Method for power saving listening and resource allocation

Abstract

A first wireless transmit / receive unit (WTRU) can receive sidelink control information (SCI) from a second WTRU, the SCI including first information indicating whether a resource is reserved by the second WTRU, and second information indicating whether the second WTRU is power saving or non-power saving. The first WTRU is capable of measuring a reference signal received power (RSRP) of a signal transmitted by the second WTRU. If the first information indicates that the resource is not reserved by the second WTRU, the first WTRU can add the resource to a set of available resources. If resources are reserved, the WTRU can set an RSRP threshold to a first setting or a second threshold based on a power saving mode of the second WTRU. If the measured RSRP is less than a selected RSRP threshold, the first WTRU can add the resource to the set of available resources.

Description

[0001] This divisional application is a divisional application with a filing date of February 12, 2021, application number 202180019025.4, and invention name “Method for power saving listening and resource allocation”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims the benefit of the following U.S. provisional applications: No. 62 / 975,489 filed on February 12, 2020, No. 63 / 061,707 filed on August 5, 2020, No. 63 / 091,662 filed on October 14, 2020, and No. 63 / 136,530 filed on January 12, 2021, the contents of which are incorporated herein by reference. Background Art

[0004] During vehicle-to-everything (V2X) operations, vehicle communications may include multiple wireless transmit / receive units (WTRUs) (e.g., vehicles and / or wireless devices with wireless communication capabilities) communicating directly with each other over an air interface. In the case of in-coverage, the WTRU may receive assistance from the network to start transmitting and receiving V2X messages. In the case of out-of-coverage, the WTRU may use one or more pre-configured parameters to start transmitting and receiving V2X messages.

[0005] V2X communications are supported in, for example, Long Term Evolution (LTE) and New Radio (NR), and may include, but are not limited to, any of the following: vehicle-to-vehicle (V2V) communications, in which vehicle WTRUs may communicate directly with each other; vehicle-to-infrastructure (V2I) communications, in which vehicle WTRUs may communicate with roadside units (RSUs) and / or evolved Node Bs (eNBs); vehicle-to-network (V2N) communications, enabling vehicle WTRUs to communicate with a core network; and / or vehicle-to-pedestrian (V2P) communications, in which vehicle WTRUs may communicate with WTRUs having special conditions (e.g., low battery capacity or low power). Summary of the invention

[0006] Systems and methods may be used for power save listening and resource allocation for sidelink (SL) communications. A first wireless transmit / receive unit (WTRU) may receive side link control information (SCI) from a second WTRU. The SCI may include first information indicating, for each resource in a resource pool, whether the resource is reserved by the second WTRU, and second information indicating whether the second WTRU is a power save WTRU or a non-power save WTRU. The first WTRU may be able to measure a reference signal received power (RSRP) of a signal transmitted by the second WTRU. The first WTRU may perform resource selection by the following steps, for each resource in the resource pool: if the first information indicates that the resource is not reserved by the second WTRU, adding the resource to a set of available resources. For each resource in the resource pool, if the first information indicates that the resource is reserved by the second WTRU: if the second information indicates that the second WTRU is a power saving WTRU, the WTRU may set a selected RSRP threshold or increment to a first set of RSRP thresholds or increments for determining the availability of the resource; and if the second information indicates that the second WTRU is a non-power saving WTRU, the first WTRU may set the selected RSRP threshold or increment to a second set of RSRP thresholds or increments for determining the availability of the resource. In the event that the measured RSRP is less than the selected RSRP threshold, the first WTRU may add the resource to the set of available resources. The first WTRU may select a resource from the set of available resources for transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] A more detailed understanding may be obtained from the following description given by way of example in conjunction with the accompanying drawings, in which like reference numerals indicate like elements, and in which:

[0008] Figure 1A is a system diagram illustrating an exemplary communication system in which one or more disclosed embodiments may be implemented;

[0009] Figure 1B It is shown that according to one embodiment, Figure 1A A system diagram of an exemplary wireless transmit / receive unit (WTRU) for use within the communication system is shown;

[0010] Figure 1C It is shown that according to one embodiment, Figure 1A A system diagram of an exemplary radio access network (RAN) and an exemplary core network (CN) used within the illustrated communication system;

[0011] Figure 1D It is shown that according to one embodiment, Figure 1AA system diagram of another exemplary RAN and another exemplary CN used in the communication system shown;

[0012] Figure 2 A signaling diagram illustrating an exemplary link establishment process;

[0013] Figure 3 A timing diagram showing exemplary listening windows and sub-windows that may be used in a long-term partial listening process;

[0014] Figure 4 A timing diagram showing exemplary listening windows and sub-windows that may be used in a short-term partial listening process;

[0015] Figure 5 A timing diagram showing another example of a listening window and sub-window that may be used in a short-term partial listening process;

[0016] Figure 6 A timing diagram illustrating an exemplary process for a WTRU to determine a set of resources on which to perform sensing based on a set of reserved resources;

[0017] Figure 7 A timing diagram showing exemplary listening windows, sub-windows, and sub-channels that may be used in a listening process;

[0018] Figure 8 A flow chart illustrating an exemplary resource allocation process that may be performed by a first WTRU in order for the first WTRU to determine which resources to use for sidelink communications;

[0019] Fig. 9 A timing diagram illustrating an exemplary resource selection process;

[0020] Fig.10 A timing diagram illustrating an example of a resource selection timing process for a transport block (TB); and

[0021] Fig.11 Resource timing of exemplary time-frequency resources for a physical sidelink feedback channel (PSFCH) resource set for a power saving WTRU and a resource set for a non-power saving WTRU are shown. DETAILED DESCRIPTION

[0022] Figure 1A1 is a schematic diagram illustrating 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 through sharing of system resources (including wireless bandwidth). For example, the communication system 100 may employ 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 discrete Fourier transform spread OFDM (ZT-UW-DFT-S-OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, filter bank multi-carrier (FBMC), etc.

[0023] like Figure 1A As shown, the communication system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d (which may be vehicles), a radio access network (RAN) 104, a core network (CN) 106, a public switched telephone network (PSTN) 108, the Internet 110 and other networks 112, but it should be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. 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, the WTRUs 102a, 102b, 102c, 102d (any of which may be referred to as a station (STA)) may be configured to transmit and / or receive wireless signals and may include user equipment (UE), a mobile station, a vehicle (e.g., a car, a self-driving / autonomous car, a bus, a train, a bicycle, an airplane, a scooter, a road roller, etc.), 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 operating in an industrial and / or automated process chain environment), a consumer electronic device, a device operating on a commercial and / or industrial wireless network, etc. Any of the WTRUs 102a, 102b, 102c, and 102d may be interchangeably referred to as a WTRU.

[0024] 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 that is configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the CN 106, the Internet 110, and / or other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a NodeB, an evolved NodeB (eNB), a Home NodeB, a Home evolved NodeB, a next generation NodeB such as a gNodeB (gNB), a new radio (NR) NodeB, a site controller, an access point (AP), a wireless router, and the like. Although the base stations 114a, 114b are each depicted as a single element, it should be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0025] The base station 114a may be part of the RAN 104, which may also include other base stations and / or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), a relay node, etc. 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, which may be referred to as a cell (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 coverage of wireless services to a specific geographic area, which may be relatively fixed or may change over time. The 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 an example, the base station 114a may include three transceivers, such as one transceiver for each sector of the cell. In an embodiment, the base station 114a may employ multiple-input multiple-output (MIMO) technology and may utilize multiple transceivers for each sector of the cell. For example, beamforming may be used to transmit and / or receive signals in a desired spatial direction.

[0026] 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, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0027] More specifically, as noted above, the communication system 100 may be a multiple access system and may employ one or more channel access schemes such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, etc. For example, the base station 114a in the RAN 104 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 116. 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 ​​Uplink (UL) Packet Access (HSUPA).

[0028] 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 LTE-Advanced (LTE-A) and / or LTE-Advanced Pro (LTE-A Pro).

[0029] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as NR radio access, which may establish the air interface 116 using NR.

[0030] 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 implement LTE radio access and NR radio access together, for example using dual connectivity (DC) principles. Thus, the air interface utilized 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).

[0031] 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, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile Communications (GSM), GSM Enhanced Data Rates for Evolution (EDGE), GSM EDGE (GERAN), etc.

[0032] Figure 1A The 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 utilize any suitable RAT to facilitate wireless connectivity in a local area, such as a business location, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a road, and the like. In an example, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In an embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.) to establish a picocell or a femtocell. Figure 1A As shown, the base station 114 b may have a direct connection to the Internet 110. Thus, the base station 114 b may not need to access the Internet 110 via the CN 106.

[0033] The RAN 104 may be in communication with the CN 106, 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. Data may have different quality of service (QoS) requirements, such as different throughput requirements, delay requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 may provide call control, billing services, mobile location-based services, pre-paid calling, Internet connectivity, video distribution, etc., and / or perform high-level security functions, such as user authentication. Although not described in detail in the specification, the CN 106 may be 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. Figure 1AAlthough not shown in the figure, it will be appreciated that the RAN 104 and / or the CN 106 may be in direct or indirect communication with other RANs that employ the same RAT as the RAN 104 or a different RAT. For example, in addition to being connected to the RAN 104, which may utilize NR radio technology, the CN 106 may also be in communication with another RAN (not shown) that employs GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0034] The CN 106 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 networks and devices that use common communication protocols, such as the Transmission Control Protocol (TCP), the User Datagram Protocol (UDP), and / or the Internet Protocol (IP) in the TCP / IP Internet protocol suite. The networks 112 may include wired and / 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, which may employ the same RAT as the RAN 104 or a different RAT.

[0035] 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 via 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.

[0036] Figure 1B is a system diagram illustrating an exemplary WTRU 102. Figure 1B As shown, the WTRU 102 may include, among other things, a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and / or other peripherals 138. It will be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0037] 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), any other type of integrated circuit (IC), a state machine, etc. The processor 118 may perform signal coding, data processing, power control, input / output processing, and / or any other functions that enable 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, but it is understood that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0038] The transmit / receive element 122 may be configured to transmit signals to or receive signals from a base station (e.g., base station 114a) via an air interface 116. For example, in an example, the transmit / receive element 122 may be an antenna configured to transmit and / or receive RF signals. In one embodiment, the transmit / receive element 122 may be a transmitter / detector configured to transmit and / or receive, for example, IR, UV, or visible light signals. In yet another embodiment, the transmit / receive element 122 may be configured to transmit and / or receive RF and light signals. It should be understood that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0039] Although the transmit / receive element 122 is Figure 1B 102 as a single element, but the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may employ MIMO technology. Thus, in an example, the WTRU 102 may include two or more transmit / receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0040] The transceiver 120 may be configured to modulate signals to be transmitted by the transmit / receive element 122 and to demodulate signals received by the transmit / receive element 122. As noted above, the WTRU 102 may have multi-mode capabilities. For example, the transceiver 120 may include multiple transceivers to enable the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11.

[0041] The processor 118 of the WTRU 102 may be coupled to a speaker / microphone 124, a keypad 126, and / or a 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 therefrom. 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 data in any type of suitable memory, such as a non-removable memory 130 and / or a 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 a memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0042] The processor 118 may receive power from the power source 134, and may be configured to distribute and / or control power to 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 (NiCd), nickel-zinc (NiZn), nickel-metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, etc.

[0043] 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) regarding 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) over the air interface 116 and / or determine its location based on the timing of signals received from two or more nearby base stations. It will be appreciated that the WTRU 102 may acquire location information by any suitable location-determination method while remaining consistent with an embodiment.

[0044] The processor 118 may also be coupled to other peripherals 138, which may include one or more software modules and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, the peripherals 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, a Bluetooth® module, FM radio unit, digital music player, media player, video game player module, Internet browser, virtual reality and / or augmented reality (VR / AR) device, activity tracker, etc. The peripheral device 138 may include one or more sensors. The sensor may be one or more of the following: a gyroscope, an accelerometer, a Hall effect sensor, a magnetometer, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor; a geographic location sensor, an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, a gesture sensor, a biometric sensor, a humidity sensor, etc.

[0045] The WTRU 102 may include a full-duplex radio for which transmission and reception of some or all signals (e.g., associated with specific subframes for UL (e.g., for transmission) and DL (e.g., for reception)) may be concurrent and / or simultaneous. The full-duplex radio may include an interference management unit for reducing and / or substantially eliminating self-interference via hardware (e.g., choke) or via signal processing performed by a processor (e.g., a separate processor (not shown) or via the processor 118). In one embodiment, the WTRU 102 may include a half-duplex radio for which transmission and reception of some or all signals (e.g., associated with specific subframes for UL (e.g., for transmission) or DL ​​(e.g., for reception)) may be concurrent and / or simultaneous.

[0046] Figure 1C 1 is a system diagram illustrating the RAN 104 and the CN 106 according to one embodiment. As described above, the RAN 104 may employ an E-UTRA radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0047] The RAN 104 may include evolved Node-Bs 160a, 160b, 160c, though it will be appreciated that the RAN 104 may include any number of evolved Node-Bs while remaining consistent with an embodiment. The evolved Node-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 an example, the evolved Node-Bs 160a, 160b, 160c may implement MIMO technology. Thus, the evolved Node-B 160a, for example, may use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a.

[0048] Each of the evolved Node Bs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, etc. Figure 1C As shown, the eNode-Bs 160a, 160b, 160c may communicate with one another via an X2 interface.

[0049] 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 (PGW) 166. While the foregoing elements are depicted as part of the CN 106, it should be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0050] The MME 162 may be connected to each of the evolved Node-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, bearer activation / deactivation, selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c, etc. 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.

[0051] The SGW 164 may be connected to each of the evolved Node-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 perform other functions, such as anchoring the user plane during inter-evolved Node-B handovers, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, managing and storing the context of the WTRUs 102a, 102b, 102c, and the like.

[0052] The SGW 164 may be connected to the PGW 166, 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.

[0053] 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 may be in communication with, an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that serves 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.

[0054] Although the WTRU Figures 1A to 1D Although described as a wireless terminal, it is contemplated that in certain representative embodiments such a terminal may (eg, temporarily or permanently) employ a wired communications interface with a communications network.

[0055] In a representative embodiment, the other network 112 may be a WLAN.

[0056] A WLAN in 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 have access or an interface to a distribution system (DS) or another type of wired / wireless network that carries traffic to and / or carries traffic away from the BSS. Traffic originating from outside the BSS and directed to the STA may be reached by the AP and may be delivered to the STA. Traffic originating from the STA and directed to a destination outside the BSS may be sent to the AP to be delivered to the corresponding destination. Traffic between STAs within the BSS may be sent by the AP, for example, where the source STA may send traffic to the AP, and the AP may deliver the traffic to the destination STA. Traffic between STAs within the BSS may be considered and / or referred to as point-to-point traffic. Point-to-point traffic may be sent between the source and destination STAs (e.g., directly between them) using direct link establishment (DLS). In certain representative embodiments, the DLS may use 802.11e DLS or 802.11z tunnel DLS (TDLS). A WLAN using an independent BSS (IBSS) mode may not have an AP, and STAs (eg, all STAs) within or using the IBSS may communicate directly with each other. The IBSS communication mode may sometimes be referred to herein as an "ad-hoc" communication mode.

[0057] When using the 802.11ac infrastructure operating mode or a similar operating mode, the AP may transmit a beacon on a fixed channel (such as a primary channel). The primary channel may be a fixed width (e.g., a 20MHz wide bandwidth) or a dynamically set width. The primary channel may be an operating channel of the BSS and may be used by the STA to establish a connection with the AP. In certain representative embodiments, carrier sense multiple access / collision avoidance (CSMA / CA) may be implemented, for example, in an 802.11 system. For CSMA / CA, a STA (e.g., each STA) (including the AP) may sense the primary channel. If the primary channel is sensed / detected and / or determined to be busy by a specific STA, the specific STA may back off. One STA (e.g., only one station) may transmit at any given time in a given BSS.

[0058] High throughput (HT) STAs may communicate using a 40 MHz wide channel, for example, via a combination of a primary 20 MHz channel and adjacent or non-adjacent 20 MHz channels to form a 40 MHz wide channel.

[0059] Very high throughput (VHT) STAs may support 20MHz, 40MHz, 80MHz, and / or 160MHz wide channels. 40MHz and / or 80MHz channels may be formed by combining consecutive 20MHz channels. A 160MHz channel may be formed by combining 8 consecutive 20MHz channels, or by combining two non-contiguous 80MHz channels (this may be referred to as an 80+80 configuration). For the 80+80 configuration, after channel coding, the data may pass through a segment parser that may divide the data into two streams. Each stream may be individually processed by an inverse fast Fourier transform (IFFT) and time domain processing. These streams may be mapped to two 80MHz channels, and data may be transmitted by a transmitting STA. At the receiver of the receiving STA, the operations described above for the 80+80 configuration may be reversed, and the combined data may be sent to a medium access control (MAC).

[0060] 802.11af and 802.11ah support operating modes below 1GHz. Channel operating bandwidths and carriers are reduced in 802.11af and 802.11ah relative to those used in 802.11n and 802.11ac. 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 may support meter type control / machine type communication (MTC), such as MTC devices in macro coverage areas. MTC devices may have certain capabilities, such as limited capabilities, including support for (e.g., only support for) certain bandwidths and / or limited bandwidths. MTC devices may include batteries with battery life above a threshold (e.g., to maintain very long battery life).

[0061] WLAN systems that can support multiple channels and channel bandwidths such as 802.11n, 802.11ac, 802.11af, and 802.11ah include channels that can be designated as primary channels. The primary channel may have a bandwidth equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be set and / or limited by a STA (which supports the minimum bandwidth operating mode) from all STAs operating in the BSS. In the example of 802.11ah, for STAs (e.g., MTC-type devices) that support (e.g., only support) 1MHz mode, the primary channel may be 1MHz wide, even if the AP and other STAs in the BSS support 2MHz, 4MHz, 8MHz, 16MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or network allocation vector (NAV) settings may depend on the state of the primary channel. If the primary channel is busy, for example, because a STA (supporting only the 1MHz operating mode) is transmitting to the AP, all available frequency bands may be considered busy even if most of the available frequency bands remain idle.

[0062] 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. The total bandwidth available for 802.11ah is 6MHz to 26MHz, depending on the country code.

[0063] Figure 1D 1 is a system diagram illustrating the RAN 104 and the CN 106 according to one embodiment. As noted above, the RAN 104 may employ NR radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0064] The RAN 104 may include gNBs 180a, 180b, 180c, though it will be appreciated that the RAN 104 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, 180c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In an example, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, the gNBs 180a, 180b may utilize beamforming to transmit signals to and / or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a may, for example, use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a. In an embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation techniques. For example, the gNB 180a may transmit multiple component carriers to the 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, the gNBs 180a, 180b, 180c may implement coordinated multi-point (CoMP) techniques. For example, the WTRU 102a may receive coordinated transmissions from the gNB 180a and gNB 180b (and / or gNB 180c).

[0065] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with scalable parameter sets. For example, OFDM symbol spacing and / or OFDM subcarrier spacing may vary for different transmissions, different cells, and / or different portions of the wireless transmit spectrum. The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using subframes or Transmission Time Intervals (TTIs) of varying or scalable lengths (e.g., containing varying numbers of OFDM symbols and / or varying absolute time lengths over time).

[0066] 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 while also not accessing other RANs (e.g., such as 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 anchor points. 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 WTRUs 102a, 102b, 102c may communicate or be connected with the gNBs 180a, 180b, 180c while also communicating or being connected with other RANs, such as the eNode-Bs 160a, 160b, 160c. For example, the WTRUs 102a, 102b, 102c may implement the DC principle to communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c substantially simultaneously. In a non-standalone configuration, the eNode-Bs 160a, 160b, 160c may serve as mobility anchors for the WTRUs 102a, 102b, 102c, and the gNBs 180a, 180b, 180c may provide additional coverage and / or throughput for serving the WTRUs 102a, 102b, 102c.

[0067] 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, scheduling of users in UL and / or DL, support of network slicing, interworking between DC, NR, and E-UTRA, routing of user plane data towards a user plane function (UPF) 184a, 184b, routing of control plane information towards an access and mobility management function (AMF) 182a, 182b, etc. As shown in FIG. Figure 1D As shown, gNBs 180a, 180b, and 180c may communicate with each other via an Xn interface.

[0068] Figure 1D The illustrated CN 106 may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one session management function (SMF) 183a, 183b, and a data network (DN) 185a, 185b. Although the foregoing elements are depicted as part of the CN 106, it should be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0069] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c via the N2 interface in the RAN 104 and may serve as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRU 102a, 102b, 102c, support of network slicing (e.g., handling of different protocol data unit (PDU) sessions with different requirements), selecting a specific SMF 183a, 183b, management of registration areas, termination of non-access stratum (NAS) signaling, mobility management, etc. The AMF 182a, 182b may use network slicing in order to customize CN support for the WTRU 102a, 102b, 102c based on the type of services used by the WTRU 102a, 102b, 102c. For 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 mobile broadband (eMBB) access, services for MTC access, etc. The AMF 182a, 182b may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies, such as WiFi.

[0070] The SMF 183a, 183b may be connected to the AMF 182a, 182b in the CN 106 via the N11 interface. The SMF 183a, 183b may also be connected to the UPF 184a, 184b in the CN 106 via the N4 interface. The SMF 183a, 183b may select and control the UPF 184a, 184b, and configure traffic routing through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions such as managing and allocating WTRU IP addresses, managing PDU sessions, controlling policy enforcement and QoS, providing DL data notifications, etc. The PDU session type may be IP-based, non-IP-based, Ethernet-based, etc.

[0071] The UPF 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 104 via the N3 interface, 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. The UPF 184, 184b may perform other functions, such as routing and forwarding packets, enforcing user plane policies, supporting multi-homed PDU sessions, handling user plane QoS, buffering DL packets, providing mobility anchoring, etc.

[0072] The CN 106 may facilitate communications with other networks. For example, the CN 106 may include or may communicate with an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that serves 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. In an example, the WTRUs 102a, 102b, 102c may be connected to the DNs 185a, 185b through the UPFs 184a, 184b via an N3 interface to the UPFs 184a, 184b and an N6 interface between the UPFs 184a, 184b and the local DNs 185a, 185b.

[0073] Given that Figures 1A to 1D as well as Figures 1A to 1D Corresponding to the description of the present invention, one or more or all of the functions described herein with reference to one or more of the following may be performed by one or more simulation devices (not shown): WTRU102a-d, base station 114a-b, evolved Node B 160a-c, MME 162, SGW 164, PGW 166, gNB 180a-c, AMF182a-b, UPF 184a-b, SMF 183a-b, DN 185a-b and / or any other device described herein. The simulation device may be one or more devices configured to emulate one or more or all of the functions described herein. For example, the simulation device may be used to test other devices and / or simulate network and / or WTRU functions.

[0074] The simulation device may be designed to implement one or more tests of other devices in a laboratory environment and / or in an operator network environment. For example, the one or more simulation devices may perform one or more or all functions while being fully or partially implemented and / or deployed as part of a wired and / or wireless communication network in order to test other devices within the communication network. The one or more simulation devices may perform one or more functions or all functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network. The simulation device may be directly coupled to another device for testing purposes and / or perform testing using over-the-air wireless communications.

[0075] The one or more simulation devices may perform one or more (including all) functions without being implemented / deployed as part of a wired and / or wireless communication network. For example, the simulation device may be used in a test scenario in a test lab and / or a non-deployed (e.g., testing) wired and / or wireless communication network to enable testing of one or more components. The one or more simulation devices may be test equipment. Direct RF coupling and / or wireless communication via RF circuitry (e.g., which may include one or more antennas) may be used by the simulation device to transmit and / or receive data.

[0076] The New Radio (NR) system currently being developed by 3GPP is expected to support multiple use cases such as enhanced mobile broadband (eMBB) and ultra-high reliability and low latency communications (URLLC). Support for enhanced V2X (eV2X) communications in the NR system is under development. eV2X in NR may support new services for both safety and non-safety scenarios, including but not limited to sensor sharing, autonomous driving, vehicle platooning, and remote driving. Different eV2X services may require different performance requirements and / or time delays (e.g., 3ms delay).

[0077] NR V2X can support new use cases, including but not limited to vehicle platooning, advanced driving, extended sensors, and remote driving. Vehicle platooning can enable vehicles to dynamically form groups that travel together. Two or more vehicles (e.g., all vehicles) in a given platoon can receive periodic data from the lead vehicle for platooning operations. This data can allow the distance between vehicles (gap distance) to become extremely small, so that the gap distance converted to time can be very low (e.g., sub-second). Platoon applications can allow vehicles in a platoon to drive autonomously. Advanced driving can achieve semi-autonomous or fully autonomous driving. Longer inter-vehicle distances can be assumed. Each vehicle and / or roadside unit (RSU) can share data obtained from its local sensors with approaching vehicles, allowing vehicles to coordinate their trajectories or activities. In addition, each vehicle can share its driving intentions with approaching vehicles. Such use groups can provide safer travel, conflict avoidance, and improved traffic efficiency.

[0078] Extended sensors enable the exchange of raw or processed data collected by local sensors or real-time video data between, for example, vehicles, WTRUs, RSUs, pedestrian devices, and / or V2X application servers. Vehicles can enhance their perception of their environment beyond what their own sensors can detect and have a more comprehensive understanding of the local environment based on sensor data collected for various devices. Remote driving enables a remote driver or V2X application to operate a remote vehicle (e.g., for a passenger who cannot drive themselves) or a remote vehicle located in a hazardous environment. Cloud-based driving can be used in situations where changes are limited and routes are predictable, such as public transportation. In an example, access to a cloud-based backend service platform can be used to remove driving.

[0079] In the examples described herein, vehicles, WTRUs, RSUs, UEs, and pedestrian devices may be used interchangeably. For example, a WTRU as used herein may refer to a portable wireless device mounted on or integrated into a vehicle (a vehicle having wireless communication capabilities), or a portable wireless device carried by a pedestrian. A WTRU may refer to a pedestrian user equipment (PUE) and may be referred to as a power-saving WTRU. A WTRU may refer to a vehicle user equipment (VUE) and may be referred to as a vehicle WTRU. In some examples, a vehicle WTRU (VUE) may be a non-power-saving device that is less restricted in terms of available power than a power-saving WTRU, such as a mobile device carried by a pedestrian (e.g., a PUE).

[0080] The QoS model for NR V2X may be described. QoS on the LTE-V2X air interface (such as the PC5 interface) may be supported by ProSe per-packet priority (PPPP). The application layer may be allowed to mark packets with PPPP, which indicates the required QoS level. Certain enhancements may be added, such as allowing the packet delay budget (PDB) to be derived from PPPP.

[0081] Examples of key performance indicators (KPIs) for NR V2X may include payload (e.g., bytes), transmission rate (e.g., messages / second), maximum end-to-end latency (e.g., ms), reliability (%), data rate (e.g., Mbps), and / or minimum required communication range (e.g., meters).

[0082] The same set of service requirements (or different service requirements) may apply to PC5-based V2X communications and Uu-based V2X communications. Such QoS characteristics may be represented by a 5G QoS identifier (5QI). In an example, a unified QoS model may be used for PC5 and Uu interfaces, such that a 5QI may be used for V2X communications over PC5, and such that the application layer may have a consistent way to indicate QoS requirements regardless of the link used.

[0083] In an example, a WTRU (including a vehicle) supporting 5G / NR V2X may utilize any one or more of the following types of services: broadcast, multicast, and / or unicast. For unicast type services, the same QoS model as Uu may be used, such that each unicast link may be considered a bearer and may be associated with a QoS flow respectively. Additional parameters of QoS characteristics and / or data rates defined in the 5QI may be applied. In an example, the minimum required communication range may be considered an additional parameter used by PC5. Similar considerations may apply to multicast services, as it may be considered a special case of unicast (e.g., with multiple defined service receivers). For broadcast services, there may be no concept of bearers. In this case, each message may have different characteristics depending on the given application requirements. The 5QI can be used in a similar manner to PPPP and / or ProSe per-packet reliability (PPPR) (e.g., to mark each packet). The 5QI may be able to represent the characteristics required for PC5 broadcast operation (e.g., delay, priority, and / or reliability). A set of V2X broadcast-specific 5QIs (e.g., referred to as VQIs) may be defined for use by PC5.

[0084] In an example, PC5 QoS parameters may be negotiated when establishing a one-to-one communication procedure, which may be enhanced to support PC5 QoS parameter negotiation between two WTRUs. After the PC5 QoS parameter negotiation procedure, the same QoS may be used in both directions. Figure 2 2 is a signaling diagram illustrating an exemplary link establishment process 200 that may be used to establish a secure communication link, such as a layer 2 (L2) link, over a PC5 interface. Figure 2 As shown, WTRU 201 and WTRU 202 may communicate one-to-one over a direct air interface, such as a PC5 interface, and may negotiate PC5 QoS parameters during a link establishment procedure 200. For example, WTRU 201 may send a direct communication request message 204 to WTRU 202 to trigger a mutual authentication procedure 206 between WTRUs 201 and 202. The direct communication request message 204 may include (e.g., requested) PC5 QoS parameters. WTRU 202 may initiate the mutual authentication procedure 206. For example, WTRU 202 may send a response message (not shown) to WTRU 201 as part of the mutual authentication procedure 206, and may include the accepted PC5 QoS parameters in the response message sent back to WTRU 201.

[0085] According to the NR V2X service model, NR V2X may support, but is not limited to supporting any one or more of the following types of services: periodic and aperiodic. NR V2X may support additional different types of packet sizes, packet arrival rates, and / or delay requirements. For example, mode 2 aperiodic services may support packet sizes between approximately 10,000 bytes and 30,000 bytes, an average arrival rate of approximately 20 ms, and / or a delay requirement of approximately 10 ms. In another example, mode 3 periodic services may support packet sizes between approximately 30,000 bytes and 60,000 bytes, an average arrival rate of approximately 30 ms, and / or a delay requirement of approximately 30 ms.

[0086] Partial sensing and / or random selection may be used as a power saving mechanism in LTE V2X (e.g., for use by pedestrian WTRUs). In the case of partial sensing, the WTRU may be configured by upper layers with a minimum number of candidate subframes in the resource selection window [T1, T2], where the specific subframes may be selected by the WTRU implementation. The WTRU may perform sensing in the sensing window only on subframes that are an integer number of reservation periods away from the candidate subframes, thereby reducing the amount of resources that the WTRU needs to perform sensing in the sensing window. Another implementation for pedestrian WTRUs may be to perform random selection on a resource pool. If the resource pool is configured for random selection, the WTRU may perform resource selection without considering any sensing results during the sensing process.

[0087] Discontinuous Reception (DRX) may be used over the NR Uu interface. Connected mode DRX may be specified for power saving in the NR Uu for a WTRU in RRC_CONNECTED. DRX may be scheduled based on a configuration of a wake-up time at the WTRU. If the WTRU receives a physical downlink control channel (PDCCH) schedule during its wake-up time, it may remain awake for a period of time until no further schedule is received. The WTRU may be configured with parameters including, but not limited to, any of the following exemplary parameters: drx-onDurationTimer: duration at the start of a DRX cycle; drx-SlotOffset: delay before starting the drx-onDurationTimer; drx-InactivityTimer: duration after a PDCCH opportunity in which the PDCCH indicates a new uplink (UL) or downlink (DL) transmission for a medium access control (MAC) entity; drx-RetransmissionTimerDL (per DL hybrid automatic repeat request (HARQ) process, which may or may not include a broadcast process): maximum duration until a DL retransmission is received; drx-RetransmissionTimerUL (per UL HARQ process): maximum duration until a grant for UL retransmission is received; drx-LongCycleStartOffset: long DRX cycle; drx-StartOffset: subframe at which long DRX cycle and short DRX cycle start; drx-ShortCycle: short DRX cycle; drx-ShortCycleTimer: duration for which the WTRU should follow the short DRX cycle; drx-HARQ-RTT-TimerDL (per DL HARQ process, which may or may not include a broadcast process): minimum duration before the MAC entity expects a DL assignment for HARQ retransmission; and / or drx-HARQ-RTT-TimerUL (per UL HARQ process): minimum duration before the MAC entity expects a UL HARQ retransmission grant.

[0088] A WTRU configured with DRX may determine its active time (e.g., the time during which the WTRU actively monitors the PDCCH), such that when a DRX cycle is configured, the active time may include: the duration of the operation of a timer (e.g., drx-onDurationTimer, drx-InactivityTimer, drx-RetransmissionTimerDL, drx-RetransmissionTimerUL, and / or ra-ContentionResolutionTimer); the time or duration during which a scheduling request is sent and waited on the PUCCH; and / or the time or duration during which a newly transmitted PDCCH signal or message indicating a C-RNTI addressed to the MAC entity has not been received after successfully receiving a random access response message for which a preamble was not selected by the MAC entity.

[0089] Long-term partial listening and short-term listening may be implemented according to the subject matter disclosed herein. NR V2X may support both periodic and non-periodic services. When semi-persistent resource reservation is enabled, long-term partial listening may be used (e.g., in LTE V2X) to avoid conflicts with periodic services. However, long-term partial listening may not detect reservations for dynamic resource allocations. In addition, semi-persistent resource reservation may be enabled / disabled in a resource pool. Therefore, in a resource pool where semi-persistence is disabled, long-term partial listening may not be used.

[0090] To reduce resource conflicts for dynamic resource allocation, the WTRU may need to perform short-term listening, which may be performed immediately before the WTRU's transmission. In addition, to save power, partial listening may be used in the short-term listening window. Power saving listening and resource selection may take into account the interaction between long-term partial listening and short-term partial listening.

[0091] In LTE V2X, it is expected that a power saving WTRU (also referred to as power saving user equipment (PUE)) uses the same resource pool as a non-power saving device, such as a non-power saving device, such as a vehicle WTRU (also referred to as vehicle user equipment (VUE)). The power saving WTRU may be configured in a large resource pool to perform listening. Performing listening in all subchannels configured in the resource pool may result in listening overhead and power inefficiency. Therefore, in an example, the power saving WTRU may selectively select a set of subchannels from the resource pool to monitor and perform listening to save power. In this case, listening adaptation in the frequency domain may be used.

[0092] Techniques for sidelink power saving including power sensing are disclosed herein. In an example, a WTRU may perform long-term partial sensing in one or more sensing subwindows. For example, a WTRU may monitor semi-persistent reservations of other WTRUs. In a long-term sensing window, a WTRU may partially perform sensing in K time slots in each subwindow sensing of X time slots, where K≤X. A WTRU may perform resource selection in K time slots in a resource selection subwindow of X time slots. The resource selection subwindows, the time gap between each sensing subwindow, and / or the number of times a subwindow sensing occurs may be configured or preconfigured.

[0093] Figure 3 A timing diagram of exemplary listening windows and sub-windows that may be used by a WTRU 301 in a long term partial listening procedure 300 is shown. During the long term partial listening window 302, the WTRU 301 may perform partial listening on K time slots in each sub-window 304 of X time slots, e.g., to monitor and determine semi-persistent reservations of other WTRUs, before selecting a resource during a resource selection window 306. The resource selection window 306 starts at time T1 and ends at time T2. The time gap between the first sub-window 304 in the long term partial listening window 302 and the resource selection sub-window 308 is j*P, where the values ​​of j and P may be (pre)configured. Other sub-windows 304 may have a time gap to the resource selection sub-window 308 that is a multiple of P (e.g., P, 2P). The WTRU 301 may trigger resource allocation at time n and before the start of the resource selection window 306 at time T1, and may select resources from a set of K selectable time slots 320 for communication during the resource selection sub-window 308. The WTRU 301 may determine the value of X and / or K based on one or more of the following information: the bandwidth of the resource pool; the number of subchannels that the WTRU 301 performs listening in each time slot; the QoS or sidelink radio bearer (SLRB) / logical channel (LCH) associated with a pending transport block (TB) or an expected TB; the broadcast type (e.g., unicast, multicast, or broadcast) of the pending TB; the channel busy rate (CBR) of the resource pool; the HARQ type of the TB; and / or the power saving mode or state of the WTRU 301. Detailed examples for selecting the parameters X and K are described below.

[0094] For example, the values ​​of X and / or K may be determined based on the bandwidth of the resource pool and / or the number of subchannels on which the WTRU performs listening in each time slot. For example, the WTRU may determine the value of K based on the number of subchannels used for listening. If the number of subchannels used for listening is large, the WTRU may select a smaller K value, and if the number of subchannels used for listening is small, a larger K value may be selected. This approach may be motivated to ensure that the WTRU is able to select sufficient available resources for resource selection. As another example, the values ​​of X and / or K may be determined based on the QoS or SLRB / LCH associated with the pending TB or the expected TB. For example, the WTRU may determine a larger K and / or X value when the priority of the pending TB is high, and a smaller K and / or W value when the priority of the pending TB is low.

[0095] As another example, the values ​​of X and / or K may be determined based on the broadcast type (e.g., unicast, multicast, or broadcast) of the TB to be processed. In one example, the WTRU may be configured with different values ​​of K and / or X based on the broadcast type. The WTRU may then determine the value of K based on the broadcast type of the TB. In another example, the WTRU may determine whether to perform listening or whether to use the listening result for resource selection or reselection based on the broadcast type of the TB. For example, the WTRU may perform listening on broadcast services instead of listening on unicast / multicast services. As another example, the values ​​of X and / or K may be determined based on the CBR of the resource pool. For example, when the CBR is higher, the WTRU may increase the values ​​of K and / or X, and when the CBR is lower, the WTRU may reduce the values ​​of K and / or X.

[0096] As another example, the values ​​of X and / or K may be determined based on the HARQ type of the TB. For example, the WTRU may be (pre)configured with at least two sets of minimum values ​​of K and X, one set for disabling HARQ transmission and the other set for enabling HARQ transmission. The WTRU may then determine the values ​​of K and X based on the HARQ type of the TB. In another example, the values ​​of X and / or K may be determined based on one or more power saving modes / states of the WTRU. For example, the WTRU may be (pre)configured with a set of power saving modes / states, and each power saving mode / state may be associated with a partial listening configuration. The partial listening configuration may include a minimum amount of resources for performing listening before performing a transmission (e.g., a minimum number of time slots, subchannels for listening). Therefore, the WTRU may determine the amount of listening resources based on the current power saving state.

[0097] In an example, the WTRU may perform short-term partial listening. The WTRU performing short-term partial listening may enable the WTRU to detect dynamic reservation of TBs. For example, the WTRU may perform short-term partial listening after a packet arrives or after the WTRU triggers resource selection or before the WTRU triggers resource selection. Figure 44 shows a timing diagram of exemplary listening windows and sub-windows that may be used by the WTRU 401 in the short-term partial listening procedure 400. In addition to the long-term partial listening window 402 and the listening sub-window 404, as shown in FIG. Figure 4 As shown in the example of , the WTRU 401 may be able to perform short-term partial listening during the short-term partial listening window 410 using the set (subset) of listening time slots 412. The short-term partial listening window 410 may start after the WTRU 401 triggers resource allocation at time n. The short-term partial listening window 410 may end before the start of the resource selection sub-window 408 (which may include a set of K selectable time slots 420) and may end after the start time T1 of the resource selection window 406 as shown (or, not shown, before the start time T1).

[0098] Figure 5 A timing diagram showing another example of a listening window and sub-window that may be used by the WTRU 501 in the short-term partial listening procedure 500. Although not shown, Figure 5 The long-term partial listening window and the listening sub-window may be included. Figure 5 As shown in the example, the WTRU 501 may be able to perform short-term partial listening using the set (subset) of listening time slots 512 during the short-term partial listening window 510. The short-term partial listening window 510 may occur before the WTRU 501 triggers resource allocation at time n. The short-term partial listening window 510 may end before the start of the resource selection window 506 and before the start of the resource selection sub-window 508 (which may include a set of K optional time slots 520). In the example, the WTRU 501 may perform short-term partial listening after it triggers resource selection for non-periodic traffic and before it triggers resource selection for periodic traffic. Figure 4 and Figure 5 In the exemplary case shown, the short-term partial listening window may be determined based on one or more of the following criteria: the time gap between the packet arrival time and the first selectable time slot in the resource selection subwindow; the QoS or SLRB / LCH of the pending TB or expected TB; and / or whether the WTRU performs long-term partial listening.

[0099] In an example, the short-term partial listening window may be determined based on a time gap between a packet arrival time and a first selectable time slot in a resource selection subwindow. For example, if the time gap is less than a threshold value W, the short-term partial listening window is less than W. If the time gap is greater than the threshold value, the short-term partial listening window may be equal to W. The value of W may be fixed or (pre-)configured by the network.

[0100] In an example, the short-term partial listening window may be determined based on the QoS or SLRB / LCH of the pending TB or the expected TB. In an example, the WTRU may be configured with multiple minimum short-term partial listening windows, each of which may be associated with one or more priorities of the TB. The WTRU may determine the short-term partial listening window size based on the QoS of the pending TB. For example, the WTRU may use a smaller short-term partial listening window for low priority TBs and a larger short-term partial listening window for high priority TBs.

[0101] In an example, if the WTRU performs long-term partial listening, the WTRU may perform short-term partial listening in a set of time slots between the resource selection trigger and the first candidate resource selection time slot. In another example, if the WTRU does not perform long-term partial listening, the WTRU may perform short-term partial listening according to a (pre-)configured listening window. The (pre-)configured short-term partial listening window may be associated with the QoS of the TB or may be fixed to X time slots (e.g., 32 time slots).

[0102] In an example, the WTRU may determine a set of time slots in the short-term partial listening window to perform listening. The set of time slots may be determined based on one or more of the following criteria: configuration / pre-configuration; QoS or SLRB / LCH associated with the TB; CBR of the resource pool; whether resource (re)evaluation of the TB is enabled or disabled; HARQ type of the TB (e.g., HARQ-enabled and HARQ-disabled TBs); broadcast type of the TB (e.g., broadcast, unicast, or multicast); the number of candidate time slots and / or the number of candidate resources in a period; DRX state of the WTRU; whether the WTRU performs resource selection for initial selection, (re)evaluation of selected resources, or (re)evaluation of reserved resources; and / or whether semi-persistence is enabled / disabled in the resource pool.

[0103] In an example, the group of time slots may be determined based on configuration / pre-configuration. For example, the WTRU may configure / pre-configure a group of time gaps between each optional time slot and the time slots to be listened to in the resource selection subwindow. In an example, the group of time slots may be determined based on the QoS or SLRB / LCH associated with the TB. For example, the WTRU may configure / pre-configure the minimum number of listening time slots in the short-term partial listening window. The WTRU may then select the group of time slots to perform listening to satisfy that the number of time slots listened to is greater than a configured / pre-configured threshold. The WTRU may select the group of time slots at the beginning / end of the short-term listening window, or may select the group of time slots randomly.

[0104] In an example, the set of time slots may be determined based on the CBR of the resource pool. In one example, if the CBR of the resource pool is greater than a threshold, the WTRU may perform a short-term partial listening, and if the CBR of the resource pool is less than the threshold, the short-term partial listening may not be performed. In another example, the WTRU may determine the short-term partial listening window based on the CBR of the resource pool. For example, the WTRU may configure / pre-configure the short-term listening window for each CBR range. The WTRU may then determine the actual short-term partial listening window based on the measured CBR of the resource pool.

[0105] In an example, the group of time slots may be determined based on whether the resource (re)evaluation TB is enabled / disabled. For example, the WTRU may determine the short-term listening window size based on whether the resource (re)evaluation TB is enabled / disabled. For example, when the resource (re)evaluation is enabled, the WTRU may be (pre)configured with one short-term listening window, and when the resource (re)evaluation is disabled, the WTRU may be (pre)configured with another short-term listening window. The short-term listening window may be further determined based on the QoS of the TB and / or the CBR of the resource pool. Then, the WTRU may determine the short-term listening window based on whether the resource (re)evaluation is enabled / disabled.

[0106] In an example, the group of time slots may be determined based on the HARQ type of the TB (e.g., HARQ-enabled and HARQ-disabled TBs). In an example, the group of time slots may be determined based on the broadcast type of the TB (e.g., broadcast, unicast, or multicast). In an example, the group of time slots may be determined based on the number of candidate time slots and / or the number of candidate resources within a period. For example, the WTRU may determine the short-term listening window based on the number of candidate time slots in a period (e.g., the period from the packet arrival time to the PDB). For example, if the number of candidate resources is less than the minimum number of required candidate time slots, the WTRU may not perform short-term listening. If the number of candidate time slots is greater than the minimum required candidate resources, the WTRU may initiate a short-term listening upon packet arrival until the number of candidate resources is equal to the minimum required one and / or the short-term listening window is greater than or equal to the minimum required short-term listening window.

[0107] In an example, the group of time slots may be determined based on the DRX state of the WTRU. For example, the DRX state of the WTRU may include any one or more of the following: whether DRX is configured; and / or whether the WTRU is in an on duration or an off duration. In an example, the group of time slots may be determined based on the power saving mode of the WTRU. In an example, the group of time slots may be determined based on whether the WTRU performs resource selection for initial selection, (re)evaluation of selected resources, or (re)evaluation of reserved resources. For example, the WTRU may be (pre)configured with three minimum short-term listening windows for initial resource selection, (re)evaluation of selected resources, and / or (re)evaluation of reserved resources. The WTRU may determine the short-term listening for initial selection, (re)evaluation of selected resources, and / or (re)evaluation of reserved resources accordingly. In an example, the group of time slots may be determined based on whether semi-persistence is enabled / disabled in the resource pool.

[0108] In an example, the WTRU may determine to trigger listening (e.g., long-term partial listening and / or short-term partial listening) based on one or more of the following criteria: when / whether a packet arrives at the access stratum (AS) layer; the value of a counter associated with resource selection / reselection reaches a threshold; the arrival of p periodic services; and / or the WTRU determines to perform resource reassessment on semi-persistently reserved resources.

[0109] In an example, when a packet arrives at the AS layer and the WTRU needs to perform resource selection / reselection on the packet, the WTRU may trigger a short-term partial listening. In another method, the WTRU may trigger a short-term partial listening only W time slots before a resource selection window or a resource selection sub-window. The value of W may be determined based on one or more pre-configurations of the network (e.g., the WTRU may configure / pre-configure a minimum duration of a short-term partial listening before a resource reselection window), the QoS of the pending or expected TB, and / or the CBR of the resource pool.

[0110] In an example, the WTRU may trigger a listen when a resource selection / reselection counter is less than a threshold. For example, the WTRU may maintain a resource selection / reselection counter for one or more sidelink processes. If the counter reaches zero, the WTRU may perform resource selection / reselection for the sidelink process. The WTRU may then determine to perform a long-term partial listen when the counter is less than a threshold. This approach may be triggered to ensure that the WTRU has sufficient listening results when it is necessary to perform resource selection / reselection.

[0111] In an example, the WTRU may trigger a long term partial listening in response to the arrival of periodic traffic. The WTRU may use random resource selection and / or resource selection based on short term listening for the first N periods of periodic traffic. The value of N may be based on the periodicity of the periodic traffic and / or the (pre-)configured long term listening period. The WTRU may then use long term partial listening and / or short term partial listening to perform resource selection for the next period when the long term partial listening results are available.

[0112] In an example, the WTRU may trigger a long partial listening for resource re-evaluation of a semi-persistently reserved resource. For example, the WTRU may perform a long partial listening to determine the availability of the semi-persistently reserved resource. Prior to a resource re-evaluation event, the WTRU may determine to perform a long partial listening to collect listening results for the resource re-evaluation event. In an example, the WTRU may perform a long partial listening or a short partial listening based on configuration / pre-configuration (e.g., the WTRU may perform a short partial listening only when semi-persistent reservation is disabled in a resource pool), the QoS of a pending TB or an expected TB, the type of service (e.g., unicast / multicast / broadcast, or periodic / non-periodic service), the HARQ retransmission type of the TB, and / or whether the WTRU performs one or more of a semi-persistent reservation for the TB, or perform both listening processes. In an example, the WTRU may perform long partial listening or short partial listening based on the HARQ retransmission type of the TB, or perform both listening processes (e.g., retransmission based on HARQ feedback, blind retransmission, or a mixture of retransmission based on HARQ feedback and blind retransmission). For example, the WTRU may perform short partial listening only for resource selection of TBs with retransmission based on HARQ feedback, and it may perform short partial listening and long partial listening for resource selection of TBs with blind retransmission.

[0113] In an example, the WTRU may perform short-term partial listening only for resource allocations without semi-persistent reservation (e.g., resource allocations for non-periodic traffic, or resource allocations for periodic traffic in a resource pool where semi-persistent reservation is disabled). In an example, the WTRU may perform short-term partial listening only when the priority of the TB is above a threshold. This implementation may allow the WTRU to reduce conflicts with high priority TBs. In another example, the WTRU may perform short-term partial listening only when the priority of the TB is less than a threshold; otherwise, it may perform both short-term and long-term partial listening.

[0114] In an example, the WTRU may perform long term partial listening only when the WTRU performs resource selection with semi-persistent reservation. In another example, the WTRU may perform long term partial listening only when the priority of a pending TB or an expected TB is less than / greater than a threshold.

[0115] In an example, when the WTRU performs resource selection with semi-persistent reservation, the WTRU may perform both long-term partial listening and short-term partial listening. In another example, when the priority of the TB is greater than a threshold, the WTRU may perform both long-term partial listening and short-term partial listening. This embodiment may reduce the collision probability of high priority TBs. In another example, when the size of the TB is greater than a threshold or the number of subchannels used to transmit the TB is less than a threshold, the WTRU may perform both long-term and short-term partial listening.

[0116] In an example, the WTRU may determine the set of time slots and / or subchannels for performing listening and / or resource allocation based on one or more of configuration / pre-configuration, QoS or SLRB / LCH associated with a pending TB or an expected TB, the size of the pending TB or the expected TB, the size of the listening window and / or the number of time slots listened to in the listening window, the CBR of the resource pool, the channel occupancy (CR) of the WTRU, the location of the WTRU, random selection, listening results, resource evaluation results, the set of reserved resources, the transmission activity of the WTRU, and / or the listening type (e.g., short-term listening or long-term listening).

[0117] The WTRU may determine the set of subchannels and / or time slots for listening based on configuration / pre-configuration. For example, the WTRU may configure / pre-configure a minimum number of subchannels and / or time slots to perform listening and / or resource allocation. The WTRU may select a number of subchannels and / or time slots for listening and / or resource selection that is greater than or equal to the minimum configured value.

[0118] The WTRU may be configured with different minimum listening bandwidths and / or different numbers of listening slots based on the priority or SLRB / LCH associated with the pending TB or the expected TB. The WTRU may then determine the number of listening bandwidths and / or listening slots based on the priority of the pending TB or the expected TB.

[0119] The WTRU may determine the listening bandwidth based on the size of the pending or expected TB. For example, if the size of the pending or expected TB is greater than a threshold, the WTRU may perform listening in one listening bandwidth, and if the size of the pending or expected TB is greater than a threshold, it may determine to perform listening in another listening bandwidth. The threshold may be determined by the WTRU, or it may be configured / pre-configured by the network per resource pool.

[0120] For example, the WTRU may be configured / preconfigured with a minimum number of resources to listen in the listening window. The WTRU may determine the number of time slots and the number of sub-channels in each sensed time slot to perform the listening to ensure that the total amount of resources to be listened is greater than the configured / preconfigured value. The WTRU may then determine the number of sub-channels to perform the listening based on the number of time slots sensed in the listening window.

[0121] The WTRU may determine the set of subchannels and / or time slots for sounding based on the CBR of the resource pool and / or the CR of the WTRU. For example, as shown in Tables 1 and 2, the WTRU may configure / pre-configure a minimum sounding bandwidth and / or a minimum number of time slots to perform sounding based on the CBR of the resource pool and / or the CR of the WTRU. The WTRU may then determine the minimum number of sounding bandwidth and / or time slots to perform sounding based on the measured CBR of the resource pool and / or the CR of the WTRU.

[0122]

[0123] Table 1: Relationship between minimum listening bandwidth configuration and CBR

[0124]

[0125] Table 2: Relationship between minimum listening bandwidth configuration and CR

[0126] The WTRU may determine the set of subchannels and / or time slots for listening based on the location of the WTRU. For example, the WTRU may be configured with a mapping between the location of the WTRU (e.g., region) and the set of listening subchannels. The WTRU may then determine the set of listening subchannels based on the location of the WTRU. In another example, the WTRU may randomly select a set of subchannels to perform listening and resource allocation. This implementation may allow the transmit resources of all WTRUs to be evenly distributed in a large resource pool.

[0127] The WTRU may determine the set of subchannels and / or time slots for listening based on its listening results. In one example, if the amount of reserved resources in the set of monitoring / listening time slots is greater than a threshold, the WTRU may exclude any time slots in the group. In another example, if the amount of reserved resources in a set of subchannels is higher than a threshold, the WTRU may exclude the set of subchannels from all listening time slots or a set of monitoring subchannels in a subset of listening time slots. The WTRU may stop monitoring a set of subchannels by not decoding the sidelink control information (SCI) in these subchannels and / or not using the listening results obtained from these subchannels for the resource reassessment process. These specific implementations may help the WTRU save power because the WTRU may not need to monitor / listen in time slots that have been reserved by other WTRUs. The WTRU may determine the duration of excluding occupied timeslots from the set of listening timeslots based on one or more of configured / pre-configured settings, random selection, QoS associated with a pending or expected TB or SLRB / LCH and / or QoS of a TB associated with the occupied timeslot, and / or a channel busy rate (CBR) of the resource pool.

[0128] In an example, the WTRU may determine the duration of excluding occupied time slots from the group of listening time slots based on a configured / preconfigured setting. For example, the WTRU may be configured for a fixed duration / period to exclude occupied time slots from the group of monitoring / listening time slots. In an example, the WTRU may determine the duration of excluding occupied time slots from the group of listening time slots based on a random selection. For example, the WTRU may randomly select a time slot (e.g., the number of time slots) to exclude occupied time slots from the group of monitoring time slots. The time slot can be randomly selected within a range that can be configured / preconfigured by the network. In an example, the WTRU may determine the duration of excluding occupied time slots from the group of listening time slots based on the QoS associated with the pending or expected TB or the SLRB / LCH and / or the QoS of the TB associated with the occupied time slot. For example, for a high priority TB, the WTRU may exclude the time slot from monitoring / listening for a long duration, and for a low priority TB, the WTRU may exclude the time slot for a short duration. In an example, the WTRU may determine the duration of excluding occupied timeslots from the set of listening timeslots based on the CBR of the resource pool. For example, if the CBR is low, the WTRU may stop monitoring occupied timeslots for a long time, and if the CBR of the resource pool is high, the WTRU may stop monitoring occupied timeslots for a short time.

[0129] The WTRU may adjust a set of listening resources based on the resource evaluation results. For example, the WTRU may adjust the set of time slots and / or the set of subchannels to perform listening based on the results of one or more of the resource evaluation processes described herein. For example, if one or more of the following exemplary conditions are met, the WTRU may increase the amount of listening resources by increasing the number of listening time slots or the number of listening subchannels: the amount of optional resources is less than a certain threshold after the resource evaluation process; and / or the number of RSRP threshold increases exceeds the (pre) configured time. In another example, the WTRU may reduce the amount of listening resources if one or more of the following exemplary conditions are met: after the resource evaluation process, the WTRU reports an amount of resources greater than a certain amount; and / or the number of RSRP threshold increases is less than the (pre) configured time.

[0130] The WTRU may determine the set of time slots and / or subchannels to perform listening based on the set of reserved resources. For example, the WTRU may be configured / preconfigured to perform resource evaluation / re-evaluation on the reserved resources and / or the time gap between the reserved resources and the listening time slots to determine potential conflicts between the WTRU's reserved resources and the reserved resources of other WTRUs.

[0131] Figure 6 A timing diagram is shown of an example process 600 for a WTRU 601 to determine a set of resources on which to perform listening based on a set of reserved resources. Figure 6In the example of FIG. 6 , the WTRU 601 may reserve resources 610 in time slots 624 for transmission in each reservation period 602. The WTRU 601 may use resources 606 including subchannels 610 in the listening time slots 622 to listen / monitor for reservations of other WTRUs 603. The WTRU 601 may perform monitoring / listening in subchannels 606 of the listening resources 622, where other WTRUs 603 may reserve resources for transmission in time slots 624 that conflict with the subchannels 610. The set of time slots 622 for performing listening may have a time gap of J*P time slots before the reserved time slots 624 reserved for transmission by the WTRU 601.

[0132] According to another example, the WTRU may skip monitoring one or more listening sub-windows to save power. The WTRU may determine whether to skip monitoring one or more listening sub-windows based on the QoS of the TB and / or the CBR of the resource pool. For example, the WTRU may be configured / pre-configured for multiple listening sub-windows to monitor. If the priority of the TB is less than a threshold and / or the CBR of the resource pool is less than a threshold, the WTRU may skip monitoring one or more listening sub-windows. If the priority of the TB is greater than a threshold and / or the CBR of the resource is greater than a threshold, the WTRU may not skip any configured monitoring sub-windows.

[0133] In an example, the dynamic adjustment of resources used for listening may be a function of transmission activity. The WTRU may dynamically adjust the resources on which listening is performed based on scheduling activity and / or resource usage (e.g., channel occupancy of the WTRU). The WTRU may perform listening on a first set of resources or a first resource pool when a DRX timer T is running, may start or restart a DRX timer when the WTRU determines that there is transmission activity (e.g., based on listening to resources associated with a resource pool currently being used by the WTRU), and may perform listening on a second set of resources or a resource pool when the DRX timer expires. If the WTRU determines that the transmission is for a session configured by the WTRU (e.g., an L2 identity (ID) of interest), the WTRU may start or restart the DRX timer. If one resource pool is used only for the purpose of restarting the timer (e.g., if a transmission in one of the resource pools does not enable the WTRU to determine whether the transmission is for a session configured by the WTRU, such as a wake-up signal), the WTRU may use a transmission in another of the resource pools to make such a determination. The WTRU may additionally use the first resource for listening based on a fixed (e.g., configured) period.

[0134] The transition between resources on which listening is performed may be similar to the transition between resource pools as described herein. The WTRU may determine that there is scheduling activity based on listening alone, based on listening and decoding of control information, based on decoding of control information alone, or based on its transmission, and / or whether the WTRU determines that the transmission is associated with a session configured by the WTRU.

[0135] The WTRU may determine the number of candidate time slots for listening based on the transmission activity. In an example, the WTRU may determine the number of candidate time slots for listening based on the transmission activity. For example, in the absence of any transmission / reception associated with a V2X service configured at the WTRU (e.g., L2 ID), the WTRU may use a first number of candidate time slots K1 for the WTRU's listening process. Upon reception / transmission associated with the V2X service, the WTRU may then use a second number of candidate time slots K2 for a period associated with a timer. The WTRU may reset the timer at each reception / transmission associated with such V2X service. The WTRU may return to using K1 candidate time slots for listening upon expiration of the timer.

[0136] In an example, the WTRU may determine the number of candidate time slots for its listening process based on the amount of reception / transmission associated with the V2X service of interest within a recent period or a configurable time window. For example, the WTRU may be configured / preconfigured with a time window (e.g., a time sliding window relative to the current time slot) within which the WTRU measures the number of reception / transmissions associated with the V2X service of interest (e.g., the L2 ID set of interest). The WTRU may be configured with a mapping between a certain number of reception / transmission ranges and a number of candidate time slots for listening. For example, if the number of reception / transmissions in the time window is in the range X=[x1, x2], the WTRU may use a corresponding configured number of candidate time slots K within the selection window [T1, T2].

[0137] In an example, the number of candidate time slots for a WTRU to transmit / listen may be determined based on another parameter or aspect related to an activity behavior, which may be defined as a DRX activity or a listening activity of the WTRU. For example, the WTRU may be configured to have a first number of candidate time slots during the WTRU's on-duration (or a certain number of time slots before or after the on-duration), and a second number of candidate time slots outside its on-duration (or outside of that number of time slots). The on-duration may correspond to the on-duration of another WTRU or group of WTRUs, and / or may be the WTRU's own on-duration. In an example, the WTRU may be configured with a number of candidate time slots determined by the on-duration repetition frequency (e.g., a DRX cycle) at the WTRU, and the number of candidate time slots may change due to a change in the on-duration frequency.

[0138] Dynamic adjustment of the listening window as a function of the transmission activity may be implemented. For example, the WTRU may dynamically adjust its listening activity and / or its listening window based on scheduling activity and / or resource usage (e.g., within a specific resource for a V2X session within a given period), which may be determined based on the channel occupancy (CR) of the WTRU. When the DRX timer T is running, the WTRU may use a first listening window size, when the WTRU determines that there is a transmission activity, the timer may be started or restarted, and when the timer expires, a second listening window size may be used.

[0139] The WTRU may determine that there is scheduling activity based on, for example, listening (e.g., only listening), listening and decoding of control information, decoding of control information only, and / or transmission of control information. The WTRU may determine that the transmission of control information is associated with a session configured by the WTRU. The WTRU may additionally use a first listening window size according to a fixed (e.g., configured) period.

[0140] In an example, the WTRU may determine a set of time slots and / or subchannels to perform listening based on the listening type (e.g., short-term listening or long-term listening). For example, for short-term listening, the WTRU may perform listening in all subchannels of a resource pool. The WTRU may perform listening in a subset of subchannels in the resource pool. The subset of subchannels may be determined based on subchannels of reserved resources and / or subchannels used for resource selection. For example, the WTRU may perform long-term listening to re-evaluate resources reserved for periodic transmission. The WTRU may then perform listening in the set of subchannels reserved for periodic transmission. In an example, the WTRU may perform long-term listening in the set of subchannels used for resource selection.

[0141] Figure 7A timing diagram of exemplary listening windows, sub-windows, and sub-channels that may be used for a listening process 700 performed by a WTRU 701, wherein the listening process 700 includes a long-term partial listening and a short-term partial listening. Figure 7 In the example of , the WTRU 701 may perform long-term listening during one or more long-term partial listening windows / sub-windows 704 in the set of subchannels for resource selection, and the WTRU 701 may perform short-term listening during the short-term partial listening windows 710 in all subchannels of the resource pool. Figure 7 , the short term partial listening window 710 occurs after the WTRU 701 triggers resource allocation at time n and occurs during the resource selection window 706. The short term partial listening window 710 ends before the start of the resource selection sub-window 708. The set of subchannels in the resource selection sub-window 708 is the same as the set of subchannels monitored in the long term partial listening window / sub-window 704.

[0142] In an example, the WTRU may perform partial listening for preemption. The WTRU may determine that it will perform full listening for resource selection. The WTRU may perform partial listening for resource re-evaluation. The WTRU may perform partial listening for resource re-evaluation of selected resources (e.g., resources that have not been reserved by the SCI) and / or reserved resources (e.g., resources that have been reserved by the SCI).

[0143] In an example, the WTRU may trigger listening adaptation by changing the set of resources to perform listening based on any one or more of the following conditions: the WTRU performs resource evaluation / re-evaluation (e.g., after each time the WTRU performs resource allocation and reservation, the WTRU may trigger a change in the set of resources used for listening); and / or if the CBR is greater than or less than a threshold (e.g., if the CBR is greater than and / or less than a threshold, the WTRU may trigger a change in the set of resources used for listening). In an example, the WTRU may perform listening adaptation periodically. For example, the WTRU may periodically perform resource evaluation to determine whether it needs to adjust the set of resources to perform listening. If the criteria for listening adaptation are met, the WTRU may change the set of resources used for listening accordingly.

[0144] In an example, a power saving WTRU may use a bit field in the SCI to indicate its WTRU type, listening type and / or capabilities. For example, for this bit field, one code point may be used to indicate that the WTRU is a power saving WTRU (e.g., PUE) and another code point may be used to indicate that the WTRU is a non-power saving WTRU (e.g., VUE).

[0145] In an example, the WTRU may distinguish between resources reserved by a power saving WTRU and a non-power saving WTRU during resource evaluation / re-evaluation. The WTRU may consider the WTRU type and / or power saving type (e.g., power saving vs. non-power saving) differently during the resource (re)evaluation process. In an example, the WTRU may be (pre)configured with two sets of RSRP thresholds, wherein a first set of RSRP thresholds may be associated with a power saving WTRU (e.g., PUE) and a second set of RSRP thresholds may be associated with a non-power saving WTRU such as a vehicle WTRU (e.g., VUE). In another example, the WTRU may be (pre)configured to apply a different RSRP increment step for resources reserved by a power saving WTRU than for resources reserved by a vehicle WTRU (e.g., non-power saving WTRU). In another example, the WTRU may be (pre)configured with different sets of maximum numbers of RSRP increments based on the type of the WTRU. For example, a maximum number of RSRP increments for a first set associated with a power saving WTRU (e.g., a PUE) may be set to a first configuration value (e.g., a zero or non-zero value), and a maximum number of RSRP increments for a second set associated with a non-power saving WTRU (e.g., a VUE) may be set to a second configuration value (e.g., infinity or another value that may be different from the first configuration value).

[0146] In an example, a WTRU (e.g., PUE) may modify the QoS parameters of its TB and may indicate the modified QoS in the SCI associated with the TB that the WTRU transmits to another WTRU. For example, the power saving WTRU may lower the priority of the data by an offset value and indicate the modified value in the transmitted SCI. The offset may be fixed or may be (pre-)configured based on the priority of the TB. This approach may be motivated to help another non-power saving WTRU (VUE) to prioritize the transmission by the power saving WTRU and / or avoid (not use) the reserved resources of the power saving WTRU.

[0147] Figure 8A flow chart of an exemplary resource allocation process 800 that may be performed by a first WTRU in order for the first WTRU to determine which resources to use for sidelink communications is shown. According to the resource allocation process 800, the first WTRU may determine different threshold parameters to be used during listening based on the power saving mode of another WTRU and / or the power saving type of the other WTRU that reserved the resources. Examples of power saving types of WTRUs include power saving WTRUs (e.g., PUEs) and non-power saving WTRUs (e.g., VUEs, vehicle WTRUs), and examples of power saving modes include a WTRU operating in a first power saving mode and a WTRU operating in a second power saving mode such that operation according to the first power saving mode uses less power than operation according to the second power saving mode. In an example, a power saving WTRU and a WTRU operating in the first power saving mode may have similar priorities and may use the same thresholds (i.e., may be considered equivalent), and a non-power saving WTRU and a WTRU operating in a second power saving mode (e.g., a non-power saving mode or a power saving mode that uses more power than the first power saving mode) may have similar priorities and may use the same thresholds (i.e., may be considered equivalent). The first WTRU may perform listening during a listening window (eg, a long-term partial listening window, a short-term partial listening window), which may occur before or after the first WTRU triggers resource selection.

[0148] At 802, the first WTRU may perform listening by decoding the SCI and measuring the RSRP of the transmission associated with the SCI received from the other (second) WTRU. At 804, the first WTRU may determine when the first WTRU triggers resource selection. For example, when the first WTRU has data to be sent to another (second) WTRU via the side link, the first WTRU may trigger resource selection. Under the condition that the first WTRU triggers resource selection, at 806, the first WTRU may determine the availability of each of the multiple resources in the resource selection window by repeating the steps in 809 for each of the multiple resources allocated to the resource selection window. For example, the multiple resources may be a resource pool for transmission. For example, the resource pool for transmission may be configured / (pre-)configured at the WTRU for possible sidelink transmission (e.g., by an eNB or by another WTRU). In an example, the resources in the resource pool may be a set of consecutive subchannels in a time slot. At 808, for each resource, the first WTRU may determine whether the resource is reserved by another (second) WTRU, for example, based on the last transmission of the SCI received by the first WTRU from the second WTRU. If the resources are not reserved by another (second) WTRU, then at 818 the first WTRU may add the resources to the set of available resources.

[0149] If the resource is reserved by another (second) WTRU, then at 810, the first WTRU may determine whether the resource is reserved by a second WTRU that is a power saving WTRU (e.g., a PUE) and / or a WTRU in a power saving mode. For example, the first WTRU may determine whether the resource is reserved by a second WTRU that is a power saving WTRU and / or a WTRU in a power saving mode by verifying an indicator of a power saving mode and / or a power saving type in an SCI received from the second WTRU or another WTRU. If the first WTRU determines that the resource is reserved by a second WTRU that is a power saving WTRU and / or a WTRU in a power saving mode, then at 814, the first WTRU may apply the first set of RSRP parameters and / or RSRP increments as selected RSRP parameters and / or selected RSRP increments for determining resource availability. If the first WTRU determines that the resources are reserved for a second WTRU that is a non-power saving WTRU and / or a WTRU that is not in a power saving mode, then at 812, the first WTRU may apply a second set of RSRP parameters and / or RSRP increments as selected RSRP parameters and / or selected RSRP increments for determining resource availability. In one example, the first WTRU may be configured / preconfigured with a lower RSRP threshold when the second WTRU is a power saving mode WTRU, and the first WTRU may be configured / preconfigured with a higher RSRP threshold when the second WTRU is a non-power saving mode WTRU. Using different thresholds, the first WTRU may be able to avoid selecting reserved resources for another WTRU that is a power saving mode WTRU, which may help protect transmissions of the power saving mode WTRU. The RSRP parameters may include at least one RSRP threshold for determining the use of resources.

[0150] At 816, the first WTRU uses the RSRP threshold from the selected RSRP parameter and determines whether the measured RSRP of the resource under consideration is below the RSRP threshold. If the measured RSRP of the resource is below the RSRP threshold, then at 818, the first WTRU adds the resource to a set of available resources. Steps 808 to 818 are repeated for all resources in the resource selection window. At 820, the first WTRU performs resource selection from the determined set of available resources (e.g., during the resource selection window).

[0151] Fig. 9 A timing diagram of an exemplary resource selection (resource allocation) process 900 that may be performed by a first WTRU 901 is shown. Fig. 9 The exemplary resource selection process 900 shown in FIG. 1 may correspond to Figure 8 The exemplary resource allocation process 800 shown, or any subset of the exemplary resource allocation process 800. Fig. 9, the first WTRU 901 may perform a sense of the availability of the plurality of resources 904, for example by receiving and decoding the SCI from the other (second) WTRUs, to determine whether any of the plurality of resources 904 is reserved by any of the other (third) WTRUs. This sense may occur during the sense window 902 and may occur before the WTRU 901 triggers resource selection at time n. Fig. 9 In the example of , other WTRUs may transmit in all of the plurality of resources 904, as determined during the listening window 902. The SCI associated with each transmission in the resources 904 reserves one resource 908 in the resource selection window 906. Therefore, during the resource selection window 906, all of the plurality of resources 908 may be reserved by other WTRUs and may not be used for transmission by the first WTRU 901.

[0152] In an example, the WTRU may perform CBR measurements based on the set of subchannels and time slots sensed. The WTRU may measure the CBR using one or more of the following: long-term partial sensing, short-term partial sensing, or both long-term and short-term partial sensing. In an example, the WTRU may perform CBR measurements using long-term partial sensing. The WTRU may measure the sidelink received signal strength indicator (RSSI) in the set of subchannels and time slots used for long-term partial sensing. The WTRU may calculate the CBR as the ratio of the number of busy subchannels to the total number of subchannels. If the RSSI is greater than a threshold, the subchannel may be considered busy. In an example, the WTRU may perform CBR measurements using short-term partial sensing. The WTRU may measure the sidelink RSSI in the set of subchannels and time slots used for short-term partial sensing. The WTRU may calculate the CBR as the ratio of the number of busy subchannels to the total number of subchannels. In an example, the WTRU may perform CBR measurements using both short-term and long-term partial sensing. The WTRU may measure the sidelink RSSI in the set of subchannels and time slots used for both short-term and long-term partial sensing. The WTRU may then calculate the CBR as the ratio of the number of busy subchannels to the total number of subchannels.

[0153] In an example, the WTRU may determine the resource selection timing of the TB. Fig.10 A timing diagram showing an example of a resource selection timing procedure 1000 for a TB that may be performed by a WTRU 1001 is shown. Fig.10An example of timing parameters for resource selection timing of a TB is shown. For example, the WTRU 1001 may determine any one or more of the following resource selection timing parameters that may be related to the resource selection window 1006: the resource selection trigger time (i.e., the timing of n); the start of the initial resource selection window 1020 (i.e., the timing of n+T1); the end time of the resource selection window 1020 (i.e., the timing of n+T2); the timing of the first candidate time slot 1008 (i.e., n+m), so that the candidate time slot may be a time slot that the WTRU can evaluate the availability of resources for potential resource selection; and / or the timing of the last candidate time slot 1010 (i.e., n+M). In the example, the WTRU 1001 may determine the resource selection timing parameters in response to the arrival of the TB at time T0.

[0154] In an example, the WTRU may determine any one or more of the parameters related to the resource selection timing of the TB (e.g., minimum / maximum values ​​of T1, T2, T2-T1, m, M, Mm, etc.) based on any one or more of the following conditions: resource selection type (e.g., random-based, full listening-based, and / or partial listening-based); QoS of the TB; CBR of the resource pool and / or CR of the WTRU; timing of the first candidate time slot, packet arrival time, and / or the gap between the packet arrival time and the first candidate time slot; whether to enable / disable the resource (re-selection); the number of candidate time slots and / or the number of candidate resources in a period; the HARQ type of the TB (e.g., HARQ-enabled and HARQ-disabled TBs); the broadcast type of the TB (e.g., broadcast, unicast, or multicast); the DRX state of the WTRU; the power saving mode of the WTRU; whether the WTRU performs resource selection for initial selection, (re)evaluation of selected resources, or (re)evaluation of reserved resources; whether semi-persistence is enabled / disabled in the resource pool; and / or the resource selection type of the TB.

[0155] For this resource selection type, if the WTRU performs random resource selection, the WTRU may trigger resource selection for the TB upon packet arrival. The WTRU may trigger resource selection for the TB at least / at most transmit (Tx) timeslots before the first candidate timeslot. For example, with respect to enabling / disabling resource (re)evaluation, if resource (re)evaluation is enabled, the WTRU may trigger resource selection for the TB at least or at most Tx timeslots before the first candidate timeslot. In another example, if resource (re)evaluation is disabled, the WTRU may trigger resource selection for the TB at least or at most Ty timeslots before the first candidate timeslot. The values ​​of Tx and / or Ty may be (pre-)configured per resource pool based on other parameters such as QoS of the TB, the time gap between the packet arrival time and the first candidate timeslot.

[0156] For the QoS of the TB, the WTRU may be (pre-)configured with the minimum / maximum values ​​of the first and / or last candidate time slots (i.e., m and M) according to the QoS of the TB (e.g., the priority of the TB). The WTRU may then determine the values ​​of m and M accordingly based on the QoS of the TB.

[0157] For the CBR of the resource pool and / or the CR of the WTRU, the WTRU may be (pre-)configured with multiple sets of resource selection timing parameters (e.g., minimum / maximum values ​​of T1, T2, T2-T1, m, M, Mm, etc.), where each set of parameters may be associated with a certain range of CBR and / or a certain range of CR. The WTRU may then determine which set of resource selection timing parameters to use based on the CBR of the resource pool and / or the CR of the WTRU.

[0158] For DRX, the WTRU may be (pre-)configured with multiple sets of resource selection timing parameters (e.g., minimum / maximum values ​​of T1, T2, T2-T1, m, M, Mm, etc.), where each set of parameters may be associated with one DRX state of the WTRU. In an example, when DRX is not (pre-)configured, the WTRU may be (pre-)configured with one set of resource selection timing parameters, and when DRX is configured, the WTRU may be configured with another set of parameters. In an example, the WTRU may be (pre-)configured with multiple sets of resource selection timing parameters, where a first set of parameters may be used when DRX is not configured, a second set of parameters may be used when the WTRU is in a DRX on duration, and a third set of parameters may be used when the WTRU is in a DRX off duration.

[0159] For power saving modes, the WTRU may be (pre)configured with multiple power saving modes, and in each power saving mode, the WTRU may be (pre)configured with a corresponding set of resource selection timing parameters. The WTRU may then determine which set of resource selection timing parameters to use based on its power saving mode.

[0160] For a resource selection type, the WTRU may be (pre-)configured with multiple sets of resource selection timing parameters (e.g., minimum / maximum values ​​of T1, T2, T2-T1, m, M, Mm, etc.), where each set of resource selection timing parameters may be associated with a corresponding resource selection type. The WTRU may then determine a range of CBRs and / or a range of CRs. The WTRU may then determine which set of resource selection timing parameters to use based on the CBR of the resource pool and / or the CR of the WTRU.

[0161] For example, for the number of candidate time slots and / or the number of candidate resources within a period, the WTRU may determine the resource selection trigger time based on the number of candidate time slots within a period (e.g., the period from the packet arrival time to the PDB). For example, if the number of candidate time slots is greater than the minimum number of required candidate time slots, the WTRU may continue to perform listening and trigger resource selection when the number of candidate time slots equals the minimum number of candidate time slots. Otherwise, the WTRU may trigger resource selection when a packet arrives.

[0162] For example, for the HARQ type of the TB (e.g., HARQ-enabled and HARQ-disabled TBs), the WTRU may (pre-)configure a minimum number of candidate time slots and / or a minimum resource selection window (e.g., a minimum value of [n+m, n+M]) based on the HARQ type of the TB. The WTRU may determine the resource selection window based on whether the TB has HARQ enabled / disabled to satisfy the minimum number of required candidate resources and / or the minimum resource selection window accordingly. For example, for a HARQ-enabled TB, the WTRU may be (pre-)configured with a first value of (Mm), and for a HARQ-disabled TB, the WTRU may be (pre-)configured with a second value of (Mm), wherein the second value of (Mm) is less than the first value of (Mm).

[0163] In an example, the DRX state of the WTRU may include any one or more of the following criteria: whether DRX is configured; and / or whether the WTRU is in an on duration or an off duration. In an example, the WTRU may determine whether to use a physical sidelink shared channel (PSSCH) demodulation reference signal (DMRS) or a physical sidelink control channel (PSCCH) to measure the availability of the channel based on whether DRX is configured and / or whether the WTRU is in a DRX on duration or an off duration. For example, if DRX is configured and / or the WTRU is in an on duration, the WTRU may determine to use the PSCCH DMRS. In an example, if DRX is not configured and / or the WTRU is in an off duration, the WTRU may determine to use the PSSCH DMRS.

[0164] In an example, the WTRU may be (pre)configured with three numbers of candidate time slots for initial resource selection, (re)evaluation of selected resources, and (re)evaluation of reserved resources, with respect to whether the WTRU is performing resource selection for initial selection, (re)evaluation of selected resources, or (re)evaluation of reserved resources. The WTRU may then determine the resource selection window accordingly to satisfy the required minimum number of candidate time slots for initial selection, (re)evaluation of selected resources, or (re)evaluation of reserved resources.

[0165] Based on the example of resource allocation, the WTRU may determine the resource selection type. The WTRU may determine any of the following resource allocation types for the TB: based on listening (e.g., based on full listening or based on partial listening); and / or random. The determination of the resource allocation type for the TB may be based on one or more of the following criteria: configuration / pre-configuration; packet arrival time; QoS of data; CBR of the resource pool; availability of listening results; number of timeslots sensed within the resource selection window; and / or remaining available battery life.

[0166] In an example, the resource pool may allow both random resource allocation and listening-based resource selection. The WTRU may determine whether to perform random resource allocation or listening-based resource selection based on the QoS of the TB. For example, if the priority of the TB is less than a threshold, the WTRU may perform random resource selection, and if the priority of the TB is less than a threshold, the WTRU may perform listening-based resource selection.

[0167] In an example, the WTRU may determine whether to perform a sensed based resource allocation or a random resource selection in a resource pool based on the number of time slots sensed in a listening window (e.g., the number of time slots sensed may refer to the number of time slots sensed in a long-term partial listening window or a short-term partial listening window or both listening windows). For example, if the number of time slots sensed in the listening window is less than a threshold, the WTRU may determine to perform a random resource selection or to discard a TB. Otherwise, the WTRU may determine to perform a sensed based resource allocation.

[0168] In an example, the WTRU may configure / preconfigure two sets of resource pools, one of which may be associated with transmissions to power saving WTRUs (e.g., PUEs) and the other may be associated with transmissions to non-power saving WTRUs (e.g., VUEs). The WTRU may further configure / preconfigure two sets of destinations (or any indication related to services that may be used to distinguish target WTRUs as VUEs and / or PUEs), one of which is not associated with power saving WTRUs (e.g., PUEs) and the other is associated with power saving WTRUs (e.g., PUEs). The WTRU may determine the transmit resource pool to use based on whether the destination is associated with a power saving WTRU (e.g., PUE).

[0169] In an example, the WTRU may configure / pre-configure a resource pool. The WTRU may determine the set of subchannels and / or time slots to perform resource allocation for transmitting the TB based on the target WTRUs for the TB within the resource pool, such as whether the target WTRU has a power saving WTRU (e.g., a PUE). For example, if the PUE is not included in the set of target WTRUs, the WTRU may perform resource allocation in all subchannels; otherwise, the WTRU may perform resource selection in a subset of subchannels. The subset of subchannels may be determined based on one or any of the location of the WTRU, the CBR of the resource pool, and / or the QoS of the TB.

[0170] In an example, a WTRU (e.g., a PUE) may apply a timing restriction between two selected resources when it performs resource selection. The WTRU may select a time gap between two transmission resources (e.g., a time gap between an initial transmission and a first retransmission) that is above a threshold. The threshold may be (pre)configured according to a transmission priority, or it may be fixed per resource pool. This approach may be triggered to support other WTRUs (e.g., VUEs) in resource re-evaluation to detect potential conflicts. In an example, the WTRU may determine the set of selectable resources (e.g., the set of resources to be reported to the MAC layer) based on its time / frequency region. In one approach, the WTRU may divide the set of time / frequency resources into multiple of the following groups: a set of listening-based selection resources; and / or a set of randomly selected resources. The WTRU may determine the set of selectable resources by first selecting from the set of listening-based resources. If the set of selectable resources in the sensed time / frequency resources is less than a threshold, the WTRU may further select resources from the set of randomly selected resources.

[0171] Mechanisms may be used for resource evaluation / re-evaluation. In an example, the physical (PHY) layer of the WTRU (e.g., VUE) may perform resource evaluation by determining the set of selectable resources to be reported to the medium access control (MAC) layer. The MAC layer may randomly select one or more resources from the set of resources reported by the PHY layer for transmitting a TB.

[0172] In an example, the WTRU may perform a resource evaluation / re-evaluation. The WTRU may perform a resource evaluation / re-evaluation by one or more of determining whether its selected / reserved resources conflict with any reserved resources from other WTRUs, selecting new resources for the WTRU transmission, discarding a TB, and / or discarding a reserved resource that conflicts with another WTRU.

[0173] In an example, the WTRU may perform resource evaluation / re-evaluation by performing one or more of the following operations to determine whether its selected / reserved resources conflict with any reserved resources from other WTRUs. The WTRU may determine whether its reserved resources conflict with any reserved resources from other WTRUs by evaluating the listening results in a subset of listening resources. For example, the WTRU may evaluate time slots and / or sub-channels, where transmissions in these time slots and / or sub-channels may reserve resources that conflict with potential transmissions of the WTRU. The WTRU may perform this type of resource evaluation / re-evaluation periodically or based on an event. The event may be based on the WTRU performing resource selection / reselection, and / or the CBR of the resource pool being greater than / less than one or either of the thresholds.

[0174] The WTRU may perform resource evaluation / re-evaluation in one of the evaluation / re-evaluation of selected resources and / or the evaluation / re-evaluation of reserved resources. In the evaluation / re-evaluation specifically implemented for selected resources, the WTRU may perform resource evaluation / re-evaluation after it has selected the resources for transmitting the TB and before it transmits the SCI to reserve the resources. In the evaluation / re-evaluation specifically implemented for reserved resources, the WTRU may perform resource evaluation / re-evaluation on resources that have been reserved by the WTRU's SCI. Resources may be semi-persistently reserved for different TBs, or resources may be dynamically reserved for retransmissions of the same TB. The WTRU may perform evaluation / re-evaluation before transmitting the TB for semi-persistent reservation. In another example, it may perform evaluation / re-evaluation after the initial transmission of the TB for dynamic reservation.

[0175] The WTRU may perform resource evaluation when resource selection is triggered. For example, the WTRU may determine whether to trigger resource evaluation / re-evaluation (evaluation / re-evaluation of selected resources and / or evaluation / re-evaluation of reserved resources) or not trigger resource evaluation / re-evaluation based on one or more of the following exemplary criteria: whether the WTRU performs short-term partial listening; QoS of the TB; CBR of the resource pool; amount of selectable resources of the resource; HARQ retransmission type of the TB; whether the WTRU performs semi-persistent reservation for the TB; reservation period of the semi-persistent reservation; period of resource evaluation / re-evaluation; and / or whether semi-persistent reservation is enabled / disabled.

[0176] In an example, the WTRU may determine whether to trigger resource evaluation / re-evaluation based on whether it performs short-term partial listening. For example, if short-term partial listening is not performed, the WTRU may not trigger a re-evaluation of the selected resource. In an example, the WTRU may determine whether to trigger resource evaluation / re-evaluation based on the QoS of the TB. For example, if the priority of the TB is greater than a threshold, the WTRU may trigger a resource re-evaluation, and if the priority of the TB is less than a threshold, it may not trigger a resource re-evaluation.

[0177] In an example, the WTRU may determine whether to trigger resource evaluation / re-evaluation based on the CBR of the resource pool. For example, if the CBR of the resource pool is greater than a threshold, the WTRU may trigger resource re-evaluation. Otherwise, the WTRU may determine not to trigger resource re-evaluation.

[0178] In an example, the WTRU may determine whether to trigger resource evaluation / re-evaluation based on the amount of optional resources used for resource selection. For example, if the amount of optional resources in the last resource evaluation / re-evaluation is less than a threshold, the WTRU may trigger resource evaluation / re-evaluation. Otherwise, the WTRU may not trigger resource evaluation / re-evaluation. In an example, the WTRU may determine whether to trigger resource evaluation / re-evaluation based on the HARQ retransmission type of the TB. For example, if the WTRU performs blind retransmission for the TB, the WTRU may trigger resource re-evaluation, and if the WTRU performs HARQ-based retransmission or a mix of HARQ-based and blind retransmission, resource re-evaluation may not be triggered.

[0179] In an example, the WTRU may determine whether to trigger resource evaluation / re-evaluation based on whether the WTRU performs a semi-persistent reservation for a TB. For example, if the WTRU performs a semi-persistent reservation, the WTRU may trigger a resource re-evaluation, and if the WTRU does not perform a semi-persistent reservation, it may not trigger a resource re-evaluation. In an example, the WTRU may determine whether to trigger a resource evaluation / re-evaluation based on a reservation period of a semi-persistent reservation. For example, if the reservation period is less than a threshold, the WTRU may perform a resource evaluation / re-evaluation, and if the reservation period is greater than a threshold, it may not perform a resource evaluation or re-evaluation. The threshold for the reservation period that determines whether the WTRU needs to perform a resource evaluation / re-evaluation may be configured / pre-configured per resource pool.

[0180] In an example, the WTRU may determine whether to trigger resource evaluation / re-evaluation based on the period of resource evaluation / re-evaluation. For example, the WTRU may configure / pre-configure a minimum period to perform resource evaluation / re-evaluation for each side link process. The WTRU may determine whether it performs resource evaluation / re-evaluation on the transmission of a specific TB based on the time gap between the reserved resources of the current TB and the reserved resources of the last TB to be evaluated / re-evaluated. For example, if the time gap is greater than a threshold, the WTRU may perform resource evaluation / re-evaluation; otherwise, the WTRU may not trigger resource evaluation / re-evaluation. This method may be triggered to allow the WTRU to skip monitoring for a period of time to save power. In an example, the WTRU may determine whether to trigger resource evaluation / re-evaluation based on whether semi-persistent reservation is enabled / disabled. For example, if semi-persistence is disabled in the resource pool, the WTRU may trigger resource evaluation / re-evaluation; otherwise, the WTRU may not trigger resource evaluation / re-evaluation.

[0181] The WTRU may trigger resource evaluation and / or resource allocation based on one or more of the timing of the first heard / optional timeslot in the resource selection subwindow, the termination of the short-term partial listening, and the periodicity. In an example, the WTRU may trigger resource evaluation and / or resource allocation based on the timing of the first heard / optional timeslot in the resource selection subwindow. For example, the WTRU may trigger resource selection and / or resource evaluation at least T3 timeslots before the first listening timeslot in the resource selection window. The value of T3 or the minimum / maximum value of T3 may be (pre-)configured or determined by the WTRU based on the QoS of the TB. This approach may allow the WTRU to have available resources to select within the heard timeslot. In an example, the WTRU may trigger resource evaluation and / or resource allocation based on the termination of the short-term partial listening. For example, when the WTRU completes the short-term partial listening, the WTRU may trigger resource re-evaluation.

[0182] In an example, the WTRU may trigger resource evaluation and / or periodicity based on resource allocation. For example, the WTRU may determine to periodically perform resource (re)evaluation for a semi-persistent reservation of a sidelink process. For example, the WTRU may perform resource (re)evaluation every N TBs transmitted. The value of N may be configured / preconfigured and / or may be determined based on the reservation period of the sidelink process.

[0183] The WTRU may perform a resource (re)assessment on a semi-persistently reserved resource. In an example, the WTRU may perform a resource (re)assessment on a semi-persistently reserved resource. The WTRU may be (pre)configured with a minimum number of resources and / or periods to be (re)assessed based on any one or more of the following criteria: the QoS of the TB; and / or the periodicity of the semi-persistent reservation. In an example, the WTRU may perform a resource (re)assessment to meet the minimum number of resources and / or periods to be (re)assessed. For example, the WTRU may be (pre)configured to perform a resource (re)assessment at least once every N time slots. The value of N may be (pre)configured according to the QoS of the TB. The WTRU may then determine to perform a resource (re)assessment in a period after every N time slots. The WTRU may determine to perform a resource (re)assessment periodically and / or dynamically.

[0184] The WTRU may determine the set of subchannels to select based on the resource selection type. For example, if the WTRU performs random resource selection, the WTRU may select resources from all subchannels configured for the resource pool. However, if the WTRU performs listening-based resource selection, the WTRU may select resources from subchannels that are heard. In an example, the WTRU may perform resource selection to determine a set of resources for transmission. The WTRU may further select one or more other sets of resources for backup. If the WTRU detects a potential conflict in the first set of transmission resources, the WTRU may select the set of backup resources for potential transmission.

[0185] The WTRU may apply a time / frequency restriction between the set of resources used for transmission and the set of resources used for backup. The WTRU may select a transmission resource and its associated backup resource that meet any one or more of the following criteria; the time gap between the two selected resources is less than or equal to a threshold (the time gap threshold may be zero, for example, in which case the two selected resources may be in the same time slot); the frequency gap between the two resources is less than the threshold or the two selected resources belong to a subset of subchannels; and / or the frequency gap between the two selected resources is greater than the threshold or the two selected resources belong to different subsets of subchannels. In an example, the WTRU may select a transmission resource and its associated backup resource to be in the same time slot and / or in the same set of subchannels. This approach may reduce the listening time for the WTRU.

[0186] In an example, the WTRU may perform a short-term partial listening before performing a resource reassessment of the reserved resources and / or backup resources. The size of the listening window may be (pre)configured based on any one or more of the following criteria: the QoS of the TB and / or the CBR of the resource pool (e.g., the WTRU may be (pre)configured with a minimum listening window and / or a minimum number of listening slots according to the priority of the TB and / or the CBR of the resource pool before performing a resource reassessment, and the WTRU may then determine the listening window based on these parameters); and / or the periodicity of the reserved resources (e.g., if the periodicity of the reserved slots is large, the WTRU may select a long listening window, or the WTRU may select a short listening window). In an example, the WTRU may be (pre)configured with the set of time / frequency resources to perform listening, thereby detecting potential conflicts in the time / frequency resources. The WTRU may then determine the listening resources to detect potential conflicts based on the (pre)configured time / frequency relationship and the set of time / frequency resources that the WTRU targets for performing listening.

[0187] The WTRU may determine to perform resource reassessment on its reserved resources and / or backup resources. The WTRU may determine how often the WTRU performs resource reassessment on a set of semi-persistently reserved resources (e.g., SPS procedures) and / or backup resources based on any one or more of the following criteria: QoS of the TB (e.g., for each transmit priority, the WTRU may be (pre-)configured with a minimum number of resource reassessments per N reservation periods, and / or a minimum number of resource reassessments per fixed duration (e.g., 1 s), and the WTRU may then randomly determine the transmit period at which to perform resource reassessment to satisfy the required resource reassessment criteria); reservation periodicity (e.g., the WTRU may be (pre-)configured to perform resource reassessment for Y number of transmission priorities); at least X resource reassessments for a transmission such that the WTRU may then randomly select X resource reassessments from the Y transmissions, and the value of X may be configured based on the priority of the TB such that when the value of X may be zero, the WTRU may determine not to perform resource reassessments); the number of reserved resources per reservation period (e.g., the WTRU may determine the number of resource reassessments based on the number of more resources reserved in the reservation period); and / or the CBR of the resource pool (e.g., when the CBR is higher, the WTRU may be required to perform more resource reassessments, while when the CBR is lower, the WTRU may be required to perform fewer resource reassessments).

[0188] If the WTRU detects a conflict, the WTRU may reselect a transmit resource. For example, if the WTRU detects a potential conflict in a transmit resource, the WTRU may perform any one or more of the following actions. In a first exemplary action, the WTRU may replace the transmit resource with a corresponding resource. In a second exemplary action, the group of transmit resources may be replaced with the group of backup resources. The WTRU may perform the first exemplary action on a TB with HARQ disabled, and the WTRU may perform the second exemplary action on a TB with HARQ enabled. In the example, if the WTRU detects a potential conflict in a backup resource, the WTRU may reselect the backup resource. If the WTRU cannot select a backup resource that meets the time and / or frequency constraints, the WTRU may reselect both the backup resource and the corresponding transmit resource.

[0189] In an example, the WTRU may perform silencing on the SPS sidelink process. The WTRU may perform one or more of the following exemplary processes: the WTRU may determine that the reserved resources are not used in one or more reservation periods; the WTRU may determine that the one or more reserved resources are not used in a period; and / or the WTRU determines that the reserved resources are not used in one or more reservation periods and determines that the one or more reserved resources are not used in a period. For example, the WTRU may use the first exemplary method in a first time period and the second exemplary method in another time period. In an example, the WTRU may determine which period and / or which resource to silence based on any one or more of the following criteria: the QoS of the TB; the periodicity of the reserved resources; and / or the CBR of the resource pool (for example, the WTRU may silence more resources in a congested scenario, such as when the CBR is high, and the WTRU may silence fewer resources in a non-congested scenario, for example, when the CBR is low). In an example, the WTRU may double the resource reservation period for transmission before the silent period. If the WTRU determines to mute transmissions in the current cycle, the WTRU may indicate twice the reservation period in the SCI of the previous cycle. This method will reserve resources in the next cycle if available.

[0190] The WTRU may perform resource selection for a TB during a silent period. During a silent period, if a TB is available, the WTRU may use another resource pool to perform transmission during this period. The WTRU may use a resource pool (e.g., an exception resource pool) that allows random resource selection to transmit a TB. In an example, the WTRU may use dynamic resource selection to select transmission resources for the current TB. The WTRU may perform resource reassessment to determine the availability of a reserved SPS sidelink process. For example, when the WTRU is not transmitting in a reserved resource, the WTRU may perform reception in a reserved time slot to determine whether there are any overlapping transmissions in the reserved time slot. If there is no transmission in the reserved resources, the WTRU may continue to use these reserved time slots in the next period. If the WTRU detects a transmission in the reserved resources, the WTRU may decode the SCI of the transmission, and the WTRU may perform any one or more of the following operations: if the SCI indicates a dynamic transmission, the WTRU may continue to use the reserved resource in the next period; and / or if the SCI indicates an SPS transmission, the WTRU may determine whether to use the reserved time slot in the next period based on the conflict percentage. For example, if the conflict percentage in the SPS side link process is higher than a threshold (the threshold may be zero or greater than zero), the WTRU may determine to reselect another resource. However, if the conflict percentage is less than the threshold, the WTRU may continue to use the SPS side link process.

[0191] A mechanism for switching on / off listening of a resource pool may be used. The WTRU may be configured / pre-configured for multiple resource pools associated with different broadcast types, service types, and / or listening types. In an example, the WTRU may be configured to monitor multiple resource pools. Each resource pool may be associated with one or more of a listening type, a broadcast type, and / or a service type.

[0192] In an example, each resource pool may be associated with a listening type. For example, the WTRU may be configured / preconfigured with a resource pool to perform default listening, in which the WTRU may perform continuous listening. The WTRU may further configure / preconfigure one or more other resource pools to perform non-continuous listening. For example, the WTRU may perform listening in these resource pools partially or based on event triggers. In an example, each resource pool may be associated with a broadcast type. For example, the WTRU may be configured with one resource pool associated with broadcast or all broadcasts and one or more other resource pools associated with unicast and / or multicast. In an example, each resource pool may be associated with a broadcast type. For example, the WTRU may be configured with one or more resource pools associated with basic security services and one or more resource pools associated with advanced services. In another example, the WTRU may be configured with a set of resource pools associated with power-saving WTRUs (e.g., PUEs) and another set of resource pools associated with non-power-saving WTRUs (e.g., VUEs).

[0193] The WTRU may trigger or start listening in another resource pool. In an example, when the WTRU receives data / control from the second resource pool that triggers listening in the second resource pool (implicitly or explicitly), the WTRU may perform listening in the first resource pool. For example, the WTRU may be configured to monitor multiple resource pools, each of which may be associated with one or more services. The WTRU may be further configured in a resource pool in which it performs listening to continuously or periodically determine listening activities in other resource pools. According to an example, the WTRU may be configured / pre-configured in a first default resource pool to perform continuous monitoring, and configured / pre-configured in a second default resource pool for non-continuous monitoring. In the first default resource pool, the WTRU may receive control and / or data from a second WTRU (e.g., a peer WTRU with which the WTRU is conducting a unicast session), which control and / or data may trigger the first WTRU to perform listening in another second resource pool. The control or data from the second (peer) WTRU may include any of the following information: the second (peer) WTRU initiating a unicast / multicast session in another resource pool; the second (peer) WTRU switching the unicast / multicast data to another resource pool; and / or time / frequency resources used for the unicast / multicast session.

[0194] The WTRU may switch off listening in a resource pool. In an example, the WTRU may determine to switch off listening in a resource pool based on any one or more of the following criteria: the WTRU detects / declares a radio link failure (RLF) for one or more links with services associated with the resource pool (e.g., by the WTRU using an access stratum (AS) layer or upper layer scheme); the WTRU receives (implicitly or explicitly) an indication from a gNB, other node, or peer WTRU to terminate a unicast / multicast session (e.g., the WTRU may receive an SCI that resources are not reserved for transmitting future TBs in the same unicast / multicast session, and the WTRU may then terminate the unicast session and turn off listening in the associated resource pool); the WTRU fails to detect control and / or data for a unicast / multicast session in one or more reserved resources of one or more sidelink processes for the unicast / multicast session; and / or the WTRU terminates a unicast session in a non-continuous listening resource pool.

[0195] In an example, a process may be used for random resource selection. In an example, a WTRU may determine whether to use listening-based or random resource selection in a resource pool. The WTRU may be configured with a resource pool that allows both random resource selection and listening-based resource selection. The WTRU may determine which resource selection scheme to use based on any one or more of the following criteria: the power saving mode / state of the WTRU; the CBR of the resource pool; the CR of the WTRU; the broadcast type of the TB; and / or the QoS of the TB; and / or the timing of the first candidate time slot, the timing of the last candidate time slot, the packet arrival time, and / or the gap between the packet arrival time and the first candidate time slot.

[0196] In an example of a timing-based resource selection scheme criterion, the WTRU may perform a random selection if the time gap between the packet arrival time and the first candidate time slot is less than a threshold. The threshold may be (pre)configured based on the QoS of the TB and / or the CBR of the resource pool. In an example, the WTRU may determine to perform a random-based resource selection if the number of candidate time slots that satisfy the PDB of the TB is less than a threshold. The threshold may be (pre)configured based on the QoS of the TB (e.g., priority) and / or the CBR of the resource pool.

[0197] In an example, the WTRU may determine whether it may perform random resource allocation based on the power saving mode and / or power saving state of the WTRU. For example, the WTRU may be configured in two sets of power saving modes / states. In a first set of power saving modes / states, random resource selection may be allowed, while in a second set of power saving modes or states, random selection may not be allowed. The power saving modes / states of the WTRU may be modeled by the sidelink and / or Uu interface activities of the WTRU.

[0198] In an example, the WTRU may determine whether it can perform random resource allocation based on the CBR of the resource pool. For example, when the CBR of the resource pool is less than a threshold, the WTRU may perform random resource selection, and if the CBR of the resource pool is greater than another threshold, the WTRU may perform a sense-based resource allocation. In an example, the WTRU may determine whether it can perform random resource allocation based on the channel occupancy ratio (CR) of the WTRU. For example, when the CR is less than a threshold, the WTRU may perform random resource selection; otherwise, the WTRU may be required to perform a sense-based resource selection. The CR of the WTRU may be calculated / determined based on resources transmitted and / or reserved from different resource selection types (e.g., random-based, partial sense-based, and full sense-based). For example, the WTRU may calculate three CRs, wherein a first CR may be used to evaluate the channel occupancy of the selected resource using random selection, a second CR may be used to evaluate the occupancy of the selected resource using sense-based selection, and a third CR may be used to evaluate the occupancy ratio of all resources. The WTRU may then determine whether to randomly select a resource based on the first CR.

[0199] In an example, the WTRU may determine whether it can perform random resource allocation based on the broadcast type and / or HARQ type of the TB. For example, the WTRU may be allowed to perform random selection for a broadcast TB, but may not be allowed to perform random selection for a unicast / multicast TB. In another example, the WTRU may be allowed to perform random selection for a HARQ-disabled TB, but may not be allowed to perform random selection for a HARQ-enabled TB. In an example, the WTRU may determine whether it can perform random resource allocation based on the QoS of the TB. For example, the WTRU may be allowed to perform random selection for a set of priorities, and may not be allowed to perform random selection for another set of priorities. For example, if the priority of the TB and / or the delay of the TB is less than a threshold, the WTRU may be allowed to perform random selection. Otherwise, the WTRU may not be allowed to perform random selection. The priority and / or delay threshold may be configured per resource pool and / or per service.

[0200] In an example, the WTRU may indicate a resource selection mode and / or a power saving mode in a message. For example, the WTRU may use an SCI (e.g., SCI 1 or SCI) to indicate a resource allocation mode and / or a power saving mode for a transmit resource. The WTRU may use one or more of the following exemplary fields or indicators to indicate a resource allocation mode and / or a power saving mode for a transmit resource: a field in a first SCI and / or a second SCI; and / or a second SCI format. For example, the WTRU may use one SCI format for one set of power saving modes and / or resource allocation modes and another second SCI format for another set of power saving modes and / or resource allocation modes. In an example, the WTRU may prioritize resources reserved by different resource selection modes and / or power saving modes. For example, the WTRU may decode the SCI to determine a resource selection mode and / or a power saving mode associated with a reserved resource. When determining the availability of each reserved resource, the WTRU may then use different RSRP thresholds (e.g., such as Figure 8 ).

[0201] In an example, the WTRU may determine whether to reselect a conflicting resource based on a resource selection mode and / or a power saving mode indicated in the SCI. The WTRU may determine whether the WTRU should reselect a resource due to a resource re-evaluation procedure based on a resource selection mode and / or a power saving mode associated with a reserved resource. For example, if a resource selected / reserved by the WTRU conflicts with a resource reserved by a random selection procedure, the WTRU may perform a resource reselection regardless of the priority associated with the resource. This approach may avoid conflicts with randomly selected resources.

[0202] In an example, the WTRU may determine a resource selection window for a TB. The WTRU may use different groups of time slots to select resources for initial transmission and retransmission of the TB. For example, the WTRU may determine the group of partially heard time slots and non-heard time slots in the resource selection window. The WTRU may then randomly select an initial transmission from the group of available / optional resources in the group of partially heard time slots. The WTRU may then randomly select a retransmission resource from the group of heard and / or non-heard resources. This approach may reduce the probability of collision for the initial transmission of the TB.

[0203] In an example, the WTRU may perform a resource re-evaluation after the random selection. The WTRU may determine whether to perform a resource (re)evaluation on the randomly selected resource based on any one or more of the following criteria: resource pool configuration; QoS of the TB; CBR of the resource pool and / or CR of the WTRU; timing between the resource selection time and the first selected resource; HARQ type of the TB (e.g., HARQ-enabled and HARQ-disabled TBs); DRX state of the WTRU; power saving mode of the WTRU; and / or whether semi-persistent resource reservation is enabled / disabled in the resource pool.

[0204] In the example of resource pool configuration, the WTRU may be (pre)configured whether to perform resource re-evaluation on a randomly selected resource in the resource pool. The WTRU may accordingly determine whether to perform resource (re)evaluation on the selected resource. In the example of QoS of a TB, if the QoS of the TB is greater than a threshold, the WTRU may determine to perform resource (re)evaluation on the randomly selected resource. Otherwise, the WTRU may determine not to perform resource (re)evaluation. The threshold may be (pre)configured per resource pool. In the example of timing between resource selection time and the first selected resource, if the time gap between resource selection and the first selected resource is greater than a threshold, the WTRU may determine to perform resource (re)evaluation on the randomly selected resource. Otherwise, the WTRU may not perform resource (re)evaluation on the randomly selected resource. The threshold may be (pre)configured per resource pool. The threshold may be configured according to the QoS of the TB. In the example of DRX state of the WTRU, if the QoS of the TB is greater than a threshold, the WTRU may determine to perform resource (re)evaluation on the randomly selected resource. Otherwise, the WTRU may determine not to perform resource (re)evaluation. The threshold may be (pre)configured per resource pool. In the example of whether semi-persistent resource reservation is enabled / disabled in a resource pool, the WTRU may determine whether to perform resource (re)evaluation on a randomly selected resource based on whether semi-persistence is enabled / disabled. For example, if semi-persistent resource reservation is disabled, the WTRU may perform resource (re)evaluation on a randomly selected resource. Otherwise, the WTRU may not perform resource (re)evaluation on a randomly selected resource.

[0205] In an example, the WTRU may determine a listening window for resource re-evaluation after random selection. The WTRU may determine a listening window for resource (re)evaluation of a randomly selected resource. In an example, the listening window may start from the time the WTRU performs resource selection and it may end T3 time slots before the first randomly selected resource. T3 may be fixed based on the processing capability of the WTRU. In another example, the WTRU may be (pre-)configured with a minimum listening window for resource (re)evaluation of a randomly selected resource. The WTRU may start listening when resource selection is triggered and stop listening when the minimum listening window is reached. The WTRU may start listening T0 time slots before the resource selection is triggered. When the minimum required listening window and / or T3 time slots before the first randomly selected resource are reached, the WTRU may stop listening for resource (re)selection.

[0206] In an example, the mechanism may support unicast / multicast. In an example, the WTRU may determine resources for HARQ feedback. The WTRU may be configured with a set of HARQ feedback resources for one resource selection mode, power saving mode, and / or WTRU type and another set of HARQ feedback resources for another resource selection mode, power saving mode, and / or WTRU type. The resource selection mode, power saving mode, and / or WTRU type may be indicated in the SCI. The receiving WTRU (the WTRU receiving the SCI) may then determine which HARQ feedback resource to use based on the resource selection mode, power saving mode, and / or WTRU type (the WTRU transmitting the SCI) indicated in the SCI. Fig.11 Resource timing of an exemplary time-frequency resource 1100 is shown for a physical sidelink feedback channel (PSFCH) resource set for a power saving WTRU 1101 (eg, a PUE) and a resource set for a non-power saving WTRU 1102 (eg, a VUE). Fig.11 In the example of , a WTRU may be configured with two HARQ resource sets: a first resource set that occurs every 2 time slots may be used by a non-power saving WTRU 1102 (e.g., a VUE), while a second resource set that occurs every 6 time slots may be used by a power saving WTRU 1101 (e.g., a PUE). This approach may be beneficial in order to save the limited processing power of a power saving WTRU (e.g., a PUE).

[0207] In an example, the WTRU may determine whether to transmit HARQ feedback for PSCCH / PSSCH. The WTRU may determine whether to transmit HARQ feedback to the Tx WTRU after each PSCCH / PSSCH reception based on one or more factors. An exemplary determining factor may be the number of times a TB is transmitted. For example, the WTRU may feedback HARQ after transmitting a certain number of TBs. For example, the WTRU may transmit (report) HARQ feedback after a maximum of X TB transmissions. The value of X may be (pre) configured by resource pool based on the QoS (e.g., priority) of the TB. An exemplary factor may be resource reservation information in the SCI. For example, if the SCI reserves less than N resources for the same TB, the WTRU may report HARQ feedback after one PSCCH / PSSCH transmission. If the SCI reserves at least N resources for the same TB, the WTRU may not report HARQ feedback. An exemplary factor may be the QoS of the TB. For example, the WTRU may determine whether to transmit HARQ feedback for PSCCH / PSSCH based on the QoS of the TB. For example, if the priority of the TB is greater than a threshold, the WTRU may transmit (report) HARQ feedback, and if the priority of the TB is less than a threshold, the HARQ feedback may not be reported. An exemplary factor may be the CBR of the resource pool. An exemplary factor may be the resource selection mode for the TB transmission resources. For example, if the Tx WTRU performs random resource selection, the WTRU may report HARQ feedback for PSCCH / PSSCH transmission; otherwise, the WTRU may not perform HARQ feedback. In contrast, if the Tx WTRU performs listening-based resource allocation, the receiving WTRU may perform HARQ feedback; otherwise, the WTRU may not perform HARQ feedback.

[0208] In an example, the WTRU may adjust the set of listening resources based on HARQ feedback and / or the average number of transmissions per TB. In one method, the WTRU may adjust the set of listening resources based on the HARQ feedback status of the TB. For example, if the WTRU receives more than X NACK feedbacks for a TB, the WTRU may increase the number of resources used for listening. If the WTRU receives less than Y NACK feedbacks for a TB, the WTRU may decrease the number of listening resources. The values ​​of X and Y may be configured per resource pool per priority.

[0209] In an example, the WTRU may adjust the set of listening resources based on the average number of transmissions per TB per priority level. In one approach, the WTRU may adjust the set of listening resources based on the average number of transmissions per TB. For example, if the average number of transmissions per TB is greater than a threshold, the WTRU may increase the number of listening resources, and if the average number of transmissions per TB is less than a threshold, it may decrease the number of listening resources. The threshold may be configurable per resource pool per priority level.

[0210] In an example, the WTRU may perform any one or more of the following: determine whether to use listening-based or random resource selection in a resource pool; indicate a resource selection mode and / or a power saving mode in a message; determine a resource selection window for a TB; determine resource selection for HARQ feedback; determine whether to transmit HARW feedback for PSCCH / PSSCH; adjust a set of listening resources based on HARQ feedback and / or an average number of transmissions per TB; and / or adjust a set of listening resources based on an average number of transmissions for TBs per priority level.

[0211] An example method for congestion control is described herein. A WTRU may determine TB transmission behavior for congestion control. In an example, the WTRU may determine any one or more of the following TB transmission parameters: number of (re)transmissions of a TB; number of subchannels to use for each transmission; transmit power; MCS in a TB; and / or which MCS table to use.

[0212] The WTRU may use any one or more of the following criteria to determine the transmission parameters of the TB. In an example, a resource selection type (e.g., random-based, full-sounding-based, and partial-sounding-based) may be used. For example, the WTRU may be (pre-)configured to use multiple resource selection types for the TB. The WTRU may be (pre-)configured with multiple sets of ranges (e.g., maximum values ​​and / or minimum values) of transmission parameters for the TB, where one set may be (pre-)configured for one (or more) resource selection types (e.g., random-based, full-sounding-based, and partial-sounding-based), and another set may be (pre-)configured for another resource selection type. The WTRU may then determine which set of ranges to use based on the resource selection type of the TB.

[0213] For example, the WTRU may be (pre)configured with two maximum (re)transmission times per TB, one threshold may be (pre)configured for random based resource allocation and another threshold may be (pre)configured for listening based resource allocation. The WTRU may then determine the threshold to use based on the resource selection type of the TB.

[0214] In an example, the number of candidate time slots and / or the number of candidate resources in the resource selection window may be used. For example, the WTRU may determine the maximum number of (re)transmissions of the TB based on the maximum number of candidate time slots in the resource selection window. In another example, the number of selectable resources in the resource selection window may be used. In another example, the HARQ type of the TB may be used (e.g., HARQ-enabled and HARQ-disabled TBs).

[0215] In another example, the DRX state of the WTRU may be used. For example, the DRX state of the WTRU may include any one or more of the following criteria: whether DRX is configured; and / or whether the WTRU is in an on duration or an off duration. In another example, whether the resource (re)evaluation of selected resources is enabled / disabled may be used. In another example, whether the resource (re)evaluation of reserved resources is enabled / disabled may be used. In other examples, the broadcast type of the TB (e.g., broadcast, unicast, or multicast) and / or the power saving mode of the WTRU may be used. In another example, the QoS of the TB, the CBR of the resource pool, and / or the CR of the WTRU may be used. For example, the WTRU may determine which MCS table to use based on the QoS of the TB, the CBR of the resource pool, and / or the CR of the WTRU.

[0216] Although the features and elements are described above in specific combinations, it will be understood by those skilled in the art that each feature or element may be used alone or in any combination with other features and elements. In addition, the methods described herein may be implemented in a computer program, software, or firmware incorporated in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted via a wired or wireless connection) and 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, cache memory, semiconductor memory devices, magnetic media (such as built-in hard disks and removable disks), magneto-optical media, and optical media (such as CD-ROM disks and digital versatile disks (DVDs)). A processor associated with software may be used to implement a radio frequency transceiver for a WTRU, UE, terminal, base station, RNC, or any host computer.

Claims

1. A first wireless transmit / receive unit (WTRU), comprising: Transceiver; and processor, wherein the transceiver and the processor are configured to: receiving side link control information (SCI) from a second WTRU, wherein the SCI comprises first information indicating, for each resource in a resource pool, whether the resource is reserved by the second WTRU, and second information indicating whether the second WTRU is a power saving WTRU or a non-power saving WTRU; measuring a reference signal received power (RSRP) of a signal transmitted by the second WTRU; To perform resource selection, follow these steps: For each resource in the resource pool: adding the resource to a set of available resources if the first information indicates that the resource is not reserved by the second WTRU; In a case where the first information indicates that the resource is reserved by the second WTRU: setting a selected RSRP threshold or increment to a first set of RSRP thresholds or increments for determining availability of resources if the second information indicates that the second WTRU is a power saving WTRU; setting the selected RSRP threshold or increment to a second set of RSRP thresholds or increments for determining availability of resources if the second information indicates that the second WTRU is a non-power saving WTRU; In a case where the measured RSRP is less than the selected RSRP threshold, adding the resource to the set of available resources; as well as A resource is selected from the set of available resources for use in the transmission.

2. The first WTRU of claim 1, wherein the transceiver and the processor are configured to trigger the resource selection when the first WTRU has data to transmit to the second WTRU.

3. The first WTRU of claim 1 , wherein each of the resources in the resource pool is a time-frequency resource.

4. The first WTRU of claim 1 , wherein the first set of RSRP thresholds or increments and the second set of RSRP thresholds or increments are pre-configured.

5. The first WTRU of claim 1, wherein the transceiver and the processor are configured to select the resource from the set of available resources for transmission during a resource selection window.

6. The first WTRU of claim 1 , wherein the transceiver and the processor are configured to receive the SCI during a listening window and measure the RSRP of the signal.

7. The first WTRU of claim 6, wherein the listening window is one of a long-term partial listening window or a short-term partial listening window.

8. The first WTRU of claim 1, wherein the first WTRU is configured as one of a power-saving WTRU or a non-power-saving WTRU.

9. The first WTRU of claim 1, configured as one of a pedestrian user equipment (PUE) or a vehicle user equipment (VUE).

10. A first WTRU according to claim 1, wherein the power saving WTRU operates in a first power saving mode and the non-power saving WTRU operates in a second power saving mode, wherein operation according to the first power saving mode uses less power than operation according to the second power saving mode.

11. A method performed by a first wireless transmit / receive unit (WTRU), the method comprising: receiving side link control information (SCI) from a second WTRU, wherein the SCI comprises first information indicating, for each resource in a resource pool, whether the resource is reserved by the second WTRU, and second information indicating whether the second WTRU is a power saving WTRU or a non-power saving WTRU; measuring a reference signal received power (RSRP) of a signal transmitted by the second WTRU; To perform resource selection, follow these steps: For each resource in the resource pool: adding the resource to a set of available resources if the first information indicates that the resource is not reserved by the second WTRU; In a case where the first information indicates that the resource is reserved by the second WTRU: setting a selected RSRP threshold or increment to a first set of RSRP thresholds or increments for determining availability of resources if the second information indicates that the second WTRU is a power saving WTRU; setting the selected RSRP threshold or increment to a second set of RSRP thresholds or increments for determining availability of resources if the second information indicates that the second WTRU is a non-power saving WTRU; In a case where the measured RSRP is less than the selected RSRP threshold, adding the resource to the set of available resources; as well as A resource is selected from the set of available resources for use in the transmission.

12. The method of claim 11, further comprising triggering the resource selection when the first WTRU has data to transmit to the second WTRU.

13. The method of claim 11, wherein each of the resources in the resource pool is a time-frequency resource.

14. The method of claim 11, wherein the first set of RSRP thresholds or increments and the second set of RSRP thresholds or increments are preconfigured.

15. The method of claim 11, wherein the selecting the resource from the set of available resources for use in transmission occurs during a resource selection window.

16. The method of claim 11, wherein the receiving the SCI and the measuring signal's RSRP occurs during a listening window.

17. The method of claim 16, wherein the listening window is one of a long-term partial listening window or a short-term partial listening window.

18. The method of claim 11, wherein the first WTRU is configured as one of a power-saving WTRU or a non-power-saving WTRU.

19. The method of claim 11, wherein the first WTRU is configured as one of a pedestrian user equipment (PUE) or a vehicle user equipment (VUE).

20. The method of claim 11, wherein the power saving WTRU operates in a first power saving mode and the non-power saving WTRU operates in a second power saving mode, wherein operation according to the first power saving mode uses less power than operation according to the second power saving mode.

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