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] This application is a divisional application of the invention patent application with the application date of August 5, 2023, application number 202380061439.2, and invention name “Coordinating Carrier Usage in Multi-Carrier Side Link”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] 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

[0004] In the 3rd Generation Partnership Project (3GPP) standards, a device-to-device direct communication link is referred to as a sidelink. Similar to the uplink and downlink, the sidelink also has control and data channels. The control channel in the sidelink is referred to as the Physical Sidelink Control Channel (PSCCH), and the data channel in the sidelink is referred to as the Physical Sidelink Shared Channel (PSSCH). The PSCCH can be used to indicate the time / frequency domain resource location, modulation and coding mode, and priority of data carried in the PSSCH, which is transmitted on the PSSCH, while the PSSCH can be used to carry data.

[0005] Control information and data in vehicle-to-vehicle / pedestrian / infrastructure / network or vehicle-to-everything (V2X) communications can be transmitted via a sidelink, and V2X communications can include two transmission modes: Transmission Mode 3 (Mode 3) and Transmission Mode 4 (Mode 4). In Mode 3, the transmission resources for the PSCCH and PSSCH of a WTRU (referred to as a V2X WTRU) are allocated by the evolved Node B (eNB). The WTRU determines the transmission resources for the PSCCH and PSSCH by receiving a sidelink resource allocation indication sent by the eNB via the Physical Downlink Control Channel (PDCCH) or enhanced PDCCH (EPDCCH). In Mode 4, the transmission resources for the PSCCH and PSSCH are autonomously selected by the WTRU based on channel detection results. 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

[0006] Aspects of the present disclosure relate to carrier coordination, and more particularly to carrier selection and resource selection in a multi-carrier sidelink.

[0007] A wireless transmit / receive unit (WTRU), such as a first WTRU, may include a processor and a transceiver. Furthermore, in some examples, the WTRU (e.g., the first WTRU) may be configured to perform a method comprising any combination of the following: The processor and the transceiver of the first WTRU may be configured to receive configuration information indicating carrier selection criteria. 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.

[0008] 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 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 and second carriers to the second WTRU in a second message. In some examples, the indication may be transmitted with a second PC5 RRC reconfiguration message.

[0009] 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.

[0010] 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 the condition that the first carrier has a CBR below the CBR threshold. Additionally, 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 the lowest CBR among a plurality of carriers that are not in the set of preferred carriers.

[0011] 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 first carrier having a measured RSRP above 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 first carrier experiencing LBT failures less than the LBT failure threshold within a preconfigured time period. 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 first carrier having an ACK to NACK ratio above the HARQ threshold.

[0012] 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.

[0013] In addition, in some examples, the present disclosure relates to a WTRU that includes a processor and a memory, the processor and the memory being 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.

[0014] The present disclosure also relates to a wireless transmit / receive unit (WTRU) (e.g., a first WTRU) comprising a processor and a transceiver, the processor and the transceiver being configurable to: receive configuration information indicating a carrier selection criterion; receive a sidelink message from a second WTRU indicating a set of preferred carriers for sidelink transmissions; select at least a first carrier for unicast sidelink transmissions 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; determine that the first carrier cannot be used for broadcast sidelink transmissions; select at least a second carrier for broadcast sidelink transmissions, the second carrier not in the set of preferred carriers; and transmit an indication of the selected first and second carriers to the second WTRU in a second message. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1A is a system diagram illustrating an example communication system in which one or more disclosed embodiments may be implemented.

[0016] 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 example communication system.

[0017] 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) used within an illustrated communication system.

[0018] 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.

[0019] Figure 2 is a flow diagram of an example process 200 performed by a WTRU for coordinating carrier usage in a multi-carrier sidelink. DETAILED DESCRIPTION

[0020] Figure 1Ais a diagram illustrating an example communication system 100 in which one or more disclosed embodiments may be implemented. Communication system 100 may be a multiple access system that provides content, such as voice, data, video, messaging, broadcast, etc., to multiple wireless users. Communication system 100 may enable multiple wireless users to access such content by sharing system resources, including wireless bandwidth. For example, 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-tailing 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).

[0021] like Figure 1A As 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, the Internet 110, and other networks 112. However, it should be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network 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 UEs 102a, 102b, 102c, 102d (any of which may be referred to as a “station” and / or “STA”) may be configured to transmit and / or receive wireless signals and may include user equipment (WTRUs), mobile stations, fixed or mobile subscriber units, subscription-based units, pagers, cellular phones, personal digital assistants (PDAs), smartphones, laptops, netbooks, personal computers, wireless sensors, hotspot or Mi-Fi devices, Internet of Things (IoT) devices, watches or other wearable devices, head-mounted displays (HMDs), vehicles, drones, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in industrial and / or automated process chain environments), consumer electronic devices, devices operating on commercial and / or industrial wireless networks, etc. Any of the WTRUs 102a, 102b, 102c, and 102d may be interchangeably referred to as UEs.

[0022] The communication system 100 may also include a base station 114a and / or a base station 114b. Each of the base stations 114a, 114b may be any type of device configured to interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the CNs 106 / 115, the Internet 110, and / or other networks 112. By way of example, the base stations 114a, 114b may be base transceiver stations (BTSs), Node-Bs, eNode-Bs, Home Node-Bs, Home eNode-Bs, gNBs, NR Node-Bs, site controllers, access points (APs), wireless routers, and the like. While the base stations 114a, 114b are each depicted as a single element, it should be understood that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0023] Base station 114a may be part of the RAN 104 / 113, which may also include other base stations and / or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), relay nodes, etc. Base station 114a and / or base station 114b may be configured to transmit and / or receive wireless signals on one or more carrier frequencies, which may be referred to as cells (not shown). These frequencies may be in licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide wireless service coverage 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. Thus, in one embodiment, base station 114a may include three transceivers, one for each sector of the cell. In one 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 transmit and / or receive signals in a desired spatial direction.

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

[0025] More specifically, as 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. For example, the base station 114a in the RAN 104 / 113 and the WTRUs 102a, 102b, 102c may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may use Wideband CDMA (WCDMA) to establish the air interface 115 / 116 / 117. WCDMA may include communication protocols such as High Speed ​​Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High Speed ​​Downlink (DL) Packet Access (HSDPA) and / or High Speed ​​UL Packet Access (HSUPA).

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

[0027] 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).

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

[0029] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology 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).

[0030] Figure 1A The base station 114b in the may be, for example, a wireless router, a Home NodeB, a Home eNodeB, or an access point, and may utilize any suitable RAT to facilitate wireless connectivity in a local area, such as a business, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), and a road. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In an embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In 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 femtocell. Figure 1A As shown, base station 114b may have a direct connection to the Internet 110. Therefore, base station 114b may not need to access the Internet 110 via CN 106 / 115.

[0031] The RAN 104 / 113 may be in communication with the CN 106 / 115, which may be any type of network configured to provide voice, data, applications, and / or Voice over Internet Protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. Data may have different quality of service (QoS) requirements, such as different throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, and mobility requirements. The CN 106 / 115 may provide call control, billing services, mobile location-based services, prepaid calling, Internet connectivity, video distribution, etc., and / or perform advanced security functions, such as user authentication. Although not described in Figure 1AAlthough 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.

[0032] The CN 106 / 115 may also act as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or other networks 112. The PSTN 108 may include a circuit-switched telephone network that provides plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols, such as Transmission Control Protocol (TCP), User Datagram Protocol (UDP), and / or Internet Protocol (IP) from 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.

[0033] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communication system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks 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.

[0034] 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 supply 134, a global positioning system (GPS) chipset 136, and / or other peripherals 138. It will be appreciated that the WTRU 102 may include any subcombination of the foregoing elements while remaining consistent with an embodiment.

[0035] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors associated with a DSP core, a controller, a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) circuit, any other type of integrated circuit (IC), a state machine, 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.

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

[0037] Although the transmit / receive element 122 Figure 1B Although depicted as a single element in FIG. 1 , 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.

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

[0039] The processor 118 of the WTRU 102 may be coupled to and may receive user input data from the speaker / microphone 124, keypad 126, and / or 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, keypad 126, and / or display / touchpad 128. Furthermore, the processor 118 may access information from and store data in any suitable type of memory, such as non-removable memory 130 and / or removable memory 132. Non-removable memory 130 may include random access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. Removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, and the like. In other embodiments, the processor 118 may access information from and store data in memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0040] The processor 118 may receive power from the power source 134 and may be configured to distribute and / or control power 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.

[0041] The processor 118 may also be coupled to the GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) 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.

[0042] The processor 118 may also be coupled to other peripherals 138, which may include one or more software modules and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos and / or video), a Universal Serial Bus (USB) port, a vibration device, a television transceiver, a hands-free headset, a Bluetooth ® module, a frequency modulation (FM) radio unit, a digital music player, a media player, a video game player module, an internet browser, a virtual reality and / or augmented reality (VR / AR) device, and an activity tracker, etc. The peripheral device 138 may include one or more sensors, which may be one or more of the following: a gyroscope, an accelerometer, a Hall effect sensor, a magnetometer, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor; a geolocation sensor; an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, a gesture sensor, a biometric sensor, and / or a humidity sensor.

[0043] 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 by a processor (e.g., a separate processor (not shown) or by the processor 118). In an embodiment, the WTRU 102 may include a half-duplex radio 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.

[0044] 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 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.

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

[0046] Each of the eNodeBs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, 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.

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

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

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

[0050] 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.

[0051] The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. For example, the CN 106 may include, or 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. Furthermore, 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.

[0052] Even though 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) employ a wired communication interface with a communication network.

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

[0054] A WLAN in infrastructure basic service set (BSS) mode may have an access point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP may have access to or an interface with a distribution system (DS) or another type of wired / wireless network that carries traffic to and / or from the BSS. Traffic originating from outside the BSS and destined for a STA can reach the AP and be delivered to the STA. Traffic originating from a STA and destined for a destination outside the BSS can be transferred to the AP for delivery to the destination. Traffic between STAs within the BSS can be transferred through the AP, for example, where a source STA can transmit traffic to the AP, and the AP can deliver the traffic to the destination STA. Traffic between STAs within the BSS may be considered and / or referred to as peer-to-peer traffic. Peer-to-peer traffic can be transferred between a source STA and a destination STA (e.g., directly between them) using direct link setup (DLS). In certain representative embodiments, DLS may use 802.11e DLS or 802.11z tunneled DLS (TDLS). A WLAN using 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.

[0055] When using 802.11ac infrastructure mode of operation or a similar mode of operation, the AP may transmit beacons on a fixed channel, such as the primary channel. The primary channel may have a fixed width (e.g., a 20 MHz wide bandwidth) or a width dynamically set via signaling. The primary channel may be the operating channel of the BSS and may be used by STAs to establish connections with the AP. In certain representative embodiments, such as in an 802.11 system, Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) may be implemented. With CSMA / CA, STAs (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, that particular STA may back off. One STA (e.g., only one station) may transmit in a given BSS at any given time.

[0056] 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.

[0057] Very High Throughput (VHT) STAs can support 20 MHz, 40 MHz, 80 MHz, and / or 160 MHz wide channels. 40 MHz and / or 80 MHz channels can be formed by combining contiguous 20 MHz channels. A 160 MHz channel can be formed by combining eight contiguous 20 MHz channels or by combining two non-contiguous 80 MHz channels (this is referred to as an 80+80 configuration). For the 80+80 configuration, after channel coding, the data passes through a segment parser that separates the data into two streams. Each stream is individually processed using an inverse fast Fourier transform (IFFT) and time domain processing. These streams are mapped to two 80 MHz channels, and the data can be transmitted by the transmitting STA. At the receiving STA's receiver, the operations described above for the 80+80 configuration are reversed, and the combined data is passed to the media access control (MAC).

[0058] 802.11af and 802.11ah support sub-1 GHz operating modes. 802.11af and 802.11ah reduce the channel operating bandwidth and carriers used in 802.11n and 802.11ac. 802.11af supports 5 MHz, 10 MHz, and 20 MHz bandwidths in the TV White Space (TVWS) spectrum, while 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. According to representative embodiments, 802.11ah can support meter-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) certain bandwidths and / or limited bandwidth. MTC devices may also include batteries with battery life exceeding a threshold (e.g., to maintain very long battery life).

[0059] WLAN systems that support multiple channels and channel bandwidths (such as 802.11n, 802.11ac, 802.11af, and 802.11ah) include a channel that can be designated as a primary channel. 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 the STA (which supports the minimum bandwidth operating mode) from among all STAs operating in the BSS. In the example of 802.11ah, for a STA (e.g., an MTC-type device) that supports (e.g., only) 1 MHz mode, the primary channel may be 1 MHz wide, even if the AP and other STAs in the BSS support 2 MHz, 4 MHz, 8 MHz, 16 MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or network allocation vector (NAV) settings may depend on the status of the primary channel. If the primary channel is busy, for example, because a STA (supporting only 1 MHz operating mode) is transmitting to the AP, the entire available frequency band may be considered busy, even if most of the frequency band remains idle and potentially available.

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

[0061] Figure 1D 1 is a system diagram illustrating the RAN 113 and the CN 115 according to 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.

[0062] The RAN 113 may include gNBs 180a, 180b, and 180c, though it will be appreciated that the RAN 113 may include any number of gNBs while remaining consistent with an embodiment. Each of the gNBs 180a, 180b, and 180c may include one or more transceivers for communicating with the WTRUs 102a, 102b, and 102c over the air interface 116. In one embodiment, the gNBs 180a, 180b, and 180c may implement MIMO technology. For example, the gNBs 180a and 180b may utilize beamforming to transmit signals to and / or receive signals from the gNBs 180a, 180b, and 180c. Thus, the gNB 180a may, for example, use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a. In one embodiment, the gNBs 180a, 180b, and 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, and 180c may implement coordinated multi-point (CoMP) technology. For example, WTRU 102a may receive coordinated transmissions from gNB 180a and gNB 180b (and / or gNB 180c).

[0063] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with scalable parameter sets. For example, the 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).

[0064] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c 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 eNode-B 160a, 160b, 160c. For example, the WTRUs 102a, 102b, 102c may implement DC principles to communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c substantially simultaneously. In a non-standalone configuration, the eNode-B 160a, 160b, 160c may serve 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.

[0065] 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 user plane functions (UPFs) 184a, 184b, routing of control plane information towards access and mobility management functions (AMFs) 182a, 182b, etc. Figure 1D As shown, gNBs 180a, 180b, and 180c can communicate with each other via the Xn interface.

[0066] 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 possibly data networks (DNs) 185a, 185b. While each of the aforementioned 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.

[0067] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via the N2 interface and may act as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, supporting network slicing (e.g., handling of different PDU sessions with different requirements), selecting a specific SMF 183a, 183b, managing registration areas, terminating NAS signaling, and mobility management. The AMF 182a, 182b may use network slicing to customize CN support for the WTRUs 102a, 102b, 102c based on the type of services utilized by the WTRUs 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.

[0068] The SMFs 183a and 183b can connect to the AMFs 182a and 182b in the CN 115 via the N11 interface. The SMFs 183a and 183b can also connect to the UPFs 184a and 184b in the CN 115 via the N4 interface. The SMFs 183a and 183b can select and control the UPFs 184a and 184b and configure traffic routing through the UPFs 184a and 184b. The SMFs 183a and 183b can perform other functions, such as managing and allocating UE IP addresses, managing PDU sessions, controlling policy enforcement and QoS, and providing downlink data notifications. PDU session types can be IP-based, non-IP-based, Ethernet-based, and so on.

[0069] 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, and the like.

[0070] The CN 115 may facilitate communications with other networks. For example, the CN 115 may include, or may communicate with, an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that acts as an interface between the CN 115 and the PSTN 108. Furthermore, 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 connect to local data networks (DNs) 185a, 185b through UPFs 184a, 184b via the N3 interface to the UPFs 184a, 184b and the N6 interface between the UPFs 184a, 184b and the local data networks (DNs) 185a, 185b.

[0071] Given that Figures 1A to 1D as well as Figures 1A to 1D As described herein, one or more or all of the functionality described herein with respect to one or more of the following may be performed by one or more emulated devices (not shown): the WTRUs 102a-102d, base stations 114a-114b, eNodeBs 160a-160c, MMEs 162, SGWs 164, PGWs 166, gNBs 180a-180c, AMFs 182a-182ab, UPFs 184a-184b, SMFs 183a-183b, DNs 185a-185b, and / or any other devices described herein. An emulated device may be one or more devices configured to emulate one or more or all of the functionality described herein. For example, an emulated device may be used to test other devices and / or simulate network and / or WTRU functionality.

[0072] Emulated devices can be designed to implement one or more tests of other devices in a laboratory environment and / or in a carrier network environment. For example, one or more emulated devices can 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 emulated devices can perform one or more functions or all functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network. The emulated device can be directly coupled to another device for testing purposes and / or can use over-the-air wireless communications to perform testing.

[0073] One or more emulated 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 emulated devices can be used in a test lab and / or in a test scenario where a wired and / or wireless communication network is not deployed (e.g., testing) to enable testing of one or more components. The one or more emulated devices can be test equipment. Direct RF coupling and / or wireless communication via RF circuitry (e.g., which may include one or more antennas) can be used by the emulated devices to send and / or receive data.

[0074] 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.

[0075] After a unicast link is established or when a WTRU is transmitting to a peer WTRU using a carrier that may not be in the receiver WTRU's (RX WTRU) list of preferred carriers, a WTRU (e.g., a TX WTRU) may trigger a transmit carrier reselection procedure. After a unicast link is established or when a WTRU is transmitting to a peer WTRU using a carrier that may not be in the RX WTRU's list of preferred carriers, a WTRU (e.g., a TX WTRU) may use a higher channel busy ratio (CBR) threshold to determine whether the carrier is selectable when a carrier is in the RX WTRU's list of preferred carriers. The TX WTRU may select multiple allowed carriers by, for example, starting with a carrier that is the preferred carrier of at least one peer WTRU in the unicast link and then following the order of CBR. The TX WTRU may also inform the peer WTRU (e.g., using a PC5 radio resource control (RRC) message) which, if any, of the selected carriers may be the peer WTRU's preferred carrier. 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.

[0076] Vehicular communication may be a communication mode whereby WTRUs can 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 begin 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 begin sending and receiving V2X messages.

[0077] V2X communications may be supported and may be inspired by 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 RSUs / eNBs; 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 with special conditions (e.g., low battery capacity).

[0078] LTE may define two modes of operation for 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 / preconfigured 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 operate in one mode (e.g., Mode 3) may not utilize a transmit pool.

[0079] 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 the 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.

[0080] NR inherits two resource allocation modes from LTE. In NR, one mode (e.g., Mode 1) may correspond to gNB-scheduled resource allocation. In another mode (e.g., Mode 2), resource allocation may correspond to WTRU-autonomous resource allocation. Both the resource pool concept and sensing of Mode 2 resource allocation may be used.

[0081] For V2X sidelink communications, carrier aggregation (CA) in the sidelink may be supported. CA in the sidelink may be applicable to both in-coverage and out-of-coverage WTRUs. For CA in the sidelink, neither a primary nor a secondary component carrier may be defined. Each resource pool (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 available 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 carriers used for V2X sidelink communications and the PPPP of the V2X message to be transmitted. Carrier reselection may be performed when resource reselection is triggered and / or for each sidelink procedure. To avoid frequent switching across different carriers, the WTRU may remain on a carrier already selected for transmission, for example, if the CBR measured on that carrier 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.

[0082] 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 CBR into account (e.g., to ensure balanced use of resources).

[0083] Unicast operation may allow a WTRU to limit the number of carriers it needs to monitor (and, for example, may 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 carrier use in a system may be required that takes into account carrier use by the WTRU in both unicast and multicast / broadcast scenarios.

[0084] The TX WTRU and / or the 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 transmissions 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.

[0085] 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) the set of preferred carriers of the RX WTRU to the TX WTRU based on a trigger as described herein.

[0086] After the TX WTRU performs resource selection using the RX WTRU's preferred carrier, the TX WTRU may indicate the actual selected carrier to the RX WTRU. The TX WTRU may send the actual selected carrier during the TX WTRU's (e.g., one, multiple, or all) carrier / resource (re)selection operation. 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. The TX WTRU may indicate the selected carrier and / or information related to the preferred carrier when any or all of the preferred carriers do not meet other selection criteria at the TX WTRU and / or as discussed herein. After carrier / resource (re)selection, the TX WTRU may trigger a message to the RX WTRU for these purposes (e.g., and others). Such a message may appear as a PC5 RRC reconfiguration message. In a situation where 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 the 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 that was agreed upon between them; the RX WTRU and the TX WTRU may use a default carrier or a subset of carriers that were agreed upon as the default carrier; 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.

[0087] 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 SL using SL MAC CE, PC5-RRC signaling, and / or PC5-S signaling of PHY layer signaling (e.g., SCI). The RX WTRU may transmit the list of carriers to be used 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 transmit a bitmap of preferred carriers to the TX WTRU using MAC CE and / or PHY signaling. The RX WTRU may transmit carriers that have changed since the last possible carrier was transmitted to the TX WTRU (e.g., as incremental signaling).

[0088] 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.

[0089] 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 the 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 transmit on (e.g., from a performance, channel quality, and / or interference perspective), 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 carriers described above.

[0090] 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 across all carriers and / or other carriers that the RX WTRU may monitor 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 may be determined, for example, in a similar manner as the list of preferred carriers.

[0091] The TX WTRU may use any or a combination of the following example criteria to determine a preferred carrier. For example, the TX WTRU may receive configuration information indicating carrier selection criteria. In one example criterion, a set of carriers may be currently 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.

[0092] 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).

[0093] In some examples, the criteria used to determine preferred carriers (e.g., by the TX WTRU) may include the broadcast types associated with the intended reception / transmission on those carriers. For example, the RX WTRU may transmit a set of carriers on which it may perform unicast and / or multicast / broadcast reception (e.g., only unicast and / or only multicast / broadcast). For example, any of the example criteria discussed herein may be specific to the type of broadcast reception 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 one type of broadcast reception (e.g., only unicast reception). Alternatively or additionally, the RX WTRU may use a second CBR for carriers with another type of broadcast reception (e.g., multicast / broadcast reception). For example, the RX WTRU may transmit a list of carriers on which it may perform reception for a type of broadcast that may meet a measurement criterion (e.g., a 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 different measurement criteria may be met (eg, SL RSRP may be above a threshold)).

[0094] In some examples, the criteria used to determine the preferred carrier (e.g., by the TX WTRU) may include a mode (e.g., Mode 1 versus Mode 2). For example, the RX WTRU may use Mode 1 or Mode 2 to transmit the carriers on which the RX WTRU may perform its own transmission. 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.

[0095] In some examples, criteria used to determine 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 an SL RLF may have been detected or may be detected, 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.

[0096] In some examples, the criteria used to determine a preferred carrier (e.g., by a TX WTRU) may include sensing capabilities and / or sensing results. For example, a WTRU (e.g., a 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 sensing results may meet certain criteria. For example, when performing sensing, the WTRU may be able to find a specific percentage of available resources.

[0097] 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 being 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., the 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 a 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 a configured time period may be above a threshold. The WTRU may transmit carriers on which the number of unicast links using the carrier being used for transmission may be above a threshold. The WTRU may transmit carriers that may have been selected or may have been selected for its own transmission during a previous carrier selection procedure.

[0098] In some examples, criteria used to determine a preferred carrier (e.g., by a TX WTRU) may include occupancy / traffic of the RX WTRU on the carrier used for reception. For example, the WTRU may transmit on a carrier on which the number of unicast links used by the RX WTRU for reception may be above a threshold. The WTRU may transmit on a carrier on which the number of received SL transmissions intended for the RX WTRU may be above a threshold.

[0099] 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.

[0100] The RX WTRU may trigger the transmission of the set of preferred carriers. Such transmission may occur based on a specific trigger. For example, the RX WTRU may transmit the set of preferred carriers upon receiving an explicit / implicit request from the TX WTRU. For example, an explicit request (e.g., via a PC5-RRC message) may be transmitted by the TX WTRU, wherein 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 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.

[0101] 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 situations 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 with another. In some examples, the one or more criteria include criteria based on the number of carriers that may have changed. For example, in situations where the preferred carrier may have changed and / or the number of carriers that may have changed may be above a threshold. In some examples, the one or more criteria include criteria based on the carriers that may have changed. For example, in situations where the preferred carrier may have changed and the change may have occurred on one or more specific carriers. In some examples, the one or more criteria may include a criterion based on whether a carrier has changed relative to a carrier used / selected by the TX WTRU, for example, where a 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.

[0102] 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 communicate 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 communicate 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 in addition, the RX WTRU may determine a preferred carrier and / or communicate 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.

[0103] In some examples, when the RX WTRU initiates / completes a sidelink reconfiguration, the RX WTRU may determine a preferred carrier and / or communicate a 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 a preferred carrier and / or communicate a 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 a preferred carrier and / or communicate a new preferred carrier to the TX WTRU, potentially providing a list of SL carriers to use 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 the carriers occurs (e.g., preemption is detected), the RX WTRU may determine a preferred carrier and / or communicate a new preferred carrier to the TX WTRU.

[0104] In some examples, the RX WTRU may determine a preferred carrier and / or transmit a new preferred carrier to the TX WTRU when another WTRU detects a SL RLF. 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 performs / completes an RRC connection / RRC connection fails. 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 receives an RRC connection release. 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 be reconfigured in the event of any change in sidelink parameters (e.g., by the network and / or by a peer WTRU). In some examples, the RX WTRU may determine a preferred carrier and / or transmit a new preferred carrier to the TX WTRU when any other event occurs related to a change in the conditions for determining a preferred carrier as described herein.

[0105] 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 (e.g., only) when 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 since 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 than when the last set of preferred carriers was transmitted.

[0106] The TX WTRU may trigger carrier reselection and / or resource reselection when there is a discrepancy 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.

[0107] 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 transmitting a particular L2 ID or IDs; determining an actual carrier for transmitting a particular L2 ID or IDs; selecting an actual carrier for transmitting from a set of allowable carriers; determining a particular carrier available for unicast versus a carrier available for multicast / broadcast; determining an amount of time that one or more carriers are available for transmission; 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 a carrier to exclude from transmitting a particular L2 ID or IDs.

[0108] 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 selection of preferred carriers during carrier selection. The TX WTRU may use the preferred carriers received from the RX WTRU to prioritize preferred carriers during transmission to the RX WTRU. The TX WTRU may use the preferred carriers received from the RX WTRU to determine a 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 limit 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.

[0109] The TX WTRU may prioritize preferred carriers. For example, the TX WTRU may prioritize preferred carriers during carrier selection. Prioritization may mean selecting the preferred carrier first before selecting other carriers. Prioritization may consist of applying different criteria / conditions to carriers that may be preferred compared to carriers that may not be preferred.

[0110] The TX WTRU may first select a preferred carrier before selecting other carriers. For example, the TX WTRU may determine the number of carriers to select from. 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 set of 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 a preferred carrier that may be common to most WTRUs before selecting other carriers and / or carriers that may not be preferred carriers.

[0111] When selecting a carrier that may be a preferred carrier, the TX WTRU may prioritize the preferred carrier using different selection criteria and / or conditions compared to selecting a carrier that may be a non-preferred carrier. For example, the TX WTRU may be allowed to select a carrier based on a criterion and a condition regarding 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, carrier selection may be allowed. An example criterion used by the TX WTRU to select a carrier may be 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, carrier selection may be allowed. An example criterion used by the TX WTRU to select a carrier may be licensed versus unlicensed and / or based on LBT results for the unlicensed carrier. For example, if LBT failures have occurred less than a threshold number of times within a (pre-)configured past time period, selection of the 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.

[0112] 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.

[0113] 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 to be applied when evaluating preferred carriers and a second CBR threshold to be applied when evaluating non-preferred carriers. The TX WTRU may evaluate each supported carrier independently (e.g., one carrier at a time) before selecting. 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, may declare the carrier 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, may declare the carrier allowed. The TX WTRU may use the same criteria described herein or other criteria to select a subset of allowed carriers from the list of allowed carriers.

[0114] 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 an RSRP threshold. In an example, if the supported carrier is not a preferred carrier, the TX WTRU may select the supported carrier if the CBR measured on the carrier is below a 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.

[0115] 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.

[0116] A TX WTRU may prioritize preferred carriers when transmitting. A TX WTRU may prioritize preferred carriers during transmissions to a peer WTRU. For example, a TX WTRU may have multiple selected carriers on which to transmit, 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.

[0117] 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 data is 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 no data is 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).

[0118] For grants on non-preferred carriers, 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 grants on non-preferred carriers, the TX WTRU may apply a higher priority to data available for transmission 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 transmission so that the data appears to have a higher priority) than to data available for transmission to a first peer WTRU associated with a preferred carrier. In some examples, a grant on a preferred carrier may be available for transmission to (e.g., only to) a WTRU associated with a preferred WTRU, and may be discarded if no data is available for transmission to any WTRU that has that carrier as a preferred carrier. In some examples, a grant on a non-preferred carrier may not be used to transmit data associated with a WTRU that may have provided a list of preferred carriers. The WTRU may select (e.g., only) data associated with 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 in situations where the preferred carrier may correspond to a carrier agreed upon for transmissions between two peer WTRUs in a unicast link, and / or the non-preferred carrier may include any other carrier (e.g., on which transmissions of any broadcast type are possible). Thus, the WTRU may select a carrier for unicast sidelink transmissions with the RX WTRU, where the carrier is selected from a set of preferred carriers based on the condition that the first carrier satisfies the carrier selection criteria.

[0119] 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 select. For example, the TX WTRU may determine the number of carriers to select 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 a list of allowed carriers from the preferred carriers and may select at least a number of carriers including the allowed preferred carriers.

[0120] The TX WTRU may limit the selected carriers based on preferred carriers. For example, the TX WTRU may select a set of carriers for transmission by limiting the selection based on a set of preferred carriers from one or more peer WTRUs. In some examples, the selected carriers may be limited to (e.g., only) carriers indicated as preferred carriers by at least one other WTRU. Furthermore, in some examples, the selected carriers may include at least all of the preferred carriers that may be indicated by all peer WTRUs. For example, the selected carriers may include at least X of 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 of the carriers indicated as preferred (e.g., if they meet some other criteria as indicated herein). The value of X may be predetermined or may be configured (e.g., signaled in the Uu RRC or PC5-RRC).

[0121] The value of X may further depend on any one or a 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 sidelink 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 that WTRU. The value of X may depend on 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 those 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 with the 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).

[0122] 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 multicast / 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 that 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.

[0123] The TX WTRU may use a list of preferred carriers from one or more TX WTRUs during carrier (re)selection. The TX WTRU may perform 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.

[0124] During carrier selection, the TX WTRU may select a set of carriers based on 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 for 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.

[0125] 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 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). This selection may be performed in order of lowest CBR to highest CBR until X carriers are available for selection. The TX WTRU may then select additional carriers based on its needs. For example, if the TX WTRU must transmit on a carrier that is not part of the preferred carriers, 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 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 the TX WTRU may use to send data to the RX WTRU. For example, this may be limited to carriers in the preferred carrier list if the carriers in the preferred carrier list are allowed carriers as determined by the TX WTRU.

[0126] After receiving the carriers used by the TX WTRU, the RX WTRU may determine whether the TX WTRU's use of the carriers would result in exceeding the capabilities at the RX WTRU (e.g., the number of monitored carriers). If the TX WTRU's use of the carriers would 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.

[0127] Figure 2FIG2 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.

[0128] 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 carrier having 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 carrier having 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 carrier experiencing LBT failures less than the LBT failure threshold (e.g., within a preconfigured time period). 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 an ACK to NACK ratio above the HARQ threshold.

[0129] 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 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 an unlicensed band. If the number of LBT failures that have occurred within a (pre-)configured past time period is less than a threshold number, 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.

[0130] At 206, the WTRU may select an allowed carrier from 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 start with the carrier that is the preferred carrier of at least one peer WTRU in the unicast link and then select the allowed carriers in order of the CBR.

[0131] At 208, the WTRU may determine whether the selected allowed carrier supports multicast / broadcast. If the WTRU determines that the selected allowed carrier supports multicast / broadcast, then at 210, the WTRU may transmit data on the selected allowed carrier. If the WTRU determines that the selected allowed carrier does not support multicast / 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 preferred carriers for unicast sidelink transmissions for one or more peer WTRUs and may select additional carriers for broadcast transmissions if the preferred carrier is not suitable for broadcast sidelink transmission.

Claims

1. A first wireless transmit / receive unit (WTRU), comprising: A processor configured to: receiving an indication of a first set of carriers for sidelink transmission; receiving a message indicating a second set of carriers for which a second WTRU supports reception of sidelink transmissions; selecting a plurality of carriers for a sidelink transmission, wherein the plurality of carriers are selected based on the first set of carriers and the second set of carriers, wherein the sidelink transmission is a multicast or broadcast transmission; as well as The sidelink transmission is transmitted to at least one other WTRU via the plurality of carriers, wherein the plurality of carriers includes at least one carrier from the second set of carriers.

2. The first WTRU of claim 1 , wherein the second WTRU does not support receiving sidelink transmissions on carriers other than the second set of carriers.

3. The first WTRU of claim 1 , wherein the plurality of carriers includes at least one carrier that is part of the first set of carriers but not part of the second set of carriers.

4. The first WTRU of claim 1 , wherein the first set of carriers comprises one or more carriers on which the first WTRU is configured to transmit one or more sidelink transmissions.

5. The first WTRU of claim 1 , wherein the processor is configured to: The plurality of carriers are selected for the sidelink transmission based on a quality of service (QoS) associated with the sidelink transmission.

6. The first WTRU of claim 1 , wherein the second set of carriers of the second WTRU is associated with quality of service (QoS).

7. The first WTRU of claim 1 , wherein the processor is configured to: The plurality of carriers are selected for the sidelink transmission based on a received signal received power (RSRP) threshold associated with the sidelink transmission, wherein the plurality of carriers are selected based on a condition that the plurality of carriers have a measured RSRP above the RSRP threshold.

8. The first WTRU of claim 1 , wherein the processor is configured to: The plurality of carriers are selected for the sidelink transmission based on a channel busy ratio (CBR) threshold associated with the sidelink transmission, wherein the plurality of carriers are selected based on a condition that the plurality of carriers have a CBR below the CBR threshold.

9. The first WTRU of claim 1 , wherein the processor is configured to: The plurality of carriers are selected for the sidelink transmission based on a listen-before-talk (LBT) failure threshold associated with the sidelink transmission, wherein the plurality of carriers are selected based on a condition that the plurality of carriers experience LBT failures less than the LBT failure threshold within a preconfigured time period.

10. The first WTRU of claim 1 , wherein the processor is configured to: The plurality of carriers are selected for the sidelink transmission based on a hybrid automatic repeat request (HARQ) threshold associated with the sidelink transmission, wherein the plurality of carriers are selected based on a condition that the plurality of carriers have a ratio of ACK to NACK above the HARQ threshold.

11. A method performed by a first wireless transmit / receive unit (WTRU), the method comprising: receiving an indication of a first set of carriers for sidelink transmission; receiving a message indicating a second set of carriers for which a second WTRU supports reception of sidelink transmissions; selecting a plurality of carriers for a sidelink transmission, wherein the plurality of carriers are selected based on the first set of carriers and the second set of carriers, wherein the sidelink transmission is a multicast or broadcast transmission; as well as The sidelink transmission is transmitted to at least one other WTRU via the plurality of carriers, wherein the plurality of carriers includes at least one carrier from the second set of carriers.

12. The method of claim 11, wherein the second WTRU does not support receiving sidelink transmissions on carriers other than the second set of carriers.

13. The method of claim 11, wherein the plurality of carriers includes at least one carrier that is part of the first set of carriers but not part of the second set of carriers.

14. The method of claim 11, wherein the first set of carriers includes one or more carriers on which the first WTRU is configured to transmit one or more sidelink transmissions.

15. The method according to claim 11, further comprising: The plurality of carriers are selected for the sidelink transmission based on a quality of service (QoS) associated with the sidelink transmission.

16. The method of claim 11, wherein the second set of carriers of the second WTRU is associated with quality of service (QoS).

17. The method according to claim 11, wherein the method further comprises: The plurality of carriers are selected for the sidelink transmission based on a received signal received power (RSRP) threshold associated with the sidelink transmission, wherein the plurality of carriers are selected based on a condition that the plurality of carriers have a measured RSRP above the RSRP threshold.

18. The method according to claim 11, further comprising: The plurality of carriers are selected for the sidelink transmission based on a channel busy ratio (CBR) threshold associated with the sidelink transmission, wherein the plurality of carriers are selected based on a condition that the plurality of carriers have a CBR below the CBR threshold.

19. The method according to claim 11, wherein the method further comprises: The plurality of carriers are selected for the sidelink transmission based on a listen-before-talk (LBT) failure threshold associated with the sidelink transmission, wherein the plurality of carriers are selected based on a condition that the plurality of carriers experience LBT failures less than the LBT failure threshold within a preconfigured time period.

20. The method according to claim 11, wherein the method further comprises: The plurality of carriers are selected for the sidelink transmission based on a hybrid automatic repeat request (HARQ) threshold associated with the sidelink transmission, wherein the plurality of carriers are selected based on a condition that the plurality of carriers have a ratio of ACK to NACK above the HARQ threshold.

21. A first wireless transmit / receive unit (WTRU), the first wireless transmit / receive unit (WTRU) comprising: A processor and a transceiver, the processor and the transceiver being 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 criteria; 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 and second carriers is transmitted to the second WTRU in a second message.

22. The first WTRU of claim 21 , 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.

23. The first WTRU of claim 21 , wherein the processor and the transceiver are configured to: receiving a second sidelink message from the second WTRU indicating a set of non-preferred carriers for sidelink transmission, 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 that is different from the carrier selection criterion used to select the first carrier for unicast sidelink transmission.

24. The first WTRU of claim 21 , wherein the sidelink message is a first PC5 RRC reconfiguration message, and wherein the indication is conveyed within a second PC5 RRC reconfiguration message.

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