Relay reselection request indicating multihop relay support

Abstract

A first WTRU sends a link modification request to a second WTRU. The link modification request may comprise an indication of WTRU-to-WTRU relay reselection, an indication of candidate WTRU-to-WTRU relays, and an indication that multihop relay is supported. The first WTRU receives from the second WTRU a link modification accept message. The link modification accept message may indicate a selected end-to- end route. The link modification accept message may comprise an indication of a first end WTRU, a second end WTRU, and a list of relays between the first end WTRU and the second end WTRU. The link modification accept message may comprise an IP address associated with the second WTRU. The first WTRU sends a PCS link request to establish the selected end-to-end route and sends a link modification acknowledgement message to the second WTRU. The link modification acknowledgement message may comprise an IP address associated with the first WTRU.

Description

RELAY RESELECTION REQUEST INDICATING MULTIHOP RELAY SUPPORTCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application Number 63 / 541 ,220, filed September 28, 2023, the contents of which are hereby incorporated by reference herein.BACKGROUND

[0002] Mobile communications using wireless communication continue to evolve. A fifth generation may be referred to as 5G. A previous (legacy) generation of mobile communication may be, for example, fourth generation (4G) long term evolution (LTE).SUMMARY

[0003] Systems, methods, and instrumentalities are disclosed for coordinated WTRU-to-WTRU Relay Reselection procedures.

[0004] A wireless transmit and receive unit (WTRU), which may be referred to as a first WTRU, may be configured to send a link modification request to a second WTRU. The link modification request may comprise an indication of WTRU-to-WTRU relay reselection, an indication of candidate WTRU-to-WTRU relays, and an indication that multihop relay may be supported.

[0005] The first WTRU may receive from the second WTRU a link modification accept message. The link modification accept message may indicate a selected end-to-end route. The selected end-to-end route may include at least one of the candidate WTRU-to-WTRU relays. The link modification accept message may comprise an indication of a first end WTRU, an indication of a second end WTRU, and a list of relays between the first end WTRU and the second end WTRU. The link modification accept message may comprise an IP address associated with the second WTRU.

[0006] The first WTRU may send a PC5 link request to establish the selected end-to-end route. The first WTRU may send a link modification acknowledgement message to the second WTRU. The link modification acknowledgement message may comprise an IP address associated with the first WTRU.

[0007] The second WTRU may be configured to receive from the first WTRU a link modification request. The link modification request may comprise an indication of WTRU-to-WTRU relay reselection, an indication of candidate WTRU-to-WTRU relays, and an indication that multihop relay may be supported.

[0008] The second WTRU may perform a multihop WTRU-to-WTRU relay discovery procedure to discover available end-to-end routes to the second WTRU. The second WTRU may select one of the available end-to-end routes.

[0009] The second WTRU may send to the first WTRU a link modification accept message. The link modification accept message may indicate a selected end-to-end route. The selected end-to-end route may include at least one of the candidate WTRU-to-WTRU relays. The link modification accept message may comprise an indication of a first end WTRU, an indication of a second end WTRU, and a list of relays between the first end WTRU and the second end WTRU. The link modification accept message may comprise an IP address associated with the second WTRU.

[0010] The second WTRU may receive from the first WTRU a link modification acknowledgement message. The second WTRU may send a PC5 link request to establish the selected end-to-end route. The first WTRU and the second WTRU may communicate data over the selected end-to-end route.

[0011] A wireless transmit and receive unit (WTRU), which may be referred to as a first WTRU, may be configured to discover end-to-end routes via multihop relay to a second WTRU. The first WTRU may select candidate end-to-end routes to the second WTRU. The first WTRU may select candidate end-to-end routes based on whether WTRU-to-WTRU relays in the candidate end-to-end routes support multihop WTRU-to- WTRU relay services.

[0012] The first WTRU may send a link modification request to the second WTRU. The link modification request may comprise an indication of WTRU-to-WTRU relay reselection and an indication of the candidate end-to-end routes to the second WTRU. The indication of candidate end-to-end routes to the second WTRU may comprise for each candidate end-to-end route, an indication of a first end WTRU, an indication of a second end WTRU, and a list of relays between the first end WTRU and the second end WTRU.

[0013] The first WTRU may receive a link modification accept message from the second WTRU. The link modification accept message may indicate a selected end-to-end route. The first WTRU may perform an end-to-end connection setup procedure with the second WTRU via the selected end-to-end route.

[0014] The second WTRU may receive a link modification request from the first WTRU. The link modification request may comprise an indication of WTRU-to-WTRU relay reselection and an indication of the candidate end-to-end routes to the second WTRU. The indication of the candidate end-to-end routes to the second WTRU may comprise, for each candidate end-to-end route, an indication of a first end WTRU,an indication of a second end WTRU, and a list of relays between the first end WTRU and the second end WTRU.

[0015] The second WTRU may determine a selected end-to-end route from the candidate end-to-end routes. The second WTRU may determine the selected end-to-end route based on one or more of link quality, number of hops, or communication delay.

[0016] The second WTRU may send a link modification accept message to the first WTRU. The link modification accept message may indicate the selected end-to-end route. The second WTRU may perform an end-to-end connection setup procedure with the first WTRU via the selected end-to-end route. The first WTRU and the second WTRU may communicate data over the selected end-to-end route.BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1A is a system diagram illustrating an example communications system in which one or more disclosed embodiments may be implemented.

[0018] FIG. 1 B is a system diagram illustrating an example wireless transmit / receive unit (WTRU) that may be used within the communications system illustrated in FIG. 1A according to an embodiment.

[0019] FIG. 1 C is a system diagram illustrating an example radio access network (RAN) and an example core network (ON) that may be used within the communications system illustrated in FIG. 1 A according to an embodiment.

[0020] FIG. 1 D is a system diagram illustrating a further example RAN and a further example ON that may be used within the communications system illustrated in FIG. 1 A according to an embodiment.

[0021] FIG. 2 depicts example processing for Layer 3 based negotiated WTRU-to-WTRU Relay reselection.

[0022] FIG. 3 depicts an example Layer3 based Negotiated WTRU-to-WTRU Relay reselection procedure with multihop relay discovery at an initiating end WTRU.

[0023] FIG. 4 depicts example processing for Layer2 based Negotiated WTRU-to-WTRU Relay reselection procedure.DETAILED DESCRIPTION

[0024] A more detailed understanding may be had from the following description, given by way of example in conjunction with the accompanying drawings.

[0025] FIG. 1A is a diagram illustrating an example communications system 100 in which one or more disclosed embodiments may be implemented. The communications system 100 may be a multiple access system that provides content, such as voice, data, video, messaging, broadcast, etc., to multiple wireless users. The communications system 100 may enable multiple wireless users to access such content through the sharing of system resources, including wireless bandwidth. For example, the communications systems 100 may employ one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tail unique-word discrete Fourier transform (DFT)- Spread OFDM (ZT UW DTS-s OFDM), unique word OFDM (UW-OFDM), resource block-filtered OFDM, filter bank multicarrier (FBMC), and the like.

[0026] As shown in FIG. 1A, the communications system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a RAN 104 / 113, a ON 106 / 115, a public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, though it will be appreciated that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. By way of example, the WTRUs 102a, 102b, 102c, 102d, any of which may be referred to as a “station” and / or a “STA”, may be configured to transmit and / or receive wireless signals and may include a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular telephone, a personal digital assistant (PDA), a smartphone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (e.g., remote surgery), an industrial device and applications (e.g., a robot and / or other wireless devices operating in an industrial and / or an automated processing chain contexts), a consumer electronics device, a device operating on commercial and / or industrial wireless networks, and the like. Any of the WTRUs 102a, 102b, 102c, and 102d may be interchangeably referred to as a UE.

[0027] The communications systems 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 wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the CN 106 / 115, the I nternet 110, and / or the other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a Node-B, an eNode B (eNB), a Home Node B, a Home eNode B, a gNode B (gNB), a NR NodeB, a site controller, an access point (AP), a wireless router, and the like. While the base stations 114a, 114b are each depicted as a single element, itwill be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0028] The 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. The base station 114a and / or the base station 114b may be configured to transmit and / or receive wireless signals on one or more carrier frequencies, which may be referred to as a cell (not shown). These frequencies may be in licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide coverage for a wireless service to a specific geographical area that may be relatively fixed or that may change over time. The cell may further be divided into cell sectors. For example, the cell associated with the base station 114a may be divided into three sectors. Thus, in one embodiment, the base station 114a may include three transceivers, i.e. , one for each sector of the cell. In an embodiment, the base station 114a may employ multiple-input multiple output (MIMO) technology and may utilize multiple transceivers for each sector of the cell. For example, beamforming may be used to transmit and / or receive signals in desired spatial directions.

[0029] 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).

[0030] More specifically, as noted above, the communications system 100 may be a multiple access system and may employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. 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 establish the air interface 115 / 116 / 117 using wideband CDMA (WCDMA). 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).

[0031] 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).

[0032] 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).

[0033] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may implement LTE radio access and NR radio access together, for instance using dual connectivity (DC) principles. Thus, the air interface utilized by WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions sent to / from multiple types of base stations (e.g., an eNB and a gNB).

[0034] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.11 (i.e., Wireless Fidelity (WiFi), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and the like.

[0035] The base station 114b in FIG. 1 A may be a wireless router, Home Node B, Home eNode B, or access point, for example, and may utilize any suitable RAT for facilitating wireless connectivity in a localized area, such as a place of business, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a roadway, and the like. 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. As shown in FIG. 1 A, the base station 114b may have a direct connection to the Internet 110. Thus, the base station 114b may not be required to access the Internet 110 via the CN 106 / 115.

[0036] The RAN 104 / 113 may be in communication with the CN 106 / 115, which may be any type of network configured to provide voice, data, applications, and / or voice over internet protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have varying quality of service (QoS) requirements, such as differing throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, and the like. The CN 106 / 115 may provide call control, billing services, mobile location-based services, pre-paid calling,Internet connectivity, video distribution, etc., and / or perform high-level security functions, such as user authentication. Although not shown in FIG. 1A, 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 be utilizing a NR radio technology, the CN 106 / 115 may also be in communication with another RAN (not shown) employing a GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0037] The CN 106 / 115 may also serve as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or the other networks 112. The PSTN 108 may include circuit- switched telephone networks that provide plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols, such as the transmission control protocol (TCP), user datagram protocol (UDP) and / or the internet protocol (IP) in the TCP / IP internet protocol suite. The networks 112 may include wired and / or wireless communications 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.

[0038] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communications system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks over different wireless links). For example, the WTRU 102c shown in FIG. 1A 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.

[0039] FIG. 1 B is a system diagram illustrating an example WTRU 102. As shown in FIG. 1 B, the WTRU 102 may include a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and / or other peripherals 138, among others. It will be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0040] 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 in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) circuits, any other type of integrated circuit (IC), a state machine, and the like. The processor 118 may perform signal coding, data processing,power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. While FIG. 1 B depicts the processor 118 and the transceiver 120 as separate components, it will be appreciated that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0041] The transmit / receive element 122 may be configured to transmit signals to, or receive signals from, a base station (e.g., the base station 114a) over 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 an embodiment, the transmit / receive element 122 may be an emitter / detector configured to transmit and / or receive IR, UV, or visible light signals, for example. In yet another embodiment, the transmit / receive element 122 may be configured to transmit and / or receive both RF and light signals. It will be appreciated that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0042] Although the transmit / receive element 122 is depicted in FIG. 1 B as a single element, 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.

[0043] The transceiver 120 may be configured to modulate the signals that are to be transmitted by the transmit / receive element 122 and to demodulate the signals that are received by the transmit / receive element 122. As noted above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers for enabling the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11 , for example.

[0044] The processor 118 of the WTRU 102 may be coupled to, and may receive user input data from, the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or organic light-emitting diode (OLED) display unit). The processor 118 may also output user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. In addition, the processor 118 may access information from, and store data in, any type of suitable memory, such as the non-removable memory 130 and / or the removable memory 132. The non-removable memory 130 may include random-access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, and the like. In other embodiments, the processor 118may 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).

[0045] The processor 118 may receive power from the power source 134 and may be configured to distribute and / or control the 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, and the like.

[0046] 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 over the air interface 116 from a base station (e.g., base stations 114a, 114b) and / or determine its location based on the timing of the signals being received from two or more nearby base stations. It will be appreciated that the WTRU 102 may acquire location information by way of any suitable locationdetermination method while remaining consistent with an embodiment.

[0047] The processor 118 may further be coupled to other peripherals 138, which may include one or more software and / or hardware modules that provide additional features, functionality and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an e-compass, a satellite transceiver, a digital camera (for photographs and / or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands free headset, a Bluetooth® module, a frequency modulated (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, an activity tracker, and the like. The peripherals 138 may include one or more sensors, the sensors may be one or more of 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.

[0048] The WTRU 102 may include a full duplex radio for which transmission and reception of some or all of the signals (e.g., associated with particular subframes for both the 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 to reduce and or substantially eliminate self-interference via either hardware (e.g., a choke) or signal processing via a processor (e.g., a separate processor (not shown) or via processor 118). In an embodiment, the WRTU 102 may include a half-duplex radio for which transmissionand reception of some or all of the signals (e.g., associated with particular subframes for either the UL (e.g., for transmission) or the downlink (e.g., for reception)).

[0049] FIG. 1 C is a system diagram illustrating the RAN 104 and the CN 106 according to an embodiment. As noted above, the RAN 104 may employ an E-UTRA radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0050] 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.

[0051] Each of the eNode-Bs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, and the like. As shown in FIG. 1 C, the eNode-Bs 160a, 160b, 160c may communicate with one another over an X2 interface.

[0052] The CN 106 shown in FIG. 1 C 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 will be appreciated that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0053] 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, selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c, and the like. The MME 162 may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as GSM and / or WCDMA.

[0054] The SGW 164 may be connected to each of the eNode Bs 160a, 160b, 160c in the RAN 104 via the S1 interface. The SGW 164 may generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions, such as anchoring user planes during inter- eNode B handovers, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, managing and storing contexts of the WTRUs 102a, 102b, 102c, and the like.

[0055] 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.

[0056] 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 communicate with, an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that serves as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to the other networks 112, which may include other wired and / or wireless networks that are owned and / or operated by other service providers.

[0057] Although the WTRU is described in FIGS. 1 A-1 D as a wireless terminal, it is contemplated that in certain representative embodiments that such a terminal may use (e.g., temporarily or permanently) wired communication interfaces with the communication network.

[0058] In representative embodiments, the other network 112 may be a WLAN.

[0059] 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 an access or an interface to a Distribution System (DS) or another type of wired / wireless network that carries traffic in to and / or out of the BSS. Traffic to STAs that originates from outside the BSS may arrive through the AP and may be delivered to the STAs. Traffic originating from STAs to destinations outside the BSS may be sent to the AP to be delivered to respective destinations. Traffic between STAs within the BSS may be sent through the AP, for example, where the source STA may send traffic to the AP and the AP may deliver the traffic to the destination STA. The traffic between STAs within a BSS may be considered and / or referred to as peer-to- peer traffic. The peer-to-peer traffic may be sent between (e.g., directly between) the source and destination STAs with a direct link setup (DLS). In certain representative embodiments, the DLS may use an 802.11e DLS or an 802.11 z tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may not have an AP, and the STAs (e.g., all of the STAs) within or using the IBSS may communicate directly with each other. The IBSS mode of communication may sometimes be referred to herein as an “ad-hoc” mode of communication.

[0060] When using the 802.11 ac infrastructure mode of operation or a similar mode of operations, the AP may transmit a beacon on a fixed channel, such as a primary channel. The primary channel may be a fixed width (e.g., 20 MHz wide bandwidth) or a dynamically set width via signaling. The primary channelmay be the operating channel of the BSS and may be used by the STAs to establish a connection with the AP. In certain representative embodiments, Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) may be implemented, for example in in 802.11 systems. For CSMA / CA, the STAs (e.g., every STA), including the AP, may sense the primary channel. If the primary channel is sensed / detected and / or determined to be busy by a particular STA, the particular STA may back off. One STA (e.g., only one station) may transmit at any given time in a given BSS.

[0061] High Throughput (HT) STAs may use a 40 MHz wide channel for communication, for example, via a combination of the primary 20 MHz channel with an adjacent or nonadjacent 20 MHz channel to form a 40 MHz wide channel.

[0062] Very High Throughput (VHT) STAs may support 20MHz, 40 MHz, 80 MHz, and / or 160 MHz wide channels. The 40 MHz, and / or 80 MHz, channels may be formed by combining contiguous 20 MHz channels. A 160 MHz channel may be formed by combining 8 contiguous 20 MHz channels, or by combining two non-contiguous 80 MHz channels, which may be referred to as an 80+80 configuration. For the 80+80 configuration, the data, after channel encoding, may be passed through a segment parser that may divide the data into two streams. Inverse Fast Fourier Transform (IFFT) processing, and time domain processing, may be done on each stream separately. The streams may be mapped on to the two 80 MHz channels, and the data may be transmitted by a transmitting STA. At the receiver of the receiving STA, the above described operation for the 80+80 configuration may be reversed, and the combined data may be sent to the Medium Access Control (MAC).

[0063] Sub 1 GHz modes of operation are supported by 802.11 af and 802.11 ah. The channel operating bandwidths, and carriers, are reduced in 802.11 af and 802.11 ah relative to those used in 802.11 n, and 802.11ac. 802.11af supports 5 MHz, 10 MHz, and 20 MHz bandwidths in the TV White Space (TVWS) spectrum, and 802.11 ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non- TVWS spectrum. According to a representative embodiment, 802.11 ah may support Meter Type Control / Machine-Type Communications, such as MTC devices in a macro coverage area. MTC devices may have certain capabilities, for example, limited capabilities including support for (e.g., only support for) certain and / or limited bandwidths. The MTC devices may include a battery with a battery life above a threshold (e.g., to maintain a very long battery life).

[0064] WLAN systems, which may support multiple channels, and channel bandwidths, such as 802.11 n, 802.11 ac, 802.11 af, and 802.11 ah, include a channel which may be designated as the primary channel. The primary channel may have a bandwidth equal to the largest common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be set and / or limited by aSTA, from among all STAs in operating in a BSS, which supports the smallest bandwidth operating mode. In the example of 802.11 ah, the primary channel may be 1 MHz wide for STAs (e.g., MTC type devices) that support (e.g., only support) a 1 MHz mode, 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, due to a STA (which supports (e.g., only supports) a 1 MHz operating mode), transmitting to the AP, the entire available frequency bands may be considered busy even though a majority of the frequency bands remains idle and may be available.

[0065] In the United States, the available frequency bands, which may be used by 802.11 ah, are from 902 MHz to 928 MHz. In Korea, the available frequency bands are from 917.5 MHz to 923.5 MHz. In Japan, the available frequency bands are from 916.5 MHz to 927.5 MHz. The total bandwidth available for 802.11 ah is 6 MHz to 26 MHz depending on the country code.

[0066] FIG. 1 D is a system diagram illustrating the RAN 113 and the CN 115 according to an embodiment. As noted above, the RAN 113 may employ an 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.

[0067] The RAN 1 13 may include gNBs 180a, 180b, 180c, though it will be appreciated that the RAN 113 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, 180c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, gNBs 180a, 108b may utilize beamforming to transmit signals to and / or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a, for example, may use multiple antennas to transmit wireless signals to, and / or receive wireless signals from, the WTRU 102a. In an embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation technology. For example, the gNB 180a may transmit multiple component carriers to the WTRU 102a (not shown). A subset of these component carriers may be on unlicensed spectrum while the remaining component carriers may be on licensed spectrum. In an embodiment, the gNBs 180a, 180b, 180c may implement Coordinated Multi-Point (CoMP) technology. For example, WTRU 102a may receive coordinated transmissions from gNB 180a and gNB 180b (and / or gNB 180c).

[0068] The WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using transmissions associated with a scalable numerology. For example, the OFDM symbol spacing and / or OFDM subcarrier spacing may vary for different transmissions, different cells, and / or different portions ofthe wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using subframe or transmission time intervals (TTIs) of various or scalable lengths (e.g., containing varying number of OFDM symbols and / or lasting varying lengths of absolute time).

[0069] 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 the standalone configuration, WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c without also accessing other RANs (e.g., such as eNode-Bs 160a, 160b, 160c). In the standalone configuration, WTRUs 102a, 102b, 102c may utilize one or more of gNBs 180a, 180b, 180c as a mobility anchor point. In the standalone configuration, WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration WTRUs 102a, 102b, 102c may communicate with / connect to gNBs 180a, 180b, 180c while also communicating with / connecting to another RAN such as eNode-Bs 160a, 160b, 160c. For example, 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 the non-standalone configuration, eNode-Bs 160a, 160b, 160c may serve as a mobility anchor for WTRUs 102a, 102b, 102c and gNBs 180a, 180b, 180c may provide additional coverage and / or throughput for servicing WTRUs 102a, 102b, 102c.

[0070] Each of the gNBs 180a, 180b, 180c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, support of network slicing, dual connectivity, interworking between NR and E- UTRA, routing of user plane data towards User Plane Function (UPF) 184a, 184b, routing of control plane information towards Access and Mobility Management Function (AMF) 182a, 182b and the like. As shown in FIG. 1 D, the gNBs 180a, 180b, 180c may communicate with one another over an Xn interface.

[0071] The CN 115 shown in FIG. 1 D 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 a Data Network (DN) 185a, 185b. While each of the foregoing elements are depicted as part of the CN 115, it will be appreciated that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0072] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via an N2 interface and may serve as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, support for network slicing (e.g., handling of different PDU sessions with different requirements), selecting a particular SMF 183a, 183b, management of the registration area, termination of NAS signaling, mobility management, and the like.Network slicing may be used by the AMF 182a, 182b in order to customize CN support for WTRUs 102a, 102b, 102c based on the types of services being utilized 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 massive mobile broadband (eMBB) access, services for machine type communication (MTC) access, and / or the like. 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.

[0073] The SMF 183a, 183b may be connected to an AMF 182a, 182b in the CN 115 via an N11 interface. The SMF 183a, 183b may also be connected to a UPF 184a, 184b in the CN 115 via an N4 interface. The SMF 183a, 183b may select and control the UPF 184a, 184b and configure the routing of traffic through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions, such as managing and allocating UE IP address, managing PDU sessions, controlling policy enforcement and QoS, providing downlink data notifications, and the like. A PDU session type may be IP-based, non-IP based, Ethernetbased, and the like.

[0074] The UPF 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via an 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.

[0075] 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 serves as an interface between the CN 115 and the PSTN 108. In addition, the CN 115 may provide the WTRUs 102a, 102b, 102c with access to the other networks 112, which may include other wired and / or wireless networks that are owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to a local Data Network (DN) 185a, 185b through the UPF 184a, 184b via the N3 interface to the UPF 184a, 184b and an N6 interface between the UPF 184a, 184b and the DN 185a, 185b.

[0076] In view of Figures 1 A-1 D, and the corresponding description of Figures 1 A-1 D, one or more, or all, of the functions described herein with regard to one or more of: WTRU 102a-d, Base Station 114a-b, eNode-B 160a-c, MME 162, SGW 164, PGW 166, gNB 180a-c, AMF 182a-b, UPF 184a-b, SMF 183a-b, DN 185a-b, and / or any other device(s) described herein, may be performed by one or more emulationdevices (not shown). The emulation devices may be one or more devices configured to emulate one or more, or all, of the functions described herein. For example, the emulation devices may be used to test other devices and / or to simulate network and / or WTRU functions.

[0077] The emulation devices may be designed to implement one or more tests of other devices in a lab environment and / or in an operator network environment. For example, the one or more emulation devices may perform the one or more, or all, functions while being fully or partially implemented and / or deployed as part of a wired and / or wireless communication network in order to test other devices within the communication network. The one or more emulation devices may perform the one or more, or all, functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network. The emulation device may be directly coupled to another device for purposes of testing and / or may perform testing using over-the-air wireless communications.

[0078] The one or more emulation devices may perform the one or more, including all, functions while not being implemented / deployed as part of a wired and / or wireless communication network. For example, the emulation devices may be utilized in a testing scenario in a testing laboratory and / or a non-deployed (e.g., testing) wired and / or wireless communication network in order to implement testing of one or more components. The one or more emulation devices may be test equipment. Direct RF coupling and / or wireless communications via RF circuitry (e.g., which may include one or more antennas) may be used by the emulation devices to transmit and / or receive data.

[0079] Systems, methods, and instrumentalities are disclosed for WTRU-to-WTRU Relay Reselection procedures using WTRU-to-WTRU Relay discovery and connection setup. An initiating WTRU, if triggered for relay reselection, may indicate multihop relay connection and propose candidate end-to-end routes. An end WTRU, if receiving a link modification request for relay reselection, may discover an end-to-end route via multihop relays and may share the selected end-to-end route with the other End WTRU. Based on the end-to-end route, PC5 connection setup or link modification procedure may be performed based on the end-to-end route information.

[0080] Systems, methods, and instrumentalities are disclosed for Layer 3 based negotiated WTRU-to- WTRU Relay reselection for multihop connection.

[0081] A WTRU, which may be referred to as WTRU1 , may trigger relay reselection for communication with a second WTRU, which may be referred to as WTRU2, via another relay. WTRU1 may send a link modification request to WTRU2 via a first relay which may be referred to as relay 1 . The request may include an indication of WTRU-to-WTRU relay reselection, an indication of candidate WTRU-to-WTRU relay(s), and an indication of whether multihop relay is supported.

[0082] WTRU1 may receive a link modification accept message from WTRU2 via relay 1 . The link modification accept message may include a selected new end-to-end route, which may be specified by designating two end WTRUs and a list of WTRU-to-WTRU relays between the two end WTRUs, and an IP address of WTRU2 to be used in connection with the new WTRU-to-WTRU route.

[0083] WTRU1 may respond with a PC5 link setup request or a PC5 link modification request to establish or set up the selected end-to-end route via the selected WTRU-to-WTRU relay WTRU in the selected end-to-end route. WTRU1 may send a link modification acknowledgement message to WTRU2 via relayl including an IP address of WTRU1 to be used in association with the new end-to-end route. WTRU1 may exchange traffic with WTRU2 via the newly selected and established end-to-end route.

[0084] WTRU2 may receive from WTRU1 via relay 1 the link modification request indicating a request for WTRU-to-WTRU relay reselection. WTRU 2 may perform a multihop WTRU-to-WTRU relay or multihop candidate WTRU-to-WTRU relay discovery procedure to discover an end-to-end route to WTRU1. WTRU2 may select an end-to-end route to WTRU1 via multihop relays.

[0085] WTRU2 may initiate a PC5 link setup or a modification procedure for the selected end-to-end route with a selected WTRU-to-WTRU relay WTRU in the selected end-to-end route. WTRU2 may send a link modification accept message to WTRU1 via relayl including a selected new end-to-end route and an IP address for WTRU2 for use in connection with the new end-to-end route.

[0086] WTRU2 may receive from WTRU1 via relay 1 a link modification ack message including an IP address of WTRU1 for use in connection with the new end-to-end route. WTRU2 may exchange traffic with WTRU1 via the new end-to-end route.

[0087] Systems, methods, and instrumentalities are disclosed for Layer 2 based negotiated WTRU-to- WTRU relay reselection for multihop connection.

[0088] A WTRU, which may be referred to as WTRU1 , may trigger relay reselection for communication with a second WTRU which may be referred to as WTRU2. WTRU1 may discover end-to-end routes via multihop relay to WTRU2 and may select a candidate list of end-to-end routes to WTRU2. WTRU1 may send a link modification request to WTRU2 via relayl . The link modification request may include an indication of WTRU-to-WTRU relay reselection and candidate end-to-end routes via multihop relay.

[0089] WTRU1 may receive a link modification accept message from WTRU2 via relayl including the selected new end-to-end route. WTRU1 may perform an end-to-end connection setup procedure with WTRU2 via the selected new end-to-end route. WTRU1 may exchange traffic with WTRU2 via the newly selected end-to-end route.

[0090] WTRU2 may receive from WTRU1 via relay 1 the link modification request indicating WTRU-to- WTRU relay reselection and the candidate list of end-to-end routes to WTRU2. WTRU2 may select a new end-to-end route to WTRU1 from the candidate list of end-to-end routes. WTRU2 may send to WTRU 1 via relay 1 a link modification accept message including the selected new end-to-end route and an IP address for WTRU2 for use in connection with the new end-to-end route.

[0091] WTRU2 may perform end-to-end connection setup procedure with WTRU1 via the selected new e2e route. WTRU2 may exchange traffic with WTRU1 via the new end-to-end route.

[0092] 5G Proximity Services (ProSe) may define several features and procedures such as 5G ProSe Direct Discovery, 5G ProSe Direct Communication, 5G ProSe WTRU-to-Network Relay, and 5G ProSe WTRU-to-WTRU Relay.

[0093] 5G ProSe WTRU-to-WTRU Relay may enable indirect communication between two End WTRUs. For WTRU-to-WTRU Relay, 5G ProSe WTRU-to-WTRU Relay Discovery and 5G ProSe Communication via WTRU-to-WTRU Relay may be employed.

[0094] For 5G ProSe WTRU-to-WTRU Relay Discovery, both Model A and Model B discovery may be supported. In connection with Model A discovery, a single discovery protocol message (e.g., Announcement) may be employed. In connection with Model B discovery, two discovery protocol messages (e.g., Solicitation and Response) may be employed.

[0095] 5G ProSe may also support discovery integrated into a PC5 unicast link establishment procedure.

[0096] 5G ProSe Communication via WTRU-to-WTRU Relay may be possible with Layer2 WTRU-to- WTRU Relay or Layer3 WTRU-to-WTRU Relay. For Layer2 WTRU-to-WTRU Relay and Layer3 WTRU-to- WTRU Relay, 5G ProSe communication setup with discovery procedures may be defined. Discovery integrated into PC5 unicast link establishment procedure may be defined.

[0097] With Layer2 WTRU-to-WTRU Relay, an end-to-end PC5 link may be established between the End WTRUs via the Relay. PC5-S messages may then be exchanged between End WTRUs.

[0098] With Layer3 WTRU-to-WTRU Relay, each End WTRU may establish a PC5 link with the Relay. The Relay may forward messages towards End WTRUs. PC5-S messages may be exchanged between End WTRUs and the Relay.

[0099] With Layer3 WTRU-to-WTRU Relay, if an IP based data connection may be used, after PC5 link setup with Relay, each End WTRU may be assigned an IP address by Relay which may be based on DHCP mechanism, or each End WTRU may assign its own IP address, which may be based on a link local IP address assignment mechanism, and may inform the Relay of the assigned IP address. Whether the IPaddress may be assigned based on either DHCP or link local IP address may be determined during security connection setup between an end WTRU and WTRU-to-WTRU Relay.

[0100] WTRU-to-WTRU reselection may be provided. After connection setup between two End WTRUs via a WTRU-to-WTRU Relay, each End WTRU may keep monitoring the channel status of the PC5 link and if link quality goes below some threshold, the End WTRU may select another WTRU-to-WTRU Relay for the connection between two End WTRUs.

[0101] For WTRU-to-WTRU Relay reselection, WTRU-to-WTRU Relay discovery procedures may be used or the negotiated 5G ProSe WTRU-to-WTRU Relay reselection procedure may be used.

[0102] In the negotiated WTRU-to-WTRU Relay reselection, one End WTRU may initiate the WTRU-to- WTRU Relay reselection procedure. End WTRUs may negotiate a new WTRU-to-WTRU Relay using the existing connection and may establish the communication via the reselected WTRU-to-WTRU Relay prior to releasing the communication via the current 5G ProSe WTRU-to-WTRU Relay.

[0103] Multi-hop communications may be provided for WTRU-to-network and WTRU-to-WTRU Relay communications. Potential enhancements to support multi-hop for WTRU-to-network and WTRU-to-WTRU may be provided.

[0104] Multi-hop for WTRU-to-network Relays may enable a remote WTRU to discover and communicate with a WTRU-to-network Relay via one or more WTRU-to-WTRU relays. Multi-hop WTRU-to- WTRU Relays may enable End WTRUs to discover and communicate with each other via more than one WTRU-to-WTRU Relay.

[0105] The multi-hop capability may be employed, e.g., may be deemed crucial, for mission critical communications (e.g., first responders) and, in general, may be useful for enhancing coverage (e.g., indoor coverage).

[0106] Providing relay reselection for multihop connections may be desired. If end WTRUs (e.g., WTRU1 and WTRU2) may be connected via Relayl , WTRUs may change to another relay (relay2) if relay link quality becomes bad while minimizing the interruption delay based on a negotiated relay reselection procedure. This negotiated relay reselection procedure may assume that there may be at least one relay directly reachable by both end WTRUs to connect. But, in examples, two end WTRUs may not maintain end-to-end connection via a single hop relay connection but may connect via a multihop relay connection.

[0107] For example, after WTRU1 and WTRU2 may be connected via relayl , WTRU1 may discover a new relay (relay2) for relay reselection instead of relayl . But WTRU2 may not connect to relay2 directly. Instead WTRU2 may connect to relay2 via relay3.

[0108] If there may be no common relay available in direct connection between two end WTRUs, WTRUs may perform negotiated relay reselection with consideration of commonly available relays in a multihop environment.

[0109] A WTRU-to-WTRU Relay WTRU (which may be referred to as, for example, U2U Relay WTRU, UE-to-UE Relay, or U2U Relay) may refer to a WTRU which may be authorized and behaves as a relay WTRU to forward traffic between end WTRUs. The following terms may be used interchangeably: initiating WTRU, source end WTRU, source WTRU. The following terms may be used interchangeably: responding WTRU, target end WTRU, target WTRU.

[0110] A WTRU-to-WTRU Relay discovery procedure (which may be referred to as, for example, U2U Relay discovery procedure) may discover a path to a target WTRU via a relay WTRU. Using a WTRU-to- WTRU Relay discovery procedure, an initiating WTRU may obtain information relating to WTRU-to-WTRU Relay(s) which may be reachable to the target WTRU. An initiating WTRU may select a proper end-to-end route to the target WTRU via a Relay WTRU. For multihop support, in the discovery response, a WTRU-to- WTRU Relay may provide an indication of whether or not it supports multihop relay.

[0111] A multihop WTRU-to-WTRU Relay discovery procedure and a multihop candidate WTRU-to- WTRU Relay discovery procedure may be performed by an end WTRU.

[0112] A multihop WTRU-to-WTRU Relay discovery procedure may discover an end-to-end path to reach a target WTRU via a path through a single or multiple relay WTRUs. For example, an end-to-end (which may be referred to, for example, as, e2e) path between WTRU1 and WTRU2 via relayl and relay2 may be expressed as [WTRU1 , Relayl , Relay2, and WTRU2], In a multihop WTRU-to-WTRU relay discovery procedure for a target WTRU, an initiating WTRU may obtain information from WTRU-to-WTRU Relay WTRU(s) about the path(s) to the target WTRU involving the WTRU-to-WTRU relay WTRU(s) and other WTRU-to-WTRU relay WTRUs in the path between WTRU-to-WTRU Relay WTRU(s) and the target WTRU. An initiating WTRU may select proper end-to-end candidate routes (e.g., the best, acceptable, or available end-to-end (E2E) routes considering various criteria such as, for example, number of relays, expected end-to-end QoS, existing PC5 connections via Relays, etc.) between the initiating WTRU and the target WTRU via multihop relay WTRUs.

[0113] A multihop candidate WTRU-to-WTRU Relay discovery procedure may discover an end-to-end path for a target WTRU-to-WTRU Relay via a path through single or multihop relay WTRUs. A multihop candidate WTRU-to-WTRU Relay discovery procedure may be performed by performing a multihop WTRU-to-WTRU Relay discovery procedure by setting a target WTRU-to-WTRU relay WTRU’s information as a target WTRU’s information.

[0114] A negotiated layer 3 WTRU-to-WTRU Relay reselection procedure with multihop relay discovery at a responding End WTRU may be provided. A negotiated layer-3 WTRU-to-WTRU relay reselection procedure with multihop relay discovery support and with a list of candidate WTRU-to-WTRU relays which may be directly reachable may be provided by an initiating End WTRU (WTRU1).

[0115] Based on the list of WTRU-to-WTRU relays, a responding End WTRU (WTRU2) may attempt to find a new end-to-end route to WTRU 1 . WTRU2 may consider multihop routes to WTRU1 if there may be no relay in the provided list reachable directly by WTRU2.

[0116] Once WTRU2 determines that a multihop connection may be useful, e.g., may be needed, (e.g., because no candidate relays may be directly reachable), WTRU2 may initiate multihop WTRU-to-WTRU relay discovery for WTRU1 or multihop candidate WTRU-to-WTRU relay discovery for relay WTRUs in the list.

[0117] WTRU2 may select an end-to-end route to reach WTRU1 based on received information from the discovery procedure, may initiate a PC5 connection setup procedure via the selected route, and may inform WTRU1 about the selected end-to-end route.

[0118] During the negotiated WTRU-to-WTRU Relay reselection procedure, WTRU1 and WTRU2 may exchange their new IP address to be used at the newly selected end-to-end route.

[0119] FIG. 2 depicts example processing for Layer 3 based negotiated WTRU-to-WTRU Relay reselection.

[0120] Referring to FIG. 2, at 0, WTRU1 , WTRU2, and Relays may be authorized and receive parameter provisioning information. WTRU1 and WTRU2 may be authorized for multihop WTRU-to-WTRU Relay service as End WTRUs and may be provisioned with parameters for discovery and connection setup with other WTRUs via multihop WTRU-to-WTRU Relay services. Relayl , Relay2, Relay3, and Relay4 may be authorized for multihop WTRU-to-WTRU Relay service as Relay WTRUs and may be provisioned with parameters for discovery and connection setup with other WTRUs and relay WTRUs via multihop WTRU- to-WTRU Relay services. The provisioned parameters may include parameters such as, for example, RSC (Relay service Code(s)), lists of PLMN, and user info ID of WTRU for application, which may be allowed at a multihop relay connection.

[0121] Referring to FIG. 2, at 1 , WTRU1 and WTRU2 may set up a PC5 connection with Relayl for communication between WTRU1 and WTRU2. WTRU1 and WTRU2 may exchange data traffic, e.g., IP traffic, via Relayl .

[0122] Referring to FIG. 2, at 2, WTRU1 , which may be an initiating End WTRU, may determine, e.g., based on PC5 signal strength, to perform WTRU-to-WTRU Relay reselection.

[0123] WTRU1 may obtain a list of WTRU-to-WTRU Relays which may be accessible by WTRU1 in direct PC5 connection. The list of WTRU-to-WTRU Relays may include the WTRU-to-WTRU Relays which have PC5 connection with WTRU1 and the WTRU-to-WTRU Relays from which WTRU1 received WTRU- to-WTRU Relay Discovery Announcement messages or a WTRU-to-WTRU Relay Discovery Response message in response to a Discovery Solicitation message sent by WTRU1 . WTRU1 may initiate WTRU-to- WTRU Relay discovery procedures to find the candidate WTRU-to-WTRU Relays.

[0124] WTRU1 may determine the candidate WTRU-to-WTRU Relays from a list of WTRU-to-WTRU Relays based on, for example, signal strength, delay for sending and responding messages, Relay Service Code for WTRU-to-WTRU Relay services supported by a WTRU-to-WTRU Relay, whether a WTRU-to- WTRU Relay supports multihop WTRU-to-WTRU Relay services, and / or supported traffic type which may be, for example, IP traffic, Ethernet traffic, etc.

[0125] During a discovery procedure, WTRU1 may receive information indicating whether a WTRU-to- WTRU Relay supports multihop WTRU-to-WTRU Relay services.

[0126] Referring to FIG. 2, at 3, WTRU1 may send a Link Modification Request message to Relayl . A Link Modification Request may include a Relay re-selection indication, information of candidate WTRU-to- WTRU Relay(s), IP addresses of the responding End WTRUs (e.g., WTRU2), an IP address of WTRU1 , and / or an indication of whether multihop relay connection may be supported.

[0127] For each WTRU-to-WTRU Relay, WTRU1 may specify the User Info ID and may include an indication of whether the WTRU-to-WTRU relay supports multihop WTRU-to-WTRU Relay services.

[0128] Multiple End WTRUs’ IP addresses may be included at responding End WTRUs if WTRU1 may be communicating with multiple End WTRUs via Relayl .

[0129] Referring to FIG. 2, at 4, based on End WTRUs’ IP addresses that may be received at 3, Relayl may determine the responding End WTRUs (e.g., WTRU2) and may send a Link Modification Request message to the responding End WTRUs (e.g., WTRU2).

[0130] The Link Modification Request message may include a Relay re-selection indication, User Info ID(s) of the candidate WTRU-to-WTRU Relay(s), IP address of WTRU1 , and an indication whether multihop relay connection may be supported.

[0131] For each WTRU-to-WTRU Relay, an indication whether the WTRU-to-WTRU relay supports multihop WTRU-to-WTRU Relay services may be included if received at 3.

[0132] If multiple End WTRUs may be specified in the Link Modification Request message received from WTRU1 , Relayl may send a PC5 Link Modification Request to each of the End WTRUs.

[0133] Referring to FIG. 2, at 5, if receiving a Link Modification Request for Relay reselection sent at 4, WTRU2 may select a new WTRU-to-WTRU Relay from the candidate WTRU-to-WTRU Relays.

[0134] WTRU2 may initiate a multihop WTRU-to-WTRU relay discovery procedure with a target WTRU (e.g., WTRU1) or a multihop candidate WTRU-to-WTRU relay discovery procedure with target WTRU-to- WTRU Relay(s) in the received candidate WTRU-to-WTRU relays if, for example, WTRU2 does not identify a Relay WTRU from the candidate WTRU-to-WTRU Relays which may be proper for direct connection with WTRU2 based on, for example, link quality, result of direct discovery procedure, etc.

[0135] Referring to FIG. 2, at 6, WTRU2 may select an end-to-end route (an end-to-end route may be designated, for example, in the format [WTRU2, Relay4, Relay2, and WTRU1]) including a WTRU-to- WTRU relay or multihop WTRU-to-WTRU relays for new end-to-end connection to WTRU1 , based on, for example, discovery results determined at 5, link quality, number of hops of an end-to-end route, end-to-end delay of an end-to-end route, etc.

[0136] Referring to FIG. 2, at 7, based on a selected end-to-end route (e.g., [WTRU2, Relay4, Relay2, and WTRU1]), WTRU2 may initiate a PC5 connection setup or modification procedure for communication with WTRU1 via the selected new end-to-end route. WTRU2 may send a direct communication request (DCR) including an indication of whether multihop relay may be used and the selected end-to-end route ([WTRU2, Relay4, Relay2, and WTRU1]) to Relay4 if WTRU2 has no PC5 connection with Relay4, or WTRU2 may send a Link modification request including a selected end-to-end route to Relay4 if WTRU2 has an existing PC5 connection with Relay4.

[0137] After sending a DCR or LMR to Relay4, a security association procedure may be performed between WTRU2 and Relay4.

[0138] After sending DCR or LMR, WTRU2 may receive DC accept or LM accept for the requested end- to-end route from Relay4, for example, if end-to-end connection setup for a selected new route may be successful. An Accept message may also include the selected end-to-end route information.

[0139] Relay4 may send DC accept or LM accept to WTRU2, for example, after receiving DC accept or LM accept from Relay2 at 8.

[0140] After PC5 connection setup with Relay4, WTRU2 may perform an IP address assignment procedure, for example, by obtaining an IP address from Relay4 which works as DHCP server, or by assigning link local IP address.

[0141] Referring to FIG. 2, at 8, after receiving DCR or LMR for a new end-to-end route from WTRU2, Relay4 may trigger new PC5 connection setup or modification of existing PC5 connection with an entity ata next hop in the end-to-end route (e.g., Relay2). In DCR or LMR, selected end-to-end route information may be included.

[0142] After sending DCR to Relay2, a security association procedure may be performed between Relay2 and Relay4.

[0143] After sending DCR or LMR, Relay4 may receive DC accept or LM accept for the requested end- to-end route from Relay2, for example, if Relay2 may be successfully performed at 9. An accept message may also include the selected end-to-end route information.

[0144] Relay2 may send DC accept or LM accept to Relay4, for example, after receiving DC accept or LM accept from WTRU1 at 9.

[0145] Referring to FIG. 2, at 9, after receiving DCR or LMR for a new end-to-end route from Relay4, Relay2 may trigger a new PC5 connection setup or modification of an existing PC5 connection with an entity at a next hop in the end-to-end route (e.g., WTRU1). In DCR or LMR, selected end-to-end route information may be included.

[0146] After sending DCR to WTRU1 , a security association procedure may be performed between WTRU1 and Relay2.

[0147] After sending DCR or LMR, Relay2 may receive DC accept or LM accept for the requested end- to-end route from WTRU1. An accept message may also include the selected end-to-end route information.

[0148] WTRU1 may send DC accept or LM accept to Relay2 if accepting the requested PC5 link setup or link modification for communication to WTRU2 via an end-to-end route.

[0149] After PC5 connection setup with Relay2, WTRU1 may perform an IP address assignment procedure, for example, by obtaining an IP address from Relay2 which may work as a DHCP server or by assigning a link local IP address.

[0150] Referring to FIG. 2, at 10, after selecting a new end-to-end route to WTRU1 , WTRU2 may send a Link Modification Accept message to Relay 1 . A Link Modification Accept message may include information of a new end-to-end route (e.g., [WTRU2, Relay4, Relay2, and WTRU1]), an IP address of WTRU1, an IP address of WTRU2, a new IP address of WTRU2 at the newly selected end-to-end route (e.g., IP address assigned by relay4), and a Relay re-selection indication.

[0151] If WTRU1 receives a new IP address of WTRU2 at the newly selected end-to-end route, WTRU1 may determine the IP address of WTRU2 may be the IP address assigned by Relay4 which may be in the selected end-to-end route.

[0152] Referring to FIG. 2, at 11 , Relay 1 may send a Link Modification Accept message to WTRU1 . The Link Modification Accept message may include information of a new end-to-end route (e.g., [WTRU2, Relay4, Relay2, and WTRU1]), an IP address of WTRU1 , an IP address of WTRU2, a new IP address of WTRU2 at the newly selected end-to-end route (e.g., an IP address assigned by Relay4), and a Relay reselection indication.

[0153] Referring to FIG. 2, at 12, after receiving a Link Modification Accept message from Rel ay 1 , WTRU1 may acknowledge a newly selected end-to-end path to WTRU2 (e.g., [WTRU2, Relay4, Relay2, and WTRUI]).

[0154] Referring to FIG. 2, at 13, WTRU1 may send a Link Modification Ack to Relayl . A Link Modification Ack may include the IP address of WTRU1 at the newly selected end-to-end route (e.g., IP address assigned by Relay2), an IP address of the responding WTRU (e.g., WTRU2), and an indication of Relay reselection.

[0155] Referring to FIG. 2, at 14, Relayl may send Link Modification Ack to WTRU2. A Link Modification Ack may include the IP address of WTRU1 at the newly selected end-to-end route (e.g., IP address assigned by Relay2), an IP address of WTRU1, an IP address of the responding WTRU (e.g., WTRU2) and an indication of Relay reselection. Relayl may release, e.g., implicitly release, the link between Relayl and WTRU1 . The link may be kept between Relayl and WTRU1 if that relay serves WTRU1 as a relay for another WTRU-to-WTRU relay connection or multihop WTRU-to-WTRU relay connection. The same may apply for the PC5 link between Relayl and WTRU2.

[0156] Referring to FIG. 2, at 15, WTRU1 and WTRU2 may transfer traffic via the newly selected end-to- end route. In an example, WTRU1 and WTRU2 may transfer data via Relay2 and Relay4.

[0157] A negotiated Layer 3 WTRU-to-WTRU Relay reselection procedure with multihop relay discovery at an initiating End WTRU may be provided. Disclosed is a negotiated Layer-3 WTRU-to-WTRU relay reselection procedure with multihop relay discovery support using a provided list of WTRU-to-WTRU relays which may include relays reachable directly or via multihop by an Initiating End WTRU (e.g., WTRU1).

[0158] If a relay reselection may be triggered at WTRU1 , WTRU1 may perform discovery procedures which may include, for example, multihop relay discovery procedures.

[0159] Based on a list of candidate WTRU-to-WTRU relays received from WTRU1 , a responding End WTRU (e.g., WTRU2) may select a new WTRU-to-WTRU route and WTRU2 may consider multihop routes from a candidate list. WTRU2 may perform WTRU-to-WTRU relay discovery procedure to check the reachability of candidate relay WTRUs.

[0160] WTRU2 may select the end-to-end route to WTRU1 based on the received information from discovery, may initiate a PC5 connection setup procedure, and may send the selected route to WTRU1 .

[0161] During this negotiated WTRU-to-WTRU relay reselection procedure, WTRU1 and WTRU2 may exchange their new IP address to be used via the newly selected end-to-end route.

[0162] FIG. 3 depicts an example Layer3 based Negotiated WTRU-to-WTRU Relay reselection procedure with multihop relay discovery at an initiating end WTRU.

[0163] Referring to FIG. 3, at 0, WTRU1 and WTRU2 may be authorized for multihop WTRU-to-WTRU Relay service as End WTRUs and may be provisioned with parameters for discovery and connection setup with other WTRUs via multihop WTRU-to-WTRU Relay services.

[0164] Relayl , Relay2, Relay3, and Relay4 may be authorized for multihop WTRU-to-WTRU Relay service as Relay WTRUs and may be provisioned with parameters for discovery and connection setup with other WTRUs and relay WTRUs via multihop WTRU-to-WTRU Relay services.

[0165] The provisioned parameters for each WTRU may include parameters such as, for example, RSC (Relay Service Code(s)), lists of PLMNs, and User Info IDs of WTRUs for application, which may be allowed at a multihop relay connection.

[0166] Referring to FIG. 3, at 1 , WTRU1 and WTRU2 may set up a PC5 connection with Relayl for communication between WTRU1 and WTRU2. WTRU1 and WTRU2 may exchange data traffic, e.g., IP traffic, via Relayl .

[0167] Referring to FIG. 3, at 2, WTRU1 (which may be referred to as an initiating End WTRU) may determine based on, for example, PC5 signal strength, to perform WTRU-to-WTRU Relay reselection.

[0168] Referring to FIG. 3, at 3, WTRU1 may obtain a list of WTRU-to-WTRU Relays which may be accessible by WTRU1 in direct PC5 connection. The list of WTRU-to-WTRU Relays may include the WTRU-to-WTRU Relays which have PC5 connection with WTRU1 and the WTRU-to-WTRU Relays from which WTRU1 received WTRU-to-WTRU Relay Discovery Announcement messages or WTRU-to-WTRU Relay Discovery Response messages in response to Discovery Solicitation messages sent by WTRU1 .WTRU1 may initiate WTRU-to-WTRU Relay discovery procedures to find the candidate WTRU-to-WTRU Relays.

[0169] WTRU1 may initiate a multihop WTRU-to-WTRU relay discovery procedure with a target WTRU (e.g., WTRU2) to find an end-to-end route via multihop relays to WTRU2.

[0170] WTRU1 may determine the candidate WTRU-to-WTRU Relays from a list of discovered WTRU- to-WTRU Relays and candidate end-to-end routes to WTRU2 via multihop relay based on, for example, signal strength, delay for sending and responding messages, number of hops of an end-to-end route, end-to-end delay associated with an end-to-end route, Relay Service Code for WTRU-to-WTRU Relay services supported by WTRU-to-WTRU Relay, whether WTRU-to-WTRU Relay supports multihop WTRU-to-WTRU Relay services, and / or supported traffic type, e.g., IP traffic, Ethernet traffic, etc.

[0171] Referring to FIG. 3, at 4, WTRU1 may send a Link Modification Request message to Relayl . Link Modification Request may include a Relay re-selection indication, information of candidate WTRU-to-WTRU Relay(s), information of candidate end-to-end route via multihop relay (e.g., [WTRU1 , Relay2, Relay4, WTRU2]), IP addresses of the responding End WTRUs (e.g., WTRU2), and / or an IP address of WTRUI .

[0172] For each WTRU-to-WTRU Relay in candidate WTRU-to-WTRU Relay(s), WTRU1 may include an indication whether the WTRU-to-WTRU relay supports multihop WTRU-to-WTRU Relay services.

[0173] Multiple End WTRUs’ IP addresses may be included at responding End WTRUs if WTRU1 may be communicating with multiple End WTRUs via Relayl .

[0174] If multiple End WTRUs’ IP addresses may be included at responding End WTRUs, for each responding end WTRU, information of candidate end-to-end route via multihop relay to the end WTRU may be added in the Link Modification Request message.

[0175] Referring to FIG. 3, at 5, based on received End WTRUs’ IP addresses determined at 4, Relayl may determine the responding End WTRUs (e.g., WTRU2) and may send a Link Modification Request message to the responding End WTRUs (e.g., WTRU2).

[0176] The Link Modification Request message may include, for example, a Relay re-selection indication, User Info ID(s) of the candidate WTRU-to-WTRU Relay(s), information of candidate end-to-end routes via multihop relay, and / or IP address of WTRUI .

[0177] For each WTRU-to-WTRU Relay in candidate WTRU-to-WTRU Relay(s), an indication of whether the WTRU-to-WTRU relay supports multihop WTRU-to-WTRU Relay services may be included if received at 4.

[0178] If multiple End WTRUs may be specified in the Link Modification Request message received from WTRU1 , Relayl may send a PC5 Link Modification Request to each of the End WTRUs.

[0179] Referring to FIG. 3, at 6, if receiving Link Modification Request for Relay reselection sent at 5, WTRU2 may select a new WTRU-to-WTRU Relay from the candidate WTRU-to-WTRU Relays or may select a new end-to-end route from candidate end-to-end routes via multihop relay. WTRU2 may select a proper end-to-end route (e.g., a selected end-to-end route may be [WTRU2, Relay4, Relay2, and WTRU1]) including a WTRU-to-WTRU relay or multihop WTRU-to-WTRU relays for new end-to-end connection to WTRU1 based, for example, on received candidate WTRU-to-WTRU Relay(s) and candidate end-to-endroutes via multihop relay, a discovery result at 6, link quality, number of hops in an end-to-end route, end- to-end delay associated with an end-to-end route, etc.

[0180] WTRU2 may initiate a WTRU-to-WTRU relay discovery procedure with target WTRU-to-WTRU Relay(s) in the received candidate WTRU-to-WTRU relays and candidate end-to-end routes via multihop relay.

[0181] Referring to FIG. 3, at 7, based on a selected end-to-end route (e.g., [WTRU2, Relay4, Relay2, and WTRU1]), WTRU2 may initiate PC5 connection setup or modification procedure for communication with WTRU1 via the selected new route. WTRU2 may send DCR including a selected end-to-end route to Relay4 if WTRU2 has no PC5 connection with Relay4 or WTRU2 may send a Link modification request including a selected end-to-end route to Relay4 if WTRU2 has existing PC5 connection with Relay4.

[0182] After sending DCR or LMR to Relay4, a security association procedure may be performed between WTRU2 and Relay4 (e.g., if needed).

[0183] After sending DCR or LMR, WTRU2 may receive DC accept or LM accept for the requested end- to-end route from Relay4, for example, if end-to-end connection setup for a selected new route may be successful. An accept message may also include the selected end-to-end route information.

[0184] Relay4 may send DC Accept or LM accept to WTRU2, for example, after receiving DC accept or LM accept from Relay2 at 8.

[0185] After PC5 connection setup with Relay4, WTRU1 may perform IP address assignment procedure by, for example, getting an IP address from Relay4 which works as a DHCP server or by assigning a link local IP address.

[0186] Referring to FIG. 3, at 8, after receiving DCR or LMR for new end-to-end route from WTRU2, Relay4 may trigger new PC5 connection setup or modification of existing PC5 connection with an entity at a next hop in the end-to-end route (e.g., Relay2). In DCR or LMR, selected end-to-end route information may be included.

[0187] After sending DCR to Relay2, security association procedure may be performed between Relay2 and Relay4 (e.g., if needed).

[0188] After sending DCR or LMR, Relay4 may receive DC accept or LM accept for the requested end- to-end route from Relay2, for example, if Relay2 successfully performed at 9. An accept message may also include the selected end-to-end route information.

[0189] Relay2 may send DC accept or LM accept to Relay4, for example, after receiving DC accept or LM accept from WTRU1 at 9.

[0190] Referring to FIG. 3, at 9, after receiving DCR or LMR for new end-to-end route from Relay4, Relay2 may trigger new PC5 connection setup or modification of an existing PC5 connection with an entity at a next hop in the end-to-end route (e.g., WTRU1). In DCR or LMR, selected end-to-end route information may be included.

[0191] After sending DCR to WTRU1 , a security association procedure may be performed between WTRU1 and Relay2 (e.g., if needed).

[0192] After sending DCR or LMR, Relay2 may receive DC accept or LM accept for the requested end- to-end route from WTRU1. An accept message may also include the selected end-to-end route information.

[0193] WTRU1 may send DC accept or LM accept to Relay2 if accepting the requested PC5 link setup or link modification for communication to WTRU2 via the end-to-end route.

[0194] After PC5 connection setup with Relay2, WTRU1 may perform IP address assignment procedure by, for example, getting an IP address from Relay2 which works as DHCP server or by assigning a link local IP address.

[0195] Referring to FIG. 3, at 10, after selecting a new end-to-end route to WTRU1 , WTRU2 may send a Link Modification Accept message to Relayl . A Link Modification Accept message may include information of a new end-to-end route (e.g., [WTRU2, Relay4, Relay2, and WTRU1]), an IP address of WTRU1, an IP address of WTRU2, a new IP address of WTRU2 at a newly selected end-to-end route (e.g., IP address assigned by Relay4), and a Relay re-selection indication.

[0196] Referring to FIG. 3, at 11 , Relayl may send a Link Modification Accept message to WTRU1. The Link Modification Accept message may include information of a new end-to-end route (e.g., [WTRU2, Relay4, Relay2, and WTRU1]), an IP address of WTRU1 , an IP address of WTRU2, a new IP address of WTRU2 at newly selected end-to-end route (e.g., IP address assigned by Relay4), and a Relay re-selection indication.

[0197] Referring to FIG. 3, at 12, after receiving a Link Modification Accept message from Relayl , WTRU1 may acknowledge the newly selected end-to-end path to WTRU2. (e.g., [WTRU2, Relay4, Relay2, and WTRLH]).

[0198] Referring to FIG. 3, at 13, WTRU1 may send Link Modification Ack to relayl . Link Modification Ack may include, for example, the IP address of WTRU1 at a newly selected end-to-end route (e.g., IP address assigned by Relay2), an IP address of a responding WTRU (e.g., WTRU2) and a Relay reselection indication.

[0199] Referring to FIG. 3 at 14, Relayl may send Link Modification Ack to WTRU2. Link ModificationAck may include the IP address of WTRU1 at a newly selected end-to-end route (e.g., IP address assignedby Relay2), an IP address of WTRU1, an IP address of a responding WTRU (e.g., WTRU), and a Relay reselection indication. Relayl may release, e.g., may implicitly release, the link between Relayl and WTRU1. The link may be kept between relayl and WTRU1 if that relay may be serving WTRU1 as relay for other WTRU-to-WTRU relay connection or multihop WTRU-to-WTRU relay connection. The same may apply for the PC5 link between Relayl and WTRU2.

[0200] Referring to FIG. 3, at 15, WTRU1 and WTRU2 may transfer traffic via the newly selected end-to- end route (e.g., via Relay2 and Relay4).

[0201] A negotiated Layer 2 WTRU-to-WTRU Relay reselection procedure with multihop relay discovery may be provided.

[0202] FIG. 4 depicts example processing for Layer2 based Negotiated WTRU-to-WTRU Relay reselection procedure.

[0203] Referring to FIG. 4, at 0, WTRU1 and WTRU2 may be authorized for multihop WTRU-to-WTRU Relay service as End WTRUs and may be provisioned with parameters for discovery and connection setup with other WTRUs via multihop WTRU-to-WTRU Relay services.

[0204] Relayl , Relay2, Relay3, and Relay4 may be authorized for multihop WTRU-to-WTRU Relay service as a Relay WTRU and may be provisioned with parameters for discovery and connection setup with other WTRUs and Relay WTRUs via multihop WTRU-to-WTRU Relay services.

[0205] The provisioned parameter for each WTRU may include parameters such as, for example, RSC (Relay service Code(s)), a list of PLMN, and User Info ID of the WTRU for application, which may be allowed at multihop relay connection.

[0206] Referring to FIG. 4 at 1 , WTRU1 and WTRU2 may establish or set up a PC5 connection with Relayl for end-to-end communication between WTRU1 and WTRU2. WTRU1 and WTRU2 may exchange data traffic via Relayl .

[0207] Referring to FIG. 4, at 2, WTRU1 , which may be considered an initiating End WTRU, may determine based on, for example, PC5 signal strength, to perform WTRU-to-WTRU Relay reselection.

[0208] Referring to FIG. 4, at 3, WTRU1 may obtain a list of WTRU-to-WTRU Relays which may be accessible by WTRU1 in direct PC5 connection. The list of WTRU-to-WTRU Relays may include the WTRU-to-WTRU Relays which have PC5 connection with WTRU1 and the WTRU-to-WTRU Relays from which WTRU1 received WTRU-to-WTRU Relay Discovery Announcement messages or a WTRU-to-WTRU Relay Discovery Response message in response to a Discovery Solicitation message sent by WTRU1 . WTRU1 may initiate WTRU-to-WTRU Relay discovery procedures to find the candidate WTRU-to-WTRU Relays.

[0209] WTRU1 may initiate multihop WTRU-to-WTRU relay discovery procedures with a target WTRU (e.g., WTRU2) to find an end-to-end route via multihop relays to WTRU2.

[0210] WTRU1 may determine the candidate WTRU-to-WTRU Relays from a list of WTRU-to-WTRU Relays and candidate end-to-end routes to WTRU2 via multihop relay based on, for example, signal strength, delay in sending and responding messages, number of hops of an end-to-end route, end-to-end delay associated with an end-to-end route, Relay Service Code for WTRU-to-WTRU Relay services supported by WTRU-to-WTRU Relay, whether WTRU-to-WTRU Relay supports multihop WTRU-to-WTRU Relay services, and / or supported traffic type such as, for example, IP traffic, Ethernet traffic, etc.

[0211] Referring to FIG. 4, at 4, WTRU1 may send a Link Modification Request message to WTRU2, via Relayl . Link Modification Request may include a relay re-selection indication, information of candidate WTRU-to-WTRU Relay(s), information of candidate end-to-end route via multihop relay (e.g., [WTRU1 , Relay2, Relay4, WTRU2]), information of responding End WTRUs (e.g., WTRU2).

[0212] For each WTRU-to-WTRU Relay in candidate WTRU-to-WTRI Relay(s), WTRU1 may include an indication of whether the WTRU-to-WTRU Relay supports multihop WTRU-to-WTRU Relay services.

[0213] If WTRU1 may be communicating with multiple End WTRUs via a Relay, WTRU1 may send a link modification request for reselection with candidate end-to-end routes via multihop relays to each End WTRU which has end-to-end connection via Relayl .

[0214] Referring to FIG. 4, at 5, if receiving Link Modification Request for Relay reselection sent at 5, WTRU2 may select a new WTRU-to-WTRU Relay from the candidate WTRU-to-WTRU Relays or may select a new end-to-end route from candidate end-to-end routes via multihop relay. WTRU2 may select an end-to-end route (e.g., a selected end-to-end route may be [WTRU2, Relay4, Relay2, and WTRU1]) including a WTRU-to-WTRU relay or multihop WTRU-to-WTRU relays for new end-to-end connection to WTRU1 based on, for example, received candidate WTRU-to-WTRU Relay(s) and candidate end-to-end route via multihop relay, the discovery result at 6 of FIG. 4, link quality, a number of hops of an end-to-end route, and end-to-end delay associated with an end-to-end route, etc.

[0215] WTRU2 may initiate WTRU-to-WTRU relay discovery procedure with target WTRU-to-WTRU Relay(s) in the received candidate WTRU-to-WTRU relays and candidate end-to-end route via multihop relay.

[0216] Referring to FIG. 4, at 6, after selecting a new end-to-end route to WTRU1 , WTRU2 may send a Link Modification Accept message to WTRU1 via Relayl . Link Modification Accept message may include information of a new end-to-end route (e.g., [WTRU2, Relay4, Relay2, and WTRU1]), information of WTRU2, information of WTRU1 , and Relay re-selection indication.

[0217] Referring to FIG. 4, at 7, after exchanging new end-to-end route information, based on a selected end-to-end route (e.g., [WTRU2, Relay4, Relay2, and WTRU1]), WTRU1 or WTRU2 may initiate PC5 link setup procedure or PC5 link modification procedure with corresponding Relay WTRU (Relay2 or Relay4) for end-to-end connection setup between WTRU1 and WTRU2. The DCR or LMR message for end-to-end connection setup may include newly selected end-to-end route information (e.g., [WTRU2, Relay4, Relay2, and WTRUI]).

[0218] After successful end-to-end connection setup, WTRU1 and WTRU2 may transfer traffic via the newly selected end-to-end route (e.g., via Relay2 and Relay4).

[0219] Although features and elements described herein are described in particular combinations, each feature or element may be used alone without the other features and elements of the preferred embodiments, or in various combinations with or without other features and elements.

[0220] The description herein may be provided for exemplary purposes and does not limit in any way the applicability of the described systems, methods, and instrumentalities to other wireless technologies and / or to wireless technology using different principles, when applicable. The term network in this disclosure may refer to one or more gNBs which in turn may be associated with one or more Transmission / Reception Points (TRPs) or any other node in the radio access network.

[0221] Although the implementations described herein may consider 3GPP specific protocols, it is understood that the implementations described herein are not restricted to this scenario and may be applicable to other wireless systems. For example, although the solutions described herein consider LTE, LTE-A, New Radio (NR) or 5G specific protocols, it is understood that the solutions described herein are not restricted to this scenario and are applicable to other wireless systems as well.

[0222] The processes described herein may be implemented in a computer program, software, and / or firmware incorporated in a computer-readble medium for execution by a computer and / or processor.Examples of computer-readable media include, but are not limited to, electronic signals (transmitted over wired and / or wireless connections) and / or computer-readable storage media. Examples of computer- readable storage media include, but are not limited to, a read only memory (ROM), a random access memory (RAM), a register, cache memory, semiconductor memory devices, magnetic media such as, but not limited to, internal hard disks and removable disks, magneto-optical media, and / or optical media such as compact disc (CD)-ROM disks, and / or digital versatile disks (DVDs). A processor in association with software may be used to implement a radio frequency transceiver for use in a WTRU, terminal, base station, RNC, and / or any host computer.

Claims

CLAIMSWhat is Claimed:1 . A wireless transmit and receive unit (WTRU), comprising: a processor configured to: send a link modification request to a second WTRU, the link modification request comprising an indication of WTRU-to-WTRU relay reselection, an indication of candidate WTRU-to-WTRU relays, and an indication multihop relay is supported; receive from the second WTRU a link modification accept message, the link modification accept message indicating a selected end-to-end route including at least one of the candidate WTRU-to-WTRU relays; and send a link modification acknowledgement message to the second WTRU.

2. The WTRU of claim 1 , wherein the link modification accept message indicating the selected end-to-end route comprises an indication of a first end WTRU, an indication of a second end WTRU, and a list of relays between the first end WTRU and the second end WTRU.

3. The WTRU of claim 2, wherein the link modification accept message indicating the selected end- to-end route further comprises an IP address associated with the second WTRU.

4. The WTRU of claim 3, wherein the link modification acknowledgement message comprises an IP address associated with the WTRU.

5. The WTRU of claim 1 , wherein the processor is further configured to send a PC5 link request to establish the selected end-to-end route.

6. A wireless transmit and receive unit (WTRU), comprising: a processor configured to:receive from a second WTRU a link modification request, the link modification request comprising an indication of WTRU-to-WTRU relay reselection, an indication of candidate WTRU-to-WTRU relays, and an indication multihop relay is supported; perform a multihop WTRU-to-WTRU relay discovery procedure to discover available end-to-end routes to the second WTRU; select one of the available end-to-end routes to the second WTRU; send to the second WTRU a link modification accept message, the link modification accept message indicating a selected end-to-end route including at least one of the candidate WTRU-to-WTRU relays; and receive from the second WTRU a link modification acknowledgement message.

7. The WTRU of claim 6, wherein the link modification accept message indicating the selected end-to-end route comprises an indication of a first end WTRU, an indication of a second end WTRU, and a list of relays between the first end WTRU and the second end WTRU.

8. The WTRU of claim 7, wherein the link modification accept message indicating the selected end- to-end route further comprises an IP address associated with the WTRU.

9. The WTRU of claim 8, wherein the link modification acknowledgement message comprises an IP address associated with the second WTRU.

10. The WTRU of claim 6, wherein the processor is further configured to send a PC5 link request to establish the selected end-to-end route.

11. A method of relay link modification, comprising: a first wireless transmit and receive unit (WTRU) sending a link modification request to a second WTRU, the link modification request comprising an indication of WTRU-to-WTRU relay reselection, an indication of candidate WTRU-to-WTRU relays, and an indication multihop relay is supported; the first WTRU receiving from the second WTRU a link modification accept message, the link modification accept message indicating a selected end-to-end route including at least one of the candidate WTRU-to-WTRU relays; andthe first WTRU sending a link modification acknowledgement message to the second WTRU.

12. The method of claim 11 , wherein the link modification accept message indicating the selected end-to-end route comprises an indication of a first end WTRU, an indication of a second end WTRU, and a list of relays between the first end WTRU and the second end WTRU.

13. The method of claim 12, wherein the link modification accept message indicating the selected end- to-end route further comprises an IP address associated with the second WTRU.

14. The method of claim 13, wherein the link modification acknowledgement message comprises an IP address associated with the WTRU.

15. The method of claim 11 , further comprising: the first WTRU sending a PC5 link request to establish the selected end-to-end route.

16. A method of relay link modification, comprising: a first wireless transmit and receive unit (WTRU) receiving from a second WTRU a link modification request, the link modification request comprising an indication of WTRU-to-WTRU relay reselection, an indication of candidate WTRU-to-WTRU relays, and an indication multihop relay is supported; the first WTRU performing a multihop WTRU-to-WTRU relay discovery procedure to discover available end-to-end routes to the second WTRU; the first WTRU selecting one of the available end-to-end routes to the second WTRU; the first WTRU sending to the second WTRU a link modification accept message, the link modification accept message indicating a selected end-to-end route including at least one of the candidate WTRU-to-WTRU relays; and the first WTRU receiving from the second WTRU a link modification acknowledgement message.

17. The method of claim 16, wherein the link modification accept message indicating the selected end-to-end route comprises an indication of a first end WTRU, an indication of a second end WTRU, and a list of relays between the first end WTRU and the second end WTRU.

18. The method of claim 17, wherein the link modification accept message indicating the selected end-to-end route further comprises an IP address associated with the WTRU.

19. The method of claim 18, wherein the link modification acknowledgement message comprises an IP address associated with the second WTRU.

20. The method of claim 16, further comprising: the first WTRU sending a PC5 link request to establish the selected end-to-end route.21 . A wireless transmit and receive unit (WTRU), comprising: a processor configured to: discover end-to-end routes via multihop relay to a second WTRU; select candidate end-to-end routes to the second WTRU; send a link modification request to the second WTRU, the link modification request comprising an indication of WTRU-to-WTRU relay reselection and an indication of the candidate end-to-end routes to the second WTRU; receive a link modification accept message from the second WTRU, the link modification accept message indicating a selected end-to-end route; and perform an end-to-end connection setup procedure with the second WTRU via the selected end-to- end route.

22. The WTRU of claim 21 , wherein the processor configured to select the candidate end-to-end routes to the second WTRU is configured to select the candidate end-to-end routes based on whether WTRU-to-WTRU relays in the candidate end-to-end routes support multihop WTRU-to-WTRU relay services.

23. The WTRU of claim 21 , wherein the indication of the candidate end-to-end routes to the second WTRU comprises, for each candidate end-to-end route, an indication of a first end WTRU, an indication of a second end WTRU, and a list of relays between the first end WTRU and the second end WTRU.

24. The WTRU of claim 21 ,wherein the link modification accept message comprises for the selected end-to-end route, an indication of a first end WTRU, an indication of a second end WTRU, and a list of relays between the first end WTRU and the second end WTRU.

25. The WTRU of claim 21 , wherein the end-to-end connection setup procedure is a PC5 link setup procedure.

26. A wireless transmit and receive unit (WTRU), comprising: a processor configured to: receive a link modification request from a second WTRU, the link modification request comprising an indication of WTRU-to-WTRU relay reselection and an indication of candidate end-to-end routes to the second WTRU; determine a selected end-to-end route from the candidate end-to-end routes; send a link modification accept message to the second WTRU, the link modification accept message indicating the selected end-to-end route; and perform an end-to-end connection setup procedure with the second WTRU via the selected end-to- end route.

27. The WTRU of claim 26, wherein the indication of the candidate end-to-end routes to the second WTRU comprise, for each candidate end-to-end route, an indication of a first end WTRU, an indication of a second end WTRU, and a list of relays between the first end WTRU and the second end WTRU.

28. The WTRU of claim 26, wherein the processor configured to determine the selected end-to-end route from the candidate end-to-end routes is configured to determine the selected end-to-end route based on one or more of link quality, number of hops, or communication delay.

29. The WTRU of claim 26, wherein the end-to-end connection setup procedure is a PC5 link setup procedure.

30. The WTRU of claim 26,wherein the link modification accept message further comprises an IP address associated with theWTRU.31 . A method of relay link modification, comprising: discovering end-to-end routes via multihop relay to a second WTRU; selecting candidate end-to-end routes to the second WTRU; sending a link modification request to the second WTRU, the link modification request comprising an indication of WTRU-to-WTRU relay reselection and an indication of the candidate end-to-end routes to the second WTRU; receiving a link modification accept message from the second WTRU, the link modification accept message indicating a selected end-to-end route; and performing an end-to-end connection setup procedure with the second WTRU via the selected end-to-end route.

32. The method of claim 31 , wherein selecting the candidate end-to-end routes to the second WTRU comprises selecting the candidate end-to-end routes based on whether WTRU-to-WTRU relays in the candidate end-to-end routes support multihop WTRU-to-WTRU relay services.

33. The method of claim 31 , wherein the indication of the candidate end-to-end routes to the second WTRU comprises, for each candidate end-to-end route, an indication of a first end WTRU, an indication of a second end WTRU, and a list of relays between the first end WTRU and the second end WTRU.

34. The method of claim 31 , wherein the link modification accept message comprises for the selected end-to-end route, an indication of a first end WTRU, an indication of a second end WTRU, and a list of relays between the first end WTRU and the second end WTRU.

35. The method of claim 31 , wherein the end-to-end connection setup procedure is a PC5 link setup procedure.

36. A method of relay link modification, comprising:receiving a link modification request from a second WTRU, the link modification request comprising an indication of WTRU-to-WTRU relay reselection and an indication of candidate end-to-end routes to the second WTRU; determining a selected end-to-end route from the candidate end-to-end routes; sending a link modification accept message to the second WTRU, the link modification accept message indicating the selected end-to-end route; and performing an end-to-end connection setup procedure with the second WTRU via the selected end-to-end route.

37. The method of claim 36, wherein the indication of the candidate end-to-end routes to the second WTRU comprise, for each candidate end-to-end route, an indication of a first end WTRU, an indication of a second end WTRU, and a list of relays between the first end WTRU and the second end WTRU.

38. The method of claim 36, wherein determining the selected end-to-end route from the candidate end-to-end routes comprises determining the selected end-to-end route based on one or more of link quality, number of hops, or communication delay.

39. The method of claim 36, wherein the end-to-end connection setup procedure is a PC5 link setup procedure.

40. The method of claim 36, wherein the link modification accept message further comprises an IP address associated with theWTRU.

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