Nr relay-method for multi-hop discovery and relay selection

Abstract

A method for use in a first wireless transmit / receive unit (WTRU) and a wireless transmit / receive unit (WTRU) are described herein. The method comprises: receiving a first transmission from a first remote WTRU; determining whether a reference signal received power (RSRP) level of the first received transmission is higher than a predetermined threshold; receiving a second transmission from a second remote WTRU; determining whether a reference signal received power (RSRP) level of the second received transmission is higher than a predetermined threshold; and transmitting a discovery message identifying the first remote WTRU and the second remote WTRU under the condition that the RSRP level of the first received transmission and the RSRP level of the second received transmission are both higher than a predetermined threshold, and receiving and transmitting data between the WTRUs identified in the discovery message.

Description

[0001] This application is a divisional application of the invention patent application with the application date of October 19, 2022, application number 202280076312.3, and invention name "NR Relay—Method for Multi-hop Discovery and Relay Selection".

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims the benefit of U.S. Provisional Application No. 63 / 257,287, filed on October 19, 2021, the contents of which are incorporated herein by reference. Background Art

[0004] In a communication system with user equipment (UE) and a network node, relays such as UE to network relay UE (U2N relay) and UE to UE relay UE (U2U relay) can enhance network coverage and reliability. In a network where relays are adopted by UE, the sending UE needs to discover and select a relay before starting its transmission to a remote UE. For a single-hop U2N relay, two possible models may be specified for discovery and relay selection or reselection. In a first model (hereinafter, Model A), the U2N relay sends a discovery notification message to a remote UE. In a second model (hereinafter, Model B), the remote UE sends a request message to request a relay service from another relay UE. The U2N relay may then respond to the request message from the remote UE. In contrast to a single-hop relay, for a multi-hop relay, a relay (e.g., a U2U relay) may be within network coverage or out of coverage. In a scenario where every UE may send discovery and become a U2U relay, allowing every UE to do so may waste resources and create congestion on the discovery resource pool. Therefore, there is a need for methods and apparatus to determine which UEs or wireless transmit / receive units (WTRUs) send discovery messages and / or what information the discovery messages should include. Summary of the invention

[0005] Methods and apparatus for multi-hop discovery and relay selection are described herein. For example, a network node may determine configuration information for sending a discovery message. The configuration information may include a Uu reference signal received power (RSRP) condition and a distance condition to a base station (BS). The Uu RSRP condition may include a Uu RSRP range for each hop to the BS and a Uu RSRP range for each quality of service (QoS) of a relay service. The distance condition to the BS may include a distance range to the BS for each number of hops to the BS and a distance range to the BS for each QoS of the relay service. The network node may then send a discovery message to one or more sub-network nodes based on the configuration information.

[0006] This document describes a method for use in a first wireless transmit / receive unit (WTRU), the method comprising: receiving a first transmission from a first remote WTRU; determining whether a reference signal received power (RSRP) level of the first received transmission is higher than a predetermined threshold; receiving a second transmission from a second remote WTRU; determining whether a reference signal received power (RSRP) level of the second received transmission is higher than a predetermined threshold; sending a discovery message identifying the first remote WTRU and the second remote WTRU, under the condition that both the RSRP level of the first received transmission and the RSRP level of the second received transmission are higher than the predetermined threshold, and receiving and sending data between the WTRUs identified in the discovery message.

[0007] This document describes a wireless transmit / receive unit (WTRU), which is configured to: receive a first transmission from a first remote WTRU; determine whether a reference signal received power (RSRP) level of the first received transmission is higher than a predetermined threshold; receive a second transmission from a second remote WTRU; determine whether a reference signal received power (RSRP) level of the second received transmission is higher than a predetermined threshold; send a discovery message identifying the first remote WTRU and the second remote WTRU under the condition that both the RSRP level of the first received transmission and the RSRP level of the second received transmission are higher than the predetermined threshold, and receive and send data between the WTRUs identified in the discovery message. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] A more detailed understanding may be obtained from the following description given by way of example in conjunction with the accompanying drawings, in which like reference numerals indicate like elements, and in which:

[0009] Figure 1A is a system diagram illustrating an exemplary communication system in which one or more disclosed embodiments may be implemented;

[0010] Figure 1B It is shown that according to one embodiment, Figure 1A A system diagram of an exemplary wireless transmit / receive unit (WTRU) for use within the communication system shown;

[0011] Figure 1C It is shown that according to one embodiment, Figure 1A A system diagram of an exemplary radio access network (RAN) and an exemplary core network (CN) used within the illustrated communication system;

[0012] Figure 1D It is shown that according to one embodiment, Figure 1A A system diagram of another exemplary RAN and another exemplary CN used within the communication system shown;

[0013] Figure 2is a diagram illustrating an exemplary system for discovery messaging by multiple configured Uus located within different received signal received power (RSRP) ranges;

[0014] Figure 3 is a diagram illustrating an exemplary user plane radio protocol stack for layer 2 evolved user equipment (UE) to network relay (PC5);

[0015] Figure 4 is a diagram illustrating an exemplary control plane radio protocol stack for Layer 2 Evolved UE to Network Relay (PC5);

[0016] Figure 5 is a diagram illustrating an exemplary UE to network relay discovery;

[0017] Figure 6 is a diagram illustrating an exemplary UE to network relay discovery;

[0018] Figure 7 is a flow chart of a process for determining whether to send a discovery message;

[0019] Figure 8 is a flow chart of another process for determining whether to send a discovery message;

[0020] Fig. 9 is a flow chart of another process for determining whether to send a discovery message; and

[0021] Fig.10 is a flow diagram of another process for determining whether to send a discovery message. DETAILED DESCRIPTION

[0022] Figure 1A 1 is a diagram illustrating an exemplary communication system 100 in which one or more disclosed embodiments may be implemented. The communication system 100 may be a multiple access system that provides content such as voice, data, video, messaging, broadcast, etc. to multiple wireless users. The communication system 100 may enable multiple wireless users to access such content through sharing of system resources (including wireless bandwidth). For example, the communication system 100 may employ one or more channel access methods such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single carrier FDMA (SC-FDMA), zero tail unique word discrete Fourier transform spread OFDM (ZT-UW-DFT-S-OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, filter bank multi-carrier (FBMC), etc.

[0023] like Figure 1AAs shown, the communication system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a radio access network (RAN) 104, a core network (CN) 106, a public switched telephone network (PSTN) 108, the Internet 110 and other networks 112, but it should be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. By way of example, the UE 102a, 102b, 102c, 102d (any of which may be referred to as a station (STA)) may be configured to send and / or receive wireless signals and may include a user equipment (WTRU), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular phone, a personal digital assistant (PDA), a smart phone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watch or other wearable device, a head-mounted display (HMD), a vehicle, a drone, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in an industrial and / or automated process chain environment), a consumer electronic device, a device operating on a commercial and / or industrial wireless network, etc. Any of the WTRUs 102a, 102b, 102c, and 102d may be interchangeably referred to as a UE.

[0024] The communication system 100 may also include a base station 114a and / or a base station 114b. Each of the base stations 114a, 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the CN 106, the Internet 110, and / or other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a Node B, an evolved Node B (eNB), a Home Node B, a Home evolved Node B, a next generation Node B such as a gNode B (gNB), a New Radio (NR) Node B, a site controller, an access point (AP), a wireless router, and the like. While the base stations 114a, 114b are each depicted as a single element, it will be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0025] The base station 114a may be part of the RAN 104, which may also include other base stations and / or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), a relay node, etc. The base station 114a and / or the base station 114b may be configured to send and / or receive wireless signals on one or more carrier frequencies, which may be referred to as a cell (not shown). These frequencies may be in a licensed spectrum, an unlicensed spectrum, or a combination of licensed and unlicensed spectrums. A cell may provide coverage of wireless services to a specific geographic area, which may be relatively fixed or may change over time. The cell may be further divided into cell sectors. For example, a cell associated with the base station 114a may be divided into three sectors. Therefore, in one embodiment, the base station 114a may include three transceivers, i.e., one transceiver for each sector of the cell. In one embodiment, the base station 114a may employ multiple-input multiple-output (MIMO) technology and may utilize multiple transceivers for each sector of the cell. For example, beamforming may be used to send and / or receive signals in a desired spatial direction.

[0026] The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d over an air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0027] More specifically, as noted above, the communication system 100 may be a multiple access system and may employ one or more channel access schemes such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, etc. For example, the base station 114a in the RAN 104 and the WTRUs 102a, 102b, 102c may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may use Wideband CDMA (WCDMA) to establish the air interface 116. WCDMA may include communication protocols such as High Speed ​​Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High Speed ​​Downlink (DL) Packet Access (HSDPA) and / or High Speed ​​Uplink (UL) Packet Access (HSUPA).

[0028] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 116 using Long Term Evolution (LTE) and / or Advanced LTE (LTE-A) and / or Advanced LTE Pro (LTE-A Pro).

[0029] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as NR radio access, which may establish the air interface 116 using NR.

[0030] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may implement LTE radio access and NR radio access together, for example using dual connectivity (DC) principles. Thus, the air interface utilized by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions sent to / from multiple types of base stations (e.g., eNBs and gNBs).

[0031] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.11 (i.e., Wireless Fidelity (WiFi)), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile Communications (GSM), GSM Enhanced Data Rates for Evolution (EDGE), GSM EDGE (GERAN), etc.

[0032] Figure 1AThe base station 114b in the may be, for example, a wireless router, a Home NodeB, a Home eNodeB, or an access point, and may utilize any suitable RAT to facilitate wireless connectivity in a local area, such as a business location, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a road, and the like. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.) to establish a micro-micro cell base station or a femto cell base station. As Figure 1A As shown, the base station 114 b may have a direct connection to the Internet 110. Therefore, the base station 114 b may not need to access the Internet 110 via the CN 106.

[0033] The RAN 104 may be in communication with the CN 106, which may be any type of network configured to provide voice, data, applications, and / or Voice over Internet Protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have different quality of service (QoS) requirements, such as different throughput requirements, delay requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 may provide call control, billing services, mobile location-based services, pre-paid calling, Internet connectivity, video distribution, etc., and / or perform high-level security functions, such as user authentication. Although not described in detail in the accompanying drawings, the CN 106 may be configured to provide voice, data, applications, and / or Voice over Internet Protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. Figure 1A Although not shown in the figure, it will be appreciated that the RAN 104 and / or the CN 106 may be in direct or indirect communication with other RANs that employ the same RAT or a different RAT as the RAN 104. For example, in addition to being connected to the RAN 104, which may utilize NR radio technology, the CN 106 may also be in communication with another RAN (not shown) that employs GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0034] The CN 106 may also 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 that provides plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols, such as the Transmission Control Protocol (TCP), the User Datagram Protocol (UDP), and / or the Internet Protocol (IP) in the TCP / IP Internet protocol suite. The networks 112 may include wired communication networks and / or wireless communication networks owned and / or operated by other service providers. For example, the networks 112 may include another CN connected to one or more RANs, which may employ the same RAT as the RAN 104 or a different RAT.

[0035] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communication system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks via different wireless links). Figure 1A The illustrated WTRU 102c may be configured to communicate with the base station 114a, which may employ a cellular-based radio technology, and with the base station 114b, which may employ an IEEE 802 radio technology.

[0036] Figure 1B is a system diagram illustrating an example WTRU 102. Figure 1B As shown, the WTRU 102 may include, among other things, a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and / or other peripherals 138. It will be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0037] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors associated with a DSP core, a controller, a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), any other type of integrated circuit (IC), a state machine, etc. The processor 118 may perform signal coding, data processing, power control, input / output processing, and / or any other functions that enable the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. Although Figure 1B The processor 118 and the transceiver 120 are depicted as separate components, but it is understood that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0038] The send / receive element 122 may be configured to send a signal to a base station (e.g., base station 114a) or receive a signal from a base station via an air interface 116. For example, in one embodiment, the send / receive element 122 may be an antenna configured to send and / or receive an RF signal. In one embodiment, the send / receive element 122 may be a transmitter / detector configured to send and / or receive, for example, an IR, UV, or visible light signal. In another embodiment, the send / receive element 122 may be configured to send and / or receive both an RF signal and an optical signal. It should be understood that the send / receive element 122 may be configured to send and / or receive any combination of wireless signals.

[0039] Although the transmit / receive element 122 Figure 1B 1 as a single element, the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may employ MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit / receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0040] The transceiver 120 may be configured to modulate signals to be transmitted by the transmit / receive element 122 and to demodulate signals received by the transmit / receive element 122. As noted above, the WTRU 102 may have multi-mode capabilities. For example, the transceiver 120 may include multiple transceivers to enable the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11.

[0041] The processor 118 of the WTRU 102 may be coupled to and may receive user input data from a speaker / microphone 124, a keypad 126, and / or a display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light emitting diode (OLED) display unit). The processor 118 may also output user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. In addition, the processor 118 may access information from and store data in any type of suitable memory, such as a non-removable memory 130 and / or a removable memory 132. The non-removable memory 130 may include a random access memory (RAM), a read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, or the like. In other embodiments, the processor 118 may access information from, and store data in, memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0042] 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 suitable device for powering the WTRU 102. For example, the power source 134 may include one or more dry cell batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel-metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, etc.

[0043] The processor 118 may also be coupled to the GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to or in lieu of the information from the GPS chipset 136, the WTRU 102 may receive location information from a base station (e.g., base stations 114a, 114b) over the air interface 116 and / or determine its location based on the timing of signals received from two or more nearby base stations. It will be appreciated that the WTRU 102 may acquire location information by any suitable location-determination method while remaining consistent with an embodiment.

[0044] The processor 118 may also be coupled to other peripherals 138, which may include one or more software modules and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos and / or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, module, a frequency modulation (FM) radio unit, a digital music player, a media player, a video game player module, an Internet browser, a virtual reality and / or augmented reality (VR / AR) device, an activity tracker, etc. The peripheral device 138 may include one or more sensors. The sensor may be one or more of the following: a gyroscope, an accelerometer, a Hall effect sensor, a magnetometer, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor; a geographic location sensor, an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, a gesture sensor, a biometric sensor, a humidity sensor, etc.

[0045] The WTRU 102 may include a full-duplex radio for which transmission and reception of some or all of the signals (e.g., associated with specific subframes for both UL (e.g., for transmission) and DL (e.g., for reception)) may be concurrent and / or simultaneous. The full-duplex radio may include an interference management unit for reducing and / or substantially eliminating self-interference via hardware (e.g., a choke) or via signal processing performed by a processor (e.g., a separate processor (not shown) or via the processor 118). In one embodiment, the WTRU 102 may include a half-duplex radio for which transmission and reception of some or all of the signals (e.g., associated with specific subframes for both UL (e.g., for transmission) or DL ​​(e.g., for reception)) may be concurrent and / or simultaneous.

[0046] Figure 1C 1 is a system diagram illustrating the RAN 104 and the CN 106 according to one embodiment. As noted above, the RAN 104 may employ an E-UTRA radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0047] The RAN 104 may include evolved Node-Bs 160a, 160b, 160c, though it will be appreciated that the RAN 104 may include any number of evolved Node-Bs while remaining consistent with an embodiment. The evolved Node-Bs 160a, 160b, 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the evolved Node-Bs 160a, 160b, 160c may implement MIMO technology. Thus, the evolved Node-B 160a, for example, may use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a.

[0048] Each of the evolved Node Bs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, etc. Figure 1C As shown, the eNode-Bs 160a, 160b, 160c may communicate with one another via an X2 interface.

[0049] Figure 1C The illustrated CN 106 may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (PGW) 166. Although the foregoing elements are depicted as part of the CN 106, it should be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0050] The MME 162 may be connected to each of the evolved Node-Bs 162a, 162b, 162c in the RAN 104 via an S1 interface and may serve as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, bearer activation / deactivation, selecting a particular serving gateway during an 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 GSM and / or WCDMA.

[0051] The SGW 164 may be connected to each of the evolved Node-Bs 160a, 160b, 160c in the RAN 104 via an S1 interface. The SGW 164 may generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions, such as anchoring the user plane during inter-evolved Node-B handovers, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, managing and storing the context of the WTRUs 102a, 102b, 102c, and the like.

[0052] The SGW 164 may be connected to the PGW 166, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0053] The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. For example, the CN 106 may include, or may be in communication with, an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that 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 networks and / or wireless networks owned and / or operated by other service providers.

[0054] Although the WTRU Figures 1A to 1D Although described as wireless terminals, it is contemplated that in certain representative embodiments, such terminals may (eg, temporarily or permanently) use a wired communication interface with a communication network.

[0055] In a representative embodiment, the other network 112 may be a WLAN.

[0056] A WLAN in infrastructure basic service set (BSS) mode may have an access point (AP) for a BSS and one or more stations (STA) associated with the AP. The AP may have access or an interface to a distribution system (DS) or another type of wired / wireless network that carries traffic to and / or carries traffic away from the BSS. Traffic originating from outside the BSS and leading to the STA may be reached by the AP and may be delivered to the STA. Traffic originating from the STA and leading to a destination outside the BSS may be sent to the AP to be delivered to the corresponding destination. Traffic between STAs within the BSS may be sent by the AP, for example, wherein the source STA may send traffic to the AP, and the AP may deliver traffic to the destination STA. Traffic between STAs within the BSS may be considered and / or referred to as point-to-point traffic. Point-to-point traffic may be sent between the source STA and the destination STA (e.g., directly between them) using a direct link setup (DLS). In certain representative embodiments, the DLS may use 802.11e DLS or 802.11z tunnel DLS (TDLS). A WLAN using an independent BSS (IBSS) mode may not have an AP, and STAs within or using the IBSS (eg, all STAs in the STA) may communicate directly with each other. The IBSS communication mode may sometimes be referred to herein as an "ad hoc" communication mode.

[0057] When using the 802.11ac infrastructure operating mode or a similar operating mode, the AP may send beacons on a fixed channel, such as a primary channel. The primary channel may be a fixed width (e.g., a 20 MHz wide bandwidth) or a dynamically set width. The primary channel may be an operating channel of the BSS and may be used by the STA to establish a connection with the AP. In certain representative embodiments, carrier sense multiple access / collision avoidance (CSMA / CA) may be implemented, for example, in an 802.11 system. For CSMA / CA, a STA (e.g., each STA) (including the AP) may listen to the primary channel. If the primary channel is listened / detected and / or determined to be busy by a particular STA, the particular STA may back off. One STA (e.g., only one station) may transmit at any given time in a given BSS.

[0058] High throughput (HT) STAs may communicate using a 40 MHz wide channel, for example, via a combination of a primary 20 MHz channel and adjacent or non-adjacent 20 MHz channels to form a 40 MHz wide channel.

[0059] Very high throughput (VHT) STA can support 20MHz, 40MHz, 80MHz and / or 160MHz wide channels. 40MHz and / or 80MHz channels can be formed by combining continuous 20MHz channels. A 160MHz channel can be formed by combining 8 continuous 20MHz channels, or by combining two non-continuous 80MHz channels (this can be called 80+80 configuration). For the 80+80 configuration, after channel coding, the data can pass through a segment parser that can divide the data into two streams. Each stream can be processed by inverse fast Fourier transform (IFFT) and time domain processing separately. These streams can be mapped to two 80MHz channels, and data can be transmitted by transmitting STA. At the receiver of the receiving STA, the above-mentioned operation for the 80+80 configuration can be reversed, and the combined data can be sent to the medium access control (MAC).

[0060] 802.11af and 802.11ah support operating modes below 1GHz. Channel operating bandwidths and carriers are reduced in 802.11af and 802.11ah relative to those used in 802.11n and 802.11ac. 802.11af supports 5MHz, 10MHz, and 20MHz bandwidths in the TV White Space (TVWS) spectrum, and 802.11ah supports 1MHz, 2MHz, 4MHz, 8MHz, and 16MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11ah may support meter type control / machine type communication (MTC), such as MTC devices in macro coverage areas. MTC devices may have certain capabilities, such as limited capabilities, including support for (e.g., only support for) certain bandwidths and / or limited bandwidths. MTC devices may include batteries with battery life above a threshold (e.g., to maintain very long battery life).

[0061] WLAN systems that can support multiple channels and channel bandwidths such as 802.11n, 802.11ac, 802.11af, and 802.11ah include channels that can be designated as primary channels. The primary channel may have a bandwidth equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be set and / or limited by a STA (which supports the minimum bandwidth operating mode) from all STAs operating in the BSS. In the example of 802.11ah, for STAs (e.g., MTC-type devices) that support (e.g., only support) 1MHz mode, the primary channel may be 1MHz wide, even if the AP and other STAs in the BSS support 2MHz, 4MHz, 8MHz, 16MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or network allocation vector (NAV) settings may depend on the state of the primary channel. If the primary channel is busy, for example, because a STA (supporting only the 1MHz operating mode) is transmitting to the AP, all available frequency bands may be considered busy even if most of the available frequency bands remain idle.

[0062] In the United States, the available frequency band for 802.11ah is 902MHz to 928MHz. In South Korea, the available frequency band is 917.5MHz to 923.5MHz. In Japan, the available frequency band is 916.5MHz to 927.5MHz. The total bandwidth available for 802.11ah is 6MHz to 26MHz, depending on the country code.

[0063] Figure 1D1 is a system diagram illustrating the RAN 104 and the CN 106 according to one embodiment. As noted above, the RAN 104 may employ NR radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0064] The RAN 104 may include gNBs 180a, 180b, 180c, though it will be appreciated that the RAN 104 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, 180c may each include one or more transceivers to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, the gNBs 180a, 180b may utilize beamforming to send signals to and / or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a may, for example, use multiple antennas to send wireless signals to and / or receive wireless signals from the WTRU 102a. In one embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation technology. For example, the gNB 180a may send multiple component carriers to the WTRU 102a (not shown). A subset of these component carriers may be on an unlicensed spectrum, while the remaining component carriers may be on a licensed spectrum. In one embodiment, the gNBs 180a, 180b, 180c may implement coordinated multi-point (CoMP) technology. For example, the WTRU 102a may receive coordinated transmissions from the gNB 180a and gNB 180b (and / or gNB 180c).

[0065] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with scalable parameter sets. For example, OFDM symbol spacing and / or OFDM subcarrier spacing may vary for different transmissions, different cells, and / or different portions of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using subframes or Transmission Time Intervals (TTIs) of varying or scalable lengths (e.g., containing different numbers of OFDM symbols and / or varying absolute time lengths over time).

[0066] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c while also not accessing other RANs (e.g., such as the eNodeBs 160a, 160b, 160c). In a standalone configuration, the WTRUs 102a, 102b, 102c may use one or more of the gNBs 180a, 180b, 180c as mobility anchor points. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration, the WTRUs 102a, 102b, 102c may communicate / connect with the gNB 180a, 180b, 180c while also communicating / connecting with another RAN, such as the evolved Node-B 160a, 160b, 160c. For example, the WTRUs 102a, 102b, 102c may implement the DC principle to communicate with one or more gNBs 180a, 180b, 180c and one or more evolved Node-Bs 160a, 160b, 160c substantially simultaneously. In a non-standalone configuration, the evolved Node-B 160a, 160b, 160c may serve as a mobility anchor for the WTRUs 102a, 102b, 102c, and the gNB 180a, 180b, 180c may provide additional coverage and / or throughput for serving the WTRUs 102a, 102b, 102c.

[0067] Each of the gNBs 180a, 180b, 180c may be associated with a specific cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in UL and / or DL, support of network slicing, interworking between DC, NR, and E-UTRA, routing of user plane data towards a user plane function (UPF) 184a, 184b, routing of control plane information towards an access and mobility management function (AMF) 182a, 182b, etc. Figure 1D As shown, gNBs 180a, 180b, and 180c may communicate with each other via an Xn interface.

[0068] Figure 1DThe CN 106 shown may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one session management function (SMF) 183a, 183b, and possible data networks (DNs) 185a, 185b. Although the foregoing elements are depicted as part of the CN 106, it should be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0069] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 104 via the N2 interface and may serve as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRU 102a, 102b, 102c, support of network slicing (e.g., handling of different protocol data unit (PDU) sessions with different requirements), selecting a specific SMF 183a, 183b, management of registration areas, termination of non-access stratum (NAS) signaling, mobility management, etc. The AMF 182a, 182b may use network slicing to customize CN support for the WTRU 102a, 102b, 102c based on the type of services used by the WTRU 102a, 102b, 102c. For example, different network slices may be established for different use cases, such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced mobile broadband (eMBB) access, services for MTC access, etc. The AMF 182a, 182b may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies, such as WiFi.

[0070] The SMF 183a, 183b may be connected to the AMF 182a, 182b in the CN 106 via the N11 interface. The SMF 183a, 183b may also be connected to the UPF 184a, 184b in the CN 106 via the N4 interface. The SMF 183a, 183b may select and control the UPF 184a, 184b, and configure traffic routing through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions such as managing and allocating UE IP addresses, managing PDU sessions, controlling policy enforcement and QoS, providing DL data notifications, etc. The PDU session type may be IP-based, non-IP-based, Ethernet-based, etc.

[0071] The UPF 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 104 via the N3 interface, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPF 184, 184b may perform other functions, such as routing and forwarding packets, enforcing user plane policies, supporting multi-homed PDU sessions, handling user plane QoS, buffering DL packets, providing mobility anchoring, etc.

[0072] The CN 106 may facilitate communications with other networks. For example, the CN 106 may include or may communicate with an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that serves as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired networks and / or wireless networks owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to the DNs 185a, 185b via the UPFs 184a, 184b via the N3 interfaces to the UPFs 184a, 184b and the N6 interfaces between the UPFs 184a, 184b and the local DNs 185a, 185b.

[0073] Given that Figures 1A to 1D as well as Figures 1A to 1D Corresponding to the description of the present invention, one or more or all of the functions described herein with reference to one or more of the following may be performed by one or more simulation devices (not shown): WTRU102a-d, base station 114a-b, evolved Node B 160a-c, MME 162, SGW 164, PGW 166, gNB 180a-c, AMF182a-b, UPF 184a-b, SMF 183a-b, DN 185a-b and / or any other device described herein. The simulation device may be one or more devices configured to emulate one or more or all of the functions described herein. For example, the simulation device may be used to test other devices and / or simulate network and / or WTRU functions.

[0074] The simulation device may be designed to implement one or more tests of other devices in a laboratory environment and / or an operator network environment. For example, the one or more simulation devices may perform one or more functions or all functions while being fully or partially implemented and / or deployed as part of a wired and / or wireless communication network in order to test other devices within the communication network. The one or more simulation devices may perform one or more functions or all functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network. The simulation device may be directly coupled to another device for testing purposes and / or perform testing using over-the-air wireless communications.

[0075] The one or more simulation devices may perform one or more (including all) functions without being implemented / deployed as part of a wired and / or wireless communication network. For example, the simulation device may be used in a test scenario in a test lab and / or a non-deployed (e.g., testing) wired and / or wireless communication network to implement testing of one or more components. The one or more simulation devices may be test equipment. Direct RF coupling and / or wireless communication via RF circuits (e.g., which may include one or more antennas) may be used by the simulation device to send and / or receive data.

[0076] The following terms may be used throughout this disclosure.

[0077] ACK

[0078] BLER Block Error Rate

[0079] CB is based on contention conflicts (e.g. access, channel, resource)

[0080] CBR Channel Busy Rate

[0081] CP Cyclic Prefix

[0082] CP-OFDM Conventional OFDM (relies on cyclic prefix)

[0083] CQI Channel Quality Indicator

[0084] CR Channel occupancy rate

[0085] CRC Cyclic Redundancy Check

[0086] CSI Channel State Information

[0087] D2D device-to-device transmission (e.g., LTE sidelink)

[0088] DCI Downlink Control Information

[0089] DFT-s-OFDM Digital Fourier Transform Extended OFDM

[0090] DL Downlink

[0091] DMRS Demodulation Reference Signal

[0092] FB Feedback

[0093] FDD Frequency Division Duplex

[0094] FDM Frequency Division Multiplexing

[0095] LBT Listen before you speak

[0096] LLC Low Latency Communications

[0097] LTE LTE Long Term Evolution, e.g. from 3GPP LTE Release 8 and higher

[0098] MAC Media Access Control

[0099] NACK Negative ACK

[0100] MBB Massive Broadband Communication

[0101] MC Multi-Carrier

[0102] MCS modulation and coding scheme

[0103] OFDM Orthogonal Frequency Division Multiplexing

[0104] OOB Out of Band (Emit)

[0105] P cmax Total available UE power in a given TI

[0106] PC5-S PC5 Signaling

[0107] PDB Packet Delay Budget

[0108] PHY Physical Layer

[0109] PSCCH Physical SL Control Channel

[0110] PSFCH Physical SL Feedback Channel

[0111] PSS Primary Synchronization Signal

[0112] PSSCH Physical SL Shared Channel

[0113] PSSCH-RSRP PSSCH reference signal received power

[0114] QoS Quality of Service (from the perspective of the physical layer)

[0115] RNTI Radio Network Identifier

[0116] RRC Radio Resource Control

[0117] RRM Radio Resource Management

[0118] RS reference signal

[0119] RSRP Reference Signal Received Power

[0120] RSRQ Reference Signal Received Quality

[0121] RTT Round Trip Time

[0122] S-RSSI SL Received Signal Strength Indicator

[0123] SL Sidelink

[0124] SL-RSRP Sidelink reference signal received power

[0125] SD-RSRP Sidelink Discovery Reference Signal Received Power

[0126] SS Sync Signal

[0127] SSS Auxiliary Sync Signal

[0128] TB Transfer Block

[0129] TDD Time Division Duplex

[0130] TDM Time Division Multiplexing

[0131] TTI Transmit Time Interval

[0132] TRP Send / Receive Point

[0133] TRX Transceiver

[0134] UL Uplink

[0135] URLLC Ultra-Reliable Low Latency Communications

[0136] V2X vehicle-to-vehicle communications

[0137] The terms UE to UE (U2) relay and WTRU to WTRU relay may be used interchangeably throughout this disclosure. The terms UE to UE (U2U) and WTRU to WTRU may be used interchangeably throughout this disclosure. The terms UE to network (U2N) relay and WTRU to network relay may be used interchangeably throughout this disclosure. The terms UE to network (U2N) and WTRU to network may be used interchangeably throughout this disclosure.

[0138] Start relay description

[0139] Current 5G wireless communication systems mainly operate on network-to-device communication links, where data flows directly between a base station (network) and a wireless user equipment (UE or WTRU). In order to extend the coverage of a base station, sidelink relays may be used, which refers to the use of both WTRU-to-network relays and WTRU-to-WTRU relays.

[0140] Figure 2 is a diagram of an example wireless communication system for implementing sidelink relay.

[0141] The exemplary system includes a network node or gNB 210. The network node 210 is configured to communicate wirelessly with a mobile user equipment (UE). Three signal level thresholds are shown at increasing distances from the node 210. A plurality of user equipments (UEs) are shown. The user equipments (UEs) (220, 222, 224) are shown as being positioned between threshold 1 and threshold 2. The user equipments (UEs) (230, 232) are shown as being positioned between threshold 2 and threshold 3. The user equipments (UEs) (240, 250, 252) are shown as being positioned outside of threshold 3. As shown, UEs 220, 222, and 232 communicate directly with the node 210. These direct UE-node links (210a, 210b, 210c) are labeled Uu. UEs 220 and 222 are shown as sending U2N discovery messages, i.e., advertising to other UEs that they are available for direct relaying back to the node 220 from another UE (e.g., 232, 240). UEs 230, 232, and 240 are shown sending U2U discovery messages (230a, 233a, 240a), i.e., advertising themselves to other UEs as being available for relaying from the other UEs to another UE closer to node 210. UEs 250 and 252 are shown as remote UEs that cannot communicate directly with node 210, but can communicate with the node via relays 232a and 240a through US 232 and 240, respectively.

[0142] In discovery model A, the U2N relay sends a discovery advertisement message to a remote UE. In discovery model B, the remote UE sends a request message to request relay service from another relay UE. The U2N relay may then respond to the request message from the remote UE. Figure 2 An exemplary system employing discovery model A is shown.

[0143] In contrast to single-hop relays, for multi-hop relays (e.g. Figure 2As shown, via UEs 222, 240, 252), a relay (e.g., a U2U relay) may be within or outside network coverage (e.g., UE 240). In a scenario where each UE may send discoveries and become a U2U relay, allowing each UE to do so may waste resources and cause congestion in the discovery resource pool. Described below are methods for determining which UEs or wireless transmit / receive units (WTRUs) send discovery messages and / or what information the discovery messages should include.

[0144] For Model A discovery, the WTRU may be (pre)-configured with multiple (e.g., two) Uu RSRP ranges, where the first range may be used when the WTRU sends a discovery message to become a WTRU-to-network relay (e.g., directly connected to the gNB), and the second range may be used when the WTRU sends a discovery message to become a WTRU-to-WTRU relay (e.g., not directly connected to the gNB). The WTRU may then determine whether to send a discovery message based on whether the WTRU is targeting to become a WTRU-to-WTRU relay or a WTRU-to-network relay and whether the measured Uu RSRP is within the associated range. Specifically, if the Uu RSRP is within the first range (e.g., Thres2 < Uu RSRP < Thres1), the WTRU may send a discovery message to be used as a WTRU-to-network relay. Otherwise, if the Uu RSRP is within the second range (e.g., Thres3 < Uu RSRP < Thres2), the WTRU may send a discovery message to be used as a WTRU-to-WTRU relay. The WTRU may also determine whether to send a discovery message to be used as a WTRU-to-WTRU based on whether it detects a WTRU-to-network relay. Specifically, if the WTRU detects a WTRU-to-network relay, the WTRU may send a discovery message to be used as a WTRU-to-WTRU; otherwise, the WTRU may not send the discovery message.

[0145] Figure 5 An exemplary WTRU-to-network relay discovery using Model A is shown. In Model A, the WTRU-to-network relay may send an advertisement message. The UE 510 that advertises the availability as a UE-network relay sends discovery advertisement messages 512, 514, 516, which are received by remote UEs 1 (520), 2 (530), and 3 (540). In an embodiment, the UE that advertises the availability as a UE-network relay may also send additional information (517, 518, 519) to the remote UEs (520, 530, 540) respectively.

[0146] Figure 6An exemplary WRTU to network relay discovery using Model B is shown. In Model B, a remote WRTU (e.g., 610) may send a request message (610, 612, 614) requesting relay service from another relay WTRU (e.g., 620, 630, 640). Subsequently, the WTRU to network relay may respond to the request message from the remote WTRU. In this example, UE-Network Relay 1 (620) and UE-Network Relay 2 (630) respond to the remote UE 610 with discovery response messages 622 and 632, respectively.

[0147] Coverage extension based on sidelink communication may include WTRU to network coverage extension and WTRU to WTRU coverage extension. For WTRU to network coverage extension, the WTRU may need Uu coverage reachability to reach a server in the PDN network or a corresponding WTRU outside the proximity area.

[0148] For WTRU to WTRU coverage extension, proximity reachability may be limited to a single-hop sidelink via EUTRA-based or NR-based sidelink technology. However, this may not be sufficient in the absence of Uu coverage, given the limited single-hop sidelink coverage. In summary, the sidelink connectivity may be further extended in the NR framework to support enhanced QoS requirements.

[0149] A mechanism with minimal regulatory impact that supports the SA requirements for sidelink-based WTRU-to-network and WTRU-to-WTRU relaying, focusing on the following aspects of Layer 3 relay and Layer 2 relay [RAN2] (as applicable); relay (re)selection criteria and procedures; relay / remote WTRU authorization; QoS for relay functionality; service continuity; security of the relay connection after SA3 has provided its conclusion; and impact on the user plane protocol stack and control plane procedures (e.g., connection management of relay connections).

[0150] The mechanisms supporting the upper layer operations of the discovery model / process for sidelink relay may assume that there are no new physical layer channels / signals [RAN2]. The same relay implementation may be used for WTRU to network relay and WTRU to WTRU relay. For layer 2 WTRU to network relay, the architecture of end-to-end PDCP and hop-by-hop RLC may be used as a starting point.

[0151] Relaying via the ProSe WTRU to Network Relay may extend network coverage to out-of-coverage WTRUs by using PC5 (D2D) between the out-of-coverage WTRU and the WTRU to Network Relay. The ProSe WTRU to Network Relay may provide a generic L3 forwarding function that may relay any type of IP traffic between a remote WTRU and the network. One-to-one and one-to-many sidelink communications may be used between the remote WTRU and the ProSe WTRU to Network Relay. For both the remote WTRU and the relay WTRU, only one single carrier (i.e., the public safety ProSe carrier) operation may be supported (i.e., Uu and PC5 may be the same carrier for the relay / remote WTRU). The remote WTRU may be authorized by upper layers and may be within the coverage of the public safety ProSe carrier or out of coverage of any supported carrier, including the public safety ProSe carrier for WTRU to Network Relay discovery, (re)selection and communication. The ProSe WTRU to Network Relay may always be within the coverage of the EUTRAN. ProSe WTRU to network relay and remote WTRU can perform sidelink communication and sidelink discovery.

[0152] The relay selection / reselection of a ProSe WTRU to network relay may be performed based on a combination of AS layer quality measurements (e.g., RSRP) and / or upper layer criteria. Specifically, a base station (BS) (e.g., eNB) may control whether a WTRU may act as a ProSe WTRU to network relay. If the BS (e.g., eNB) broadcasts any information associated with the ProSe WTRU to network relay operation, the ProSe WTRU to network relay operation may be supported in the cell.

[0153] The BS (e.g., eNB) may provide transmit resources for ProSe WTRU to network relay discovery using broadcast signaling for RRC_IDLE state and dedicated signaling for RRC_CONNECTED state. The BS (e.g., eNB) may provide receive resources for ProSe WTRU to network relay discovery using broadcast signaling. The BS (e.g., eNB) may broadcast minimum and / or maximum Uu link quality (e.g., RSRP) thresholds that the ProSe WTRU to network relay needs to comply with before it may initiate the WTRU to network relay discovery procedure. When in RRC_IDLE, when the BS (e.g., eNB) broadcasts the transmit resource pool, the WTRU may use the thresholds to autonomously start or stop the WTRU to network relay discovery procedure. When in RRC_CONNECTED, the WTRU may use the thresholds to determine whether it can indicate to the BS (e.g., eNB) that it is a relay WTRU and wishes to initiate ProSe WTRU to network relay discovery.

[0154] If the BS (eg, eNB) does not broadcast the transmit resource pool for ProSe-WTRU to network relay discovery, then subject to these broadcast thresholds, the WTRU may initiate a request for ProSe-WTRU to network relay discovery resources through dedicated signaling.

[0155] If the ProSe-WTRU to network relay is initiated by broadcast signaling, the ProSe WTRU to network relay discovery may be performed when in RRC_IDLE. If the ProSe WTRU to network relay is initiated by dedicated signaling, the relay discovery may be performed as long as it is in RRC_CONNECTED.

[0156] A ProSe WTRU to network relay that performs sidelink communication for ProSe WTRU to network relay operation must be in RRC_CONNECTED. After receiving a Layer 2 Link Establishment Request or a TMGI Monitoring Request (e.g., an upper layer message) from a remote WTRU, the ProSe WTRU to network relay may indicate itself to the BS (e.g., eNB) as a ProSe WTRU to network relay and intends to perform ProSe WTRU to network relay sidelink communication. The BS (e.g., eNB) may provide resources for ProSe WTRU to network relay communication.

[0157] The remote WTRU may decide when to start monitoring for ProSe WTRU to network relay discovery. Depending on the configuration of resources for ProSe WTRU to network relay discovery, the remote WTRU may send a ProSe WTRU to network relay discovery request message when it is in RRC_IDLE or in RRC_CONNECTED. The BS (e.g., eNB) may broadcast a threshold value that the remote WTRU uses to determine whether it may send a ProSe WTRU to network relay discovery request message to connect or communicate with a ProSe WTRU to network relay WTRU. The RRC_CONNECTED remote WTRU may use the broadcast threshold value to determine whether it may indicate to the BS (e.g., eNB) that it is a remote WTRU and wishes to participate in ProSe WTRU to network relay discovery and / or communication. The BS (e.g., eNB) may use broadcast or dedicated signaling to provide transmit resources and use broadcast signaling to provide receive resources for ProSe WTRU to network relay operation. When the RSRP exceeds the broadcast threshold value, the remote WTRU may stop using the ProSe WTRU to network relay discovery and communication resources.

[0158] The exact time of traffic switching from Uu to PC5 or from PC5 to Uu may be known to higher layers.

[0159] The remote WTRU may perform radio measurements at the PC5 interface and use them together with higher layer criteria for ProSe WTRU to network relay selection and reselection. If the PC5 link quality exceeds a configured threshold (e.g., pre-configured or provided by a BS (such as an eNB)), the ProSe WTRU to network relay may be considered suitable in terms of radio criteria. The remote WTRU may select a ProSe WTRU to network relay that meets the higher layer criteria and has the best PC5 link quality among all suitable ProSe WTRU to network relays.

[0160] The remote WTRU triggers ProSe WTRU to network relay reselection when the current ProSe WTRU to network relay PC5 signal strength is below the configured signal strength threshold. The remote WTRU triggers ProSe WTRU to network relay reselection when it receives a layer 2 link release message (e.g., an upper layer message) from the ProSe WTRU to network relay.

[0161] Figure 3 An exemplary user plane radio protocol stack for a layer 2 evolved user equipment (UE) to network relay (PC5) between a remote WTRU 310, a relay WTRU 320, an eNB 330, and a core network 340 is shown. Communications between the remote WTRU 310 and the relay WTRU are at the physical layer PC5 (321). Communications between the relay WTRU 320 and the eNB 330 are at the physical layer Uu (322). Communications between the eNB and the CN are over S1-U / S5 / S8 (332). Figure 4 An exemplary control plane radio protocol stack for Layer 2 Evolved UE to Network Relay (PC5) is shown. WTRU to Network Relay for business use cases tailored for wearables and IoT devices may be performed in the RAN. In contrast to ProSe WTRU to Network Relay which uses an L3 (e.g., IP layer) relay approach, WTRU to Network Relay for wearables may be based on Figure 3 and Figure 4 The protocol stack shown uses L2 relay (332, 334).

[0162] Relay implementations may be based on a one-to-one communication link established at the upper layers (ProSe layer) between two WTRUs (e.g., a remote WTRU and a WTRU-to-network relay). Such a connection may be transparent to the AS layer and connection management signaling, and the processes performed at the upper layers may be carried by the AS layer data channel. The AS layer may not be aware of such a one-to-one connection.

[0163] In NR V2X, the AS layer may support the concept of a unicast link between two WTRUs. Such a unicast link may be initiated by upper layers (such as in a ProSe one-to-one connection). However, the AS layer may be informed of the existence of such a unicast link and any data that may be sent between peer WTRUs in a unicast manner. With such knowledge, the AS layer may support HARQ feedback, CQI feedback, and unicast-specific power control schemes.

[0164] Unicast links at the AS layer can be supported via a PC5-RRC connection. The PC5-RRC connection can be defined as follows: A PC5-RRC connection is a logical connection between a pair of source layer 2ID and destination layer 2ID in an AS. One PC5-RRC connection corresponds to one PC5 unicast link. PC5-RRC signaling can be initiated after its corresponding PC5 unicast link is established. When the PC5 unicast link is released as indicated by the upper layer, the PC5-RRC connection and the corresponding sidelink SRB and sidelink DRB are released. For each PC5-RRC connection for unicast, a sidelink SRB is used to send a PC5-S message before PC5-S security is established. One sidelink SRB is used to send a PC5-S message to establish PC5-S security. One sidelink SRB is used to send a PC5-S message after PC5-S security has been established, and the message is protected. One sidelink SRB is used to transport PC5-RRC signaling, which is protected and sent only after PC5-S security has been established.

[0165] PC5-RRC signaling may include a sidelink configuration message (e.g., RRCReconfigurationSidelink) in which one WTRU configures the RX related parameters of each sidelink radio bearer (SLRB) in the peer WTRU. Such reconfiguration message may configure the parameters of each protocol in the L2 stack (e.g., SDAP, PDCP, etc.). The receiving WTRU may confirm or reject such configuration, depending on whether it can support the configuration proposed by the peer WTRU.

[0166] In an embodiment, a WTRU (e.g., a WTRU-to-WTRU relay WTRU) is (pre-)configured with some or all of the following conditions for sending / forwarding discovery messages:

[0167] 1) SD-RSRP range from the parent node and / or distance range to the parent node for each QoS served by the relay.

[0168] 2) If the WTRU is within coverage, the WTRU is (pre-)configured to check the UuRSRP (reference signal received power) as a condition; otherwise, the WTRU checks the distance to the gNB as a condition. For example:

[0169] 2a) In an embodiment, check the Uu RSRP range per hop to the gNB for each QoS of the relay service. For example, for a QoS level, if Thre1 ≥ Uu RSRP > Thre2, the WTRU may relay for the WTRU to the network, and if Thre2 ≥ Uu RSRP ≥ Thre3, the WTRU may relay for the first intermediate WTRU to the WTRU. Otherwise, if UuRSRP < Thre3 (e.g., the WTRU is out of coverage (OOC)), the WTRU may be an intermediate relay.

[0170] 2b) In another embodiment, check the distance range to the gNB per hop count to the gNB for each QoS of the relay service.

[0171] In an embodiment, if the WTRU does not meet the condition to become a WTRU-to-network relay (e.g., it can only be a WTRU-to-WTRU relay). Perform the following actions:

[0172] 1) In an embodiment, the WTRU monitors discovery transmissions from the parent node and performs the following operations for each detected discovery message, where each discovery message includes any or all of the following: path information, hop count to the gNB, location information of the parent node and the gNB (e.g., cell ID, coordinates), and QoS of the relay service.

[0173] 1a) The WTRU determines the hop count to the gNB.

[0174] 1b) The WTRU measures SD-RSRP and calculates the distances to the parent node and to the gNB.

[0175] 2) The discovery message sent by the WTRU may include the following information:

[0176] 2a) If the WTRU has an ongoing connection with the gNB, the WTRU may include the current path. Otherwise, the WTRU may include the shortest path based on detected discovery announcements from other nodes.

[0177] 2b) Path status (e.g., whether the WTRU has an ongoing connection with the gNB).

[0178] 3) For discovery transmissions, if the WTRU is within network coverage (e.g., UuRSRP > Thre3), in an embodiment, the WTRU checks the Uu RSRP as a condition. Otherwise, the WTRU checks the distance to the gNB as a condition.

[0179] 4) In an embodiment, if pre-configured conditions are met and / or the WTRU receives an indication to send a discovery from a parent node, the WTRU triggers the sending of a discovery announcement.

[0180] In another embodiment, the WTRU (e.g., a WTRU-to-WTRU relay WTRU) is pre-configured with the following conditions for forwarding discovery messages:

[0181] 1) The SD-RSRP range from a child node and / or the distance range to a child node for each QoS of the relay service.

[0182] 2) If the WTRU is within coverage, the WTRU is pre-configured to check the Uu RSRP condition; otherwise, the WTRU checks the distance condition to the gNB as follows:

[0183] 2a) In an embodiment, the WTRU checks the Uu RSRP range per hop to the gNB for each QoS of the relay service. For example, for a QoS service, if Thre1 ≥ Uu RSRP > Thre2, the WTRU may be a WTRU-to-network relay, and if Thre2 ≥ Uu RSRP ≥ Thre3, the WTRU may be a first intermediate WTRU-to-WTRU relay. Otherwise, if Uu RSRP < Thre3 (e.g., the WTRU is in OOC), the WTRU may be any intermediate relay.

[0184] 2b) In an embodiment, the WTRU checks the distance range to the gNB per hop count to the gNB for each QoS of the relay service.

[0185] In another embodiment, the WTRU (e.g., a WTRU-to-WTRU relay WTRU) monitors discovery request messages from a child WTRU (e.g., a remote WTRU) and discovery announcement messages from a parent node (e.g., a WTRU-to-network relay).

[0186] If the WTRU has an ongoing connection with the gNB, for each detected discovery request message, the WTRU determines the remaining hop count to the gNB based on the indication in the message. If the hop count to the gNB is less than the remaining hops in the discovery request message, the WTRU forwards the path information of the detected discovery message to the parent node using PC5-RRC.

[0187] Otherwise, if the WTRU does not have an ongoing connection with the gNB, the WTRU determines the shortest path to the gNB based on the detected discovery announcement message from the parent node, and if the conditions for sending the discovery request message based on the number of hops in the shortest path are met (for example, the Uu RSRP condition if the WTRU is within the coverage area, and the distance condition to the gNB if the WTRU is out of the network coverage), the discovery request message is used to forward the detected path information of the discovery message.

[0188] Embodiments for discovery transmission are described herein.

[0189] In an embodiment, the WTR performs discovery monitoring. In an embodiment, the WTRU determines whether to monitor discovery transmissions from other WTRUs for multi-hop relaying. For example, for Model A discovery, if the WTRU does not meet the conditions to become a WTRU-to-network relay, the WTRU determines to monitor the discovery resource pool. Specifically, if the Uu RSRP becomes less than a (pre-)configured threshold, the WTRU triggers discovery monitoring to monitor discovery transmissions from the WTRU to the network to provide a WTRU-to-WTRU relay service to the remote WTRU.

[0190] In an embodiment, the first WTRU decodes discovery messages from other WTRUs.The first WTRU performs one or any combination of a Triggered Discovery Sending procedure and a Triggered Relay (re)Selection procedure upon receiving discovery messages from other WTRUs.

[0191] In an embodiment, the first WTRU performs a triggered discovery sending process, for example, the first WTRU (e.g., a WTRU to WTRU relay) monitors discovery messages from a child / parent node (e.g., a WTRU to network relay) sending discovery messages, and transmits the child / parent node information to a remote WTRU to provide a WTRU to WTRU relay service to the remote WTRU.

[0192] In an embodiment, a first WTRU performs a triggered relay (re)selection procedure, for example, a WTRU (e.g., a remote WTRU) has an ongoing connection with a WTRU-to-WTRU relay that is directly connected to a WTRU-to-network relay. The WTRU monitors discovery messages from other WTRUs. If the WTRU detects a discovery message from the WTRU-to-network relay, the WTRU triggers relay (re)selection. If the discovery message from the WTRU-to-network relay satisfies a set of conditions (e.g., SL-RSRP is greater than a threshold), the WTRU triggers relay (re)selection by switching from an existing path to a new path.

[0193] In an embodiment, the WTRU determines the QoS of the relay service. In an embodiment, the QoS of the relay service includes per-hop QoS (hop-by-hop QoS) and QoS from source to destination (i.e., end-to-end QoS). The QoS parameters include one or any combination of a priority associated with the relay service, a delay associated with the relay service, and a reliability associated with the relay service. In an embodiment, the priority associated with the relay service is determined based on the priority of the SLRB / LCH established from the frequency modulation or multiple nodes in the relay path. In an embodiment, the delay associated with the relay service is determined based on the delay associated with one hop and the maximum number of hops allowed from the source to the destination. In an embodiment, the reliability associated with the relay service is determined based on the reliability associated with one hop and the maximum number of hops allowed from the source to the destination.

[0194] In an embodiment, the WTRU determines the QoS of the discovery message. In an embodiment, the QoS of the discovery message includes one or any combination of parameters such as the priority of the message, the reliability of the message, and the delay requirement of the message.

[0195] In an embodiment, the WTRU indicates the relay type in a discovery message. In an embodiment, the WTRU sends a discovery message. In an embodiment, the WTRU indicates its relay type (e.g., WTRU to WTRU relay, WTRU to network relay, number of hops to source / destination, etc.) in a discovery message to provide relay services to another WTRU. In an embodiment, the WTRU indicates that it is a WTRU to WTRU relay and / or a WTRU to network relay. In an embodiment, the WTRU sends a discovery message to indicate that it can be a WTRU to network relay. In another embodiment, the WTRU sends a discovery message to indicate that it can be a WTRU to WTRU relay. In another embodiment, the WTRU sends a discovery message to indicate that it can be a WTRU to WTRU relay or a WTRU to network relay. In an embodiment, the indication is indicated implicitly or explicitly in the discovery message.

[0196] In an embodiment, the WTRU determines its relay type. In an embodiment, the WTRU determines its relay type (e.g., WTRU-to-WTRU relay, WTRU-to-network relay) based on one or any combination of the following:

[0197] 1) (Pre-) configuration. For example, the WTRU is (pre-)configured as WTRU to WTRU and

[0198] / or WTRU to network relay. The WTRU then determines its own relay type based on such (pre-) configuration.

[0199] 2) The shortest path to the source / destination node (e.g., gNB). For example, the WTRU determines whether to become a WTRU-to-network relay or a WTRU-to-WTRU relay. In an embodiment, the WTRU is prioritized to become a U2N relay. If the conditions for becoming a U2N relay are not met, the WTRU then determines to become a WTRU-to-WTRU relay.

[0200] 3) Detection of parent / child nodes. In an embodiment, if the WTRU detects a discovery message from a U2N relay, the WTRU determines to be a WTRU-to-WTRU relay of a U2N relay.

[0201] 4) Measured Uu RSRP. In an embodiment, if the WTRU's measured Uu RSRP is within a (pre-)configured range, then the WTRU determines to be a U2N relay. If the WTRU's measured Uu RSRP is within another Uu RSRP range, then the WTRU determines to be a WTRU-WTRU relay directly connected to a U2N relay.

[0202] 5) Coverage status of the WTRU. In an embodiment, if the WTRU is in coverage, the WTRU determines to be a U2N relay, and if the WTRU is out of coverage, the WTRU determines to be a WTRU-WTRU relay connected to a U2N relay.

[0203] 6) Uu RRC state of the WTRU. In an embodiment, if the WTRU is in RRCCONNECTED, then the WTRU determines to be a WTRU-to-network relay. Otherwise, if the WTRU is in RRCIDLE / INACTIVE mode, then the WTRU determines to be a WTRU-to-WTRU relay directly connected to the WTRU-to-network relay.

[0204] In an embodiment, the WTRU determines whether to send a discovery message. In an embodiment, the WTRU determines whether to send a discovery message based on one or any combination of the following: (pre-)configured number of hops to the gNB; remaining number of hops and / or remaining delay to reach the source / destination node; availability of the parent / child node; measured Uu RSRP; measured SLRSRP; distance to the parent / child node and / or distance to the source / destination node; distance to the gNB; coverage status of the WTRU; QoS of the relay service; indication from the child / parent node; connection status to the child / parent node; load of the WTRU; cell ID; and / or PLMN ID.

[0205] In an embodiment, the WTRU determines whether to send a discovery message based on the (pre)configured number of hops to the gNB. In an embodiment, the WTRU determines whether to send a discovery message based on the (pre)configured relay type. In an embodiment, the WTRU is (pre)configured to be a WTRU to network relay only. The WTRU then determines whether to send a discovery message based on the conditions for becoming a WTRU to network relay. In an embodiment, the WTRU is (pre)configured to be a WTRU to WTRU relay WTRU. The WTRU then determines whether to send a discovery message based on the conditions for becoming a WTRU to WTRU relay. The conditions include some or all of the following: availability of the source / destination node, Uu RSRP, etc. In an embodiment, the WTRU is (pre)configured to be a relay, regardless of whether it is a WTRU to WTRU or a WTRU to network relay. The WTRU then determines whether to send a discovery message based on the conditions for sending discovery to become a WTRU to network relay or sending discovery to become a WTRU to WTRU relay.

[0206] In an embodiment, the WTRU determines whether to send a discovery message based on the remaining number of hops and / or the remaining delay to reach the source / destination node. In an embodiment, the WTRU receives a discovery message from a parent / child node, and the WTRU determines whether to send a discovery message to forward the discovery information for the parent / child node based on the remaining number of hops and / or the remaining delay of the discovery message indicated in the discovery message received from the parent / child node. In an embodiment, the WTRU determines the remaining delay and / or the remaining number of hops of the discovery message based on the discovery message received from the parent / child node. In an embodiment, if the remaining delay and / or the remaining number of hops is less than a threshold, the WTRU does not send a discovery message. Otherwise, if the remaining delay and / or the remaining number of hops is greater than the threshold, the WTRU sends a discovery message.

[0207] For example, a WTRU receives a discovery message from a WTRU to a network relay. The WTRU determines whether to send a discovery message forwarding discovery information from the WTRU to the network relay based on the maximum number of hops that the WTRU to the network relay wants to reach the destination / source WTRU, which is implicitly or explicitly indicated in the discovery message from the WTRU to the network relay. If the discovery message indicates that the WTRU to WTRU relay is disabled (i.e., the WTRU to the network relay only serves remote WTRUs), the WTRU shall not send a discovery message forwarding discovery information from the WTRU to the network relay; otherwise, the WTRU shall send a discovery message forwarding discovery information from the WTRU to the network relay.

[0208] In an embodiment, the WTRU determines whether to send a discovery message based on the availability of parent / child nodes. In an embodiment, if the WTRU determines that it is not allowed to be a WTRU-to-network relay, the WTRU determines whether it can be a WTRU-to-WTRU relay that relays messages from / to another WTRU-to-network relay based on the availability of one or more parent / child nodes. In an embodiment, for the Model A discovery process, if the WTRU detects a suitable WTRU-to-network relay, the WTRU determines to send a discovery message; otherwise, the WTRU will not send a discovery message. In an embodiment, the WTRU determines whether it has detected a suitable WTRU-to-network relay by decoding a discovery message from the WTRU-to-network relay. In an embodiment, for the Model B discovery process, if the WTRU detects a suitable remote WTRU, the WTRU determines to send a discovery message; otherwise, if the WTRU does not detect a remote WTRU, the WTRU will not send a discovery message. In another embodiment, if the WTRU detects a suitable child WTRU and another suitable parent WTRU, the WTRU determines to send a discovery message; otherwise, the WTRU will not send a discovery message.

[0209] In an embodiment, the WTRU determines whether to send a discovery message based on its measured Uu RSRP. In an embodiment, the WTRU is (pre-)configured with multiple Uu RSRP ranges, where each range is associated with a type of discovery message, number of hops to the gNB, QoS of the relay service, and / or number of hops to the source / destination node. The WTRU determines which Uu RSRP range to apply based on the number of hops to the gNB and / or the number of hops to the source / destination node. If the measured Uu RSRP is within the range, the WTRU sends a discovery message. Otherwise, the WTRU shall not send a discovery message.

[0210] In one example, if Figure 2As shown, for Model A, it is found that the WTRU is (pre-)configured with multiple (e.g., two) Uu RSRP ranges, where the first range (212 - 214) is used when the WTRU sends a discovery message to become a WTRU-to-network relay (e.g., directly connected to the gNB), and the second range (214 - 216) is used when the WTRU sends a discovery message to become a WTRU-to-WTRU relay (e.g., the WTRU is not directly connected to the gNB). The WTRU then determines whether to send a discovery message based on whether the WTRU is targeted to become a WTRU-to-WTRU relay or a WTRU-to-network relay and whether the measured Uu RSRP is within the associated range. Specifically, if the Uu RSRP is within the first range (e.g., Thres2 < Uu RSRP < Thres1), then the WTRU (e.g., 220, 222) sends a discovery message (e.g., 220a, 222a) to be used as a WTRU-to-network relay. Otherwise, if the Uu RSRP is within the second range (e.g., Thres3 < Uu RSRP < Thres2), then the WTRU (e.g., 230, 232) sends a discovery message (e.g., 230a, 232a) to be used as a WTRU-to-WTRU relay.

[0211] An example of the foregoing embodiment is described in Figure 7 the flowchart as follows: In an example of step 710, the WTRU is (pre-)configured with multiple (e.g., two) Uu RSRP ranges, where Range 1 is used when the WTRU sends a discovery message to become a WTRU-to-network relay (e.g., directly connected to the gNB), and Range 2 is used when the WTRU sends a discovery message to become a WTRU-to-WTRU relay (e.g., the WTRU is not directly connected to the gNB). At step 712, the WTRU determines whether the Uu RSRP is within the first range (e.g., Thres2 < Uu RSRP < Thres1). If the answer is yes, then at step 720, the WTRU sends a discovery message to be used as a WTRU-to-network relay. If the answer is no, then at step 716, the WTRU determines whether the Uu RSRP is within the second range (e.g., Thres3 < Uu RSRP < Thres2). If the answer is yes, then at step 722, the WTRU sends a discovery message to be used as a WTRU-to-WTRU relay. In the embodiment, as shown, for example, at step 718, the WTRU also determines whether to send a discovery message to be used as a WTRU-to-WTRU based on whether it detects a WTRU-to-network relay. If the answer is yes, then at step 722, if the WTRU detects a WTRU-to-network relay, the WTRU sends a discovery message to be used as a WTRU-to-WTRU; otherwise, the WTRU will not send a discovery message.

[0212] In another embodiment, the WTRU determines whether to send discovery based on the SL RSRP of the sidelink channel between the WTRU and the child node and / or the sidelink channel between the WTRU and the parent node. Specifically, if the SL RSRP of the sidelink channel between the WTRU and the child node and / or the sidelink channel between the WTRU and the parent node is greater than a threshold, the WTRU sends a discovery message. In an embodiment, the SL RSRP threshold is (pre-)configured per hop of the sidelink.

[0213] In another embodiment, the WTRU determines whether to send a discovery message based on the distance to the parent / child node and / or the distance to the source / destination node. In an embodiment, the WTRU is (pre) configured to be a relay for a distance range to the parent / child node and / or a distance range to the source / destination node. The WTRU then determines whether to send a discovery message providing a service to a remote WTRU based on the distance between the WTRU and the child / parent node and / or based on the distance between the WTRU and the source / destination node. In an embodiment, if the distance between the WTRU and the source / destination node and / or the distance between the WTRU and the parent / child node is within the (pre) configured range, the WTRU sends a discovery message and transmits information about the source / destination node and / or the parent / child node in an embodiment.

[0214] In another embodiment, the WTRU determines whether to send a discovery message based on the distance to the gNB. Specifically, the WTRU is (pre-)configured with one or more distance ranges to the gNB to determine whether it is allowed to send a discovery message. Each distance range is a function of the number of hops to the gNB, the QoS of the relay service, and / or the QoS of the discovery message. The WTRU then determines whether to send a discovery message based on the distance to the gNB, the number of hops to the gNB, the QoS of the relay service, and / or the QoS of the discovery message.

[0215] In an embodiment, for one QoS of relay service, the WTRU is (pre-)configured for two distance ranges, where a first range is used when the WTRU is a WTRU-to-network relay and a second range is used when the WTRU is a WTRU-to-WTRU relay directly connected to the WTRU-to-network relay. The WTRU then determines whether to send a discovery message based on the distance to the gNB and the number of hops to the gNB (e.g., whether the WTRU is a WTRU-to-network relay or a WTRU-to-WTRU relay directly connected to the WTRU-to-network relay). For example, if the distance to the gNB is within the first range, the WTRU sends a discovery message becoming a WTRU-to-network relay.

[0216] In another embodiment, the WTRU determines whether to send a discovery message based on the coverage status of the WTRU. For example, if the WTRU is out of network coverage, the WTRU sends a discovery message that is a WTRU-to-WTRU relay; however, if the WTRU is within network coverage, the WTRU sends a discovery message that is a WTRU-to-network relay. If the WTRU is (pre-)configured as a WTRU-to-WTRU relay, the WTRU is allowed to send discovery messages if the WTRU is out of network coverage; otherwise, if the WTRU is within network coverage, the WTRU is not allowed to send discovery messages that are a WTRU-to-WTRU relay.

[0217] In another embodiment, an example of which is Figure 8 , the WTRU determines whether to send a discovery message based on the QoS of the relay service. At step 810, the WTRU receives a discovery message from the WTRU to the network relay. At step 812, the WTRU determines whether to send a WTRU to WTRU relay discovery message that is a WTRU to network relay based on the QoS of the relay service indicated in the discovery message. In an implementation scheme, if the QoS of the relay service is within a range, then at step 820, the WTRU determines to send a discovery message; otherwise, at step 814, the WTRU determines not to send a WTRU to WTRU relay discovery message that is a WTRU to network relay. In an implementation scheme, the QoS range is further (pre-)configured based on other parameters such as SL-RSRP, load of the WTRU, etc.

[0218] In another embodiment, the WTRU determines whether to send a discovery message based on an indication from a child / parent node. The WTRU may have an ongoing connection with the child / parent node. The WTRU then receives an indication from the child / parent node to send a discovery message. The indication is transmitted to the WTRU via SCI, MAC CE, or PC5 RRC. The WTRU then triggers the discovery transmission based on the indication from the child / parent node.

[0219] In another embodiment, the WTRU determines whether to send a discovery message based on the connection status to the child / parent node. The WTRU may have an ongoing connection with the child / parent node. The WTRU may then receive an indication from the child / parent node to send a discovery message. The indication may be transmitted to the WTRU via SCI, MAC CE, or PC5 RRC. The WTRU may then trigger the discovery transmission based on the indication from the child / parent node. The discovery message may include information about the child / parent node, such as the ID information of the source / destination node (e.g., WTRU ID, cell ID, or PLMN ID).

[0220] In another embodiment, an example of which is Fig. 9 , the WTRU determines whether to send a discovery message based on the load of the WTRU. In an embodiment, at step 910, the WTRU is (pre)configured with one or more load thresholds, wherein each of the thresholds is associated with a type of relay. The WTRU then determines whether to send a discovery message based on its relay type and its load. In an embodiment, the WTRU is (pre)configured with three load thresholds, wherein a load level between a first threshold (Thresh1) and a second threshold (Thresh 2) is associated with a WTRU to network relay, and a load level between a second threshold (Thresh 2) and a third threshold (Thresh 3) is associated with a WTRU to WTRU relay. At step 912, the WTRU determines whether the load is between the first threshold and the second threshold. If the answer is yes, then at step 920, the WTRU sends a discovery message indicating the availability of being a WTRU to network relay. If the answer is no, then at step 916, the WTRU determines whether the load is between the second threshold and the third threshold. If the answer is yes, then at step 930, the WTRU sends a discovery message indicating the availability of the WTRU to WTRU relay. Fig. 9 Not shown, but in an embodiment, if the load level is above a third threshold, the WTRU does not send a discovery message. In an embodiment, the WTRU is (pre-)configured with two load thresholds. For a load between the first threshold and the second threshold, the WTRU sends a discovery message indicating the availability as a WTRU-network relay, and for a load above the second threshold, the WTRU sends a discovery message indicating the availability as a WTRU-WTRU relay. In an embodiment, the WTRU is (pre-)configured with one load value. For a load below the first threshold, the WTRU sends a discovery message indicating the availability as a WTRU-network relay, and for a load above the first threshold, the WTRU sends a discovery message indicating the availability as a WTRU-WTRU relay.

[0221] In an embodiment, the WTRU determines which conditions to check before discovery transmission based on the coverage state of the WTRU. In an embodiment, the WTRU is (pre-)configured with multiple sets of conditions for performing discovery transmission, each set of conditions being determined based on one or any combination of the coverage state of the WTRU and the Uu RRC state of the WTRU.

[0222] For the coverage state of the WTRU, the WTRU is (pre)configured with two sets of conditions for sending discovery, where a first set of conditions may be required if the WTRU is within the network coverage, and another set of conditions is required when the WTRU is outside the network coverage. The WTRU determines which set of conditions to use for sending discovery messages based on the coverage state of the WTRU. If the WTRU is within the network coverage, the WTRU checks the first set of conditions, and if the WTRU is outside the network coverage, the WTRU checks the second set of conditions. For example, for the scenario within the network coverage, in an implementation scheme, the WTRU needs to check the UuRSRP condition (e.g., the Uu RSRP should be within the (pre)configured range). The WTRU then determines whether to send a discovery message based on the Uu RSRP. However, when the WTRU is outside the network coverage, the WTRU needs to check the distance to the gNB (e.g., the distance to the gNB is within the (pre)configured range). The WTRU then determines whether to send a discovery message based on the distance to the gNB.

[0223] For example, for the Uu RRC state of the WTRU, the WTRU is (pre-)configured with two sets of conditions to check, where the first set of conditions is required if the WTRU is in RRC connected mode, and the second set of conditions is required if the WTRU is in RRC idle / inactive mode. The WTRU then determines which set of conditions to check based on the RRC state of the WTRU.

[0224] In one embodiment, the WTRU is (pre)configured to be a WTRU-to-network or WTRU-to-WTRU relay. The WTRU is (pre)configured with two Uu RSRP ranges, where the first Uu RSRP range is a condition for being a WTRU-to-network relay and the second Uu RSRP range is a condition for being a WTRU-to-WTRU relay. The WTRU first determines whether it can be a WTRU-to-network relay based on the Uu RSRP. Specifically, if the Uu RSRP is within the first Uu RSRP range, the WTRU determines to be a WTRU-to-network relay, and it sends a discovery message to provide WTRU-to-network relay services to other remote WTRUs. Otherwise, if the Uu RSRP is not within the first range, the WTRU determines that it cannot be a WTRU-to-network relay. The WTRU then checks whether the Uu RSRP is within the second range. If the Uu RSRP is not within the second range, the WTRU determines that it cannot be a WTRU-to-network relay or a WTRU-to-WTRU relay. Otherwise, if the Uu RSRP is within the second range, the WTRU determines that it can be a WTRU-to-WTRU relay. In an embodiment, the WTRU performs discovery monitoring to detect the availability of a WTRU-to-network relay. If the WTRU detects a WTRU-to-network relay, the WTRU determines to send a discovery message to a WTRU-to-WTRU relay connected to the WTRU-to-network relay. In an embodiment, the WTRU includes information of the detected WTRU-to-network relay in the discovery message.

[0225] In another exemplary embodiment, the WTRU is (pre-)configured to be a WTRU-to-network or WTRU-to-WTRU relay. The WTRU is (pre-)configured with a Uu RSRP range as a condition to be a WTRU-to-network relay. The WTRU is further (pre-)configured with a distance range to the gNB as a condition to be a WTRU-to-WTRU relay. The WTRU first determines whether it can be a WTRU-to-network relay based on the Uu RSRP. If the Uu RSRP is within the first Uu RSRP range, the WTRU determines to be a WTRU-to-network relay and it sends a discovery message to provide WTRU-to-network relay services to other remote WTRUs. If the WTRU does not meet the conditions to be a WTRU-to-network relay, the WTRU then monitors discovery to detect the availability of a WTRU-to-network relay. The WTRU then receives location information of the source / destination node (e.g., gNB) from the discovery message sent from the WTRU-to-network relay. The WTRU may then determine whether to be a WTRU-to-WTRU relay directly connected to the WTRU-to-network relay based on the distance between the WTRU and the gNB. Specifically, if the distance is within the (pre-)configured range, the WTRU may be a WTRU-to-WTRU relay; otherwise, the WTRU may not be a WTRU-to-network relay. The WTRU may then send a discovery message and may include information about the gNB and the WTRU-to-network relay in the discovery message to provide relay services to the remote WTRU.

[0226] In an embodiment, the WTRU determines the information to be included in the discovery message. In an embodiment, the WTRU includes one or any combination of the following information in the discovery message:

[0227] 1) A collection of remote WTRUs. In an embodiment, a WTRU (e.g., a relay WTRU) detects a discovery request message from one or more remote WTRUs. The WTRU then determines to generate a discovery message to forward the remote WTRU information for another relay (e.g., a WTRU to a network relay) or a gNB.

[0228] 2) Set of child / parent nodes. In an embodiment, for Model A discovery, the WTRU indicates the set of parent nodes in the discovery message. For Model B, the WTRU indicates the set of remote WTRUs in the discovery message. For other models, the WTRU indicates the set of both parent and child nodes in the discovery message.

[0229] 3) One or more paths to the gNB. In an embodiment, if the WTRU is a WTRU-to-WTRU relay, the WTRU indicates one or more paths to the gNB in ​​the discovery message. The path includes information about the gNB and the WTRU-to-network relay.

[0230] 4) Connection status of the WTRU and / or other WTRUs in the path. In an embodiment, the WTRU indicates whether it has an ongoing path to the source (e.g., gNB) and information about the path (e.g., WTRU to network ID and cell ID).

[0231] 5) Uu RRC status of the WTRU and / or other WTRUs in the path.

[0232] 6) Number of hops to reach gNB.

[0233] 7) Number of hops to reach the source / destination node.

[0234] 8) Location of gNB.

[0235] 9)The location of the WTRU.

[0236] 10) Discovery Model. In an embodiment, the WTRU indicates in the discovery message whether the WTRU is using Model A, Model B, or a combination of Model A and Model B. In an embodiment, for the combination of Model A and Model B, the WTRU also includes information about both child nodes and parent nodes in the discovery message.

[0237] 11) QoS of the relay service required. In an embodiment, this may include hop-by-hop QoS and / or end-to-end QoS.

[0238] 12) QoS of discovery messages.

[0239] In an embodiment, the WTRU determines what information to include in the discovery message. In an embodiment, the WTRU determines what information to include in the discovery message based on one or any combination of the following:

[0240] 1) The type of relay (e.g., WTRU-to-network relay or WTRU-to-WTRU relay). In an embodiment, if the WTRU is a WTRU-to-WTRU relay, the WTRU includes information related to the WTRU-to-network relay in the discovery message. If the WTRU is a WTRU-to-network relay, the WTRU includes information about the gNB (e.g., cell ID, location of the gNB, etc.) in the discovery message.

[0241] 2) Whether the WTRU has an ongoing connection with the source / destination node. In an embodiment, if the WTRU has an ongoing connection with the source / destination node, the WTRU indicates such information in the discovery message. In an embodiment, the WTRU indicates the path to the source / destination in the discovery message. For example, if the WTRU has an ongoing connection with a WTRU-to-network relay, the WTRU indicates the ID of the WTRU-to-network relay in the discovery message.

[0242] 3) Whether the WTRU has an ongoing connection with the parent / child node. In an embodiment, if the WTRU has an ongoing connection with the child / parent node, the WTRU indicates such information in the discovery message. In an embodiment, the WTRU indicates the path to the source / destination in the discovery message.

[0243] 4) Discovery Model. In an embodiment, for discovery model A, the WTRU includes information about the gNB and the parent node. For discovery model B, the WTRU includes information about the child nodes. For other discovery models (e.g., a combination of model A and model B), the WTRU includes information about both the child nodes and the parent node.

[0244] In an embodiment, the WTRU determines whether to include a child / parent node in a discovery message. In an embodiment, the WTRU determines whether to include a child / parent node in a discovery message based on one or any combination of the following:

[0245] 1) Maximum number of child / parent nodes to include in a discovery message. In an embodiment, the WTRU is (pre-)configured to include a maximum number of child / parent nodes in a discovery message. The WTRU then determines which child / destination node to include in the discovery message based on the highest SL-RSRP until the number of child / destination nodes included in the discovery message reaches the maximum number of child / parent nodes.

[0246] 2) SL-RSRP between the child / parent node and the WTRU. In an embodiment, the WTRU is (pre-)configured with a range of SL-RSRPs (e.g., minimum and / or maximum SL-RSRPs) in the sidelink channel between the WTRU and the child / parent node that includes the child / parent node in the discovery message. The WTRU may then determine whether to include the child / parent node in the discovery message based on the sidelink channel between the WTRU and the child / parent node. In an embodiment, if the SL RSRP between the child / parent node and the WTRU is within the range, the WTRU includes the child / parent node in the discovery message; otherwise, the WTRU does not include the child / parent node in the discovery message.

[0247] 3) The distance between the child / parent node and the WTRU. In an embodiment, the WTRU is (previously)

[0248] The WTRU is configured with a distance range (e.g., minimum and / or maximum distance) between the child / parent node and the WTRU that includes the child / parent node in the discovery message. The WTRU then

[0249] The WTRU determines whether to include the child / parent node in the discovery message based on the distance between the child / parent node and the WTRU. If the distance between the child / parent node and the WTRU is within the range, the WTRU includes the child / parent node in the discovery message; otherwise, if the distance is outside the (pre-)configured distance range, the WTRU does not include the child / parent node in the discovery message.

[0250] 4) QoS of relay service required. In an embodiment, the WTRU determines whether to include a child / parent node in a discovery message based on the QoS requirements of the relay service. In an embodiment, the WTRU is (pre-)configured with a QoS range that determines whether to include a child / parent node in a discovery message. The QoS requirements of the relay service are transmitted in the discovery message. The WTRU then determines whether to include a child / parent node in a discovery message based on the QoS requirements of the relay service.

[0251] In an embodiment, if the QoS requirement of the relay service is within the (pre-)configured required QoS, the WTRU includes the child / parent node in the discovery message; otherwise, the WTRU does not include the child / parent node in the discovery message.

[0252] In an embodiment, the WTRU determines the QoS of the relay service. In an embodiment, the WTRU determines the hop-by-hop QoS of the relay service. The WTRU determines the QoS of the relay service in the next hop based on the required QoS in the current hop, the maximum number of hops for the relay service, and / or the end-to-end QoS. In an embodiment, the WTRU is a WTRU-to-WTRU relay that is directly connected to the WTRU-to-network relay and the remote WTRU. The WTRU receives a discovery message for Model B discovery from the remote WTRU. The WTRU then determines the required QoS of the relay service in the hop between the WTRU itself and the WTRU to the network relay based on the end-to-end required QoS, the required QoS in the hop between the WTRU and the remote WTRU, and the 3-hop relay service. In an embodiment, the WTRU may split the end-to-end delay equally between each hop.

[0253] In an implementation scheme, an example of which is Fig.10As shown in step 1010, a first WTRU (WTRU1) receives a discovery message from a second WTRU (WTRU2), the discovery message including the number of hops from the second WTRU to a base station (BS), the location of the BS, and the quality of service (QoS) parameters of the second WTRU. At step 1012, based on the location of the BS, the distance from the first WTRU to the BS is determined. In an embodiment, the determined distance to the BS is within a preconfigured allowed distance range, wherein the preconfigured allowed distance range is associated with the number of hops from the first WTRU; at step 1014, based on the QoS parameters of the second WTRU, the relay load of the first WTRU, and the sidelink (SL) reference signal received power (SL RSRP) of the received discovery message, the QoS parameters of the first WTRU for the relay service provided by the first WTRU are determined. At step 1016, WTRU1 determines whether the QoS parameters of the first WTRU and the determined distance to the BS are within the preconfigured limits. If the answer is yes, then at step 1018, WTRU1 sends a discovery message to the third WTRU (WTRU3), which is a WTRU-WTRU discovery message. If the answer is no, then at step 1020, WTRU1 does not send a discovery message. In another embodiment, the discovery message includes some or all of the following: a relay type of the first WTRU, a number of hops from the first WTRU to the BS, QoS parameters of the first WTRU, and a location of the BS. In another embodiment, the QoS parameters of the first WTRU include some or all of the following: priority information associated with the relay service, delay information associated with the relay service, and reliability information associated with the relay service.

[0254] Embodiments for relay selection and reselection are described herein.

[0255] In an embodiment, a WTRU (e.g., a remote WTRU) determines a delay in sending a packet. Specifically, the WTRU receives a timestamp in a packet, i.e., the time when the packet was originally sent. The WTRU then determines a delay associated with a packet based on the time at which it decoded the message and the timestamp indicated in the packet. In an embodiment, the WTRU indicates the timestamp in the packet. The source / destination node then determines a delay associated with the packet.

[0256] In an embodiment, the WTRU determines the quality of the path based on one or any combination of: the number of hops in the path; the minimum RSRP (SL-RSRP or Uu RSRP) of all hops; and / or the average RSRP of all hops.

[0257] In an embodiment, the WTRU performs the path shortening process by performing one or any combination of the following: monitoring discovery messages; sending discovery messages; triggering relay (re)selection; and / or performing connection establishment with a newly selected node.

[0258] In an embodiment, the WTRU triggers the path shortening process based on one or any combination of the following events:

[0259] 1) In an embodiment, the WTRU receives an indication from a parent / child node to trigger the path shortening process.

[0260] For example, a WTRU receives an indication from its child / parent node to perform a path shortening procedure.

[0261] The WTRU then initiates a path shortening procedure to shorten the path to the source / destination or find an alternative source / destination.

[0262] 2) In an embodiment, the WTRU decodes a discovery message from another relay that has fewer or equal hops to the source / destination than the current path. For example, the WTRU monitors discovery messages from other nodes. If the WTRU detects a relay that has fewer or equal hops to the source / destination than the current path, the WTRU then determines to perform a path shortening procedure.

[0263] 3) In an embodiment, the SL-RSRP between the WTRU and the source / destination node becomes less than a threshold.

[0264] 4) In an embodiment, the load of the WTRU becomes greater / less than a threshold.

[0265] 5) In an embodiment, the delay of the packet becomes greater than a threshold.

[0266] Although features and elements are described above in specific combinations, it will be understood by those of ordinary skill in the art that each feature or element may be used alone or in any combination with other features and elements. In addition, the methods described herein may be implemented in a computer program, software, or firmware incorporated in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted via a wired or wireless connection) and computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, read-only memory (ROM), random access memory (RAM), registers, cache memory, semiconductor memory devices, magnetic media (such as built-in hard disks and removable disks), magneto-optical media, and optical media (such as CD-ROM disks and digital versatile disks (DVDs)). A processor associated with the software may be used to implement a radio frequency transceiver for a WTRU, UE, terminal, base station, RNC, or any host computer.

Claims

1. A method for use in a first wireless transmit / receive unit (WTRU), the method comprising: receiving a first transmission from a first remote WTRU; determining whether a reference signal received power (RSRP) level of the first received transmission is above a predetermined threshold; receiving a second transmission from a second remote WTRU; determining whether a reference signal received power (RSRP) level of the second received transmission is above the predetermined threshold; sending a discovery message identifying the first remote WTRU and the second remote WTRU on the condition that the RSRP level of the first received transmission and the RSRP level of the second received transmission are both above the predetermined threshold, and Data is received and sent between the WTRUs identified in the discovery message.

2. The method of claim 1 , wherein the predetermined threshold is provided to the WTRU by a base station.

3. The method of claim 1, wherein the predetermined threshold is a side link RSRP (SL-RSRP) threshold.

4. The method of claim 1 , wherein the discovery message identifies the WTRU as a WTRU-to-WTRU relay.

5. The method of claim 1, wherein the sending and receiving of data between the WTRUs identified in the discovery message is performed on a sidelink channel.

6. A wireless transmit / receive unit (WTRU), the WTRU being configured to: receiving a first transmission from a first remote WTRU; determining whether a reference signal received power (RSRP) level of the first received transmission is above a predetermined threshold; receiving a second transmission from a second remote WTRU; determining whether a reference signal received power (RSRP) level of the second received transmission is above the predetermined threshold; sending a discovery message identifying the first remote WTRU and the second remote WTRU on the condition that the RSRP level of the first received transmission and the RSRP level of the second received transmission are both above the predetermined threshold, and Data is received and sent between the WTRUs identified in the discovery message.

7. The WTRU of claim 6, wherein the predetermined threshold is provided to the WTRU by a base station.

8. The WTRU of claim 6, wherein the predetermined threshold is a side link RSRP (SL-RSRP) threshold.

9. The WTRU of claim 6, wherein the discovery message identifies the WTRU as a WTRU-to-WTRU relay.

10. The WTRU of claim 6, wherein the transmission and reception of data between the WTRUs identified in the discovery message is performed on a sidelink channel.

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