NR V2X method for data transmission in wireless systems

Abstract

A method and apparatus for selecting resources for transmission may be performed by a WTRU. The method may include determining a priority of a data packet and determining a CBR of a resource pool. The WTRU may set a backoff counter to an initial backoff value based on at least one of the priority of the packet or the CBR. CCA may be performed in multiple resource time slots to determine whether the resource time slot is available. The backoff counter may reduce the number of available resources in each time slot. When the backoff counter reaches a threshold that may be set to zero, the resource may be randomly selected for transmission. The WTRU may then transmit data to another WTRU on the randomly selected resource.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Application No. 62 / 715,659, filed on August 7, 2018, U.S. Provisional Application No. 62 / 736,287, filed on September 25, 2018, U.S. Provisional Application No. 62 / 752,787, filed on October 30, 2018, U.S. Provisional Application No. 62 / 789,861, filed on January 8, 2019, and U.S. Provisional Application No. 62 / 840,793, filed on April 30, 2019, the contents of each of which are incorporated herein by reference. Summary of the invention

[0003] A method and wireless transmit / receive unit (WTRU) for selecting resources for transmission. The method may include determining a priority of a data packet and determining a channel busy ratio (CBR) of a resource pool, the WTRU may set a backoff counter to an initial backoff value based on at least one of the priority of the packet or the CBR. A clear channel assessment (CCA) may be performed in multiple resource time slots to determine whether the resource time slot is available. The backoff counter may reduce the number of available resources in each time slot. When the backoff counter reaches a threshold that may be set to zero, the resource may be randomly selected for transmission. The WTRU may then transmit data to another WTRU on the randomly selected resource. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Furthermore, like reference numerals in the accompanying drawings denote like elements, and wherein:

[0005] Figure 1A is a system diagram illustrating an exemplary communication system in which one or more disclosed embodiments may be implemented;

[0006] Figure 1B is a diagram showing the Figure 1A A system diagram of an exemplary wireless transmit / receive unit (WTRU) for use within a communication system as shown in;

[0007] Figure 1C is a diagram showing the Figure 1A A system diagram of an exemplary radio access network (RAN) and an exemplary core network (CN) used within the communication system shown in;

[0008] Figure 1D is a diagram showing the Figure 1A A system diagram of another exemplary RAN and another exemplary CN used in the communication system shown in;

[0009] Figure 2 is a diagram illustrating channelization of time and frequency resources;

[0010] Figure 3 is a diagram illustrating example options for a clear channel assessment (CCA) configuration;

[0011] Figure 4 is an example of a resource selection process;

[0012] Figure 5 is a diagram showing a pool configuration of a side link control information (SCI) notification (SCI_Notification);

[0013] Figure 6 is a timing diagram illustrating channel access of one or more SCI_Notification messages having one or more different priorities;

[0014] Figure 7 is a diagram showing a WTRU randomly selecting four time-frequency resources to perform CCA for transmission of two SCI_Notification messages;

[0015] Figure 8 is a diagram showing options for SCI_Notification for notifying future PSSCH and / or Physical Sidelink Control Channel (PSCCH) transmission(s); and

[0016] Fig. 9 is a diagram illustrating calculation of a sidelink received signal strength indicator (S-RSSI) for a candidate resource;

[0017] Fig.10 is a timing diagram showing an SCI indication regarding one or more consecutive transmissions following the indication;

[0018] Fig.11 is a diagram illustrating a method in which a WTRU uses a first transmitted SCI_Notification to reserve resources for subsequent retransmissions;

[0019] Fig.12 This is a diagram of a sample pattern design;

[0020] Fig.13 is a diagram illustrating a WTRU determining availability of a pattern based on decoding an SCI or SCI_Notification;

[0021] Fig.14 is a diagram showing a WTRU randomly selecting a pattern window for multiple transmissions of a TB;

[0022] Fig.15 is a flow chart illustrating resource selection based on group priority;

[0023] Fig.16 is a timing diagram illustrating a transmission process using a backoff counter; and

[0024] Fig.17 is a flow chart illustrating an example method by which a WTRU selects resources for transmission.

[0025] Example Network for Implementation of Embodiments

[0026] Figure 1A 1 is a diagram showing an exemplary communication system 100 in which the disclosed embodiments may be implemented. The communication system 100 may be a multiple access system that provides content such as voice, data, video, messaging, broadcast, etc. to multiple wireless users. The communication system 100 may enable multiple wireless users to access such content by sharing system resources including wireless bandwidth. For example, the communication system 100 may use one or more channel access methods such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single carrier FDMA (SC-FDMA), zero tail unique word discrete Fourier transform spread OFDM (ZT-UW-DFT-S-OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, and filter bank multi-carrier (FBMC), etc.

[0027] like Figure 1AAs shown, the communication system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a radio access network (RAN) 104, a CN 106, a public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, although it should be appreciated that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network components. Each WTRU 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. For example, any of the WTRUs 102a, 102b, 102c, 102d may be referred to as a “station (STA)”, which may be configured to transmit and / or receive wireless signals, and may include a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular phone, a personal digital assistant (PDA), a smart phone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watch or other wearable device, a head-mounted display (HMD), a vehicle, a drone, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices working in an industrial and / or automated process chain environment), consumer electronic devices, and devices working on a commercial and / or industrial wireless network, etc. Any of the WTRUs 102a, 102b, 102c, 102d may be interchangeably referred to as a UE.

[0028] The communication system 100 may also include a base station 114a and / or a base station 114b. Each base station 114a, 114b may be any type of device configured to facilitate access to one or more communication networks (e.g., CN 106, Internet 110, and / or other networks 112) by wirelessly interfacing with at least one of the WTRUs 102a, 102b, 102c, 102d. For example, the base stations 114a, 114b may be base transceiver stations (BTS), node Bs, e-node Bs (eNBs), home node Bs, home e-node Bs, next generation node Bs (such as g-node Bs (gNBs)), new radio (NR) node Bs, site controllers, access points (APs), and wireless routers, among others. Although each base station 114a, 114b is depicted as a single component, it should be understood that the base stations 114a, 114b may include any number of interconnected base stations and / or network components.

[0029] The base station 114a may be part of the RAN 104, and the RAN may also include other base stations and / or network components (not shown), such as a base station controller (BSC), a radio network controller (RNC), and relay nodes, 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 called cells (not shown). These frequencies may be in a licensed spectrum, an unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide wireless service coverage for a specific geographic area that is relatively fixed or may change over time. A cell may be further divided into cell sectors. For example, a cell associated with the base station 114a may be divided into three sectors. Thus, in one embodiment, the base station 114a may include three transceivers, that is, each transceiver corresponds to a sector of the cell. In an embodiment, the base station 114a may use multiple-input multiple-output (MIMO) technology and may use multiple transceivers for each sector of the cell. For example, by using beamforming, signals may be transmitted and / or received in a desired spatial direction.

[0030] 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).

[0031] More specifically, as described herein, the communication system 100 may be a multiple access system and may utilize one or more channel access schemes such as CDMA, TDMA, FDMA, OFDMA, and SC-FDMA, among others. For example, the base station 114a in the RAN 104 and the WTRUs 102a, 102b, 102c may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may utilize 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).

[0032] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 116 using Long Term Evolution (LTE) and / or Advanced LTE (LTE-A) and / or Advanced LTE Pro (LTE-APro).

[0033] In an 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.

[0034] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may jointly implement LTE radio access and NR radio access (e.g., using dual connectivity (DC) principles). Thus, the air interface used by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions sent to / from multiple types of base stations (e.g., eNBs and gNBs).

[0035] 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), Enhanced Data Rates for GSM Evolution (EDGE), and GSM EDGE (GERAN), among others.

[0036] Figure 1AThe base station 114b in the example may be a wireless router, a Home NodeB, a Home eNodeB, or an access point, and may use any appropriate RAT to facilitate wireless connectivity in a local area, such as a business location, a residence, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a road, and the like. In one embodiment, the base station 114b and the WTRUs 102c, 102d may establish a wireless local area network (WLAN) by implementing a radio technology such as IEEE 802.11. In an embodiment, the base station 114b and the WTRUs 102c, 102d may establish a wireless personal area network (WPAN) by implementing a radio technology such as IEEE 802.15. In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may establish a picocell or a femtocell by using a cellular-based RAT (e.g., WCDMA, CDMA 2000, GSM, LTE, LTE-A, LTE-A Pro, NR, and the like). Figure 1A As shown, the base station 114b may be directly connected to the Internet 110. Thus, the base station 114b does not need to access the Internet 110 via the CN 106.

[0037] 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 WTRUs 102a, 102b, 102c, 102d. The data may have different quality of service (QoS) requirements, such as different throughput requirements, latency requirements, fault tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 may provide call control, billing services, mobile location-based services, prepaid calls, Internet connectivity, video distribution, etc., and / or may perform advanced security functions such as user authentication. Although in Figure 1A Although not shown, it will be appreciated that the RAN 104 and / or CN 106 may be in direct or indirect communication with other RANs that employ the same RAT or a different RAT as the RAN 104. For example, in addition to being connected to the RAN 104 employing NR radio technology, the CN 106 may also be in communication with another RAN (not shown) employing GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0038] 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 network 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 other networks 112 may include another CN connected to one or more RANs, where the one or more RANs may use the same RAT or a different RAT as the RAN 104.

[0039] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communication system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks over different wireless links). Figure 1A The illustrated WTRU 102c may be configured to communicate with the base station 114a, which may employ a cellular-based radio technology, and with the base station 114b, which may employ an IEEE 802 radio technology.

[0040] Figure 1B is a system diagram showing an example WTRU 102. Figure 1B As shown, the WTRU 102 may include a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keyboard 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 should be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0041] 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, and the like. The processor 118 may perform signal coding, data processing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. Although Figure 1B The processor 118 and the transceiver 120 are depicted as separate components, however it should be appreciated that the processor 118 and the transceiver 120 may also be integrated into one electronic component or chip.

[0042] The transmit / receive component 122 may be configured to transmit or receive signals to or from a base station (e.g., base station 114a) via the air interface 116. For example, in one embodiment, the transmit / receive component 122 may be an antenna configured to transmit and / or receive RF signals. As an example, in an embodiment, the transmit / receive component 122 may be an emitter / detector configured to transmit and / or receive IR, UV, or visible light signals. In an embodiment, the transmit / receive component 122 may be configured to transmit and / or receive RF and light signals. It should be appreciated that the transmit / receive component 122 may be configured to transmit and / or receive any combination of wireless signals.

[0043] Although in Figure 1B 102 as a single component, but the WTRU 102 may include any number of transmit / receive components 122. More specifically, the WTRU 102 may employ MIMO technology. Thus, in an embodiment, the WTRU 102 may include two or more transmit / receive components 122 (e.g., multiple antennas) for transmitting and receiving radio signals over the air interface 116.

[0044] The transceiver 120 may be configured to modulate signals to be transmitted by the transmit / receive component 122 and to demodulate signals received by the transmit / receive component 122. As described herein, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers that allow the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11.

[0045] The processor 118 of the WTRU 102 may be coupled to the speaker / microphone 124, the keyboard 126, and / or the display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light emitting diode (OLED) display unit), and may receive user input data from these components. The processor 118 may also output user data to the speaker / microphone 124, the keyboard 126, and / or the display / touchpad 128. In addition, the processor 118 may access information from and store information in any suitable memory, such as 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 memories that are not physically located in the WTRU 102, such as, for example, a server or a home computer (not shown).

[0046] The processor 118 may receive power from the power source 134, and may be configured to distribute and / or control power for use by other components in the WTRU 102. The power source 134 may be any suitable device for powering the WTRU 102. For example, the power source 134 may include one or more dry cell batteries (e.g., nickel-cadmium (Ni-Cd), nickel-zinc (Ni-Zn), nickel-metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, and the like.

[0047] The processor 118 may also be coupled to the GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) related to the current location of the WTRU 102. In addition to or in lieu of the information from the GPS chipset 136, the WTRU 102 may receive location information from a base station (e.g., base stations 114a, 114b) via the air interface 116 and / or determine its location based on the timing of signals received from two or more nearby base stations. It should be appreciated that the WTRU 102 may acquire location information via any suitable positioning method while remaining consistent with an embodiment.

[0048] The processor 118 may also be coupled to other peripheral devices 138, which may include one or more software and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, the peripheral devices 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos and / or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, Modules, FM radio units, digital music players, media players, video game console modules, Internet browsers, virtual reality and / or augmented reality (VR / AR) devices, and activity trackers, etc. The peripherals 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, and a humidity sensor, etc.

[0049] The WTRU 102 may include a full-duplex radio in which reception or transmission of some or all signals (e.g., associated with specific subframes for UL (e.g., for transmission) and DL (e.g., for reception)) may be concurrent and / or simultaneous for the radio. A full-duplex radio may include an interference management unit that reduces and / or substantially eliminates self-interference by means of hardware (e.g., chokes) or by signal processing by a processor (e.g., a separate processor (not shown) or by the processor 118). In an embodiment, the WTRU 102 may include a half-duplex radio that transmits and receives some or all signals (e.g., associated with specific subframes for UL (e.g., for transmission) or DL ​​(e.g., for reception)).

[0050] Figure 1C 1 is a system diagram showing the RAN 104 and the CN 106 in accordance with an embodiment. As described herein, the RAN 104 may communicate with the WTRUs 102a, 102b, 102c using an E-UTRA radio technology over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0051] The RAN 104 may include eNode-Bs 160a, 160b, 160c, however it will be appreciated that the RAN 104 may include any number of eNode-Bs while remaining consistent with an embodiment. Each of the eNode-Bs 160a, 160b, 160c may include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the eNode-Bs 160a, 160b, 160c may implement MIMO technology. Thus, for example, the eNode-B 160a may use multiple antennas to transmit wireless signals to, and / or receive wireless signals from, the WTRU 102a.

[0052] Each eNodeB 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, user scheduling in UL and / or DL, etc. Figure 1C As shown, the eNode-Bs 160a, 160b, 160c may communicate with each other via an X2 interface.

[0053] 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. Although the aforementioned components are described as being part of the CN 106, it should be appreciated that any of these components may be owned and / or operated by an entity other than the CN operator.

[0054] The MME 162 may be connected to each of the eNode-Bs 160a, 160b, 160c in the RAN 104 via an S1 interface and may serve as a control node. For example, the MME 142 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, performing bearer activation / deactivation processing, and selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c. The MME 162 may also 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.

[0055] The SGW 164 may be connected to each of the eNode-Bs 160a, 160b, 160c in the RAN 104 via an S1 interface. The SGW 164 may generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 may also perform other functions, such as anchoring the user plane during inter-eNB handovers, triggering paging processing when DL data is available for the WTRUs 102a, 102b, 102c, and managing and storing the contexts of the WTRUs 102a, 102b, 102c, and the like.

[0056] 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.

[0057] 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 be in communication with an IP gateway, such as an IP Multimedia Subsystem (IMS) server, and the IP gateway may serve as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks that are owned and / or operated by other service providers.

[0058] Although in Figures 1A-1D Although the WTRU is described as a wireless terminal, it should be appreciated that in certain typical embodiments, such a terminal may use a (eg, temporary or permanent) wired communication interface with a communication network.

[0059] In a typical embodiment, the other network 112 may be a WLAN.

[0060] A WLAN using an infrastructure basic service set (BSS) mode may have an access point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP may access or be connected to a distributed system (DS) or other types of wired / wireless networks that send services into and / or out of the BSS. Services originating from outside the BSS and destined for the STA may be reached by the AP and delivered to the STA. Services originating from the STA and destined for a destination outside the BSS may be sent to the AP for delivery to the corresponding destination. Services between STAs within the BSS may be sent through the AP, for example, the source STA may send services to the AP and the AP may deliver services to the destination STA. Services between STAs within the BSS may be considered and / or referred to as end-to-end services. The end-to-end services may be sent using a direct link establishment (DLS) between the source and destination STAs (e.g., directly therebetween). In certain typical embodiments, the DLS may use 802.11e DLS or 802.11z channelized 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. Here, the IBSS communication mode may also be sometimes referred to as an "ad hoc" communication mode.

[0061] When using the 802.11ac infrastructure mode of operation or a similar mode of operation, the AP may transmit a beacon on a fixed channel (e.g., a primary channel). The primary channel may have a fixed width (e.g., a bandwidth of 20 MHz) or a dynamically set width. The primary channel may be a working channel of the BSS and may be used by STAs to establish a connection with the AP. In certain typical embodiments, carrier sense multiple access (CSMA / CA) with collision avoidance (e.g., in an 802.11 system) may be implemented. For CSMA / CA, STAs (e.g., each STA) including the AP may sense the primary channel. If a particular STA senses / detects and / or determines that the primary channel is busy, the particular STA may back off. In a specified BSS, one STA (e.g., only one station) may transmit at any given time.

[0062] A high throughput (HT) STA may communicate using a 40 MHz wide channel (eg, by combining a 20 MHz wide primary channel with a 20 MHz wide adjacent or non-adjacent channel to form a 40 MHz wide channel).

[0063] Very high throughput (VHT) STA can support channels with widths of 20MHz, 40MHz, 80MHz and / or 160MHz. 40MHz and / or 80MHz channels can be formed by combining continuous 20MHz channels. A 160MHz channel can be formed by combining 8 continuous 20MHz channels or by combining two discontinuous 80MHz channels (this combination can be referred to as an 80+80 configuration). For the 80+80 configuration, after channel coding, the data can be transmitted and passed through a segment parser, which can separate the data into two streams. Inverse fast Fourier transform (IFFT) processing and time domain processing can be performed separately on each stream. The stream can be mapped on two 80MHz channels, and the data can be transmitted by the STA performing the transmission. At the receiver of the STA performing the reception, the above-mentioned operation for the 80+80 configuration can be opposite, and the combined data can be sent to the medium access control (MAC).

[0064] 802.11af and 802.11ah support working modes below 1 GHz. Compared with 802.11n and 802.11ac, the channel working bandwidth and carrier used in 802.11af and 802.11ah are reduced. 802.11af supports 5MHz, 10MHz and 20MHz bandwidths in the TV White Space (TVWS) spectrum, and 802.11ah supports 1MHz, 2MHz, 4MHz, 8MHz and 16MHz bandwidths using non-TVWS spectrum. According to certain typical embodiments, 802.11ah can support meter type control / machine type communication (MTC) (e.g., MTC devices in macro coverage areas). MTC can have certain capabilities, such as limited capabilities including support (e.g., only support) certain and / or limited bandwidths. MTC devices can include a battery, and the battery life of the battery is higher than a threshold (e.g., for maintaining a very long battery life).

[0065] For WLAN systems that can support multiple channels and channel bandwidths (e.g., 802.11n, 802.11ac, 802.11af, and 802.11ah), the WLAN system includes a channel that can be designated as a primary channel. The bandwidth of the primary channel can be equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel can be set and / or limited by a certain STA, where the STA originates from all STAs operating in the BSS that supports the minimum bandwidth operating mode. In the example of 802.11ah, even if the AP and other STAs in the BSS support 2MHz, 4MHz, 8MHz, 16MHz and / or other channel bandwidth operating modes, for STAs (e.g., MTC-type devices) that support (e.g., only support) 1MHz mode, the width of the primary channel can be 1MHz. Carrier sensing and / or network allocation vector (NAV) settings can depend on the state of the primary channel. If the primary channel is busy (eg, because a STA (which only supports 1 MHz operating mode) is transmitting to the AP), then all available frequency bands may be considered busy even if most of the available frequency bands remain idle.

[0066] In the United States, the available frequency band for 802.11ah is 902MHz to 928MHz. In South Korea, the available frequency band is 917.5MHz to 923.5MHz. In Japan, the available frequency band is 916.5MHz to 927.5MHz. Depending on the country code, the total bandwidth available for 802.11ah is 6MHz to 26MHz.

[0067] Figure 1D1 is a system diagram showing the RAN 104 and the CN 106 according to an embodiment. As described above, the RAN 104 may communicate with the WTRUs 102a, 102b, 102c using NR radio technology over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0068] 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. Each of the gNBs 180a, 180b, 180c may include one or more transceivers to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, the gNBs 180a, 180b may use beamforming processing to transmit and / or receive signals to and / or from the gNBs 180a, 180b, 180c. Thus, for example, the gNB 180a may use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a. In an embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation technology. 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 an unlicensed spectrum while the remaining component carriers may be on a licensed spectrum. In an embodiment, the gNBs 180a, 180b, 180c may implement coordinated multi-point (CoMP) technology. For example, the WTRU 102a may receive coordinated transmissions from the gNB 180a and gNB 180b (and / or gNB 180c).

[0069] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with a scalable numerology. For example, the OFDM symbol spacing and / or OFDM subcarrier spacing may be different for different transmissions, different cells, and / or different portions of the radio transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using subframes or transmission time intervals (TTIs) of different or scalable lengths (e.g., containing different numbers of OFDM symbols and / or varying absolute time lengths).

[0070] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c without accessing other RANs (e.g., the eNodeBs 160a, 160b, 160c). In a standalone configuration, the WTRUs 102a, 102b, 102c may use one or more of the gNBs 180a, 180b, 180c as mobility anchors. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration, the WTRU 102a, 102b, 102c may communicate / connect to the gNB 180a, 180b, 180c while communicating / connecting to another RAN (e.g., the eNode-B 160a, 160b, 160c). For example, the WTRU 102a, 102b, 102c may communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c in a substantially simultaneous manner by implementing the DC principle. In a non-standalone configuration, the eNode-B 160a, 160b, 160c may act as a mobility anchor for the WTRU 102a, 102b, 102c, and the gNB 180a, 180b, 180c may provide additional coverage and / or throughput to serve the WTRU 102a, 102b, 102c.

[0071] Each gNB 180a, 180b, 180c may be associated with a specific cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, user scheduling in UL and / or DL, support network slicing, DC, implement interworking between NR and E-UTRA, route user plane data to user plane functions (UPFs) 184a, 184b, and route control plane information to access and mobility management functions (AMFs) 182a, 182b, etc. Figure 1D As shown, gNB180a, 180b, and 180c can communicate with each other through the X2 interface.

[0072] Figure 1DThe CN 106 shown may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one session management function (SMF) 183a, 183b, and may include a data network (DN) 185a, 185b. Although the foregoing components are described as part of the CN 106, it should be understood that any of these components may be owned and / or operated by entities other than the CN operator.

[0073] The AMF 182a, 182b may be connected to one or more gNBs 180a, 180b, 180c in the RAN 104 via an N2 interface and may act as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRU 102a, 102b, 102c, supporting network slicing (e.g., handling different protocol data unit (PDU) sessions with different requirements), selecting a specific SMF 183a, 183b, managing registration areas, terminating non-access stratum (NAS) signaling, and mobility management, etc. The AMF 182a, 1823b may use network slicing processing to customize the CN support provided to the WTRU 102a, 102b, 102c based on the service type 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 massive 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) using other radio technologies, such as LTE, LTE-A, LTE-APro, and / or non-3GPP access technologies such as WiFi.

[0074] 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 may configure service routing through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions, such as managing and allocating UE IP addresses, managing PDU sessions, controlling policy implementation and QoS, and providing DL data notifications, etc. The PDU session type may be IP-based, non-IP-based, Ethernet-based, etc.

[0075] The UPF 184a, 184b can be connected to one or more gNBs 180a, 180b, 180c in the RAN 104 via the N3 interface, which can provide the WTRUs 102a, 102b, 102c with access to packet-switched networks (e.g., the Internet 110) to facilitate communication between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPF 184, 184b can perform other functions such as routing and forwarding packets, implementing user plane policies, supporting multi-host PDU sessions, processing user plane QoS, buffering DL packets, and providing mobility anchor processing, etc.

[0076] 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 acts 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 one embodiment, the WTRUs 102a, 102b, 102c may be connected to the local DN 185a, 185b via the N3 interface connected to the UPF 184a, 184b and the N6 interface between the UPF 184a, 184b and the DN 185a, 185b and through the UPF 184a, 184b.

[0077] In view of Figures 1A-1D and about Figures 1A-1D , 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): WTRU 102a-d, base station 114a-b, eNodeB 160a-c, MME 162, SGW 164, PGW 166, gNB 180a-c, AMF 182a-b, UPF 184a-b, SMF 183a-b, DN 185a-b, and / or any other device(s) described herein. These simulation devices may be one or more devices configured to simulate one or more or all of the functions herein. For example, these simulation devices may be used to test other devices and / or simulate network and / or WTRU functions.

[0078] The simulation device can be designed to implement one or more tests about other devices in a laboratory environment and / or an operator network environment. For example, the one or more simulation devices can perform one or more or all functions while being implemented and / or deployed as part of a wired and / or wireless communication network in whole or in part to test other devices inside the communication network. The one or more simulation devices can perform one or more or all functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network. The simulation device can be directly coupled to other devices to perform the test, and / or can use over-the-air wireless communication to perform the test.

[0079] The one or more simulation devices can perform one or more functions, including all functions, while not being implemented / deployed as part of a wired and / or wireless communication network. For example, the simulation device can be used in a test lab and / or a test scenario of a wired and / or wireless communication network that is not deployed (e.g., tested) to implement tests on one or more components. The one or more simulation devices can be test devices. The simulation device can transmit and / or receive data using direct RF coupling and / or wireless communication with the aid of RF circuits (as an example, the circuits can include one or more antennas). DETAILED DESCRIPTION

[0080] The V2X feature of LTE provides support for basic safety services. Generally, there are two types of supported services: periodic services and event-triggered services. According to a service model, periodic and non-periodic services are generated as follows. For periodic services, one 300-byte message is followed by four 190-byte messages. In addition, the arrival interval time between two packets is a multiple of 100ms. For event-triggered services, when an event is triggered after a Poisson process, 6 messages are generated with a period of 100ms. According to the above service model of LTE V2X, generally, both event-triggered services and periodic services can be considered as periodic services.

[0081] Sensing and resource selection for LTE V2X may be performed by the WTRU prior to the transmission of control information or data. In LTE V2X, the Physical Sidelink Control Channel (PSCCH) and the Physical Sidelink Shared Channel (PSSCH) are transmitted in the same subframe. The PSCCH contains Sidelink Control Information (SCI) which provides information about upcoming or simultaneous PSSCH transmissions. By decoding the PSCCH, the receiving WTRU may decode the following information: the frequency and time of forward bookings for the PSSCH; the priority of the PSSCH; the frequency and time of PSSCH retransmissions.

[0082] Typically, a vehicle-type WTRU in LTE V2X performs sensing and resource selection as follows. First, it performs sensing to decode one or more SCIs sent from one or more other WTRUs. Based on the decoding of the SCI(s), the WTRU may have information about the forward reservation PSSCH and the corresponding priority. If the reference signal received power (RSRP) (RSRP_PSSCH) of the WTRU's PSCCH is greater than a threshold, the WTRU may consider the forward reservation PSSCH to be occupied and exclude it from resource selection. The WTRU then arranges the remaining resources in ascending order of received signal strength indicator (RSSI) and may select 20% of the total resources as the final resource selection, as shown in the set SA. Finally, a resource is randomly selected in the SA for transmission.

[0083] Similar to LTE V2X, NR V2X aims to support two types of services, namely, periodic and aperiodic. However, NR aims to support more different types of packet sizes, packet arrival rates, and latency requirements. Specifically, Model 2 aperiodic services support the following attributes: packet size range between 10,000 and 30,000 bytes; average inter-arrival rate of 20 ms; latency requirement of 10 ms. In addition, Mode 3 periodic services have the following attributes: packet size range between 30,000 and 60,000 bytes; average inter-arrival rate of 30 ms; and latency requirement of 30 ms.

[0084] For NR V2X, non-periodic traffic is considered an important traffic model required in the most advanced scenarios. For traffic model 2, the WTRU may need to perform resource selection very frequently, for example, once every 20ms on average. If the WTRU follows the same resource selection process of LTE V2X, resource conflicts will occur very frequently because the probability of multiple WTRUs performing resource selection at the same time will increase.

[0085] In one embodiment, the WTRU may perform resource selection for bursty traffic without increasing the risk of resource contention.

[0086] Resource selection in LTE V2X allocates resources for a single transport block. For Model 2 aperiodic traffic and Model 3 periodic traffic, NR V2X aims to support very large packet sizes, for example, up to 60,000 bytes for periodic traffic and up to 30,000 bytes for aperiodic traffic. Therefore, performing resource selection for one application layer packet may require segmenting the packet and performing multiple resource selections for each transport block associated with the packet. An alternative embodiment is to use a single resource selection process to perform resource selection for multiple TBs simultaneously, for example.

[0087] Figure 2 200 is a diagram showing channelization of time 204 and frequency 202 resources. In one embodiment, the WTRU may perform resource selection for multiple TB transmissions. The WTRU may be configured according to alternative options for channelization. As shown, one or more resource pools may be channelized. In the frequency domain 202, 1 subchannel may consist of N sub PRBs may consist of or may include N sub A subband may be composed of N consecutive PRBs, for example, each subchannel may have 2 PRBs. Each subchannel may be orthogonal in the frequency domain. One subband may consist of or may include N subchannels. Each subband may be overlapping or non-overlapping in frequency, and each subband may or may not have the same number of subchannels. One transmission may occupy one subband in the frequency domain.

[0088] In the time domain 204, the transmission instant can be determined based on the following two factors: the duration of the transmission and whether the transmission is a slot-based transmission or a non-slot-based transmission. For slot-based transmission, one transmission can span N slots. For non-slot-based transmission, one transmission can span N≤14 symbols. The initial transmission can be at the beginning of the slot, at the second half of the slot, or at any symbol of the slot.

[0089] exist Figure 2 In the example shown, three different example subband configurations 206-210 are shown. In the illustration of N subchannel subband 206, each subchannel includes 2 PRBs. Each of the four PRBs corresponds to one of the two channels separated in frequency. For simplicity, a variable number of additional subchannels are not shown. In the example of 2 subchannel subband 208, there are 4 PRBs. In the example of 1 subchannel subband 210, two PRBs are shown.

[0090] The pool indication 212 may be provided as a bitmap that indicates a pool as either "on" via a (1) bit or "off" via a (0) bit. The pool indication may be made via RRC, MAC, or PHY signaling.

[0091] In the example shown, the first two bits 214, 216 are "on" so there is a transmission time instance available for transmission in the time domain. The WTRU may determine, based on the bitmap, whether a transmission instant is available on one or more subbands 206-210. For example, the WTRU may determine that a two-symbol transmission time instance 236 is available on the N-channel subband 206 along the entire subchannel 238 or only along a single or two PRBs (e.g., PRB 240). The WTRU may determine that a two-slot transmission time instance 242 is available on the 2-subchannel subband 208. The WTRU may determine that only 2 symbols 244 are available in the 1-subchannel subband 210. The WTRU may enter a sleep state during the next two time slots based on determining that bits 218, 220 are set to "off".

[0092] The WTRU may wake up upon determining that the next four bits 222-228 are set to "on". For example, the WTRU may determine that a full time slot 246 is available on the N subchannel subband 206. Two symbols 248 of the 2 subchannel subband 208 may be available. Four symbols of the 1 subchannel subband 210 may be available. In the time period corresponding to the pool bits 222, 224, no transmission is available. In the time interval corresponding to the pool bit 228, a 4-symbol transmission instance 252 may be available on the N subchannel subband 206. A 7-symbol transmission time instance 254 may be available on the 2 subchannel subband 208. A full time slot 256 may be available on the 1 subchannel subband 210. During the time period corresponding to the bit 230, the WTRU may sleep.

[0093] During the time period corresponding to the pool bits 232, 234, the WTRU may not have availability 258 in the N subchannel subband. The WTRU may have an 8-symbol transmission time instance 260 in the 2-subchannel subband 208. The WTRU may have a 2-slot transmission time instance 262 in the 1-subchannel subband 210. Any number of symbols or slots may be configured as a transmission instance.

[0094] Resource selection may be performed for one or more TB transmissions of periodic and non-periodic groups. In one embodiment, a resource group may be defined as a group of N subchannels spanning M symbols. A resource group format (RGF) may be defined as a tuple (M, N). In one embodiment, a high-level process for the WTRU to perform resource selection may include the following. 1. The WTRU determines the RGF for resource selection within a resource selection window. The selection window may be determined to meet the latency requirements of the TB. 2. The WTRU may exclude a set of unavailable resources that may be occupied by another WTRU or WTRU group, and if the WTRU uses these resources, it may cause non-negligible interference to the transmission. 3. The WTRU may perform resource selection within the selection window.

[0095] The WTRU may determine a minimum value of M to support sensing. In one embodiment, the WTRU may be (pre)configured with a range of M, for example, minimum and maximum transmission durations to support the CCA process and reduce half-duplex issues. Specifically, the WTRU may be configured for a range of M based on one or more of the following: QoS of the MAC PDU, such as vehicle quality indicator (VQI), priority, latency, reliability, etc.; congestion level of the resource pool, such as CBR; size of the MAC PDU; packet size and / or buffer size and / or traffic pattern.

[0096] The clear channel assessment (CCA) process may involve consideration of multiple options. The WTRU may be configured with the following parameters to perform CCA: the bandwidth of an assessed channel; the number of assessed channels; the duration of assessing the channel; the start time of the assessment; the end time of the assessment; the energy / power threshold (RSRP, received signal code power (RSCP), SINR, or SNR) used to determine the availability of the assessed channel; and / or the duration of the reservation signal. For example, the WTRU may transmit a reservation signal when it completes the CCA process and determines that the channel is clear.

[0097] Figure 3 300, 330, 370 are diagrams showing three options 300, 330, 370 for clear channel assessment (CCA) configuration. The options for bandwidth and number of channels to be assessed for CCA are Figure 3 Described in , where the WTRU performs CCA in a bandwidth of 100 MHz.

[0098] In option 1 300, the x-axis represents time 302 and the y-axis represents frequency 304. In one example, the WTRU may perform CCA 306 on all bandwidths at once. In option 2, the x-axis again represents time 332 and the y-axis represents frequency 334. In this example, the WTRU may divide the bandwidth into 5 channels or sub-bands 336-344, each 20 MHz, and may perform CCA 346-354 in each channel to determine the availability of each channel. In option 3 360, the x-axis represents time 362 and the y-axis represents frequency 364. In this example, the WTRU may perform CCA 366-380 in each PRB 382-396 and may determine the availability of each PRB 382-396 individually.

[0099] In one embodiment, the WTRU may be configured to perform operations such as transmission or reception based on wideband energy measurements (eg, RSSI). The WTRU may perform such measurements based on automatic gain control (AGC) output without baseband processing.

[0100] In another embodiment, the WTRU may perform RSRP, RSCP, SINR or SNR measurements. The WTRU may perform FFT and subcarrier demapping to obtain energy measurements at a finer granularity (e.g., per resource block group (RBG), physical resource block (PRB) or subcarrier).

[0101] The WTRU may determine the availability of an RGF based on the results of the CCA procedure. In one embodiment, the WTRU may determine that the RGF is unavailable if the CCA procedure indicates that at least one channel overlapping with the RGF is unavailable. In another embodiment, the WTRU may determine that the RGF is unavailable if at least X% of the PRBs in the RGF are indicated as unavailable during the CCA procedure. X may be preconfigured or may be provided in WTRU-specific or group-specific signaling.

[0102] In one set of embodiments, the WTRU may determine the parameters of the CCA based on the size and / or QoS of the MAC PDU. Specifically, the CCA parameters may be dynamically changed based on the size, latency and / or QoS of the MAC PDU.

[0103] In one embodiment, the WTRU may determine the bandwidth of an evaluated channel based on the resource size of the MAC PDU. This embodiment may help the WTRU have more accurate information corresponding to the resources it wants to transmit. For example, if a MAC PDU requires 10 PRBs for transmission, the WTRU may determine that the bandwidth of the evaluated channel is 10 or 20 PRBs.

[0104] In another embodiment, the WTRU may determine an energy or power threshold, such as RSRP, RSCP, SINR, or SNR, to evaluate the availability of the evaluated channel based on the QoS characteristics of the MAC PDU (e.g., VQI, priority, or latency, etc.). This embodiment may prioritize packets with different priorities, reliability, or latency requirements. For example, the WTRU may be configured to have a difference of x decibels (xdB) between packets with consecutive priorities.

[0105] In another embodiment, the WTRU may determine the channel access time based on the priority or latency of the MAC PDU. In one embodiment, the WTRU may be configured with a higher channel access time density for high priority or latency required data, the higher channel access time density indicating the number of channel access times in a cycle. In another embodiment, the WTRU may be configured to have different channel access times for different MAC PDUs with different priorities or latency requirements. For example, for high priority or latency required data, the WTRU may be configured with a faster channel access symbol / slot than others in a time slot or subframe. This embodiment may be utilized so that high priority data may receive access to the channel faster than low priority data. Therefore, when CCA is performed, low priority channels may avoid high priority data.

[0106] In another embodiment, the WTRU may determine the duration of the reservation signal based on the priority or delay of the MAC PDU. The WTRU may determine the reservation duration for the MAC PDU based on the QoS of the MAC PDU. For example, the WTRU may determine that the duration of the reservation for a low priority MAC PDU may be shorter than the duration of the reservation signal for a high priority MAC PDU. This embodiment may limit the low priority MAC PDU from reserving a channel for a long time. Therefore, a timer or other method may be used to ensure that a low priority PDU can be sent.

[0107] Resource selection may be based on a combination of CCA, SCI decoding, and random selection. The WTRU may combine CCA and SCI decoding and random resource selection to determine the resources for transmission. In one set of embodiments, the WTRU may perform resource selection by a combination of one of the following processes. Process 1: If the power / energy measured by the WTRU in the PSSCH or PSCCH is greater than a threshold, the WTRU may exclude resources reserved by other WTRUs by decoding the SCI of other WTRUs. Process 2: The WTRU may select a subband, resource, channel, RGF, or transmission time, etc. for possible transmission and / or CCA evaluation. Process 3: The WTRU may perform a clear channel assessment (CCA) before transmitting a TB.

[0108] The WTRU may perform process 2, which determines the subband, resources, RGF, or transmission time for possible transmission and / or CCA. In one method, the WTRU may be configured to select a subband with one or any combination of the following attributes for possible transmission and / or CCA. The WTRU may select the subband with the highest number of available resources for possible transmission in the resource selection window. The WTRU may select the subband with the longest continuous available resources within the resource selection window. The WTRU may select the subband with the earliest available resources within the resource selection window. The WTRU may select a subband with N continuous available resources within the resource selection window. The WTRU may be configured to randomly select one of the multiple subbands that satisfies the above constraints. Alternatively or in combination, the WTRU may be configured to select a subband with the earliest N continuous available resources within the resource selection window. The value of N may be (pre)configured based on one or any combination of the following: the QoS of the TB, which includes the priority and / or latency of the TB; or the size of the TB.

[0109] In one method, the WTRU may be configured to select a transmission time instance for possible transmission and / or CCA based on one or both of the following: the earliest transmission time instance within a resource selection window with at least one available resource or subband; or a transmission time instance with at least N available resources / subbands. The WTRU may be configured to randomly select a transmission time instance that satisfies the above constraints, or alternatively, the WTRU may be configured to select the earliest transmission time instance that satisfies the above constraints. The value of N may be (pre)configured based on one or any combination of the following: the QoS of the TB, which includes the priority and / or latency of the TB; or the size of the TB.

[0110] In one embodiment, the WTRU may be configured to perform measurements using a wideband energy measurement method (eg, RSSI). The WTRU may perform such measurements based on automatic gain control (AGC) output without baseband processing.

[0111] In another embodiment, the WTRU may perform RSRP, RSCP, SINR or SNR measurements. The WTRU may perform FFT and subcarrier demapping to obtain energy measurements at a finer granularity (e.g., per RBG, PRB or subcarrier).

[0112] The combination of the above procedures can avoid resource conflicts in different scenarios. Procedure 1 can avoid resources being forward-committed by other WTRUs for periodic services. Procedure 2 can randomize resource conflicts between WTRUs performing dynamic resource selection for a TB transmission. Procedure 3 can mitigate resource conflicts with WTRUs performing continuous transmission of multiple TBs.

[0113] The WTRU may perform procedure 1 before the CCA procedure to further exclude reserved resources by decoding the SCI between two CCA times. The WTRU may decode any resource reservation signal / message, such as SCI_Notification message, preemption message, resource reservation sequence, etc., to exclude reserved resources in the future.

[0114] In one embodiment, the WTRU may combine three processes to perform resource selection as follows. Initially, the WTRU may perform process 1. Similar to LTE V2X, the WTRU may exclude resources whose measured power / energy is greater than a threshold and indicated in one SCI as occupied by other WTRUs. The WTRU may select M% of the total resources in the resource selection window as the set of available resources for selection based on specific criteria such as received power, RSSI, etc.

[0115] After completing process 1, the WTRU may follow the following methods. In a first method, the WTRU may perform process 2 by selecting a subband, one or more resources, one or more RGFs, or one or more transmission time instances for a possible transmission from the set of available resources in process 1. After process 2, the WTRU may perform process 3, which determines whether the selected subband, resource, RGF, transmission time instance is available. If the subband, resource, RGF transmission time instance is idle, the WTRU may transmit the packet in the selected subband, resource, RGF, or transmission time instance. Otherwise, if the channel is busy, the WTRU may wait until the channel becomes available and transmit the packet in the channel, or the WTRU may randomly select other subbands, resources, RGFs, or transmission time instances for possible transmission and perform CCA. This process may continue until the WTRU may select a resource / channel / RGF / transmission time instance for transmission, or the process may terminate when the WTRU does not find any resource for transmission within the selection window.

[0116] In a second method, the WTRU may perform process 2 by selecting X subbands / resources / RGFs / transmission instants for possible transmissions from the set of available resources in process 1. Thereafter, the WTRU may sequentially perform process 3 of determining whether a selected subband, resource, RGF, or transmission instant is available for each of the X subbands, resources, RGFs, or transmission instants until it can select a subband, resource, RGF, or transmission instant for transmission or it cannot find a subband, resource, RGF, or transmission instant for transmission in the selection window.

[0117] In a third method, the WTRU may perform process 2 by selecting a transmission time instant for a possible transmission from the set of available transmission time instants in process 1. A transmission time instant may be considered available if it contains at least X available resources after process 1, where X may be a fixed value. After process 2, the WTRU may perform a CCA to determine if any resources are available for transmission. If one or more resources are available, the WTRU may randomly select a resource for transmission. Otherwise, if all subbands are busy, the WTRU may select the next available transmission time instant, or may randomly select another available transmission time instant to perform a CCA. The process may continue until the WTRU can select a resource for transmission, or the process may terminate when the WTRU does not find a resource for transmission within the selection window.

[0118] In a fourth method, the WTRU may perform procedure 3 immediately after procedure 1 to further determine the resources available within the predefined window. Based on the resources deemed available, the WTRU may then perform procedure 2 to transmit on one or more of the randomly selected available resources.

[0119] Resource selection may be based on a combination of CCA, SCI decoding, backoff, and random selection. The WTRU may integrate CCA, SCI decoding, random resource selection, and backoff to select resources for transmission. In another set of embodiments, the WTRU may perform resource selection by combining one of the following procedures. Procedure 1: If the power / energy measured by the WTRU in the PSSCH or PSCCH is greater than a threshold, the WTRU may exclude resources reserved by other WTRUs by decoding the SCI of another WTRU. Procedure 2: The WTRU may select a subband, resource, RGF, or transmission time for possible transmission and / or evaluation of CCA. Procedure 2 may be similarly performed by selecting resources based on a combination of CCA, SCI decoding, and random selection. Procedure 3: The WTRU may perform a clear channel assessment (CCA) before transmitting a TB. Procedure 4: The WTRU may perform a backoff procedure by initially selecting a random backoff value in the range [0, B] and then reducing the backoff value following a specific criterion. This backoff procedure may be used to randomize resource conflicts and prioritize channel access for packets with different priorities.

[0120] In any of the embodiments described herein, the WTRU may perform process 1 prior to the CCA process to further exclude the reserved resources by decoding the SCI between two CCA times. The WTRU may decode any resource reservation signal / message (e.g., SCI_Notification message, preemption message, resource reservation sequence, etc.) to exclude the reserved resources in the future. In the backoff process, the range of the backoff reduction amount and / or the initial backoff value may depend on one or any combination of the following: the QoS of the MAC PDU, for example, if the MAC PDU has a higher priority, the backoff value will be reduced more, in one embodiment, the WTRU may be configured with different reduction values ​​based on the priority, latency and / or reliability of the MAC PDU; the number of failed CCAs; the time until the end of the resource selection window; the number of available channels / RGFs; the radio activity of a resource pool, carrier or bandwidth part (BWP), such as CBR; the transmission order of a TB, for example, whether the TB consists of a transmission or a retransmission, or includes a transmission or a retransmission. For example, the maximum value of the backoff value for the initial transmission may be less than or greater than the maximum value for the retransmission.

[0121] In one embodiment, the WTRU may combine four processes to perform resource selection as follows: initially, the WTRU may perform process 1 on the resources within the selection window; then, the WTRU may randomly select a backoff value in the range [0, B], where the value of B may depend on one or a combination of: the use of the resource pool, such as CBR measurement; or the QoS of the packet, such as VQI, priority, reliability, range, etc., or a value derived from any of the following: the resource group format used for transmission; characteristics of the BWP, such as bandwidth, subcarrier spacing, etc.

[0122] The WTRU may then:

[0123] In a first approach, the WTRU may perform process 2 by selecting a subband to perform CCA. The WTRU may then perform process 3, which evaluates whether the channel is available. If the channel is available, the WTRU may reduce the backoff value every time interval Ti. If the backoff value is less than or equal to zero, the WTRU may perform transmission of the TB. Otherwise, if the backoff value is greater than zero, the WTRU may wait for a period of time Tw and perform CCA again, or the WTRU may maintain the backoff value and change to another channel to perform CCA. The values ​​of Ti and Tw may be determined based on one or any combination of the following: the time division duplex (TDD) configuration of the resource pool / BWP; the QoS of the MAC PDU; the number of failed CCAs; the time until the end of the resource selection window; the number of available channels / RGFs; and / or the radio activity of the resource pool / carrier / BWP.

[0124] In the second method, the WTRU may randomly select X subbands to perform parallel CCA in each channel. The WTRU may perform CCA independently in each of the subbands, where the CCA process in each subband may be similar to the previous method. When the backoff value associated with a subband is less than or equal to zero, the WTRU may perform transmission in the subband.

[0125] In a third method, the WTRU may perform a CCA in multiple subbands. Specifically, at each transmission moment, the WTRU may determine the number of available resources, channels, or RGFs by performing a CCA in the selected subband. The WTRU may then reduce the backoff value. When the backoff value is less than or equal to zero, the WTRU may randomly select a resource for transmission.

[0126] Figure 4 is a timing diagram 400 showing a WTRU using Figure 3An example of performing resource selection according to a third method 370 is shown, in this example, the x-axis represents time 402 and the y-axis represents frequency 404. The WTRU performs resource selection in four subbands 406-412 in frequency 404. The WTRU may determine the RGF for transmission in a timeslot within a subband. First, the WTRU may exclude the resources (one or more) reserved by other WTRUs. Then, the WTRU may randomly select a backoff value in the range [0, B]. At each transmission instant, the WTRU reduces the backoff value by an amount equal to the number of available subbands. When the backoff value reaches 0, the WTRU randomly selects an available subband for transmission.

[0127] exist Figure 4 , CCA may be performed in each time slot. At CCA 414, no resources are determined to be available, and at 442, the backoff value may be set to or maintained at 6. The same is true at CCA 416, 418, and the backoff value remains the same 444, 446. In CCA 416, portions of subband 1 406 and subband 3 410 are available, but the available portions are less than the entire subband. Therefore, at CCA 416, 418, the number of available subbands 432, 434 is 0. Subsequently, at CCA 420, 4 subbands are determined to be available 436. This is because subbands 1 and 2 406, 408 have available resources determined by CCA, while subbands 3 and 4 410, 412 have available resources determined by SCI decoding. Subbands determined to be available via SCI decoding are referred to as non-forward reserved resources. After determining the 4 436 available subbands 1-4 406-412, the WTRU may subtract 4 from 6, so the backoff value becomes 2448. Subsequently, at CCA 422, subbands 1 and 2 406, 408 remain available. The number of available subbands 438 is 2, and the backoff value 450 becomes 2. Therefore, the WTRU may transmit on subband 2 408 in the next timeslot. The WTRU may continue to determine the number of available subbands 440 while transmitting. If there is more data to transmit, the WTRU may continue to perform CCA 424-430 at time 402.

[0128] Resource selection may be based on a combination of CCA, backoff and / or preemption. The WTRU may perform or determine resource allocation by combining CCA, backoff and / or preemption. In one embodiment, the WTRU may perform resource allocation by combining CCA, backoff and / or preemption. In particular, the WTRU may perform a resource allocation procedure, or the WTRU may perform preemption, which may preempt one or more transmission resources for transmission of the WTRU. Preemption may occur when one or any combination of the following conditions is met: during the resource allocation procedure, the number of CCA failures is greater than a threshold; when the time to the end of the resource selection window is less than a threshold, the backoff value is higher than a threshold. These thresholds (e.g., CCA failure number threshold, backoff threshold, or time threshold to the end of the resource selection window, etc.) may be determined by one or any combination of the following: QoS of the MAC PDU, such as VQI, priority, latency, reliability, etc.; congestion level of the resource pool, such as CBR; size of the MAC PDU; packet size and / or buffer size and / or traffic pattern.

[0129] The WTRU may perform one or more resource selections for transmission and retransmission. In one embodiment, the WTRU may determine the number of retransmissions based on the reliability or QoS (e.g., priority, reliability, and latency) of the MAC PDU and / or the radio activity (e.g., CBR) of the resource pool. The WTRU may perform resource selection for transmission and retransmission using the described method.

[0130] Resource selection may be based on a combination of CCA and time division multiplexing (TDM) between control transmissions and data transmissions. The WTRU may transmit one or more SCI_Notification messages prior to the transmission of the PSSCH. In one embodiment, the WTRU may be configured to transmit one or more SCI_Notification messages prior to the transmission of one or more PSSCHs to notify other WTRUs of the intention to transmit one or more PSSCH transmissions in the future. In one embodiment, for a PSSCH transmission, the WTRU may be configured to transmit one or more SCI_Notification messages and PSCCH, wherein the SCI_Notification message (one or more) may be used to notify other WTRUs of the priority and resource usage of the PSSCH and PSCCH, which may be used to decode the PSSCH. In another embodiment, the WTRU may be configured to transmit only SCI_Notification messages (one or more), which may be used to notify other WTRUs of the future resource usage of one or more PSSCHs and to help other WTRUs decode future PSSCH transmissions (one or more). An SCI_Notification message may implicitly or explicitly include one of the following information elements about the PSSCH transmission: the time and frequency of the PSSCH; the time and frequency of the PSCCH, the aggregation level of the PSCCH, one or more QoS parameters of the PSCCH (such as, priority, latency and / or reliability of the PSSCH; frequency and time of PSSCH retransmission(s); MCS; transmit power; granularity of the PSSCH (e.g., slot-based or non-slot-based); the time difference between the time requirement of the PSSCH(s) and the data for transmission, for example, the amount of time slack associated with the data being transmitted in the associated PSSCH.

[0131] In one example, the SCI_Notification message contains the time-frequency resource(s) and priority of the PSSCH(s) and PSCCH(s) involved. In this example, the WTRU may need to transmit both PSCCH and PSSCH in the transmission involved in the SCI_Notification. The PSCCH is used to send the SCI, which conveys the information necessary to decode the PSSCH.

[0132] In another example, the SCI_Notification message contains VQI parameters, time-frequency resources (one or more) of the PSSCH(s) involved, MCS parameters (one or more), etc. Such information may be used to decode the PSSCH(s) involved. In this example, the WTRU may or may not transmit another SCI to decode the PSSCH. The WTRU may transmit another SCI to reduce half-duplex issues. Alternatively, the WTRU may not transmit another SCI to improve spectral efficiency because the information transmitted in the SCI_Notification is sufficient to decode the PSSCH. Whether the WTRU transmits another SCI may further depend on the VQI transmitted in the relevant PSSCH.

[0133] The WTRU may be configured to transmit the SCI_Notification message in a dedicated resource pool. Alternatively, it may be sent in a PSCCH resource pool.

[0134] Figure 5 500 is a diagram illustrating a pool configuration 500 of SCI_Notification 506. In one example, a WTRU may be configured with a dedicated pool or a PSCCH resource pool 504 to transmit SCI_Notification 506 for notifying other WTRUs about future PSCCH 508 and PSSCH 510 transmissions, such as Figure 5 In another example, the WTRU may be configured to transmit an SCI_Notification 514 in a PSCCH resource pool 516 to help other WTRUs decode future PSSCH transmissions 518, such as Figure 5 Option B 512 is shown.

[0135] The WTRU may be configured to transmit multiple SCIs, all of which may be used to decode the PSSCH, and one or more SCIs may be used as SCI_Notification(s). In one embodiment, the WTRU may be configured to transmit multiple SCIs, all of which may be used to decode the PSSCH, and one or more SCIs may be used as SCI_Notification(s). Specifically, the WTRU may be configured to transmit one or more SCI_Notifications prior to the transmission of the PSSCH, which may be used to notify other WTRUs of the resources used for the PSSCH transmission and the parameters used to decode the PSSCH. The WTRU may also be configured to transmit one SCI in a TB used for the PSSCH. This embodiment may be motivated to increase the probability of successfully decoding the PSCCH by reducing half-duplex issues.

[0136] It should be noted that, in the following, SCI_Notification may refer to a message sent prior to the transmission of the PSCCH.When SCI_Notification is sent, the WTRU may or may not be configured to send SCI in a TB of the PSSCH.

[0137] The receiver WTRU may determine the parameters of the PSCCH transmission based on decoding the SCI_Notification. In one embodiment, the WTRU may implicitly or explicitly determine the parameters of the PSCCH involved in the transmission based on decoding the SCI_Notification. Specifically, the WTRU may determine one or any combination of the following parameters for the PSCCH transmission: the time-frequency resources of the PSCCH; the MCS; the aggregation level, which may be based on one or any combination of the following information of the SCI_Notification: the amount or location of the time-frequency resources of the SCI_Notification and QoS parameters such as priority, latency and reliability.

[0138] In one embodiment, the transmitter WTRU may be configured to use a predetermined MCS and a certain number of symbols and resource elements for transmitting the PSCCH based on the QoS of the data. In one embodiment, the transmitter WTRU may include the initial transmission of the PSCCH involved in the SCI_Notification. The receiver WTRU may determine the time-frequency resources and MCS of the PSCCH transmission based on the QoS of the data and the initial transmission time included in the SCI_Notification. In another embodiment, the transmitter WTRU may be configured to have a time interval between the SCI_Notification and the PSCCH, which may be based on the QoS of the data. The receiver WTRU may determine the time-frequency resources and / or MCS of the PSCCH transmission based on the QoS of the data.

[0139] The WTRU may determine whether to use SCI_Notification. In one embodiment, the WTRU may determine whether to use SCI notification based on the properties of its own transmission in combination with the measured environment. Specifically, in some cases, the WTRU may transmit a TB by first transmitting an SCI_Notification to reserve resources for the PSCCH / PSSCH, and then transmit the PSCCH / PSSCH. In other cases, the WTRU may perform transmission of a TB by performing resource selection only for the PSSCH or PSCCH alone.

[0140] The WTRU may determine whether to use SCI_Notification based on any or a combination of the following. In one embodiment, the QoS and / or logical channel of the TB to be sent may provide a determination. For example, the WTRU may perform an SCI notification when the reliability of the transmission is above a certain threshold. For example, the WTRU may perform an SCI notification when the latency associated with the transmission is above or below a threshold, where the threshold may further depend on the amount of available resources from the sensing process. For example, the WTRU may be configured with a set of logical channels for which transmissions with SCI_Notification are allowed. If a TB contains data from one or more such logical channels, the WTRU may perform an SCI_Notification for transmitting the TB.

[0141] In one embodiment, measurements at the WTRU (e.g., sensing or CBR measurements) may help determine whether to use SCI_Notification. For example, when the percentage of available resources is above a certain threshold, the WTRU may perform SCI notification for the TB. The determination regarding the available resources may be based on detection of SCI_Notification and / or SCI transmissions indicating forward reserved resources. For example, when the measured CBR or similar congestion metric is above a threshold, the WTRU may perform SCI_Notification for the TB.

[0142] The size of the TB to be transmitted may help determine whether to use SCI_Notification. For example, when the TB to be transmitted is larger than a threshold or when the number of consecutive TBs may exceed a threshold, the WTRU may perform SCI notification for the TB. For example, when the number of RBs in the same timeslot occupied by the TB to be transmitted and / or the number of consecutive RBs in the same timeslot exceeds a threshold, the WTRU may perform SCI notification for the TB.

[0143] The resource pool configuration may be used to determine whether to use SCI_Notification. For example, the WTRU may perform SCI_Notification when one or more physical sidelink feedback channel (PSFCH) resources are periodically (pre)configured with a period less than or equal to N slots, where the value of N may be (pre)configured or provided by higher layer signaling.

[0144] The type of TB transmission (e.g., unicast, multicast, or broadcast transmission type) may be used to determine whether to use SCI notification. For example, the WTRU may perform SCI notification for unicast and / or multicast services. In an example, the SCI notification may not be used for unicast and / or multicast services, but may be used for broadcast services.

[0145] In an exemplary embodiment, the WTRU may be configured with a table of threshold reliability values ​​for a given CBR range, for example by using a channel contention value.The WTRU may perform SCI notification whenever the reliability of the packet to be transmitted is above a threshold associated with the measured CBR.

[0146] The WTRU may determine when to transmit the SCI_Notification based on the QoS requirements of the packet. The WTRU may determine to transmit the SCI_Notification message based on the QoS requirement(s) of the packet. In one embodiment, the WTRU may be configured to determine the SCI_Notification transmission window based on the priority of the packet. For example, the WTRU may be configured to transmit the SCI_Notification message within the range [n+T min,n+T max ], where n is the time at which the WTRU performs resource selection, T min may depend on the capabilities of the WTRU, and T max It can be determined based on the priority of the group.

[0147] The WTRU may determine the PSSCH transmission window based on the QoS of the packet (e.g., priority and / or latency). The WTRU may be configured to select PSSCH and / or PSCCH resources in a resource selection window within the range [n+T1, n+T2], where T1 and T2 may be determined based on the QoS of the packet (e.g., priority and / or latency). Specifically, if the priority and / or latency requirements of the packet are high (low PPPP value), T1 and T2 may be smaller. Alternatively, the WTRU may be configured to select PSSCH and / or PSCCH resources in a resource selection window within the range [n+T1, n+T2]. max + offset, n+T2] to select PSSCH and / or PSCCH resources, where the offset can be determined based on the priority of the group or a fixed value.

[0148] The WTRU may determine the PSSCH and / or PSCCH transmission window based on the result of the resource selection for SCI_Notification. In one embodiment, the WTRU may determine the resource selection window for PSSCH and / or PSCCH transmission based on the result of the resource selection for SCI_Notification(s). Specifically, the WTRU may be configured to determine the SCI_Notification transmission window in the range [n+Tmin, n+Tmax]. The values ​​of Tmin and / or Tmax may be determined based on the QoS of the packet. The WTRU may first perform resource selection for SCI_Notification(s). Assuming that the last resource of SCI_Notification for a resource allocation process may occur in time slot n+T, the WTRU can determine the resource selection window for PSSCH and / or PSCCH transmission within the range of [n+T+offset, n+T2], where the offset can be determined based on any of the following: the QoS of the packet (priority, latency, etc.); a fixed value; the time difference between T and Tmax, or the time difference between T and Tmin; the congestion level of the resource (e.g., CBR); and T2 can be determined based on different functions, which may depend on any of the factors listed above for determining the offset.

[0149] The WTRU may perform resource selection for SCI_Notification, PSSCH, and / or PSCCH in a single resource selection window by determining a minimum offset. In one or more embodiments, the WTRU may be configured with a time offset limit between SCI_Notification and the PSSCH and / or PSCCH to which it refers. Specifically, the WTRU may determine to perform resource selection for SCI_Notification, PSSCH, and / or PSCCH within a resource allocation window. In some embodiments, the WTRU may be configured with a resource selection window for SCI_Notification and PSSCH and / or PSCCH in the range [n+T1, n+T2], where the values ​​of T1 and T2 may be determined based on the QoS of the data (e.g., latency, priority, reliability) and / or the congestion level of the resource pool (e.g., using CBR).

[0150] The parameter offset may be defined as the minimum time gap between SCI_Notification and PSSCH and / or PSCCH. In another embodiment, the parameter offset may be defined as the time gap between SCI_Notification, PSSCH and / or PSCCH. The offset value may be pre-configured or configured based on the QoS of the data (such as priority, latency and reliability) or by the gNB via Radio Resource Control (RRC) signaling or via System Information Broadcast (SIB).

[0151] In one embodiment, the WTRU may be configured to first perform resource selection for SCI_Notification, and then the WTRU may determine the resource selection window for PSSCH and / or PSCCH taking into account the limitation of the time gap or offset between SCI_Notification and PSSCH and / or PSCCH. The WTRU may be configured to perform resource selection for SCI_Notification in the range [n+T1, n+T2-offset-delta], where the value of delta (difference) may be determined based on the QoS of the data (e.g., latency, priority, reliability) and / or the congestion level of the resource pool (e.g., CBR). Assuming that the resources for SCI_Notification may occur in time slot n+T, the WTRU may be configured to perform resource selection for PSSCH and / or PSCCH in the range [n+T+offset, n+T2].

[0152] In one embodiment, the WTRU may first perform resource selection for PSSCH and / or PSCCH, and then the WTRU may perform resource selection for SCI_Notification taking into account the time slot limit offset. Specifically, the WTRU may be configured to select a resource selection window for PSSCH and / or PSCCH in the range [n+T1+offset+delta,n+T2], where delta may be determined based on the QoS of the data (e.g., latency, priority, reliability) and / or the congestion level of the resource pool (e.g., CBR). Assuming that the resources for PSSCH and / or PSCCH transmission may occur in time slot n+T, the WTRU may perform resource selection for SCI_Notification(s) in the range [n+T1,n+T-offset].

[0153] The WTRU may perform sensing by decoding the SCI and SCI_Notification. The WTRU may use the RSRP / RSSI / RSCP of the SCI or SCI_Notification resources to determine the availability of the PSSCH resources indicated by the corresponding SCI or SCI_Notification. Specifically, if the RSRP / RSSI / RSCP of the SCI or SCI_Notification is greater than a threshold, the WTRU may determine that the corresponding PSSCH is considered unavailable. Otherwise, the corresponding PSSCH resources may be considered available.

[0154] The WTRU may determine the availability of PSSCH and / or PSCCH resources based on the QoS parameter(s) provided in the SCI_Notification. In one embodiment, the WTRU may determine the availability of PSSCH and / or PSCCH resources involved in the SCI or SCI_Notification based on the QoS parameter(s) provided in the SCI or SCI_Notification. Specifically, the WTRU may determine the QoS associated with the PSSCH and / or PSCCH involved. The WTRU may determine the availability of the PSSCH and / or PSCCH resources involved by comparing the RSRP / RSSI / RSCP measured in the SCI or SCI_Notification resources with a threshold, which may be determined based on the relative QoS of the PSSCH and / or PSCCH involved and the pending TBs queued by the WTRU. If the threshold is not configured or the threshold is configured to 0 (W), the WTRU may directly exclude the resources involved by the SCI or SCI_Notification.

[0155] A WTRU that detects an SCI or SCI_Notification transmitted by another WTRU may decide to override such SCI / SCI_Notification and select resources that are the same / overlapping with the resources reserved by the SCI / SCI_Notification. The WTRU may make such a decision based on any of the following: the priority of the data to be transmitted by the WTRU is higher than the priority announced by the received SCI / SCI_Notification; the amount of available resources, for example, the WTRU TB is allowed to be transmitted when the available resources are below a threshold; the time difference between the decoded PSSCH and its time requirement (e.g., slack time) is higher than a threshold and / or is greater than the latency requirement of the WTRU's own transmission; the measured CBR is higher than a threshold.

[0156] A WTRU that decides to override a SCI_Notification may perform resource selection and transmission of its own SCI notification such that it occurs at at least some time offset before the PSSCH / PSCCH resources reserved by the original SCI_Notification that is being overwritten. The WTRU may also use modified resource selection criteria / parameters, such as modified thresholds, larger resource pools, increased TX power, or a larger number of repetitions, during resource selection and / or transmission of its own SCI_Notification. Such modifications may be used to ensure that the SCI_Notification can be reliably received by the original WTRU that transmitted the original SCI_Notification. Alternatively, or in combination, the WTRU may cancel the transmission of the overlay SCI_Notification if it cannot find resources for its own SCI_Notification that occur at at least some offset before the reserved PSSCH / PSCCH resources.

[0157] When the WTRU detects that its selected SCI_Notification or PSSCH and / or PSCCH resources may conflict with another SCI_Notification or PSSCH and / or PSCCH transmission, the WTRU may reselect PSSCH and / or PSCCH and / or SCI_Notification resources. Specifically, the WTRU may decode SCI_Notification or SCI messages from other WTRUs. After decoding these messages, if the PSSCH and / or PSCCH or SCI_Notification resources of another transmission overlap with its own PSSCH and / or PSCCH or SCI_Notification resources, the WTRU may reselect another resource for SCI_Notification or PSSCH and / or PSCCH transmission.

[0158] The WTRU may determine the conflict handling procedure based on whether the SCI_Notification has been transmitted. In some embodiments, the WTRU may perform two different conflict handling procedures. One procedure may be performed before the transmission of the SCI_Notification, while the other procedure may be performed after the transmission of the SCI_Notification. This embodiment may be activated to distinguish the behavior of other WTRUs before the SCI_Notification transmission. Conflict handling before the SCI_Notification transmission may be activated to avoid conflicts between two WTRUs selecting the same resources, where one WTRU may not have information about the transmission of the other WTRU. However, conflict handling after the SCI_Notification transmission may be activated to address situations where one WTRU may need to preempt the resources of another WTRU.

[0159] The WTRU may perform potential conflict handling after selecting one or more resources for SCI_Notification and / or PSSCH and / or PSCCH and before SCI_Notification transmission. In one embodiment, the WTRU may perform potential conflict handling after selecting resources for SCI_Notification and / or PSSCH and / or PSCCH and before SCI_Notification transmission. Specifically, the WTRU may monitor other WTRU's transmissions to detect potential conflicts after selecting resources for SCI_Notification and / or PSSCH and / or PSCCH and before SCI_Notification transmission. The WTRU may perform resource reselection or discard packets for SCI_Notification and / or PSSCH and / or PSCCH if one or any combination of the following conditions is met: the WTRU detects an SCI or SCI_Notification involving or reserving a resource that conflicts with the resource selected by the WTRU; the RSRP_PSSCH or RSRP_PSCCH measured on the SCI / SCI_Notification or the PSSCH resource involved is greater than a threshold. The threshold may be preconfigured, or configured by the network via SIB or RRC messages.

[0160] The WTRU may perform potential conflict handling after the SCI_Notification transmission and before the corresponding PSSCH and / or PSCCH transmission. In one embodiment, the WTRU may perform potential conflict handling after the SCI_Notification transmission. Specifically, the WTRU may monitor the transmissions of other WTRUs to detect potential conflicts after selecting resources for the SCI_Notification and / or PSSCH and / or PSCCH and after the SCI_Notification transmission. The WTRU may perform resource reselection or discard packets for the SCI_Notification and / or PSSCH and / or PSCCH if one or any combination of the following conditions is met: the WTRU detects an SCI or SCI_Notification involving or reserving a resource that conflicts with the resource selected by the WTRU; the priority of the notified / reserved resource is greater than the priority of the pending TB of the WTRU; the RSRP_PSSCH or RSRP_PSCCH measured on the SCI / SCI_Notification or the PSSCH resource involved is greater than a threshold. The threshold may be preconfigured or configured by the network via a SIB or RRC message.

[0161] The WTRU may determine whether to transmit an SCI_Notification to notify future PSSCH transmission(s). In some embodiments, the WTRU may determine to transmit one or more SCI_Notification messages based on one or any combination of the following: QoS characteristics of the MAC PDU, such as VQI, priority, latency, reliability, etc.; congestion level of the resource pool, such as CBR; size of the MAC PDU; packet size and / or buffer size and / or traffic pattern.

[0162] In one embodiment, the WTRU may determine to transmit one or more SCI_Notification messages if the VQI of the data is within a certain range. In another embodiment, the WTRU may determine to transmit SCI_Notification message(s) if the priority, reliability, or latency requirement of the MAC PDU is greater than a threshold. This embodiment may reduce the probability of collision of high priority, high reliability, or high latency data by providing notification prior to these transmissions.

[0163] In another embodiment, the WTRU may determine to transmit the SCI_Notification message(s) if the CBR of the resource pool is greater than a threshold. This embodiment may reduce conflicts when the resource pool is congested. The WTRU may perform CBR measurements on the control, data, or SCI_Notification-dedicated resource pools to determine whether it should transmit the SCI_Notification message(s).

[0164] In another embodiment, if the size of the PSSCH transmission is greater than a threshold and / or the WTRU's buffer size is greater than a threshold, the WTRU may determine to transmit the SCI_Notification message(s). This embodiment may reduce the probability of collision for large size packets. This is because the probability of a transmission collision for a large TB may be higher than the probability of a transmission collision for a small TB.

[0165] Figure 6is a timing diagram 600 illustrating channel access 600 for SCI_Notification message(s) with different priorities. In one embodiment, the WTRU performs resource selection for the SCI_Notification message(s). Based on the QoS characteristics of the MAC PDU (e.g., VQI, priority, latency, reliability, etc.) and / or the congestion level of the resource pool (e.g., CBR) and / or the resource allocation mode, the WTRU may be configured for different channel access moments to transmit the SCI_Notification message(s). In one embodiment, the resource allocation mode includes a network scheduling mode and a WTRU or WTRU scheduling mode. In one embodiment, for a specific CBR range, the WTRU may be (pre)configured with different channel access moments for the SCI_Notification message(s) based on the QoS characteristics of the MAC PDU. In one example, when the CBR is low, the WTRU may be (pre)configured with the same channel access moment for the SCI_Notification message(s) for all MAC PDUs; however, as Figure 6 As shown, when the CBR is high, the WTRU may be configured to access the channel in the second symbol of each time slot if it has a high priority transmission. If the WTRU has a medium priority transmission, the WTRU may be configured to access the channel in the fourth symbol of each time slot. If the WTRU has a low priority transmission, the WTRU may be configured to access the channel in the sixth time slot of every other time slot.

[0166] exist Figure 6 6, the x-axis represents time 602 and the y-axis represents frequency 604. CCA 606-612 can be performed at the beginning of four time slots 614-620. In time slot 614, symbol 622 can be used for high priority. Subsequently, in the same time slot 614, symbol 624 can be used for medium priority transmission. In time slot 616, symbol 626 can be used for high priority transmission. Another symbol 628 can be used for medium priority transmission, followed by symbol 630 for low priority transmission. In this way, symbols for low priority transmission can be dedicated only every other time slot, thereby saving bandwidth for high priority transmission. Similarly, time slot 618 can include high priority symbol 632 and medium priority symbol 634. Time slot 620 can include high priority symbol 636, medium priority symbol 638 and low priority symbol 640.

[0167] In another embodiment, the WTRU may be configured to rely on different channel access moments based on a combination of resource allocation mode and / or data QoS. Specifically, if the WTRU operates in WTRU scheduling mode, the WTRU may be configured to access the channel after or before one or more symbols. Alternatively, the WTRU may be configured to access the channel in every even timeslot if the WTRU operates in network scheduling mode and in every odd timeslot if the WTRU operates in WTRU scheduling mode.

[0168] The WTRU may determine the number of SCI_Notification transmissions. In one embodiment, the WTRU may determine the number of SCI_Notification messages for one or more PSSCH and / or PSCCH transmissions based on one or a combination of: QoS characteristics of the MAC PDU, such as VQI, priority, latency, reliability, etc.; congestion level of the resource pool, such as CBR; size of the MAC PDU; packet size and / or traffic pattern.

[0169] In one embodiment, the WTRU may determine the number of SCI_Notification messages based on a combination of the reliability of the MAC PDU and the congestion level (e.g., CBR) of the resource pool. Specifically, for a specific CBR range, the WTRU may be configured with the number of SCI_Notification messages based on the reliability of the MAC PDU. In one embodiment, the WTRU may be configured with the number of SCI_Notification opportunities based on the size of the MAC PDU. Specifically, the WTRU may be configured to transmit more SCI_Notification messages for large size packets. This embodiment may reduce the probability of collision of large size packets, which may help reduce the waste of resources due to congestion of large size packets.

[0170] In one embodiment, the WTRU may perform resource selection for multiple SCI_Notification messages. Specifically, the WTRU may need to perform resource selection for N SCI_Notification messages. The WTRU may randomly select N+M possible time-frequency resources to evaluate the transmission resources. The WTRU may perform CCA sequentially in each selected time-frequency resource, and when the transmission resources are available, may perform transmission in each available time-frequency resource. The process may terminate when the WTRU transmits all N SCI_Notification messages or the WTRU reaches the end of the resource selection window. This embodiment may ensure that the WTRU is able to select transmission resources for all N SCI_Notification messages, because if the WTRU only selects N possible time-frequency resources to evaluate the transmission resources, then due to the possibility that the channel is unavailable after the CCA event, the WTRU may not be able to select sufficient transmission resources for N SCI_Notification transmissions within the resource selection window. The value of M may be determined based on one or any combination of the following: QoS characteristics of the MAC PDU (e.g., VQI, priority, latency, reliability, etc.); congestion level of the resource pool, such as CBR; size of the MAC PDU; packet size and / or traffic pattern. It should be noted that this embodiment may be applied to resource allocation for any transmission, such as SCI_Notification, PSSCH, PSCCH, etc.

[0171] Figure 7 FIG7 is a diagram 700 showing a WTRU randomly selecting four time-frequency resources to perform CCA for transmitting two SCI_Notification messages. Figure 7 , the WTRU randomly selects four time-frequency resources 726, 720, 730, 732 in time 702 and frequency 704 to perform CCA for transmitting two SCI_Notification messages.

[0172] exist Figure 7In the example shown, based on the CBR and / or QoS and / or size of the MAC PDU, the WTRU may need to transmit two SCI_Notification messages, and the WTRU determines to select four time-frequency resources 726, 720, 730, 732 to perform CCA 734-740 for potential SCI_Notification transmissions. During the CCA process, the WTRU determines that the transmission resource of the second randomly selected time-frequency resource 720 is occupied. Finally, the WTRU may transmit two SCI_Notification messages in the third time-frequency resource 730. Since enough SCI_Notification messages have been transmitted, the WTRU may determine to stop the CCA for the fourth CCA time-frequency resource 732. The WTRU may use one or more SCI_Notification messages to notify one or more PSSCH and / or PSCCH transmissions. The WTRU may use one or more SCI_Notification messages to notify one or more PSSCH and / or PSCCH transmissions.

[0173] Figure 8 800 is a diagram illustrating an option for SCI_Notification to notify future PSSCH and / or PSCCH transmission(s). In one embodiment, the WTRU may use multiple SCI_Notification messages 812, 814 to notify one PSCCH 816 and / or PSSCH 818 transmission, such as Figure 8 Option A 810 of 810. This embodiment can alleviate the half-duplex problem where the WTRU misses one SCI_Notification message. The WTRU can detect other SCI_Notification messages to obtain information about future PSSCH and / or PSCCH transmissions.

[0174] In another embodiment, the WTRU may use one SCI_Notification message 832 to notify multiple PSCCH transmissions 834, 836 and / or PSSCH transmissions 838, 840, such as Figure 8 Option B 830 is shown. This embodiment can reduce the number of SCI_Notification transmissions to notify multiple PSSCH and / or PSCCH transmissions.

[0175] In another embodiment, the WTRU may combine the above two methods by having one SCI_Notification message to indicate multiple PSSCH and / or PSCCH transmissions, and having multiple SCI_Notification messages to notify one PSSCH and / or PSCCH transmission.

[0176] Option C 850 shows two SCI_Notification messages 852 , 854 indicating multiple PSCCH transmissions 856 , 858 and multiple PSSCH transmissions 860 , 862 .

[0177] The SCI_Notification message may indicate multiple transmissions of a TB. Specifically, the SCI_Notification may explicitly or implicitly include one or any combination of the following information for multiple transmissions of a TB: time-frequency resources for initial transmission and possible retransmission (one or more); frequency hopping pattern / index for transmission and retransmission (one or more); time gap between transmission and retransmission; time gap between two retransmissions; number of retransmissions (one or more); pattern index for transmission.

[0178] The WTRU may determine the transmission pattern of the TB based on the QoS of the TB. In one embodiment, the WTRU may determine the parameters for transmitting the TB based on the QoS of the TB and / or the congestion level (e.g., CBR) of the resource pool. Specifically, the WTRU may determine one or any combination of the following parameters based on the QoS of the TB and / or the congestion level of the resource pool: the size of the time-frequency resource; the number of transmissions; the time gap between the initial transmission and the retransmission and the time gap between two retransmissions; whether frequency hopping is enabled or disabled.

[0179] In one example, the WTRU may determine the number of transmissions of a TB based on the reliability of the TB. The WTRU may determine the time gap between the initial transmission and the retransmission and the time gap between two retransmissions based on the latency and / or priority of the TB. Alternatively, the WTRU may decide whether to enable or disable frequency hopping based on the reliability of the TB.

[0180] The WTRU may change the resource selection process for PSCCH and / or PSSCH transmission based on whether SCI_Notification is transmitted. In one embodiment, the WTRU may change the resource selection process for PSCCH and / or PSSCH transmission based on whether SCI_Notification is transmitted. If the SCI_Notification message is not transmitted, the WTRU may select resources for PSCCH and / or PSCCH transmission based on any one or more of the processes described herein. Alternatively, if one or more SCI_Notification messages are transmitted, the WTRU may select resources for PSCCH and / or PSCCH as follows. When SCI_Notification is sent, the WTRU may perform resource selection for PSSCH and / or PSCCH transmission. The WTRU may exclude resources forward reserved by PSCCH transmission or resources notified by SCI_Notification and / or via preemption.

[0181] In one embodiment, the WTRU may exclude resource(s) forward reserved by PSCCH transmission(s). Specifically, for resources forward reserved by PSCCH(s), the WTRU may use a similar process as in LTE V2X, where the WTRU may exclude a reserved resource if its PSSCH_RSRP and / or PSCCH_RSRP is greater than a threshold.

[0182] The WTRU may exclude PSSCH and / or PSCCH resources notified by SCI_Notification, preemption, resource reservation sequence, etc. In another embodiment, the WTRU may exclude resources notified by SCI_Notification, preemption, resource reservation sequence, etc. Specifically, if the RSRP measured on the SCI_Notification or preemption message is greater than a threshold, the WTRU may exclude one or more resources notified by the SCI_Notification message or preemption message. In one embodiment, the WTRU may be (pre)configured with a table of RSRP thresholds (one or more). The WTRU may then determine the index and the corresponding threshold based on the QoS of the transmission (e.g., VQI, priority, latency, reliability) and the QoS of the SCI_Notification or preemption message.

[0183] In one embodiment, the WTRU may use the same table of PSSCH_RSRP; however, the WTRU may apply a delta value to the value in the table when comparing with the RSRP of the SCI_Notification or preemption message. The delta value may be (pre)configured or calculated by the WTRU, which may depend on the SCI_Notification or preemption message(s) and the transmission parameters of the WTRU's PSSCH, such as power, MCS, resource quantity size, etc. This embodiment may reduce the number of threshold tables that the WTRU needs to maintain and may reduce the complexity of the resource selection process when the WTRU has to use multiple threshold tables.

[0184] Fig. 9 is a timing diagram 900 showing the calculation of the sidelink received signal strength indicator (S-RSSI) for candidate resources. The WTRU may calculate the S-RSSI for each of a plurality of candidate resources 906-910 to determine X% of the candidate / available resources based on the S-RSSI. In one embodiment, the WTRU may calculate the S-RSSI for each candidate resource to determine X% of the candidate / available resources to report to an upper layer (e.g., a MAC layer). Specifically, the WTRU may calculate the S-RSSI for the candidate resource by averaging the S-RSSI measured in the same frequency resource of the candidate resource in a time slot / time instant, where the time slot / time instant may be represented by nT*j, where n is the time instant of the candidate resource, j is a non-negative integer, and T may be determined as the greatest common divisor of all reservation periods that the resource pool can support. The value of T may be (pre)configured or notified to the WTRU by the network via RRC or SIB. The WTRU may exclude time slots / time instants having non-periodic / event triggered transmissions in the frequency resources of the candidate resource. In Fig. 9 In one example shown, the resource pool supports reservation periods of 5, 10, 20, 50, j*100 (j=1…10) (ms). The WTRU determines T=5 ms and may therefore delay the S-RSSI calculation for each period of the 5 ms period 912-918. In addition to the event-triggered / non-periodic transmission time slots, the WTRU determines the S-RSSI of the candidate resource by averaging the measured S-RSSI for the time slots represented by n-5j. The WTRU may transmit an SCI_Notification 920. The WTRU may proceed to determine another candidate resource, such as candidate resource 922, in the resource selection window 924 at time 902 and frequency 924.

[0185] The WTRU may determine the PSSCH and PSCCH multiplexing scheme based on the characteristics of the data. In one set of embodiments, the WTRU may be configured to perform TDM, frequency division multiplexing (FDM), or a mix between FDM and TDM on the PSCCH and PSSCH. The WTRU may determine the multiplexing scheme between the PSSCH and PSCCH based on the characteristics of the data. Specifically, the multiplexing scheme may be determined based on one or more combinations of: the type of data, e.g., periodic versus aperiodic; the QoS of the data, e.g., priority, latency, and / or reliability; resource pool / BWP configuration, e.g., SCS; and / or available reservation grants.

[0186] In one embodiment, the WTRU may determine a multiplexing scheme based on the type of data it is transmitting (e.g., aperiodic versus periodic). For example, the WTRU may determine an FDM scheme for periodic data and a TDM scheme for aperiodic data. In order to distinguish between periodic data and aperiodic data, the WTRU may be configured with two orthogonal logical channel sets for each type of data. This motivation may be to reduce the number of transmissions of periodic data and resource conflicts for aperiodic data.

[0187] In one embodiment, the WTRU may determine the multiplexing scheme based on the availability of the reserved grant and / or the QoS of the data. In one embodiment, if the reserved grant is not applicable for MAC PDU transmission or the WTRU does not have the reserved grant, the WTRU may determine the TDM scheme. The reserved grant may not be suitable for MAC PDU transmission due to one or any combination of the following. The reserved grant may not meet the QoS of the MAC PDU, such as priority, latency, etc. The reserved grant may be dedicated to other services.

[0188] In another embodiment, when the WTRU does not have a suitable reservation grant and the reliability and / or priority of the MAC PDU is greater than a threshold, the WTRU may determine a TDM scheme. These methods can help avoid resource conflicts for high priority and / or reliability MAC PDUs. Alternatively, if the WTRU has suitable reserved resources for MAC PDU transmission, the WTRU may determine an FDM scheme between the PSSCH and the PSCCH.

[0189] In one set of embodiments, the WTRU may determine to perform resource selection for multiple TBs. These embodiments may help the WTRU simplify the resource selection process. A multi-TB resource may be defined as a set of resources for transmitting N TBs, where each TB transmission may require K beam scans. A multi-TB resource format (MRF) may be defined as a set of (N, K). An MRF may belong to one of the following: one or more TBs, each TB requiring one beam transmission; one or more TBs, each TB requiring K>1 beam transmissions.

[0190] The WTRU may determine to perform resource selection for multiple TBs when one or more of the following conditions are met: when the WTRU is configured with a service that requires resource selection for multiple TBs (e.g., sensor sharing, queuing, etc.); when the buffer status of the data is greater than a specific threshold; when the resource pool CBR is less than or greater than a certain threshold; when it is configured to perform CA transmission or multi-BWP transmission; when data for a specific logical channel is received (e.g., such a logical channel is associated with a data or radio bearer with a packet greater than a specific threshold); when the number of selectable carriers or BWPs available to the WTRU is lower than a specific value; when using a separate resource selection process or sidelink process to transmit a TB would cause the WTRU to exceed the maximum number of its sidelink processes; when the size of an arriving packet is greater than a threshold.

[0191] The WTRU may determine when to reserve one or more resources for the transmission of multiple TBs. In one embodiment, the WTRU may determine to reserve resources for the transmission of multiple TBs using one SCI_Notification based on one or any combination of the following: when the buffer status of the buffered data is greater than a certain threshold; when the WTRU is configured with a service that requires resource selection for multiple TBs (e.g., sensor sharing, or queuing, etc.); when the buffer status of the data is greater than a certain threshold; when the CBR of the resource pool is less than or greater than a certain threshold; when the WTRU is configured to perform CA transmission or multiple BWP transmission; when data for a specific logical channel is received, for example, the logical channel is associated with a data or radio bearer having at least one packet greater than a certain threshold; when the number of selectable carriers or BWPs available to the WTRU is below a certain value; when the use of a separate resource selection process or sidelink process to transmit a TB would cause the WTRU to exceed its maximum number of processes; when the size of the arriving packet is greater than a threshold; when the remaining latency requirement(s) of certain TBs is below a threshold.

[0192] The WTRU may use the SCI associated with one TB to reserve resources for another TB. In one embodiment, the WTRU may be configured to use an SCI associated with a PSSCH transmission of one TB to reserve one or more resources for transmission(s) of the same or different TBs. The WTRU may use the one or more reserved resources for one or more transmissions of: for example, a retransmission of the same TB using the same or different redundancy version (RV) as the initial transmission; a transmission of another TB in the same semi-persistent scheduling (SPS) service; a transmission of another TB in a burst service, for example, the two TBs may belong to the same packet from upper layers; or a transmission of any other TB.

[0193] The WTRU may use different mappings in the time domain to indicate the reserved resources for transmitting a TB. In one embodiment, the WTRU may be configured to use different mappings between the bit field indicated in the SCI and the timing offset between the SCI transmission and the timing of the resources reserved for transmitting the TB. The method may be motivated to support the WTRU to indicate different types of reserved resources, such as reserved resources for SPS services, retransmissions, and burst services. For example, the WTRU may be configured to use 3 bits in the SCI to indicate the reserved time resources for retransmitting a TB and transmitting another TB in a burst service, where a value indicated by the bit field may correspond to the timing offset of the number of time slots between the SCI transmission and the reserved resources. Alternatively, the WTRU may also use 3 bits in the SCI to indicate the reserved time resources for SPS service transmission; however, a value indicated by the bit field may correspond to an index in a table of SPS periods, which may be described in Table 1.

[0194]

[0195]

[0196] Table 1: Mapping between index and SPS period

[0197] The WTRU may use one or more SCIs associated with different transmissions to reserve different types of transmissions. In one embodiment, the WTRU may be configured to use SCIs associated with different transmissions to reserve different resources for different types of transmissions. This approach may be driven as a balance between the signaling overhead required in the SCI and the efficiency of resource reservation. In one example, the WTRU may be configured to use the SCI associated with the first X transmissions to reserve resources for one or more retransmissions and another TB in a burst service. The WTRU may also be configured to use the SCI associated with the last Y transmissions (one or more) to reserve resources (one or more) for the transmission of other TBs (one or more) associated with the SPS service. In this method, the values ​​of X and Y may be (pre)configured, which may be determined based on the number of blind retransmissions of a TB.

[0198] The WTRU may be configured to indicate the type of TB it has reserved in the SCI. In one embodiment, the WTRU may be configured to reserve one or more resources for one or more types of TB transmissions. In one method, the WTRU may indicate the type of TB it has reserved in the SCI by using one or more bits in the SCI. For example, the WTRU may use one bit to indicate whether it is reserving resources for TBs in SPS services or for TBs in burst services.

[0199] The WTRU may be configured to use a reservation table where different sets of codepoints may be used for reservation of different types of TBs. For example, the WTRU may be configured with two sets of codepoints in the table where the first set is used to reserve resources for TBs in SPS traffic and the other set is used to reserve resources for TBs in burst traffic. This method may be motivated to allow a receiver WTRU to distinguish between different types of TB reservations where SPS reservations may apply to multiple cycles and burst reservations may apply to only one cycle.

[0200] The WTRU may be configured to determine what type of TB to reserve based on the pool configuration. In one embodiment, the WTRU may be configured to reserve resources in the resource pool for one or any combination of the following TB transmissions: TB transmissions for SPS services; TB transmissions for burst services; or one or more TB retransmissions. This approach may be motivated to allow the system to enable / disable one or more types of resource reservations.

[0201] Resource selection may be performed in one BWP / carrier. The WTRU may treat resources for multiple transmissions as a single resource or sidelink process during the resource selection process. The WTRU may use the process / algorithm to perform resource selection for multiple transmissions. This embodiment may reduce the number of resource selections or resource selection time for multiple transmissions.

[0202] In one embodiment, the WTRU determines the MRF to perform resource selection. The WTRU may determine the values ​​of N and K in the MRF based on one or a combination of: the WTRU's buffer status; the CBR of the resource pool; the resource pool configuration.

[0203] The WTRU may first attempt resource selection with a specific number of side link processes, and then increase or decrease the number of side link processes when the first attempt fails. The method may be adjusted to select resources for one or more side link processes or when the WTRU still has data available at the buffer. Specifically, the WTRU may be configured to perform a multi-stage resource selection process for multiple transmissions, where each stage may be associated with an MRF. The WTRU may gradually reduce the number of transmissions used for each size link process after each stage of resource selection. The WTRU may be (pre)configured to perform resource selection for a predefined set (N, K).

[0204] The failure / success of a particular attempt at resource selection utilizing multiple sidelink processes may be determined by any one or combination of: (pre)configuration; QoS of the data to be sent; CBR; the maximum number of available subchannels available in any symbol / timeslot within the selection period; the size of the data.

[0205] In one example, the WTRU is configured to perform resource selection for three MRFs with different N values ​​in the tuple (N, K), which are (5, 1), (2, 1), and (1, 1). First, the WTRU excludes occupied resources and selects X% of the total resources. Then, in the first stage of resource selection, the WTRU selects a resource for the transmission of 5TB. In one embodiment, if the first stage resource selection for one or more sidelink processes is unsuccessful, then in the second stage, the WTRU performs resource selection for the transmission of 2TB, and finally, the WTRU performs resource selection for 1TB.

[0206] An advantage of this embodiment is that it allows the WTRU to select several sidelink processes and therefore select different resource reservations that best meet the QoS requirements of the large packets to be transmitted, without requiring a large number of sidelink processes and without requiring a large amount of resources to be reserved in a given timeslot / symbol, and potentially leaving available resources for low latency WTRUs.

[0207] In one embodiment, the WTRU determines resources for a first transmission and may transmit continuously on the selected frequency resources for multiple transmissions.

[0208] The WTRU may follow the disclosed resource selection process (which may be used to determine the resources for one TB transmission) to determine the time and frequency resources for the first TB. By decoding the SCI and / or SCI_Notification, the WTRU may continuously transmit at the next transmission time in the resource pool to transmit the subsequent TBs, except for the time occupied / reserved by other WTRUs. The WTRU may avoid such occupied / reserved time by waiting for the reserved transmission to complete and resuming its transmission, or it may select another subband to transmit the remaining TBs.

[0209] Fig.10 1000 is a timing diagram showing an SCI indication regarding one or more consecutive transmissions at time 1002. The WTRU may be configured to transmit an SCI to indicate that it is performing consecutive data transmissions. In one embodiment, the WTRU may transmit one or more SCIs 1014-1018 over multiple time slots 1008-1012 to indicate the type of transmission (e.g., consecutive type versus non-consecutive type) and the start and end times of the consecutive transmissions. In one embodiment, the WTRU may transmit one SCI per transmission, where a prior SCI indicates information for one or more subsequent transmissions.

[0210] exist Fig.10 In the example shown, the WTRU may be configured to indicate the continuous transmission using option 1 1004 or option 2 1006. In option 1 1004, the WTRU transmits SCI 1014-1018 in each of the three time slots 1008-1012. The SCI in each previous time slot reserves resources for the subsequent time slot. In option 2 1006, the WTRU transmits one SCI 1020 in only one time slot 1008, which reserves resources for transmission in the three time slots 1008-1012.

[0211] The WTRU may be configured to perform resource reservation for periodic services of variable size. The WTRU may reserve resources with different priorities. In one embodiment, the WTRU may reserve resources for periodic services of variable size by indicating different priorities for each resource within the reserved resource group. Specifically, the WTRU may implicitly or explicitly indicate that it may reserve specific resources with different priorities, which may depend on the probability of using the resource. The priority of each resource may be indicated in the SCI or SCI_Notification. When the WTRU performs resource reservation for a packet with priority P, it may assign priority P to resources with a high probability of being used for the next transmission, and gradually reduce the priority to other resources with a lower probability of being used.

[0212] This embodiment may help the WTRU to reserve resources for packets of a certain size with data priority. As the packet size decreases, the WTRU may lower the MCS. As the packet size increases, if a reserved portion becomes unavailable, the WTRU may lower the MCS to support more data in one transmission. Alternatively, the WTRU may perform another resource selection to transmit the remaining data of the packet.

[0213] The SCI may be designed for multi-priority reservation of groups. To support the receiving WTRU during the sensing process, the WTRU may indicate the reservation information in its SCI. In one embodiment, the WTRU may indicate the location and priority of each resource group in one SCI. Optionally, the WTRU may transmit one SCI for a reserved resource with the same priority.

[0214] In one example, the WTRU may reserve resources for packets of size 190 or 300 bytes with priority P1. It may reserve one resource with 6 PRBs (for 190 bytes with priority P1) and another resource with 4 PRBs (with priority P2=P1+1). Alternatively, when the WTRU reserves resources for packets of size 800 or 1200 bytes with priority P1, it may reserve two transmissions for 800-byte packets with priority P1 and one transmission for 1200-byte packets with priority P2=P1+2.

[0215] The WTRU may reserve resources for periodic SCI_Notification transmissions. In one embodiment, the WTRU may reserve one or more SCI_Notification reservation procedures for periodic packets of variable size. The WTRU may then perform resource selection for PSSCH and / or PSCCH transmissions in the case of transmitting the SCI_Notification. The WTRU may then update the content of the SCI_Notification accordingly based on the result of the resource selection procedure. This embodiment may allow the WTRU to not have to perform resource selection for the SCI_Notification message(s).

[0216] The WTRU may reserve resources for periodic SCI_Notification transmissions and reserve one or more fixed resources for PSSCH and / or PSCCH transmissions. In one embodiment, the WTRU may reserve one or more SCI_Notification reservation procedures and the fixed resources for PSSCH and / or PSCCH transmissions. The amount of fixed resources may be determined based on an average packet size, or the amount of fixed resources may be determined based on a minimum packet size. When the packet arrives, the WTRU may perform resource selection or use the reserved resources based on the size of the packet and the reserved resources.

[0217] The WTRU may perform resource selection among multiple BWPs and multiple carriers. The WTRU may determine when to perform resource selection for multiple carriers or BWPs. The WTRU may determine resource selection for multiple carriers / BWPs when one or a combination of the following conditions are met: the buffer size is greater than a threshold, or the WTRU may decide to perform resource selection for multiple TBs simultaneously; Carrier Aggregation (CA) is configured for the WTRU; The WTRU is configured to have a specific application that requires the transmission of a large amount of data.

[0218] The WTRU may perform resource selection to minimize the half-duplex problem. The WTRU may select resources in multiple carriers or BWPs simultaneously. The WTRU may perform resource selection in multiple carriers / BWPs simultaneously to minimize the half-duplex problem, where when the WTRU receives / transmits in an adjacent carrier, it may not transmit / receive in other carriers. Specifically, when the WTRU has multiple TBs for transmission, it may determine to perform resource selection on N carriers / BWPs simultaneously. The WTRU may first determine available transmission moments that have resources for transmission in each of the multiple carriers. The WTRU may then randomly select one or more transmission moments to transmit in all N carriers / BWPs. When the number of available transmission moments is less than a threshold, the WTRU may reduce N to perform further resource selection.

[0219] The WTRU may sequentially select resources for multi-carrier / BWP transmissions. In one embodiment, the WTRU may perform resource selection for multiple TBs sequentially in each carrier / BWP. The WTRU may perform resource selection for one carrier / BWP as described. The WTRU may then perform resource selection for a second carrier / BWP to minimize half-duplex issues. The WTRU may prioritize transmission times that may be selected for transmissions by a first carrier.

[0220] In one embodiment, the WTRU may perform different resource allocation schemes for the initial transmission and the retransmission(s). Specifically, the WTRU may perform resource selection for the initial transmission by using any of the described procedures, which may be based on decoding SCI, SCI_Notification, CCA, backoff and / or preemption. For the retransmission(s), the WTRU may first exclude occupied resources, which may be determined by decoding SCI or SCI_Notification, preemption messages from other WTRUs. The frequency resources used for the retransmission(s) may be the same as the frequency resources for the initial transmission, or may be randomly selected in a resource pool. The time resources used for the retransmission(s) may be randomly selected, which may satisfy one or any of the following conditions: the time gap between the initial transmission and the first retransmission is within the range [1, X]; the time gap between two consecutive retransmissions is within [1, Y], where the values ​​(one or more) of X and Y may be configured, for example, preconfigured.

[0221] The WTRU may use the SCI or SCI_Notification of the initial transmission to reserve resources for retransmission(s). The WTRU may use the SCI or SCI_Notification of the initial transmission to reserve resources(s) for retransmission(s). Specifically, the WTRU may use the SCI or SCI_Notification of the initial transmission to implicitly / explicitly indicate one or any combination of the following information: number of retransmissions; time-frequency resources for retransmissions; time gaps between different transmissions; frequency hopping of the transmission of the TB.

[0222] In one embodiment, the WTRU may be pre-configured with the number of retransmissions and / or the time gap between different transmissions based on the QoS of the TB (e.g., reliability, priority, and / or latency). The receiver WTRU may use the QoS indicated in the SCI or SCI_Notification to determine the number of retransmissions and the time-frequency resources reserved for retransmissions by the initial transmission of the transmitter WTRU.

[0223] The WTRU may use SCI_Notification to reserve one or more resources for an initial transmission and / or retransmission(s) of a TB. Specifically, for an initial transmission, the WTRU may transmit one or more SCI_Notification messages prior to the transmission of the PSSCH and / or PSCCH, wherein the SCI_Notification messages may be used to reserve / indicate time-frequency resources for the initial transmission and / or retransmission(s). The WTRU may use the SCI of the initial transmission to reserve resources for the retransmission(s). For example, Fig.10 As shown in Option 1 1004 of the WTRU, the WTRU uses the SCI_Notification of the initial transmission to reserve time-frequency resources for the initial transmission and two retransmissions. In Option 2 1006, a single SCI 1020 may reserve time-frequency resources for data in multiple time slots 1008-1012 without sending subsequent SCIs.

[0224] A method for selecting one or more (pre)configured resources is disclosed herein. In one embodiment, the WTRU determines to perform sensing-based resource selection or non-sensing resource selection based on (pre)configuration and / or CBR measurement and / or resource reservation signal / message (e.g., by using an SCI_Notification message, a preemption message, or a resource reservation sequence).

[0225] In one embodiment, the WTRU may be (pre)configured with a set of resources for transmission. The WTRU may be instructed whether the (pre)configured resources are dedicated to the WTRU or shared between different WTRUs. In one embodiment, the WTRU may determine to perform sensorless resource selection by randomly selecting one or more transmission resources if any one or more of the following conditions are met: the (pre)configured resources are dedicated to the WTRU; the CBR measured in the resource pool is below a threshold; the number or size of resource reservation signals / messages (e.g., SCI_Notification message, preemption message, or resource reservation sequence) is below a threshold.

[0226] In one embodiment, the WTRU may determine to perform sensing-based resource selection if one or any combination of the following conditions is met: the (pre)configured resources are shared between different WTRUs; the CBR measured in the resource pool is greater than a threshold; the number of resource reservation signals / messages (e.g., SCI_Notification messages, preemption messages, resource reservation sequences) is greater than a threshold.

[0227] The threshold (e.g., CBR threshold, number of SCI_Notification messages, number of preemption messages, etc.) may be preconfigured for the WTRU or configured for the WTRU via RRC or SCI. The threshold may be determined based on the QoS of the packet (e.g., VQI, priority, latency, etc.).

[0228] The WTRU may determine a channel access scheme based on the QoS of the data. In one embodiment, the WTRU may be configured for different channel access methods based on the QoS of the packet (e.g., QoS determined via VQI, priority, latency, etc.). Specifically, if the priority and / or latency of the packet is high, the WTRU may determine to perform a random selection. Alternatively, the WTRU may determine to perform CCA only when the priority and / or latency of the packet is medium. Finally, if the priority and / or latency of the packet is low, the WTRU may need to perform CCA and backoff procedures. The priority and / or latency thresholds of packets that implement different channel access schemes may be (pre) configured or configured by the network via RRC or SIB.

[0229] Resource selection may be based on one or more patterns. In some embodiments, the WTRU may be configured to perform pattern-based transmissions. Specifically, pattern-based transmissions may be defined as transmissions that use one or more predefined time and possible frequency resources.

[0230] In one embodiment, the WTRU may be configured as a pattern pool, where each pattern may be defined in a window. The window may be repeated, which allows the pattern to be repeated. Within a pattern window, each pattern may be defined as a set of transmission periods and possible transmission frequencies within the pattern window. A transmission interval may consist of one or more time slots or may include one or more time slots.

[0231] Fig.11 1100 is a diagram illustrating a method used by a WTRU to use a first transmitted SCI_Notification to reserve resources for a retransmission. Fig.11In the example shown, the WTRU may transmit an SCI_Notification 1106 indicating resources for an initial transmission 1108. The SCI_Notification 1106 may also indicate resources for transmission of first control information 1110 and a first retransmission 1112. The SCI_Notification 1106 may also indicate resources for transmission of second control information 1114 and a first retransmission 1116. The SCI_Notification may indicate a time gap 1118 between the initial transmission 1108 and the end of the first retransmission 1112. Another time gap may be indicated between the end of the first retransmission 1112 and the end of the second retransmission 1116. Other gaps in time 1102 or frequency 1104 may additionally or alternatively be indicated.

[0232] The WTRU may be configured with a resource pool consisting of or including a 4-interval pattern window, where each pattern may be represented by 4 bits and each bit represents a transmission opportunity in that pattern in two time slots. The WTRU may be configured to use one of the possible pattern sets in Table 2. In each pattern, a bit set to 1 indicates a transmission interval and a bit set to 0 indicates a non-transmission interval.

[0233] Fig.12 is a diagram of an example pattern design 1200 demonstrating a 4-interval window resource pool. Fig.12 Three style windows 1206-1210 are shown in time 1202. Each interval 1212-1234 of each style window 1206-1210 may occupy 2 time slots. In other embodiments, other style(s) and style options may be applicable.

[0234] index style index style index style index style 1 1111 5 0111 9 0110 13 0100 2 1110 6 1100 10 0101 14 0010 3 1101 7 1010 11 0011 15 0001 4 1011 8 1001 12 1000

[0235] Table 2: Possible set of styles for 4-interval windows

[0236] The WTRU may determine the transmission pattern based on the QoS and / or CBR of the TBs of the resource pool. In one embodiment, the WTRU may determine the transmission pattern based on the CBR of the resource pool and / or the QoS of the TBs. Specifically, the WTRU may be configured with a table that indicates the minimum and maximum number of transmissions for a TB based on the QoS and / or the CBR of the resource pool. The WTRU may select one or more patterns with a number of transmissions within the configured range.

[0237] The WTRU may determine a set of patterns based on the QoS of the data to be transmitted. The WTRU may be (pre)configured with multiple pattern sets, where each pattern set may be associated with one or any combination of the following parameters: duration of a pattern window; duration of a transmission interval; number of transmission resources used for each pattern, e.g., the maximum and / or minimum number of (pre)configured transmission resources for a pattern in a resource pool; maximum / minimum time gap between transmissions in a pattern; size of frequency resources used for each transmission.

[0238] In one embodiment, the WTRU may determine a transmission resource pool based on the QoS of the TB. Specifically, the WTRU may determine one or any combination of the following parameters for transmitting a TB: the number of transmissions for the TB; the duration of a transmission of the TB; the frequency range of one or more transmissions; the total transmission time; and / or based on frequency hopping, such as based on the frequency hopping pattern or based on whether frequency hopping is used. Based on one or any combination of the mentioned transmission parameters, the WTRU may determine a set of patterns to meet the QoS requirements of the TB.

[0239] The WTRU may determine the set of available patterns based on the QoS of the TB and / or the resource allocation time. In some embodiments, the WTRU may determine the set of available patterns based on one or any combination of: the QoS of the TB, such as priority, reliability and / or latency; and / or the resource selection time compared to the pattern.

[0240] In one embodiment, the WTRU may determine a set of available patterns and / or a subset of one or more patterns based on the reliability of the TB. Based on the reliability of the TB, the WTRU may determine a minimum number of transmissions for the TB. The WTRU may then determine a set of patterns whose number of transmissions is greater than or equal to the minimum number of transmissions possible for the TB. This embodiment may be facilitated to allow the WTRU to select a transmission pattern that meets the reliability requirements of the TB. For example, for Fig.12 , the WTRU may need to select transmission resources for a TB that requires at least 2 transmissions. Therefore, the WTRU may determine a set of available patterns whose indices belong to the set {1,2,3,4,5,6,7,8,9,10,11}. The mapping of indices to patterns may be as described in Table 1.

[0241] In one embodiment, the WTRU may determine the set of available patterns based on the resource allocation time of the TB. Specifically, if the WTRU may need to perform resource selection in the middle of the pattern window, the WTRU may exclude patterns with transmission times before the resource selection time. For example, the WTRU may need to perform resource selection during the first interval and may need to select a pattern with at least two transmission intervals. The set of patterns with at least two transmission intervals may be {1,2,3,4,5,6,7,8,9,10,11}. The WTRU may exclude a set of patterns with transmissions in the first interval, such as {1,2,3,4,6,7,8,9}. Therefore, the set of available patterns is {5,9,10,11}.

[0242] The WTRU may determine a set of available patterns based on the priority of the TB. In one embodiment, the WTRU may be (pre)configured with a set of available patterns based on the priority of the TB. Specifically, each pattern may have an initial transmission interval, and the WTRU may be (pre)configured to select patterns with different initial transmission intervals based on the priority of the TB. For example, for a high priority TB, the WTRU may be allowed to select a pattern with an initial transmission in the first interval, while for a low priority TB, the pattern with an initial transmission in the second interval may be allowed to be selected. This embodiment may be driven to allow the WTRU to reduce the probability of conflict in selecting patterns with TBs with different priorities.

[0243] In one embodiment, the WTRU may determine to combine multiple styles in different style windows to transmit a TB. The WTRU may use the same or different style indexes in the style window to transmit a TB. The WTRU may perform style combining to meet the QoS of the TB. Specifically, if the WTRU cannot select a style in the style window to meet the QoS of the TB, the WTRU may perform style combining. The WTRU may indicate its transmission across multiple style windows in the SCI or SCI_Notification to support another WTRU sensing and decoding the message.

[0244] In one embodiment, the WTRU may indicate the use of a pattern or a pattern subset in an SCI or SCI_Notification. Specifically, the WTRU may implicitly or explicitly indicate one or any combination of the following information in the SCI and / or SCI_Notification: a pattern index, a frequency range used for one transmission; the number of transmission resources and a frequency hopping indication.

[0245] Fig.13 1300 is a timing diagram illustrating a WTRU determining the availability of a pattern based on decoding of an SCI or SCI_Notification 1312. Fig.13 , the x-axis represents time 1302 and the y-axis represents frequency 1304. Three subchannels 1306-1310 are shown in frequency 1304. The WTRU may determine the availability of a pattern, such as pattern 1011 1314 and pattern 1316 - and / or a group of patterns and / or a subset of patterns based on sensing. In one embodiment, the WTRU may determine the availability of a pattern and / or a group of patterns based on decoding an SCI and / or an SCI_Notification 1312. Specifically, if the WTRU may decode an SCI or SCI_Notification 1312 that reserves a transmission pattern and the RSSI / RSRP of the reserved resources is greater than a threshold, the WTRU may determine that the reserved pattern and a pattern having a transmission in one resource of the reserved pattern are occupied.

[0246] exist Fig.13 In the example shown, a WTRU may reserve transmission pattern 1011 1314 in subchannel 1 1310 by using SCI_Notification 1312, and a WTRU may reserve transmission pattern 0101 1316 in subchannel 3 1306 by using SCI. The WTRU determines pattern 1011 1314 in subchannel 1 1310 as occupied, and it may also determine that for subchannel 1 1310, all other patterns except pattern 0100 are occupied. Similarly, for subchannel 3 1306, all patterns except 1000, 0010, and 1010 are considered occupied. The WTRU may not receive any information about the availability of subchannel 2 1308 from SCI_Notification 1312. Alternatively, the absence of a bitmap may indicate that subchannel 2 1308 is available or unavailable. Patterns may be applied over a single pattern window, such as 1 pattern window 1318, 1320.

[0247] In one embodiment, the WTRU may determine the availability of a set of patterns by using CCA. Specifically, first the WTRU may determine the availability of a resource by using CCA. If the resource is considered to be occupied, the WTRU may determine a set of patterns that may use the occupied resource. For example, if the WTRU is configured with a 4-interval pattern window and the WTRU determines that the first interval is occupied, the WTRU may determine that all patterns with transmissions in the first interval are unavailable, that is, the WTRU may consider the pattern indexes 1, 2, 3, 4, 6, 7, 8, 12 described in Table 1 as occupied. The WTRU may use a counter to reset to the resources in the group to recover the previously occupied resources, otherwise the resources in the group are determined to be occupied.

[0248] Fig.14Schematic diagram 1400 is shown of a WTRU randomly selecting a style window in time 1402 and frequency 1404 for transmitting a TB. The WTRU may select a style with one or more windows to transmit the TB based on the QoS of the TB. In one embodiment, the WTRU may determine a resource selection window [T1, T2] including or excluding style windows 1406-1414 that may be able to meet the QoS of the TB. The WTRU may then determine a set of style windows to perform one or more style selections. The set of style windows may be selected within the resource selection window [T1, T2]. The WTRU may randomly select one or more style windows 1406-1414 within [T1, T2] to perform style selection. Fig.14 As shown, the WTRU may randomly select pattern window 1 1408, pattern window 2 1410, or pattern window 3 1412 to transmit a TB. Other selection methods besides random selection may be used.

[0249] In another embodiment, the WTRU may perform pattern selection and / or pattern window selection for transmission of one TB by decoding SCI and / or SCI_Notification and delaying transmission using a backoff counter. Specifically, the WTRU may perform the following steps to perform pattern window selection and / or pattern selection.

[0250] Initially, the WTRU may generate a backoff counter to determine whether the WTRU is able to select a style window and / or style for transmission. Specifically, if the backoff counter is less than or equal to zero, the WTRU is able to select a style window and / or style for transmission. Otherwise, the WTRU may not be able to select the style window and / or style. The value of the backoff counter may be randomly selected within the window [0, W], where the value of W may be (pre) configured or configured by the network via a SIB or RRC message. In an embodiment, transmission may be performed when the backoff counter may be lower than a value other than 0. Alternatively, the backoff counter may be incremented instead of decremented and may still be consistent with the embodiments of this document.

[0251] The WTRU may then determine the set of available patterns within the pattern window by decoding the SCI and / or SCI_Notification and / or by performing CCA. Specifically, the WTRU may exclude all patterns of transmission resources that potentially conflict with the pattern indicated by the SCI and / or SCI_Notification. It may also exclude resources or patterns that are determined to be occupied by performing CCA.

[0252] The WTRU may then reduce the backoff counter, where the reduction may be based on one or any combination of: QoS of the TB; number of available resources; number of available patterns; number of deferred pattern windows; radio activity of the resource pool / carrier / BWP, e.g., a determined CBR.

[0253] If the backoff counter is less than or equal to zero, the WTRU may randomly select an available pattern within the current pattern window, or randomly select an available pattern within the subsequent pattern window, for transmitting the TB. Otherwise, if the backoff counter is greater than zero, the WTRU waits until the next pattern window to perform SCI and / or SCI_Notification decoding or CCA.

[0254] In NR V2X, the WTRU may support periodic services of fixed and / or variable size. The network may require the WTRU to report the service information to support the network in scheduling.

[0255] The WTRU may report multiple packet sizes for variable-sized periodic services in the WTRU Assistance Information Element. In one embodiment, the WTRU may report different service information in the WTRU Assistance Information to inform the network of this feature. Specifically, if the upper layers indicate the presence of fixed-size periodic services, the WTRU may report the size of the packet. However, if the upper layers indicate the presence of variable-sized periodic services, the WTRU may report N packet sizes. The value of N may be determined based on one or any combination of: the range of packet sizes supported by the upper layers; and / or the QoS range of the service.

[0256] In one example, the WTRU may be configured with an SPS configuration that alternates between grant sizes reported by the WTRU assistance information or grant sizes that are related to the sizes reported in the SPS configuration. Specifically, the WTRU may assume that the grant sizes for contiguous resources of the SPS configuration match or are related to each reported size. The WTRU may also receive signaling in the SPS configuration about the pattern of different grant sizes within the SPS configuration. Alternatively, the WTRU may adopt a fixed pattern (one contiguous grant for each size) or may adopt the pattern to match the information provided in the WTRU assistance information.

[0257] The WTRU may be configured to have one or more grant sizes associated with an SPS configuration, which is explicitly located in the SPS configuration itself. Alternatively, the WTRU may derive the grant size based on a first grant size provided by the network. For example, the first grant size may be associated with a first requested grant size in the WTRU assistance information. Subsequent grant sizes may be determined based on the relationship between the requested grant sizes provided in the WTRU assistance information. If the WTRU requested X and 2X in the WTRU assistance information, and was granted Y in the SPS configuration, it may assume Y and 2Y as consecutive grant sizes for the SPS.

[0258] In one embodiment, the WTRU may implicitly or explicitly indicate the packet size of variable-sized periodic services in the SR. In one embodiment, the WTRU may be configured with a mapping of SR information bits to packet sizes. When the WTRU reports the SR, the WTRU may set the SR information bits to the corresponding packet size. In this way, a receiver that can decode the bit length can determine the packet size. Alternatively, the WTRU may be configured with different SR configurations, and each configuration may be associated with one or more packet sizes, for example using a range of sizes. Then, when the packet is available at the buffer, the WTRU may use the appropriate configuration to indicate the size of the packet.

[0259] Fig.15 1500 is a flow chart illustrating resource selection based on packet priority. In an embodiment, the WTRU may receive 1502 a resource pool configuration that provides the WTRU with one or more time intervals, time slots, bandwidth configurations, or reservation periods, etc. When the WTRU determines that a packet is buffered 1504 or received from a higher layer, the WTRU may check 1506 the packet priority. A CBR of the resources indicated by the resource pool may be determined 1508. Based on the packet priority or CBR, the WTRU may set 1510 a backoff counter to an initial backoff value. In an embodiment, the WTRU may use a lookup table to determine the backoff counter. The WTRU may then perform 1512 a CCA on one or more resource time slots. When the CCA indicates that resources are available, the backoff counter may be decremented 1514 by the number of available resources in each time slot. The WTRU may then determine 1516 whether the backoff counter is equal to or less than zero, and if the answer is yes 1518, the WTRU may randomly select 1522 a resource for transmission. If the answer is no 1520, the WTRU may proceed to perform 1512 the CCA.

[0260] Fig.161600 is a timing diagram illustrating a transmission process using a backoff counter. In a first time slot 1644 in time 1602, CCA may be performed along three subbands 1606-1610 in frequency 1604. In the first time slot 1644, subband 1606 may be busy due to forward reservation resources. Subband 1608 may be determined as an available channel access instance. Subband 1610 may be unavailable according to LBT. Therefore, 1 resource 1630 may be indicated as available, and the backoff value may be reduced from 3 1636 to 2 1638. In a second time slot 1646, subband 1612 may be busy due to forward reservation resources. Subband 1614 may be determined as an available channel access instance. Subband 1616 may be busy due to forward reservation resources. Therefore, 1 resource 1632 may be indicated as available, and the backoff value may be reduced from 2 1638 to 1 1640. In a third time slot 1648, subband 1618 may be available. Subband 1620 may be available. Subband 1622 may not be available. Thus, 2 resources 1634 may be indicated as available, and the backoff value may be decreased from 1 1640 to -1 1642. In a fourth time slot 1650, subband 1624 may be available. Subband 1626 may not be available. Subband 1628 may be selected for transmission.

[0261] Fig.17 1700 is a flow chart illustrating an example method for a WTRU to select resources for transmission. Based on a priority, a WTRU may be configured 1702 with multiple channel access moments in a time slot. The priority may be based on a data packet priority or another priority. The WTRU may determine 1704 available resources on which CCA may be performed based on sensing transmissions of other WTRUs. The WTRU may generate 1706 an initial backoff value based on the performance and / or priority of the CBR. At 1708, CCA may be performed in each available resource in the time slot. Whenever an available resource is determined in the time slot, the WTRU may reduce 1710 the backoff value accordingly, for example, the backoff value may reduce the number of available resources. When the backoff value is equal to or less than a threshold (e.g., 0) 1712, the WTRU may randomly select 1714 an available resource for transmission in a time slot. Until the backoff value reaches or exceeds the threshold, the WTRU may continue to perform 1708 CCA.

[0262] Although the features and elements are described above in specific combinations, it will be recognized by those skilled in the art that each feature or element can be used alone or in any combination with other features and elements. In addition, the methods described herein can 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, buffer memory, semiconductor memory devices, magnetic media (e.g., internal hard disks and removable disks), magneto-optical media, and optical media (e.g., CD-ROM disks and digital versatile disks (DVDs)). A processor associated with software can be used to implement a radio frequency transceiver for a WTRU, UE, terminal, base station, RNC, or any host computer.

Claims

1. A method performed by a wireless transmit / receive unit WTRU, the method comprising: Sending first side link control information SCI indicating one or more transmission resources; determining that: (1) based on receiving an SCI from another WTRU, the one or more transmission resources indicated by the first SCI overlap with one or more transmission resources associated with a higher priority reservation associated with the other WTRU, and (2) based on receiving the SCI from the other WTRU, a sidelink reference signal received power (SL-RSRP) measurement is greater than a SL-RSRP threshold; and Based on the determination, sending a second SCI, the second SCI indicating one or more different transmission resources, The SL-RSRP measurement is a measurement associated with resources reserved by the other WTRU.

2. The method according to claim 1, wherein the threshold is configured via a system information broadcast (SIB).

3. The method of claim 1, wherein the threshold is configured via radio resource control (RRC) signaling.

4. A wireless transmit / receive unit WTRU, the WTRU comprising: transmitter; as well as processor, wherein the transmitter and the processor are configured to: Sending first side link control information SCI indicating one or more transmission resources; determining: (1) based on receiving an SCI from another WTRU, whether the one or more transmission resources indicated by the first SCI overlap with one or more transmission resources associated with a higher priority reservation associated with the other WTRU, and (2) based on receiving the SCI from the other WTRU, determining that a sidelink reference signal received power (SL-RSRP) measurement is greater than an SL-RSRP threshold; and Based on the determination, sending a second SCI, the second SCI indicating one or more different transmission resources, The SL-RSRP measurement is a measurement associated with the resources reserved by the other WTRU.

5. The WTRU of claim 4, wherein the processor is further configured to select one or more different transmission resources.

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