NR v2x method for data transmission in wireless system

Abstract

The present invention relates to an NR V2X method for data transmission in a wireless system, and more particularly, to a method and an apparatus for selecting resources for transmission, the method being performed by a WTRU. The method may include determining a priority of data packets and determining a CBR of a resource pool. The WTRU may set a backoff counter to an initial backoff value according to at least one of the priority of the packet or the CBR. The CCA may be performed in a plurality of resource slots to determine whether the resource slots are available. The backoff counter may reduce the number of available resources in each slot. When the backoff counter reaches a threshold that may be set to zero, the resource for transmission may be randomly selected. The WTRU may then transmit data to another WTRU on the randomly selected resource.

Description

This application is a divisional application of Chinese Patent Application No. 201980058773.6, titled "NR V2X Method for Data Transmission in Wireless Systems", with a filing date of August 6, 2019. The content of the parent application is incorporated herein by reference. Cross - reference to related applications

[0001] 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 respective contents of which are incorporated herein by reference. Summary of the invention

[0002] A method and a wireless transmit / receive unit (WTRU) for selecting resources for transmission. The method may include: determining the priority of a data packet and determining the 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. Clear channel assessment (CCA) may be performed in multiple resource time slots to determine whether the resource time slots are available. The backoff counter may reduce the number of available resources in each time slot. When the backoff counter reaches a threshold that can be set to 0, the resources for transmission may be randomly selected. Then, the WTRU may transmit data to another WTRU on the randomly selected resources. Brief description of the drawings

[0003] Further, like reference numerals in the drawings denote like elements, and in which:

[0004] Figure 1A is a system diagram showing an exemplary communication system in which one or more disclosed embodiments may be implemented;

[0005] Figure 1B is a system diagram showing an exemplary wireless transmit / receive unit (WTRU) that may be used within the communication system shown in Figure 1A ;

[0006] Figure 1C is a system diagram showing an exemplary radio access network (RAN) and an exemplary core network (CN) that may be used within the communication system shown in Figure 1A ;

[0007] Figure 1D is a system diagram showing another exemplary RAN and another exemplary CN that can be used within the communication system shown in Figure 1A ;

[0008] Figure 2 is a diagram showing the channelization of time and frequency resources;

[0009] Figure 3 is a diagram showing an example option of a Clear Channel Assessment (CCA) configuration;

[0010] Figure 4 is an example of a resource selection process;

[0011] Figure 5 is a diagram showing the pool configuration of Sidelink Control Information (SCI) Notification (SCI_Notification);

[0012] Figure 6 is a timing diagram showing the channel access of one or more SCI_Notification messages having one or more different priorities;

[0013] Figure 7 is a diagram showing a WTRU randomly selecting four time - frequency resources to perform CCA for transmitting two SCI_Notification messages;

[0014] Figure 8 is a diagram showing options of SCI_Notification for notifying future Physical Sidelink Shared Channel (PSSCH) and / or Physical Sidelink Control Channel (PSCCH) transmission(s); and

[0015] Figure 9 is a diagram showing the calculation of Sidelink Received Signal Strength Indicator (S - RSSI) of candidate resources;

[0016] Figure 10 is a timing diagram showing an SCI indication regarding one or more consecutive transmissions following the indication;

[0017] Figure 11 is a diagram showing the method by which a WTRU uses the SCI_Notification of a first transmission to reserve resources for subsequent retransmissions;

[0018] Figure 12 is a diagram of an example pattern design;

[0019] Figure 13is a diagram showing that the WTRU determines the availability of a pattern based on decoding of an SCI or SCI_Notification;

[0020] Figure 14 is a diagram showing that the WTRU randomly selects a pattern window for multiple transmissions of a TB;

[0021] Figure 15 is a flowchart showing resource selection based on packet priority;

[0022] Figure 16 is a timing diagram showing a transmission process using a backoff counter; and

[0023] Figure 17 is a flowchart showing an example method by which the WTRU selects resources for transmission. An example network for implementation of the embodiments

[0024] Figure 1A is an illustration showing an exemplary communication system 100 in which the disclosed embodiments may be implemented. The communication system 100 may be a multi-access system that provides voice, data, video, messaging, broadcast, and other content for multiple wireless users. The communication system 100 may enable multiple wireless users to access such content by sharing system resources including wireless bandwidth. By way of 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 multicarrier (FBMC), among others.

[0025] As 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. However, it should be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network components. Each of the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. For example, any one 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 computer, 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, a medical device and application (such as remote surgery), an industrial device and application (such as a robot and / or other wireless devices operating in an industrial and / or automated processing chain environment), a consumer electronic device, and a device operating 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.

[0026] The communication system 100 may also include base stations 114a and / or base stations 114b. Each of the base stations 114a, 114b may be any type of device configured to facilitate access to one or more communication networks (such as the CN 106, the Internet 110, and / or other networks 112) by wirelessly interfacing with at least one of the WTRUs 102a, 102b, 102c, 102d in a wireless manner. For example, the base stations 114a, 114b may be a base transceiver station (BTS), a Node B, an evolved Node B (eNB), a home Node B, a home eNB, a next-generation Node B (such as, a g Node B (gNB)), a new radio (NR) Node B, a site controller, an access point (AP), and a wireless router, etc. Although each of the base stations 114a, 114b is described 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.

[0027] Base station 114a may be part of 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. Base station 114a and / or base station 114b may be configured to transmit and / or receive wireless signals on one or more carrier frequencies in a cell (not shown). These frequencies may be in licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide wireless service coverage for a relatively fixed or potentially time-varying specific geographical area. A cell may be further divided into cell sectors. For example, the cell associated with base station 114a may be divided into three sectors. Thus, in one embodiment, base station 114a may include three transceivers, that is, each transceiver corresponds to one sector of the cell. In an embodiment, 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 can be transmitted and / or received in a desired spatial direction.

[0028] Base stations 114a, 114b may communicate with one or more of WTRUs 102a, 102b, 102c, 102d via air interface 116, where the air interface may be any suitable wireless communication link (such as radio frequency (RF), microwave, centimeter wave, millimeter wave, infrared (IR), ultraviolet (UV), visible light, etc.). Air interface 116 may be established using any suitable radio access technology (RAT).

[0029] More specifically, as described herein, communication system 100 may be a multiple access system and may use one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, and SC-FDMA, etc. For example, base station 114a in RAN 104 and WTRUs 102a, 102b, 102c may implement a certain radio technology, such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), where the technology may use Wideband CDMA (WCDMA) to establish 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).

[0030] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a certain radio technology, such as evolved UMTS terrestrial radio access (E-UTRA), where the technology may use Long Term Evolution (LTE) and / or Advanced LTE (LTE-A) and / or Advanced LTA Pro (LTE-APro) to establish the air interface 116.

[0031] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a certain radio technology, such as NR radio access, where the radio technology may use NR to establish the air interface 116.

[0032] 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 the dual connectivity (DC) principle). Thus, the air interfaces used by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions to / from multiple types of base stations (e.g., eNBs and gNBs).

[0033] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement the following 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), etc.

[0034] Figure 1AThe base station 114b therein may be a wireless router, a home Node B, a home eNode B, or an access point, and may use any suitable RAT to facilitate wireless connections in a local area, such as a business premise, a residence, a vehicle, a campus, an industrial facility, an air corridor (e.g., for drones), and a road, etc. 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 pico cell or a femto cell by using a cellular-based RAT (such as WCDMA, CDMA 2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.). As Figure 1A 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.

[0035] The RAN 104 may communicate with the CN 106, where the CN 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, and mobility requirements, etc. The CN 106 may provide call control, accounting services, location-based services for mobile, prepaid calling, Internet connection, video distribution, etc., and / or may perform advanced security functions such as user authentication. Although not shown in Figure 1A it, it should be understood that the RAN 104 and / or the CN 106 may communicate directly or indirectly with other RANs that use the same RAT or a different RAT as the RAN 104. For example, in addition to being connected to the RAN 104 that uses the NR radio technology, the CN 106 may also communicate with other RANs (not shown) that use GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technologies.

[0036] CN 106 can also act as a gateway for the WTRU 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 interconnected computer network device system that uses common communication protocols (e.g., the Transmission Control Protocol (TCP), the User Datagram Protocol (UDP), and / or the Internet Protocol (IP) in the TCP / IP Internet protocol family). The network 112 may include wired and / or wireless communication networks owned and / or operated by other service providers. For example, the other network 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.

[0037] Some or all of the WTRU 102a, 102b, 102c, 102d in the communication system 100 may include multi-mode capabilities (e.g., the WTRU 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks over different wireless links). For example, Figure 1A the illustrated WTRU 102c may be configured to communicate with a base station 114a that may use a cellular-based radio technology, and with a base station 114b that may use IEEE 802 radio technology.

[0038] Figure 1B is a system diagram showing an exemplary WTRU 102. As Figure 1B shown, the WTRU 102 may include a processor 118, a transceiver 120, a transmit / receive component 122, a speaker / microphone 124, a keyboard 126, a display / touchpad 128, a non-removable memory 130, a removable memory 132, a power supply 134, a Global Positioning System (GPS) chipset 136, and / or other peripheral devices 138. It should be understood that the WTRU 102 may also include any sub-combination of the foregoing components while remaining compliant with the embodiments.

[0039] The processor 118 can be a general-purpose processor, a dedicated processor, a conventional processor, a digital signal processor (DSP), multiple 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), and a state machine, etc. The processor 118 can perform signal encoding, data processing, power control, input / output processing, and / or any other functions that enable the WTRU 102 to operate in a wireless environment. The processor 118 can be coupled to a transceiver 120, and the transceiver 120 can be coupled to a transmit / receive component 122. Although Figure 1B the processor 118 and the transceiver 120 are described as separate components, it should be understood that the processor 118 and the transceiver 120 can also be integrated in an electronic component or chip.

[0040] The transmit / receive component 122 can be configured to transmit or receive signals to or from a base station (such as base station 114a) via the air interface 116. For example, in one embodiment, the transmit / receive component 122 can be an antenna configured to transmit and / or receive RF signals. As an example, in an embodiment, the transmit / receive component 122 can be a radiator / detector configured to transmit and / or receive IR, UV, or visible light signals. In an embodiment, the transmit / receive component 122 can be configured to transmit and / or receive RF and optical signals. It should be understood that the transmit / receive component 122 can be configured to transmit and / or receive any combination of wireless signals.

[0041] Although in Figure 1B the transmit / receive component 122 is described as a single component, the WTRU 102 can include any number of transmit / receive components 122. More specifically, the WTRU 102 can use MIMO technology. Thus, in an embodiment, the WTRU 102 can include two or more transmit / receive components 122 (such as multiple antennas) that transmit and receive radio signals via the air interface 116.

[0042] The transceiver 120 can be configured to modulate the signals to be transmitted by the transmit / receive component 122, and to demodulate the signals received by the transmit / receive component 122. As described herein, the WTRU 102 can have multi-mode capabilities. Therefore, the transceiver 120 can include multiple transceivers that allow the WTRU 102 to communicate using multiple RATs (such as NR and IEEE 802.11).

[0043] The processor 118 of the WTRU 102 may be coupled to a speaker / microphone 124, a keyboard 126, and / or a display / touchpad 128 (such as 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 any suitable memory such as a non-removable memory 130 and / or a removable memory 132, and store information in these memories. The non-removable memory 130 may include random access memory (RAM), 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 so on. In other embodiments, the processor 118 may access information from memories that are not actually located in the WTRU 102, and store data in these memories. As an example, such memories may be located in a server or a home computer (not shown).

[0044] The processor 118 may receive power from a power source 134 and may be configured to distribute and / or control power for 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 battery packs (such as nickel cadmium (Ni-Cd), nickel zinc (Ni-Zn), nickel metal hydride (NiMH), lithium ion (Li-ion), etc.), solar cells, and fuel cells, and so on.

[0045] The processor 118 may also be coupled to a GPS chipset 136, which may be configured to provide location information (such as longitude and latitude) related to the current location of the WTRU 102. As a supplement or replacement to the information from the GPS chipset 136, the WTRU 102 may receive location information from a base station (such as base stations 114a, 114b) via an air interface 116, and / or determine its location based on the signal timing received from two or more nearby base stations. It should be understood that the WTRU 102 may obtain location information by means of any suitable positioning method while remaining compliant with the embodiments.

[0046] The processor 118 may also be coupled to other peripheral devices 138, where the peripheral devices may include one or more software and / or hardware modules that provide additional features, functions, and / or wired or wireless connections. For example, the peripheral devices 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos and / or videos), 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 peripheral device 138 may include one or more sensors. The sensors may be one or more of the following: gyroscopes, accelerometers, Hall effect sensors, magnetometers, orientation sensors, proximity sensors, temperature sensors, time sensors, geographical location sensors, altimeters, light sensors, touch sensors, magnetometers, barometers, gesture sensors, biometric sensors, and humidity sensors, etc.

[0047] The WTRU 102 may include a full-duplex radio device, where for this radio device, the 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. The full-duplex radio device may include an interference management unit that reduces and / or substantially eliminates self-interference by means of hardware (e.g., choke coils) or by signal processing of 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 device 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)).

[0048] Figure 1C is a system diagram showing the RAN 104 and the CN 106 according to an embodiment. As described herein, the RAN 104 may communicate with the WTRU 102a, 102b, 102c using E-UTRA radio technology over the air interface 116. The RAN 104 may also communicate with the CN 106.

[0049] The RAN 104 may include eNodeBs 160a, 160b, 160c. However, it should be understood that the RAN 104 may include any number of eNodeBs while remaining compliant with the embodiment. Each eNodeB 160a, 160b, 160c may include one or more transceivers for communicating with the WTRU 102a, 102b, 102c over the air interface 116. In one embodiment, the eNodeBs 160a, 160b, 160c may implement MIMO technology. Thus, for example, the eNodeB 160a may use multiple antennas to transmit wireless signals to the WTRU 102a and / or receive wireless signals from the WTRU 102a.

[0050] Each eNode B 160a, 160b, 160c can be associated with a specific cell (not shown) and can be configured to handle radio resource management decisions, handover decisions, user scheduling in UL and / or DL, etc. As Figure 1C shown, eNode Bs 160a, 160b, 160c can communicate with each other via the X2 interface.

[0051] Figure 1C The CN 106 shown can include a Mobility Management Entity (MME) 162, a Serving Gateway (SGW) 164, and a Packet Data Network (PDN) Gateway (PGW) 166. Although the foregoing components are all described as being part of the CN 106, it should be understood that any one of these components can be owned and / or operated by an entity other than the CN operator.

[0052] The MME 162 can be connected to each eNode B 160a, 160b, 160c in the RAN 104 via the S1 interface and can act as a control node. For example, the MME 142 can be responsible for authenticating users of the WTRU 102a, 102b, 102c, performing bearer activation / deactivation procedures, and selecting a specific serving gateway during the initial attachment process of the WTRU 102a, 102b, 102c, etc. The MME 162 can also provide a control plane function for handover between the RAN 104 and other RANs (not shown) using other radio technologies (such as GSM and / or WCDMA).

[0053] The SGW 164 can be connected to each eNode B 160a, 160b, 160c in the RAN 104 via the S1 interface. The SGW 164 can generally route and forward user data packets to / from the WTRU 102a, 102b, 102c. Also, the SGW 164 can perform other functions, such as anchoring the user plane during handover between eNBs, triggering paging procedures when DL data is available for the WTRU 102a, 102b, 102c, and managing and storing the context of the WTRU 102a, 102b, 102c, etc.

[0054] The SGW 164 can be connected to the PGW 166, which can provide access to a packet switched network (such as the Internet 110) for the WTRU 102a, 102b, 102c to facilitate communication between the WTRU 102a, 102b, 102c and IP-enabled devices.

[0055] CN 106 can facilitate communication with other networks. For example, CN 106 can provide the WTRUs 102a, 102b, 102c with access to a circuit-switched network (e.g., the PSTN 108) in order to facilitate communication between the WTRUs 102a, 102b, 102c and traditional landline communication devices. For example, CN 106 can include or communicate with an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server), and the IP gateway can act as an interface between CN 106 and the PSTN 108. In addition, CN 106 can provide the WTRUs 102a, 102b, 102c with access to other networks 112, where the network can include other wired and / or wireless networks owned and / or operated by other service providers.

[0056] While the WTRU is described in Figure 1A - 1D as a wireless terminal, it should be appreciated that in some exemplary embodiments, such a terminal may use a (e.g., temporary or permanent) wired communication interface with the communication network.

[0057] In an exemplary embodiment, the other network 112 may be a WLAN.

[0058] A WLAN operating in 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 be connected to or interfaced with a Distribution System (DS) or some other type of wired / wireless network that delivers traffic into and / or out of the BSS. Traffic originating outside the BSS and destined for an STA may reach and be delivered to the STA through the AP. Traffic originating from an STA and destined for a destination outside the BSS may be sent to the AP for delivery to the corresponding destination. Traffic between STAs within the BSS may be sent through the AP, e.g., the source STA may send traffic to the AP and the AP may deliver the traffic to the destination STA. Traffic between STAs within the BSS may be considered and / or referred to as end-to-end traffic. The end-to-end traffic may be sent using a Direct Link Setup (DLS) between the source and destination STAs (e.g., directly between them). In some exemplary embodiments, the DLS may use 802.11e DLS or 802.11z Channelized DLS (TDLS). A WLAN operating in an Independent BSS (IBSS) mode may not have an AP, and STAs within or using the IBSS (e.g., all STAs) may communicate directly with each other. Here, the IBSS communication mode may sometimes also be referred to as an "ad hoc" communication mode.

[0059] When operating in the 802.11ac infrastructure mode or a similar mode, the AP can transmit beacons on a fixed channel (e.g., the primary channel). The primary channel can have a fixed width (e.g., a bandwidth of 20 MHz) or a dynamically set width. The primary channel can be the operating channel of the BSS and can be used by the STA to establish a connection with the AP. In some exemplary embodiments, Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) (e.g., in the 802.11 system) can be implemented. For CSMA / CA, STAs including the AP (e.g., each STA) can sense the primary channel. If a particular STA senses / detects and / or determines that the primary channel is busy, then the particular STA can back off. In a specified BSS, at any given time, there can be one STA (e.g., only one station) transmitting.

[0060] High Throughput (HT) STAs can use a channel with a width of 40 MHz for communication (e.g., by combining a 20 MHz primary channel with an adjacent or non - adjacent 20 MHz channel to form a 40 MHz channel).

[0061] Very High Throughput (VHT) STAs can support channels with widths of 20 MHz, 40 MHz, 80 MHz, and / or 160 MHz. 40 MHz and / or 80 MHz channels can be formed by combining consecutive 20 MHz channels. A 160 MHz channel can be formed by combining eight consecutive 20 MHz channels or by combining two non - consecutive 80 MHz channels (such a combination can be referred to as an 80 + 80 configuration). For the 80 + 80 configuration, after channel coding, the data can be passed and go through a segmentation parser, which can split the data into two streams. On each stream, inverse Fast Fourier Transform (IFFT) processing and time - domain processing can be performed separately. The streams can be mapped on two 80 MHz channels, and the data can be transmitted by the STA performing the transmission. On the receiver of the STA performing the reception, the above operations for the 80 + 80 configuration can be reversed, and the combined data can be sent to the Media Access Control (MAC).

[0062] 802.11af and 802.11ah support operation modes below 1 GHz. Compared with 802.11n and 802.11ac, the channel operating bandwidth and carriers used in 802.11af and 802.11ah are reduced. 802.11af supports 5 MHz, 10 MHz, and 20 MHz bandwidths in the TV white space (TVWS) spectrum, and 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. According to some exemplary embodiments, 802.11ah may support meter type control / machine type communication (MTC) (e.g., MTC devices in a macro coverage area). MTC may have certain capabilities, such as limited capabilities including support for (e.g., only support for) certain and / or limited bandwidths. MTC devices may include a battery, and the battery life of the battery is higher than a threshold (e.g., for maintaining a long battery life).

[0063] For a WLAN system (e.g., 802.11n, 802.11ac, 802.11af, and 802.11ah) that can support multiple channels and channel bandwidths, the WLAN system includes a channel that can be designated as a primary channel. The bandwidth of the primary channel may be equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be set and / or restricted by a certain STA, where the STA is sourced from all STAs operating in the BSS that support the minimum bandwidth operating mode. In an example regarding 802.11ah, even if the AP and other STAs in the BSS support 2 MHz, 4 MHz, 8 MHz, 16 MHz, and / or other channel bandwidth operating modes, for an STA that supports (e.g., only supports) the 1 MHz mode (e.g., an MTC type device), the width of the primary channel may be 1 MHz. Carrier sensing and / or network allocation vector (NAV) setting may depend on the state of the primary channel. If the primary channel is busy (e.g., because an STA (which only supports the 1 MHz operating mode) is transmitting to the AP), then all available bands may be considered busy even if most of the available bands remain idle.

[0064] In the United States, the available band for 802.11ah is 902 MHz to 928 MHz. In Korea, the available band is 917.5 MHz to 923.5 MHz. In Japan, the available band is 916.5 MHz to 927.5 MHz. Depending on the country code, the total bandwidth available for 802.11ah is 6 MHz to 26 MHz.

[0065] Figure 1DFIG. 0 is a system diagram showing RAN 104 and CN 106 according to an embodiment. As described above, RAN 104 may communicate with WTRUs 102a, 102b, 102c using NR radio technology over air interface 116. RAN 104 may also communicate with CN 106.

[0066] RAN 104 may include gNBs 180a, 180b, 180c, but it should be understood that RAN 104 may include any number of gNBs while remaining compliant with the embodiment. Each gNB 180a, 180b, 180c may include one or more transceivers to communicate with WTRUs 102a, 102b, 102c over air interface 116. In one embodiment, gNBs 180a, 180b, 180c may implement MIMO technology. For example, gNBs 180a, 180b may use beamforming processing to transmit and / or receive signals to and / or from gNBs 180a, 180b, 180c. Thus, for example, gNB 180a may use multiple antennas to transmit wireless signals to WTRU 102a and / or receive wireless signals from WTRU 102a. In an embodiment, gNBs 180a, 180b, 180c may implement carrier aggregation technology. For example, gNB 180a may transmit multiple component carriers to WTRU 102a (not shown). A subset of these component carriers may be on unlicensed spectrum while the remaining component carriers may be on licensed spectrum. In an embodiment, gNBs 180a, 180b, 180c may implement coordinated multi-point (CoMP) technology. For example, WTRU 102a may receive a coordinated transmission from gNB 180a and gNB 180b (and / or gNB 180c).

[0067] WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using transmissions associated with scalable numerology. For example, the OFDM symbol interval and / or the OFDM subcarrier interval may be different for different transmissions, different cells, and / or different portions of the radio transmission spectrum. WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using subframes or transmission time intervals (TTIs) having different or scalable lengths (e.g., containing different numbers of OFDM symbols and / or having an absolute time length that varies continuously).

[0068] gNBs 180a, 180b, 180c can be configured to communicate with WTRUs 102a, 102b, 102c operating in a stand-alone configuration and / or a non-stand-alone configuration. In the stand-alone configuration, WTRUs 102a, 102b, 102c can communicate with gNBs 180a, 180b, 180c without accessing other RANs (such as eNodeBs 160a, 160b, 160c). In the stand-alone configuration, WTRUs 102a, 102b, 102c can use one or more of gNBs 180a, 180b, 180c as a mobile anchor. In the stand-alone configuration, WTRUs 102a, 102b, 102c can use signals in the unlicensed band to communicate with gNBs 180a, 180b, 180c. In the non-stand-alone configuration, WTRUs 102a, 102b, 102c communicate / connect with gNBs 180a, 180b, 180c while communicating / connecting with other RANs (such as eNodeBs 160a, 160b, 160c). For example, WTRUs 102a, 102b, 102c can communicate with one or more gNBs 180a, 180b, 180c and one or more eNodeBs 160a, 160b, 160c in a substantially simultaneous manner by implementing the DC principle. In the non-stand-alone configuration, eNodeBs 160a, 160b, 160c can act as the mobile anchor for WTRUs 102a, 102b, 102c, and gNBs 180a, 180b, 180c can provide additional coverage and / or throughput to serve WTRUs 102a, 102b, 102c.

[0069] Each gNB 180a, 180b, 180c can be associated with a specific cell (not shown) and can be configured to handle radio resource management decisions, handover decisions, user scheduling in UL and / or DL, support network slicing, DC, implement interworking procedures 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. As Figure 1D shown, gNBs 180a, 180b, 180c can communicate with each other via the X2 interface.

[0070] Figure 1DThe illustrated CN 106 may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one session management function (SMF) 183a, 183b, and may possibly include data networks (DN) 185a, 185b. Although the foregoing components have all been described as part of CN 106, it should be understood that any of these components may be owned and / or operated by entities other than the CN operator.

[0071] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 104 via the N2 interface and may act as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRU 102a, 102b, 102c, supporting network slicing (e.g., handling different protocol data unit (PDU) sessions with different requirements), selecting a particular SMF 183a, 183b, managing the registration area, terminating non-access stratum (NAS) signaling, and mobility management, among other things. The AMF 182a, 182b may use network slicing processing in order to customize the CN support provided to the WTRU 102a, 102b, 102c based on the type of service used by the WTRU 102a, 102b, 102c. For example, different network slices may be established for different usage scenarios such as services that rely on ultra-reliable low latency (URLLC) access, services that rely on enhanced massive mobile broadband (eMBB) access, and services for machine type communication (MTC) access, among others. The AMF 182a, 182b may provide control plane functions for handover between the RAN 104 and other RANs (not shown) that use other radio technologies such as LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies such as WiFi.

[0072] 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 traffic 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 enforcement and QoS, and providing DL data notifications, among others. The PDU session types may be IP-based, non-IP-based, and Ethernet-based, among others.

[0073] UPF 184a and 184b can be connected to one or more gNBs 180a, 180b, 180c in RAN 104 via the N3 interface, which can provide the WTRUs 102a, 102b, 102c with access to a packet switched network (such as the Internet 110) to facilitate communication between the WTRUs 102a, 102b, 102c and IP-enabled devices. UPF 184, 184b can perform other functions such as routing and forwarding packets, enforcing user plane policies, supporting multi-homed PDU sessions, handling user plane QoS, buffering DL packets, and providing mobility anchoring handling, etc.

[0074] CN 106 can facilitate communication with other networks. For example, CN 106 can include or can communicate with an IP gateway (such as an IP Multimedia Subsystem (IMS) server) that serves as an interface between CN 106 and the PSTN 108. In addition, CN 106 can provide the WTRUs 102a, 102b, 102c with access to other networks 112, which can include other wired and / or wireless networks owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c can be connected to the local DNs 185a, 185b via the N3 interface to the UPFs 184a, 184b and the N6 interface between the UPFs 184a, 184b and the DNs 185a, 185b and through the UPFs 184a, 184b.

[0075] In view of Figure 1A - 1D and with respect to Figure 1A - 1D the corresponding descriptions, one or more or all of the functions described below can be performed by one or more emulation devices (not shown): WTRUs 102a-d, base stations 114a-b, eNode Bs 160a-c, MME 162, SGW 164, PGW 166, gNBs 180a-c, AMFs 182a-b, UPFs 184a-b, SMFs 183a-b, DNs 185a-b and / or any other device(s) described herein. These emulation devices can be one or more devices configured to emulate one or more or all of the functions herein. For example, these emulation devices can be used to test other devices and / or simulate network and / or WTRU functions.

[0076] The simulation device can be designed to perform one or more tests on 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, in whole or in part, as part of a wired and / or wireless communication network, in order to test other devices within the communication network. The one or more simulation devices 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 tests, and / or can use over-the-air wireless communication to perform tests.

[0077] 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 laboratory and / or a test scenario of a wired and / or wireless communication network that is not deployed (e.g., for testing), in order to perform 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 via an RF circuit (as an example, the circuit can include one or more antennas). Detailed implementation

[0078] The V2X feature of LTE provides support for basic security services. Generally, there are two supported service types: periodic services and event-triggered services. According to one service model, periodic and aperiodic services are generated as follows. For periodic services, a 300-byte message is followed by four 190-byte messages. In addition, the arrival interval time between two packets is a multiple of 100 ms. For event-triggered services, when an event is triggered after a Poisson process, 6 messages are generated at a period of 100 ms. According to the above service model of LTE V2X, generally, both event-triggered services and periodic services can be considered periodic services.

[0079] The sensing and resource selection of LTE V2X can be performed by the WTRU before transmitting 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 can decode the following information: the frequency and time of the forward booking PSSCH; the priority of the PSSCH; the frequency and time of PSSCH retransmissions.

[0080] 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) of the PSSCH of the WTRU (RSRP_PSSCH) is greater than a threshold, the WTRU may consider the forward reservation PSSCH as occupied and exclude it from resource selection. Then, the WTRU arranges the remaining resources in ascending order of the received signal strength indicator (RSSI) and may select 20% of the total resources as the final resource selection, as shown in set SA. Finally, a resource is randomly selected from SA for transmission.

[0081] 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, the model 2 aperiodic service supports the following attributes: a packet size range between 10000 and 30000 bytes; an average arrival interval rate of 20 ms; and a latency requirement of 10 ms. In addition, the mode 3 periodic service has the following attributes: a packet size range between 30000 and 60000 bytes; an average arrival interval rate of 30 ms; and a latency requirement of 30 ms.

[0082] For NR V2X, the aperiodic service is considered an important service model required in the state-of-the-art scenarios. For service model 2, the WTRU may need to perform resource selection very frequently, for example, once every 20 ms on average. If the WTRU follows the same resource selection process as LTE V2X, resource conflicts will occur very frequently because the probability of multiple WTRUs performing resource selection simultaneously will increase.

[0083] In one embodiment, the WTRU may perform resource selection for burst services without increasing the risk of resource conflicts.

[0084] Resource selection in LTE V2X allocates resources for a single transmission block. For the model 2 aperiodic service and the model 3 periodic service, NR V2X aims to support very large packet sizes, for example, up to 60000 bytes for periodic services and up to 30000 bytes for aperiodic services. Therefore, performing resource selection for an application layer packet may require segmenting the packet and performing resource selection multiple times for each transmission 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.

[0085] Figure 2 FIG. 200 illustrates the 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 of channelization. As shown, one or more resource pools may be channelized. In the frequency domain 202, 1 subchannel may consist of N sub consecutive PRBs or may include N sub consecutive PRBs. For example, each subchannel may have 2 PRBs. Each subchannel may be orthogonal in the frequency domain. 1 subband may consist of N subchannels or may include N subchannels. Each subband may be frequency-overlapped or non-overlapped, and each subband may or may not have the same number of subchannels. One transmission may occupy one subband in the frequency domain.

[0086] In the time domain 204, the transmission instant may be determined based on two factors: the duration of the transmission and whether the transmission is slot-based or non-slot-based. For slot-based transmissions, one transmission may span N slots. For non-slot-based transmissions, one transmission may span N≤14 symbols. The initial transmission may be at the start of the slot, in the second half of the slot, or at any symbol of the slot.

[0087] In Figure 2 the example shown, three different exemplary subband configurations 206-210 are shown. In the illustration of the N-subchannel subband 206, each subchannel includes 2 PRBs. Each of the four PRBs corresponds to one of two channels separated in frequency. For simplicity, a variable number of additional subchannels are not shown. In the example of the 2-subchannel subband 208, there are 4 PRBs. In the example of the 1-subchannel subband 210, two PRBs are shown.

[0088] The pool indication 212 may be provided as a bitmap that represents the pool as "on" via a (1) bit or as "off" via a (0) bit. The pool indication may be made via RRC, MAC, or PHY signaling.

[0089] In the example shown, the first two bits 214, 216 are "on", so there are transmission time instances available for transmission in the time domain. The WTRU can determine, based on this bitmap, whether a transmission moment is available on one or more of the subbands 206 - 210. For example, the WTRU can determine that the 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 can determine that the two-slot transmission time instance 242 is available on the 2-subchannel subband 208. The WTRU can determine that only 2 symbols 244 are available in the 1-subchannel subband 210. The WTRU can enter a sleep state during the next two time slots based on determining that bits 218, 220 are set to "off".

[0090] The WTRU can wake up when it determines that the next four bits 222 - 228 are set to "on". For example, the WTRU can determine that a full time slot 246 is available on the N-channel 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. No transmission is available during the time period corresponding to the pool bits 222, 224. During the time interval corresponding to the pool bit 228, a 4-symbol transmission moment 252 may be available on the N-channel 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. The WTRU can sleep during the time period corresponding to bit 230.

[0091] During the time periods corresponding to the pool bits 232, 234, the WTRU may have no availability 258 in the N-channel subband. The WTRU can have an 8-symbol transmission time instance 260 in the 2-subchannel subband 208. The WTRU can have a two-slot transmission time instance 262 in the 1-subchannel subband 210. Any number of symbols or time slots can be configured as a transmission moment.

[0092] Resource selection can be performed for one or more TB transmissions of periodic and aperiodic packets. In one embodiment, a resource group may be defined as a set of N subchannels spanning M symbols. A resource group format (RGF) may be defined as a tuple (M, N). In one implementation, the high-level procedure for a 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 requirement 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.

[0093] The WTRU may determine the minimum value of M to support sensing. In one implementation, the WTRU may be (pre)-configured with a range of M, e.g., the minimum and maximum transmission durations that support the CCA process and reduce the half-duplex problem. Specifically, the WTRU may be configured for the range of M based on one or more of the following: the QoS of the MAC PDU, such as the vehicle quality indicator (VQI), priority, latency, reliability, etc.; the congestion level of the resource pool, such as CBR; the size of the MAC PDU; the packet size and / or buffer size and / or traffic pattern.

[0094] The clear channel assessment (CCA) process may involve considering multiple options. The WTRU may be configured with the following parameters to perform CCA: the bandwidth of an evaluated channel; the number of evaluated channels; the duration of evaluating the channels; the start time of the evaluation; the end time of the evaluation; the energy / power threshold (RSRP, received signal code power (RSCP), SINR or SNR) for determining the availability of the evaluated 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 idle.

[0095] Figure 3 is a diagram showing three options 300, 330, 370 for clear channel assessment (CCA) configuration. The options for the bandwidth and the number of evaluated channels for CCA are described in Figure 3 where the WTRU performs CCA in a bandwidth of 100 MHz.

[0096] In option 1 300, the x-axis represents time 302 and the y-axis represents frequency 304. In one example, the WTRU can 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 can divide the bandwidth into 5 channels or sub-bands 336 - 344, each 20 MHz, and can 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 can perform CCA 366 - 380 in each PRB 382 - 396 and can individually determine the availability of each PRB 382 - 396.

[0097] In one embodiment, the WTRU can be configured to perform operations such as transmitting or receiving based on broadband energy measurements (e.g., RSSI). The WTRU can perform such measurements based on the automatic gain control (AGC) output without performing baseband processing.

[0098] In another embodiment, the WTRU can perform RSRP, RSCP, SINR, or SNR measurements. The WTRU can perform FFT and subcarrier demapping in order to obtain energy measurement results with a finer granularity (e.g., per resource block group (RBG), physical resource block (PRB), or subcarrier).

[0099] The WTRU can determine the availability of an RGF based on the result of the CCA process. In one implementation, if the CCA process indicates that at least one channel overlapping with the RGF is unavailable, the WTRU can determine that the RGF is unavailable. In another embodiment, if at least X% of the PRBs in the RGF are indicated as unavailable during the CCA process, the WTRU can determine that the RGF is unavailable. X can be pre-configured or can be provided in WTRU-specific or group-specific signaling.

[0100] In a set of embodiments, the WTRU can determine the CCA parameters based on the size and / or QoS of the MAC PDU. Specifically, the CCA parameters can be dynamically changed based on the size, latency, and / or QoS of the MAC PDU.

[0101] In one embodiment, the WTRU can determine the bandwidth of an evaluated channel based on the resource size of the MAC PDU. This embodiment can 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 can determine that the bandwidth of the evaluated channel is 10 or 20 PRBs.

[0102] 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 (such as VQI, priority, or latency, etc.). This embodiment may prioritize packets with different priority, reliability, or latency requirements. For example, the WTRU may be configured to have a difference of x decibels (xdB) between packets with successive priorities.

[0103] In another embodiment, the WTRU may determine the channel access moment based on the priority or latency of the MAC PDU. In one embodiment, the WTRU may be configured for a higher channel access moment density for high-priority or latency-required data, and this higher channel access moment density indicates the number of channel access moments in a period. In another embodiment, the WTRU may be configured to have different channel access times for different MAC PDUs with different priority or latency requirements. For example, for high-priority or latency-required data, the WTRU may be configured with faster channel access symbols / slots in a time slot or subframe than others. This embodiment can be utilized such that high-priority data can receive access to the channel faster than low-priority data. Therefore, when performing CCA, low-priority channels can avoid high-priority data.

[0104] In another embodiment, the WTRU may determine the duration of the reservation signal based on the priority or latency 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 the low-priority PDU can be transmitted.

[0105] 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 a set of embodiments, the WTRU may perform resource selection through 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, then by decoding the SCI of other WTRUs, the WTRU may exclude the resources reserved by other WTRUs. Process 2: The WTRU may select a subband, resource, channel, RGF, or transmission moment, etc., for the evaluation of possible transmission and / or CCA. Process 3: The WTRU may perform an idle channel assessment (CCA) before transmitting a TB.

[0106] The WTRU may perform procedure 2, which determines subbands, resources, RGFs, or transmission instances for possible transmission and / or CCA. In one method, the WTRU may be configured to select a subband having one or any combination of the following attributes for possible transmission and / or CCA. The WTRU may select a subband having the highest number of available resources for possible transmission within a resource selection window. The WTRU may select a subband having the longest continuous available resources within the resource selection window. The WTRU may select a subband having the earliest available resources within the resource selection window. The WTRU may select a subband having N continuous available resources within the resource selection window. The WTRU may be configured to randomly select one that meets the above constraints from among multiple subbands. Alternatively or in combination, the WTRU may be configured to select a subband having 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.

[0107] In one method, the WTRU may be configured to select a transmission instance for possible transmission and / or CCA based on one or both of the following: the earliest transmission instance having at least one available resource or subband within a resource selection window; or a transmission instance having at least N available resources / subbands. The WTRU may be configured to randomly select a transmission instance that meets the above constraints, or alternatively, the WTRU may be configured to select the earliest transmission instance that meets 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.

[0108] In one embodiment, the WTRU may be configured to perform measurements using a wideband energy measurement method (e.g., RSSI). The WTRU may perform such measurements based on the automatic gain control (AGC) output without performing baseband processing.

[0109] In another embodiment, the WTRU may perform RSRP, RSCP, SINR, or SNR measurements. The WTRU may perform FFT and subcarrier demapping in order to obtain energy measurement results with a finer granularity (e.g., per RBG, PRB, or subcarrier).

[0110] The combination of the above processes can avoid resource conflicts in different scenarios. Process 1 can avoid resources being reserved by other WTRUs for periodic services in advance. Process 2 can randomize resource conflicts among WTRUs performing dynamic resource selection for a TB transmission. Process 3 can mitigate resource conflicts associated with consecutive transmissions of multiple TBs by a WTRU.

[0111] Before the CCA process, the WTRU can perform Process 1 to further exclude reserved resources by decoding the SCI between two CCA instants. The WTRU can decode any resource reservation signal / message, such as an SCI_Notification message, a preemption message, a resource reservation sequence, etc., to exclude the reserved resources in the future.

[0112] In one embodiment, the WTRU can combine the three processes to perform resource selection as follows. Initially, the WTRU can perform Process 1. Similar to LTE V2X, the WTRU can exclude resources with measured power / energy greater than a threshold and indicated as occupied by other WTRUs in an SCI. The WTRU can select M% of the total resources in the resource selection window as the set of available resources for selection according to specific criteria such as received power, RSSI, etc.

[0113] After completing Process 1, the WTRU can follow the following method. In the first method, the WTRU can perform Process 2 by selecting a subband, one or more resources, one or more RGFs, or one or more transmission instants for possible transmission from the set of available resources in Process 1. After Process 2, the WTRU can perform Process 3, which determines whether the selected subband, resource, RGF, transmission instant is available. If the subband, resource, RGF, transmission instant is idle, the WTRU can transmit the packet in the selected subband, resource, RGF, or transmission instant. Otherwise, if the channel is busy, the WTRU can wait until the channel becomes available and transmit the packet in that channel, or the WTRU can randomly select other subbands, resources, RGFs, or transmission instants for possible transmission and perform CCA. This process can continue until the WTRU can select a resource / channel / RGF / transmission time instance for transmission, or when the WTRU does not find any resources for transmission within the selection window, the process can terminate.

[0114] In a second method, the WTRU may perform Procedure 2 by selecting X sub - bands / resources / RGFs / transmission instances for possible transmission from the set of available resources in Procedure 1. Thereafter, the WTRU may sequentially perform Procedure 3 which determines, for each of the X sub - bands, resources, RGFs, or transmission instances, whether a selected sub - band, resource, RGF, or transmission instance is available until it can select a sub - band, resource, RGF, or transmission instance for transmission or it cannot find a sub - band, resource, RGF, or transmission instance for transmission within the selection window.

[0115] In a third method, the WTRU may perform Procedure 2 by selecting a transmission instance for possible transmission from the set of available transmission instances in Procedure 1. A transmission instance may be considered available if it contains at least X available resources after Procedure 1, where X may be a fixed value. After Procedure 2, the WTRU may perform CCA to determine if any resources for transmission are available. If one or more resources are available, the WTRU may randomly select a resource for transmission. Otherwise, if all sub - bands are busy, the WTRU may select the next available transmission instance or may randomly select another available transmission instance to perform CCA. This 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.

[0116] In a fourth method, the WTRU may immediately perform Procedure 3 after Procedure 1 to further determine the resources available within a predefined window. Based on the resources considered available, the WTRU may then perform Procedure 2 to transmit on one or more of the randomly selected available resources.

[0117] Resource selection can be based on a combination of CCA, SCI decoding, backoff, and random selection. The WTRU can integrate CCA, SCI decoding, random resource selection, and backoff to select resources for transmission. In another set of embodiments, the WTRU can perform resource selection by combining 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, then by decoding the SCI of another WTRU, the WTRU can exclude resources reserved by other WTRUs. Process 2: The WTRU can select a subband, resource, RGF, or transmission instance for possible transmission and / or evaluation of CCA. Process 2 can be similarly performed by selecting resources based on a combination of CCA, SCI decoding, and random selection. Process 3: The WTRU can perform a Clear Channel Assessment (CCA) before transmitting a TB. Process 4: The WTRU can perform a backoff process by initially selecting a random backoff value in the range [0, B] and then reducing that backoff value according to a specific criterion. This backoff process can be used to randomize resource conflicts and prioritize channel access for packets with different priorities.

[0118] In any of the embodiments described herein, the WTRU can perform Process 1 before the CCA process to further exclude reserved resources by decoding the SCI between two CCA instances. The WTRU can decode any resource reservation signal / message (e.g., SCI_Notification message, preemption message, resource reservation sequence, etc.) to exclude reserved resources in the future. During the backoff process, the amount of backoff reduction and / or the range of the initial backoff value can depend on one or any combination of the following: the QoS of the MAC PDU, e.g., if the MAC PDU has a higher priority, the backoff value will be reduced more, and in one embodiment, the WTRU can 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 to the end of the resource selection window; the number of available channels / RGFs; the radio activity of the resource pool, carrier, or Bandwidth Part (BWP), e.g., CBR; the transmission order of a TB, e.g., 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 an initial transmission can be less than or greater than the maximum value for a retransmission.

[0119] In one embodiment, the WTRU may combine four processes to perform resource selection as follows: Initially, the WTRU may perform Process 1 on resources within a 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 following: 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 for transmission; the characteristics of the BWP, such as bandwidth, subcarrier spacing, etc.

[0120] After that, the WTRU may:

[0121] In a first method, the WTRU may perform Process 2 by performing CCA by selecting a subband. Then, the WTRU may 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 the 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 to the end of the resource selection window; the number of available channels / RGFs; and / or the radio activity of the resource pool / carrier / BWP.

[0122] In a 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 that subband.

[0123] In a third method, the WTRU may perform one CCA in multiple subbands. Specifically, at each transmission moment, the WTRU may determine the number of available resources, channels, or RGFs by performing CCA in the selected subbands. Then, the WTRU may reduce the backoff value. When the backoff value is less than or equal to zero, the WTRU may randomly select a resource for transmission.

[0124] Figure 4 is a timing diagram 400 that shows the WTRU using Figure 3Example of the third method 370 for performing resource selection, where the x-axis represents time 402 and the y-axis represents frequency 404 in this example. The WTRU performs resource selection in 4 subbands 406 - 412 in frequency 404. The WTRU can determine the RGF for a time slot transmission within a subband. First, the WTRU can exclude the resource(s) reserved by other WTRUs. Then, the WTRU can randomly select a backoff value within the range [0, B]. At each transmission moment, 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.

[0125] In Figure 4 CCA can be performed in each time slot. At CCA 414, no resource is determined to be available, and at 442, the backoff value can be set to or remain at 6. The same is true at CCA 416, 418, and the backoff value remains the same 444, 446. At CCA 416, parts of subband 1 406 and subband 3 410 are available, but the available part is 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 called non-forward reservation resources. After determining 4 436 available subbands 1 - 4 406 - 412, the WTRU can subtract 4 from 6, so the backoff value becomes 2 448. 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 can transmit on subband 2 408 in the next time slot. The WTRU can continue to determine the number of available subbands 440 while transmitting. If there is more data to transmit, the WTRU can continue to perform CCA 424 - 430 at time 402.

[0126] Resource selection can be based on a combination of CCA, backoff, and / or preemption. The WTRU can perform or determine resource allocation by combining CCA, backoff, and / or preemption. In one embodiment, the WTRU can perform resource allocation by combining CCA, backoff, and / or preemption. In particular, the WTRU can perform a resource allocation procedure, or the WTRU can perform a preemption that can preempt one or more transmission resources for the transmission of the WTRU. Preemption can occur when one or any combination of the following conditions are 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 count threshold, backoff threshold, or time to end of resource selection window threshold, etc.) can be determined by one or any combination of the following: the QoS of the MAC PDU, e.g., VQI, priority, latency, reliability, etc.; the congestion level of the resource pool, e.g., CBR; the size of the MAC PDU; the packet size and / or buffer size and / or traffic pattern.

[0127] The WTRU can perform one or more resource selections for transmission and retransmission. In one embodiment, the WTRU can determine the number of retransmissions based on the reliability or QoS of the MAC PDU (e.g., priority, reliability, and latency) and / or the radio activity of the resource pool (e.g., CBR). The WTRU can perform resource selection for transmission and retransmission by using the methods described.

[0128] Resource selection can be based on a combination of CCA and time division multiplexing (TDM) between control transmission and data transmission. 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 transmitting one or more PSSCHs to notify other WTRUs of the intention to transmit one or more PSSCH transmissions in the future. In one implementation, for a PSSCH transmission, the WTRU may be configured to transmit one or more SCI_Notification messages and a PSCCH, where the SCI_Notification message(s) 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 the SCI_Notification message(s), which may be used to notify other WTRUs of the future resource usage of one or more PSSCHs and to assist other WTRUs in decoding future PSSCH transmissions. An SCI_Notification message may implicitly or explicitly contain one of the following information elements regarding 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 the priority, latency, and / or reliability of the PSSCH; the frequency and time of PSSCH retransmission(s); MCS; transmit power; the granularity of the PSSCH (e.g., slot-based or non-slot-based); the time difference between the time requirements of the (one or more) PSSCHs and the data being transmitted, e.g., the amount of time slack associated with the data being transmitted in the associated PSSCH).

[0129] In one example, the SCI_Notification message contains the time-frequency resources and priorities of the PSSCH(s) and PSCCH involved. In this example, the WTRU may be required to transmit both the PSCCH and the PSSCH in the transmission(s) covered by the SCI_Notification. The PSCCH is used to transmit an SCI that conveys the information necessary to decode the PSSCH.

[0130] In another example, the SCI_Notification message includes VQI parameters, time-frequency resource(s) of the PSSCH(s) involved, MCS parameter(s), etc. Such information can 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 the half-duplex issue. Alternatively, the WTRU may not transmit another SCI to improve spectral efficiency, since 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 of the transmission in the associated PSSCH.

[0131] 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.

[0132] Figure 5 FIG. is a diagram showing a pool configuration 500 of the SCI_Notification 506. In one example, the WTRU may be configured to have a dedicated pool or a PSCCH resource pool 504 to transmit the SCI_Notification 506 for notifying other WTRUs about future PSCCH 508 and PSSCH 510 transmissions, as Figure 5 shown by option A 502. In another example, the WTRU may be configured to transmit the SCI_Notification 514 in the PSCCH resource pool 516 to assist other WTRUs in decoding future PSSCH transmissions 518, as Figure 5 shown by option B 512.

[0133] A WTRU may be configured to transmit multiple SCIs, where all the SCIs may be used for decoding the PSSCH, and one or more of the SCIs may be used as SCI_Notification(s). In one embodiment, a WTRU may be configured to transmit multiple SCIs, where all of the SCIs may be used for decoding the PSSCH, and one or more of the SCIs may be used as SCI_Notification(s). Specifically, the WTRU may be configured to transmit one or more SCI_Notifications before the transmission of the PSSCH, and the SCI_Notification may be used to notify other WTRUs of the resources for PSSCH transmission and the parameters for decoding the PSSCH. The WTRU may also be configured to transmit one SCI in the TB for the PSSCH. This embodiment may be triggered to increase the probability of successfully decoding the PSCCH by reducing the half-duplex problem.

[0134] It should be noted that hereinafter, SCI_Notification may refer to a message sent before the transmission of the PSCCH. When the SCI_Notification is sent, the WTRU may or may not be configured to send an SCI in the TB of the PSSCH.

[0135] The receiving WTRU may determine the parameters of the PSCCH transmission based on decoding of the SCI_Notification. In one embodiment, the WTRU may implicitly or explicitly determine the parameters for the PSCCH transmission involved in the transmission based on decoding of 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.

[0136] In one embodiment, the transmitter WTRU may be configured to use a predetermined MCS, as well as 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 involved PSCCH 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.

[0137] The WTRU may determine whether to use the SCI_Notification. In one embodiment, the WTRU may determine whether to use the SCI notification based on the attributes of its own transmission in combination with the measured environment. Specifically, in some cases, the WTRU may transmit the TB by first transmitting the SCI_Notification to reserve resources for the PSCCH / PSSCH and then transmitting the PSCCH / PSSCH. In other cases, the WTRU may perform the transmission of the TB by performing resource selection only for the PSSCH or the PSCCH alone.

[0138] The WTRU may determine whether to use the SCI_Notification based on a determination of any one or a combination of the following. In one example, the QoS and / or logical channel of the TB to be transmitted may provide a determination. For example, when the reliability of the transmission is higher than a specific threshold, the WTRU may perform the SCI notification. For example, when the latency associated with the transmission is higher or lower than a threshold, which may further depend on the amount of available resources from the sensing process, the WTRU may perform the SCI notification. For example, the WTRU may be configured with a set of logical channels for which the use of transmission with SCI_Notification is allowed. If the TB contains data from one or more such logical channels, the WTRU may perform the SCI_Notification for transmitting the TB.

[0139] In one embodiment, measurements at the WTRU (e.g., sensing or CBR measurements) can help determine whether to use SCI_Notification. For example, when the percentage of available resources is higher than a specific threshold, the WTRU can perform an SCI notification for the TB. The determination regarding the available resources can be based on the detection of SCI_Notification and / or an SCI transmission indicating forward reserved resources. For example, when the measured CBR or a similar congestion metric is higher than a threshold, the WTRU can perform an SCI_Notification for the TB.

[0140] The size of the TB to be sent can 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 can perform an SCI notification for the TB. For example, when the number of RBs in the same time slot occupied by the TB to be transmitted and / or the number of consecutive RBs in the same time slot exceeds a threshold, the WTRU can perform an SCI notification for the TB.

[0141] Resource pool configuration can be used to determine whether to use SCI_Notification. For example, when one or more physical sidelink feedback channel (PSFCH) resources are (pre)-configured to have a period of less than or equal to N time slots, the WTRU can perform an SCI_Notification, where the value of N can be (pre)-configured or provided by higher layer signaling.

[0142] The type of TB transmission (e.g., unicast, multicast, or broadcast transmission type) can be used to determine whether to use an SCI notification. For example, the WTRU can perform an SCI notification for unicast and / or multicast traffic. In an example, the SCI notification may not be used for unicast and / or multicast traffic but may be used for broadcast traffic.

[0143] In an exemplary embodiment, the WTRU can be configured to have a table of threshold reliability values for a given CBR range, e.g., by using a channel contention value. The WTRU can perform an SCI notification as long as the reliability of the packet to be transmitted is higher than the threshold associated with the measured CBR.

[0144] The WTRU can determine when to transmit an SCI_Notification based on the QoS requirements of the packet. The WTRU can determine to transmit an SCI_Notification message based on the QoS requirement(s) of the packet. In one embodiment, the WTRU can be configured to determine an SCI_Notification transmission window based on the priority of the packet. For example, the WTRU can be configured to be in the range [n + T min,n + T max for transmission, where n is the time for the WTRU to perform resource selection, and T min may depend on the capabilities of the WTRU, and T max may be determined based on the priority of the packet.

[0145] 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 within a resource selection window in the range [n + T 1 , n + T 2 , where T 1 and T 2 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 PPP value), then T 1 and T 2 may be smaller. Alternatively, the WTRU may be configured to select PSSCH and / or PSCCH resources in the range [n + T max + offset, n + T2], where the offset may be determined based on the priority of the packet or a fixed value.

[0146] The WTRU may determine the PSSCH and / or PSCCH transmission window based on the result of the resource selection of 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 value of Tmin and / or Tmax may be determined based on the QoS of the packet. The WTRU may first perform the resource selection for SCI_Notification(s). Assuming that the last resource for SCI_Notification for a resource allocation process may occur at time slot n + T, the WTRU may determine the resource selection window for PSSCH and / or PSCCH transmission in the range [n + T + offset, n + T2], where the offset may 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 may be determined based on a different function, which may depend on any of the factors listed above for determining the offset.

[0147] 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 involved therewith. 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).

[0148] 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 configured by the gNB via radio resource control (RRC) signaling or via system information broadcast (SIB).

[0149] In one embodiment, the WTRU may be configured to first perform resource selection for SCI_Notification, and then the WTRU may determine a resource selection window for PSSCH and / or PSCCH taking into account the time gap or offset limit 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 resource 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].

[0150] In one embodiment, the WTRU may first perform resource selection for the PSSCH and / or PSCCH, and then the WTRU may perform resource selection for the SCI_Notification taking into account the time gap limit offset. Specifically, the WTRU may be configured to select a resource selection window for the 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 the SCI_Notification(s) in the range [n + T1, n + T - offset].

[0151] 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 resource to determine the availability of the PSSCH resource 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 resource may be considered available.

[0152] The WTRU may determine the availability of the 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 the 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 resource with a threshold, which may be determined based on the relative QoS of the PSSCH and / or PSCCH involved and the pending TB 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.

[0153] 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 as / overlap 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, e.g., allowing the transmission of the WTRU TB when the available resources are below a threshold; the time difference (e.g., slack time) between the decoded PSSCH and its timing requirement is higher than a threshold, and / or greater than the latency requirement of the WTRU's own transmission; the measured CBR is higher than a threshold.

[0154] A WTRU that decides to override an SCI_Notification may perform resource selection and transmit its own SCI notification such that it occurs at least some time offset before the PSSCH / PSCCH resources reserved by the original SCI_Notification being overridden. The WTRU may also use modified resource selection criteria / parameters, such as modified thresholds, larger resource pools, increased TX power, or greater repetition counts, etc., during the resource selection and / or transmission of its own SCI_Notification. Such modification can 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, if the WTRU cannot find resources for its own SCI_Notification (which occurs at least some offset before the reserved PSSCH / PSCCH resources), the WTRU may cancel the transmission of the overridden SCI_Notification.

[0155] When the WTRU detects that the SCI_Notification or PSSCH and / or PSCCH resources it has selected 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 the SCI_Notification or SCI message 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.

[0156] The WTRU may determine the conflict handling process based on whether the SCI_Notification has been transmitted. In some embodiments, the WTRU may perform two different conflict handling processes. One process may be performed before the transmission of the SCI_Notification, while the other process may be performed after the transmission of the SCI_Notification. This embodiment may be triggered to distinguish the behavior of other WTRUs before the SCI_Notification transmission. The conflict handling before the SCI_Notification transmission may be triggered to avoid conflicts between two WTRUs that select the same resources, where one WTRU may not have information about the transmission of the other WTRU. However, the conflict handling after the SCI_Notification transmission may be triggered to resolve the situation where one WTRU may need to preempt the resources of another WTRU.

[0157] 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 transmissions of other WTRUs to detect potential conflicts after selecting resources for SCI_Notification and / or PSSCH and / or PSCCH and before SCI_Notification transmission. If one or any combination of the following conditions is met, the WTRU may perform resource reselection for SCI_Notification and / or PSSCH and / or PSCCH or discard the packet: The WTRU detects an SCI or SCI_Notification that involves or reserves a resource conflicting with the resources selected by the WTRU; The RSRP_PSSCH or RSRP_PSCCH measured on the SCI / SCI_Notification or the involved PSSCH resource is greater than a threshold. This threshold may be pre-configured or configured by the network via SIB or RRC messages.

[0158] The WTRU may perform potential conflict handling after SCI_Notification transmission and before the corresponding PSSCH and / or PSCCH transmission. In one embodiment, the WTRU may perform potential conflict handling after SCI_Notification transmission. Specifically, the WTRU may monitor transmissions of other WTRUs to detect potential conflicts after selecting resources for SCI_Notification and / or PSSCH and / or PSCCH and after SCI_Notification transmission. If one or any combination of the following conditions is met, the WTRU may perform resource reselection for SCI_Notification and / or PSSCH and / or PSCCH or discard the packet: The WTRU detects an SCI or SCI_Notification that involves or reserves a resource conflicting with the resources 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 involved PSSCH resource is greater than a threshold. This threshold may be pre-configured or configured by the network via SIB or RRC messages.

[0159] The WTRU may determine whether to transmit SCI_Notification to notify of 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, e.g., VQI, priority, latency, reliability, etc.; congestion level of the resource pool, e.g., CBR; size of the MAC PDU; packet size and / or buffer size and / or traffic pattern.

[0160] In one embodiment, if the VQI of the data is within a specific range, the WTRU may determine to transmit one or more SCI_Notification messages. In another embodiment, if the priority, reliability, or latency requirement of the MAC PDU 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 high-priority, high-reliability, or high-latency data by providing notification prior to these transmissions.

[0161] In another embodiment, if the CBR of the resource pool is greater than a threshold, the WTRU may determine to transmit the SCI_Notification message(s). This embodiment may reduce collisions when the resource pool is congested. The WTRU may perform CBR measurements on the resource pool dedicated to control, data, or SCI_Notification to determine whether it should transmit the SCI_Notification message(s).

[0162] In another embodiment, if the size of the PSSCH transmission is greater than a threshold and / or the buffer size of the WTRU 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-sized packets. This is because the probability of collision for transmissions of large TBs may be higher than that for transmissions of small TBs.

[0163] Figure 6FIG. 600 is a timing diagram showing 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 instances to transmit the SCI_Notification message(s). In one embodiment, the resource allocation mode includes network scheduling mode and WTRU or WTRU scheduling mode. In one embodiment, for a particular CBR range, the WTRU may be (pre)-configured with different channel access instances 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 instance for the SCI_Notification message(s) for all MAC PDUs; however, as Figure 6 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.

[0164] In Figure 6 , the x-axis represents time 602 and the y-axis represents frequency 604. CCA 606 - 612 may be performed at the start of four time slots 614 - 620. In time slot 614, symbol 622 may be for high priority. Subsequently, in the same time slot 614, symbol 624 may be for medium priority transmission. In time slot 616, symbol 626 may be for high priority transmission. Another symbol 628 may be for medium priority transmission, followed by symbol 630 for low priority transmission. Thus, symbols for low priority transmission may be dedicated only every other time slot, saving bandwidth for high priority transmission. Similarly, time slot 618 may include high priority symbol 632 and medium priority symbol 634. Time slot 620 may include high priority symbol 636, medium priority symbol 638, and low priority symbol 640.

[0165] In another embodiment, the WTRU may be configured to depend on different channel access instances based on a combination of resource allocation patterns and / or data QoS. Specifically, if the WTRU is operating in the 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 time slot if the WTRU is operating in the network scheduling mode and in every odd time slot if the WTRU is operating in the WTRU scheduling mode.

[0166] 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 the following: QoS characteristics of the MAC PDU, e.g., VQI, priority, latency, reliability, etc.; congestion level of the resource pool, e.g., CBR; size of the MAC PDU; packet size and / or traffic pattern.

[0167] 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 of the resource pool (e.g., CBR). Specifically, for a particular 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-sized packets. This embodiment may reduce the collision probability of large-sized packets, which may help reduce resource waste due to congestion of large-sized packets.

[0168] 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 sequentially perform CCA 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 has transmitted all N SCI_Notification messages or when the WTRU reaches the end of the resource selection window. This embodiment may ensure that the WTRU can 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, the WTRU may not be able to select sufficient transmission resources for the N SCI_Notification transmissions within the resource selection window due to the possibility that the channel becomes unavailable after a CCA event. The value of M may be determined based on one or any combination of the following: the QoS characteristics of the MAC PDU (e.g., VQI, priority, latency, reliability, etc.); the congestion level of the resource pool, e.g., CBR; the size of the MAC PDU; the 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.

[0169] Figure 7 FIG. 700 is an illustration showing the WTRU randomly selecting four time-frequency resources to perform CCA for transmitting two SCI_Notification messages. In Figure 7 FIG. 700, the WTRU randomly selects four time-frequency resources 726, 720, 730, 732 at time 702 and frequency 704 to perform CCA for transmitting two SCI_Notification messages.

[0170] In Figure 7In the example shown, based on the QoS and / or size of the CBR and / or MAC PDU, the WTRU may need to transmit two SCI_Notification messages. The WTRU determines to select four time-frequency resources 726, 720, 730, 732 to perform CCA 734 - 740 for potential SCI_Notification transmission. 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 sufficient 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.

[0171] Figure 8 FIG. 800 is a diagram showing options 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, as Figure 8 shown in option A810. This embodiment may mitigate the half-duplex problem where the WTRU loses one SCI_Notification message. The WTRU is able to detect other SCI_Notification messages to obtain information about future PSSCH and / or PSCCH transmissions.

[0172] 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, as Figure 8 shown in option B 830. This embodiment may reduce the number of SCI_Notification transmissions to notify multiple PSSCH and / or PSCCH transmissions.

[0173] 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.

[0174] Option C 850 shows two SCI_Notification messages 852, 854, which are used to indicate multiple PSCCH transmissions 856, 858 and multiple PSSCH transmissions 860, 862.

[0175] The SCI_Notification message can indicate multiple transmissions of a TB. Specifically, the SCI_Notification can explicitly or implicitly include one or any combination of the following information for multiple transmissions of a TB: time-frequency resources for the initial transmission and possible retransmission(s); hopping pattern / index for transmission and retransmission(s); time gap between transmission and retransmission(s); time gap between two retransmissions; number of retransmission(s); style index for transmission.

[0176] The WTRU can determine the transmission style of a TB based on the QoS of the TB. In one embodiment, the WTRU can determine the parameters for transmitting the TB based on the QoS of the TB and / or the congestion level of the resource pool (e.g., CBR). Specifically, the WTRU can 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: size of the time-frequency resource; number of transmissions; time gap between the initial transmission and retransmission and the time gap between two retransmissions; whether hopping is enabled or disabled.

[0177] In one example, the WTRU can determine the number of transmissions of a TB based on the reliability of the TB. The WTRU can determine the time gap between the initial transmission and retransmission and the time gap between two retransmissions based on the delay and / or priority of the TB. Alternatively, the WTRU can decide whether to enable or disable hopping based on the reliability of the TB.

[0178] The WTRU may change the resource selection process for PSCCH and / or PSSCH transmission based on whether the SCI_Notification has been transmitted. In one embodiment, the WTRU may change the resource selection process for PSCCH and / or PSSCH transmission based on whether the SCI_Notification has been transmitted. If the SCI_Notification message has not been 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 have been transmitted, the WTRU may select resources for PSCCH and / or PSCCH as follows. When the 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 notification.

[0179] In one embodiment, the WTRU may exclude the resources (one or more) forward reserved by the PSCCH transmission (one or more). Specifically, for the resources forward reserved by the PSCCH (one or more), the WTRU may use a similar process in LTE V2X, where if the PSSCH_RSRP and / or PSCCH_RSRP of the reserved resources is greater than a threshold, the WTRU may exclude the reserved resources.

[0180] The WTRU may exclude the PSSCH and / or PSCCH resources notified by SCI_Notification, preemption, resource reservation sequence, etc. In another embodiment, the WTRU may exclude the resources notified by SCI_Notification, preemption, resource reservation sequence. 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 example, the WTRU may be (pre)-configured with a table regarding the RSRP threshold(s). Then the WTRU may determine the index and the corresponding threshold based on the transmitted QoS (e.g., VQI, priority, latency, reliability) and the QoS of the SCI_Notification or preemption message.

[0181] In one embodiment, the WTRU may use the same table for PSSCH_RSRP; however, when comparing with the RSRP of the SCI_Notification or preemption message, the WTRU may apply a delta value to the values in the table. The value of delta 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 when the WTRU has to use multiple threshold tables, it may reduce the complexity of the resource selection process.

[0182] Figure 9 is a timing diagram 900 showing the side-link received signal strength indicator (S-RSSI) calculation 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 the upper layer (e.g., 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 / moment, which may be represented by n - T*j, where n is the moment 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 the time slot / moment having an aperiodic / event-triggered transmission in the frequency resource of the candidate resource. In Figure 9 the example shown, the resource pool supports reservation periods of 5, 10, 20, 50, j*100 (j = 1…10) (ms). The WTRU determines that T = 5 ms, so it may delay the S-RSSI calculation for each period of the 5 ms periods 912 - 918. In addition to having event-triggered / aperiodic transmission time slots, the WTRU determines the S-RSSI for the candidate resource by averaging the measured S-RSSI of the time slots that may be represented by n - 5j. The WTRU may transmit an SCI_Notification 920. The WTRU may continue to determine another candidate resource, such as candidate resource 922, in the resource selection window 924 at time 902 and frequency 924.

[0183] The WTRU may determine the PSSCH and PSCCH multiplexing scheme based on the characteristics of the data. In a set of embodiments, the WTRU may be configured to perform TDM, frequency division multiplexing (FDM), or a hybrid 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 following: the type of the data, e.g., periodic versus aperiodic; the QoS of the data, e.g., priority, latency, and / or reliability; the resource pool / BWP configuration, e.g., SCS; and / or the available reserved grant.

[0184] In one embodiment, the WTRU may determine the 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. To distinguish between periodic and aperiodic data, the WTRU may be configured to have two orthogonal logical channel sets for each type of data. The motivation may be to reduce the number of transmissions of periodic data and resource conflicts for aperiodic data.

[0185] 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 to MAC PDU transmission or the WTRU does not have a reserved grant, the WTRU may determine a 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, e.g., priority, latency, etc. The reserved grant may be dedicated to other services.

[0186] In another embodiment, when the WTRU does not have a suitable reserved 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 may help avoid resource conflicts for high-priority and / or reliable MAC PDUs. Alternatively, if the WTRU has a suitable reserved resource for MAC PDU transmission, the WTRU may determine an FDM scheme between the PSSCH and PSCCH.

[0187] In a set of embodiments, a WTRU may determine to perform resource selection for multiple transport blocks (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 of which requires one beam transmission; one or more TBs, and each of which requires K>1 beam transmissions.

[0188] 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 state of the buffered data is greater than a specific threshold; when the CBR of the resource pool is less than or greater than a certain threshold; when it is configured to perform carrier aggregation (CA) transmission or multi-bandwidth part (BWP) transmission; when data for a specific logical channel is received (e.g., such a logical channel is associated with data or a radio bearer having packets with a size greater than a specific threshold); when the number of available alternative carriers or BWPs for the WTRU is below a specific value; when using a separate resource selection process or sidelink process to transmit a TB would cause the WTRU to exceed its maximum number of sidelink processes; when the size of the arriving packet is greater than a threshold.

[0189] 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 use a single SCI_Notification to reserve resources for the transmission of multiple TBs based on one or any combination of the following: when the buffer state 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 state of the data is greater than a specific 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 multi-BWP transmission; when data for a specific logical channel is received, e.g., such a logical channel is associated with data or a radio bearer having at least one packet with a size greater than a specific threshold; when the number of available alternative carriers or BWPs for the WTRU is below a specific value; when using 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) for certain TBs is below a threshold.

[0190] A WTRU may use an 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 the transmission(s) of the same or a different TB(s). The WTRU may use the one or more reserved resources for one or more transmissions of one of the following: for example, a retransmission of the same TB, which uses the same or a 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 bursty traffic, e.g., the two TBs may belong to the same packet from the upper layer; or a transmission of any other TB.

[0191] The WTRU may use different mappings in the time domain to indicate the reserved resources for the transmission of the TB. In one embodiment, the WTRU may be configured to use different mappings between a bit field indicated in the SCI and the timing offset between the following two: the SCI transmission and the timing of the resources reserved for the transmission of the TB. This method may be motivated to support the WTRU in indicating different types of reserved resources, such as reserved resources for SPS services, retransmissions, and bursty traffic. For example, the WTRU may be configured to use 3 bits in the SCI to indicate the reserved time resources for retransmitting the TB and for transmitting another TB in bursty traffic, where one 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 transmissions; however, one value indicated by this bit field may correspond to an index in a table of SPS periods, which may be described in Table 1. Index Coded bit SPS period (3 ms) 1 001 3 2 010 5 3 011 10 4 100 20 5 101 30 6 110 40 7 111 50 Table 1: Mapping between Index and SPS Period

[0192] 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 the SCIs associated with different transmissions to reserve different resources for different types of transmissions. This method may be motivated 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 SCIs associated with the first X transmissions to reserve resources for one or more retransmissions and for the transmission of another TB in bursty traffic. The WTRU may also be configured to use the SCIs associated with the last Y transmissions(s) to reserve the resource(s) for transmitting other TB(s) 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 one TB.

[0193] The WTRU may be configured to indicate the type of TB reserved in the SCI. In one embodiment, the WTRU may be configured to reserve one or more resources for the transmission of one or more types of TB. In one method, the WTRU may indicate the type of TB 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 a TB in SPS traffic or for a TB in burst traffic.

[0194] The WTRU may be configured to use a reservation table, where different sets of code points may be used for the reservation of different types of TB. For example, the WTRU may be configured with two sets of code points in the table, where the first set is used to reserve resources for a TB in SPS traffic and the other set is used to reserve resources for a TB in burst traffic. This method may be triggered to allow the receiving WTRU to distinguish between different types of TB reservations, where the SPS reservation may apply to multiple cycles and the burst reservation may apply to only one cycle.

[0195] The WTRU may be configured to determine which type of TB to reserve based on a pool configuration. In one embodiment, the WTRU may be configured to reserve resources for the transmission of a TB for one or any combination of the following in a resource pool: the TB transmission of SPS traffic; the TB transmission of burst traffic; or one or more TB retransmissions. This method may be triggered to allow the system to enable / disable one or more types of resource reservations.

[0196] Resource selection may be performed in a BWP / carrier. The WTRU may consider the resources for multiple transmissions as a single resource or a sidelink process during the resource selection process. The WTRU may use the said process / algorithm to perform resource selection for multiple transmissions. This embodiment may reduce the number of resource selections or the resource selection time for multiple transmissions.

[0197] 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 following: the buffer status of the WTRU; the CBR of the resource pool; the resource pool configuration.

[0198] The WTRU may first attempt to utilize resource selection for a specific number of sidelink procedures and then increase or decrease the number of sidelink procedures when the first attempt fails. This method may be adjusted to select resources for one or more sidelink procedures or when the WTRU still has available data 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 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).

[0199] The failure / success of a specific attempt at resource selection using multiple sidelink procedures may be determined by any one or combination of the following: (pre)-configuration; QoS of the data to be sent; CBR; the maximum number of available subchannels available in any symbol / slot within the selection period; the size of the data.

[0200] 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 the occupied resources and selects X% of the total resources. Then, in the first stage of resource selection, the WTRU selects one resource for a 5TB transmission. In one embodiment, if the resource selection for one or more sidelink procedures in the first stage is not successful, then in the second stage, the WTRU performs resource selection for a 2TB transmission, and finally, the WTRU performs resource selection for a 1TB transmission.

[0201] The advantage of this embodiment is that it allows the WTRU to select several sidelink procedures and thus select different resource reservations that best meet the QoS requirements of the large packets to be transmitted, without requiring a large number of sidelink procedures, nor reserving a large amount of resources in a given time slot / symbol, and potentially leaving available resources for low-latency WTRUs.

[0202] In one embodiment, the WTRU determines the resources for the first transmission and may continuously transmit on the selected frequency resources for multiple transmissions.

[0203] The WTRU may follow the disclosed resource selection procedure (which may be used to determine resources for a 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 instance of the resource pool, except for the instances occupied / reserved by other WTRUs, to transmit subsequent TBs. The WTRU may avoid such occupied / reserved instances by waiting for the reserved transmission to complete and resuming its transmission, or it may select another sub - band to transmit the remaining TBs.

[0204] Figure 10 FIG. 1000 is a timing diagram showing SCI indications regarding one or more consecutive transmissions at time 1002. The WTRU may be configured to transmit an SCI to indicate its performance of a continuous data transmission. In one embodiment, the WTRU may transmit one or more SCIs 1014 - 1018 in a plurality of time slots 1008 - 1012 to indicate the transmission type (e.g., continuous type versus discontinuous type) and the start and end times of the continuous transmission. In one embodiment, the WTRU may transmit one SCI per transmission, where the prior SCI indicates information about one or more subsequent transmissions.

[0205] In Figure 10 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 an SCI 1014 - 1018 in each of 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 only one SCI 1020 in one time slot 1008, which reserves resources for the transmissions in 3 time slots 1008 - 1012.

[0206] The WTRU may be configured to perform resource reservation for variable - size periodic traffic. The WTRU may reserve resources with different priorities. In one embodiment, the WTRU may reserve resources for variable - size periodic traffic by indicating different priorities for each resource within a 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 the resources with a high probability of being used for the next transmission, and gradually lower the priority to other resources with a lower probability of being used.

[0207] This embodiment can help the WTRU reserve resources for packets of a specific size with data priorities. When the packet size decreases, the WTRU can reduce the MCS. When the packet size increases, if a reserved portion becomes unavailable, the WTRU can reduce the MCS to support more data in one transmission. Alternatively, the WTRU can perform another resource selection to transmit the remaining data of the packet.

[0208] The SCI can be designed for multi-priority reservation of packets. To support the receiving WTRU during the sensing process, the WTRU can indicate the reservation information in its SCI. In one embodiment, the WTRU can indicate the location and priority of each resource group in one SCI. Optionally, the WTRU can transmit one SCI for the reserved resources with the same priority.

[0209] In one example, the WTRU can reserve resources for packets of size 190 or 300 bytes with priority P1. It can 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 can reserve two transmissions for the 800-byte packet with priority P1 and another transmission for the 1200-byte packet with priority P2 = P1 + 2.

[0210] The WTRU can reserve resources for periodic SCI_Notification transmissions. In one embodiment, the WTRU can reserve one or more SCI_Notification reservation processes for periodic packets with variable sizes. Then, when transmitting the SCI_Notification, the WTRU can perform resource selection for PSSCH and / or PSCCH transmissions. Then the WTRU can update the content of the SCI_Notification accordingly based on the result of the resource selection process. This embodiment can allow the WTRU not to have to perform resource selection for the SCI_Notification message(s).

[0211] 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 the fixed resources may be determined based on the average packet size, or the amount of the fixed resources may be determined based on the minimum packet size. When the packet arrives, the WTRU may perform resource selection based on the size of the packet and the reserved resources or use the reserved resources.

[0212] The WTRU may perform resource selection across 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 with a specific application that requires transmission of a large amount of data.

[0213] The WTRU may perform resource selection to minimize the half-duplex problem. The WTRU may simultaneously select resources across multiple carriers or BWPs. The WTRU may perform resource selection across multiple carriers / BWPs simultaneously to minimize the half-duplex problem, where when the WTRU is receiving / transmitting on an adjacent carrier, it may not transmit / receive on other carriers. Specifically, when the WTRU has multiple TBs for transmission, it may determine to perform resource selection regarding N carriers / BWPs simultaneously. The WTRU may first determine the available transmission instances that have resource transmissions in each of the multiple carriers. Then, the WTRU may randomly select one or more transmission instances for transmission across all N carriers / BWPs. When the number of available transmission instances is less than a threshold, the WTRU may reduce N to perform further resource selection.

[0214] The WTRU may sequentially select resources for multi-carrier / BWP transmission. In one embodiment, the WTRU may sequentially perform resource selection for multiple TBs in each carrier / BWP. The WTRU may perform resource selection for the described one carrier / BWP. Then, the WTRU may perform resource selection for a second carrier / BWP to minimize the half-duplex problem. The WTRU may preferentially select a transmission instance that may be selected for transmission by the first carrier.

[0215] In one embodiment, the WTRU may perform different resource allocation schemes for initial transmission and retransmission(s). Specifically, the WTRU may perform resource selection for initial transmission by using any of the processes described, which may be based on decoding the SCI, SCI_Notification, CCA, backoff, and / or preemption. For the retransmission(s), the WTRU may first exclude the occupied resources, which may be determined by decoding the SCI or SCI_Notification, preemption messages from other WTRUs. The frequency resources for the retransmission(s) may be the same as the frequency resources of the initial transmission or may be randomly selected from a resource pool. The time resources for the retransmission(s) may be randomly selected and may satisfy one or any of the following conditions: the time gap between the initial transmission and the first retransmission is in the range of [1, X]; the time gap between two consecutive retransmissions is within [1, Y], where the value(s) of X and Y may be configured, e.g., preconfigured.

[0216] The WTRU may use the SCI or SCI_Notification of the initial transmission to reserve resources for the retransmission(s). The WTRU may use the SCI or SCI_Notification of the initial transmission to reserve resources for the 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: the number of retransmissions; the time-frequency resources of the retransmission; the time gap between different transmissions; frequency hopping for the transmission of the TB.

[0217] In one implementation, the WTRU may be preconfigured 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 receiving 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 the retransmission by the initial transmission of the transmitting WTRU.

[0218] The WTRU may use SCI_Notification to reserve one or more resources for the initial transmission and / or retransmission(s) of the TB. Specifically, for the initial transmission, the WTRU may transmit one or more SCI_Notification messages prior to the transmission of the PSSCH and / or PSCCH, where the SCI_Notification message may be used to reserve / indicate the 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, as shown in option 1 1004 of Figure 10 , 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 transmitting subsequent SCIs.

[0219] Methods for selecting one or more (pre)-configured resources are 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 SCI_Notification message, preemption message, or resource reservation sequence).

[0220] In one embodiment, the WTRU may be (pre)-configured with a set of resources for transmission. The WTRU may be instructed that the (pre)-configured resources are dedicated to the WTRU or shared among different WTRUs. In one embodiment, if any one or more of the following conditions are met, the WTRU may determine to perform non-sensing resource selection by randomly selecting one or more transmission resources: 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 the resource reservation signal / message (e.g., SCI_Notification message, preemption message, or resource reservation sequence) is below a threshold.

[0221] In one embodiment, if one or any combination of the following conditions are met, the WTRU may determine to perform sensing-based resource selection: the (pre)-configured resources are shared among different WTRUs; the CBR measured in the resource pool is greater than a threshold; the number of the resource reservation signal / message (e.g., SCI_Notification message, preemption message, resource reservation sequence) is greater than a threshold.

[0222] The threshold (e.g., CBR threshold, number of SCI_Notification messages, number of preemption messages, etc.) can be pre-configured for the WTRU or configured for the WTRU via RRC or SCI. The threshold can be determined based on the QoS of the packet (e.g., VQI, priority, latency, etc.).

[0223] The WTRU can determine a channel access scheme based on the QoS of the data. In one embodiment, the WTRU can 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 can determine to perform random selection. Alternatively, the WTRU can 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 a backoff procedure. The priority and / or latency threshold for packets performing different channel access schemes can be (pre)-configured or configured by the network via RRC or SIB.

[0224] Resource selection can be based on one or more patterns. In some embodiments, the WTRU can be configured to perform pattern-based transmission. Specifically, pattern-based transmission can be defined as transmission using one or more predefined time and possibly frequency resources.

[0225] In one embodiment, the WTRU can be configured into a pattern pool, where each pattern can be defined within a window. The window can be repeated, which allows the pattern to be repeated. Within a pattern window, each pattern can be defined as a set of transmission periods and possibly transmission frequencies within the pattern window. A transmission interval can consist of one or more time slots or can include one or more time slots.

[0226] Figure 11 FIG. 1100 shows a method used by the WTRU to reserve resources for retransmission using SCI_Notification for a first transmission. In Figure 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 the transmission of a first control information 1110 and a first retransmission 1112. The SCI_Notification 1106 may also indicate resources for the transmission of a second control information 1114 and a first retransmission 1116. The SCI_Notification may indicate a time gap 1118 between the end of the initial transmission 1108 and the first retransmission 1112. Another time gap may be indicated as being 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 be indicated additionally or alternatively.

[0227] The WTRU may be configured to have 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 set of possible patterns from Table 2. In each pattern, the bits set to 1 indicate transmission intervals, and the bits set to 0 indicate non-transmission intervals.

[0228] Figure 12 is an illustration showing an example pattern design 1200 of a 4-interval window resource pool. Figure 12 Shows three pattern windows 1206 - 1210 in time 1202. Each interval 1212 - 1234 of each pattern window 1206 - 1210 may occupy 2 time slots. In other embodiments, other pattern(s) and pattern options may be applicable. 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 Table 2: Set of possible patterns for 4-interval windows

[0229] The WTRU may determine a transmission pattern based on the QoS and / or CBR of the TB of the resource pool. In one embodiment, the WTRU may determine a transmission pattern based on the CBR of the resource pool and / or the QoS of the TB. Specifically, the WTRU may be configured with a table that indicates a minimum number and a 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 having a number of transmissions within the configured range.

[0230] 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: the duration of the pattern window; the duration of a transmission interval; the number of transmission resources for each pattern, e.g., the maximum and / or minimum number of (pre)-configured transmission resources for the pattern in the resource pool; the maximum / minimum time gap between transmissions in the pattern; the size of the frequency resources for each transmission.

[0231] 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 the transmission of a TB: the number of transmissions for the TB; the duration of a single transmission of the TB; the frequency range of one or more transmissions; the total transmission time; and / or based on frequency hopping, e.g., based on a frequency hopping pattern or based on whether frequency hopping is employed. 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.

[0232] The WTRU may determine the available set of patterns based on the QoS of the TB and / or the resource allocation time. In some embodiments, the WTRU may determine the available set of patterns based on one or any combination of the following: the QoS of the TB, e.g., priority, reliability, and / or latency; and / or the resource selection time compared to the pattern.

[0233] In one embodiment, the WTRU may determine the available set of patterns and / or a subset having one or more patterns based on the reliability of the TB. Based on the reliability of the TB, the WTRU may determine the minimum number of transmissions for the transmission of the TB. Then, the WTRU may determine the set of patterns, the number of transmissions of which is greater than or equal to the minimum number of possible transmissions of the TB. This embodiment may be promoted to allow the WTRU to select a transmission pattern that meets the reliability requirements of the TB. For example, for Figure 12 the 4-interval window resource pool described in, the WTRU may need to select transmission resources for a TB that requires at least 2 transmissions. Thus, the WTRU may determine the available set of patterns, the indices of which 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.

[0234] 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 having a transmission time before the resource selection time. For example, the WTRU may need to perform resource selection during a first interval and may need to select a pattern having at least two transmission intervals. The set of patterns having at least two transmission intervals may be {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}. The WTRU may exclude the set of patterns having transmissions in the first interval, such as {1, 2, 3, 4, 6, 7, 8, 9}. Thus, the set of available patterns is {5, 9, 10, 11}.

[0235] The WTRU may determine the 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 having 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 having an initial transmission in the first interval, while for a low-priority TB, the WTRU may be allowed to select a pattern having an initial transmission in the second interval. This embodiment may be motivated to allow the WTRU to reduce the probability of collisions in selecting patterns for TBs having different priorities.

[0236] In one embodiment, the WTRU may determine to combine multiple patterns in different pattern windows to transmit a TB. The WTRU may use the same or different pattern indices in the pattern window to transmit a TB. The WTRU may perform pattern combination to meet the QoS of the TB. Specifically, if the WTRU cannot select a pattern in the pattern window to meet the QoS of the TB, the WTRU may perform pattern combination. The WTRU may indicate its transmission across multiple pattern windows in the SCI or SCI_Notification to support another WTRU in sensing and decoding the message.

[0237] In one embodiment, the WTRU may indicate the use of a pattern or a subset of patterns in the 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: pattern index, frequency range for one transmission; number of transmission resources, and hopping indication.

[0238] Figure 13 is a timing diagram 1300 showing the WTRU determining the availability of a pattern based on the decoding of the SCI or SCI_Notification 1312. InFigure 13 In this case, the x-axis represents time 1302 and the y-axis represents frequency 1304. Three sub-channels 1306 - 1310 are shown in the frequency 1304. The WTRU can determine the availability of patterns based on sensing, such as pattern 1011 1314 and patterns 1316 - and / or a set of patterns and / or a subset of patterns. In one embodiment, the WTRU can determine the availability of a pattern and / or a set of patterns based on decoding the SCI and / or SCI_Notification 1312. Specifically, if the WTRU can decode the SCI or SCI_Notification 1312, which reserves a transmission pattern and the RSSI / RSRP of the reserved resources is greater than a threshold, the WTRU can determine that the reserved pattern and the pattern having a transmission in one resource of the reserved pattern are occupied.

[0239] In Figure 13 In the example shown, a WTRU can reserve the transmission pattern 1011 1314 in sub-channel 1 1310 by using the SCI_Notification 1312, and a WTRU can reserve the transmission pattern 0101 1316 in sub-channel 3 1306 by using the SCI. The WTRU determines that the pattern 1011 1314 in sub-channel 1 1310 is occupied, and it can also determine that for sub-channel 1 1310, all other patterns except pattern 0100 are occupied. Similarly, for sub-channel 3 1306, all patterns except 1000, 0010, and 1010 are considered occupied. The WTRU may not receive any information about the availability of sub-channel 2 1308 from the SCI_Notification 1312. Instead, the absence of a bitmap can indicate that sub-channel 2 1308 is available or unavailable. The pattern can be applied to a single pattern window, such as 1 pattern window 1318, 1320.

[0240] In one embodiment, the WTRU can determine the availability of a set of patterns by using CCA. Specifically, first the WTRU can determine the availability of resources by using CCA. If the resource is considered occupied, the WTRU can determine a set of patterns that can use the occupied resources. 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 can determine that all patterns having a transmission in the first interval are unavailable, that is, the WTRU can consider the pattern indices 1, 2, 3, 4, 6, 7, 8, 12 described in Table 1 as occupied. The WTRU can use a counter to revert to the resources in the group to restore previously occupied resources, otherwise the resources in the group are determined to be occupied.

[0241] Figure 14FIG. 1400 shows a schematic diagram in which a WTRU randomly selects a pattern window at time 1402 and frequency 1404 for transmitting a TB. The WTRU may select a pattern having 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] that includes or does not include pattern windows 1406-1414, and the resource selection window may be capable of meeting the QoS of the TB. The WTRU may then determine a set of pattern windows to perform one or more pattern selections. The set of pattern windows may be selected within the resource selection window [T1, T2]. The WTRU may randomly select one or more of the pattern windows 1406-1414 within [T1, T2] to perform pattern selection. As Figure 14 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 other than random selection may be employed.

[0242] In another embodiment, the WTRU may perform pattern selection and / or pattern window selection for the transmission of a TB by decoding the SCI and / or SCI_Notification and using a backoff counter to delay the transmission. Specifically, the WTRU may perform the following steps to perform pattern window selection and / or pattern selection.

[0243] Initially, the WTRU may generate a backoff counter to determine whether the WTRU is able to select a pattern window and / or a pattern for transmission. Specifically, if the backoff counter is less than or equal to zero, the WTRU is able to select a pattern window and / or a pattern for transmission. Otherwise, the WTRU may not be able to select the pattern window and / or the pattern. 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 an SIB or an RRC message. In an embodiment, when the backoff counter may be below a value other than 0, transmission may occur. Alternatively, the backoff counter may be incremented instead of decremented and may still be consistent with the embodiments herein.

[0244] Then, the WTRU may 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 having transmission resources that potentially conflict with the patterns indicated by the SCI and / or SCI_Notification. It may also exclude resources or patterns determined to be occupied by performing CCA.

[0245] Then, the WTRU may decrement the backoff counter, where the decrement may be based on one or any combination of the following: QoS of the TB; number of available resources; number of available patterns; number of postponed pattern windows; radio activity of the resource pool / carrier / BWP, e.g., a determined CBR.

[0246] 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 a 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.

[0247] In NR V2X, the WTRU may support fixed and / or variable-sized periodic traffic. The network may require the WTRU to report the traffic information to support the network in scheduling.

[0248] The WTRU may report multiple packet sizes for variable-sized periodic traffic in a WTRU assistance information element. In one embodiment, the WTRU may report different traffic information in the WTRU assistance information to notify the network of this feature. Specifically, if the upper layer indicates the existence of fixed-sized periodic traffic, the WTRU may report the size of the packet. However, if the upper layer indicates the existence of variable-sized periodic traffic, the WTRU may report N packet sizes. The value of N may be determined based on one or any combination of the following: the range of packet sizes supported by the upper layer; and / or the QoS range of the traffic.

[0249] In one example, the WTRU may be configured with an SPS configuration that alternates between the authorized size reported in the WTRU assistance information or an authorized size related to the size reported in the SPS configuration. Specifically, the WTRU may assume that the authorized size of consecutive resources of the SPS configuration matches or is related to each reported size. The WTRU may also receive signaling in the SPS configuration regarding the patterns of different authorized sizes within the SPS configuration. Alternatively, the WTRU may employ a fixed pattern (one consecutive authorization for each size) or may employ the pattern to match the information provided in the WTRU assistance information.

[0250] The WTRU may be configured to have one or more grant sizes associated with the SPS configuration, which are explicitly located within 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 requests X and 2X in the WTRU assistance information and is granted Y in the SPS configuration, it may assume Y and 2Y as consecutive grant sizes for the SPS.

[0251] In one embodiment, the WTRU may implicitly or explicitly indicate the packet size of variable-sized periodic traffic in the SR. In one embodiment, the WTRU may be configured to have 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. Thus, 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 using, for example, a size range. Then, when the packet is available at the buffer, the WTRU may use the appropriate configuration to indicate the size of the packet.

[0252] Figure 15 FIG. 1500 is a flow chart showing resource selection based on packet priority. In one 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. The 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 the backoff counter to an initial backoff value. In one example, the WTRU may use a look-up table to determine the backoff counter. Then, the WTRU may perform 1512 CCA on one or more resource time slots. When the CCA indicates that the resource is available, the backoff counter may be decremented 1514 by the number of available resources in each time slot. Then, the WTRU may determine 1516 whether the backoff counter is equal to or below 0, 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 continue to perform 1512 CCA.

[0253] Figure 16FIG. 1600 is a timing diagram showing a transmission process using a backoff counter. In the first time slot 1644 at time 1602, CCA can be performed along three sub-bands 1606-1610 in frequency 1604. In the first time slot 1644, sub-band 1606 may be busy due to forward reserved resources. Sub-band 1608 can be determined as an available channel access instance. Sub-band 1610 may be unavailable according to LBT. Therefore, 1 resource 1630 can be represented as available, and the backoff value can be reduced from 3 1636 to 2 1638. In the second time slot 1646, sub-band 1612 may be busy due to forward reserved resources. Sub-band 1614 can be determined as an available channel access instance. Sub-band 1616 may be busy due to forward reserved resources. Therefore, 1 resource 1632 can be represented as available, and the backoff value can be reduced from 2 1638 to 1 1640. In the third time slot 1648, sub-band 1618 may be available. Sub-band 1620 may be available. Sub-band 1622 may be unavailable. Therefore, 2 resources 1634 can be represented as available, and the backoff value can be reduced from 1 1640 to -1 1642. In the fourth time slot 1650, sub-band 1624 may be available. Sub-band 1626 may be unavailable. Sub-band 1628 can be selected for transmission.

[0254] Figure 17 FIG. 1700 is a flow chart showing an example method by which a WTRU selects a resource for transmission. Based on priority, the WTRU can be configured 1702 with multiple channel access instances within a time slot. The priority can be based on data packet priority or another priority. The WTRU can determine 1704 available resources on which CCA can be performed based on sensing the transmissions of other WTRUs. The WTRU can generate 1706 an initial backoff value based on the performance and / or priority of the CBR. At 1708, CCA can be performed on each available resource in the time slot. Whenever an available resource is determined in the time slot, the WTRU can reduce 1710 the backoff value accordingly. For example, the backoff value can be reduced by the number of available resources. When the backoff value is equal to or less than a threshold (e.g., 0) 1712, the WTRU can randomly select 1714 an available resource for transmission in a time slot. Until the backoff value reaches or exceeds the threshold, the WTRU can continue to perform 1708 CCA.

[0255] Although specific combinations of features and elements have been described above, those of ordinary skill in the art will recognize that each feature or element can be used alone or in any combination with other features and elements. Additionally, 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 wired or wireless connections) 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 memories, 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 comprises: storing reservation signal information, wherein the reservation signal information is associated with one or more priorities of data; determining a duration of a reservation signal based on the reservation signal information and a priority of data to be transmitted by the WTRU; and transmitting the reservation signal at a start position based on the determined duration of the reservation signal.

2. The method according to claim 1, further comprises: receiving configuration information associated with one or more channel access times, wherein the determination of the duration of the reservation signal is further based on the one or more channel access times.

3. The method according to claim 1, wherein the data to be transmitted by the WTRU comprises a media access control (MAC) protocol data unit (PDU).

4. The method according to claim 1, wherein, the reservation signal information is associated with a delay of data.

5. The method according to claim 1, wherein the duration of the reservation signal is further based on a delay of the data to be transmitted by the WTRU.

6. The method according to claim 1, wherein the duration of the reservation signal is further based on a quality of service (QoS) of the data to be transmitted by the WTRU.

7. A wireless transmit / receive unit (WTRU), the WTRU comprises: a transceiver; and a processor; wherein the transceiver and the processor are configured to: store reservation signal information, wherein the reservation signal information is associated with one or more priorities of data; determine a duration of a reservation signal based on the reservation signal information and a priority of data to be transmitted by the WTRU; and transmit the reservation signal at a start position based on the determined duration of the reservation signal.

8. The WTRU according to claim 7, wherein the transceiver and the processor are further configured to: receive configuration information associated with one or more channel access times, wherein, the determination of the duration of the reservation signal is further based on the one or more channel access times.

9. The WTRU according to claim 7, wherein the data to be transmitted by the WTRU comprises a media access control (MAC) protocol data unit (PDU).

10. The WTRU according to claim 7, wherein the reservation signal information is associated with a delay of data.

11. The WTRU according to claim 7, wherein the duration of the reservation signal is further based on a delay of the data to be transmitted by the WTRU.

12. The WTRU according to claim 7, wherein the duration of the reservation signal is further based on a quality of service (QoS) of the data to be transmitted by the WTRU.

13. A method performed by a wireless transmit / receive unit (WTRU), the method comprises: determining a priority of a data packet; determining a channel busy ratio (CBR) of a resource pool; Set the backoff counter to an initial backoff value according to at least one of the priorities of the said grouping or the CBR; Perform a Clear Channel Assessment (CCA) in multiple resource time slots; Reduce the backoff counter by the number of available resources in each resource time slot according to the CCA; and When the backoff counter reaches a threshold, randomly select a resource for transmission.

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