Method for supporting multi-hop user equipment to network relay and relay user equipment

Abstract

The invention discloses a method for supporting multi-hop user equipment to network relay and relay user equipment. A maximum hop count specific for the relay service code is provided by the network to the second relay user equipment. Further, the second relay user equipment receives a first user equipment-to-network relay discovery notification message from the first relay user equipment, where the first user equipment-to-network relay discovery notification message includes a user information identification of the first relay user equipment, a relay service code, and a first accumulated hop count. If the sum of the first accumulated hop count and 1 is smaller than or equal to the maximum hop count, the second relay user equipment further transmits or broadcasts a second user equipment-to-network relay discovery notification message, and the second user equipment-to-network relay discovery notification message comprises a user information identifier, a relay service code and the second accumulated hop count of the second relay user equipment.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 528,328, filed on July 21, 2023, the entire disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates generally to wireless communication networks, and more particularly, to a method and apparatus for supporting multi-hop UE-to-network relay in a wireless communication system. Background Art

[0004] As the demand for transmitting large amounts of data to and from mobile communication devices grows rapidly, traditional mobile voice communication networks have evolved into networks with Internet Protocol (IP) packet communications, which can provide IP-based voice, multimedia, multicast, and on-demand communication services to users of mobile communication devices.

[0005] An exemplary network structure is an Evolved Universal Terrestrial Radio Access Network (E-UTRAN). The E-UTRAN system can provide high data throughput to enable the above-mentioned IP-bearing voice and multimedia services. Currently, the 3rd Generation Partnership Project (3GPP) standards organization is discussing new next-generation (e.g., 5G) radio technologies. Therefore, changes to the current body of 3GPP standards are currently being submitted and considered to evolve and finalize the 3GPP standards. Summary of the invention

[0006] A method and apparatus for supporting multi-hop UE to network (U2N) relay is disclosed. In one embodiment, a maximum hop count specific to a relay service code (RSC) is provided by the network to a second relay UE. In addition, the second relay UE receives a first U2N relay discovery notification message from a first relay UE, wherein the first U2N relay discovery notification message includes a user information identifier (ID) of the first relay UE, an RSC, and a first cumulative hop count. If the first cumulative hop count plus 1 is less than or equal to the maximum hop count, the second relay UE also transmits or broadcasts a second U2N relay discovery notification message, wherein the second user equipment to network relay discovery notification message includes the user information ID of the second relay UE, the RSC, and the second cumulative hop count. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 A diagram illustrating a wireless communication system according to an exemplary embodiment;

[0008] Figure 2 is a block diagram of a transmitter system (also referred to as an access network) and a receiver system (also referred to as a user equipment or UE) according to an exemplary embodiment;

[0009] Figure 3 is a functional block diagram of a communication system according to an exemplary embodiment;

[0010] Figure 4 According to an exemplary embodiment Figure 3 Functional block diagram of the program code;

[0011] Figure 5 For 3GPP TS23.304V18.2.0 Figure 4 .2.7.1-1 reappearance;

[0012] Figure 6 For 3GPP TS23.304V18.2.0 Figure 4 .2.7.2-1 reappearance;

[0013] Figure 7 For 3GPP TS23.304V18.2.0 Figure 6 .3.2.1-1 reappearance;

[0014] Figure 8 For 3GPP TS23.304V18.2.0 Figure 6 .3.2.1-2 reappearance;

[0015] Fig. 9 For 3GPP TS23.304V18.2.0 Figure 6 .3.2.3.2-1 reappearance;

[0016] Fig.10 For 3GPP TS23.304V18.2.0 Figure 6 .3.2.3.3-1 reappearance;

[0017] Fig.11 For 3GPP TS23.304V18.2.0 Figure 6 .4.3.1-1 reappearance;

[0018] Fig.12 For 3GPP TS23.304V18.2.0 Figure 6 .5.1.1-1 reappearance;

[0019] Fig.13For 3GPP TS23.304V18.2.0 Figure 6 .5.2.2-1 reappearance;

[0020] Fig.14 For 3GPP TS 38.300 V17.5.0 Fig.16 .12.5.1-1 reappearance;

[0021] Fig.15 An exemplary 3-hop UE to network relay is shown according to an exemplary embodiment;

[0022] Fig.16 illustrates multi-hop UE-to-network relay discovery according to an exemplary embodiment;

[0023] Fig.17 illustrates a multi-route UE-to-network relay according to an exemplary embodiment;

[0024] Fig.18 is a flow chart according to an exemplary embodiment. DETAILED DESCRIPTION

[0025] The exemplary wireless communication systems and devices described below adopt wireless communication systems that support broadcast services. Wireless communication systems are widely deployed to provide various types of communications such as voice, data, etc. These systems can be based on code division multiple access (CDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), 3GPP Long Term Evolution (LTE) wireless access, 3GPP Long Term Evolution Advanced (LTE-A or Advanced LTE), 3GPP2 Ultra Mobile Broadband (UMB), WiMax, 3GPP New Radio (NR) or some other modulation technology.

[0026] Specifically, the exemplary wireless communication systems and devices described below may be designed to support one or more standards, such as those provided by an alliance named “3rd Generation Partnership Project” referred to herein as 3GPP, including: TS23.304V18.2.0, “Proximity based Service (ProSe) in 5G System (5GS) (Release 18)”; TS24.554V18.1.0, “Proximity Service (ProSe) in 5G System (5GS) Protocol Aspects; Stage 3 (Release 18)”; and TS22.261V19.3.0, “Service Requirements for 5G System; Stage 1 (Release 19)”. The standards and documents listed above are expressly incorporated herein by reference in their entirety.

[0027] Figure 1 A multiple access wireless communication system according to an embodiment of the present invention is shown. An access network 100 (AN) includes multiple antenna groups, one group includes 104 and 106, another group includes 108 and 110, and an additional group includes 112 and 114. Figure 1 , only two antennas are shown for each antenna group, however, each antenna group may utilize more or fewer antennas. Access terminal 116 (AT) communicates with antennas 112 and 114, where antennas 112 and 114 transmit information to access terminal 116 via forward link 120 and receive information from access terminal 116 via reverse link 118. Access terminal (AT) 122 communicates with antennas 106 and 108, where antennas 106 and 108 transmit information to access terminal (AT) 122 via forward link 126 and receive information from access terminal (AT) 122 via reverse link 124. In a frequency division duplex (FDD) system, communication links 118, 120, 124, and 126 may use different frequencies for communication. For example, forward link 120 may use a different frequency than reverse link 118.

[0028] Each antenna group and / or the area in which the antenna group is designed to communicate is often referred to as a sector of the access network. In an embodiment, the antenna groups are each designed to communicate with access terminals in a sector of the area covered by the access network 100.

[0029] In communicating via forward links 120 and 126, the transmit antennas of access network 100 may utilize beamforming in order to improve the signal-to-noise ratio of the forward links for the different access terminals 116 and 122. Also, an access network using beamforming to transmit to access terminals randomly dispersed throughout its coverage area may cause less interference to access terminals in neighboring cells than if the access network transmitted to all of its access terminals via a single antenna.

[0030] An access network (AN) may be a fixed station or base station for communicating with a terminal, and may also be referred to as an access point, a Node B, a base station, an enhanced base station, an evolved Node B (eNB), a network node, a network, or some other terminology. An access terminal (AT) may also be referred to as a user equipment (UE), a wireless communication device, a terminal, an access terminal, or some other terminology.

[0031] Figure 2 A simplified block diagram of an embodiment of a transmitter system 210 (also referred to as an access network) and a receiver system 250 (also referred to as an access terminal (AT) or user equipment (UE)) in a multiple input multiple output (MIMO) system 200. At the transmitter system 210, traffic data for a number of data streams is provided from a data source 212 to a transmit (TX) data processor 214.

[0032] In one embodiment, each data stream is transmitted via a respective transmit antenna.TX data processor 214 formats, codes, and interleaves the traffic data for each data stream based on a particular coding scheme selected for that data stream to provide coded data.

[0033] The coded data for each data stream may be multiplexed with pilot data using OFDM techniques. The pilot data is typically a known data pattern that is processed in a known manner and may be used at the receiver system to estimate the channel response. The multiplexed pilot and coded data for each data stream are then modulated (i.e., symbol mapped) based on a specific modulation scheme selected for the data stream (e.g., Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK), Multiple Phase Shift Keying (M-PSK), or Quadrature Amplitude Modulation (M-QAM)) to provide modulation symbols. The data rate, coding, and modulation for each data stream may be determined by instructions executed by the processor 230.

[0034] The modulation symbols for all data streams are then provided to a TX MIMO processor 220, which may further process the modulation symbols (e.g., for OFDM). T The modulation symbol stream is provided to N T transmitters (TMTR) 222a through 222t. In certain embodiments, TX MIMO processor 220 applies beamforming weights to the symbols of the data streams and to the antenna from which the symbol is being transmitted.

[0035] Each transmitter 222 receives and processes a respective symbol stream to provide one or more analog signals, and further conditions (eg, amplifies, filters, and upconverts) the analog signals to provide a modulated signal suitable for transmission over the MIMO channel. T The antennas 224a to 224t transmit N signals from transmitters 222a to 222t. T a modulated signal.

[0036] At the receiver system 250, N R The transmitted modulated signals are received by each antenna 252a through 252r and the received signal from each antenna 252 is provided to a respective receiver (RCVR) 254a through 254r. Each receiver 254 conditions (e.g., filters, amplifies, and downconverts) a respective received signal, digitizes the conditioned signal to obtain samples, and further processes the samples to provide a corresponding “received” symbol stream.

[0037] The RX data processor 260 then receives and processes the N R The N received by the receiver 254 R symbol streams to provide N T The RX data processor 260 then demodulates, deinterleaves, and decodes each detected symbol stream to recover the traffic data for the data stream. The processing by the RX data processor 260 is complementary to the processing performed by the TX MIMO processor 220 and the TX data processor 214 at the transmitter system 210.

[0038] Processor 270 periodically determines which pre-coding matrix to use (discussed below). Processor 270 formulates a reverse link message comprising a matrix index portion and a rank value portion.

[0039] The reverse link message may include various types of information about the communication link and / or the received data stream. The reverse link message is then processed by the TX data processor 238, which also receives traffic data for a number of data streams from the data source 236, modulated by the modulator 280, conditioned by the transmitters 254a to 254r, and transmitted back to the transmitter system 210.

[0040] At the transmitter system 210, the modulated signals from the receiver system 250 are received by the antenna 224, conditioned by the receiver 222, demodulated by the demodulator 240, and processed by the RX data processor 242 to extract the reverse link message transmitted by the receiver system 250. The processor 230 then determines which precoding matrix to use to determine the beamforming weights and then processes the extracted message.

[0041] Steering Figure 3 , this figure shows an alternative simplified functional block diagram of a communication device according to one embodiment of the present invention. Figure 3 As shown, the communication device 300 in the wireless communication system can be used to implement Figure 1 UE (or AT) 116 and 122 in or Figure 1 The base station (or AN) 100 in the wireless communication system is preferably an NR system. The communication device 300 may include an input device 302, an output device 304, a control circuit 306, a central processing unit (CPU) 308, a memory 310, a program code 312 and a transceiver 314. The control circuit 306 executes the program code 312 in the memory 310 through the CPU 308, thereby controlling the operation of the communication device 300. The communication device 300 can receive signals input by the user through the input device 302 (such as a keyboard or a keypad), and can output images and sounds through the output device 304 (such as a display or a speaker). The transceiver 314 is used to receive and transmit wireless signals, pass the received signals to the control circuit 306, and wirelessly output the signals generated by the control circuit 306. The communication device 300 in the wireless communication system can also be used to implement Figure 1 AN 100 in.

[0042] Figure 4 According to one embodiment of the present invention, Figure 3 4. In this embodiment, program code 312 includes application layer 400, layer 3 portion 402, and layer 2 portion 404, and is coupled to layer 1 portion 406. Layer 3 portion 402 typically performs radio resource control. Layer 2 portion 404 typically performs link control. Layer 1 portion 406 typically performs physical connectivity.

[0043] 3GPP TS 23.304 specifies the procedures related to UE to network relay as follows:

[0044] 4.2.7 5G ProSe UE to Network Relay Reference Architecture

[0045] 4.2.7.1 5G ProSe layer 3 UE to network relay reference architecture

[0046] Down Figure 4 .2.7.1-1 shows a high-level reference architecture for 5G ProSe layer 3 UE to network relay. In this figure, the 5G ProSe layer 3 UE to network relay can be in the HPLMN or VPLMN.

[0047] [3GPP TS 23.304 V18.2.0 titled "Reference architecture for 5G ProSe layer 3 UE to network relay" Figure 4 .2.7.1-1 is reproduced as Figure 5 ]

[0048] […]

[0049] 4.2.7.2 5G ProSe layer 2 UE to network relay reference architecture

[0050] Figure 4 .2.7.2-1 shows the 5G ProSe Layer 2 UE to Network Relay reference architecture. The 5G ProSe Layer 2 Remote UE and the 5G ProSe Layer 2 UE to Network Relay may be served by the same or different PLMNs. If the serving PLMNs of the 5G ProSe Layer 2 Remote UE and the 5G ProSe Layer 2 UE to Network Relay are different, the NG-RAN is shared by the serving PLMN, see 5G MOCN architecture in Section 5.18 of TS 23.501 [4].

[0051] [3GPP TS23.304 V18.2.0 titled "5G ProSe layer 2 UE to network relay reference architecture" Figure 4 .2.7.2-1

[0052] Reproduced as Figure 6 ]

[0053] NOTE 1: The Uu between 5G ProSe Layer 2 Remote UE and NG-RAN consists of RRC, SDAP and PDCP.

[0054] Note 2: 5G ProSe Layer 2 Remote UE and 5G ProSe Layer 2 UE to Network Relay are served by the same NG-RAN. The core network entities (e.g., AMF, SMF, UPF) serving 5G ProSe Layer 2 Remote UE and 5G ProSe Layer 2 UE to Network Relay may be the same or different.

[0055] […]

[0056] 5.1.4.1 Policy / Parameter Provisioning for 5G ProSe UE to Network Relay

[0057] The following information is provisioned in the UE to support the UE acting as a 5G ProSe UE to network relay:

[0058] 1) Authorization policy for acting as a 5G ProSe Layer 3 and / or Layer 2 UE to Network Relay when “served by NG-RAN”:

[0059] -The PLMN for which the UE is authorized to relay traffic for 5G ProSe Layer 3 and / or Layer 2 remote UEs.

[0060] The authorization of the UE to act as a 5G ProSe UE to network relay also authorizes the use of 5G ProSe UE to network relay discovery with Model A and Model B.

[0061] NOTE 1: The choice of discovery model or whether to perform both models simultaneously depends on the UE and application implementation.

[0062] 2) ProSe relay discovery strategy / parameters for 5G ProSe UE to network relay:

[0063] - Contains parameters that enable the UE to perform 5G ProSe UE-to-Network Relay Discovery when provided by the PCF or provisioned in the ME or configured in the UICC:

[0064] - 5G ProSe UE to network relay discovery parameters (User Information ID, Relay Service Code, UE to network relay layer indicator per RSC, optional control plane security indicator per RSC). The UE to network relay layer indicator indicates whether the associated RSC provides 5G ProSe layer 2 or layer 3 UE to network relay service. If the control plane security indicator is provided for an RSC, the control plane based security procedures as described in clause 5.1.4.3.2 are performed for UE to network relay communications of the RSC, otherwise if the control plane security indicator is not provided for an RSC, the user plane based security procedures as described in clause 5.1.4.3.3 are performed for the RSC. An RSC dedicated to emergency services may also be provisioned.

[0065] - A preset destination layer 2 ID for sending relay discovery notification and relay discovery additional information messages and receiving relay discovery solicitation messages;

[0066] - For 5G ProSe layer 3 UE to network relay, the PDU session parameters (PDU session type, DNN, SSC mode, S-NSSAI, access type preference) to be used for relay services per ProSe relay service code;

[0067] - Contains security related content for 5G ProSe UE to network relay, see TS 33.503

[29] .

[0068] NOTE 2: 5G ProSe relay discovery policies / parameters may be provided from the ProSe application server to the 5G ProSe UE to the network relay, except for the security parameters in item number 2).

[0069] 3) For 5G ProSe layer 3 UE to network relay, QoS mapping:

[0070] - Each QoS map entry contains:

[0071] -Mapping between 5QI value and PQI value;

[0072] -PQIPDB adjustment factor for PC5 communications for 5G ProSe layer 3 UE to network relay operation;

[0073] - An optional relay service code is associated with the QoS map entry.

[0074] 4) For a 5G ProSe Layer 3 UE to network relay that relays Ethernet or unstructured traffic from a 5G ProSe Layer 3 remote UE using an IP-type PDU session:

[0075] -Map the ProSe service to the ProSe application server address information (consisting of IP address / FQDN and transport layer port number).

[0076] 5) Parameters for broadcasting warning messages:

[0077] -Configured destination layer 2 ID;

[0078] - PC5 QoS parameters defined in clause 5.6.1;

[0079] - Based on the configured NR Tx attribute set as specified in clause 5.1.3.1.

[0080] NOTE 3: Whether all UEs across PLMNs in a particular area use one or more common destination Layer 2 IDs for common warning notification relay depends on inter-operator alignment and network configuration.

[0081] 6) Validity time indicates the expiration time of the policy / parameters used for 5G ProSe UE to network relay discovery and communication.

[0082] The following information is provisioned in the UE to support the UE to assume the role of 5G ProSe remote UE, thereby enabling the use of 5G ProSe UE to network relay:

[0083] 1) Authorization policy for UE-to-network relay using 5G ProSe Layer 3 and / or Layer 2:

[0084] -For 5G ProSe Layer 3 Remote UE, indicates whether the UE is authorized to use 5G ProSe Layer 3 UE-to-Network Relay.

[0085] -For 5G ProSe Layer 2 Remote UE, indicates the PLMN in which the UE is authorized to use 5G ProSe Layer 2 UE to Network Relay.

[0086] The authorization of the UE to act as a 5G ProSe Remote UE also authorizes the use of 5G ProSe UE to Network Relay Discovery with Model A and Model B.

[0087] NOTE 4: The choice of discovery model or whether to perform both models simultaneously depends on the UE and application implementation.

[0088] 2) Strategies / parameters for 5G ProSe UE to network relay discovery:

[0089] - Enables the UE to include parameters for 5G ProSe Relay discovery when provided by the PCF or provisioned in the ME or configured in the UICC and for connecting to the 5G ProSe UE to Network Relay after discovery:

[0090] - 5G ProSe UE to network relay discovery parameters (User Information ID, Relay Service Code, UE to network relay layer indicator for each RSC, optional control plane security indicator for each RSC). The UE to network relay layer indicator indicates whether the associated RSC provides 5G ProSe layer 2 or layer 3 UE to network relay service. If the control plane security indicator is provided for an RSC, the control plane based security procedures as described in clause 5.1.4.3.2 are performed for UE to network relay communications of the RSC, otherwise if the control plane security indicator is not provided for the RSC, the user plane based security procedures as described in clause 5.1.4.3.3 are performed for the RSC. An RSC dedicated to emergency services may be provisioned to enable support for emergency services for UE to network relay.

[0091] - A preset destination layer 2 ID for sending relay discovery solicitation messages and receiving relay discovery notification and relay discovery additional information messages;

[0092] -For 5G ProSe Layer 3 UE to network relay, the PDU session parameters (PDU session type, DNN, SSC mode, S-NSSAI, access type preference) for relay services, or the indication of N3IWF access, for each ProSe relay service code if N3IWF access is not used;

[0093] - For 5G ProSe Layer 3 UE-to-network relay, optionally the ProSe application traffic descriptor (as defined in TS 23.503 [9]) for the relay traffic per ProSe relay service code;

[0094] - Contains security related content for 5G ProSe UE to network relay, see TS 33.503

[29] .

[0095] 3) Policy / parameters for N3IWF selection for 5G ProSe Layer 3 Remote UE:

[0096] -N3IWF identifier configuration (FQDN or IP address) in HPLMN for 5G ProSe Layer 3 Remote UE.

[0097] -5G ProSe Layer 3 UE to Network Relay Access Node Selection Information - A prioritized list of PLMNs for N3IWF selection. It also indicates whether the selection of N3IWF in PLMN should be based on Tracking Area Identification FQDN or Operator Identifier FQDN.

[0098] NOTE 5: 5G ProSe relay discovery policies / parameters may be provided from the ProSe application server to the 5G ProSe remote UE, except for the security parameters in item number 2).

[0099] 4) Parameters for receiving warning messages:

[0100] -Configured destination layer 2 ID;

[0101] - PC5 QoS parameters defined in clause 5.6.1;

[0102] - Based on the configured NR Tx attribute set as specified in clause 5.1.3.1.

[0103] NOTE 6: Whether all UEs across PLMNs in a particular area use one or more common destination Layer 2 IDs for common warning notification relay depends on inter-operator alignment and network configuration.

[0104] 5) Validity time indicates the expiration time of the policy / parameters used for 5G ProSe UE to network relay discovery and communication.

[0105] The following information is provisioned in the UE to support the UE assuming the role of 5G ProSe UE to Network Relay, and the following information is provided in the UE to support the UE assuming the role of 5G ProSe Remote UE, thereby enabling the use of 5G ProSe UE to Network Relay:

[0106] 1) Radio parameters for 5G ProSe UE to Network Relay Discovery when the UE is not “served by NG-RAN”:

[0107] -Contains radio parameters for NR PC5 with a geographical area, and an indication of whether the radio parameters are "operator managed" or "non-operator managed". The UE uses the radio parameters to perform 5G ProSe direct discovery over the PC5 reference point when "not served by NG-RAN" only if the UE can reliably locate itself in the corresponding geographical area. Otherwise, the UE is not authorized to transmit.

[0108] - Preset PC5 DRX configuration (see TS 38.331

[16] ).

[0109] 2) Radio parameters for 5G ProSe relay UE to network relay communications when the UE is not “served by NG-RAN”:

[0110] -Contains radio parameters for NR PC5 with a geographical area, and an indication of whether the radio parameters are "operator managed" or "non-operator managed". The UE uses the radio parameters to perform 5G ProSe direct communication over the PC5 reference point when "not served by NG-RAN" only if the UE can reliably locate itself in the corresponding geographical area. Otherwise, the UE is not authorized to transmit.

[0111] NOTE 7: The validity period of these radio parameters is the same as the validity period of the policies / parameters listed above for 5G ProSe UE to Network Relay or 5G ProSe Remote UE.

[0112] 3) Privacy-related policies / parameters:

[0113] - A privacy timer value indicating the duration after which the UE should change each source layer 2 ID allocated by the UE itself when privacy is required.

[0114] […]

[0115] 6.3.2 5G ProSe direct discovery procedure over PC5 reference point

[0116] 6.3.2.1 Overview

[0117] The PC5 communication channel is used to carry discovery messages on the PC5, and the discovery messages on the PC5 are distinguished from other PC5 messages by the AS layer.

[0118] Supports both Model A and Model B discovery as defined in TS 23.303 [3]:

[0119] - Model A uses a single discovery protocol message (Notify).

[0120] - Model B uses two discovery protocol messages (solicit and response).

[0121] Figure 6 The procedure for 5G ProSe direct discovery with Model A is described in .3.2.1-1.

[0122] [3GPP TS 23.304 V18.2.0 titled "5G ProSe direct discovery with Model A" Figure 6 .3.2.1-1 Reproduced as Figure 7 ]

[0123] 1. Notify the UE to send a notification message. The notification message may include the type of discovery message, ProSe application code or ProSe restricted code, relay_Indication, security protection element, and [metadata information]. The application layer metadata information may be included in the notification message as metadata.

[0124] The destination Layer 2 ID and source Layer 2 ID used to send the notification message are specified in clauses 5.8.1.2 and 5.8.1.3.

[0125] If the 5G ProSe inter-UE relay can broadcast its user information ID during 5G ProSe inter-UE discovery, the notification UE includes relay_Indication.

[0126] The listening UE determines the destination Layer 2 ID for signaling reception. The destination Layer 2 ID is configured with the UE as specified in clause 5.8.2.1.

[0127] Figure 6 The procedure for 5G ProSe direct discovery with Model B is described in .3.2.1-2.

[0128] [3GPP TS TS23.304V18.2.0 titled "5G ProSe Direct Discovery with Model B" Figure 6 .3.2.1-2

[0129] Reproduce as Figure 8 ]

[0130] 1. The discoverer UE sends a request message. The request message may include the type of discovery message, ProSe query code, relay_Indication, and security protection element.

[0131] The destination Layer 2 ID and source Layer 2 ID used to send the solicitation message are specified in clauses 5.8.1.2 and 5.8.1.3.

[0132] How the discoverer UE determines the destination Layer 2 ID for signalling reception is specified in clause 5.8.1.2.

[0133] If the 5G ProSe inter-UE relay can broadcast its user information ID during 5G ProSe inter-UE discovery, the discoverer UE includes relay_Indication.

[0134] 2. The discoverer UE that matches the solicitation message responds to the discoverer UE using a response message. The response message may include the type of discovery message, ProSe response code, relay_Indication, security protection element, and [metadata information]. The application layer metadata information may be included in the response message as metadata.

[0135] If the 5G ProSe inter-UE relay can broadcast its user information ID during 5G ProSe inter-UE discovery, the discovered UE includes relay_Indication.

[0136] The source Layer 2ID used to send the response message is specified in clause 5.8.1.3. The destination Layer 2ID is set to the source Layer 2ID of the received solicitation message.

[0137] NOTE: Details of security protection elements are specified in TS 33.503

[29] .

[0138] […]

[0139] 6.3.2.3 5G ProSe UE to Network Relay Discovery

[0140] 6.3.2.3.1 Overview

[0141] 5G ProSe UE to Network Relay Discovery is applicable to both 5G ProSe Layer 3 and Layer 2 UE to Network Relay Discovery for public safety purposes and commercial services. To perform 5G ProSe UE to Network Relay Discovery, the 5G ProSe Remote UE and the 5G ProSe UE to Network Relay are pre-configured or provisioned with relevant information as described in clause 5.1.

[0142] In 5G ProSe UE to network relay discovery, the UE uses pre-configured or provisioned information for the relay discovery procedure as defined in clause 5.1.4.1.

[0143] The Relay Service Code (RSC) is used for 5G ProSe UE to Network Relay discovery to indicate the connectivity service provided by the 5G ProSe UE to Network Relay to the 5G ProSe Remote UE. The RSC (including one RSC dedicated to emergency services) is configured on the 5G ProSe UE to Network Relay and the 5G ProSe Remote UE as defined in clause 5.1.4. Based on the policy specified in clause 5.1.4, the 5G ProSe UE to Network Relay and the 5G ProSe Remote UE know whether the RSC is providing 5G ProSe Layer 2 or Layer 3 UE to Network Relay service and whether the RSC is used for emergency services. A 5G ProSe UE to Network Relay supporting multiple RSCs may use multiple discovery messages to advertise the RSCs with one RSC per discovery message.

[0144] NOTE: Clause 5.4.4 specifies when the 5G ProSe UE to network relay can broadcast an emergency RSC.

[0145] Additional information not used directly for discovery may also be announced using the PC5-D protocol stack in a single or separate discovery messages of type "Relay Discovery Additional Information" as defined in section 5.8.3.1.

[0146] 6.3.2.3.2 Procedure for 5G ProSe UE to Network Relay Discovery with Model A

[0147] Figure 6 .Described in 3.2.3.2-1 is the procedure for 5G ProSe UE to network relay discovery with Model A.

[0148] [3GPP TS 23.304 V18.2.0 titled "5G ProSe UE to Network Relay Discovery with Model A" Figure 6 .3.2.3.2-1 Reproduced as Fig. 9 ]

[0149] 1.5G ProSe UE to Network Relay sends a UE to Network Relay Discovery Notification message. The UE to Network Relay Discovery Notification message contains the type of discovery message, notifier information and RSC, and is sent using source layer 2 ID and destination layer 2 ID as described in clause 5.8.3.

[0150] For 5G ProSe Layer 3 UE-to-network relay, the 5G ProSe Layer 3 UE-to-network relay shall only include the RSC in the UE-to-network relay discovery notification when the S-NSSAI associated with the RSC belongs to the allowed NSSAI of the UE-to-network relay.

[0151] The 5G ProSe Remote UE (1 to 3) determines the destination Layer 2 ID for signaling reception. As specified in clause 5.1.4.1, the destination Layer 2 ID is configured with the UE.

[0152] The 5G ProSe remote UEs (1 to 3) listen to the notification message and the 5G ProSe UE to network RSC corresponding to the service to be served.

[0153] Optionally, the 5G ProSe UE to Network Relay may also send a Relay Discovery Additional Information message as defined in clause 6.5.1.3. The parameters contained in this message as well as the source layer 2 ID and destination layer 2 ID used to send and receive messages are described in clause 5.8.3.

[0154] The 5G ProSe remote UE selects a 5G ProSe UE to network relay based on the information received in step 1.

[0155] NOTE: The access stratum information used for 5G ProSe UE to network relay selection is specified in the RAN specification.

[0156] 6.3.2.3.3 Procedure for 5G ProSe UE to Network Relay Discovery with Model B

[0157] Figure 6 .Described in 3.2.3.3-1 is the procedure for 5G ProSe UE to network relay discovery with Model B.

[0158] [3GPP TS 23.304 V18.2.0 titled "5G ProSe UE to Network Relay Discovery with Model B" Figure 6 .3.2.3.3-1 Reproduced as Fig.10 ]

[0159] 1. The 5G ProSe Remote UE sends a 5G ProSe UE to Network Relay Discovery Solicitation message. The 5G ProSe UE to Network Discovery Solicitation message contains the type of discovery message, discoverer information, RSC and optional target message, and is sent using source layer 2 ID and destination layer 2 ID as described in clause 5.8.3. The 5G ProSe Remote UE discovering the 5G ProSe UE to Network Relay sends the solicitation message with the RSC associated with the desired connectivity service. The RSC is based on the policy / parameters specified in clause 5.1.4.1.

[0160] The way in which the 5G ProSe UE to Network Relay (1 to 3) determines the destination Layer 2 ID for signaling reception is specified in clause 5.8.3. As specified in clause 5.1.4.1, the destination Layer 2 ID is configured with the UE.

[0161] 2. The 5G ProSe UE to Network Relay (1 and 2) matching the value of the RSC and target information (if present) contained in the solicitation message responds to the 5G ProSe Remote UE with a UE to Network Relay Discovery Response message. The 5G ProSe UE to Network Relay Discovery Response message contains the type of discovery message, discoverer information and RSC, and is sent using the source Layer 2 ID and destination Layer 2 ID as described in clause 5.8.3.

[0162] For the 5G ProSe Layer 3 UE-to-network Relay, the 5G ProSe UE-to-network Relay shall only respond to a matching RSC in the UE-to-network Relay Discovery Solicitation message when the S-NSSAI associated with the RSC belongs to the allowed NSSAIs of the 5G ProSe UE-to-network Relay.

[0163] The 5G ProSe remote UE selects a 5G ProSe UE to network relay based on the information received in step 2.

[0164] […]

[0165] 6.4.3.1 Layer 2 link establishment over PC5 reference point

[0166] To perform unicast mode of ProSe direct communication over PC5 reference point, the UE is configured with relevant information as described in clause 5.1.3.

[0167] Figure 6 .4.3.1-1 shows the Layer 2 link establishment procedure for unicast mode of ProSe direct communication over PC5 reference point.

[0168] [3GPP TS 23.304 V18.2.0 entitled "Layer 2 Link Establishment Procedure" Figure 6 .4.3.1-1 Reproduced as Fig.11 ]

[0169] 1. The UE determines the destination Layer 2 ID for signalling reception for PC5 unicast link establishment as specified in clause 5.8.2.4.

[0170] 2. The ProSe application layer in UE-1 provides application information for PC5 unicast communication. The application information includes ProSe service information and the application layer ID of the UE. The application information may include the application layer ID of the target UE.

[0171] The ProSe application layer in UE-1 may provide the ProSe application requirements for this unicast communication.UE-1 determines the PC5 QoS parameters and PFI as specified in clause 5.6.1.

[0172] If UE-1 decides to reuse the existing PC5 unicast link as specified in clause 5.3.4, the UE triggers the Layer 2 Link Modification procedure as specified in clause 6.4.3.4.

[0173] 3. UE-1 sends a direct communication request message to initiate the unicast layer 2 link establishment procedure. The direct communication request message contains:

[0174] - Source user information: the application layer ID of the originating UE (ie, the application layer ID of UE-1).

[0175] - If the ProSe application layer provides the application layer ID of the target UE in step 2, the following information is included:

[0176] - Target user information: Application layer ID of the target UE (ie, the application layer ID of UE-2).

[0177] -ProSe service information: Information about the ProSe identifier requesting Layer 2 link establishment.

[0178] - Security information: information used to establish security.

[0179] NOTE 1 Security information and the necessary protection of source user information and destination user information are defined by SA WG3.

[0180] Determine the source layer 2 ID and destination layer 2 ID used to send the direct communication request message, as specified in clauses 5.8.2.1 and 5.8.2.4. The destination layer 2 ID can be a broadcast or unicast layer 2 ID. When a unicast layer 2 ID is used, the target user information shall be included in the direct communication request message.

[0181] UE-1 transmits a direct communication request message through PC5 which is broadcast or unicast using the source layer 2 ID and the destination layer 2 ID.

[0182] The default PC5 DRX configuration may be used to transmit and receive this message (see TS 38.300

[12] ).

[0183] 4. Establish security for UE-1 as follows:

[0184] 4a. If the target user information is included in the direct communication request message, the target UE, ie, UE-2, responds by establishing security with UE-1.

[0185] 4b. If the target user information is not included in the direct communication request message, the UE interested in using the notified ProSe service over the PC5 unicast link with UE-1 responds by establishing security with UE-1.

[0186] NOTE 2 Signalling for security procedures is defined by SAWG3.

[0187] When security protection is enabled, UE-1 sends the following information to the target UE:

[0188] - If using IP communication, then:

[0189] -IP address configuration: For IP communication, this link requires an IP address configuration, and the IP address configuration indicates one of the following values:

[0190] - "DHCPv4 server", if only IPv4 address allocation mechanism is supported by the initiating UE, i.e. acting as a DHCPv4 server; or

[0191] - "IPv6 router", if only the IPv6 address allocation mechanism is supported by the originating UE, i.e. acting as an IPv6 router; or

[0192] - "DHCPv4 server and IPv6 router", if both IPv4 and IPv6 address allocation mechanisms are supported by the initiating UE; or

[0193] - "Address allocation not supported" if both IPv4 and IPv6 address allocation mechanisms are not supported by the originating UE.

[0194] - Link-local IPv6 address: If UE-1 does not support the IPv6 IP address allocation mechanism, i.e. the IP address configuration indicates "address allocation not supported", a link-local IPv6 address is formed locally based on RFC 4862

[17] .

[0195] - QoS Information: Information about PC5 QoS flows. For each PC5 QoS flow, the PFI and corresponding PC5 QoS parameters (ie, PQI and conditionally other parameters such as MFBR / GFBR) and the associated ProSe identifier.

[0196] -Optional PC5 QoS rules.

[0197] Determine the source Layer 2 ID for the security establishment procedure as specified in clauses 5.8.2.1 and 5.8.2.4. The destination Layer 2 ID is set to the source Layer 2 ID of the received direct communication request message.

[0198] Upon receiving the Security Setup Procedure message, UE-1 obtains the Layer 2 ID of the peer UE for future communications for signaling and data traffic for this unicast link.

[0199] 5. The target UE, which has successfully established security with UE-1, sends a direct communication acceptance message to UE-1:

[0200] 5a. (Layer 2 link establishment towards UE) If the target user information is contained in the direct communication request message, the target UE (ie, UE-2) responds with a direct communication accept message if the application layer ID for UE-2 matches.

[0201] 5b. (Layer 2 Link Establishment for ProSe Services) If the direct communication request message does not contain target user information, the UE interested in using the notified ProSe service (in Figure 6 .UE-2 and UE-4 in 4.3.1-1) respond to the request by sending a direct communication accept message.

[0202] The direct communication acceptance message contains:

[0203] -Source user information: the application layer ID of the UE that sends the direct communication acceptance message.

[0204] - QoS Information: Information about PC5 QoS flows. For each PC5 QoS flow, the PFI requested by UE-1 and the corresponding PC5 QoS parameters (ie PQI and conditionally other parameters such as MFBR / GFBR) and optionally the associated ProSe identifier.

[0205] -Optional PC5 QoS rules.

[0206] - If using IP communication, then:

[0207] -IP address configuration: For IP communication, this link requires an IP address configuration, and the IP address configuration indicates one of the following values:

[0208] - "DHCPv4 Server", if only IPv4 address allocation mechanism is supported by the target UE, i.e. act as a DHCPv4 server; or

[0209] - "IPv6 router", if the IPv6 address allocation mechanism is supported by the target UE, i.e. act as an IPv6 router; or

[0210] - "DHCPv4 server and IPv6 router", if both IPv4 and IPv6 address allocation mechanisms are supported by the target UE; or

[0211] - "Address allocation not supported" if both IPv4 and IPv6 address allocation mechanisms are not supported by the target UE.

[0212] - Link-local IPv6 address: If the target UE does not support the IPv6 IP address allocation mechanism, i.e. the IP address configuration indicates "address allocation not supported", and UE-1 includes a link-local IPv6 address in the Direct Communication Request message, a link-local IPv6 address is formed locally based on RFC4862

[17] . The target UE shall include a non-conflicting link-local IPv6 address.

[0213] If both UEs (ie, the initiating UE and the target UE) are selected to use link-local IPv6 addresses, they shall disable dual address detection as defined in RFC4862

[17] .

[0214] NOTE 3: When the initiating UE or the target UE indicates support for IPv6 routing, the corresponding address configuration procedure shall be performed after the Layer 2 link is established and the link-local IPv6 address shall be ignored.

[0215] The ProSe layer of the UE that establishes the PC5 unicast link passes the PC5 link identifier and PC5 unicast link related information allocated for the unicast link downward to the AS layer. The PC5 unicast link related information includes layer 2ID information (i.e., source layer 2ID and destination layer 2ID). This enables the AS layer to save the PC5 link identifier and PC5 unicast link related information.

[0216] Two UEs may negotiate the PC5 DRX configuration in the AS layer, and the PC5 DRX parameter value may be configured according to a pair of source / destination layer 2 IDs in the AS layer.

[0217] 6. ProSe data is transmitted over the established unicast link as follows:

[0218] The PC5 link identifier and PFI are provided to the AS layer together with the ProSe data.

[0219] Additionally, layer 2 ID information (ie, source layer 2 ID and destination layer 2 ID) is optionally provided to the AS layer.

[0220] NOTE 4: Providing the Layer 2 ID information to the AS layer is up to the UE implementation.

[0221] UE-1 sends ProSe data using a source Layer 2 ID (ie, the Layer 2 ID of UE-1 for this unicast link) and a destination Layer 2 ID (ie, the Layer 2 ID of the peer UE for this unicast link).

[0222] NOTE 5: The PC5 unicast link is bidirectional, so UE-1's peer UE can send ProSe data to UE-1 via the unicast link with UE-1.

[0223] […]

[0224] 6.4.3.6 Layer 2 Link Management over PC5 Reference Point for 5G ProSe UE to Network Relay

[0225] The Layer 2 link procedure over the PC5 reference point for unicast mode 5G ProSe direct communication as described from clause 6.4.3.1 to clause 6.4.3.5 may be used for the PC5 reference point between a 5G ProSe Remote UE and a 5G ProSe UE to Network Relay, with the following differences and clarifications:

[0226] -The Layer 2 Link Modification procedure is applicable to ProSe communication from 5G ProSe Layer 3 UE to network relay, and other procedures are applicable to ProSe communication from 5G ProSe Layer 2 UE to network relay and ProSe communication from 5G ProSe Layer 3 UE to network relay.

[0227] - UE-oriented layer 2 link establishment is used with UE-1 representing a 5G ProSe remote UE and UE-2 representing a 5G ProSe UE to network relay. For other procedures, UE-1 represents a 5G ProSe remote UE and UE-2 represents a 5G ProSe UE to network relay, or UE-1 represents a 5G ProSe UE to network relay and UE-2 represents a 5G ProSe remote UE. That is, the layer 2 link establishment is initiated by the 5G ProSe remote UE, while other procedures can be initiated by the 5G ProSe remote UE or by the 5G ProSe UE to network relay.

[0228] For Layer 2 link establishment towards the UE as described in clause 6.4.3.1,

[0229] - In step 1, the 5G ProSe Remote UE determines the destination Layer 2 ID for PC5 unicast link establishment based on the unicast source Layer 2 ID of the selected 5G ProSe UE-to-Network Relay (as specified in clause 5.8.3) during UE-to-Network Relay discovery as specified in clause 6.3.2.3.

[0230] - In step 2, the 5G ProSe Remote UE (UE-1) determines the relay service code to be used. The relay service code to be used is selected from the received relay service code during UE to network relay discovery as specified in clause 6.3.2.3.

[0231] - In step 3, the 5G ProSe remote UE (UE-1) sends a unicast direct communication request message to the selected 5G ProSe UE to network relay. The destination layer 2 ID used to send the direct communication request message shall be the unicast layer 2 ID as determined in step 1. The direct communication request message contains:

[0232] - Source User Information: The identity of the remote UE requesting the relay operation (ie, User Information ID).

[0233] NOTE 1: Details of the additional identity / identities of the remote UE to be included during Layer 2 link establishment are specified in TS 33.503

[29] .

[0234] - Target User Information: The identity of the UE-to-Network Relay (i.e., User Information ID) provided to the 5G ProSe Remote UE during the UE-to-Network Relay discovery procedure.

[0235] - Relay Service Code: Indicates the connectivity service provided by the 5G ProSe UE to network relay requested by the 5G ProSe remote UE (which may be non-emergency or emergency).

[0236] - Security information: information used to establish security.

[0237] NOTE 2: For PC5 link establishment for emergency RSC, it will be determined whether and how PC5 security is to be used as part of the SAWG3 alignment.

[0238] - In step 4 and step 5, if the identity of the 5G ProSe UE to network relay matches the target user information and the relay service code is one of the relay service codes included during the UE to network relay discovery as specified in clause 6.3.2.3, then step 4a and step 5a are performed. The source user information in the direct communication accept message is the identity of the UE to network relay (i.e., the user information ID). In the case of a 5G ProSe layer 2 UE to network relay, the remote UE does not send the IP address configuration, link-local IPv6 address and QoS information to the 5G ProSe layer 2 UE to network relay, and the direct communication accept message does not include the IP address configuration, link-local IPv6 address and QoS information. In the case of a 5G ProSe layer 3 UE to network relay, the direct communication accept message does not include the IP address configuration indicating the value "address allocation not supported".

[0239] - In case of 5G ProSe layer 2 UE to network relay, step 6 is not performed.

[0240] For link identifier updates as described in clause 6.4.3.2,

[0241] - The application layer ID is replaced by the user information ID.

[0242] - In case of 5G ProSe Layer 2 UE to network relay, the changed identifier does not contain the IP address / prefix.

[0243] For the Layer 2 link release described in clause 6.4.3.3,

[0244] - In step 1, if the Layer 2 Link Release procedure is initiated by the 5G ProSe UE to Network Relay, the Disconnect Request message may indicate that the 5G ProSe UE to Network Relay is temporarily unavailable, as described in clause 5.12.

[0245] NOTE 3: The form of the temporary unavailability indication will be determined by Phase 3.

[0246] - If the service authorization for acting as a 5G ProSe Remote UE or a 5G ProSe UE to Network Relay is revoked, the 5G ProSe Remote UE or the 5G ProSe UE to Network Relay shall initiate the release of the Layer 2 links affected by the revoked authorization.

[0247] - A 5G ProSe Layer 2 remote UE or a 5G ProSe Layer 2 UE to network relay initiates the release of the Layer 2 link after receiving a trigger from its AS layer to release the PC5 unicast link as specified in TS 38.331

[16] .

[0248] NOTE 4: The timing of initiating Layer 2 link release depends on the UE implementation.

[0249] If the existing unicast link is established with a different relay service code or without a relay service code, the 5G ProSe remote UE and the 5G ProSe UE to network relay should set up separate PC5 unicast links.

[0250] NOTE 5: A single PC5 unicast link is established between the 5G ProSe Layer 2 UE to the Network Relay and the 5G ProSe Layer 2 Remote UE, as specified in TS 38.300

[12] , to support the PDU session of the 5G ProSe Layer 2 Remote UE.

[0251] Each PC5 unicast link for 5G ProSe UE to network relay is associated with a unicast link profile, which contains:

[0252] - User Information ID and Layer 2 ID of 5G ProSe Remote UE; and

[0253] - User Information ID and Layer 2 ID from 5G ProSe UE to network relay; and

[0254] - Relay service code; and

[0255] - Network layer protocols and information about PC5 QoS flows in case of 5G ProSe layer 3 UE to network relay.

[0256] The unicast link attribute set shall be updated accordingly after a layer 2 link modification or a layer 2 link identifier update.

[0257] […]

[0258] 6.5.1 5G ProSe Communication via 5G ProSe Layer 3 UE to Network Relay

[0259] 6.5.1.0 Overview

[0260] 5G ProSe communications via 5G ProSe Layer 3 UE to Network Relay may be performed with or without involvement of N3 IWF for non-emergency services and for emergency services as specified in clause 5.4.4.

[0261] 6.5.1.1 5G ProSe communication via 5G ProSe layer 3 UE to network relay without N3IWF

[0262] 5G ProSe Layer 3 UE to Network Relay registers with the network (if not already registered). 5G ProSe Layer 3 UE to Network Relay establishes a PDU Session or modifies an existing PDU Session in order to provide relay services towards 5G ProSe Layer 3 Remote UEs. PDU Sessions supporting 5G ProSe Layer 3 UE to Network Relay shall only be used for 5G ProSe Layer 3 Remote UE relay services.

[0263] The PLMN serving the 5G ProSe Layer 3 UE to the network relay and the PLMN where the 5G ProSe Layer 3 remote UE is registered can be the same PLMN or two different PLMNs.

[0264] [3GPP TS 23.304 V18.2.0 entitled "5G ProSe communication via 5G ProSe layer 3 UE to network relay without N3 IWF" Figure 6 .5.1.1-1 is reproduced as Fig.12 ]

[0265] 1. Service authorization and provisioning are performed as described in clause 6.2 for 5G ProSe Layer 3 UE to Network Relay (step 1a) and 5G ProSe Layer 3 Remote UE (step 1b).

[0266] 2.5G ProSe Layer 3 UE to Network Relay can establish a PDU session for relaying. In the case of IPv6, the 5G ProSe Layer 3 UE to Network Relay obtains the IPv6 prefix from the network via the prefix delegation function as defined in TS 23.501 [4].

[0267] NOTE 1: The 5G ProSe Layer 3 UE to Network Relay may establish a PDU Session for any Relay Service Code it supports before establishing a connection with the 5G ProSe Layer 3 Remote UE.

[0268] 3. The 5G ProSe Layer 3 Remote UE performs discovery of the 5G ProSe Layer 3 UE to the Network Relay as described in clause 6.3.2.3. As part of the discovery procedure, the 5G ProSe Layer 3 Remote UE learns about the connectivity services provided by the 5G ProSe Layer 3 UE to the Network Relay.

[0269] 4. The 5G ProSe Layer 3 Remote UE selects the 5G ProSe Layer 3 UE to Network Relay and establishes a connection for unicast mode communication as described in clause 6.4.3.6. If there is no PDU session associated with the relay service code or a new PDU session for relay is required, the 5G ProSe Layer 3 UE to Network Relay initiates a new PDU session establishment procedure for relay before completing the PC5 connection establishment.

[0270] When the 5G ProSe Layer 3 remote UE sends a direct communication request message containing a dedicated emergency RSC, the 5G ProSe Layer 3 UE to network relay sets up an emergency PDU session for relaying emergency services without establishing an emergency PDU session in step 2.

[0271] NOTE 2: If emergency services of the 5G ProSe layer 3 UE to network relay itself are in progress, how to handle the conflict situation is specified in clause 5.4.4.3.

[0272] The network decides that the PDU session to be established is for relayed traffic, and then generates 5G ProSe Layer 3 UE to Network Relay QoS rules and QoS flow level QoS parameters with relay considerations, and may initiate the setup of the QoS flow, as specified in clause 5.6.2.1. The remote UE may also initiate the setup of the QoS flow by providing PC5 QoS information and (optionally) PC5 QoS rules to the 5G ProSe Layer 3 UE to Network Relay during the connection setup, according to the procedure specified in clause 5.6.2.1.

[0273] 5G ProSe Layer 3 UE to Network Relay determines the PDU Session Type for relay as specified in clause 5.4.1.1.

[0274] Depending on the PDU session type used for relaying, the 5G ProSe layer 3 UE to network relay performs the relay function at the corresponding layer as follows:

[0275] -When IP type PDU session is used for IP traffic over PC5 reference point, the 5G ProSe Layer 3 UE to Network Relay acts as an IP router. For IPv4, the 5G ProSe Layer 3 UE to Network Relay performs IPv4 NAT between the IPv4 address assigned to the 5G ProSe Layer 3 remote UE and the IPv4 address assigned to the PDU session for relayed traffic.

[0276] -When Ethernet type PDU session is used for Ethernet traffic over PC5 reference point, the 5G ProSe Layer 3 UE-to-network relay acts as an Ethernet switch.

[0277] - When an unstructured type PDU session is used for unstructured traffic over the PC5 reference point, the 5G ProSe Layer 3 UE to network relay performs traffic relay based on the mapping between the PC5 link identifier and the PDU session ID and the mapping between the PFI for the PC5 layer 2 link and the QFI for the PDU session. These mappings are created when the unstructured type PDU session is established for the 5G ProSe layer 3 remote UE.

[0278] - When IP type PDU session is used for Ethernet or unstructured traffic over PC5 reference point, 5G ProSe layer 3 UE to network relay uses IP tunneling. For this IP tunneling, 5G ProSe layer 3 UE to network relay locally allocates IP address / prefix for 5G ProSe layer 3 remote UE and is used over Uu reference point to encapsulate and decapsulate uplink and downlink traffic for 5G ProSe layer 3 remote UE. Tunneled traffic over Uu reference point is transported over PC5 reference point as Ethernet or unstructured traffic.

[0279] 5. For IP PDU session type and IP traffic over PC5 reference point, the 5G ProSe Layer 3 remote UE is allocated an IPv6 prefix or IPv4 address (including NAT case) as defined in clause 5.5.1.3.

[0280] 6.5G ProSe Layer 3 Remote UE may provide PC5 QoS information and PC5 QoS rules to the 5G ProSe Layer 3 UE to Network Relay using Layer 2 Link Modification procedures as specified in clause 6.4.3.4. The 5G ProSe Layer 3 UE to Network Relay generates packet filters for use on the Uu interface based on the received PC5 QoS information and QoS rules as described in clause 5.6.2.1 and may perform UE requested PDU session modification as defined in clause 4.3.3 of TS23.502 [5] to set up a new QoS flow or bind a service to an existing QoS flow.

[0281] Uplink and downlink relaying can start from this point. For downlink traffic forwarding, PC5 QoS rules are used to map downlink packets to PC5 QoS flows. For uplink traffic forwarding, 5G QoS rules are used to map uplink packets to Uu QoS flows.

[0282] 7.5G ProSe Layer 3 UE to Network Relay shall send a Remote UE Report (Remote User ID, Remote UE Information) message to the SMF for the PDU Session associated with the relay. The Remote User ID as defined in TS 33.503

[29] is the identification of the 5G ProSe Layer 3 Remote UE user that was successfully connected in step 4. The Remote UE Information is used to assist in identifying the 5G ProSe Layer 3 Remote UE in the 5GC. For IP PDU Session Type, the Remote UE Information is the Remote UE IP Information. For Ethernet PDU Session Type, the Remote UE Information is the Remote UE MAC address detected by the 5G ProSe Layer 3 UE to Network Relay. For Unstructured PDU Session Type, the Remote UE Information is not included. For this PDU Session associated with the relay, the SMF stores the Remote User ID and related Remote UE Information in the SM context of the 5G ProSe Layer 3 UE to Network Relay.

[0283] Remote UE reporting is an N1 SM NAS message sent to the AMF along with the PDU Session ID and then delivered to the SMF.

[0284] NOTE 3 Privacy protection of remote user IDs is specified in TS 33.503

[29] .

[0285] For IP information, the following principles apply:

[0286] - For IPv4, the 5G ProSe Layer 3 UE to Network Relay shall report the TCP / UDP port range assigned to each 5G ProSe Layer 3 remote UE (along with the remote user ID);

[0287] -For IPv6, the 5G ProSe Layer 3 UE to Network Relay shall report the IPv6 prefix assigned to the individual 5G ProSe Layer 3 Remote UE (along with the Remote User ID).

[0288] If a PDU Session for relaying is released by the UE-to-network relay or the network as described in clause 4.3.4 of TS 23.502 [5], the UE-to-network relay shall initiate the release of the Layer 2 link associated with the released PDU Session using the procedure defined in clause 6.4.3.3.

[0289] If the service authorization for acting as a 5G ProSe Layer 3 UE to Network Relay in the serving PLMN is revoked, the PDU session for the relay shall be released as described in section 4.3.4 of TS 23.502 [5] (e.g., by 5G ProSe Layer 3 UE to Network Relay).

[0290] When the 5G ProSe Layer 3 Remote UE is disconnected from the 5G ProSe Layer 3 UE to Network Relay (e.g. after an explicit Layer 2 link release or based on the absence of keep-alive messages on PC5), the 5G ProSe Layer 3 UE to Network Relay shall send a Remote UE Report message to inform the SMF that the 5G ProSe Layer 3 Remote UE has left.

[0291] NOTE 4: In order for the SMF to have 5G ProSe Layer 3 remote UE information, the 5G ProSe Layer 3 UE to the HPLMN and VPLMN where the network relay is authorized to operate needs to support the transmission of 5G ProSe Layer 3 remote UE related parameters when the SMF is in the HPLMN.

[0292] How the 5G ProSe Layer 3 UE to Network Relay releases the PDU session for the relay or removes the QoS flow for the relay when the 5G ProSe Layer 3 remote UE is disconnected from the 5G ProSe Layer 3 UE to Network Relay depends on the 5G ProSe Layer 3 UE to Network Relay implementation.

[0293] 6.5.2 5G ProSe Communication via 5G ProSe Layer 2 UE to Network Relay

[0294] […]

[0295] 6.5.2.2 Connection Establishment

[0296] [3GPP TS 23.304 V18.2.0 titled "Connection establishment for 5G ProSe layer 2 UE to network relay" Figure 6 .5.2.2-1 is reproduced as Fig.13 ]

[0297] 0. If within coverage, the 5G ProSe Layer 2 Remote UE and the 5G ProSe Layer 2 UE to Network Relay may independently perform initial registration with the network according to the registration procedure in TS 23.502 [5].

[0298] 1. If in coverage, the 5G ProSe Layer 2 Remote UE and the 5G ProSe Layer 2 UE to Network Relay independently obtain service authorization for 5G ProSe Layer 2 UE to Network Relay operation from the network. Service authorization and parameter provisioning for 5G ProSe Layer 2 UE to Network Relay operation are performed for the 5G ProSe Layer 2 UE to Network Relay and the 5G ProSe Layer 2 Remote UE as specified in clause 5.1.4.

[0299] If the 5G ProSe Layer 2 Remote UE is “not served by NG-RAN”, the preconfigured parameters are used and the serving authorization and parameters may be updated after step 6.

[0300] If the 5G ProSe Layer 2 Remote UE has not performed initial registration, the 5G ProSe Layer 2 Remote UE may perform initial registration in step 6.

[0301] 2.5G ProSe Layer 2 Remote UE and 5G ProSe Layer 2 UE to Network Relay perform 5G ProSe UE to Network Relay discovery and selection as specified in clause 6.3.2.3.

[0302] The 3.5G ProSe Layer 2 Remote UE initiates a one-to-one communication connection with the selected 5G ProSe Layer 2 UE to the Network Relay through PC5 using the procedure as described in clause 6.4.3.

[0303] 4. The 5G ProSe Layer 2 Remote UE establishes an RRC connection with the same NG-RAN serving the selected 5G ProSe Layer 2 UE to Network Relay specified in TS 38.300

[12] . The 5G ProSe Layer 2 Remote UE sets the RRC establishment cause as defined in TS 38.331

[16] .

[0304] 5. During step 4, if the 5G ProSe Layer 2 UE to Network Relay is in CM_IDLE state and receives a trigger from the AS layer to enter the CM-CONNECTED state due to the AS layer connection of the remote UE set up with NG-RAN, the 5G ProSe Layer 2 UE to Network Relay performs the service request procedure in clause 4.2.3.2 of TS 23.502 [5].

[0305] 6. The 5G ProSe Layer 2 Remote UE sends a NAS message to the serving AMF. The NAS message is encapsulated in a Uu RRC message sent to the 5G ProSe Layer 2 UE to Network Relay via PC5, and the 5G ProSe Layer 2 UE to Network Relay forwards the Uu RRC message to the NG-RAN specified in TS 38.300

[12] . The NG-RAN selects the serving AMF of the 5G ProSe Layer 2 Remote UE and forwards the NAS message to this AMF.

[0306] If the 5G ProSe Layer 2 Remote UE has not performed an initial registration, the NAS message is an Initial Registration message. Otherwise, the NAS message is either a Service Request message or a Mobility or Periodic Registration message, as specified in TS 38.300

[12] , taking into account the TAI or PC5-RRC message in the RRC container received from the 5G ProSe Layer 2 UE to the Network Relay during Relay Discovery (see clause 5.8.3.3).

[0307] 7.5G ProSe Layer 2 Remote UE may trigger the PDU Session Establishment procedure as defined in clause 4.3.2.2 of TS 23.502 [5].

[0308] 8. Data is transferred between the 5G ProSe Layer 2 Remote UE and the UPF via the 5G ProSe Layer 2 UE to Network Relay and NG-RAN. The 5G ProSe Layer 2 UE to Network Relay forwards all data messages between the 5G ProSe Layer 2 Remote UE and the NG-RAN as specified in TS 38.300

[12] .

[0309] 3GPP TS 38.300 specifies the procedures related to UE to network relay as follows:

[0310] 16.12 Sidelink Relay

[0311] 16.12.1 Overview

[0312] Sidelink relay is introduced to support 5G ProSe UE to Network Relay (U2N Relay) functionality (specified in TS23.304

[48] ) to provide connectivity to the network for U2N remote UEs. Both L2 and L3 U2N relay architectures are supported. The L3 U2N relay architecture is transparent to the serving NG-RAN of the U2N relay UE, except for controlling the sidelink resources. The detailed architecture and procedures for L3 U2N relay can be found in TS23.304

[48] .

[0313] A U2N relay UE should be in RRC_CONNECTED to perform relay of unicast data.

[0314] For L2 U2N relay operation, the following RRC state combinations are supported:

[0315] - Both the L2 U2N relay UE and the L2 U2N remote UE should be in RRC_CONNECTED to perform transmission / reception of relayed unicast data; and

[0316] - The L2 U2N relay UE may be in RRC_IDLE, RRC_INACTIVE or RRC_CONNECTED as long as all L2 U2N remote UEs connected to the L2 U2N relay UE are in RRC_INACTIVE or RRC_IDLE.

[0317] A single unicast link is established between one L2 U2N relay UE and one L2 U2N remote UE. Traffic from the NG-RAN to the L2 U2N remote UE via a given L2 U2N relay UE and traffic from the L2 U2N relay UE should be separated in different Uu RLC channels.

[0318] For L2 U2N relay, the L2 U2N remote UE may only be configured to use resource allocation mode 2 (as specified in 5.7.2 and 16.9.3.1) for relaying data.

[0319] […]

[0320] 16.12.3 Relay Discovery

[0321] Model A and Model B discovery models as defined in TS 23.304

[48] are supported for U2N relay discovery. The protocol stack for discovery is shown in Fig.16 .12.3-1.

[0322] […]

[0323] The U2N remote UE may perform relay discovery message transmission (i.e., as specified in TS 23.304

[48] ) and may listen to the sidelink of relay discovery messages while in RRC_IDLE, RRC_INACTIVE, or RRC_CONNECTED. The network may broadcast or configure, via dedicated RRC signaling, a Uu RSRP threshold that the U2N remote UE uses to determine whether it may transmit a relay discovery message to the U2N relay UE.

[0324] A U2N relay UE may perform relay discovery message transmission (i.e., as specified in TS 23.304

[48] ) and may listen to the sidelink for relay discovery messages while in RRC_IDLE, RRC_INACTIVE, or RRC_CONNECTED. The network may broadcast or configure, via dedicated RRC signaling, a maximum Uu RSRP threshold, a minimum Uu RSRP threshold, or both, which the U2N relay UE uses to determine whether it may transmit a relay discovery message to a U2N remote UE.

[0325] The network may provide relay discovery configuration using broadcast or dedicated signaling. In addition, U2N remote UEs and L3 U2N relay UEs may use pre-configuration for relay discovery.

[0326] Resource pools for NR side link communications can be used for relay discovery or the network can configure resource pools dedicated to relay discovery. Resource pools dedicated to relay discovery can be configured simultaneously with resource pools used for NR side link communications in system information, dedicated signaling, and / or pre-configuration. Whether dedicated resource pools for relay discovery are configured is based on the network implementation plan. If resource pools dedicated to relay discovery are configured, only those resource pools dedicated to relay discovery are applied to relay discovery. If only resource pools for NR side link communications are configured, all configured resource pools can be used for relay discovery and NR side link communications.

[0327] For a U2N remote UE that has been connected to the network by a U2N relay UE (including both in-coverage and out-of-coverage situations), only resource allocation mode 2 is used for relay discovery message transmission.

[0328] For in-coverage U2N relay UEs, and for both in-coverage and out-of-coverage U2N remote UEs, the NR sidelink resource allocation principle is applied for relay discovery messaging.

[0329] The sidelink power control for transmission of relay discovery messages is the same as the sidelink power control used for NR sidelink communication.

[0330] Ciphering or integrity protection in the PDCP layer shall not be used for the Relay Discovery Message.

[0331] U2N remote UE and U2N relay UE can determine whether the gNB supports relay discovery, non-relay discovery, or both based on SIB12.

[0332] 16.12.4 Relay Selection / Reselection

[0333] The U2N remote UE performs radio measurements at the PC5 interface and uses them together with the higher layer criteria as specified in TS 23.304

[48] for U2N relay selection and reselection. When there is no unicast PC5 connection between the U2N relay UE and the U2N remote UE, the U2N remote UE uses SD-RSRP measurements to evaluate whether the PC5 link quality for the U2N relay UE meets the relay selection criteria.

[0334] For relay reselection, when there is data transmission from the U2N relay UE to the U2N remote UE, the U2N remote UE uses SL-RSRP measurement for the serving U2N relay UE for relay reselection trigger evaluation, and in the absence of data transmission from the U2N relay UE to the U2N remote UE, it will depend on the UE implementation to decide whether to use SL-RSRP or SD-RSRP for relay reselection trigger evaluation.

[0335] If the PC5 link quality measured by the U2N Remote UE for the U2N Relay UE exceeds a configured threshold (pre-configured or provided by the gNB), the U2N Remote UE considers the U2N Relay UE to be suitable for radio measurement. The U2N Remote UE retrieves suitable U2N Relay UE candidates that meet all AS layer and higher layer criteria (see TS 23.304

[48] ). If there are multiple such candidate U2N Relay UEs, it is up to the U2N Remote UE implementation to select one of them. For L2 U2N Relay selection (reselection), PLMN ID and Cell ID can be used as additional AS criteria.

[0336] The U2N remote UE triggers the U2N relay selection in the following cases:

[0337] -The direct Uu signal strength of the current serving cell of the U2N remote UE is below the configured signal strength threshold;

[0338] - Indicated by upper layers of the U2N remote UE.

[0339] U2N remote UE can trigger U2N relay reselection in the following cases:

[0340] -The current PC5 signal strength of the U2N relay UE is lower than the (pre-)configured signal strength threshold;

[0341] - Cell reselection, handover, Uu RLF or Uu RRC connection establishment / recovery failure has been indicated by the U2N relay UE via PC5-RRC signaling;

[0342] -When the U2N remote UE receives a PC5-S link release message from the U2N relay UE;

[0343] -When the U2N remote UE detects PC5 RLF;

[0344] -Instructed by upper layer.

[0345] For L2 U2N Remote UE and L3 U2N Remote UE in RRC_IDLE or RRC_INACTIVE, the cell selection (reselection) procedure and the relay selection (reselection) procedure run independently. If both a suitable cell and a suitable U2N Relay UE are available, it depends on the U2N Remote UE implementation to select the cell or the U2N Relay UE. The L3 U2N Remote UE may select both the cell and the L3 U2N Relay UE at the same time, and this depends on the implementation of the L3 U2N Remote UE.

[0346] For both L2 and L3 U2N relay UEs in RRC_IDLE or RRC_INACTIVE, PC5-RRC message is used to notify its connected U2N remote UEs when the U2N relay UE selects a new cell. PC5-RRC message is also used to notify its connected L2 or L3 U2N remote UEs when the L2 or L3 U2N relay UE performs handover, detects Uu RLF or its Uu RRC connection establishment / recovery fails. After receiving the PC5 RRC message for notification, it is up to the U2N remote UE implementation to decide whether to release or maintain the unicast PC5 link. If the U2N remote UE decides to release the unicast PC5 link, it triggers the PC5 release procedure and may perform cell or relay reselection.

[0347] 16.12.5 Control Plane Procedures for L2 U2N Relay

[0348] 16.12.5.1RRC Connection Management

[0349] L2 U2N remote UE needs to establish its own PDU session / DRB with the network before user plane data transfer.

[0350] The NR sidelink PC5 unicast link establishment procedure may be used to set up a secure unicast link between the L2 U2N remote UE and the L2 U2N relay UE before the L2 U2N remote UE establishes a Uu RRC connection with the network via the L2 U2N relay UE.

[0351] The establishment of Uu SRB1 / SRB2 and DRB for L2 U2N remote UE is subject to Uu configuration procedure for L2 UE to network relay.

[0352] Fig.16 The following high-level connection establishment procedure in .12.5.1-1 applies to L2 U2N Relay and L2 U2N Remote UE:

[0353] [Figure 3GPP TS 38.300 V17.5.0 entitled "Procedure for L2 U2N Remote UE Connection Establishment"

[0354] 16.12.5.1-1 is reproduced as Fig.14 ]

[0355] 1. The L2 U2N Remote and L2 U2N Relay UEs perform a discovery procedure and establish a PC5-RRC connection using the NR sidelink PC5 unicast link establishment procedure.

[0356] 2. The L2 U2N Remote UE sends a first RRC message (i.e., RRCSetupRequest) for its connection establishment with the gNB via the L2 U2N Relay UE using the designated PC5 Relay RLC channel configuration. If the L2 U2N Relay UE is not in RRC_CONNECTED, it needs to perform its own Uu RRC connection establishment upon receiving the message on the designated PC5 Relay RLC channel. After the RRC connection establishment procedure of the L2 U2N Relay UE, the gNB configures the SRB0 Relay Uu Relay RLC channel to the U2N Relay UE. The gNB responds to the L2 U2N Remote UE with an RRCSetup message. The RRCSetup message is sent to the L2 U2N Remote UE using the SRB0 Relay Uu Relay channel on Uu and the designated PC5 Relay RLC channel on PC5.

[0357] Note 1: Empty.

[0358] 3. The gNB and L2 U2N relay UE perform the relay channel establishment procedure over Uu. Based on the configuration from the gNB, the L2U2N relay / remote UE establishes the PC5 relay RLC channel for relaying of SRB1 over PC5 towards the L2 U2N remote / relay UE.

[0359] 4. An RRCSetupComplete message is sent by the L2 U2N Remote UE to the gNB via the L2 U2N Relay UE using the SRB1 Relay channel on PC5 and the SRB1 Relay channel on Uu configured to the L2 U2N Relay UE. The L2 U2N Remote UE is then in RRC_CONNECTED as if the gNB were.

[0360] 5. The L2 U2N Remote UE and gNB follow the Uu Security Mode procedures to establish security and the security messages are forwarded via the L2 U2N Relay UE.

[0361] 6. The gNB sends an RRCReconfiguration message to the L2 U2N Remote UE via the L2 U2N Relay UE to set up the end-to-end SRB2 / DRB of the L2 U2N Remote UE. The L2 U2N Remote UE sends an RRCReconfigurationComplete message to the gNB via the L2 U2N Relay UE as a response. In addition, the gNB may configure an additional Uu relay RLC channel between the gNB and the L2 U2N Relay UE, and a PC5 relay RLC channel between the L2 U2N Relay UE and the L2 U2N Remote UE for relay services.

[0362] 3GPP TS22.261 specifies the connectivity model and KPIs for UE to network relay in 5G systems as follows:

[0363] 6.9 Connectivity Model

[0364] 6.9.1 Description

[0365] A UE (remote UE) can be connected directly to the network (direct network connection), connected using another UE as a relay UE (indirect network connection), or connected using both direct and indirect connections. Relay UEs can be used in many different scenarios and verticals (inHome, SmartFarming, SmartFactories, public safety, etc.). In these cases, the use of relay UEs can be used to improve the energy efficiency and coverage of the system.

[0366] The remote UE can be anything from a simple wearable, such as a sensor embedded in clothing, to a more complex wearable UE listening to biometrics. It can also be a non-wearable UE communicating in a personal area network, such as a group of home appliances (e.g., a smart thermostat and input keys), or an electronic UE in an office environment (e.g., a smart printer), or a smart flower pot that can be remotely activated to water a plant.

[0367] When a remote UE attempts to establish an indirect network connection, there may be several available relay UEs in the vicinity, and a procedure for selecting a suitable relay UE among the available relay UEs needs to be supported.

[0368] Indirect network connection covers the use of relay UEs for connecting remote UEs to the 3GPP network. There may be one or more relay UEs (more than one hop) between the network and the remote UE.

[0369] The ProSe Inter-UE Relay may also be used to connect two remote Public Safety UEs using a direct device connection.There may be one or more ProSe Inter-UE Relays (more than one hop) between two remote Public Safety UEs.

[0370] 6.9.2 Requirements

[0371] The following set of requirements supplements the requirements listed in 3GPP TS 22.278 [5], clauses 7B and 7C.

[0372] 6.9.2.1 Overview

[0373] The 5G system will support the use of one or more relay UEs to relay services between remote UEs and gNBs.

[0374] The 5G system will support the same traffic flow of remote UEs to be relayed via different indirect network connection paths.

[0375] The 5G system will support different service flows of remote UEs to be relayed via different indirect network connection paths.

[0376] The connection between the remote UE and the relay UE will be able to use 3GPP RAT or non-3GPP RAT and use licensed or unlicensed frequency bands.

[0377] The connection between the remote UE and the relay UE will be able to use fixed broadband technology.

[0378] When the remote UE and the relay UE subscribe to different PLMNs and both PLMNs have roaming agreements with the VPLMN, the 5G system will support the indirect network connection mode in the VPLMN.

[0379] The 5G system will be able to support UEs using simultaneous indirect and direct network connection modes.

[0380] When using relay UEs, network operators will be able to define the maximum number of hops supported in their network.

[0381] The 5G system will be able to manage communications between remote UEs and the 5G network across multi-path indirect network connections.

[0382] 3GPP TS23.304 introduces UE-to-Network Relay (U2N) in Release 18. For single-hop U2N relay, U2N relay can be used to support data communication between the remote UE and the network when the remote UE cannot communicate directly with the network. U2N relay needs to establish a PC5 unicast link (or PC5 RRC connection) with the remote UE and establish an RRC connection with a network node (e.g., gNB) to support data communication between the remote UE and the network. According to 3GPP TS22.261, multi-hop U2N relay can be supported in Release 19. Fig.16 An exemplary 3-hop U2N relay is shown. Also, when using relay UEs, network operators will be able to define the maximum number of hops supported in their network.

[0383] Considering that the more hops are used, the more delay is incurred, it is not appropriate for the network to configure one value of the maximum number of hops for services with different QoS requirements. Therefore, it is advantageous for the network to configure the maximum number of hops on a service basis. For example, the network may provide the maximum number of hops for each (ProSe) Relay Service Code (RSC) to the relay UE in order to limit the maximum number of hops for a multi-hop U2N relay, where the RSC indicates the connectivity service provided by the U2N relay to the remote UE. Alternatively, the network may provide a mapping of the maximum number of hops to the (ProSe) RSC to the relay UE. In one embodiment, each RSC may be associated with one or more PDU sessions.

[0384] As described in 3GPP TS23.304, the remote UE may perform a discovery procedure to find a U2N relay and then establish a PC5 unicast link with the U2N relay in order to access the network via the U2N relay. According to 3GPP TS 38.300, the U2N relay UE may perform relay discovery messaging and may listen to the side link for relay discovery messaging when in RRC_IDLE, RRC_INACTIVE, or RRC_CONNECTED. In other words, the U2N relay UE should be within the coverage (IC) of the network in order to perform relay discovery messaging, and the U2N relay UE out of coverage (OOC) is not allowed to perform relay discovery messaging because the remote UE cannot access the network via the OOC U2N relay UE.

[0385] In order to support multi-hop U2N relaying, it is not necessary for all relays involved in the multi-hop U2N relaying to be within the coverage area (IC) of the network. Fig.15 For example, it is sufficient that relay 3 is in coverage (IC), and other relays (i.e., relay 1 and relay 2) may be out of coverage (OOC). In order to allow remote UEs to find relay 3 (which is an IC relay), relay 3 may initiate inter-UE relay discovery with model A by transmitting or broadcasting a U2N relay discovery notification message including a cumulative hop count of 1. When receiving the U2N relay discovery notification message from relay 3, relay 2 may transmit or broadcast a new U2N relay discovery notification message including a cumulative hop count of 2.

[0386] Similarly, Relay 1 may transmit or broadcast another U2N Relay Discovery Notification message including the cumulative hop count 3 in response to receiving the U2N Relay Discovery Notification message from Relay 2. After receiving the U2N Relay Discovery Notification message from Relay 1, the remote UE may then establish a PC5 unicast link (or a PC5 RRC connection) with Relay 1. A PC5 unicast link may also be established between Relay 1 and Relay 2 and a PC5 unicast link may be established between Relay 2 and Relay 3, so that the remote UE may access the network via Relay 1, Relay 2, and Relay 3. In this example, it is assumed that the maximum hop count is greater than 3.

[0387] In order to implement the maximum hop limit configured by the network, the U2N relay discovery notification message needs to include the cumulative hop count. If the cumulative hop count included in the received discovery message reaches the maximum hop count, the relay UE should not continue to broadcast or transmit the U2N relay discovery notification message. If the relay UE is in the IC of the network, the relay UE does not need to continue to broadcast or transmit the U2N relay discovery notification message for the remote UE. In other words, the IC relay UE can ignore the received U2N relay discovery notification message. Basically, the IC relay UE can initiate the U2N relay discovery procedure by itself, for example, the IC relay UE can broadcast or transmit a U2N relay discovery notification message with the cumulative hop count set to 1.

[0388] As described above, when receiving a U2N relay discovery notification message from other U2N relays (even if they are in the OOC of the network), the intermediate U2N relays (e.g., Relay 1 and Relay 2) should be allowed to transmit or broadcast another U2N relay discovery notification message. However, only the IC U2N relay is allowed to initiate the U2N relay discovery procedure by broadcasting or transmitting a U2N relay discovery notification message with the cumulative hop count set to 1.

[0389] Fig.16 An example of the above concept for multi-hop UE to network relay is shown. In general, Fig.16 An exemplary multi-hop UE-to-network relay discovery with Model A is shown.

[0390] like Fig.17 As shown in , which shows an exemplary multi-route UE to network relay, there may be multiple routes for the remote UE to reach the network via different relay UEs. Respectively, route A has 3 hops and route B has 2 hops. In this case, it is beneficial to consider the cumulative number of hops for the relay UE (or route) selection in terms of the transmission delay of the remote UE. For example, the remote UE may select relay 4 (i.e., route B) for communication with the network. In other words, the remote UE may select a relay UE indicating fewer (or smaller) cumulative hops, and the remote UE may connect to the network via the relay UE. The remote UE may then transmit a direct communication request message to the selected relay UE for establishing a PC5 unicast link (or PC5RRC connection) with the selected relay UE. For relay UE selection, other factors such as the signal strength of the relay UE (e.g., RSRP) may also be considered.

[0391] A similar situation may occur for an intermediate relay UE when a direct communication request message is received from a remote UE or other relay UE (i.e., there may be multiple routes to choose from). In this case, it is beneficial for the intermediate relay UE to consider the cumulative number of hops for relay UE (or route) selection. For example, the intermediate relay UE may select a relay UE indicating the least (or minimum) cumulative number of hops for continuing the subsequent procedure of the remote UE. The intermediate relay UE may then transmit a direct communication request message to the selected relay UE for establishing a PC5 unicast link (or PC5 RRC connection) with the selected relay UE.

[0392] On the other hand, the remote UE may initiate inter-UE relay discovery with model B by transmitting or broadcasting a U2N relay discovery solicitation message. When receiving the U2N relay discovery solicitation message from the remote UE, the relay UE may transmit or broadcast a new U2N relay discovery solicitation message including a cumulative hop count of 1. The following relay UE may also transmit or broadcast other U2N relay discovery solicitation messages including an increased cumulative hop count until the maximum hop count has been reached or the relay UE is within the coverage (IC) of the network. For example, when receiving the U2N relay discovery solicitation message from other relay UEs, if the relay UE is within the IC of the network, the relay UE may reply with a new U2N relay discovery response message. Otherwise, if the relay UE is out of coverage (OOC) of the network and the maximum hop count has not been reached (i.e., the cumulative hop count included in the received U2N relay discovery solicitation message plus 1 is less than (or less than) the maximum hop count), the relay UE may transmit or broadcast another U2N relay discovery solicitation message.

[0393] Fig.18 1800 is a flow chart of a method for supporting multi-hop UE to network relay. In step 1805, the network provides a maximum hop count specific to a relay service code (RSC) to a second relay UE. In step 1810, the second relay UE receives a first U2N relay discovery notification message from a first relay UE, wherein the first U2N relay discovery notification message includes a user information identifier (ID) of the first relay UE, an RSC, and a first cumulative hop count. In step 1815, if the first cumulative hop count plus 1 is less than or equal to the maximum hop count, the second relay UE transmits or broadcasts a second U2N relay discovery notification message, wherein the second user equipment to network relay discovery notification message includes the user information ID of the second relay UE, the RSC, and the second cumulative hop count.

[0394] In one embodiment, the second relay UE may be out of coverage (OOC) of the network. When the second relay UE is in OOC of the network, the second relay UE may not be in any of RRC_IDLE, RRC_INACTIVE, and RRC_CONNECTED. The second cumulative hop count may be set to the first cumulative hop count plus 1. When the first cumulative hop count plus 1 is greater than the maximum hop count, the second relay UE may not transmit or broadcast the second U2N relay discovery notification message.

[0395] In one embodiment, the RSC may instruct the ProSe UE to relay the connectivity service provided to the ProSe remote UE to the network.

[0396] In one embodiment, the first relay UE may be a ProSe UE to a network relay. The second relay UE may be an intermediate UE to a network relay.

[0397] Return to reference Figure 3 and Figure 4 , in an exemplary embodiment from the perspective of the second relay UE. In one embodiment, the maximum number of hops specific to the RSC is provided by the network to the second relay UE. The second relay UE 300 includes a program code 312 stored in the memory 310. The CPU 308 can execute the program code 312 to enable the second relay UE to (i) receive a first U2N relay discovery notification message from the first relay UE, wherein the first U2N relay discovery notification message includes the user information ID, RSC and the first cumulative number of hops of the first relay UE, and (ii) if the first cumulative number of hops plus 1 is less than or equal to the maximum number of hops, transmit or broadcast a second U2N relay discovery notification message, wherein the second user equipment to network relay discovery notification message includes the user information ID, RSC and the second cumulative number of hops of the second relay UE. In addition, the CPU 308 can execute the program code 312 to perform all of the above actions and steps or other actions and steps described herein.

[0398] Various aspects of the present disclosure have been described above. It should be understood that the teachings herein can be embodied in a wide variety of forms, and any specific structure, function, or both disclosed herein are only representative. Based on the teachings herein, it should be understood by those skilled in the art that the aspects disclosed herein can be implemented independently of any other aspects, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement a device or practice a method. In addition, other structures, functions, or structures and functions different from the aspects described in addition to one or more aspects described herein can be used to implement such devices or practice such methods. As an example of some of the above concepts, in some aspects, parallel channels can be established based on pulse repetition frequencies. In some aspects, parallel channels can be established based on pulse positions or offsets. In some aspects, parallel channels can be established based on time hopping sequences. In some aspects, parallel channels can be established based on pulse repetition frequencies, pulse positions or offsets, and time hopping sequences.

[0399] Those skilled in the art will understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltage, current, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0400] Those skilled in the art will further appreciate that the various illustrative logical blocks, modules, processors, components, circuits, and algorithm steps described in conjunction with the aspects disclosed herein may be implemented as electronic hardware (e.g., digital implementations, analog implementations, or a combination of both, which may be designed using source decoding or some other techniques), and various forms of programs or design codes with instructions (for convenience, which may be referred to herein as "software" or "software modules"), or a combination of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functions. Whether such functions are implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system. Those skilled in the art may implement the described functions in different ways for each specific application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.

[0401] In addition, the various illustrative logical blocks, modules, and circuits described in conjunction with the aspects disclosed herein may be implemented within or performed by an integrated circuit ("IC"), an access terminal, or an access point. An IC may include a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, electrical components, optical components, mechanical components, or any combination thereof designed to perform the functions described herein, and may execute code or instructions residing within the IC, outside the IC, or both. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0402] It should be understood that any specific order or hierarchy of steps in any disclosed process is an example of an exemplary method. It should be understood that based on design preferences, the specific order or hierarchy of steps in a process can be rearranged while remaining within the scope of the present disclosure. The accompanying method claims present elements of the various steps in an exemplary order and are not meant to be limited to the specific order or hierarchy presented.

[0403] The steps of the method or algorithm described in conjunction with the various aspects disclosed herein may be implemented directly in hardware, software modules executed by a processor, or a combination of the two. Software modules (e.g., including executable instructions and related data) and other data may reside in a data memory, such as a RAM memory, a flash memory, a ROM memory, an EPROM memory, an EEPROM memory, a register, a hard disk, a removable disk, a CD-ROM, or any other form of computer-readable storage medium known in the art. An example storage medium may be coupled to a machine such as a computer / processor (which may be referred to herein as a "processor" for convenience), such a processor may read information (e.g., code) from a storage medium and write the information to the storage medium. An example storage medium may be integrated with a processor. The processor and storage medium may reside in an ASIC. The ASIC may reside in a user device. In an alternative, the processor and storage medium may reside in a user device as discrete components. In addition, in some aspects, any suitable computer program product may include a computer-readable medium, which includes code related to one or more aspects of the present disclosure. In some aspects, a computer program product may include packaging materials.

[0404] Although the present invention has been described in conjunction with various aspects, it will be appreciated that the present invention is capable of further modifications. This application is intended to cover any changes, uses or adaptations of the present invention that generally follow the principles of the present invention and include such deviations from the present disclosure that are within the scope of known and customary practice in the field to which the present invention relates.

Claims

1. A method for supporting multi-hop user equipment to network relay, characterized in that: include: The network provides the second relay user equipment with a maximum number of hops specific to the relay service code; The second relay user equipment receives a first user equipment-to-network relay discovery notification message from the first relay user equipment, wherein the first user equipment-to-network relay discovery notification message includes a user information identifier of the first relay user equipment, the relay service code, and a first accumulated hop count; and If the first cumulative hop count plus 1 is less than or equal to the maximum hop count, the second relay user equipment transmits or broadcasts a second user equipment to network relay discovery notification message, wherein the second user equipment to network relay discovery notification message includes the user information identifier of the second relay user equipment, the relay service code and the second cumulative hop count.

2. The method according to claim 1, characterized in that: The second relay user equipment is out of coverage of the network.

3. The method according to claim 2, characterized in that When the second relay user equipment is out of coverage of the network, the second relay user equipment is not in any one of RRC_IDLE, RRC_INACTIVE and RRC_CONNECTED.

4. The method according to claim 1, characterized in that The second accumulated hop count is set to be the first accumulated hop count plus 1.

5. The method according to claim 1, characterized in that If the first cumulative number of hops plus 1 is greater than the maximum number of hops, the second relay user equipment does not transmit or broadcast the second user equipment to network relay discovery notification message.

6. The method according to claim 1, characterized in that The relay service code indicates a connectivity service provided by a proximity based service user equipment to a network relay to a proximity based service remote user equipment.

7. The method according to claim 1, characterized in that The first relay user equipment is a proximity-based service user equipment to network relay.

8. The method according to claim 1, characterized in that The second relay user equipment is an intermediate user equipment to network relay.

9. A second relay user equipment for supporting multi-hop user equipment to network relay, characterized in that: The network provides the second relay user equipment with a maximum number of hops specific to the relay service code, the second relay user equipment comprising: Control circuit; a processor installed in the control circuit; and a memory installed in the control circuit and operatively coupled to the processor; wherein the processor is configured to execute program code stored in the memory to: Receiving a first user equipment-to-network relay discovery notification message from a first relay user equipment, wherein the first user equipment-to-network relay discovery notification message includes a user information identifier of the first relay user equipment, the relay service code, and a first cumulative hop count; and If the first cumulative hop count plus 1 is less than or equal to the maximum hop count, a second user equipment to network relay discovery notification message is transmitted or broadcast, wherein the second user equipment to network relay discovery notification message includes the user information identifier of the second relay user equipment, the relay service code and the second cumulative hop count.

10. The second relay user equipment according to claim 9, characterized in that: The second relay user equipment is out of coverage of the network.

11. The second relay user equipment according to claim 10, characterized in that: When the second relay user equipment is out of coverage of the network, the second relay user equipment is not in any one of RRC_IDLE, RRC_INACTIVE and RRC_CONNECTED.

12. The second relay user equipment according to claim 9, characterized in that: The second accumulated hop count is set to be the first accumulated hop count plus 1.

13. The second relay user equipment according to claim 9, characterized in that: If the first cumulative number of hops plus 1 is greater than the maximum number of hops, the second relay user equipment does not transmit or broadcast the second user equipment to network relay discovery notification message.

14. The second relay user equipment according to claim 9, characterized in that: The relay service code indicates a connectivity service provided by a proximity based service user equipment to a network relay to a proximity based service remote user equipment.

15. The second relay user equipment according to claim 9, characterized in that: The first relay user equipment is a proximity-based service user equipment to network relay.

16. The second relay user equipment according to claim 9, characterized in that: The second relay user equipment is an intermediate user equipment to network relay.

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