Coordinating carrier usage in multicarrier sidelink

Abstract

The present disclosure relates to an apparatus and a method for carrier coordination implemented in a wireless transmit / receive unit (WTRU). The method comprises: receiving one or more preferred carriers associated with a second WTRU; and triggering carrier reselection based on receiving the one or more preferred carriers. The method also includes performing carrier selection using the one or more preferred carriers, wherein the WTRU prioritizes the one or more preferred carriers through a carrier selection criterion. The method further includes determining a number of carriers to be selected based on the one or more preferred carriers; and selecting one or more carriers based on the one or more preferred carriers, wherein the selected carriers are limited based on the one or more preferred carriers. The method also includes transmitting a unicast transmission to the second WTRU using the selected resources of the first carrier / second carrier. The method further includes transmitting a multicast / broadcast sidelink transmission.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 395,581, filed on August 5, 2022, the contents of which are incorporated herein by reference in their entirety. Background Art

[0003] In the 3rd Generation Partnership Project (3GPP) standard, a device-to-device direct communication link may be referred to as a side link. Similar to the uplink and downlink, there are control channels and data channels in the side link. The control channel in the side link may be referred to as a physical side link control channel (PSCCH), and the data channel in the side link may be referred to as a physical side link shared channel (PSSCH). The PSCCH may be used to indicate the time domain / frequency domain resource location, modulation and decoding mode, and priority of the data carried in the PSSCH transmitted by the PSSCH, while the PSSCH may be used to carry data.

[0004] Control information and data in vehicle-to-vehicle / pedestrian / infrastructure / network or vehicle-to-everything (V2X) communication may be transmitted via a side link, and at this time, V2X communication may include two transmission modes: transmission mode 3 (Mode 3) and transmission mode 4 (Mode 4). Regarding Mode 3, the transmission resources of PSCCH and PSSCH of a WTRU (referred to as a V2X WTRU) may be allocated by an evolved Node B (eNB), and the WTRU may determine the transmission resources of PSCCH and PSSCH by receiving a side link resource allocation indication sent by the eNB via a physical downlink control channel (PDCCH) or an enhanced PDCCH (EPDCCH). In Mode 4, the transmission resources of PSCCH and PSSCH may be autonomously selected by the WTRU based on the channel detection result. During the channel detection process, the WTRU may first determine the time-frequency resource location and priority of the scheduled PSSCH by receiving the PSCCH sent by other WTRUs, and may then further detect the demodulation reference signal received power (PSSCH-RSRP) of the scheduled PSSCH, and exclude resources with a PSSCH-RSRP higher than a specific threshold; and then the WTRU may calculate the average received energy (S-RSSI) of the remaining resources, and may select one resource from the resources with the lowest S-RSSI as the transmission resource. Summary of the invention

[0005] Aspects of the present disclosure relate to carrier coordination, and more particularly to carrier selection and resource selection in a multi-carrier sidelink.

[0006] A wireless transmit / receive unit (WTRU) (such as a first WTRU) may include a processor and a transceiver. In addition, in some examples, the WTRU (e.g., the first WTRU) may be configured to perform a method including any combination of the following. The processor and the transceiver of the first WTRU may be configured to receive configuration information indicating a carrier selection criterion. The processor and the transceiver of the first WTRU may be configured to receive a sidelink message from a second WTRU indicating a set of preferred carriers for sidelink transmission. In some examples, the sidelink message may be a first PC5-RRC reconfiguration message.

[0007] The processor and the transceiver of the first WTRU may be configured to select at least a first carrier for unicast sidelink transmission with the second WTRU. The first carrier may be selected from the set of preferred carriers based on a condition that the first carrier satisfies the carrier selection criteria. The processor and the transceiver of the first WTRU may be configured to determine that the first carrier cannot be used for broadcast sidelink transmission. The processor and the transceiver of the first WTRU may be configured to select at least a second carrier for broadcast sidelink transmission, the second carrier not being in the set of preferred carriers. The processor and the transceiver of the first WTRU may be configured to transmit an indication of the selected first carrier and the second carrier to the second WTRU in a second message. In some examples, the indication may be transmitted together with a second PC5 RRC reconfiguration message.

[0008] In some embodiments, the processor and the transceiver of the first WTRU may be configured to transmit unicast transmissions to the second WTRU using selected resources of the first carrier and to transmit multicast / broadcast transmissions using selected resources of the second carrier.

[0009] In some examples, the carrier selection criteria may include a channel busy ratio (CBR) threshold. The first WTRU may be configured to select the first carrier from the set of preferred carriers based on a condition that the first carrier has a CBR below the CBR threshold. In addition, in some embodiments, the processor and the transceiver of the first WTRU are configured to select the second carrier for broadcast sidelink transmission based on the second carrier having a lowest CBR among a plurality of carriers that are not in the set of preferred carriers.

[0010] In some examples, the carrier selection criteria may include a received signal power (RSRP) threshold. The first WTRU may be configured to select the first carrier from the set of preferred carriers based on the condition that the first carrier has a measured RSRP that is higher than the RSRP threshold. In some examples, the carrier selection criteria may include a listen-before-talk (LBT) failure threshold. The first WTRU may be configured to select the first carrier from the set of preferred carriers based on the condition that the LBT failures experienced by the first carrier within a preconfigured time period are less than the LBT failures. In some examples, the carrier selection criteria may include a hybrid automatic repeat request (HARQ) threshold. The first WTRU may be configured to select the first carrier from the set of preferred carriers based on the condition that the first carrier has an ACK to NACK ratio higher than the HARQ threshold.

[0011] The processor and the transceiver of the first WTRU may be configured to receive a second sidelink message from the second WTRU indicating a set of non-preferred carriers for sidelink transmissions, wherein the set of non-preferred carriers includes the second carrier. The processor and the transceiver of the first WTRU may be configured to select the second carrier for broadcast sidelink transmissions based on a condition that the second carrier satisfies a second carrier selection criterion. In some examples, the second carrier selection criterion may be different from the carrier selection criterion used to select the first carrier for unicast sidelink transmissions.

[0012] In addition, in some examples, the present disclosure relates to a WTRU that includes a processor and a memory that may be configured to receive one or more preferred carriers associated with a second WTRU. The WTRU may be configured to trigger carrier reselection based on receiving the one or more preferred carriers, and to perform carrier selection using the one or more preferred carriers. The WTRU may prioritize the one or more preferred carriers. The WTRU may be configured to determine a number of carriers to select based on the one or more preferred carriers. The WTRU may be configured to select one or more carriers based on the one or more preferred carriers, where, for example, the selected carriers may be limited based on the one or more preferred carriers. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1A is a system diagram illustrating an example communication system in which one or more disclosed embodiments may be implemented.

[0014] Figure 1B is an example of a method that can be used according to an embodiment of the present invention. Figure 1A A system diagram of an example wireless transmit / receive unit (WTRU) for use within an illustrated communication system.

[0015] Figure 1C is an example of a method that can be used according to an embodiment of the present invention. Figure 1A System diagram of an example Radio Access Network (RAN) and an example Core Network (CN) for use within an illustrated communication system.

[0016] Figure 1D is an example of a method that can be used according to an embodiment of the present invention. Figure 1A System diagram of another example RAN and another example CN for use within the illustrated communication system.

[0017] Figure 2 is a flow chart of an example process 200 performed by a WTRU for coordinating carrier usage in a multi-carrier sidelink. DETAILED DESCRIPTION

[0018] Figure 1A 1 is a diagram illustrating an example communication system 100 in which one or more disclosed embodiments may be implemented. The communication system 100 may be a multiple access system that provides content such as voice, data, video, messaging, broadcast, etc. to multiple wireless users. The communication system 100 may enable multiple wireless users to access such content through sharing of system resources (including wireless bandwidth). For example, the communication system 100 may employ one or more channel access methods such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single carrier FDMA (SC-FDMA), zero tail unique word DFT spread OFDM (ZT UW DTS-s OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, and filter bank multi-carrier (FBMC), etc.

[0019] like Figure 1AAs shown, the communication system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, RAN 104 / 113, CN 106 / 115, public switched telephone network (PSTN) 108, Internet 110 and other networks 112, but it should be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. By way of example, the UE 102a, 102b, 102c, 102d (any of which WTRU may be referred to as a “station” and / or “STA”) may be configured to send and / or receive wireless signals and may include a user equipment (WTRU), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular phone, a personal digital assistant (PDA), a smart phone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watch or other wearable device, a head-mounted display (HMD), a vehicle, a drone, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in an industrial and / or automated process chain environment), a consumer electronic device, a device operating on a commercial and / or industrial wireless network, etc. Any of the WTRUs 102a, 102b, 102c, and 102d may be interchangeably referred to as a UE.

[0020] The communication system 100 may also include a base station 114a and / or a base station 114b. Each of the base stations 114a, 114b may be any type of device that is configured to interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the CN 106 / 115, the Internet 110, and / or other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a Node B, an eNode B, a Home Node B, a Home eNode B, a gNB, an NR Node B, a site controller, an access point (AP), a wireless router, and the like. Although the base stations 114a, 114b are each depicted as a single element, it should be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0021] Base station 114a may be part of RAN 104 / 113, which may also include other base stations and / or network elements (not shown), such as base station controllers (BSC), radio network controllers (RNC), relay nodes, etc. Base station 114a and / or base station 114b may be configured to send and / or receive wireless signals on one or more carrier frequencies (which may be referred to as cells (not shown)). These frequencies may be in a licensed spectrum, an unlicensed spectrum, or a combination of a licensed spectrum and an unlicensed spectrum. A cell may provide coverage of wireless services to a specific geographic area, which may be relatively fixed or may change over time. The cell may be further divided into cell sectors. For example, the cell associated with base station 114a may be divided into three sectors. Therefore, in one embodiment, base station 114a may include three transceivers, i.e., one transceiver for each sector of the cell. In an embodiment, base station 114a may employ multiple-input multiple-output (MIMO) technology and may utilize multiple transceivers for each sector of the cell. For example, beamforming may be used to send and / or receive signals in a desired spatial direction.

[0022] The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d over an air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0023] More specifically, as noted above, the communication system 100 may be a multiple access system and may employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, and SC-FDMA, among others. For example, the base station 114a in the RAN 104 / 113 and the WTRUs 102a, 102b, 102c may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may use Wideband CDMA (WCDMA) to establish the air interface 115 / 116 / 117. WCDMA may include communication protocols such as High Speed ​​Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High Speed ​​Downlink (DL) Packet Access (HSDPA) and / or High Speed ​​UL Packet Access (HSUPA).

[0024] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 116 using Long Term Evolution (LTE) and / or Advanced LTE (LTE-A) and / or Advanced LTE Pro (LTE-A Pro).

[0025] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as NR radio access, which may establish the air interface 116 using New Radio (NR).

[0026] 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 together implement LTE radio access and NR radio access, for example using the dual connectivity (DC) principle. Thus, the air interface utilized by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions transmitted to / from multiple types of base stations (e.g., eNBs and gNBs).

[0027] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.11 (i.e., Wireless Fidelity (WiFi)), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile Communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), and GSM EDGE (GERAN).

[0028] Figure 1AThe base station 114b in may be, for example, a wireless router, a Home NodeB, a Home eNodeB, or an access point, and may utilize any suitable RAT to facilitate wireless connectivity in local areas such as commercial venues, homes, vehicles, campuses, industrial facilities, sky corridors (e.g., for use by drones), and roads. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement radio technologies such as IEEE 802.11 to establish a wireless local area network (WLAN). In an embodiment, the base station 114b and the WTRUs 102c, 102d may implement radio technologies such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.) to establish a picocell or a femtocell. As Figure 1A As shown, base station 114b may have a direct connection to Internet 110. Therefore, base station 114b may not need to access Internet 110 via CN 106 / 115.

[0029] The RAN 104 / 113 may be in communication with the CN 106 / 115, which may be any type of network configured to provide voice, data, applications and / or Voice over Internet Protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have different quality of service (QoS) requirements, such as different throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 / 115 may provide call control, billing services, mobile location-based services, prepaid calling, Internet connectivity, video distribution, etc., and / or perform high-level security functions, such as user authentication. Although not described in detail in the text and video, the CN 106 / 115 may be configured to provide voice, data, applications and / or Voice over Internet Protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have different quality of service (QoS) requirements, such as different throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 / 115 may provide call control, billing services, mobile location-based services, prepaid calling, Internet connectivity, video distribution, etc., and / or perform high-level security functions, such as user authentication. Figure 1A Although not shown in the figure, it will be appreciated that the RAN 104 / 113 and / or the CN 106 / 115 may be in direct or indirect communication with other RANs that employ the same RAT as the RAN 104 / 113 or a different RAT. For example, in addition to being connected to the RAN 104 / 113, which may utilize NR radio technology, the CN 106 / 115 may also be in communication with another RAN (not shown) that employs GSM, UMTS, CDMA2000, WiMAX, E-UTRA, or WiFi radio technology.

[0030] The CN 106 / 115 may also act as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or other networks 112. The PSTN 108 may include a circuit-switched telephone network that provides plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols, such as the Transmission Control Protocol (TCP), the User Datagram Protocol (UDP), and / or the Internet Protocol (IP) in the TCP / IP Internet protocol suite. The networks 112 may include wired communication networks and / or wireless communication networks owned and / or operated by other service providers. For example, the networks 112 may include another CN connected to one or more RANs, which may employ the same RAT as the RAN 104 / 113 or a different RAT.

[0031] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communication system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks via different wireless links). Figure 1A The illustrated WTRU 102c may be configured to communicate with the base station 114a, which may employ a cellular-based radio technology, and with the base station 114b, which may employ an IEEE 802 radio technology.

[0032] Figure 1B is a system diagram illustrating an example WTRU 102. Figure 1B As shown, the WTRU 102 may include, among other things, a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and / or other peripherals 138. It will be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0033] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors associated with a DSP core, a controller, a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) circuit, any other type of integrated circuit (IC), a state machine, etc. The processor 118 may perform signal decoding, data processing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. Although Figure 1B The processor 118 and the transceiver 120 are depicted as separate components, but it is understood that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0034] The send / receive element 122 may be configured to send a signal to a base station (e.g., base station 114a) or receive a signal from a base station via an air interface 116. For example, in one embodiment, the send / receive element 122 may be an antenna configured to send and / or receive an RF signal. In an embodiment, the send / receive element 122 may be a transmitter / detector configured to send and / or receive, for example, an IR, UV, or visible light signal. In another embodiment, the send / receive element 122 may be configured to send and / or receive both an RF signal and an optical signal. It should be understood that the send / receive element 122 may be configured to send and / or receive any combination of wireless signals.

[0035] Although the transmit / receive element 122 Figure 1B Although depicted as a single element in the figure, the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may employ MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit / receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0036] The transceiver 120 may be configured to modulate signals to be transmitted by the transmit / receive element 122 and to demodulate signals received by the transmit / receive element 122. As noted above, the WTRU 102 may have multi-mode capabilities. For example, the transceiver 120 may include multiple transceivers for enabling the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11.

[0037] The processor 118 of the WTRU 102 may be coupled to and may receive user input data from a speaker / microphone 124, a keypad 126, and / or a display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light emitting diode (OLED) display unit). The processor 118 may also output user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. In addition, the processor 118 may access information from and store data in any type of suitable memory, such as a non-removable memory 130 and / or a removable memory 132. The non-removable memory 130 may include a random access memory (RAM), a read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, and a secure digital (SD) memory card, among others. In other embodiments, the processor 118 may access information from and store data in a memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0038] The processor 118 may receive power from the power source 134, and may be configured to distribute and / or control power to the other components in the WTRU 102. The power source 134 may be any suitable device for powering the WTRU 102. For example, the power source 134 may include one or more dry cell batteries (e.g., nickel cadmium (NiCd), nickel zinc (NiZn), nickel metal hydride (NiMH), lithium ion (Li-ion), etc.), solar cells, fuel cells, etc.

[0039] The processor 118 may also be coupled to the GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to or in lieu of the information from the GPS chipset 136, the WTRU 102 may receive location information from a base station (e.g., base stations 114a, 114b) over the air interface 116 and / or determine its location based on the timing of signals received from two or more nearby base stations. It will be appreciated that the WTRU 102 may acquire location information by any suitable location-determination method while remaining consistent with an embodiment.

[0040] The processor 118 may also be coupled to other peripherals 138, which may include one or more software modules and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos and / or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, module, FM radio unit, digital music player, media player, video game player module, Internet browser, virtual reality and / or augmented reality (VR / AR) device and activity tracker, etc. Peripheral device 138 may include one or more sensors, which may be one or more of the following: gyroscope, accelerometer, Hall effect sensor, magnetometer, orientation sensor, proximity sensor, temperature sensor, time sensor; geolocation sensor; altimeter, light sensor, touch sensor, magnetometer, barometer, gesture sensor, biometric sensor and / or humidity sensor.

[0041] The WTRU 102 may include a full-duplex radio for which transmission and reception of some or all signals (e.g., associated with specific subframes for both UL (e.g., for transmission) and downlink (e.g., for reception)) may be concurrent and / or simultaneous. The full-duplex radio may include an interference management unit 139 for reducing and / or substantially eliminating self-interference via signal processing performed by hardware (e.g., a choke) or via a processor (e.g., a separate processor (not shown) or via processor 118). In an embodiment, the WRTU 102 may include a half-duplex radio for which transmission and reception of some or all signals (e.g., associated with specific subframes for both UL (e.g., for transmission) or downlink (e.g., for reception)) may be concurrent and / or simultaneous.

[0042] Figure 1C 1 is a system diagram illustrating the RAN 104 and the CN 106 in accordance with an embodiment. As noted above, the RAN 104 may employ an E-UTRA radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0043] The RAN 104 may include evolved Node-Bs 160a, 160b, 160c, though it will be appreciated that the RAN 104 may include any number of evolved Node-Bs while remaining consistent with an embodiment. The evolved Node-Bs 160a, 160b, 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the evolved Node-Bs 160a, 160b, 160c may implement MIMO technology. Thus, the evolved Node-B 160a, for example, may use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a.

[0044] Each of the evolved Node Bs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, and scheduling of users in the UL and / or DL, among other things. Figure 1C As shown, the eNode-Bs 160a, 160b, 160c may communicate with one another via an X2 interface.

[0045] Figure 1C The illustrated CN 106 may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (or PGW) 166. While each of the foregoing elements is depicted as being part of the CN 106, it should be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0046] The MME 162 may be connected to each of the evolved Node-Bs 162a, 162b, 162c in the RAN 104 via an S1 interface and may serve as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, bearer activation / deactivation, and selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c. The MME 162 may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as GSM and / or WCDMA.

[0047] The SGW 164 may be connected to each of the evolved Node-Bs 160a, 160b, 160c in the RAN 104 via an S1 interface. The SGW 164 may generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions, such as anchoring the user plane during an inter-evolved Node-B handover, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, and managing and storing the context of the WTRUs 102a, 102b, 102c.

[0048] The SGW 164 may be connected to the PGW 166, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0049] The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. For example, the CN 106 may include, or may be in communication with, an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that acts as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired networks and / or wireless networks owned and / or operated by other service providers.

[0050] Although the WTRU Figures 1A to 1D Although described as wireless terminals, it is contemplated that in certain representative embodiments, such terminals may (eg, temporarily or permanently) use a wired communications interface with a communications network.

[0051] In a representative embodiment, the other network 112 may be a WLAN.

[0052] A WLAN in infrastructure basic service set (BSS) mode may have an access point (AP) for a BSS and one or more stations (STAs) associated with the AP. The AP may have access or an interface to a distribution system (DS) or another type of wired / wireless network that carries traffic to and / or carries traffic away from the BSS. Traffic originating from outside the BSS and destined for the STA may be reached by the AP and may be delivered to the STA. Traffic originating from the STA and destined for a target outside the BSS may be transmitted to the AP to be delivered to the corresponding target. Traffic between STAs within the BSS may be transmitted by the AP, for example, wherein the source STA may transmit traffic to the AP, and the AP may deliver traffic to the target STA. Traffic between STAs within the BSS may be considered and / or referred to as point-to-point traffic. Point-to-point traffic may be transmitted between the source STA and the target STA (e.g., directly between them) using a direct link setup (DLS). In certain representative embodiments, the DLS may use 802.11e DLS or 802.11z tunnel DLS (TDLS). A WLAN using an independent BSS (IBSS) mode may not have an AP, and STAs within or using the IBSS (eg, all STAs in the STA) may communicate directly with each other. The IBSS communication mode may sometimes be referred to herein as an "ad hoc" communication mode.

[0053] When using the 802.11ac infrastructure operation mode or a similar operation mode, the AP may send beacons on a fixed channel (such as a primary channel). The primary channel may be a fixed width (e.g., a 20MHz wide bandwidth) or a width dynamically set via signaling. The primary channel may be an operating channel of the BSS and may be used by the STA to establish a connection with the AP. In certain representative embodiments, carrier sense multiple access / collision avoidance (CSMA / CA) may be implemented, for example, in an 802.11 system. For CSMA / CA, a STA (e.g., each STA) (including the AP) may sense the primary channel. If the primary channel is sensed / detected and / or determined to be busy by a particular STA, the particular STA may back off. One STA (e.g., only one station) may transmit at any given time in a given BSS.

[0054] High throughput (HT) STAs may communicate using a 40 MHz wide channel (eg, via a combination of a primary 20 MHz channel and adjacent or non-adjacent 20 MHz channels) to form a 40 MHz wide channel.

[0055] Very high throughput (VHT) STA can support 20MHz, 40MHz, 80MHz and / or 160MHz wide channels. 40MHz channels and / or 80MHz channels can be formed by combining continuous 20MHz channels. 160MHz channels can be formed by combining 8 continuous 20MHz channels, or by combining two non-continuous 80MHz channels (this can be called 80+80 configuration). For 80+80 configuration, after channel coding, the data can pass through a segment parser that can divide the data into two streams. Each stream can be processed by inverse fast Fourier transform (IFFT) and time domain processing separately. These streams can be mapped to two 80MHz channels, and the data can be sent by the transmitter STA. At the receiver of the receiver STA, the above-mentioned operation for the 80+80 configuration can be reversed, and the combined data can be transmitted to the medium access control (MAC).

[0056] 802.11af and 802.11ah support operating modes below 1GHz. Channel operating bandwidths and carriers are reduced in 802.11af and 802.11ah relative to those used in 802.11n and 802.11ac. 802.11af supports 5MHz, 10MHz, and 20MHz bandwidths in the TV White Space (TVWS) spectrum, and 802.11ah supports 1MHz, 2MHz, 4MHz, 8MHz, and 16MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11ah may support instrument type control / machine type communications, such as MTC devices in macro coverage areas. MTC devices may have certain capabilities, such as limited capabilities, including support for (e.g., only support for) certain bandwidths and / or limited bandwidths. MTC devices may include batteries with battery life above a threshold (e.g., to maintain very long battery life).

[0057] WLAN systems that can support multiple channels and channel bandwidths (such as 802.11n, 802.11ac, 802.11af, and 802.11ah) include channels that can be designated as primary channels. The primary channel may have a bandwidth equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be set and / or limited by a STA (which supports the minimum bandwidth operating mode) from all STAs operating in the BSS. In the example of 802.11ah, for STAs (e.g., MTC-type devices) that support (e.g., only support) a 1MHz mode, the primary channel may be 1MHz wide, even if the AP and other STAs in the BSS support 2MHz, 4MHz, 8MHz, 16MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or network allocation vector (NAV) settings may depend on the state of the primary channel. If the primary channel is busy, for example, because a STA (supporting only a 1MHz operating mode) is transmitting to the AP, the entire available band may be considered busy even if most of the band remains idle and may be available.

[0058] In the United States, the available frequency band for 802.11ah is 902MHz to 928MHz. In South Korea, the available frequency band is 917.5MHz to 923.5MHz. In Japan, the available frequency band is 916.5MHz to 927.5MHz. The total bandwidth available for 802.11ah is 6MHz to 26MHz, depending on the country code.

[0059] Figure 1D1 is a system diagram illustrating the RAN 113 and the CN 115 in accordance with an embodiment. As noted above, the RAN 113 may employ NR radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 113 may also be in communication with the CN 115.

[0060] The RAN 113 may include gNBs 180a, 180b, 180c, though it will be appreciated that the RAN 113 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, 180c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, the gNBs 180a, 180b may utilize beamforming to send signals to and / or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a may, for example, use multiple antennas to send wireless signals to and / or receive wireless signals from the WTRU 102a. In an embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation technology. For example, gNB 180a may transmit multiple component carriers to WTRU 102a (not shown). A subset of these component carriers may be on unlicensed spectrum, while the remaining component carriers may be on licensed spectrum. In an embodiment, gNBs 180a, 180b, 180c may implement coordinated multi-point (CoMP) technology. For example, WTRU 102a may receive coordinated transmissions from gNB 180a and gNB 180b (and / or gNB 180c).

[0061] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with scalable parameter sets. For example, OFDM symbol spacing and / or OFDM subcarrier spacing may vary for different transmissions, different cells, and / or different portions of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using subframes or Transmission Time Intervals (TTIs) of varying or scalable lengths (e.g., containing varying numbers of OFDM symbols and / or varying absolute time lengths over time).

[0062] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c while not accessing other RANs (e.g., such as the eNodeBs 160a, 160b, 160c). In a standalone configuration, the WTRUs 102a, 102b, 102c may use one or more of the gNBs 180a, 180b, 180c as mobility anchor points. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration, the WTRUs 102a, 102b, 102c may communicate / connect with the gNB 180a, 180b, 180c while also communicating / connecting with another RAN, such as the eNodeB 160a, 160b, 160c. For example, the WTRUs 102a, 102b, 102c may implement the DC principle to communicate with one or more gNBs 180a, 180b, 180c and one or more eNodeBs 160a, 160b, 160c substantially simultaneously. In a non-standalone configuration, the eNodeB 160a, 160b, 160c may act as a mobility anchor for the WTRUs 102a, 102b, 102c, and the gNB 180a, 180b, 180c may provide additional coverage and / or throughput for serving the WTRUs 102a, 102b, 102c.

[0063] Each of the gNBs 180a, 180b, 180c may be associated with a specific cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in UL and / or DL, support of network slicing, dual connectivity, interworking between NR and E-UTRA, routing of user plane data towards a user plane function (UPF) 184a, 184b, routing of control plane information towards an access and mobility management function (AMF) 182a, 182b, etc. Figure 1D As shown, gNBs 180a, 180b, and 180c may communicate with each other via an Xn interface.

[0064] Figure 1DThe illustrated CN 115 may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one session management function (SMF) 183a, 183b, and possible data networks (DNs) 185a, 185b. Although each of the foregoing elements is depicted as part of the CN 115, it should be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0065] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via the N2 interface and may act as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRU 102a, 102b, 102c, support of network slicing (e.g., handling of different PDU sessions with different requirements), selecting a specific SMF 183a, 183b, management of registration areas, termination of NAS signaling and mobility management, etc. The AMF 182a, 182b may use network slicing to customize CN support for the WTRU 102a, 102b, 102c based on the type of services utilized by the WTRU 102a, 102b, 102c. For example, different network slices may be established for different use cases, such as services relying on Ultra Reliable Low Latency (URLLC) access, services relying on enhanced Mobile Broadband (eMBB) access, services for Machine Type Communication (MTC) access, etc. The AMF 162 may provide a control plane function for switching between the RAN 113 and other RANs (not shown) that employ other radio technologies, such as LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies, such as WiFi.

[0066] The SMF 183a, 183b may be connected to the AMF 182a, 182b in the CN 115 via the N11 interface. The SMF 183a, 183b may also be connected to the UPF 184a, 184b in the CN 115 via the N4 interface. The SMF 183a, 183b may select and control the UPF 184a, 184b, and 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, providing downlink data notification, etc. The PDU session type may be IP-based, non-IP-based, Ethernet-based, etc.

[0067] The UPF 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via the N3 interface, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPF 184, 184b may perform other functions, such as routing and forwarding packets, enforcing user plane policies, supporting multi-homed PDU sessions, handling user plane QoS, buffering downlink packets, providing mobility anchoring, etc.

[0068] The CN 115 may facilitate communications with other networks. For example, the CN 115 may include or may communicate with an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that acts as an interface between the CN 115 and the PSTN 108. In addition, the CN 115 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired networks and / or wireless networks owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to local data networks (DNs) 185a, 185b via the UPF 184a, 184b via the N3 interface to the UPF 184a, 184b and the N6 interface between the UPF 184a, 184b and the DN 185a, 185b.

[0069] Given that Figures 1A to 1D as well as Figures 1A to 1D Corresponding to the description of the present invention, one or more or all of the functions described herein with respect to one or more of the following items may be performed by one or more simulation devices (not shown): WTRU 102a-102d, base station 114a-114b, evolved Node B 160a-160c, MME 162, SGW 164, PGW 166, gNB 180a-180c, AMF182a-182ab, UPF 184a-184b, SMF 183a-183b, DN 185a-185b and / or any other device described herein. The simulation device may be one or more devices configured to mimic one or more or all of the functions described herein. For example, the simulation device may be used to test other devices and / or simulate network and / or WTRU functions.

[0070] The simulation device may be designed to implement one or more tests of other devices in a laboratory environment and / or in an operator network environment. For example, one or more simulation devices may perform one or more functions or all functions while being fully or partially implemented and / or deployed as part of a wired and / or wireless communication network in order to test other devices within the communication network. One or more simulation devices may perform one or more functions or all functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network. The simulation device may be directly coupled to another device for testing purposes and / or may use over-the-air wireless communications to perform testing.

[0071] One or more simulation devices can perform one or more (including all) functions without being implemented / deployed as part of a wired and / or wireless communication network. For example, the simulation device can be used in a test scenario in a test laboratory and / or a non-deployed (e.g., testing) wired and / or wireless communication network to implement testing of one or more components. One or more simulation devices can be test equipment. Direct RF coupling and / or wireless communication via RF circuits (e.g., which can include one or more antennas) can be used by the simulation device to send and / or receive data.

[0072] The WTRU may trigger / perform carrier selection and LCP by prioritizing a set of preferred carriers indicated by a peer WTRU. A transmitting WTRU (e.g., a TX WTRU) may receive a PC5 radio resource control (RRC) message from a peer WTRU indicating a set of preferred carriers. The TX WTRU may also receive a PC5-RRC message from a peer WTRU indicating a change in the set of preferred carriers.

[0073] After a unicast link is established or in a situation where the WTRU is transmitting to a peer WTRU using a carrier that may not be in the list of preferred carriers of the receiving WTRU (RX WTRU), a WTRU (e.g., a TX WTRU) may trigger a transmit carrier reselection procedure. After a unicast link is established or in a situation where the WTRU is transmitting to a peer WTRU using a carrier that may not be in the list of preferred carriers of the RX WTRU, a WTRU (e.g., a TX WTRU) may use a higher channel busy ratio (CBR) threshold to determine whether the carrier may be selected when there is a carrier in the list of preferred carriers of the RX WTRU. The TX WTRU may select a plurality of allowed carriers by, for example, starting with a carrier that is a preferred carrier of at least one peer WTRU in the unicast link and then in order of CBR. The TX WTRU may also inform the peer WTRU (e.g., using a PC5 radio resource control (RRC) message) which of the selected carriers, if any, may be the preferred carrier of the peer WTRU. The TX WTRU may select a sidelink grant on the selected carrier. If the grant occurs on a carrier that is not a preferred carrier of the peer WTRU, and the WTRU has selected at least one carrier in the set of preferred carriers of the peer WTRU, then the WTRU (e.g., the TX WTRU) may select a logical channel that may not be associated with the peer WTRU for transmission regarding the grant.

[0074] Vehicular communication may be a mode of communication whereby WTRUs may communicate directly with each other. For vehicle-to-everything (V2X) operations, there may be more than one scenario. One scenario may be an in-coverage scenario, where the WTRU may receive assistance from the network to start sending and receiving V2X messages. Another scenario may be an out-of-coverage scenario, where the WTRU may use one or more pre-configured parameters to start sending and receiving V2X messages.

[0075] V2X communications may be supported and may be inspired from operations associated with device-to-device (D2D) communications. V2X communication services may include different types: vehicle-to-vehicle (V2V), where vehicle WTRUs may communicate directly with each other; vehicle-to-infrastructure (V2I), where vehicle WTRUs may communicate with RSU / eNB; vehicle-to-network (V2N), where vehicle WTRUs may communicate with the core network; and vehicle-to-pedestrian (V2P), where vehicle WTRUs may communicate with WTRUs having special conditions (e.g., low battery capacity).

[0076] LTE may define two modes of operation in V2X communications. When in one mode (e.g., Mode 3), the network may provide the WTRU with scheduling assignments for V2X sidelink transmissions. When in one mode (e.g., Mode 4), the WTRU may autonomously select resources from a configured / pre-configured resource pool. V2X LTE may define one or more (e.g., two) categories of resource pools, such as a receive pool that may be monitored for receiving V2X transmissions, and a V2X transmit pool that may be used by the WTRU to select transmit resources in a mode (e.g., Mode 4). A WTRU configured to be in one mode (e.g., Mode 3) may not use a transmit pool.

[0077] In LTE, these resource pools may be semi-statically signaled to the WTRU via RRC signaling. In Mode 4, the WTRU uses sensing before selecting a resource in an RRC configured transmit pool. LTE V2X does not support dynamic resource pool reconfiguration; the pool configuration may only be carried via SIB and / or dedicated RRC signaling.

[0078] NR inherits two resource allocation modes from LTE. In NR, one mode (e.g., Mode 1) resource allocation may correspond to gNB-scheduled resource allocation. While in one mode (e.g., Mode 2), resource allocation may correspond to WTRU autonomous resource allocation. Both the concept of resource pools and sensing of Mode 2 resource allocation may be used.

[0079] For V2X sidelink communications, carrier aggregation (CA) in the sidelink may be supported. CA in the sidelink may be applicable to both in-coverage WTRUs and out-of-coverage WTRUs. For CA in the sidelink, neither a primary component carrier nor a secondary component carrier may be defined. Each resource pool that is (pre-)configured for V2X sidelink communication transmission and / or reception may be associated with a single carrier. When a WTRU supporting CA in the sidelink uses autonomous resource selection, the WTRU may perform carrier selection and may select one or more carriers that may be used for V2X sidelink communication transmission. Carrier selection may be performed at the MAC layer. Carrier selection may be performed at the MAC layer based on the CBR of the (pre-)configured carrier for V2X sidelink communication and the PPPP of the V2X message to be sent. Carrier reselection may be performed when resource reselection is triggered and / or for each sidelink process. In order to avoid frequent switching across different carriers, the WTRU may keep using the carrier if, for example, the CBR measured on the carrier that has been selected for transmission may be below a (pre-)configured threshold. All selected carriers may have the same synchronization reference and / or the same synchronization priority configuration.For a WTRU using autonomous resource selection, logical channel prioritization may be performed for sidelink resources on a carrier, for example, based on the CBR measured on the carrier and the PPPP of the sidelink logical channel.

[0080] In LTE, CA may be supported for broadcast (e.g., broadcast only). The transmit carrier may be selected by the TX WTRU based on the carrier configured by upper layers for the service being transmitted (i.e., L2 ID) and / or by taking the CBR into account (e.g., to ensure balanced use of resources).

[0081] Unicast operation may allow a WTRU to limit the number of carriers that the WTRU needs to monitor (and may, for example, limit power consumption) by agreeing with a peer WTRU on a subset (e.g., a smaller set) of carriers. In a system where the WTRU may use multiple unicast links, the number of carriers that any WTRU may need to monitor may become large and may exceed the capabilities of the WTRU. Coordination of the carriers used in a system that takes into account the carriers used by the WTRU in both unicast and multicast / broadcast may be required.

[0082] The TX WTRU and / or RX WTRU may coordinate carriers used for transmissions by the TX WTRU for transmissions to the RX WTRU and / or (e.g., also) for other transmissions (e.g., in unicast to other TX WTRUs and / or for groupcast / broadcast transmissions by the TX WTRU) (e.g., both). Carrier coordination may be part of a PC5-RRC reconfiguration procedure that may occur after a unicast link establishment procedure.

[0083] The TX WTRU may request a set of preferred carriers from the RX WTRU. For example, the TX WTRU may receive a message (e.g., a sidelink message such as a PC5 RRC reconfiguration message) from the RX WTRU indicating a set of preferred carriers for sidelink transmission. Alternatively or in combination, the RX WTRU may send (e.g., autonomously send) the set of preferred carriers of the RX WTRU to the TX WTRU based on a trigger as described herein.

[0084] After resource selection by the TX WTRU using the preferred carrier of the RX WTRU, the TX WTRU may indicate the actual selected carrier to the RX WTRU. The TX WTRU may send the actual selected carrier during (e.g., one, multiple, or all) carrier / resource (re)selection operations of the TX WTRU. Alternatively or in combination, the TX WTRU may send the selected carrier (e.g., only) in specific circumstances associated with carrier selection. The TX WTRU may indicate the selected carrier (e.g., only) when the TX WTRU may not be able to select the preferred carrier provided by the RX WTRU. When any or all of the preferred carriers do not meet other selection criteria discussed at the TX WTRU and / or herein, the TX WTRU may indicate the selected carrier and / or information related to the preferred carrier. After carrier / resource (re)selection, the TX WTRU may trigger a message to the RX WTRU for these purposes (e.g., and other purposes). Such a message may appear as a PC5 RRC reconfiguration message. In the event that the carrier selected by the TX WTRU is not acceptable to the RX WTRU and / or because the TX WTRU cannot transmit using some and / or all of the preferred carriers, the RX WTRU may transmit a reconfiguration failure message in response to the reconfiguration. If the RX WTRU transmits a reconfiguration failure message, the RX WTRU and / or the TX WTRU may assume one or more of the following: the unicast link is released; the RX WTRU and the TX WTRU may use a previous list of carriers agreed upon between them; the RX WTRU and the TX WTRU may use a default carrier or a subset of carriers agreed upon as default carriers; the RX WTRU and the TX WTRU may communicate using (e.g., only) a single carrier; and / or multiple carriers that may have been used may not be used if coordination was successful.

[0085] The RX WTRU may determine a list of preferred carriers to be transmitted to the TX WTRU. The RX WTRU may transmit the list of carriers to the TX WTRU. Such a list may be transmitted via PC5-S signaling using SL MAC CE, PC5-RRC signaling, and / or PHY layer signaling (e.g., SCI). The RX WTRU may transmit the list of used carriers via a combination of signaling. For example, (e.g., one or more or all) possible carriers may be transmitted via SL RRC signaling and / or configured by the network via UMTS air interface (e.g., Uu interface) RRC signaling. The RX WTRU may use MAC CE and / or PHY signaling to transmit a bitmap of preferred carriers to the TX WTRU. The RX WTRU may transmit the carrier that has changed since the last time a carrier was possibly transmitted to the TX WTRU (e.g., as incremental signaling).

[0086] An RX WTRU may refer to a WTRU that may be transmitting a list of preferred carriers (e.g., because the list of preferred carriers may be used by the WTRU (which may be referred to as a TX WTRU) to perform its own carrier selection). The RX WTRU may also schedule its own transmissions. The selection of a preferred carrier may involve criteria related to its own transmissions.

[0087] The list of preferred carriers may include carriers that the RX WTRU may prefer the TX WTRU to use for transmission on a unicast link with the TX WTRU (e.g., a preference may be indicated, but transmission on other carriers may still be possible). In an example, the list of preferred carriers may include carriers that the RX WTRU supports for reception. For example, the RX WTRU may receive (e.g., only receive) on a preferred carrier (e.g., and not on other carriers). The list of preferred carriers may include carriers that may be the best options for the TX WTRU to perform transmission on (e.g., from a performance, channel quality and / or interference perspective, etc.), for example, as determined by the RX WTRU. The list of preferred carriers referred to herein may consist of any one or more of the above-mentioned carriers.

[0088] In some examples, the list of preferred carriers may include carriers that may be the best options for the TX WTRU to perform transmissions on from a capabilities perspective at the RX WTRU. For example, the list of preferred carriers may include carriers that may be the best options for the TX WTRU to monitor on all carriers and / or other carriers that the RX WTRU may monitor on for other links / transmissions. This may be considered from a missed reception time perspective (e.g., outside of the preferred carriers, the RX WTRU may not be able to monitor certain carriers during certain time periods) and / or from a power saving perspective (e.g., outside of the preferred carriers, the RX WTRU may still be able to monitor, but may consume more power, switch, etc.). In some examples, the list of preferred carriers may include carriers that may already be monitored by the RX WTRU for other links and / or other services (e.g., multicast / broadcast). The RX WTRU may transmit a list of non-preferred carriers, which list of non-preferred carriers may be determined, for example, in a similar manner to the list of preferred carriers.

[0089] The TX WTRU may determine the preferred carrier using any or a combination of the following example criteria. For example, the TX WTRU may receive configuration information indicating carrier selection criteria. In one example criterion, a set of carriers may currently be monitored by the RX WTRU for other links and / or services. For example, the RX WTRU may transmit a list of carriers that are configured to be monitored by the RX WTRU for any unicast links and / or multicast services, etc.

[0090] In some examples, the criteria used to determine the preferred carrier (e.g., by the TX WTRU) may include SL measurement results (e.g., CBR, sidelink (SL) reference signal received power (RSRP), SL channel quality indicator (CQI), received signal strength indicator (RSSI), etc.). For example, the RX WTRU may transmit a set of carriers for which the SL CBR may be measured to be below a threshold. Alternatively or additionally, the RX WTRU may transmit a set of carriers for which the received measured SL RSRP / SL CQI may be above a threshold. Alternatively or additionally, the RX WTRU may transmit a set of carriers for which the received SL RSRP / SL CQI received from other WTRUs may be above a threshold (e.g., as measured by the other WTRUs).

[0091] In some examples, the criteria used to determine the preferred carriers (e.g., by the TX WTRU) may include the broadcast types associated with the expected reception / transmission on those carriers. For example, the RX WTRU may transmit a set of carriers on which it may perform reception of unicast and / or groupcast / broadcast (e.g., only unicast and / or only groupcast / broadcast). For example, any of the example criteria discussed herein may be specific to the reception of the broadcast type on that carrier. For example, the RX WTRU may transmit (e.g., only) one or more or all carriers with unicast reception that have a CBR above a threshold. For example, the RX WTRU may use a first threshold CBR for carriers with reception of one broadcast (e.g., only unicast reception). Alternatively or additionally, the RX WTRU may use a second CBR for carriers with reception of another broadcast (e.g., groupcast / broadcast reception). For example, the RX WTRU may transmit a list of carriers on which it may perform reception for one broadcast type that may meet one measurement criterion (e.g., the CBR may be above a threshold). Furthermore, alternatively or additionally, the RX WTRU may transmit a list of carriers on which it may perform reception of another broadcast type (eg, for which a different measurement criterion may be met (eg, SL RSRP may be above a threshold)).

[0092] In some examples, the criteria used to determine the preferred carriers (e.g., by the TX WTRU) may include a mode (e.g., Mode 1 versus Mode 2). For example, the RX WTRU may transmit the carriers on which the RX WTRU may perform its own transmission using Mode 1 or Mode 2. In the case where the RX WTRU may be configured with Mode 1 transmission, the RX WTRU may transmit a different set of carriers determined based on different criteria herein than in the case where the RX WTRU may be configured with Mode 2 transmission.

[0093] In some examples, criteria for determining a preferred carrier (e.g., by a TX WTRU) may include carriers on which a failure event may or may not have been observed within a recent (e.g., configured) possible time period. For example, the WTRU may transmit on a carrier on which a SL RLF may have been detected or may be detected, a preemption may have been triggered or may be triggered, a unicast link failure (e.g., a reconfiguration failure) may have occurred or may occur, etc.

[0094] In some examples, the criteria used to determine the preferred carrier (e.g., by the TX WTRU) may include sensing capabilities and / or sensing results. For example, a WTRU (e.g., an RX WTRU) may transmit carriers on which the WTRU may be able to perform sensing. The WTRU may transmit carriers on which the WTRU may perform a specific type of sensing (e.g., partial sensing versus full sensing). For example, the WTRU may transmit carriers for which the sensing results may meet certain specific criteria. For example, when performing sensing, the WTRU may be able to find a specific percentage of available resources.

[0095] In some examples, the criteria used to determine the preferred carrier (e.g., by the TX WTRU) may include the occupancy / traffic of the RX WTRU on the carrier used for transmission (e.g., from the perspective of the WTRU's own resource usage and / or number of links). For example, a WTRU (e.g., an RX WTRU) may transmit carriers whose CR may be above or below a threshold. The WTRU may transmit carriers on which the WTRU may have configured periodic HARQ processes. For example, the WTRU may transmit carriers on which the number of HARQ processes using the carrier may be above or below a threshold. The WTRU may transmit carriers on which the amount of SL resources used by the WTRU for transmission during the configured time period may be above a threshold. The WTRU may transmit carriers on which the number of unicast links using the carrier used for transmission may be above a threshold. The WTRU may transmit carriers that may be selected or may have been selected for its own transmission during a previous carrier selection process.

[0096] In some examples, criteria for determining a preferred carrier (e.g., by a TX WTRU) may include occupancy / traffic of the RX WTRU on the carrier for reception. For example, the WTRU may transmit a carrier on which the number of unicast links used by the RX WTRU when receiving may be above a threshold. The WTRU may transmit a carrier on which the number of received SL transmissions intended for the RX WTRU may be greater than a threshold.

[0097] As noted above, combinations of the above criteria are possible. For example, the RX WTRU may transmit a list of carriers that are configured to be monitored by the RX WTRU and for which the SL CBR may be below a threshold.

[0098] The RX WTRU may trigger the transmission of a set of preferred carriers. Such transmission may occur based on a specific trigger. For example, upon receiving an explicit / implicit request from the TX WTRU, the RX WTRU may transmit the set of preferred carriers. For example, an explicit request (e.g., via a PC5-RRC message) may be transmitted by the TX WTRU, where the RX WTRU may transmit the set of carriers. Alternatively or additionally, the RX WTRU may transmit the set of carriers based on the explicit request, such as in response to other messaging performed by the TX WTRU, such as one or more of the following: reception of a PC5 reconfiguration; reception of a CQI request; reception of a unicast release message; reception of an IUC (inter-WTRU coordination) request message. Alternatively or additionally, the RX WTRU may transmit the set of preferred carriers upon any change in the conditions / criteria used to determine the preferred carriers.

[0099] Alternatively or in combination, the RX WTRU may transmit the set of preferred carriers upon any change in the preferred carrier (relative to the last time the preferred carrier was transmitted to the TX WTRU). For example, the RX WTRU may transmit the set of preferred carriers upon a change in the preferred carrier that meets one or more criteria. In some examples, the one or more criteria include criteria based on the number of preferred carriers. For example, in a situation where the preferred carrier may have changed and the number of preferred carriers may be above a threshold. In some examples, the one or more criteria include criteria based on the addition or removal of carriers. For example, if the preferred carrier has changed and may have resulted in the addition of new carriers (e.g., only the addition of new carriers), the removal of carriers (e.g., only the removal of carriers), and / or the replacement of one carrier by another, etc. In some examples, the one or more criteria include criteria based on the number of changed carriers. For example, in a situation where the preferred carrier may have changed and / or the number of carriers that may have changed may be greater than a threshold. In some examples, the one or more criteria include criteria based on the carriers that may have changed. For example, in a situation where the preferred carrier has changed and the change may have occurred on one or more specific carriers. In some examples, the one or more criteria include a criterion that may be based on whether a carrier has changed relative to a carrier used / selected by the TX WTRU, for example, in a situation where the preferred carrier has changed and the change may affect one of the carriers selected by the TX WTRU and / or indicated to the RX WTRU.

[0100] The RX WTRU may be configured with periodic evaluation / determination of a preferred carrier. Alternatively or in combination, the RX WTRU may determine a preferred carrier and / or transmit a new preferred carrier to the TX WTRU upon the occurrence of any one or more of the following events. In some examples, the RX WTRU may determine a preferred carrier and / or transmit a new preferred carrier to the TX WTRU when the RX WTRU may perform carrier and / or resource selection for its own transmission. Alternatively or additionally, the RX WTRU may determine a preferred carrier and / or transmit a new preferred carrier to the TX WTRU when the RX WTRU initiates / completes a unicast link establishment with the TX WTRU and / or another WTRU.

[0101] In some examples, when the RX WTRU initiates / completes a sidelink reconfiguration, the RX WTRU may determine the preferred carrier and / or transmit the new preferred carrier to the TX WTRU. Alternatively or additionally, when the RX WTRU releases a unicast link with another WTRU, the RX WTRU may determine the preferred carrier and / or transmit the new preferred carrier to the TX WTRU. In some examples, when the RX WTRU receives a reconfiguration from the network, the RX WTRU may determine the preferred carrier and / or transmit the new preferred carrier to the TX WTRU, potentially providing a list of SL carriers to be used or a list of rules for determining the preferred carrier, etc. In other examples, when an event related to sensing on one or more of these carriers occurs (e.g., preemption is detected), the RX WTRU may determine the preferred carrier and / or transmit the new preferred carrier to the TX WTRU.

[0102] In some examples, when another WTRU detects a SL RLF, the RX WTRU may determine a preferred carrier and / or transmit a new preferred carrier to the TX WTRU. Alternatively or additionally, when the RX WTRU performs / completes an RRC connection / RRC connection fails, the RX WTRU may determine a preferred carrier and / or transmit a new preferred carrier to the TX WTRU. In some examples, when the RX WTRU receives an RRC connection release, the RX WTRU may determine a preferred carrier and / or transmit a new preferred carrier to the TX WTRU. In some examples, when the RX WTRU may be reconfigured in the event of any change in sidelink parameters (e.g., by the network and / or by a peer WTRU), the RX WTRU may determine a preferred carrier and / or transmit a new preferred carrier to the TX WTRU. In some examples, when any other event related to a change in the conditions for determining a preferred carrier described herein occurs, the RX WTRU may determine a preferred carrier and / or transmit a new preferred carrier to the TX WTRU.

[0103] The TX WTRU may trigger carrier reselection and / or resource reselection upon receiving a set of preferred carriers. The TX WTRU may trigger carrier / resource reselection when (e.g., only) one or more criteria associated with a carrier provided in the list of preferred carriers are met. The TX WTRU may trigger carrier reselection and / or resource reselection when the set of preferred carriers has changed compared to when the last set of preferred carriers was transmitted. The TX WTRU may trigger carrier reselection and / or resource reselection when the number of preferred carriers is different compared to when the last set of preferred carriers was transmitted.

[0104] The TX WTRU may trigger carrier reselection and / or resource reselection when there is a difference between the set of selected carriers and the received set of preferred carriers. For example, when the preferred carriers include one or at least X carriers that are not in the set of selected carriers, the TX WTRU may trigger carrier reselection and / or resource reselection. When the set of selected carriers does not include at least one or X carriers that are not in the preferred carriers, the TX WTRU may trigger carrier reselection and / or resource reselection. When the set of preferred carriers includes at least one carrier that meets the selection criteria, the TX WTRU may trigger carrier reselection and / or resource reselection. When the set of preferred carriers does not include any carrier that meets the selection criteria, the TX WTRU may trigger carrier reselection and / or resource reselection.

[0105] The TX WTRU may use a preferred carrier when performing carrier selection. For example, the TX WTRU may use a preferred carrier received from the RX WTRU when performing carrier selection. Carrier selection may refer to one or more of the following: determining allowable carriers for sending a specific L2 ID or multiple L2 IDs; determining an actual carrier for sending a specific L2 ID or multiple L2 IDs; selecting an actual carrier for sending from a set of allowable carriers; determining a specific carrier that may be used for unicast versus a carrier that may be used for multicast / broadcast; determining an amount of time that one or more carriers may be used for sending; selecting a set of carriers (e.g., a set of preferred carriers) to transmit to a peer WTRU (e.g., in a unicast link); and / or determining to exclude carriers for sending a specific L2 ID or multiple L2 IDs.

[0106] The TX WTRU may use the preferred carriers received from the RX WTRU to perform one or more of the following: The TX WTRU may use the preferred carriers received from the RX WTRU to prioritize the selection of preferred carriers during carrier selection. The TX WTRU may use the preferred carriers received from the RX WTRU to prioritize the preferred carriers during transmission to the RX WTRU. The TX WTRU may use the preferred carriers received from the RX WTRU to determine the number of carriers to select during carrier selection. During carrier selection, the TX WTRU may use the preferred carriers received from the RX WTRU to restrict the selected carriers to the preferred carriers, to a set of carriers that may include at least the preferred carrier, to a set of carriers that may not include any carriers other than the preferred carrier, to a set of carriers that may include at least X preferred carriers (e.g., where X may be 1 or may be configured or determined by the WTRU based on other criteria related to resource selection), and / or to a set of carriers that may not include (e.g., any) preferred carriers.

[0107] The TX WTRU may prioritize preferred carriers. For example, the TX WTRU may prioritize preferred carriers during carrier selection. Prioritization may mean selecting a preferred carrier first before selecting other carriers. Prioritization may consist of using different criteria / conditions for carriers that may be preferred carriers compared to carriers that may not be preferred carriers.

[0108] The TX WTRU may first select a preferred carrier before selecting other carriers. For example, the TX WTRU may determine the number of carriers for selection. If the number of carriers is greater than the set of preferred carriers, the TX WTRU may first select the preferred carrier and then select other carriers that may not be preferred carriers. For example, in the case where the number of carriers is less than the preferred carriers, the TX WTRU may (perhaps using another criterion) select only from the preferred carriers. In some examples, the TX WTRU may receive a set of preferred carriers from multiple WTRUs and may select from the preferred carriers that may be common to most WTRUs before selecting other carriers and / or carriers that may not be preferred carriers.

[0109] When selecting a carrier that may be a preferred carrier, the TX WTRU may prioritize the preferred carrier by using different selection criteria and / or conditions compared to selecting a carrier that may be a non-preferred criterion. For example, the TX WTRU may be allowed or may select a carrier based on a criterion and a condition about the criterion. For example, the TX WTRU may use any or a combination of the following criteria (and example criteria) to select a carrier. An example criterion used by the TX WTRU to select a carrier may be the CBR measured on the carrier. For example, if the measured CBR is below a threshold, the carrier may be allowed to be selected. An example criterion used by the TX WTRU to select a carrier may be the SL measurement results (e.g., RSRP / CQI) reported by a peer WTRU and / or measured by the WTRU. For example, if the measured RSRP / CQI is above a threshold, the carrier may be allowed to be selected. An example criterion used by the TX WTRU to select a carrier may be licensed versus unlicensed and / or based on LBT results for unlicensed. For example, if the number of LBT failures that have occurred in a (pre)configured past time period is less than a threshold number of times, the selection of an unlicensed carrier may be allowed. An example criterion used by the TX WTRU to select a carrier may be HARQ feedback. For example, if the HARQ feedback indicates that the ratio of ACK to NACK on the carrier is above a threshold, then selection of the carrier may be permitted. Example criteria used by the TX WTRU to select a carrier may include other criteria that may not be listed here but may exist.

[0110] In an example, based on the criteria and / or conditions, the TX WTRU may use a first set of criteria and / or conditions when evaluating whether to select a preferred carrier and use a second set of criteria and / or conditions when evaluating whether to select a carrier that may not be in the list of preferred carriers.

[0111] In some examples, the TX WTRU may use CBR to determine a list of allowed carriers from a list of supported carriers for transmission. For example, the TX WTRU may be configured with a first CBR threshold applied when evaluating a preferred carrier and a second CBR threshold applied when evaluating a non-preferred carrier. The TX WTRU may evaluate each supported carrier independently before selecting (e.g., one carrier at a time). When evaluating a particular carrier, the WTRU may first determine whether the particular carrier is a preferred carrier. If the carrier is a preferred carrier, the WTRU may compare the CBR measured on the carrier with a first threshold, and if the measured CBR is below the first threshold, the carrier may be declared allowed. If the carrier is a non-preferred carrier, the WTRU may compare the CBR measured on the carrier with a second threshold, and if the measured CBR is below the second threshold, the carrier may be declared allowed. The TX WTRU may use the same criteria described herein or other criteria to select a subset of allowed carriers from a list of allowed carriers.

[0112] In some examples, the TX WTRU may use different criteria on preferred carriers and non-preferred carriers to determine the list of allowed carriers from the list of supported carriers for transmission. For example, if the supported carrier is a preferred carrier, the TX WTRU may select the supported carrier if the RSRP measured by the peer WTRU on the carrier is above the RSRP threshold. In an example, if the supported carrier is not a preferred carrier, the TX WTRU may select the supported carrier if the measured CBR on the carrier is below the CBR threshold. In an example, for the list of allowed carriers, the TX WTRU may use the same criteria described herein or other criteria to select a subset of the allowed carriers.

[0113] In some examples, the TX WTRU may use criteria for selecting (e.g., only) on non-preferred carriers (e.g., or only on preferred carriers). For example, if the measured CBR is below a CBR threshold, the TX WTRU may allow selection of a non-preferred carrier (e.g., from a list of preferred carriers). In some examples, the same CBR evaluation may not be preferred on a preferred carrier. For a list of allowed carriers, the TX WTRU may use the same criteria described herein or other criteria to select a subset of allowed carriers.

[0114] The TX WTRU may prioritize preferred carriers when transmitting. The TX WTRU may prioritize preferred carriers during transmissions to a peer WTRU. For example, the TX WTRU may have multiple selected carriers on which to perform transmissions, where a subset of these carriers may be preferred carriers for one or more peer WTRUs. For example, a carrier may be a preferred carrier for a first peer WTRU, a second carrier may be a preferred carrier for the first peer WTRU and a second peer WTRU (e.g., either or both thereof), and / or a third carrier may not be a preferred carrier with respect to (e.g., one or more or any) peer WTRUs.

[0115] Grants on preferred carriers may be prioritized for transmission to peer WTRUs for which they are preferred for transmission. For example, for a grant on a preferred carrier associated with a first peer WTRU, if there is data available for transmission to the first peer WTRU, the TX WTRU may select data intended for the first peer WTRU before selecting any data for a second peer WTRU. In an example, if there is no data available for transmission to the first peer WTRU, the TX WTRU may use the grant to transmit data to the second peer WTRU. For a grant on a preferred carrier associated with the first peer WTRU, the TX WTRU may apply a higher priority to data available for transmission to the first peer WTRU than to data available for transmission to the second peer WTRU (e.g., an offset may be applied to the priority of the data available for transmission to make the data appear to have a higher priority).

[0116] For a grant on a non-preferred carrier, the TX WTRU may select data intended for a second peer WTRU (e.g., not associated with any preferred carrier) before selecting data intended for a first peer WTRU that may be associated with a preferred carrier. In an example, for a grant on a non-preferred carrier, the TX WTRU may apply a higher priority to data available for sending to a second peer WTRU that may not be associated with any preferred carrier (e.g., an offset may be applied to the priority of the data available for sending so that the data appears to have a higher priority) than data available for sending to a first peer WTRU associated with a preferred carrier, for example. In some examples, a grant on a preferred carrier may be available for (e.g., only for) sending to a WTRU associated with a preferred WTRU, and the grant may be discarded if no data is available for sending to any WTRU that has the carrier as a preferred carrier. In some examples, a grant on a non-preferred carrier may not be used to send data associated with a WTRU that may have provided a list of preferred carriers. The WTRU may select (e.g., only select) data associated with sending to a WTRU that may not have provided a preferred list of carriers (e.g., or L2 ID). In some examples, the above solution may be applicable to the following situations: the preferred carrier may correspond to the carrier agreed upon for transmission between two peer WTRUs in a unicast link, and / or the non-preferred carrier may include any other carrier (e.g., on which transmission of any broadcast type is possible). Therefore, the WTRU may select a carrier for unicast sidelink transmission with the RX WTRU, where the carrier is selected from the set of preferred carriers based on the condition that the first carrier meets the carrier selection criteria.

[0117] The TX WTRU may determine the number of carriers to select based on the preferred carriers. The TX WTRU may use the preferred carriers when determining the number of carriers to be selected. For example, the TX WTRU may determine the number of selected carriers such that the carriers include at least the preferred carriers of all peer WTRUs, and may determine the minimum number of selected carriers as the list of preferred carriers. The TX WTRU may determine the list of allowed carriers from the preferred carriers, and the TX WTRU may select at least a number of carriers including the allowed preferred carriers.

[0118] The TX WTRU may restrict the selected carriers based on preferred carriers. For example, the TX WTRU may select a set of carriers for transmission by restricting the selection based on a set of preferred carriers from one or more peer WTRUs. In some examples, the selected carriers may be restricted to (e.g., only) carriers indicated as preferred carriers by at least another WTRU. In addition, in some examples, the selected carriers may include at least all preferred carriers that may be indicated by all peer WTRUs. For example, the selected carriers may include at least X carriers among the preferred carriers. Assuming that the peer WTRU may transmit more than X carriers, the TX WTRU may select at least X carriers from the list of preferred carriers transmitted by the peer WTRU. For example, if the peer WTRU may not transmit more than X carriers, the TX WTRU may select one or more or all carriers indicated as preferred (e.g., possibly in the case where they meet some other criteria indicated herein). The value of X may be predetermined or may be configured (e.g., sent in the Uu RRC or in the PC5-RRC).

[0119] The value of X may further depend on any one or combination of the following. The value of X may depend on QoS. For example, the TX WTRU may determine the value of X based on the QoS of the transmission to the peer WTRU. For example, a side link radio bearer (SLRB) may be configured with a value of X, and the WTRU may use the maximum value of X for all SLRBs configured for transmission to the WTRU. The value of X may depend on the CBR. For example, the TX WTRU may be configured with a value of X for each CBR or CBR range measured on a set of carriers (e.g., the average CBR or maximum / minimum CBR on these carriers). The value of X may depend on the SL measurement results. For example, the TX WTRU may be configured with a value of X for each RSRP or RSRP range measured using a peer WTRU. The value of X may depend on the broadcast type. For example, the TX WTRU may be pre-configured with a value of X for each broadcast type (e.g., one value for unicast, a second value for groupcast, and so on).

[0120] The RX WTRU may transmit a list of preferred carriers. Such preferred carriers may represent a list of carriers that the RX WTRU is already monitoring. Specifically, the RX WTRU may transmit a list of carriers associated with the groupcast / broadcast L2 IDs that the RX WTRU may be interested in receiving, and, as an example, a list of carriers associated with all other unicast links established with other TX WTRUs. For a particular TX WTRU, the RX WTRU may transmit the list of preferred carriers after the PC5-RRC unicast is established with the TX WTRU. In addition, the RX WTRU may transmit the list of preferred carriers whenever the list of preferred carriers changes. If the RX WTRU releases a unicast link with another TX WTRU (which may result in a change in the list of carriers that the RX WTRU is monitoring), the RX WTRU may trigger the sending of a new list of preferred carriers by each of the TX WTRUs to which it is connected.

[0121] The TX WTRU may use a list of preferred carriers from one or more TX WTRUs in carrier (re)selection. The TX WTRU may perform an initial carrier selection based on one or more of these lists. Upon receiving a list of preferred carriers from the RX WTRU, the TX WTRU may trigger carrier reselection. The TX WTRU may trigger carrier reselection if none of the preferred carriers received from the RX WTRU is used as one of the carriers currently selected at the TX WTRU.

[0122] During carrier selection, the TX WTRU may select a set of carriers based on the CBR, and in an example, may use different CBR thresholds for carriers that may be preferred carriers and carriers that may not be preferred carriers. For example, the TX WTRU may determine the allowed carriers as a set of carriers whose CBR may be above a threshold. For example, the TX WTRU may use one CBR threshold for a carrier that is one of the carriers in the preferred set of carriers from any RX WTRU. And, the TX WTRU may use another CBR threshold for a carrier that may not be a preferred carrier for any RX WTRU.

[0123] After determining the allowed carriers, the TX WTRU may perform a selection of a set of carriers for transmission. For example, the TX WTRU may select from the allowed carriers which of the allowed carriers may be preferred carriers from the RX WTRU. For example, the TX WTRU may select at least X carriers from the allowed carriers (e.g., based on QoS). The selection may be performed in the order of lowest CBR to highest CBR until X carriers can be selected. The TX WTRU may then select additional carriers based on its own needs. For example, if the TX WTRU must transmit on a carrier that is not part of the preferred carrier, the TX WTRU may select additional allowed carriers to perform transmission to all multicast / broadcast services. In some examples, non-preferred carriers may also be selected in the order of lowest CBR to highest CBR. In some examples, the TX WTRU may select a carrier for broadcast (e.g., but different from the carrier selected for unicast with the RX WTRU) that is in the set of preferred carriers. After carrier selection, the TX WTRU may communicate the selected carriers, such as the carrier to be used for unicast sidelink transmissions and the carrier to be used for broadcast sidelink transmissions, to the RX WTRU (e.g., in PC5-RRC signaling). The TX WTRU may indicate the carriers that may be used by the TX WTRU to send data to the RX WTRU. For example, this may be limited to the carriers in the preferred carrier list if the carriers in the preferred carrier list are allowed carriers as determined by the TX WTRU.

[0124] After receiving the carriers used by the TX WTRU, the RX WTRU may determine whether the use of the carriers by the TX WTRU will result in exceeding the capabilities at the RX WTRU (e.g., the number of monitored carriers). If the use of the carriers by the TX WTRU will result in exceeding the capabilities at the RX WTRU (e.g., the number of monitored carriers), the RX WTRU may perform any one or a combination of the following: transmit an updated list of preferred carriers indicating a changed / reduced set of carriers to one or more TX WTRUs; transmit a connection reconfiguration failure to the TX WTRU, which may indicate the carriers being used in the unicast link.

[0125] Figure 22 is a flow chart of an example process 200 performed by a WTRU (e.g., a TX WTRU) for coordinating carrier usage in a multi-carrier sidelink. A WTRU (e.g., a TX WTRU) may perform process 200 to determine one or more carriers for communicating with one or more peer WTRUs via unicast and / or broadcast. At 202, the WTRU may receive a message (e.g., a sidelink message) from a peer RX WTRU indicating a set of preferred carriers for sidelink transmission. In some examples, the sidelink message may be a PC5-RRC reconfiguration message.

[0126] In addition, in some examples, the WTRU may receive configuration information indicating carrier selection criteria. The configuration information may configure the WTRU to select a carrier for communication with one or more peer WTRUs based on any combination of CBR, RSRP, LBT, HARQ, etc. For example, the carrier selection criteria may include a CBR threshold, and the WTRU may be configured to select the carrier from the set of preferred carriers based on the condition that the carrier has a CBR below the CBR threshold. In some examples, the carrier selection criteria may include an RSRP threshold, and the WTRU may be configured to select the carrier from the set of preferred carriers based on the condition that the carrier has a measured RSRP above the RSRP threshold. In some examples, the carrier selection criteria may include an LBT failure threshold, and the WTRU may be configured to select the carrier from the set of preferred carriers based on the condition that the carrier (e.g., within a preconfigured time period) has experienced LBT failures less than the LBT failure. In some examples, the carrier selection criteria may include a HARQ threshold, and the WTRU may be configured to select the carrier from the set of preferred carriers based on the condition that the carrier has a ratio of ACK to NACK above the HARQ threshold.

[0127] At 204, the WTRU may determine which of the preferred carriers are allowed carriers. The WTRU may determine whether a preferred carrier is an allowed carrier based on one or more criteria. For example, the WTRU may use any or a combination of the following criteria to select a carrier from the preferred carriers received at 202. An example criterion used by the WTRU to determine whether a carrier is an allowed carrier may be the CBR measured on the carrier. For example, if the measured CBR is below the CRB threshold, the WTRU may determine that the carrier is an allowed carrier. An example criterion used by the WTRU to determine whether a carrier is an allowed carrier may be the SL measurement results (e.g., RSRP and / or CQI) reported by a peer WTRU and / or measured by the WTRU. If the measured RSRP and / or CQI is above a threshold, the WTRU may determine that the carrier is an allowed carrier. An example criterion used by the WTRU to determine whether a carrier is an allowed carrier may be whether the carrier is in a licensed band and an unlicensed band and / or based on LBT results for carriers in unlicensed bands. If the number of LBT failures that have occurred within a (pre-)configured past time period is less than a threshold number of times, the WTRU may determine that the carrier is an allowed carrier. An example criterion used by the WTRU to determine whether a carrier is an allowed carrier may be HARQ feedback. If the HARQ feedback indicates that the ratio of ACK to NACK on the carrier is above a threshold, the WTRU may determine that the carrier is an allowed carrier. Example criteria used by the WTRU to select a carrier may include other criteria that may not be listed here but may exist.

[0128] At 206, the WTRU may select an allowed carrier in the preferred carrier list. For example, the WTRU may select at least one allowed carrier for unicast sidelink transmission with the peer RX WTRU (e.g., the WTRU that transmitted the list of preferred carriers at 202). In some examples, the WTRU may select the allowed carrier from the set of preferred carriers based on a condition that the allowed carrier satisfies the carrier selection criteria (e.g., received in the configuration information). Furthermore, in some examples, the WTRU may select the allowed carriers starting with the carriers that are preferred carriers for at least one peer WTRU in a unicast link and then in order of CBR.

[0129] At 208, the WTRU may determine whether the selected allowed carrier supports multicast / broadcast. If the WTRU determines that the selected allowed carrier supports groupcast / broadcast, then at 210, the WTRU may send data on the selected allowed carrier. If the WTRU determines that the selected allowed carrier does not support groupcast / broadcast, then the WTRU may select at least one allowed non-preferred carrier, for example, for broadcast sidelink transmission. In some examples, the WTRU may also transmit an indication of the selected carrier for unicast transmission and / or for broadcast transmission to the peer WTRU in a message (e.g., a PC5 RRC reconfiguration message). In this way, the WTRU may prioritize the preferred carrier for unicast sidelink transmissions of one or more peer WTRUs, and in the event that the preferred carrier is not suitable for broadcast sidelink transmission, the WTRU may select an additional carrier for broadcast transmission.

Claims

1. A first wireless transmit / receive unit (WTRU), the first wireless transmit / receive unit (WTRU) comprising: A processor and a transceiver, wherein the processor and the transceiver are configured to: receiving configuration information indicating carrier selection criteria; receiving a sidelink message from a second WTRU indicating a set of preferred carriers for sidelink transmission; selecting at least a first carrier for unicast sidelink transmission with the second WTRU, wherein the first carrier is selected from the set of preferred carriers based on a condition that the first carrier satisfies the carrier selection criterion; Determining that the first carrier cannot be used for broadcast side link transmission; selecting at least a second carrier for broadcast sidelink transmission, the second carrier not in the set of preferred carriers; as well as An indication of the selected first carrier and second carrier is transmitted to the second WTRU in a second message.

2. The first WTRU of claim 1 , wherein the processor and the transceiver are configured to: transmitting a unicast transmission to the second WTRU using the selected resources of the first carrier; and A multicast / broadcast transmission is transmitted using the selected resources of the second carrier.

3. The first WTRU of claim 1 , wherein the carrier selection criteria comprises a channel busy ratio (CBR) threshold, and wherein the first carrier is selected from the set of preferred carriers based on a condition that the first carrier has a CBR below the CBR threshold.

4. The first WTRU of claim 1 , wherein the carrier selection criteria comprises a received signal received power (RSRP) threshold, and wherein the first carrier is selected from the set of preferred carriers based on a condition that the first carrier has a measured RSRP that is above the RSRP threshold.

5. The first WTRU of claim 1 , wherein the carrier selection criteria comprises a listen-before-talk (LBT) failure threshold, and wherein the first carrier is selected from the set of preferred carriers based on a condition that the LBT failure experienced by the first carrier within a preconfigured time period is less than the LBT failure threshold.

6. The first WTRU of claim 1 , wherein the carrier selection criteria comprises a hybrid automatic repeat request (HARQ) threshold, and wherein the first carrier is selected from the set of preferred carriers based on a condition that the first carrier has a ratio of ACK to NACK that is above the HARQ threshold.

7. The first WTRU of claim 1 , wherein the processor and transceiver are configured to select the second carrier for broadcast sidelink transmission based on the second carrier having a lowest channel busy ratio (CBR) among a plurality of carriers, the plurality of carriers not being in the set of preferred carriers.

8. The first WTRU of claim 1 , wherein the processor and transceiver are configured to: receiving, from the second WTRU, a second sidelink message indicating a set of non-preferred carriers for sidelink transmissions, wherein the set of non-preferred carriers includes the second carrier; and The second carrier is selected for broadcast sidelink transmission based on a condition that the second carrier satisfies a second carrier selection criterion different from the carrier selection criterion used to select the first carrier for unicast sidelink transmission.

9. The first WTRU of claim 1 , wherein the sidelink message is a first PC5 RRC reconfiguration message, and wherein the indication is transmitted within a second PC5 RRC reconfiguration message.

10. A method performed by a first wireless transmit / receive unit (WTRU), the method comprising: receiving configuration information indicating carrier selection criteria; receiving a sidelink message from a second WTRU indicating a set of preferred carriers for sidelink transmission; selecting at least a first carrier for unicast sidelink transmission with the second WTRU, wherein the first carrier is selected from the set of preferred carriers based on a condition that the first carrier satisfies the carrier selection criterion; Determining that the first carrier cannot be used for broadcast side link transmission; selecting at least a second carrier for broadcast sidelink transmission, the second carrier not in the set of preferred carriers; as well as An indication of the selected first carrier and second carrier is transmitted to the second WTRU in a second message.

11. The method according to claim 10, further comprising: transmitting a unicast transmission to the second WTRU using the selected resources of the first carrier; as well as A multicast / broadcast transmission is transmitted using the selected resources of the second carrier.

12. The method of claim 10, wherein the carrier selection criteria comprises a channel busy ratio (CBR) threshold, and wherein the first carrier is selected from the set of preferred carriers based on a condition that the first carrier has a CBR below the CBR threshold.

13. The method of claim 10, wherein the carrier selection criteria comprises a received signal received power (RSRP) threshold, and wherein the first carrier is selected from the set of preferred carriers based on a condition that the first carrier has a measured RSRP above the RSRP threshold.

14. The method of claim 10, wherein the carrier selection criteria comprises a listen-before-talk (LBT) failure threshold, and wherein the first carrier is selected from the set of preferred carriers based on a condition that the LBT failure experienced by the first carrier within a preconfigured time period is less than the LBT failure threshold.

15. The method of claim 10, wherein the carrier selection criterion comprises a hybrid automatic repeat request (HARQ) threshold, and wherein the first carrier is selected from the set of preferred carriers based on a condition that the first carrier has a ratio of ACK to NACK above the HARQ threshold.

16. The method according to claim 10, further comprising: The second carrier is selected for broadcast sidelink transmission based on the second carrier having a lowest channel busy ratio (CBR) among a plurality of carriers that are not in the set of preferred carriers.

17. The method according to claim 10, further comprising: receiving, from the second WTRU, a second sidelink message indicating a set of non-preferred carriers for sidelink transmissions, wherein the set of non-preferred carriers includes the second carrier; as well as The second carrier is selected for broadcast sidelink transmission based on a condition that the second carrier satisfies a second carrier selection criterion different from the carrier selection criterion used to select the first carrier for unicast sidelink transmission.

18. The method of claim 10, wherein the sidelink message is a first PC5 RRC reconfiguration message, and wherein the indication is transmitted within a second PC5 RRC reconfiguration message.

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