] For example, if no extended HARQ timing is available for low latency TB transmission, the WTRU may discard the HARQ information. For example, the WTRU may buffer the HARQ ACK / NACK information, switch to Mode 1 transmission, and send the HARQ information with the WTRU PHY ID and / or link ID information in the PUCCH or PUSCH.

[0174] HARQ transmissions may be multiplexed to different source WTRUs. The WTRU may support multiple active unicast / multicast transmissions. The WTRU may (e.g., determine) to transmit more than one PSFCH in a timeslot carrying HARQ ACK / NACK corresponding to PSSCH received from different source WTRUs, e.g., based on the HARQ timing associated with each received TB transmission. The WTRU may multiplex multiple PSFCHs to different source WTRUs based on, for example, one or more of CDM, FDM, and / or TDM.

[0175] The WTRU may multiplex multiple PSFCHs to different source WTRUs, e.g., based on CDM. The WTRU may (e.g., determine) to apply the same time and frequency resources (e.g., one or more same RBs at the same symbol in a slot) to one or more (e.g., all) PSFCH transmissions. The WTRU may determine different HARQ ACK / NACK sequences (e.g., using a cyclic shift index), e.g., based on a source ID or link ID associated with a PSFCH (e.g., each PSFCH).

[0176] The WTRU may multiplex multiple PSFCHs to different source WTRUs, for example based on FDM. The WTRU may (e.g., determine) to transmit the PSFCHs in different frequency allocations (e.g., subchannels or RBs). The frequency allocation may be based on, for example, a source ID or link ID associated with the PSFCH (e.g., each PSFCH).

[0177] The WTRU may multiplex multiple PSFCHs to different source WTRUs, for example based on TDM. The WTRU may (e.g., determine) to transmit the PSFCHs at different symbols within a time slot. For example, the symbol positions may be determined based on a source ID or link ID associated with the PSFCH (e.g., each PSFCH).

[0178] The WTRU may (e.g., determine) adjust the time slots of one or more PSFCH transmissions (e.g., each PSFCH transmission) and align them over multiple time slots. The WTRU may perform TDM of multiple PSFCH transmissions over multiple time slots (e.g., assuming that each PSFCH transmission meets the associated HARQ timing).

[0179] HARQ transmissions may be multiplexed to the same source WTRU. A WTRU may support multiple active service applications with the same WTRU during a unicast transmission. For example, HARQ timing associated with TBs belonging to service applications with different QoS requirements (e.g., PDBs) may overlap even if the associated PSSCH transmissions are received at different times. A WTRU may (e.g., determine) to transmit, in a timeslot, for example, one PSFCH or multiple PSFCHs carrying HARQ ACK / NACK for multiple TBs received from a source WTRU, where each of the multiple PSFCHs may carry a HARQ ACK / NACK corresponding to the received TB.

[0180] The WTRU may (eg, determine) to transmit a PSFCH carrying HARQ ACK / NACK for multiple TBs received from the source WTRU. The WTRU may be (pre-)configured to multiplex and / or bundle the HARQ ACK / NACK information in a PSFCH transmission.

[0181] The WTRU may (e.g., determine) to transmit multiple PSFCHs in one time slot, where each of the multiple PSFCHs may carry a HARQ ACK / NACK corresponding to a received TB. The WTRU may multiplex different PSFCHs to the same source WTRU based on, for example, one or more of CDM, FDM, and / or TDM.

[0182] The WTRU may multiplex different PSFCHs to the same source WTRU, e.g., based on CDM. The WTRU may (e.g., determine) to apply (e.g., the same) time and frequency resources (e.g., one or more same RBs at the same symbol in a slot) to one or more (e.g., all) PSFCH transmissions. The WTRU may determine different HARQ ACK / NACK sequences (e.g., using a cyclic shift index), e.g., based on a HARQ process ID and / or a source ID associated with a PSFCH (e.g., each PSFCH).

[0183] The WTRU may multiplex different PSFCHs to the same source WTRU, for example based on FDM. The WTRU may (e.g., determine) to transmit multiple PSFCHs in different frequency allocations (e.g., subchannels or RBs). The frequency allocation may be based on, for example, a HARQ process ID and / or a source ID associated with the PSFCH (e.g., each PSFCH).

[0184] The WTRU may multiplex different PSFCHs to the same source WTRU, for example based on TDM. The WTRU may (e.g., determine) to transmit the PSFCH at different symbols within a time slot. The symbol position may be determined based on, for example, a HARQ process ID and / or a source ID associated with the PSFCH (e.g., each PSFCH).

[0185] Prioritization of multiple PSFCHs within a timeslot may be performed. The WTRU may independently determine the power of a PSFCH transmission (e.g., each PSFCH transmission) based on, for example, power control parameters of the PSFCH (e.g., each PSFCH). For example, these parameters may vary based on the QoS requirements of the data associated with the PSFCH transmission. For example, if the total power of the transmission timeslot exceeds the configured limit, the WTRU may ensure the power of the PSFCH associated with the highest QoS requirement (e.g., PPPP and PPPR) and may discard the PSFCH with a lower QoS requirement.

[0186] The WTRU may monitor the PSFCH. The WTRU may monitor the HARQ transmission. The WTRU may monitor the HARQ transmission according to the HARQ timing associated with the PSSCH transmission, for example, using a shared PSFCH resource pool. Figure 8 shown).

[0187] Figure 8 An example of WTRU PSFCH resource determination and monitoring for HARQ that may use a shared resource pool is shown. The WTRU may perform blind detection on one or more (e.g., all) monitored PSFCH resources based on, for example, a HARQ ACK / NACK sequence for a sequence-based PSFCH or a DM-RS configuration for a PSFCH carrying payload. The WTRU may perform blind detection between (one or more) PSFCH frequency resources (e.g., subchannels or RBs) associated with the PSSCH. The WTRU may start blind detection, for example, from the subchannel and RB associated with the WTRU's L1 source ID. The WTRU may start AGC, for example, at the beginning of the PSFCH resource, which may include, for example, one or more consecutive symbols (e.g., such as immediately before a Tx / Rx switching symbol at the end of a timeslot). Figure 2 For example, if (eg, when) PSFCH detection is performed in a timeslot, the WTRU may not receive sensing information about the timeslot and may exclude the timeslot from the sensing process.

[0188] The WTRU may not detect a transmission at the monitored HARQ timing (e.g., neither a HARQ ACK transmission nor a NACK transmission), which may be referred to as discontinuous transmission (DTX). For example, if DTX is detected, the WTRU may perform retransmissions and extended monitoring. For example, the WTRU may detect DTX within the associated HARQ timing (e.g., no PSFCH detection) for one or more of the following reasons. For example, if an associated PSCCH / PSSCH is received and a PSFCH is sent due to a PSFCH detection / decoding failure, the WTRU may detect DTX within the associated HARQ timing. For example, if an associated PSCCH / PSSCH is received and a PSFCH is not sent (e.g., due to a mode 2 resource acquisition failure, such as when a shared PSFCH resource pool is used), the WTRU may detect DTX within the associated HARQ timing. For example, if an associated PSCCH / PSSCH is not received, for example, due to a PSCCH detection / decoding failure, the WTRU may detect DTX within the associated HARQ timing.

[0189] The WTRU may determine that the DTX indicates a failure of the associated PSCCH decoding (eg, when using a dedicated PSFCH resource pool). For example, if the WTRU receives a DTX using a dedicated PSFCH resource pool, the WTRU may perform a retransmission of the TB (eg, using systematic bits).

[0190] For example, if the channel busy ratio (CBR) is above a (pre) configured threshold and / or the extended HARQ timing is within the QoS latency requirements, the WTRU may (e.g., determine) to extend the HARQ timing by a (pre) configured time period (e.g., when using a shared PSFCH resource pool).

[0191] The WTRU may (e.g., be (pre)configured to) switch to a dedicated PSFCH resource pool for PSFCH transmissions associated with extended HARQ timing. The source and / or destination WTRU may determine the PSFCH resources in the dedicated PSFCH resource pool, for example, as disclosed herein. For example, if no HARQ transmission is received at the HARQ timing and the extended HARQ timing, the WTRU may consider the TB to be correctly received. The WTRU may (e.g., subsequently) refresh the HARQ data buffer. The WTRU may (e.g., be (pre)configured to) switch to Mode 1 for HARQ PSFCH transmissions. The WTRU may hold the data in the buffer until the TB delay budget is exceeded.

[0192] PSSCH / PSCCH transmission and reception may be performed in a PSFCH timeslot. The WTRU may determine whether a PSSCH / PSCCH transmission of the WTRU conflicts with a PSFCH transmission. For example, the WTRU may perform sensing to determine whether one or more PSFCH transmissions conflict with a PSSCH / PSCCH transmission of the WTRU. The WTRU may be (pre) configured (e.g., explicitly) with a mapping between the time and frequency indexes of the PSSCH / PSCCH and the PSFCH resources in a resource pool. The WTRU may determine whether there is a PSFCH transmission on the PSSCH / PSCCH resources of the WTRU, which may be performed, for example, by monitoring (e.g., all) PSSCH / PSCCHs with associated PSFCH resources that overlap with the PSSCH / PSCCH resources of the WTRU for transmission. For example, the WTRU may determine that the PSSCH / PSCCH transmission of the WTRU may conflict with one or more PSFCH transmissions if one or more of the following conditions are met.

[0193] For example, if the WTRU successfully decodes a PSCCH / PSSCH with an associated PSFCH that overlaps with the WTRU's PSSCH / PSCCH transmission, the WTRU may determine that the WTRU's PSSCH / PSCCH transmission may conflict with one or more PSFCH transmissions. For example, if the RSRP / RSRQ / RSSI of the PSSCH / PSCCH is greater than a threshold, the WTRU may determine that the WTRU's PSSCH / PSCCH transmission may conflict with one or more PSFCH transmissions. The threshold may be (pre)configured.

[0194] The WTRU may perform rate matching / puncturing and / or may adjust the modulation and coding scheme (MCS) for transmission. In one example, for example, if the WTRU detects a possible collision, the WTRU may perform rate matching / puncturing and / or may adjust the MCS for transmission. For example, if the WTRU must transmit PSSCH / PSCCH and transmit / receive PSFCH in the same time slot, the WTRU may perform rate matching / puncturing and / or may adjust the MCS for transmission. For example, if the WTRU needs to avoid a collision between the PSSCH / PSCCH transmission of the WTRU and (one or more) PSFCH transmissions from one or more other WTRUs, the WTRU may perform rate matching / puncturing and / or may adjust the MCS of the PSSCH / PSCCH. For example, if the WTRU must transmit PSSCH / PSCCH and receive PSFCH in the same time slot, the WTRU may perform rate matching / puncturing and / or may adjust the MCS of the PSSCH / PSCCH. For example, if the WTRU sends PSSCH / PSCCH in a PSFCH slot before a scheduled PSFCH reception, the WTRU may use (one or more) symbols between the PSSCH / PSCCH symbol and the PSFCH symbol for TX / RX switching and / or AGC. For example, by using one or more symbols between the PSSCH / PSCCH symbol and the PSFCH symbol for the TX / RX switching and / or the AGC, the PSSCH / PSCCH transmission duration may be reduced (e.g., by one symbol). For example, if the WTRU must transmit PSSCH / PSCCH and PSFCH in the same slot, the WTRU may perform rate matching / puncturing and / or may adjust the MCS of the PSSCH / PSCCH. If the WTRU transmits PSSCH / PSCCH in a PSFCH slot before a scheduled PSFCH transmission, the WTRU may use one or more symbols between the two transmissions for the gap period, for example, for frequency retuning. For example, by using one or more symbols between the two transmissions for the gap period, the PSSCH / PSCCH transmission duration may be reduced.

[0195] The WTRU may indicate (e.g., explicitly indicate) rate matching / puncturing resources in an SCI, for example, to support a receiver WTRU in decoding a TB. (One or more) rate matching / puncturing symbols of a PSSCH / PSCCH (e.g., the last P symbols of a PSSCH / PSCCH) may be indicated, for example, in an associated SCI. P may have one or more candidate values. One or more of the values ​​may be indicated in the SCI. For example, the number of symbols used for PSSCH / PSCCH in a timeslot may be indicated in the associated SCI. The Rx WTRU may (e.g., be configured to) assume that symbols that potentially overlap with PSFCH resources are rate matched and / or punctured. For example, if the Rx WTRU assumes that symbols that overlap with PSFCH resources are rate matched and / or punctured, then (one or more) rate matched and / or punctured symbols may not be indicated in the associated SCI.

[0196] For example, if the WTRU transmits a PSSCH / PSCCH in a PSFCH timeslot prior to a scheduled PSFCH reception, the WTRU may determine whether it may (e.g., explicitly) indicate rate matching / puncturing information in the SCI (e.g., based on the WTRU ID and / or link ID associated with the PSSCH / PSCCH and PSFCH). The WTRU ID and / or link ID associated with the PSFCH may be the ID of the PSSCH / PSCCH transmission corresponding to the HARQ ACK / NACK carried in the PSFCH. For example, if the WTRU destination ID associated with the PSSCH / PSCCH transmission and the PSFCH reception is the same, the WTRU may (e.g., determine) not to include rate matching / puncturing information in the SCI. For example, if the IDs match, the RX WTRU of the PSSCH / PSCCH transmission and the TX WTRU of the PSFCH transmission may be the same WTRU. For example, if the WTRU is the RX WTRU for the PSSCH / PSCCH transmission and the TX WTRU for the PSFCH transmission, then the WTRU may be aware (eg, implicitly aware) of the rate matching / puncturing.

[0197] The WTRU may determine the transmission duration of the PSSCH / PSCCH in a time slot with PSFCH resources based on, for example, a subchannel index of the PSSCH / PSCCH and / or a set of subchannels dedicated to PSFCH in each time slot. For example, the WTRU may be configured to have two or more of: a full-slot PSSCH / PSCCH or a PSSCH / PSCCH occupying N (e.g., N<14) first symbols. In one example, the WTRU may be configured to have a PSSCH / PSCCH transmission occupying 11 first symbols, for example, to reserve the remaining symbols in the time slot for HARQ operations. The WTRU may (e.g., determine) to transmit a full-slot PSSCH / PSCCH, for example, in a subchannel index without (pre-)configured PSFCH resources, or may, for example, transmit a partial (e.g., non-full) slot PSSCH / PSCCH (e.g., N=11 symbols) in a subchannel with at least one (pre-)configured PSFCH resource.

[0198] For example, if the WTRU receives a PSSCH / PSCCH in a PSSSH timeslot prior to a scheduled PSFCH reception, the WTRU may use the symbol(s) between the PSSSH / PSCCH and PSFCH symbols for AGC reconvergence. For example, if the PSSCH / PSCCH and PSFCH are from different WTRUs, AGC reconvergence may be performed prior to the PSFCH. For example, if the PSSCH / PSCH and PSFCH have a frequency offset greater than a threshold, AGC reconvergence may be performed prior to the PSFCH.

[0199] The WTRU may determine whether AGC reconvergence is required based on, for example, the link ID and / or the WTRU ID. In one example, the WTRU may compare the WTRU source ID decoded in the PSCCH at the beginning of the PSFCH slot with the source ID associated with the PSFCH transmission. For example, if the source IDs are the same (e.g., when the transmissions are from the same WTRU), the WTRU may not use any symbols for AGC reconvergence. For example, if the source IDs are different (e.g., when the transmissions are from different WTRUs), the WTRU may use the symbol(s) before the PSFCH reception for AGC reconvergence (e.g., based on the PSFCH frequency resource allocation). The WTRU may use the symbol(s) for AGC reconvergence to puncture the received PSSCH / PSCCH transmission.

[0200] The WTRU may perform (e.g., determine to perform) AGC reconvergence, for example, based on a PSSCH frequency assignment decoded in the SCI at the beginning of a PSFCH slot and / or a PSFCH frequency assignment. The PSFCH frequency assignment may be determined, for example, based on an association with a corresponding PSSCH / PSCCH transmission. For example, if the difference between the PSSCH and PSFCH frequency assignments exceeds a threshold, the WTRU may (e.g., determine to perform AGC reconvergence. For example, if the WTRU determines and / or performs AGC reconvergence, the WTRU may puncture the received PSSCH / PSCCH.

[0201] The WTRU may manage one or more HARQ processes. For example, the WTRU may perform HARQ process management. The HARQ process management may include, for example, flushing the HARQ buffer and / or determining which HARQ process to release.

[0202] The WTRU may (e.g., determine) to flush the HARQ buffer. The WTRU may (e.g., determine) to flush the HARQ buffer based on, for example, a (pre)configured period. For example, the WTRU may release the HARQ process after a (pre)configured period. The WTRU may determine which HARQ process to release based on, for example, one or more of the following. The WTRU may determine which HARQ process to release based on, for example, the QoS of the received TB. For example, the WTRU may (e.g., determine) to release the HARQ process of the TB based on, for example, a priority indicated in the SCI of the TB. The WTRU may be configured to have a mapping between priorities and time periods, for example, so as to keep the TB in the buffer (e.g., when the TB is not successfully decoded). For example, even if the WTRU cannot (e.g., successfully) decode the TB, the WTRU may release the HARQ process (e.g., after a configured period). The WTRU may determine which HARQ process to release based on, for example, the broadcast type and / or the multicast HARQ feedback option. In one example, the WTRU may be configured to have different periods, for example, to maintain a TB in the HARQ buffer for (e.g., each) playout type and / or for (e.g., each) HARQ feedback option (e.g., NACK-based feedback or ACK / NACK-based feedback). The WTRU may determine which HARQ process to release based on, for example, the availability of reserved resources for the same TB in the SCI. In one example, for example, if the SCI indicates that there are no resource reservations for the same TB, the WTRU may (e.g., determine) to release the HARQ process. The WTRU may determine which HARQ process to release based on, for example, a HARQ feedback enable / disable indication in the SCI. In one example, for example, if the WTRU receives a HARQ feedback disable indication for a previous transmission and / or a HARQ feedback enable indication for a previous transmission of the same TB in the SCI, the WTRU may release the HARQ buffer.

[0203] For example, if the WTRU receives a high priority transmission and / or the WTRU has no remaining HARQ transmission / reception for the HARQ process, the WTRU may release the HARQ process (e.g., a low priority HARQ process). A priority may be assigned to (e.g., each) HARQ process. A high priority transmission may have a higher priority than the released HARQ process (e.g., a low priority HARQ process). For example, the WTRU may (e.g., determine) release the HARQ process to receive another TB. The WTRU may determine which HARQ process to release based on, for example, one or more of the following. The WTRU may determine which HARQ process to release based on, for example, the QoS of the TBs stored in the HARQ process. For example, the WTRU may (e.g., determine) release the HARQ process associated with the lowest priority TB. The WTRU may determine which HARQ process to release based on, for example, the TB size. In one example, the WTRU may (e.g., determine) release the HARQ process associated with the largest or smallest TB. The WTRU may determine which HARQ process to release based on, for example, the broadcast type of the HARQ process. The WTRU may (e.g., determine) to release a HARQ process associated with a playout type, such as unicast, groupcast, or broadcast. In one example, the WTRU may (e.g., determine) to release a HARQ process associated with a broadcast TB, for example, if the WTRU is able to (e.g., is) decoding another blind retransmission of the released TB. The WTRU may determine which HARQ process to release based on, for example, a HARQ transmission order of the TB. The HARQ transmission order may include two or more HARQ processes. The HARQ transmission order may indicate a transmission order of the two or more HARQ processes. In one example, the WTRU may (e.g., determine) to release a HARQ process associated with the highest or lowest HARQ process in the HARQ transmission order.

[0204] Although the above features and elements are described in particular combinations, each feature or element may be used alone without the other features and elements of the preferred embodiments, or in various combinations with or without the other features and elements.

[0205] Although the implementation described herein may consider 3GPP specific protocols, it should be understood that the implementation described herein is not limited to this scenario and may be applicable to other wireless systems.

[0206] The processes described above may be implemented in a computer program, software, and / or firmware embedded in a computer-readable medium and executed by a computer and / or a processor. Examples of computer-readable media include, but are not limited to, electronic signals (transmitted via wired and / or wireless connections) and / or computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, read-only memory (ROM), random access memory (RAM), registers, buffer memory, semiconductor storage devices, magnetic media such as, but not limited to, internal hard disks and removable disks, magneto-optical media, and / or optical media such as CD-ROM disks and / or digital versatile disks (DVDs). A processor associated with the software may be used to implement a radio frequency transceiver used in a WTRU, a terminal, a base station, an RNC, and / or any host computer.

Claims

1. A wireless transmit / receive unit (WTRU), the WTRU comprising: A processor configured to: Determining a set of PSFCH resources within an allocation of PSFCH resources; as well as A PSFCH resource within the PSFCH resource set is selected, wherein the selection of the PSFCH resource is based at least on an L1 source identifier (ID) indicated in sidelink control information (SCI) and a broadcast type indicated in the SCI, and wherein, if the broadcast type is multicast, the selection of the PSFCH resource is further based on a WTRU ID.

2. The WTRU of claim 1 , wherein the processor is further configured to: receiving the allocation regarding the physical sidelink feedback channel (PSFCH) resources; and The SCI is received, wherein the SCI is associated with a physical sidelink shared channel (PSSCH) transmission.

3. The WTRU of claim 1 , wherein the selection is also based on time slot information.

4. The WTRU of claim 2, wherein the processor is further configured to send HARQ acknowledgement / negative acknowledgement (ACK / NACK) information associated with the PSSCH transmission on the selected PSFCH resource.

5. The WTRU of claim 1 , wherein the set of PSFCH resources within the allocation of PSFCH resources is determined based on a lowest PSSCH subchannel index and a PSSCH timeslot number.

6. The WTRU of claim 2, wherein for the PSFCH resource, there is a mapping between each subchannel in a PSSCH resource pool and one PSFCH resource in the allocation with respect to PSFCH resources.

7. The WTRU of claim 1, wherein the PSFCH resource set is determined based on a selection of a PSFCH time slot.

8. The WTRU of claim 7, wherein the selection of the PSFCH time slot is based on a PSSCH time slot and a preconfigured PSFCH periodicity.

9. A method associated with wireless communication, the method comprising: Determining a set of PSFCH resources within an allocation of PSFCH resources; as well as A PSFCH resource within the PSFCH resource set is selected, wherein the selection of the PSFCH resource is based at least on an L1 source identifier (ID) indicated in sidelink control information (SCI) and a broadcast type indicated in the SCI, and wherein, if the broadcast type is multicast, the selection of the PSFCH resource is further based on a WTRU ID.

10. The method according to claim 9, wherein the method further comprises: receiving the allocation regarding the physical sidelink feedback channel (PSFCH) resources; as well as The SCI is received, wherein the SCI is associated with a physical sidelink shared channel (PSSCH) transmission. The method of claim 9 , wherein the selecting is further based on time slot information.

12. The method according to claim 10, further comprising: HARQ acknowledgement / negative acknowledgement (ACK / NACK) information associated with the PSSCH transmission is sent on the selected PSFCH resource.

13. The method according to claim 9, wherein: The set of PSFCH resources within the allocation of PSFCH resources is determined based on a lowest PSSCH subchannel index and a PSSCH slot number.

14. The method according to claim 10, wherein: For the PSFCH resource, there is a mapping between each subchannel in the PSSCH resource pool and one PSFCH resource in the allocation regarding the PSFCH resource.

15. The method according to claim 9, wherein: The PSFCH resource set is determined based on the selection of the PSFCH time slot.

16. The method according to claim 15, wherein: The selection of the PSFCH time slot is based on a PSSCH time slot and a preconfigured PSFCH periodicity.

17. A wireless transmit / receive unit (WTRU), the WTRU comprising: A processor configured to: Determining a set of PSFCH resources within an allocation of PSFCH resources; as well as A PSFCH resource within the set of PSFCH resources is selected, wherein the selection of the PSFCH resource is based on at least a L1 source identifier (ID) and a WTRU ID indicated in sidelink control information (SCI).

18. The WTRU of claim 17, wherein the processor is further configured to receive the SCI, wherein the SCI is associated with a physical sidelink shared channel (PSSCH) transmission, and wherein the SCI indicates a broadcast type of multicast.

19. The WTRU of claim 18, wherein the selection of the PSFCH resource based on the WTRU ID is based on an SCI indication that the playout type is multicast.

20. A first wireless transmit / receive unit (WTRU), the WTRU comprising: A processor configured to: selecting a transport block timing from a set of timings, wherein the selection is based on one or more of: processing capability, sidelink subcarrier spacing, priority information associated with the transport block, or channel busyness; sending one or more of the priority information or the channel busy rate to a second WTRU; and Based on the timing, transmissions from the second WTRU are monitored.

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