Method and apparatus for integrated discovery support via UE to UE relay

Abstract

In an embodiment, a method implemented in a first wireless transmit / receive unit, WTRU, for performing integrated discovery when there is an existing sidelink connection between a first WTRU or a second WTRU and at least one WTRU-to-WTRU relay includes: sending a direct communication request message to the second WTRU via the at least one WTRU-to-WTRU relay, the direct communication request message including proximity-based service parameters; receiving a link change request message from the second WTRU via one of the at least one WTRU-to-WTRU relay, the link change request message including information related to the proximity-based service parameters; sending a link change response to one of the at least one WTRU-to-WTRU relay; and receiving a direct communication accept message from one of the at least one WTRU-to-WTRU relay.

Description

[Technical Field]

[0001] In general, the present disclosure is directed to the fields of communications, software, and / or encoding, including, for example, methods, architectures, apparatus, and systems directed to integrated discovery support by UE to UE (user equipment to user equipment) relays. [Background technology]

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 63 / 436,736, filed January 3, 2023, and U.S. Provisional Patent Application No. 63 / 444,460, filed February 9, 2023, each of which is incorporated by reference herein in its entirety.

[0003] For discovery integrated with PC5 unicast link establishment (so-called integrated discovery), the source user equipment (source UE) may send a direct communication request (DCR) message in a broadcast manner without selecting a UE-to-UE relay, so that many UE-to-UE relays may send / forward the DCR to the target UE. After sending / forwarding the DCR message, each UE-to-UE relay may expect a response with a Direct Communication Accept (DCA) message from the target UE. After receiving the DCA message, one UE-to-UE relay may respond / forward with a DCA message to the source UE.

[0004] However, PC5 link sharing should be used. More specifically, when there is (e.g., already is) an existing PC5 connection between the end user equipment (end UE) and the UE to UE relay, the existing PC5 link should be reused (e.g., using a link modification procedure) instead of establishing a new PC5 link.

[0005] Furthermore, when the source UE uses a service-oriented PC5 link setup (e.g., the target UE's user information is not included in the DCR message), the UE-to-UE relay has no information about the target UE with which the source UE may communicate.

[0006] From a protocol perspective, a race condition may occur between the DCR message / DCA message and the link change procedure and needs to be resolved. For example, a UE-to-UE relay may receive a DCR message from a source UE, trigger a DCR to the target UE, and respond either by sending a DCA message or by initiating a link change procedure. Similarly, a UE-to-UE relay may respond to the source UE by sending a DCA message or by initiating a link change procedure.

[0007] Therefore, it must be clarified how the UE to UE relay is triggered to send a response to the source UE containing a DCA message when link modification is used with the target UE, and how the source UE determines whether the DCR message has been responded to when the link modification procedure is performed between the UE to UE relay and the source UE.

[0008] Furthermore, for the Layer 3 (L3) relay case, end-to-end Quality of Service (QoS) may be requested by the source UE, and the QoS for each PC5 connection may be determined by the UE-to-UE relay. For the integrated discovery case, it is clarified how the PC5 QoS is configured.

[0009] When Integrated Discovery is used, there is a need to define a PC5 link establishment procedure between two end UEs via UE to UE Relay. Summary of the Invention

[0010] In an embodiment, a method implemented in a first wireless transmit / receive unit (WTRU) performing integrated discovery when there is an existing sidelink connection between the first or second WTRU and at least one WTRU-to-WTRU relay may include transmitting a direct communication request (DCR) message to the second WTRU via the at least one WTRU-to-WTRU relay, the direct communication request (DCR) message including proximity-based service (ProSe) parameters. The method may further include receiving a link change request message from the second WTRU via one of the at least one WTRU-to-WTRU relay, the link change request message including information related to the ProSe parameters. The method may further include transmitting a link change response message to one of the at least one WTRU-to-WTRU relay and receiving a direct communication accept (DCA) message from one of the at least one WTRU-to-WTRU relay.

[0011] In another embodiment, a method implemented in a WTRU-to-WTRU relay may include receiving a DCR message from a first WTRU, the DCR message including information including quality of service (QoS) information related to proximity-based services. The method may further include determining a first value of a QoS parameter for a link between the first WTRU and the WTRU-to-WTRU relay. The method may further include transmitting the DCR message to a second WTRU. The method may further include receiving from the second WTRU a second value of a QoS parameter for a link between the second WTRU and the WTRU-to-WTRU relay, and determining whether direct communication between the first WTRU and the second WTRU is accepted based on the first value of the QoS parameter and the second value of the QoS parameter.

[0012] In another embodiment, a method implemented in a wireless transmit / receive unit (WTRU) that performs integrated discovery may include receiving a direct communication request message from each WTRU-to-WTRU relay of a first set of WTRU-to-WTRU relays, the direct communication request message including a first communication request from a first source WTRU. The method may include receiving a link change request message from each WTRU-to-WTRU relay of a second set of WTRU-to-WTRU relays, the link change request message including a second communication request from the first source WTRU. The method may include selecting a WTRU-to-WTRU relay from among the first and second sets of WTRU-to-WTRU relays for communication with the first source WTRU, and sending a link change reject message to all WTRU-to-WTRU relays of the second set of WTRU-to-WTRU relays that are not selected for communication with the source WTRU.

[0013] Under the condition that the selected WTRU-to-WTRU relay is from a first set of WTRU-to-WTRU relays and an existing sidelink connection between the WTRU and the selected WTRU-to-WTRU relay is already established, the method may include transmitting a direct communication reject message to the selected WTRU-to-WTRU relay. The method may include performing a link change procedure by the selected WTRU-to-WTRU relay to modify the existing sidelink connection. Selecting the WTRU-to-WTRU relay may include selecting from among the first and second sets of WTRU-to-WTRU relays a third set of WTRU-to-WTRU relays to send a direct communication request message or a link change request message originating from the same source WTRU for the same ProSe service as the WTRU, and selecting the WTRU-to-WTRU relay from the third set of WTRU-to-WTRU relays based on any of signal strength, local policy, and operator policy per relay service code. Under a condition that the selected WTRU-to-WTRU relay is from the first set of WTRU-to-WTRU relays, the method may include sending a direct communication accept message to the selected WTRU-to-WTRU relay and sending another link change reject message to all WTRU-to-WTRU relays in the second set of WTRU-to-WTRU relays. The direct communication request message and the link change request message may include information indicative of any of proximity-based services, information related to the source WTRU information, and information related to the WTRU. The direct communication accept message may be sent in a unicast manner. The link change request message may be sent in a unicast manner. The another link change reject message and the link change reject message may be sent in a unicast manner.

[0014] In an embodiment, a wireless transmit / receive unit (WTRU) including a processor, a transceiver unit, and a storage unit may be configured to receive, from each WTRU-to-WTRU relay of a first set of WTRU-to-WTRU relays, a DCR message including a first communication request from a first source WTRU. The WTRU may be configured to receive, from each WTRU-to-WTRU relay of a second set of WTRU-to-WTRU relays, a link change request message including a second communication request from the first source WTRU. The WTRU may be configured to select a WTRU-to-WTRU relay from among the first and second sets of WTRU-to-WTRU relays for communication with the first source WTRU, and to send link change reject messages to WTRU-to-WTRU relays of the second set of WTRU-to-WTRU relays that are not selected for communication with the source WTRU.

[0015] A more detailed understanding may be had from the following detailed description, given by way of example in conjunction with the drawings attached hereto. The figures in the drawings, as well as the detailed description, are examples. In the strictest sense, the figure(s) and detailed description are not to be considered limiting, and other equally effective examples are possible and likely. Moreover, like reference numerals ("ref") in the drawings indicate like elements. [Brief explanation of the drawings]

[0016] [Figure 1A] FIG. 1 is a system diagram illustrating an example communication system. [Figure 1B] 1B is a system diagram illustrating an example WTRU (Wireless Transmit / Receive Unit) that may be used within the communication system illustrated in FIG. 1A. [Figure 1C] 1B is a system diagram illustrating an example RAN (Radio Access Network) and an example CN (Core Network) that may be used within the communication system illustrated in FIG. 1A. [Figure 1D]FIG. 1B is a system diagram illustrating a further exemplary RAN and a further exemplary CN that may be used within the communication system illustrated in FIG. 1A. [Figure 2] 10 is an example message sequence chart for Proximity-Based Service (ProSe) discovery integrated into a sidelink establishment procedure. [Figure 3] 10 is an example message sequence chart of an integrated discovery with link change procedure between a wireless transmit / receive unit (WTRU) and a WTRU to WTRU relay. [Figure 4] 10 is an example message sequence chart of an integrated discovery procedure between a WTRU and a WTRU to WTRU relay with a link change reject / accept procedure. [Figure 5] 10 is an example message sequence chart of an integrated discovery procedure between a WTRU to WTRU relay and a WTRU with direct communication reject; [Figure 6] 1 is a flow chart diagram illustrating an example method implemented in a WTRU that performs integrated discovery according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] In the detailed description that follows, numerous specific details are set forth to provide a thorough understanding of the embodiments and / or examples disclosed herein. It will be understood, however, that the above-described embodiments and examples may be practiced without some or all of the specific details set forth herein. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to obscure the description that follows. Moreover, embodiments and examples not specifically described herein may be practiced in place of, or in combination with, the embodiments and other examples explicitly, implicitly, and / or inherently described, disclosed, or otherwise provided herein (collectively "provided"). Although various embodiments are described and / or claimed herein in which apparatuses, systems, devices, etc. and / or any elements perform operations, processes, algorithms, functions, etc. and / or any parts, it will be understood that any embodiment described and / or claimed herein assumes that any apparatus, system, device, etc. and / or any element is configured to perform any operation, process, algorithm, function, etc. and / or any part. The methods, apparatus, and systems provided herein are well suited for communications involving both wired and wireless networks. An overview of various types of wireless devices and infrastructure is provided with respect to Figures 1A-1D, and various elements of the networks may utilize, perform, be arranged in accordance with, and / or be adapted and / or configured for the methods, apparatus, and systems provided herein.

[0018] 1A is a system diagram of an exemplary communication system in which one or more disclosed embodiments may be implemented. Communication system 100 may be a multiple-access system that provides content, such as voice, data, video, messaging, broadcasts, etc., to multiple wireless users. Communication system 100 may enable multiple wireless users to access such content through sharing of system resources, including wireless bandwidth. For example, the communication system 100 may employ one or more channel access methods such as, for example, CDMA (Code Division Multiple Access), TDMA (Time Division Multiple Access), FDMA (Frequency Division Multiple Access), OFDMA (Orthogonal Frequency Division Multiple Access), SC-FDMA (Single Carrier FDMA), ZT UW DTS-s OFDM (ZT (Zero-tail) UW (Unique-word) DFT (Discreet Fourier Transform) Spread OFDM), UW-OFDM (Unique Word OFDM), resource block-filtered OFDM, filter bank multicarrier (FBMC), and the like.

[0019] 1A, communications system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, radio access networks (RANs) 104 / 113, core networks (CNs) 106 / 115, public switched telephone networks (PSTNs) 108, the Internet 110, and other networks 112, although it will be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of 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 may all be referred to as “stations” and / or “STAs,” may be configured to transmit and / or receive wireless signals, and may include (or be) user equipment (UE), mobile stations, fixed or mobile subscriber units, subscription-based units, pagers, cellular phones, personal digital assistants (PDAs), smartphones, laptops, netbooks, personal computers, wireless sensors, hotspots or Mi-Fi devices, Internet of Things (IoT) devices, watches or other wearables, head-mounted displays (HMDs), vehicles, drones, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in the context of industrial and / or automated processing chains), consumer electronics devices, devices operating on commercial and / or industrial wireless networks, and the like. Any of the WTRUs 102a, 102b, 102c, and 102d may be referred to interchangeably as UEs.

[0020] Further, the communications system 100 may 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, e.g., to facilitate access to one or more communications networks, such as the CN 106 / 115, the Internet 110, and / or the network 112. By way of example, the base stations 114a, 114b may be any of a BTS (wireless base station equipment), a Node-B (NB), an eNode-B (eNB), a HNB (home Node-B), a HeNB (home eNode-B), a gNB (gNode-B), a NR NB (NR Node-B), a site controller, an AP (access point), a wireless router, and the like. While the base stations 114a, 114b are each depicted as a single element, it will be understood that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0021] The base station 114a may be part of the RAN 104 / 113, which may further include other base stations and / or network elements (not shown), such as, for example, a base station controller (BSC), a radio network controller (RNC), relay nodes, etc. The base station 114a and / or base station 114b may be configured to transmit and / or receive wireless signals on one or more carrier frequencies and may be referred to as a cell (not shown). The frequencies may be licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide coverage for wireless services over a particular geographic area, which may be relatively fixed or may change over time. Furthermore, a cell may be divided into cell sectors. For example, the cell associated with the base station 114a may be divided into three sectors. Thus, in an embodiment, the base station 514a 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 or every sector of the cell. For example, beamforming may be used to transmit and / or receive signals in a desired spatial direction.

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

[0023] More specifically, as mentioned above, the communication system 100 may be a multiple-access system and may employ one or more channel access schemes, such as, for example, CDMA, TDMA, FDMA, OFDMA, SC-FDMA, etc. 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 116 using, for example, wideband CDMA (WCDMA). WCDMA may include communication protocols such as, for example, High-Speed ​​Packet Access (HSPA) and / or Evolved HSPA+ (HSPA+). HSPA may include High-Speed ​​Downlink Packet Access (HSDPA) and / or High-Speed ​​Uplink Packet Access (HSUPA).

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

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

[0026] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may implement both LTE radio access and NR radio access, e.g., using dual connectivity (DC) principles. Thus, the air interface utilized by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions sent to / from multiple types of base stations (e.g., eNBs and gNBs).

[0027] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a wireless technology such as, for example, IEEE 802.11 (i.e., Wireless Fidelity (Wi-Fi)), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000EV-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), GERAN (GSM EDGE), or the like.

[0028] 1A may be, for example, a wireless router, a Home Node-B, a Home eNode-B, or an access point and may utilize any suitable RAT to facilitate wireless connectivity in a localized area, such as, for example, a business, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a roadway, etc. In an embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as, for example, 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, for example, IEEE 802.15, to establish a wireless personal area network (WPAN). In an 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.) that establishes either a small cell, a pico cell, or a femto cell. As shown in FIG. 1A, 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.

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

[0030] Additionally, the CN 106 / 115 may serve as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or other networks 112. The PSTN 108 may include a circuit-switched telephone network providing 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, for example, transmission control protocol (TCP), user datagram protocol (UDP), and / or IP in the TCP / IP (internet protocol) Internet protocol suite. The network 112 may include wired and / or wireless communication networks owned and / or operated by other service providers. For example, the network 112 may include another CN connected to one or more RANs that may employ the same RAT as the RAN 104 / 114 or a different RAT.

[0031] 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 separate wireless networks over separate wireless links). For example, the WTRU 102c shown in FIG. 1A may be configured to communicate with a base station 114a, which may employ a cellular-based radio technology, and with a base station 114b, which may employ an IEEE 802.11 radio technology.

[0032] 1B is a system diagram illustrating an example WTRU 102. As shown in FIG. 1B, the WTRU 102 may include, among other things, a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a GPS (Global Positioning System) chipset 136, and / or other elements / peripherals 138. It will be understood that the WTRU 102 may include any sub-combination of the above elements without departing from the spirit and scope of the present invention.

[0033] The processor 118 may be a general-purpose processor, a special-purpose processor, a conventional processor, a digital signal processor (DSP), multiple microprocessors, one or more microprocessors in conjunction with a DSP core, a controller, a microcontroller, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) circuit, any of other types of integrated circuits (ICs), a state machine, etc. The processor 118 may perform signal coding, data processing, power control, input / output processing, and / or any other function that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to a transceiver 120, which may be coupled to a transmit / receive element 122. While FIG. 1B depicts the processor 118 and the transceiver 120 as separate components, it will be understood that the processor 118 and the transceiver 120 may be integrated together, for example, in an electronic package or chip.

[0034] The transmit / receive element 122 may be configured to transmit or receive signals to a base station (e.g., base station 114a) over the air interface 116. For example, in an 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, for example, IR, UV, or visible light signals. In an embodiment, the transmit / receive element 122 may be configured to transmit and / or receive both RF and light signals. It will be understood that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

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

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

[0037] The processor 118 of the WTRU 102 may be coupled to and may receive user input data through a speaker / microphone 124, a keypad 126, and / or a display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light-emitting diode (OLED) display unit). Additionally, the processor 118 may output user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. Furthermore, the processor 118 may access information and store data in any suitable type of memory, such as non-removable memory 130 and / or 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 118 may access information and store data in memory that is not physically located in the WTRU 102, such as in a server or host computer (not shown).

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

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

[0040] Additionally, the processor 118 may be coupled to other elements / peripherals 138, which may include one or more software and / or hardware modules / units that provide additional features, functionality, and / or wired or wireless connectivity. For example, the elements / peripherals 138 may include an accelerometer, an e-compass, a satellite transceiver, a digital camera (e.g., for photos and / or videos), a Universal Serial Bus (USB) port, a vibration device, a television transceiver, a hands-free headset, a Bluetooth module, a frequency modulated FM (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, etc. The elements / peripherals 138 may include one or more sensors, which may be one or more of a gyroscope, an accelerometer, a Hall effect sensor, a magnetometer, a direction 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.

[0041] The WTRU 102 may include a full-duplex radio where transmission and reception of some or all of the signals (e.g., associated with a particular subframe for both the uplink (e.g., for transmission) and downlink (e.g., for reception)) may be parallel and / or simultaneous. The full-duplex radio may include an interference management unit to reduce and or substantially eliminate self-interference, either by hardware (e.g., a choke) or signal processing by a processor (e.g., by a separate processor (not shown) or by the processor 118). In an embodiment, the WTRU 102 may include a half-duplex radio where transmission and reception of some or all of the signals (e.g., associated with a particular subframe for either the uplink (e.g., for transmission) or downlink (e.g., for reception)) may be half-duplex.

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

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

[0044] Each of the eNode-Bs 160a, 160b, and 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 uplink (UL) and / or downlink (DL), etc. As shown in FIG. 1C , the eNode-Bs 160a, 160b, 160c may communicate with each other via an X2 interface.

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

[0046] The MME 162 may be connected to each of the eNode-Bs 160a, 160b, and 160c in the RAN 104 via an S1 interface and may act as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, activating / deactivating bearers, selecting a particular serving gateway during initial attach of the WTRUs 102a, 102b, 102c, etc. 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, for example, GSM and / or WCDMA.

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

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

[0049] The CN 106 may facilitate communication 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 communication between the WTRUs 102a, 102b, 102c and traditional landline communication devices. For example, the CN 106 may include or communicate with an IP gateway (e.g., an IMS (IP Multimedia Subsystem) 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 other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers.

[0050] Although the WTRU is described in Figures 1A-1D as a wireless terminal, it is expected that in certain exemplary embodiments, such a terminal may use a wired communication interface (e.g., temporarily or permanently) with the communication network.

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

[0052] A WLAN in infrastructure basic service set (BSS) mode may have an access point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP may have access or interface to a distribution system (DS) or another type of wired / wireless network that carries traffic into and out of the BSS. Traffic to a STA originating from outside the BSS may arrive through the AP and be delivered to the STA. Traffic originating from a STA to a destination outside the BSS may be sent to the AP for delivery to the respective destination. Traffic between STAs within a BSS may be sent through the AP, for example, where a source STA may send traffic to the AP, and the AP may deliver the traffic to the destination STA. Traffic between STAs within a BSS may be considered and / or referred to as peer-to-peer traffic. Peer-to-peer traffic may be sent between (e.g., directly between) a source and destination STA via a direct link setup (DLS). In one exemplary embodiment, the DLS may use 802.11e DLS or 802.11z tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may not have an AP, and STAs within or using the IBSS (e.g., all STAs) may communicate directly with each other. The IBSS mode of communication is sometimes referred to herein as an "ad hoc" mode of communication.

[0053] When using the 802.11ac infrastructure mode of operation or a similar mode of operation, an AP may transmit beacons on a fixed channel, such as a primary channel. The primary channel may be a fixed width (e.g., a 20 MHz wide bandwidth) or a width that is dynamically set by signaling. The primary channel may be the operating channel of the BSS and may be used by STAs to establish a connection with the AP. In a typical embodiment, CSMA / CA (Carrier Sense Multiple Access / Collision Avoidance) may be implemented in an 802.11 system, for example. With CSMA / CA, 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 in a given BSS at any given time.

[0054] For example, a HT (high throughput) STA may use a 40 MHz wide channel for communication by combining a 20 MHz primary channel with adjacent or non-adjacent 20 MHz channels to form a 40 MHz wide channel.

[0055] A very high throughput (VHT) STA may support channels of 20 MHz, 40 MHz, 80 MHz, and / or 160 MHz width. A 40 MHz and / or 80 MHz channel may be constructed by combining contiguous 20 MHz channels. A 160 MHz channel may be constructed by combining eight contiguous 20 MHz channels or by combining two non-contiguous 80 MHz channels, sometimes referred to as an 80+80 configuration. For the 80+80 configuration, after channel encoding, the data may pass through a segment parser, which may split the data into two streams. IFFT (inverse fast Fourier transform) processing and time-domain processing may be performed on each stream separately. The streams may be mapped onto two 80 MHz channels, and the data may be transmitted by the transmitting STA. At the receiver of the receiving STA, the operations for the 80+80 configuration described above may be reversed and the combined data may be sent to the MAC (Media Access Control) layer, etc.

[0056] Sub-1 GHz modes of operation are supported by 802.11af and 802.11ah. The operating bandwidths of the channels and carriers are reduced in 802.11af and 802.11ah compared to those used in 802.11n and 802.11ac. 802.11af supports 5 MHz, 10 MHz, and 20 MHz bandwidths in the TVWS (TV White Space) spectrum, while 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. According to an exemplary embodiment, 802.11ah may support meter-type control / machine-type communication, such as MTC devices in macro coverage areas. MTC devices may have limited capabilities, including support (e.g., only support) for some and / or limited bandwidths. An MTC device may include a battery with a battery life above a threshold (eg, to maintain a very long battery life).

[0057] A WLAN system that may support multiple channels and channel bandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, includes a channel that may be designated as a 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 the STA that supports the smallest bandwidth operating mode among all STAs operating in the BSS. In an 802.11ah example, the primary channel may be 1 MHz wide for a STA (e.g., an MTC-type device) that supports (e.g., only supports) the 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) setting may depend on the state of the primary channel. If the primary channel is busy, for example, due to a STA (that only supports a 1 MHz mode of operation) transmitting to the AP, the entire available frequency band may be considered busy even though most of the frequency band may remain idle and available.

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

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

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

[0061] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with scalable numerology. For example, the OFDM symbol spacing and / or OFDM subcarrier spacing may vary for separate transmissions, separate cells, and / or separate portions of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using subframes or transmission time intervals (TTIs) of different or scalable lengths (e.g., including different numbers of OFDM symbols and / or different absolute time lengths with persistence).

[0062] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c without accessing another RAN (e.g., eNode-Bs 160a, 160b, 160c, etc.). In a standalone configuration, the WTRUs 102a, 102b, 102c may utilize one or more of the gNBs 180a, 180b, 180c as mobility anchor points. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using signals in unlicensed bands. In a non-standalone configuration, the WTRUs 102a, 102b, 102c may communicate / connect with a gNB 180a, 180b, 180c while also communicating / connecting with another RAN, such as, for example, an eNode-B 160a, 160b, 160c. For example, the WTRUs 102a, 102b, 102c may implement DC principles to communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c substantially simultaneously. In a non-standalone configuration, the eNode-Bs 160a, 160b, 160c may act as mobility anchors for the WTRUs 102a, 102b, 102c, and the gNBs 180a, 180b, 180c may provide additional coverage and / or throughput in serving the WTRUs 102a, 102b, 102c.

[0063] 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 for network slicing, dual connectivity, interworking between NR and E-UTRA, routing of user plane data to user plane functions (UPFs) 184a, 184b, routing of control plane information to access and mobility management functions (AMFs) 182a, 182b, etc. As shown in FIG. 1D , the gNBs 180a, 180b, 180c may communicate with each other via an Xn interface.

[0064] 1D may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one SMF (Session Management Function) 183a, 183b, and possibly a DN (Data Network) 185a, 185b. While each of the above elements is depicted as part of the CN 115, it will be understood that any of the just-mentioned elements may be owned and / or operated by an entity other than the CN operator.

[0065] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via an N2 interface and may act as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, supporting network slicing (e.g., handling sessions of separate protocol data units (PDUs) with separate requirements), selecting a particular SMF 183a, 183b, managing registration areas, terminating NAS signaling, mobility management, etc. Network slicing may be used by the AMF 182a, 182b to customize CN support for the WTRUs 102a, 102b, 102c, for example, based on the type of service being utilized for the WTRUs 102a, 102b, 102c. For example, separate network slices may be established for separate use cases, e.g., services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced massive mobile broadband (eMBB) access, services related to MTC access, etc. The AMF 162 may provide control plane functionality for switching between the RAN 113 and other RANs (not shown) employing other radio technologies, e.g., LTE, LTE-A, LTE-A Pro, etc., and / or non-3GPP access technologies, e.g., Wi-Fi.

[0066] The SMFs 183a and 183b may be connected to the AMFs 182a and 182b in the CN 115 via an N11 interface. Additionally, the SMFs 183a and 183b may be connected to the UPFs 184a and 184b in the CN 115 via an N4 interface. The SMFs 183a and 183b may select and control the UPFs 184a and 184b and configure the routing of traffic through the UPFs 184a and 184b. The SMFs 183a and 183b may perform other functions, such as managing and assigning UE IP addresses, managing PDU sessions, controlling policy enforcement and QoS, providing downlink data notification, etc. The PDU session type may be IP-based, non-IP-based, Ethernet-based, etc.

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

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

[0069] 1A-1D and the corresponding description thereof, one or more or all of the functions described herein in connection with one or more of the WTRUs 102a-d, base stations 114a-b, eNode-Bs 160a-c, MME 162, SGW 164, PGW 166, gNBs 180a-c, AMFs 182a-b, UPFs 184a-b, SMFs 183a-b, DNs 185a-b, and / or any other element(s) or device(s) described herein may be performed by one or more emulation elements / devices (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 functionality.

[0070] The emulation device may be designed to implement one or more tests of other devices in a lab environment and / or in an operator's network environment. For example, one or more emulation devices may perform one or more, or all, functions while fully or partially implemented and / or deployed as part of a wired and / or wireless communications network to test other devices in the communications network. One or more emulation devices may perform one or more, or all, functions while temporarily implemented / deployed as part of a wired and / or wireless communications network. The emulation device (e.g., a network node) may be directly coupled to another device for testing purposes and / or may perform testing using over-the-air (OTA) wireless communications.

[0071] The one or more emulation devices may perform one or more functions, including all functions, while not implemented / deployed as part of a network node (wired and / or wireless communication network). For example, the emulation devices may be utilized in testing scenarios in a testing laboratory and / or in an undeployed (e.g., testing) wired and / or wireless communication network to implement testing of one or more components. The one or more emulation devices may be test equipment. Direct RF coupling and / or wireless communication via RF circuitry (which may include, e.g., one or more antennas) may be used by the emulation devices to transmit and / or receive data.

[0072] Proximity-based services (ProSe) include services that may be provided by a 5G system based on WTRUs in close proximity to each other. 5G ProSe may have functionality such as 5G ProSe direct discovery, 5G ProSe direct communication, 5G ProSe WTRU to network relay, and 5G ProSe WTRU to WTRU relay.

[0073] In 5G ProSe, after establishing a unicast link between two WTRUs, several unicast link management procedures may be defined.

[0074] The first unicast link management procedure may be a Layer 2 link release over a PC5 reference point. Accordingly, the WTRUs may release the Layer 2 link by exchanging a Disconnect Request message and a Disconnect Response message. When releasing the Layer 2 link, the WTRUs may delete all context data associated with the Layer 2 link, and the ProSe layer of each WTRU may notify the access stratum (AS) layer that the unicast link has been released, along with a PC5 link identifier indicating the released unicast link.

[0075] The second unicast link management procedure may be a Layer 2 link change for the unicast link. If the WTRU needs to add new PC5 QoS flow(s), modify existing QoS flow(s), or delete existing QoS flow(s) to an existing PC5 unicast link, the WTRU may exchange a Link Change Request message and a Link Modify Response message with the requested action, associated QoS information, and optional PC5 QoS rules. The QoS information may include information about the PC5 QoS flow(s), and for each PC5 QoS flow, a PC5 QoS flow identifier (PFI), corresponding PC5 QoS parameters (e.g., PQI (PC5 5G NR Standardized QoS identifier), and other conditional parameters, such as maximum flow bit rate / guaranteed flow bit rate), and optionally associated ProSe identifier(s). The ProSe layer of each WTRU may provide information about the unicast link change to the AS layer. What has just been described allows the AS layer to update the context related to the modified unicast link.

[0076] A third unicast link management procedure may be Layer 2 link maintenance over the PC5 reference point. The WTRU may exchange keep-alive and keep-alive Ack messages to detect whether a particular PC5 unicast link is still valid. The keep-alive procedure may be initiated, for example, based on a trigger from the AS layer or an internal timer. The WTRU may minimize keep-alive signaling, for example, cancel the procedure if data is successfully received over the PC5 unicast link. A WTRU that initiates the keep-alive procedure may decide on follow-up action based on the result of the signaling, for example, proceed with implicit Layer 2 link release.

[0077] 5G ProSe may define multiple functions, such as, for example, 5G ProSe direct discovery, 5G ProSe direct communication, 5G ProSe WTRU to network relay, and 5G ProSe WTRU to WTRU relay. 5G ProSe WTRU to WTRU relay may enable indirect communication between two 5G ProSe End UEs (e.g., end WTRUs). With respect to 5G ProSe WTRU to WTRU relay, 5G ProSe WTRU to WTRU relay discovery and 5G ProSe communication via WTRU to WTRU relay may be defined.

[0078] For 5G ProSe WTRU to WTRU relay discovery, both Model A and Model B discovery are supported. Model A may use a single discovery protocol message (Announcement). Model B may use two discovery protocol messages (Solicitation and Response).

[0079] Additionally, discovery integrated into the PC5 unicast link establishment procedure may be supported.

[0080] 5G ProSe communication via WTRU-to-WTRU relay may be possible by 5G ProSe Layer 2 WTRU-to-WTRU relay or 5G ProSe Layer 3 WTRU-to-WTRU relay. For Layer 2 WTRU-to-WTRU relay and Layer 3 WTRU-to-WTRU relay, 5G ProSe communication setup by discovery procedure may be defined. Discovery integrated into PC5 unicast link establishment procedure may be defined.

[0081] With Layer 2 WTRU to WTRU relay, an end-to-end PC5 link may be established between end UEs (e.g., end WTRUs) via the WTRU to WTRU relay. PC5 signaling messages may then be exchanged between the end UEs (e.g., end WTRUs).

[0082] With Layer 3 WTRU to WTRU relay, each end UE (e.g., end WTRU) establishes a PC5 link with the WTRU to WTRU relay, and the WTRU to WTRU relay may forward messages toward the end UE (e.g., end WTRU). PC5 signaling messages may be exchanged between the end UE and the WTRU to WTRU relay.

[0083] Discovery integrated with PC5 unicast link establishment (so-called integrated discovery) may combine the discovery procedure with unicast connection setup via the WTRU-to-WTRU relay by omitting the procedure for 5G ProSe WTRU-to-WTRU relay discovery. One advantage of the above procedure is that the remote WTRU and WTRU relay do not need to perform standalone 5G ProSe WTRU-to-WTRU relay discovery.

[0084] For discovery integrated with PC5 link establishment, when a WTRU enables a WTRU-to-WTRU relay to be included in a direct communication request (DCR) message to other WTRUs, the WTRU may indicate this by including a relay_indication in the broadcasted DCR message. Direct communication may be referred to interchangeably as relay communication.

[0085] When a WTRU-to-WTRU relay receives a DCR message with a relay_indication, the WTRU-to-WTRU relay may join the procedure and broadcast the DCR message to its neighbors without a relay_indication.

[0086] Figure 2 is an example message sequence chart of 5G ProSe discovery integrated into a sidelink (e.g., PC5 unicast link) establishment procedure.

[0087] In the direct communication request from the source WTRU (UE-1), only the requested ProSe service information may be included without the user information of the target WTRU (UE-2), which is called a service-oriented PC5 link setup. In the case just described, if there is a target WTRU (UE-2) interested in the ProSe service requested by the source WTRU (UE-1), the target WTRU (UE-2) may respond to the direct communication request directly to the source WTRU (UE-1) or via a WTRU-to-WTRU relay (relay-1 or relay-2).

[0088] If the direct communication request from the source WTRU (UE-1) includes user information of the target WTRU (UE-2), it is called a user-oriented PC5 link setup, and only the requested target WTRU (UE-2) may respond to the direct communication request directly to the source WTRU (UE-1) or via a WTRU-to-WTRU relay (relay-1 or relay-2).

[0089] In step 1, multiple WTRU-to-WTRU relays (relay-1 and relay-2) may receive a DCR message from the source WTRU (UE-1). The DCR message broadcast by the source WTRU (UE-1) may include a relay_indication enable command.

[0090] In step 2 and step 3, when the target WTRU (UE-2) receives DCR messages from one or more WTRU-to-WTRU relays (relay-1 and relay-2), the target WTRU (UE-2) may select a WTRU-to-WTRU relay to which the target WTRU (UE-2) will respond.

[0091] In step 5, the target WTRU (UE-2) may send a DCA message to the selected WTRU-to-WTRU relay (relay-1).

[0092] In step 8, the selected WTRU-to-WTRU relay (Relay-1) may send a DCA message to the source WTRU (UE-1).

[0093] In step 4, a security establishment procedure may occur between the target WTRU (UE-2) and the selected WTRU-to-WTRU relay (relay-1). In step 7, a security establishment procedure may occur between the source WTRU (UE-1) and the selected WTRU-to-WTRU relay (relay-1).

[0094] In step 6, an IP address allocation procedure may occur between the target WTRU (UE-2) and the selected WTRU-to-WTRU relay (relay-1). In step 9, an IP address allocation procedure may occur between the source WTRU (UE-1) and the selected WTRU-to-WTRU relay (relay-1).

[0095] Furthermore, when one source WTRU communicates with multiple target WTRUs, the sidelink (e.g., PC5 link) between the source WTRU and the WTRU-to-WTRU relay may be shared for multiple target WTRUs per relay service code (RSC), but a sidelink (e.g., PC5 link) may be established separately between the WTRU-to-WTRU relay and the target WTRU for each RSC. For a shared sidelink (e.g., PC5 link), a Layer 2 link modification procedure may be used. The same principles for a shared sidelink (e.g., PC5 link) may apply to a target WTRU communicating with multiple source WTRUs.

[0096] The following description describes an example of a sidelink (e.g., PC5 link) establishment procedure between two WTRUs (e.g., two end UEs) via a WTRU-to-WTRU relay when integrated discovery is used. More specifically, the sharing of a sidelink (e.g., PC5 link) between a WTRU (e.g., end UE) and a WTRU-to-WTRU relay via the use of a sidelink (e.g., PC5 link) modification procedure is described.

[0097] In an embodiment, when there is an existing sidelink (e.g., PC5) connection between a source WTRU and a WTRU to WTRU relay, and / or between a WTRU to WTRU and a target WTRU, a method for performing integrated discovery may be characterized by the following functionality: resolution of conflicting signaling transactions between direct communication request / accept messages and link modification request / response messages; and resolution of conflicting end-to-end QoS negotiations between direct communication request / accept messages and link modification request / response messages.

[0098] The DCR and DCA messages may be used to set up new sidelink (e.g., PC5) connections, and the Link Change Request and Response messages may be used to modify existing sidelink (e.g., PC5) connections for sidelink (e.g., PC5) sharing purposes. The DCR message may be sent in a broadcast manner. The DCA message may be sent in a unicast manner. The Link Change Request and Response messages may be sent in a unicast manner.

[0099] If the source WTRU sends a DCR message to the target WTRU, the source WTRU may expect to receive DCA from the target WTRU or from the WTRU-to-WTRU relay. If the source WTRU sends a link change request message to the target WTRU, the source WTRU may expect a link change response from the target WTRU. If the DCR message or link change request message is not responded to until some timer expires, the source WTRU may retransmit the DCR message or link change request message to the target WTRU. However, when there is an existing link between the source WTRU and the WTRU-to-WTRU relay that can be shared for communication with other target WTRUs, the source WTRU or WTRU-to-WTRU relay sending the DCR message may not receive a DCA message in response but may receive a link change request message due to link sharing.

[0100] In an embodiment, if the source WTRU sends a DCR message to the target WTRU in a broadcast manner, the source WTRU may consider the request message to be responded to upon receiving a DCA message or a Link Change Request message from the target WTRU with appropriate parameters (e.g., the same ProSe and associated QoS parameters as requested in the Direct Communication Request message, and / or the target WTRU's target user information, source user information).

[0101] Additionally, in embodiments, a message containing a transaction number may be used to check whether a message has been acknowledged. For example, if a DCR message is sent with a transaction number value, it may be considered to have been received if a DCA message is received with the same transaction number value. If a Link Change Request message is received by the source WTRU with the same value as the transaction number of the DCR message, the source WTRU may consider the DCR message to have been acknowledged.

[0102] Alternatively, in an embodiment, if the source WTRU receives a link change request message from the target WTRU (in response to the DCR message) after the source WTRU sends a DCR message to the target WTRU in a broadcast manner, the source WTRU may consider that the DCR is no longer in use and drop any procedures related to the direct communication request message.

[0103] For end-to-end QoS management, if the source WTRU requests a connection with the target WTRU via a WTRU-to-WTRU relay, it may include requested ProSe information and end-to-end QoS requirements for the ProSe. Based on the requested end-to-end QoS requirements, the WTRU-to-WTRU relay may set QoS requirements (e.g., per hop) for the sidelink (e.g., PC5 link) between the source WTRU and the WTRU-to-WTRU relay, and for the sidelink (e.g., PC5 link) between the WTRU-to-WTRU relay and the target WTRU.

[0104] If the source WTRU requests end-to-end QoS requirements, the WTRU-to-WTRU relay may respond to the source WTRU with the (e.g., per-hop) QoS requirements for the link between the source WTRU and the WTRU-to-WTRU relay after negotiating the (e.g., per-hop) QoS requirements for other links between the target WTRU and the WTRU-to-WTRU relay.

[0105] If the WTRU to WTRU relay sends at least one QoS parameter for the link between the target WTRU and the WTRU to WTRU relay (e.g., per hop) for the end-to-end connection between the source WTRU and the target WTRU, the WTRU to WTRU relay may consider the end-to-end connection to be accepted if the target WTRU responds (e.g., per hop) with the same value for at least one QoS parameter for the link between the target WTRU and the WTRU to WTRU relay.

[0106] If the WTRU-to-WTRU relay sends QoS parameters for the link between the target WTRU and the WTRU-to-WTRU relay (e.g., hop-by-hop) for the end-to-end connection between the source WTRU and the target WTRU, if the target WTRU responds with different (e.g., hop-by-hop) QoS parameter values ​​for the link between the target WTRU and the WTRU-to-WTRU relay than those sent by the WTRU-to-WTRU relay, the WTRU-to-WTRU relay may check whether this is acceptable. If not, the WTRU-to-WTRU relay may consider the end-to-end connection rejected.

[0107] If the QoS parameters of the link between the target WTRU and the WTRU to WTRU relay are agreed upon, based on the values ​​and end-to-end QoS requirements, the WTRU to WTRU relay may calculate the QoS parameters of the link between the source WTRU and the WTRU to WTRU relay.

[0108] FIG. 3 is an example message sequence chart of an integrated discovery with link change procedure between a WTRU to WTRU relay and a WTRU (eg, an end UE).

[0109] In step 0, the WTRUs (UE-1 and UE-2) may be authorized and provisioned with parameters to use the services provided by the WTRU-to-WTRU relays (relay-1 and relay-2). Additionally, the WTRU-to-WTRU relays (relay-1 and relay-2) may be authorized and provisioned with parameters to provide services to relay traffic between the WTRUs (UE-1 and UE-2).

[0110] In step 1, the source WTRU (UE-1) may broadcast a DCR message to initiate unicast communication with the target WTRU (UE-2). The DCR message may include a relay_indication, source WTRU (UE-1) user information, target WTRU (UE-2) user information, and application ID, if any, as well as a WTRU-to-WTRU relay service code. The source WTRU (UE-1) may include the requested ProSe service and QoS information related to the ProSe service.

[0111] The source WTRU (UE-1) may send a DCR message without indicating any target WTRU user information when the source WTRU (UE-1) requests connection setup with any target WTRU that supports the requested ProSe service.

[0112] The source WTRU (UE-1) may include the value of the message transaction number in the DCR message.

[0113] In step 2, the WTRU-to-WTRU relays (relay-1 and relay-2) may receive a DCR message with a relay_indication from the source WTRU (UE-1). The WTRU-to-WTRU relays (relay-1 and relay-2) may decide to participate in the procedure and broadcast another DCR message (e.g., in their vicinity) without a relay_indication.

[0114] Each DCR message from each of the WTRU-to-WTRU relays may include source WTRU user information (UE-1 user information), target WTRU user information (UE-2 user information), and WTRU-to-WTRU relay information. The DCR message from either of the WTRU-to-WTRU relays (relay-1 or relay-2) may include the requested ProSe service received in step 1 and derived QoS information related to the ProSe service for the link between the WTRU-to-WTRU relay and the target WTRU (UE-2).

[0115] When the DCR from the source WTRU (UE-1) received by the WTRU-to-WTRU relays (relay-1 and relay-2) does not include the target WTRU (UE-2) user information, the DCR from each WTRU-to-WTRU relay (relay-1 and relay-2) does not include the target WTRU (UE-2) user information.

[0116] The WTRU to WTRU relays (Relay-1 and Relay-2) may include a different value for the message transaction number for their DCR messages.

[0117] In step 3, if the target WTRU (UE-2) receives DCRs from one or more WTRU-to-WTRU relays (relay-1 and relay-2), the target WTRU (UE-2) may select a WTRU-to-WTRU relay to which the target WTRU (UE-2) will respond. The target WTRU (UE-2) may select a WTRU-to-WTRU relay according to signal strength from the WTRU-to-WTRU relay, local policy, and operator policy per relay service code, if any.

[0118] If the DRC received by the target WTRU (UE-2) does not include user information of the target WTRU (UE-2), the target WTRU (UE-2) may decide to respond to the requested DCR if it supports the requested ProSe service.

[0119] In the case of an existing sidelink (e.g., PC5) connection between the target WTRU (UE-2) and the selected WTRU-to-WTRU relay, steps 4 and 5 may be performed, and steps 6 to 8 may be omitted.

[0120] If the target WTRU (UE-2) needs to set up a new sidelink (e.g., PC5) connection with the selected WTRU-to-WTRU relay, steps 4 and 5 may be omitted and steps 6 to 8 may be performed.

[0121] In step 4, the target WTRU (UE-2) may respond to the DCR message from the selected WTRU-to-WTRU relay (relay-1) by sending a link change request message to the WTRU-to-WTRU relay (relay-1). The link change request message may include source WTRU (UE-1) user information, target WTRU (UE-2) user information, and WTRU-to-WTRU relay (relay-1) information. The link change request message may include the requested ProSe service for the link between the selected WTRU-to-WTRU relay (relay-1) and the target UE and QoS information related to the ProSe service, as received in step 2.

[0122] The link modification request message may include the same message transaction number value as received in step 2 from the selected WTRU to WTRU relay (relay-1).

[0123] Alternatively, the target WTRU (UE-2) may include the requested ProSe service as received in step 2 and QoS information related to the ProSe service for the link between the WTRU to WTRU relay (relay-1) and the target WTRU, modified from the value received in step 2 at the discretion of the target WTRU.

[0124] In step 5, if the WTRU to WTRU relay (relay-1) receives a link change request message containing the user information of the source WTRU (UE-1) and the user information of the target WTRU (UE-2) as contained in the DCR message sent in step 2, the WTRU to WTRU relay (relay-1) may consider the DCR message to be responded to. Alternatively, if the link change request message contains the same value as the message transaction number of the DCR sent in step 2, the WTRU to WTRU relay (relay-1) may consider the DCR message sent in step 2 to be responded to by a link change request from the target WTRU (UE-2).

[0125] In step 6, if necessary, security establishment occurs between the target WTRU (UE-2) and the selected (eg, 5G ProSe) WTRU to WTRU relay (relay-1).

[0126] In step 7, the target WTRU (UE-2) may return a DCA message to the WTRU-to-WTRU relay (relay-1). The DCA message may include source WTRU (UE-1) user information, target WTRU (UE-2) user information, and WTRU-to-WTRU relay (relay-1) information relay-1. The DCA message may include the requested ProSe service and QoS information related to the ProSe service for the link between the relay UE and the target UE as received in step 2.

[0127] The DCA message may contain the same message transaction number value as received in step 2 from the selected relay.

[0128] In step 8, for IP traffic, an IPv6 prefix or an IPv4 address is assigned to the target (e.g., 5G ProSe Layer 3) WTRU (UE-2).

[0129] If the DCR message sent in step 2 is successfully responded to in steps 4-5 or in steps 6-8, the WTRU to WTRU relay (Relay-1) may respond with the DCR message sent from the source WTRU (UE-2) in step 1.

[0130] If there is an existing sidelink (e.g., PC5) connection between the source WTRU (UE-1) and the WTRU to WTRU relay (relay-1), steps 9 and 10 are performed and steps 11 to 13 are omitted.

[0131] If the WTRU to WTRU relay (relay-1) establishes a new sidelink (e.g., PC5) connection with the source WTRU (UE-1), steps 9 and 10 may be omitted and steps 11 to 13 may be performed.

[0132] In step 9, the WTRU-to-WTRU relay (relay-1) may respond to the DCR message from the source WTRU (UE-1) by sending a link change request message to the source WTRU (UE-1). The link change request may be sent over the existing sidelink (e.g., PC5) connection between the source WTRU (UE-1) and the WTRU-to-WTRU relay (relay-1).

[0133] When sending a link modification request message in response to the DCR message from the source WTRU (UE-1), the link modification request message may include user information of the source WTRU (UE-1), user information of the target WTRU (UE-2), and user information of the WTRU to WTRU relay (relay-1).

[0134] The link modification request message may include the requested ProSe service and QoS information related to the ProSe service of the link between the WTRU to WTRU relay (relay-1) and the source WTRU (UE-1), derived based on the end-to-end QoS information received in step 1.

[0135] The Link Change Request message may include the same message transaction number value as received in step 1 from the source WTRU (UE-1).

[0136] In step 10, when the source WTRU (UE-1) receives the link change request, if the link change request message contains the user information of the source WTRU (UE-1) and the user information of the target WTRU (UE-2) as contained in the DCR message sent in step 1, or if the link change request message contains the same message transaction number value in the DCR sent in step 1, the source WTRU (UE-1) considers the DCR message to be responded to by a link change request message, and the source WTRU (UE-1) may respond by a link change response message.

[0137] In step 11, if necessary, security establishment may occur between the source WTRU (UE-1) and the WTRU to WTRU relay (relay-1).

[0138] In step 12, the WTRU to WTRU relay (relay-1) may respond to the source WTRU (UE-1) by sending a DCA message to the source WTRU (UE-1).

[0139] The DCA message may include user information of the source WTRU (UE-1), user information of the target WTRU (UE-2), and user information of the WTRU to WTRU relay (relay-1). The DCA message may include the requested ProSe service and QoS information related to the ProSe service of the link between the WTRU to WTRU relay (relay-1) and the source WTRU (UE-1), which may be derived based on the end-to-end QoS information received in step 1.

[0140] The DCA message may include the same message transaction number value as received in step 1 from the source WTRU (UE-1).

[0141] In step 13, for IP traffic, an IPv6 prefix or an IPv4 address is assigned to the source (e.g., 5G ProSe Layer 3) WTRU (UE-1).

[0142] In another embodiment, a method for performing integrated discovery when there is an existing sidelink (e.g., PC5) connection between a source WTRU and a WTRU-to-WTRU relay, and / or between a WTRU-to-WTRU and a target WTRU, may be characterized by the following functionality: (1) after receiving a DCR message from the source WTRU, the WTRU-to-WTRU relay UE may verify whether a sidelink (e.g., PC5) connection with the target WTRU already exists based on the target WTRU information. If there is no existing sidelink (e.g., PC5) connection between the WTRU-to-WTRU relay and the target WTRU, the WTRU-to-WTRU relay may send a DCR message including the requested ProSe service and the target WTRU information. If the WTRU-to-WTRU relay finds an available sidelink (e.g., PC5) connection with the target WTRU, the WTRU-to-WTRU relay may send a link change request to provide a connection between the source WTRU and the target WTRU for the ProSe service as requested in the DCR message from the source WTRU by sidelink (e.g., PC5 link) sharing between the WTRU-to-WTRU relay and the target WTRU. (2) The target WTRU may compare the received DCR message with the link change request message from the WTRU-to-WTRU relay and select a WTRU-to-WTRU relay for a connection with the source WTRU for the requested ProSe service. (3) If the WTRU-to-WTRU relay that sends the link change request message to the target WTRU is not selected for the connection between the target WTRU and the source WTRU, the target WTRU may send a link change reject message notifying that the WTRU-to-WTRU relay has not been selected.(4) After selecting a WTRU-to-WTRU relay for the connection between the source WTRU and the target WTRU, the target WTRU may respond to the selected WTRU-to-WTRU relay with a response message corresponding to the request message from the WTRU-to-WTRU relay. For example, the target WTRU may send a link modification accept (LMA) message in response to the link modification request and a DCA message in response to the DCR message.

[0143] In an embodiment, when the target WTRU receives a DCR and Link Change Request message from a WTRU-to-WTRU relay, the target WTRU may check the requested ProSe service, source WTRU information, and target WTRU information in the received DCR and Link Change Request message to determine whether the messages originate from the same source WTRU for the same ProSe service with the target WTRU. Based on this determination, the target WTRU may select the WTRU-to-WTRU relay that appears most suitable for connecting with the source WTRU.

[0144] Alternatively, the source WTRU may include a "request ID" in the DCR message, and the WTRU to WTRU may include this request ID in the DCR and link change request message sent towards the target WTRU. The target WTRU may check the DCR and link change requests with the same request ID to evaluate whether they result from the same request from the same source WTRU.

[0145] FIG. 4 is an example message sequence chart of an integrated discovery link procedure between a WTRU (eg, an end UE) and a WTRU to WTRU relay with a link change reject / accept procedure.

[0146] In step 0, the source WTRU (e.g., UE-1) and the target WTRU (e.g., UE-2) may be authorized and provisioned with parameters to use the services provided by the WTRU-to-WTRU relays (e.g., Relay-1 and Relay-2). The WTRU-to-WTRU relays may be authorized and provisioned with parameters to provide the services of relaying traffic between the source WTRU and the target WTRU.

[0147] In step 1, the source WTRU (eg, UE-1) may request the establishment of unicast communication with the target WTRU (eg, UE-2), and may therefore broadcast a DCR message.

[0148] The source WTRU (eg, UE-1) may include a Request ID value in the DCR message.

[0149] The DCR may include a sidelink (e.g., PC5 link) sharing policy (e.g., link sharing PREFERRED, REQUIRED, NOT NEEDED). Link sharing policies may be applied and may be provisioned at the WTRU / WTRU-to-WTRU relay on a per-ProSe or RSC basis. For example, a particular ProSe service or RSC may require the use of a dedicated connection (e.g., not allow link sharing) across the WTRU-to-WTRU relay to enforce security / traffic isolation.

[0150] In step 2, upon receiving the DCR from the source WTRU (e.g., UE-1), the WTRU-to-WTRU relays (e.g., Relay-1 and Relay-2) may decide to participate in the procedure. As a default behavior, the WTRU-to-WTRU relays may broadcast a direct communication request message in their vicinity.

[0151] If there is an existing sidelink (e.g., PC5) connection between the WTRU-to-WTRU relay (e.g., Relay-2) and the target WTRU (e.g., UE-2), instead of broadcasting a DCR message, the WTRU-to-WTRU relay (e.g., Relay-2) may send a Link Change Request message over the existing sidelink (e.g., PC5) connection. If an existing sidelink (e.g., PC5) exists with the target WTRU (e.g., UE-2), the WTRU-to-WTRU relay (e.g., Relay-2) may decide whether to request a new link with a DCR message or reuse the existing link with a Link Change Request according to the link sharing policy, as described above.

[0152] The DCR message may include source WTRU (e.g., UE-1) user information, target WTRU (e.g., UE-2) user information, and WTRU to WTRU relay (e.g., Relay-2) information in the message. The message may include the requested ProSe service as received in step 1.

[0153] If a link modification request message is sent in step 2, the link modification request message may include the user information of the source WTRU (e.g., UE-1), the target WTRU (e.g., UE-2) user information and the WTRU to WTRU relay (e.g., relay-2) information in the message, and the requested ProSe service as received in step 1.

[0154] If the received DCR message does not include the target WTRU user information, the WTRU to WTRU relay (eg, Relay-2) may not include the target WTRU user information in the DCR in step 2.

[0155] The WTRU to WTRU relay (eg, Relay-2) may include the value of the Request ID in the DCR message and in the Link Change Request message as received in the DCR message from the source WTRU.

[0156] In step 3, when the target WTRU (e.g., UE-2) receives the DCR message and the Link Change Request message from one or more WTRU-to-WTRU relays for connection setup with the source WTRU (e.g., UE-1) via the WTRU-to-WTRU relay, the target WTRU (e.g., UE-2) may verify that the received DCR message and the Link Change Request message originate from the same source WTRU for the same requested ProSe service. For example, this may be verified by comparing included parameters such as source WTRU user information, application ID, and requested ProSe service. Additionally or alternatively, this may be verified by comparing included request IDs.

[0157] From among the WTRU-to-WTRU relays that have sent DCR or link change requests to the same source WTRU (e.g., UE-1), the target WTRU (e.g., UE-2) may select a WTRU-to-WTRU relay to which the target WTRU will respond. The target WTRU may select a WTRU-to-WTRU relay according to signal strength, local policy, and per-RSC operator policy, if any. For example, to avoid the overhead of setting up and maintaining an additional sidelink (e.g., PC5 link) (e.g., with Relay-1), the target WTRU (e.g., UE-2) may prioritize WTRU-to-WTRU relays by privileging relays (e.g., Relay-2) that have sidelink (e.g., PC5 link) sharing opportunities according to a sidelink (e.g., PC5 link) sharing policy.

[0158] If the received DCR message does not include user information of the target WTRU, the target WTRU (eg, UE-2) may decide to respond to the DCR message if it supports the requested ProSe service.

[0159] In step 4, in option (option A), if the WTRU-to-WTRU relay sent a Link Change Request message for connection setup with the source WTRU, but the WTRU-to-WTRU relay is not selected for the connection with the source WTRU, the target WTRU may send a Link Change Reject to the WTRU-to-WTRU relay, which may indicate that the WTRU-to-WTRU relay is not selected for the connection between the source WTRU (e.g., UE1) and the target WTRU (e.g., UE2). If a Link Change Reject is received, the WTRU-to-WTRU relay considers the request of step 2 to be rejected and no longer needs to be requested or retransmitted. The Link Change Reject message may include an indication / cause code indicating that the WTRU-to-WTRU relay is not selected by the target WTRU for the particular connection request just mentioned. The Link Change Reject message may alternatively indicate that link sharing is not allowed based on the target WTRU link sharing policy. In the latter case, the WTRU-to-WTRU relay may retransmit the DCR in response to instead initiate a new link setup.

[0160] The link change reject message may include source WTRU (e.g., UE-1) user information, target WTRU (e.g., UE-2) user information, WTRU to WTRU relay information, requested ProSe service, and may include the same Request ID value as received in step 2 from the WTRU to WTRU relay (e.g., Relay-2).

[0161] In step 5, in an option (option B), if the WTRU-to-WTRU relay sends a Link Change Request message for connection setup with the source WTRU (e.g., UE-1), and the WTRU-to-WTRU relay is selected for the connection with the source WTRU, the target WTRU (e.g., UE-2) may send a Link Change Accept to the WTRU-to-WTRU relay, and does not proceed to steps 6, 7, and 8 because the WTRU-to-WTRU relay (e.g., Relay-1) is not selected for the connection between the source WTRU and the target WTRU.

[0162] The link change accept message may include source WTRU (eg, UE-1) user information, target WTRU (eg, UE-2) user information, WTRU to WTRU relay information, requested ProSe service, and a request ID.

[0163] If the target WTRU selects a WTRU-to-WTRU relay (e.g., Relay-1) that sent a DCR for connection with the source WTRU, and there is no existing sidelink (e.g., PC5) connection between the target WTRU and the WTRU-to-WTRU relay selected for connection with the source WTRU, the target WTRU may perform steps 6, 7, and 8.

[0164] In step 6, in an option (Option C), the target WTRU (e.g., UE2) may, if necessary, trigger security establishment between the target WTRU (e.g., UE-2) and the selected (e.g., 5G ProSe) WTRU to WTRU relay (e.g., Relay-1).

[0165] In step 7, the target WTRU may return a DCA message to the selected WTRU-to-WTRU relay (eg, Relay-1).

[0166] The DCA message may include source WTRU user information, target WTRU user information, and selected WTRU to WTRU relay (eg, relay-1) information and the requested ProSe service in the message.

[0167] The message may include the same Request ID value as received in step 2 from the selected WTRU to WTRU relay.

[0168] In step 8, for IP traffic, an IPv6 prefix or an IPv4 address may be assigned to the target (eg, 5G ProSe Layer 3) WTRU.

[0169] Once the direct communication request sent in step 2 is successfully responded to, the WTRU to WTRU relay may respond to the direct communication request message sent from the source WTRU in step 1.

[0170] Steps 9 to 13 may be performed when the selected WTRU-to-WTRU relay (e.g., Relay-1) receives a response from the target WTRU accepting the DCR or link change request for connection with the source WTRU. If the other WTRU-to-WTRU relay (e.g., Relay-2) receives a response from the target WTRU accepting the request, steps 9 to 13 may be performed between the source WTRU (e.g., UE-1) and the other WTRU-to-WTRU relay (e.g., Relay-2).

[0171] In an option (Option D), if the other WTRU to WTRU relay needs to set up a new sidelink (e.g., PC5) connection with the source WTRU (e.g., UE-1), steps 9, 10, and 11 may be performed, and steps 12 and 13 may be omitted.

[0172] In an option (Option E), if there is an existing sidelink (e.g., PC5) connection between the source WTRU (e.g., UE-1) and the WTRU to WTRU relay (relay-1), steps 12 and 13 are performed and steps 9, 10, and 11 are omitted.

[0173] In step 9, security establishment may occur between the source WTRU (eg, UE-1) and the WTRU to WTRU relay (eg, Relay-1) according to option D, if necessary.

[0174] In step 10, the WTRU-to-WTRU relay (eg, Relay-1) may respond with a DCA message to the source WTRU (eg, UE-1).

[0175] The DCA message may include user information of the source WTRU, user information of the target WTRU, and user information of the WTRU-to-WTRU relay (eg, Relay-1). The message may include the requested ProSe service.

[0176] The message may include the same Request ID value as received in step 1 from the source WTRU.

[0177] In step 11, for IP traffic, an IPv6 prefix or an IPv4 address may be assigned to the source (e.g., 5G ProSe Layer 3) WTRU.

[0178] In step 12, in an option (Option E), if there is an existing sidelink (e.g., PC5) connection between the WTRU-to-WTRU relay (e.g., Relay-1) and the source WTRU, the WTRU-to-WTRU relay (e.g., Relay-1) may send a direct communication reject message with a reject cause (e.g., "use existing link"). The reject cause may indicate that a new sidelink (e.g., PC5) connection between the source WTRU and the WTRU-to-WTRU relay (e.g., Relay-1) is not to be established for the connection with the target WTRU, and that an existing sidelink (e.g., PC5) connection between the source WTRU and the WTRU-to-WTRU relay (e.g., Relay-1) may (e.g., already) exist and should be reused. The direct communication reject message may include an indication / cause code indicating that the existing link is available for link sharing.

[0179] The message may include the same Request ID value as received in step 1 from the source WTRU.

[0180] In step 13, after receiving the Direct Communication Reject message with the cause "Use Existing Link", the source WTRU (UE-1) may trigger a link change procedure between the source WTRU and the WTRU-to-WTRU relay (e.g., Relay-1) to update the existing sidelink (e.g., PC5) connection to add ProSe service for the connection with the target WTRU (e.g., UE-2).

[0181] Alternatively, the link change procedure may be triggered by the WTRU to WTRU relay (e.g., Relay-1) upon receiving a DCA (or upon receiving an LMA if Relay-2 is selected), in which case step 12 may be omitted.

[0182] In another embodiment, when there is an existing sidelink (e.g., PC5) connection between the source WTRU and the WTRU-to-WTRU relay, and / or between the WTRU-to-WTRU relay and the target WTRU, the method for performing integrated discovery may be characterized by the following functionality: (1) after receiving a DCR message from the source WTRU, the WTRU-to-WTRU relay may send a DCR message including the requested ProSe service and potential target WTRU information; (2) the target WTRU may compare messages received from the WTRU-to-WTRU relay and select a WTRU-to-WTRU relay for connection with the source WTRU for the requested ProSe service; and (3) when a relay WTRU is selected and there is an existing connection between the WTRU-to-WTRU relay and the target WTRU, the target WTRU may decide to reuse the existing sidelink (e.g., PC5) for connection with the source WTRU. In the just-mentioned case, the target WTRU may respond with a direct communication reject message with a reject code indicating that there is an existing connection, (4) after sending the direct communication reject message, a link change procedure is performed between the target WTRU and the WTRU-to-WTRU relay to change the existing sidelink (e.g., PC5) for the connection with the source WTRU, (5) the WTRU-to-WTRU relay responds to the source WTRU based on the response from the target WTRU, and if the WTRU-to-WTRU relay finds an existing sidelink (e.g., PC5) connection between the source WTRU and the WTRU-to-WTRU relay, the WTRU-to-WTRU relay may respond with a direct communication reject message with a reject code indicating that there is an existing connection. After sending the direct communication reject, a link change procedure is performed between the source WTRU and the WTRU-to-WTRU relay to change the existing sidelink (e.g., PC5) for the connection with the target WTRU.

[0183] In an embodiment, when a target WTRU receives a direct communication request message from a WTRU-to-WTRU relay, the target WTRU may check the requested ProSe service, the source WTRU user information in the received direct communication request message, and the target WTRU user information (if provided) to determine whether the messages originate from the same source WTRU for the same ProSe service. Based on the determination, the target WTRU may select the WTRU-to-WTRU relay that appears most suitable for connecting with the source WTRU.

[0184] Alternatively, or in addition, the request ID may be included in the direct communication request message in the same manner as the direct communication request message received from the source WTRU. The target WTRU may check direct communication request messages with the same request ID to evaluate whether they result from the same request from the same source WTRU.

[0185] FIG. 5 is an example message sequence chart of an integrated discovery procedure between a WTRU to WTRU relay and a WTRU with direct communication reject.

[0186] In step 0, the source WTRU (e.g., UE-1) and the target WTRU (e.g., UE-2) may be authorized and provisioned with parameters to use the service provided by the WTRU-to-WTRU relay. The WTRU-to-WTRU relay may be authorized and provisioned with parameters to provide a service to relay traffic between the source WTRU (e.g., UE-1) and the target WTRU (e.g., UE-2). The source WTRU (e.g., UE-1), target WTRU (e.g., UE-2), and WTRU-to-WTRU relay may be provisioned by a ProSe key management function (PKMF) with security parameters (e.g., confidentiality keys) associated with the RSC.

[0187] In step 1, a source WTRU (e.g., UE-1) may broadcast a direct communication request, requesting the establishment of unicast communication for a specific application ID and / or ProSe service. The direct communication request may include the source WTRU's (e.g., UE-1) user information, application ID, and relay service code, if any, and may include the requested ProSe service and target WTRU (UE-2) user information.

[0188] The source WTRU (e.g., UE-1) may include a Request ID value in the direct communication request message. The source WTRU (e.g., UE-1) may protect the parameters (e.g., Request ID, Requested ProSe Service) for confidentiality and from replay using security parameters (e.g., using a time-based counter).

[0189] In step 2, upon receiving a direct communication request message from a source WTRU (e.g., UE-1), the WTRU-to-WTRU relays (e.g., Relay-1 and Relay-2) may decide to participate in the procedure. As a default behavior, the WTRU-to-WTRU relays may broadcast the direct communication request message in their vicinity.

[0190] The direct communication request message may include user information of the source WTRU (e.g., UE-1), user information of the target WTRU (e.g., UE-2) (if received from the source WTRU), and WTRU-to-WTRU relay information. The message may include the requested ProSe service as received in step 1.

[0191] If the received direct communication request message does not include target WTRU user information, the WTRU to WTRU relay information does not include target WTRU user information in the direct communication request in step 2 .

[0192] The WTRU to WTRU relay may include information indicating the value of the Request ID in the direct communication request message as received in step 1. The WTRU to WTRU relay may protect the parameters in the direct communication request message (e.g., Request ID, requested ProSe service) for confidentiality and from replay using security parameters.

[0193] In step 3, when the target WTRU (e.g., UE-2) receives a direct communication request message from one or more WTRU-to-WTRU relays for connection setup with the source WTRU (e.g., UE-1) via the WTRU-to-WTRU relay, the target WTRU (e.g., UE-2) may verify whether the received direct communication request message originates from the same source WTRU for the same requested ProSe service. For example, verification may be performed by comparing included parameters such as source WTRU user information, application ID, and requested ProSe service. Additionally or alternatively, verification may be performed by comparing included request IDs.

[0194] From among the WTRU-to-WTRU relays that have sent direct communication request messages to the same source WTRU, the target WTRU may select a WTRU-to-WTRU relay to which the target WTRU (e.g., UE-2) will respond. The target WTRU (e.g., UE-2) may select a WTRU-to-WTRU relay according to signal strength, local policy, and operator policy per relay service code, if any.

[0195] In step 4, if an existing sidelink (e.g., PC5) connection exists between the target WTRU (e.g., UE-2) and the selected WTRU-to-WTRU relay (e.g., Relay-2), the target WTRU may send a direct communication reject with reject cause “use existing link”, indicating, for example, that a new sidelink (e.g., PC5) connection between the target WTRU and the selected WTRU-to-WTRU relay may not be established due to the connection with the source WTRU, and that the existing sidelink (e.g., PC5) connection between the target WTRU and the selected WTRU-to-WTRU relay should be reused.

[0196] The message may include the same Request ID value received in step 2. The target WTRU may protect the parameters (e.g., Request ID) in the Direct Communication Reject message for confidentiality and from replay using security parameters.

[0197] In step 5, a link change procedure may occur between the source WTRU and the selected WTRU-to-WTRU relay (e.g., relay-2) to update the existing sidelink (e.g., PC5) connection to add ProSe services for the connection with the source WTRU. The link change procedure may be triggered by the target WTRU or by the selected WTRU-to-WTRU relay (e.g., relay-2). The WTRU-to-WTRU relay (e.g., relay-2) may verify the security of the direct communication reject message parameters and verify that they match the parameters of the direct communication request message. The WTRU-to-WTRU relay may proceed with the link change procedure if the communication reject message verification is successful; otherwise, the WTRU-to-WTRU relay may ignore the direct communication reject message.

[0198] In option A, if the selected WTRU-to-WTRU relay (e.g., Relay-2) needs to set up a new sidelink (e.g., PC5) connection with the source WTRU (e.g., UE-1), steps 6, 7, and 8 may be performed, and steps 9 and 10 may be omitted.

[0199] In option B, if there is an existing sidelink (e.g., PC5) connection between the source WTRU and the selected WTRU to WTRU relay (e.g., Relay-2), steps 9 and 10 may be performed and steps 6, 7, and 8 may be omitted.

[0200] In step 6, security establishment occurs between the source WTRU (eg, UE-1) and the selected WTRU to WTRU relay (eg, Relay-2), if necessary.

[0201] In step 7, the selected WTRU-to-WTRU relay (eg, Relay-2) may respond with a direct communication accept message to the source WTRU (eg, UE-1).

[0202] The direct communication accept message may include user information of the source WTRU, user information of the target WTRU, and user information of the selected WTRU-to-WTRU relay (e.g., Relay-2). The message may include the requested ProSe service.

[0203] The message may include the same Request ID value as received in step 1 from the source WTRU.

[0204] In step 8, for IP traffic, an IPv6 prefix or an IPv4 address may be assigned to the source (eg, 5G ProSe Layer 3) WTRU.

[0205] In step 9, if there is an existing sidelink (e.g., PC5) connection between the selected WTRU to WTRU relay (e.g., Relay-2) and the source WTRU, the selected WTRU to WTRU relay (e.g., Relay-2) may send a direct communication reject indicating that a new sidelink (e.g., PC5) connection between the source WTRU and the selected WTRU to WTRU relay (e.g., Relay-2) is not established for the connection with the target WTRU, and that the existing sidelink (e.g., PC5) connection between the source WTRU and the selected WTRU to WTRU relay (e.g., Relay-2) should be reused.

[0206] The message may include the same Request ID value as received from the source WTRU in step 1. The WTRU to WTRU relay may protect parameters (e.g., Request ID) in the Direct Communication Reject message for confidentiality and from replay using security parameters.

[0207] In step 10, after sending the direct communication reject message to the source WTRU, a link change procedure may be performed between the source WTRU and the selected WTRU-to-WTRU relay (e.g., relay-2) to update the (e.g., existing) sidelink (e.g., PC5) connection to add ProSe services for the connection with the target WTRU. The link change procedure may be triggered by the source WTRU or the selected WTRU-to-WTRU relay (e.g., relay-2). The selected WTRU-to-WTRU relay (e.g., relay-2) may trigger the link change procedure without sending a direct communication reject message to the source WTRU. The source WTRU may verify the security of the direct communication reject message parameters and verify that they match the parameters in the direct communication request message. The source WTRU may proceed with the link change procedure if the verification of the communication reject message is successful; otherwise, the source WTRU may ignore the direct communication reject message.

[0208] In an embodiment, a method implemented in a first wireless transmit / receive unit, WTRU, or a second WTRU, for performing integrated discovery when there is an existing sidelink connection between the first WTRU or the second WTRU and at least one WTRU-to-WTRU relay may include transmitting a direct communication request, DCR, message to the second WTRU via the at least one WTRU-to-WTRU relay, the direct communication request, DCR, message including proximity-based service, ProSe, parameters. The method may further include receiving a link change request message from the second WTRU via one of the at least one WTRU-to-WTRU relay, the link change request message including information related to the ProSe service parameters. The method may further include transmitting a link change response message to one of the at least one WTRU-to-WTRU relay.

[0209] The method may further include receiving a direct communication accept (DCA) message from one of the at least one WTRU-to-WTRU relays.

[0210] The DCR message may include any of a relay_indication, first WTRU user information, second WTRU user information, an application ID, and a relay service code. The first WTRU may include a ProSe service and QoS information related to the ProSe service. The method may further include determining that the received information relates to proximity-based service parameters. The DCR message may include a value of a message transaction number, and the link change request message includes the value of the message transaction number. The DCR message may include information including quality of service (QoS) information related to the proximity-based service, such that the method includes receiving QoS requirements from the WTRU-to-WTRU relay for the link between the WTRU-to-WTRU relay and the first WTRU. The DCR message may be transmitted in a broadcast manner. The link change request message may be transmitted in a unicast manner. The link change response message may be transmitted in a unicast manner.

[0211] In one embodiment, a method implemented in a WTRU-to-WTRU relay may include receiving, from a first WTRU, a direct communication request (DCR) message including information including quality of service (QoS) information related to proximity-based services. The method may further include determining a first value of a QoS parameter for a link between the first WTRU and the WTRU-to-WTRU relay. The method may include transmitting the DCR message to a second WTRU. The method may include receiving, from the second WTRU, a second value of the QoS parameter for the link between the second WTRU and the WTRU-to-WTRU relay, and determining whether direct communication between the first WTRU and the second WTRU is accepted based on the first value of the QoS parameter and the second value of the QoS parameter. The method may further include transmitting the first value of the QoS parameter for the link between the first WTRU and the WTRU-to-WTRU relay to the first WTRU.

[0212] 6, a method 600 implemented in a wireless transmit / receive unit (WTRU) performing integrated discovery may include receiving 610 a direct communication request message from each WTRU-to-WTRU relay of a first set of WTRU-to-WTRU relays, the direct communication request message including a first communication request from a first source WTRU. The method 600 may include receiving 620 a link change request message from each WTRU-to-WTRU relay of a second set of WTRU-to-WTRU relays, the link change request message including a second communication request from the first source WTRU. The method 600 may include selecting 630 a WTRU-to-WTRU relay from among the first and second sets of WTRU-to-WTRU relays for communication with the first source WTRU, and transmitting 640 a link change reject message to all WTRU-to-WTRU relays of the second set of WTRU-to-WTRU relays that are not selected for communication with the source WTRU.

[0213] Under a condition that the selected WTRU-to-WTRU relay is from a first set of WTRU-to-WTRU relays and an existing sidelink connection between the WTRU and the selected WTRU-to-WTRU relay is already established, method 600 may include sending a direct communication reject message to the selected WTRU-to-WTRU relay. Method 600 may include performing a link change procedure by the selected WTRU-to-WTRU relay to modify the existing sidelink connection. Selecting the WTRU-to-WTRU relay may include selecting from among the first and second sets of WTRU-to-WTRU relays a third set of WTRU-to-WTRU relays to send a direct communication request message or a link change request message originating from the same source WTRU for the same ProSe service as the WTRU, and selecting the WTRU-to-WTRU relay from the third set of WTRU-to-WTRU relays based on any of signal strength, local policy, and operator policy per relay service code. Under a condition that the selected WTRU-to-WTRU relay is from the first set of WTRU-to-WTRU relays, method 600 may include sending a direct communication accept message to the selected WTRU-to-WTRU relay and sending other link change reject messages to all WTRU-to-WTRU relays in the second set of WTRU-to-WTRU relays. The direct communication request message and the link change request message may include information indicative of any of proximity-based services, information about the source WTRU information, and information about the WTRU. The direct communication accept message may be sent in a unicast manner. The link change request message may be sent in a unicast manner. The link change reject message and other link change reject messages may be sent in a unicast manner.

[0214] Although features and elements are provided above in particular combinations, those skilled in the art will understand that each feature or element can be used alone or in any combination with other features and elements. The present disclosure should not be limited to the specific embodiments described in this application, but rather as illustrations of various aspects. Many modifications and variations may be made without departing from its spirit and scope, as will be apparent to those skilled in the art. No element, act, or instruction used in the description of this application should be construed as critical or essential to the invention unless explicitly provided as above. Functionally equivalent methods and apparatuses within the scope of the present disclosure, in addition to those recited herein, will be apparent to those skilled in the art from the foregoing description. Such modifications and variations are intended to fall within the scope of the appended claims. The present disclosure should be limited only by the appended claims, along with the full scope of equivalents to which such claims are entitled. It should be understood that the present disclosure is not limited to any particular method or system.

[0215] The foregoing embodiments are described, for simplicity, with respect to the terminology and structure of infrared capable devices, i.e., infrared emitters and receivers. However, the described embodiments are not limited to the systems just described and may be applied to other systems that use electromagnetic waves or other forms of non-electromagnetic waves, such as acoustic waves.

[0216] Furthermore, it should be understood that the terms used herein are for the purpose of describing particular embodiments and are not intended to be limiting. As used herein, the term "video" or "image" can mean either a snapshot, a single image, and / or multiple images displayed on a time basis. As another example, when referred to herein, the term "user equipment" and abbreviation "UE," the term "remote," and / or the term "head-mounted display" or abbreviation "HMD" can mean or include (i) a wireless transmit and / or receive unit (WTRU), (ii) any of numerous embodiments of a WTRU, (iii) a wireless and / or wired device (e.g., that may be tethered) configured with, among other things, some or all of the structure and functionality of a WTRU, (iii) a wireless and / or wired device configured with less than all of the structure and functionality of a WTRU, or (iv) the like. Details of an example WTRU, which may represent any WTRU described herein, are provided with respect to FIGS. 1A-1D . As another example, various disclosed embodiments hereinbefore and hereinafter are described as utilizing a head-mounted display. Those skilled in the art will recognize that devices other than a head-mounted display may be utilized, and that some or all of the present disclosure and various disclosed embodiments may be modified accordingly without undue experimentation. Examples of such other devices may include drones or other devices configured to stream information to provide an adapted reality experience.

[0217] Additionally, the methods provided herein may be implemented in a computer program, software, or firmware embodied in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electrical signals (transmitted over wired or wireless connections) and computer-readable recording media. Examples of computer-readable recording media include, but are not limited to, ROM (described), RAM (random access memory), registers, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, and optical media such as magneto-optical media, e.g., CD-ROM disks and digital versatile disks (DVDs). A processor associated with software may be used to implement a radio frequency transceiver for use in a UE, WTRU, terminal, base station, RNC, or any host computer.

[0218] Modifications of the methods, apparatus, and systems provided above are possible without departing from the scope of the present invention. In view of the wide variety of embodiments that may be applied, it should be understood that the illustrated embodiments are merely examples and should not be taken as limiting the scope of the following claims. For example, the embodiments provided herein include handheld devices that include or may be utilized with any suitable voltage source, such as, for example, a battery and the like, that provides any suitable voltage.

[0219] Furthermore, in the embodiments provided above, mention is made of processing platforms, computing systems, controllers, and other devices that include processors. The devices mentioned may include at least one CPU (Central Processing Unit) and memory. In accordance with the practices of those skilled in the art of computer programming, references to operations and symbolic representations of operations or instructions may be performed by various CPUs and memories. Such operations and operations or instructions may be referred to as being "executed," "computer-executed," or "CPU-executed."

[0220] Those skilled in the art will understand that the operations and symbolically represented operations or instructions include the manipulation of electrical signals by a CPU. The electrical system reconfigures or otherwise alters the operation of the CPU, as well as the processing of other signals, by representing data bits that can cause the resulting transformation or reduction of the electrical signals and the retention of the data bits in memory locations in a memory system. The memory locations where the data bits are maintained are physical locations that have particular electrical, magnetic, optical, or organic properties that correspond to or represent the data bits. It should be understood that embodiments are not limited to the platforms or CPUs described above, and that other platforms and CPUs may support the provided methods.

[0221] Additionally, data bits may be maintained on computer-readable media including magnetic disks, optical disks, and any other volatile (e.g., Random Access Memory (RAM)) or non-volatile (e.g., Read-Only Memory (ROM)) mass storage system that is readable by a CPU. Computer-readable media may include computer-readable media that reside exclusively in a processing system or that are distributed among, cooperating with, or interconnected to multiple interconnected processing systems that may be local or remote to a processing system. It should be understood that embodiments are not limited to the memories described above, and that other platforms and memories may support the provided methods.

[0222] In an example embodiment, any of the operations, processes, etc. described herein may be implemented as computer-readable instructions stored on a computer-readable medium. The computer-readable instructions may be executed by a processor in a mobile unit, a network element, and / or any other computing device.

[0223] Few distinctions remain between hardware and software implementations of system aspects. The use of hardware or software is generally (though not always, in that the choice between hardware and software can be important in some situations) a design choice representing a cost vs. efficiency trade-off. There may be various means (e.g., hardware, software, and / or firmware) by which the processes and / or systems and / or other techniques described herein may be achieved, and the preferred means may vary depending on the context in which the processes and / or systems and / or other techniques are deployed. For example, if an implementer determines that speed and accuracy are most important, the implementer may opt for a primarily hardware and / or firmware implementation. If flexibility is most important, the implementer may opt for a primarily software implementation. Alternatively, the implementer may opt for a combination of hardware, software, and / or firmware.

[0224] The foregoing detailed description has set forth various embodiments of devices and / or processes through the use of block diagrams, flowcharts, and / or examples. To the extent that the block diagrams, flowcharts, and / or examples, as described above, include one or more functions and / or operations, those skilled in the art will understand that each function and / or operation within the block diagrams, flowcharts, or examples, individually and / or collectively, may be implemented by a wide range of hardware, software, firmware, or substantially any combination thereof. In embodiments, some portions of the subject matter described herein may be implemented via Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), Digital Signal Processors (DSPs), and / or other integrated formats. However, those skilled in the art will recognize that some aspects of the embodiments disclosed herein may equivalently be implemented, in whole or in part, in integrated circuits, as one or more computer programs executing on one or more computers (e.g., as one or more programs executing on one or more computer systems), as one or more programs executing on one or more processors (e.g., as one or more programs executing on one or more microprocessors), as firmware, or as substantially any combination thereof, and that designing circuitry and / or writing software and / or firmware code is well within the skill of those skilled in the art in light of this disclosure. Additionally, those skilled in the art will understand that the subject mechanisms described herein may be distributed as a program product in various forms, and that exemplary embodiments of the subject matter described herein apply regardless of the particular type of signal-bearing medium used to actually effect the distribution.Examples of signal-bearing media include, but are not limited to, the following: recordable-type media such as, for example, floppy disks, hard disk drives, CDs, DVDs, digital tape, computer memory, and transmission-type media such as, for example, digital and / or analog communications media (e.g., fiber optic cables, wave guides, wired communications links, etc.).

[0225] Those skilled in the art will recognize that it is common in the art to describe devices and / or processes in the manner described herein and then use engineering techniques to integrate the described devices and / or processes into a data processing system. That is, at least a portion of the devices and / or processes described herein may be integrated into a data processing system through a reasonable amount of experimentation. Those skilled in the art will recognize that a typical data processing system may generally include one or more of the following: a system unit housing; a video display device; memory, such as volatile and non-volatile memory; a processor, such as a microprocessor and a digital signal processor; computational entities, such as an operating system, drivers, a graphical user interface, and application programs; one or more interaction devices, such as a touchpad or screen; and / or a control system including feedback loops and control motors (e.g., feedback for sensing position and / or velocity, control motors for moving and / or adjusting components and / or quantities). A typical data processing system may be implemented utilizing any suitable commercially available components, such as those typically found in data computing / communication systems and / or network computing / communication systems.

[0226] The subject matter described herein sometimes illustrates different components contained within or connected to different other components. It should be understood that the depicted structures above are merely examples, and that many other structures that achieve the same functionality may actually be implemented. In a conceptual sense, any arrangement of components that achieve the same functionality is effectively "associated" such that the desired functionality may be achieved. Thus, any two components that combine to achieve specific functionality herein may be understood as being "associated" with each other such that the desired functionality is achieved regardless of structure or intermediate components. Similarly, any two components so associated may also be considered to be "operably connected" or "operably coupled" to each other to achieve the desired functionality, and any two components capable of being so associated may also be considered to be "operably coupleable" to each other to achieve the desired functionality. Specific examples of operably coupleable include, but are not limited to, physically matable and / or physically interacting components, wirelessly interacting and / or wirelessly interacting components, and / or logically interacting and / or logically interacting components.

[0227] With respect to the use of substantially any plural and / or singular term herein, those skilled in the art will be able to convert from plural to singular and / or from singular to plural as appropriate to the context and / or application. Various singular / plural permutations may be expressly set forth herein for purposes of clarity.

[0228] It will be understood by those skilled in the art that terms used herein in general, and in the appended claims in particular (e.g., the body of the appended claims), are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "including" should be interpreted as "including but not limited to," etc.). It will be further understood by those skilled in the art that if a specific number of recitations in a submitted claim are intended, such intention will be explicitly set forth in the claim, and that such intention would not be given absent such recitation. For example, where only one item is intended, "single" or similar language may be used. As an aid to understanding, the following appended claims and / or description herein may include the use of the introductory phrases "at least one" and "one or more" to present claim recitations. However, use of the above phrases should not be construed as meaning that filing a claim statement with the indefinite article "a" or "an" limits any particular claim that includes the above-filed claim statement to embodiments that include only one such statement, even when the same claim includes the preface phrase "one or more" or "at least one" and an indefinite article such as "a" or "an" (e.g., "a" and / or "an" should be interpreted to mean "at least one" or "one or more"). The same holds true for the use of definite articles used to file a claim statement. Additionally, even when a specific number of statements in a filed claim is explicitly recited, those skilled in the art will recognize that the recitation should be interpreted to mean at least the recited number (e.g., the mere recitation of "two statements" without any other modifiers means at least two statements, or more than two statements).Furthermore, in instances where a convention similar to "at least one of A, B, and C, etc." is used, the above configuration is generally intended in the sense that one of ordinary skill in the art would understand the convention (e.g., "a system having at least one of A, B, and C" includes, but is not limited to, systems having A only, B only, C only, A and B together, A and C together, B and C together, and / or A, B, and C together, etc.). In instances where a convention similar to "at least one of A, B, or C, etc." is used, the above configuration is generally intended in the sense that one of ordinary skill in the art would understand the convention (e.g., "a system having at least one of A, B, or C" includes, but is not limited to, systems having A only, B only, C only, A and B together, A and C together, B and C together, and / or A, B, and C together, etc.). It will be further understood by those skilled in the art that any disjunctive word and / or phrase providing two or more alternative terms, whether in the specification, claims, or drawings, should be understood to contemplate the possibility of including one of the terms, either term, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B." Furthermore, as used herein, the term "any of" followed by a description of a plurality of items and / or a plurality of groups of items is intended to include "any of," "any combination of," "any more of," and / or "combination of any more of" the items and / or groups of items, either individually or in conjunction with other items and / or other groups of items. Furthermore, as used herein, the term "set" is intended to include any number of items, including zero. Additionally, as used herein, the term "number" is intended to include any number, including zero. Furthermore, as used herein, the term "multiple" is intended to be synonymous with "plurality."

[0229] Additionally, where features or aspects of the present disclosure are described in terms of a Markush group, those skilled in the art will further appreciate that the present disclosure is thereby described in terms of any individual element of an element of a Markush group or subgroup of elements of a subgroup.

[0230] As will be understood by those skilled in the art, for any and all purposes, including, for example, with respect to providing a written description, all ranges disclosed herein also include any and all possible subranges and combinations of those subranges. Any range described can be readily recognized as being fully described and that the same range can be at least equally broken down into halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each range described herein can be readily broken down into lower, middle, and upper thirds, etc. As will be further understood by those skilled in the art, all terms, such as "up to," "at least," "greater than," "less than," etc., refer to ranges that are inclusive of the recited number and can subsequently be broken down into subranges as described above. Finally, as will be understood by those skilled in the art, a range includes each individual element. Thus, for example, a group having 1 to 3 cells refers to a group having 1, 2, or 3 cells. Similarly, a group having 1 to 5 cells refers to groups having 1, 2, 3, 4, or 5 cells, and so on.

[0231] Moreover, the claims should not be read as limited to the order or elements presented unless expressly stated. Additionally, the use of the term "means for" in any claim is intended to invoke 35 U.S.C. § 112(6) or means-plus-function claim format, and any claim without the term "means for" does not have such an intention.

Claims

1. 1. A method implemented in a wireless transmit receive unit (WTRU), comprising: receiving, from each WTRU-to-WTRU relay of a first set of WTRU-to-WTRU relays, a direct communication request message including a first communication request from a first source WTRU; receiving, from each WTRU-to-WTRU relay of a second set of WTRU-to-WTRU relays, a link change request message including a second communication request from the first source WTRU; selecting a WTRU-to-WTRU relay from among the first and second sets of WTRU-to-WTRU relays for communication with the first source WTRU; sending a link change reject message to all WTRU-to-WTRU relays of the second set of WTRU-to-WTRU relays that are not selected for communication with the source WTRU; A method comprising:

2. 2. The method of claim 1, wherein the selected WTRU-to-WTRU relay is from the first set of WTRU-to-WTRU relays, and wherein the selected WTRU-to-WTRU relay sends a direct communication reject message to the selected WTRU-to-WTRU relay under the condition that an existing sidelink connection between the WTRU and the selected WTRU-to-WTRU relay is already established.

3. 3. The method of claim 2, comprising performing a link change procedure by the selected WTRU to WTRU relay to modify the existing sidelink connection.

4. The WTRU to WTRU relay selection may include: selecting, from among the first and second sets of WTRU-to-WTRU relays, a third set of WTRU-to-WTRU relays to transmit direct communication request messages or link change request messages originating from the same source WTRU for the same ProSe service by the WTRU; selecting the WTRU-to-WTRU relay from the third set of WTRU-to-WTRU relays based on one of signal strength, local policy, and operator policy per relay service code; 4. The method according to claim 1, further comprising:

5. 2. The method of claim 1, wherein the link change reject message is a first link change reject message, and the method further comprises: sending a direct communication accept message to the selected WTRU-to-WTRU relay under the condition that the selected WTRU-to-WTRU relay is from the first set of WTRU-to-WTRU relays; and sending a second link change reject message to all WTRU-to-WTRU relays in the second set of WTRU-to-WTRU relays.

6. 6. The method of claim 1, wherein the direct communication request message and the link change request message include information indicating one of proximity-based services, information about the source WTRU information, and information about the WTRU.

7. 7. The method according to claim 5 or 6, wherein the direct communication accept message is sent in a unicast manner.

8. 8. The method according to any one of claims 1 to 7, characterized in that the link change request message is sent in a unicast manner.

9. 9. The method according to any one of claims 5 to 8, wherein the second link change reject message is sent in a unicast manner.

10. 10. The method according to any one of claims 1 to 9, wherein the link change reject message is sent in a unicast manner.

11. A wireless transmit / receive unit, WTRU, comprising a processor, a transceiver unit, and a storage unit; receiving, from each WTRU-to-WTRU relay of a first set of WTRU-to-WTRU relays, a direct communication request message including a first communication request from a first source WTRU; receiving, from each WTRU-to-WTRU relay of a second set of WTRU-to-WTRU relays, a link change request message including a second communication request from the first source WTRU; selecting a WTRU-to-WTRU relay from among the first and second sets of WTRU-to-WTRU relays for communication with the first source WTRU; sending a link change reject message to all WTRU-to-WTRU relays of the second set of WTRU-to-WTRU relays that are not selected for communication with the source WTRU. WTRU configured to:

12. 12. The WTRU of claim 11, wherein the selected WTRU-to-WTRU is from the first set of WTRU-to-WTRU relays and is configured to send a communication reject message directly to the selected WTRU-to-WTRU relay under the condition that an existing sidelink connection between the WTRU and the selected WTRU-to-WTRU relay is already established.

13. 13. The WTRU of claim 12, configured to perform a link change procedure with the selected WTRU to WTRU relay to modify the existing sidelink connection.

14. 14. The WTRU of claim 11, wherein the WTRU configured to select a WTRU-to-WTRU relay is configured to select a third set of WTRU-to-WTRU relays from the first and second sets of WTRU-to-WTRU relays to transmit direct communication request messages or link change request messages originating from the same source WTRU for the same ProSe service by the WTRU, and the WTRU is configured to select the WTRU-to-WTRU relay from the third set of WTRU-to-WTRU relays based on one of signal strength, local policy, and operator policy per relay service code.

15. 12. The WTRU of claim 11, wherein the link change reject message is a first link change reject message, and the WTRU is configured to: send a direct communication accept message to the selected WTRU-to-WTRU relay, provided that the selected WTRU-to-WTRU relay is from the first set of WTRU-to-WTRU relays; and send a second link change reject message to all WTRU-to-WTRU relays in the second set of WTRU-to-WTRU relays.

16. 16. The WTRU of claim 11, wherein the direct communication request message and the link change request message include information indicating one of proximity-based services, information about the source WTRU information, and information about the WTRU.

17. 17. The WTRU of claim 15 or 16, wherein the direct communication accept message is transmitted in a unicast manner.

18. 18. The WTRU of claim 11, wherein the link change request message is transmitted in a unicast manner.

19. 19. The WTRU of claim 15, wherein the second link change reject message is transmitted in a unicast manner.

20. 20. The WTRU of claim 11, wherein the link change reject message is transmitted in a unicast manner.

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