Method and apparatus for notification message transmission and reception in wireless communication system

Abstract

A method and apparatus for notification message transmission and reception in a wireless communication system. An inter-UE relay UE establishes a first PC5 radio resource control connection with a first remote UE, and establishes one or more second PC5 radio resource control connections with one or more additional remote UEs, the first remote user equipment may communicate with one or more additional remote user equipment via the inter-user equipment relay user equipment. The inter-UE relay user equipment also transmits a notification message to the first remote user equipment, wherein the notification message contains the sidelink indication type and information identifying a second remote user equipment of the one or more additional remote user equipment.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 536,657, filed on September 5, 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 methods and apparatus for notification message transmission and reception in wireless communication systems. Background Art

[0004] With the rapid growth of the demand for transmitting large amounts of data to and from mobile communication devices, traditional mobile voice communication networks have evolved into networks that communicate using Internet Protocol (IP) packets. This IP packet communication can provide IP-bearing voice, multimedia, multicast and on-demand communication services for 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 implement the above-mentioned IP-bearing voice and multimedia services. Currently, the 3GPP standards organization is discussing the next generation (e.g., 5G) new air interface technology. Therefore, changes to the current body of 3GPP standards are currently being submitted and considered to evolve and complete the 3GPP standards. Summary of the invention

[0006] A method and apparatus for notification message transmission. In one embodiment, a UE-to-UE (U2U) relay UE establishes a first PC5 radio resource control (RRC) connection with a first remote UE, and establishes one or more second PC5 RRC connections with one or more additional remote UEs, so that the first remote UE can communicate with the one or more additional remote UEs via the U2U relay UE. The U2U relay UE also transmits a notification message to the first remote UE, wherein the notification message includes a sidelink indication type and information identifying a second remote UE in the one or more additional remote UEs. 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 It is 3GPP TS23.304V18.2.0 Figure 4 .2.7.1-1, 3GPP TS23.304V18.2.0 Figure 4 .2.8-1 reappearance;

[0012] Figure 6 It is 3GPP TS23.304V18.2.0 Figure 4 .2.7.2-1, 3GPP TS23.304V18.2.0 Figure 6 .4.3.1-1 reappearance;

[0013] Figure 7 It is 3GPP TS23.304V18.2.0 Figure 6 .3.2.1-1, 3GPP TS23.304V18.2.0 Figure 6 .7.1.1-1 reappearance;

[0014] Figure 8 It is 3GPP TS23.304V18.2.0 Figure 6 .3.2.1-2, Reproduction of Figure 16.12.2.x-1 of 3GPP R2-2307920;

[0015] Fig. 9 It is 3GPP TS23.304V18.2.0 Figure 6 .3.2.3.2-1, Reproduction of Figure 16.12.2.x-2 of 3GPP R2-2307920;

[0016] Fig.10 It is 3GPP TS23.304V18.2.0 Figure 6 .3.2.3.3-1, Reproduction of Figure 16.12.3.1 of 3GPP R2-2307920;

[0017] Fig.11 It is 3GPP TS23.304V18.2.0 Figure 6.5.1.1-1、3GPP R2-2309185 Figure 5 .8.9.8.1-1 reappearance;

[0018] Fig.12 An example of notification messaging for a single-hop U2U relay is described according to an exemplary embodiment;

[0019] Fig.13 is a flow chart according to an exemplary embodiment;

[0020] Fig.14 is a flow chart according to an exemplary embodiment. DETAILED DESCRIPTION

[0021] The exemplary wireless communication systems and devices described below employ 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) radio access, 3GPP Long Term Evolution Advanced (LTE-A or LTE-Advanced), 3GPP2 Ultra Mobile Broadband (UMB), WiMax, 3GPP New Radio (NR), or some other modulation technology.

[0022] 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 association named "3rd Generation Partnership Project" (referred to herein as 3GPP), including: TS 23.304 V18.2.0, "Proximity based Service (ProSe) in 5G System (5GS) (Release 18)"; R2-2307920, "Introduction of NR Sidelink Relay Enhancement", LG Electronics; and R2-2309185, "Introduction of NR Sidelink U2U Relay". The standards and documents listed above are hereby expressly incorporated by reference in their entirety.

[0023] Figure 11 shows a multiple access wireless communication system according to an embodiment of the present invention. 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 In the figure, 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 an 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 the frequency used by reverse link 118.

[0024] Each group of antennas and / or the area in which they are 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.

[0025] In communicating over 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 that uses beamforming to transmit to access terminals that are randomly dispersed throughout the coverage area of ​​the access network may generate less interference to access terminals in neighboring cells than an access network that transmits to all of its access terminals via a single antenna.

[0026] 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, Node B, base station, enhanced base station, evolved Node B (eNB), network node, network, or some other term. An access terminal (AT) may also be referred to as user equipment (UE), a wireless communication device, a terminal, an access terminal, or some other term.

[0027] Figure 22 is 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 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.

[0028] In one embodiment, each data stream is transmitted through 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.

[0029] The decoded 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 decoded data for each data stream is then modulated (i.e., symbol mapped) based on a particular modulation scheme (e.g., BPSK, QPSK, M-PSK, or M-QAM) selected for that data stream to provide modulation symbols. The data rate, coding, and modulation for each data stream may be determined by instructions executed by processor 230.

[0030] The modulation symbols for all data streams are then provided to a TX MIMO processor 220, which may further process the modulation symbols (eg, for OFDM). The TX MIMO processor 220 then converts the N 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.

[0031] 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 via the MIMO channel. T The antennas 224a to 224t transmit N signals from the transmitters 222a to 222t. T a modulated signal.

[0032] At the receiver system 250, N RThe 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 provide samples, and further processes the samples to provide a corresponding “received” symbol stream.

[0033] RX data processor 260 then extracts the N R The receiver 254 receives and processes N R received 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.

[0034] 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.

[0035] The reverse link message may include various types of information related to the communication link and / or the received data stream. The reverse link message is then processed by the TX data processor 238, modulated by the modulator 280, conditioned by the transmitters 254a to 254r, and transmitted back to the transmitter system 210, the TX data processor also receiving traffic data for a plurality of data streams from the data source 236.

[0036] At the transmitter system 210, the modulated signal from the receiver system 250 is 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.

[0037] 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 in FIG. , 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 1The 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 (for example, a keyboard or a keypad), and can output images and sounds through the output device 304 (for example, a monitor 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.

[0038] Figure 4 According to an embodiment of the present invention Figure 3 4. A simplified block diagram of program code 312 is shown in FIG. 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 generally performs radio resource control. Layer 2 portion 404 typically performs link control. Layer 1 portion 406 typically performs physical connectivity.

[0039] 3GPP TS 23.304 specifies procedures related to inter-UE relay as follows:

[0040] 4.2.8 5G ProSe Inter-UE Relay Reference Architecture

[0041] Figure 4 .2.8-1 shows the layer 2 and layer 3 5G ProSe inter-UE relay reference architecture. 5G ProSe end UEs communicate with each other via the 5G ProSe inter-UE relay.

[0042] [3GPP TS 23.304 V18.2.0 titled "Reference architecture for 5G ProSe inter-UE relay" Figure 4 .2.8-1 reproduced as Figure 5 ]

[0043] Each 5G ProSe end UE and 5G ProSe inter-UE relay can have a subscription from the same PLMN or different PLMNs.

[0044] […]

[0045] 6.4.3.1 Layer 2 link establishment over PC5 reference point

[0046] In order to perform ProSe direct communication in unicast mode over PC5 reference point, the UE is configured with relevant information as described in Section 5.1.3.

[0047] Figure 6 .4.3.1-1 shows the Layer 2 link establishment procedure for ProSe direct communication in unicast mode over the PC5 reference point.

[0048] [3GPP TS 23.304 V18.2.0 entitled "Layer 2 Link Establishment Procedure" Figure 6 .4.3.1-1 Reproduced as Figure 6 ]

[0049] 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.

[0050] 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.

[0051] The ProSe application layer in UE-1 may provide the ProSe application requirements for this unicast communication. As specified in Section 5.6.1, UE-1 determines the PC5 QoS parameters and PFI.

[0052] If UE-1 decides to reuse the existing PC5 unicast link as specified in section 5.3.4, the UE triggers the Layer 2 Link Modification procedure as specified in section 6.4.3.4.

[0053] 3. UE-1 sends a direct communication request message to initiate the unicast layer 2 link establishment procedure. The direct communication request message contains:

[0054] - Source user information: the application layer ID of the originating UE (ie, the application layer ID of UE-1).

[0055] - If the ProSe application layer provides the application layer ID of the target UE in step 2, the following information is included:

[0056] - Target user information: Application layer ID of the target UE (ie, the application layer ID of UE-2).

[0057] -ProSe service information: Information about the ProSe identifier requesting Layer 2 link establishment.

[0058] - Security information: information used to establish security.

[0059] NOTE 1 Security information and the necessary protection of source user information and destination user information are defined by SA WG3.

[0060] As specified in Sections 5.8.2.1 and 5.8.2.4, the source layer 2ID and destination layer 2ID used to send the direct communication request message are determined. The destination layer 2ID can be a broadcast or unicast layer 2ID. When a unicast layer 2ID is used, the target user information should be included in the direct communication request message.

[0061] UE-1 transmits a direct communication request message to PC5 by broadcasting or unicasting using the source layer 2 ID and the destination layer 2 ID.

[0062] The default PC5 DRX configuration may be used to transmit and receive this message (see TS 38.300

[12] ).

[0063] 4. Establish security with UE-1 as follows:

[0064] 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.

[0065] 4b. If the target user information is not included in the direct communication request message, the UE interested in using the announced ProSe service over the PC5 unicast link with UE-1 responds by establishing security with UE-1.

[0066] NOTE 2: Signalling for security procedures is defined by SA WG3.

[0067] When security protection is enabled, UE-1 sends the following information to the target UE:

[0068] - If using IP communication:

[0069] -IP address configuration: For IP communication, this link requires an IP address configuration, and the IP address configuration indicates one of the following values:

[0070] - "DHCPv4 server", if only IPv4 address allocation mechanism is supported by the initiating UE, i.e. acting as a DHCPv4 server; or

[0071] - "IPv6 router", if only IPv6 address allocation mechanisms are supported by the initiating UE, i.e. acting as an IPv6 router; or

[0072] - "DHCPv4 server and IPv6 router", if both IPv4 and IPv6 address allocation mechanisms are supported by the initiating UE; or

[0073] - "Address allocation not supported" if neither IPv4 nor IPv6 address allocation mechanisms are supported by the initiating UE.

[0074] - 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] .

[0075] - QoS Information: Information about PC5 QoS flows. For each PC5 QoS flow, PFI and corresponding PC5 QoS parameters (ie PQI and conditionally other parameters such as MFBR / GFBR) and optionally associated ProSe identifier.

[0076] -Optional PC5 QoS rules.

[0077] As specified in Sections 5.8.2.1 and 5.8.2.4, the source Layer 2ID for the security establishment procedure is determined. The destination Layer 2ID is set to the source Layer 2ID of the received direct communication request message.

[0078] After 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.

[0079] 5. The target UE, which has successfully established security with UE-1, sends a direct communication acceptance message to UE-1:

[0080] 5a. (Layer 2 link establishment towards UE) If the direct communication request message contains target user information, then if the application layer ID for UE-2 matches, the target UE, i.e. UE-2, responds with a direct communication accept message.

[0081] 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.

[0082] The direct communication acceptance message contains:

[0083] -Source user information: the application layer ID of the UE that sends the direct communication acceptance message.

[0084] - QoS Information: Information about PC5 QoS flows. For each PC5 QoS flow, the PFI and the corresponding PC5 QoS parameters requested by UE-1 (ie PQI and conditionally other parameters such as MFBR / GFBR) and optionally the associated ProSe identifier.

[0085] -Optional PC5 QoS rules.

[0086] - If using IP communication:

[0087] -IP address configuration: For IP communication, this link requires an IP address configuration, and the IP address configuration indicates one of the following values:

[0088] - "DHCPv4 Server", if only IPv4 address allocation mechanism is supported by the target UE, i.e. act as a DHCPv4 server; or

[0089] - "IPv6 router", if only IPv6 address allocation mechanisms are supported by the target UE, i.e. acting as an IPv6 router; or

[0090] - "DHCPv4 server and IPv6 router", if both IPv4 and IPv6 address allocation mechanisms are supported by the target UE; or

[0091] - "Address allocation not supported" if neither IPv4 nor IPv6 address allocation mechanisms are supported by the target UE.

[0092] - Link-local IPv6 address: A link-local IPv6 address formed locally based on RFC 4862

[17] . If the target UE does not support the IPv6 IP address allocation mechanism, i.e., the IP address configuration indicates "address allocation is not supported", and UE-1 includes a link-local IPv6 address in the Direct Communication Request message, the target UE shall include a non-conflicting link-local IPv6 address.

[0093] If two UEs (ie, an initiating UE and a target UE) are selected to use link-local IPv6 addresses, the two UEs shall deactivate dual address detection as defined in RFC 4862

[17] .

[0094] NOTE 3: When the initiating UE or the target UE indicates support for IPv6 routing, the corresponding address configuration process shall be implemented after the layer 2 link is established and the link-local IPv6 address shall be ignored.

[0095] 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 2 ID information (i.e., source layer 2 ID and destination layer 2 ID). This enables the AS layer to maintain the PC5 link identifier and PC5 unicast link related information.

[0096] Two UEs may negotiate the PC5 DRX configuration in the AS layer, and PC5 DRX parameter values ​​may be configured for each pair of source and destination Layer 2 IDs in the AS layer.

[0097] 6. ProSe data is transmitted over the established unicast link as follows:

[0098] The PC5 link identifier and PFI as well as ProSe data are provided to the AS layer.

[0099] Optionally in addition, layer 2 ID information (ie, source layer 2 ID and destination layer 2 ID) is provided to the AS layer.

[0100] NOTE 4: It is up to the UE implementation to provide the Layer 2 ID information to the AS layer.

[0101] 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).

[0102] NOTE 5: The PC5 unicast link is bidirectional, so UE-1's peer UE can send ProSe data to UE-1 through the unicast link with UE-1.

[0103] […]

[0104] 6.4.3.7 Layer 2 Link Management over PC5 Reference Point for 5G ProSe Inter-UE Relay

[0105] 6.4.3.7.1 Common part of Layer 2 link management over PC5 reference point for 5G ProSe inter-UE relay

[0106] For 5G ProSe communication via 5G ProSe inter-UE relay as described in Sections 6.7.1 and 6.7.2:

[0107] -The direct communication request message through the first hop PC5 reference point contains:

[0108] -User information ID of the source 5G ProSe UE: the identifier of the source 5G ProSe UE requesting the relay operation (i.e., the user information ID).

[0109] - User Information ID of 5G ProSe Inter-UE Relay: The identity of the Inter-UE Relay (i.e., User Information ID) provided to the source 5G ProSe end UE during the 5G ProSe Inter-UE Relay discovery procedure.

[0110] - User Information ID of target 5G ProSe UE: the identity of the target 5G ProSe UE (i.e., User Information ID) provided to the source 5G ProSe UE during the inter-UE relay discovery procedure.

[0111] - (Optional) Destination Layer 2 ID of target 5G ProSe side UE: The unicast destination Layer 2 ID of the target 5G ProSe side UE determined by the source 5G ProSe side UE, as specified in Section 5.8.2.4.

[0112] -ProSe service information: Information about the ProSe identifier requesting Layer 2 link establishment.

[0113] -RSC: Connectivity service requested by the source 5G ProSe UE and provided by the 5G ProSe inter-UE relay.

[0114] - Security information: information used to establish security for first-hop PC5 link establishment.

[0115] NOTE 1 Security information is defined by SAWG3.

[0116] The direct communication request message through the second hop PC5 reference point contains:

[0117] -User information ID of the source 5G ProSe UE.

[0118] -User information ID of the target 5G ProSe UE.

[0119] -User information ID relayed between 5G ProSe UEs.

[0120] -ProSe service information: information about the ProSe identifier.

[0121] -RSC: Connectivity service requested by the source 5G ProSe UE and provided by the 5G ProSe inter-UE relay.

[0122] - Security information: information used to establish security for the second hop PC5 link establishment.

[0123] NOTE 2 Security information is defined by SAWG3.

[0124] The direct communication acceptance message via the second hop PC5 reference point contains:

[0125] -User information ID of the target 5G ProSe UE.

[0126] The direct communication acceptance message via the first hop PC5 reference point contains:

[0127] -User information ID of the target 5G ProSe UE.

[0128] -User information ID relayed between 5G ProSe UEs.

[0129] The link modification request message through the first hop PC5 reference point contains:

[0130] - User information ID of target 5G ProSe UE: The identity of the target 5G ProSe UE provided to the source 5G ProSe UE during the inter-UE relay discovery procedure.

[0131] - (Optional) Destination Layer 2 ID of target 5G ProSe side UE: The unicast destination Layer 2 ID of the target 5G ProSe side UE determined by the source 5G ProSe side UE, as specified in Section 5.8.2.4.

[0132] The link modification request message through the second hop PC5 reference point contains:

[0133] -User information ID of the source 5G ProSe UE.

[0134] -User information ID of the target 5G ProSe UE.

[0135] The link modification acceptance message through the second hop PC5 reference point contains:

[0136] -User information ID of the target 5G ProSe UE.

[0137] The link modification acceptance message through the first hop PC5 reference point contains:

[0138] -User information ID of the target 5G ProSe UE.

[0139] 6.4.3.7.2 Layer 2 Link Management over PC5 Reference Point for 5G ProSe Layer 2 Inter-UE Relay

[0140] For 5G ProSe communication via 5G ProSe layer 2 inter-UE relay as described in Section 6.7.2, the description in Section 6.4.3.7.1 applies.

[0141] The message contents over the PC5 reference point for unicast mode 5G ProSe direct communication described in Sections 6.4.3.1 to 6.4.3.5 are the same for end-to-end connections between peer 5G ProSe end UEs.

[0142] […]

[0143] 6.4.3.7.4 Layer 2 Link Management over PC5 Reference Point for 5G ProSe Inter-UE Relay Communication Integrated with Discovery This section is for 5G ProSe Inter-UE Relay Communication integrated with discovery procedure as described in Section 6.7.3.

[0144] The direct communication request message through the first hop PC5 reference point contains:

[0145] -User information ID of the source 5G ProSe UE.

[0146] -(Optional) User information ID of target 5G ProSe UE: the identifier of the target 5G ProSe UE if provided from the ProSe application layer.

[0147] - (Optional) Destination Layer 2 ID of target 5G ProSe side UE: The unicast destination Layer 2 ID of the target 5G ProSe side UE determined by the source 5G ProSe side UE, as specified in Section 5.8.2.4.

[0148] -ProSe service information: Information about the ProSe identifier requesting Layer 2 link establishment.

[0149] -RSC: Connectivity service requested by the source 5G ProSe UE and provided by the 5G ProSe inter-UE relay.

[0150] -Relay_indication: indicates whether the direct communication request message can be forwarded by the 5G ProSe inter-UE relay.

[0151] - Security information: information used to establish security for first-hop PC5 link establishment.

[0152] NOTE 1 Security information is defined by SA WG3.

[0153] The direct communication request message through the second hop PC5 reference point contains:

[0154] -User information ID of the source 5G ProSe UE.

[0155] -User information ID relayed between 5G ProSe UEs.

[0156] -(Optional) User information ID of the target 5G ProSe UE.

[0157] -ProSe service information: information about the ProSe identifier.

[0158] -RSC: Connectivity service requested by the source 5G ProSe UE and provided by the 5G ProSe inter-UE relay.

[0159] - Security information: information used to establish security for the second hop PC5 link establishment.

[0160] NOTE 2 Security information is defined by SA WG3.

[0161] The direct communication acceptance message via the second hop PC5 reference point contains:

[0162] -User information ID of the target 5G ProSe UE.

[0163] The direct communication acceptance message via the first hop PC5 reference point contains:

[0164] -User information ID of the target 5G ProSe UE.

[0165] -User information ID relayed between 5G ProSe UEs.

[0166] For 5G ProSe communication via 5G ProSe layer 3 inter-UE relay, additional explanations are as follows:

[0167] -In the security procedure of the second-hop PC5 reference point, the 5G ProSe layer 3 inter-UE relay provides the IP address configuration or link-local IPv6 address to the target 5G ProSe end UE.

[0168] - The direct communication accept message over the second hop PC5 reference point additionally includes the IP address configuration or link-local IPv6 address (if IP communication is used), the Ethernet MAC address of the target 5G ProSe end UE (if Ethernet communication is used). QoS information is not included in the security procedures or direct communication accept message of the second hop PC5 reference point.

[0169] - In the security procedure of the first-hop PC5 reference point, the source 5G ProSe end UE provides the 5G ProSe layer 3 inter-UE relay with IP address configuration, link-local IPv6 address and QoS information of end-to-end QoS.

[0170] -5G ProSe Layer 3 Inter-UE Relay provides QoS information of the second hop QoS to the target 5G ProSe end UE using Layer 2 Link Modification as described in Section 6.4.3.4.

[0171] - Taking into account the second-hop QoS received from the target 5G ProSe side UE, the 5G ProSe layer 3 inter-UE relay determines the QoS information of the first-hop QoS, and the direct communication acceptance message through the first-hop PC5 reference point additionally includes the IP address configuration or link-local IPv6 address, the QoS information of the first-hop QoS, and may include the IP address of the target 5G ProSe side UE (if IP communication is used) or the Ethernet MAC address of the target 5G ProSe side UE (if Ethernet communication is used).

[0172] For 5G ProSe communication via 5G ProSe layer 2 inter-UE relay, the message contents over the PC5 reference point for unicast mode 5G ProSe direct communication described in Sections 6.4.3.1 to 6.4.3.5 are the same for end-to-end connections between peer 5G ProSe end UEs.

[0173] […]

[0174] 6.7.1 5G ProSe Communication via 5G ProSe Layer 3 Inter-UE Relay

[0175] 6.7.1.1 Layer 2 Link Establishment for PC5 Communication via 5G ProSe Layer 3 Inter-UE Relay

[0176] Figure 6 .7.1.1-1 shows the procedure for Layer 2 link establishment via 5G ProSe Layer 3 inter-UE relay.

[0177] [3GPP TS 23.304 V18.2.0 entitled "Layer 2 link establishment via 5G ProSe Layer 3 inter-UE relay" Figure 6 .7.1.1-1 Reproduced as Figure 7 ]

[0178] 1. Perform service authorization and provisioning for the source 5G ProSe Layer 3 UE, the target 5G ProSe Layer 3 UE and the 5G ProSe Layer 3 inter-UE relay as described in Section 6.2.

[0179] 2. The source 5G ProSe layer 3 end UE performs discovery of 5G ProSe layer 3 inter-UE relays as described in Section 6.3.2.4.

[0180] 3. The source 5G ProSe layer 3 end UE sends a direct communication request message to initiate a unicast layer 2 link establishment procedure using 5G ProSe layer 3 inter-UE relay. The parameters included in the direct communication request message are described in Section 6.4.3.7.

[0181] The source layer 2 ID of the direct communication request message is assigned by the source 5G ProSe layer 3 end UE, and the destination layer 2 ID is set to the source layer 2 ID of the discovery message relayed between 5G ProSe layer 3 UEs.

[0182] 4. If the User Information ID of the 5G ProSe Layer 3 Inter-UE Relay in the Direct Communication Request message matches the User Information ID of the 5G ProSe Inter-UE Relay and the RSC in the Direct Communication Request matches one of the RSCs supported by the relay, the 5G ProSe Layer 3 Inter-UE Relay responds by establishing security with the source 5G ProSe Layer 3 end UE. When security protection is enabled, the source 5G ProSe Layer 3 end UE sends the parameters as described in Section 6.4.3.7 to the 5G ProSe Layer 3 Inter-UE Relay.

[0183] If the Ethernet MAC address of the source 5G ProSe layer 3 end UE is already used by another 5G ProSe layer 3 end UE, the 5G ProSe layer 3 inter-UE relay may send a message to the source 5G ProSe layer 3 end UE indicating that there is an Ethernet MAC address conflict.

[0184] The source Layer 2 ID used for the security establishment procedure is self-assigned by the 5G ProSe Layer 3 inter-UE relay, and the destination Layer 2 ID is set to the source Layer 2 ID of the received direct communication request message.

[0185] 5G ProSe layer 3 inter-UE relay will select different source layer 2 IDs for PC5 links for different types of services (i.e., IP services, Ethernet services, and unstructured services).

[0186] If the PC5 link is used to deliver unstructured traffic, the 5G ProSe layer 3 inter-UE relay will select different source layer 2 IDs for different pairs of source and target 5G ProSe layer 3 end UEs.

[0187] After receiving the security establishment procedure message, the source 5G ProSe layer 3 end UE obtains the layer 2 ID of the 5G ProSe layer 3 inter-UE relay for future communications, thereby being used for signaling and data services of this unicast link.

[0188] 5. After the security establishment procedure in step 4 is completed, the 5G ProSe layer 3 inter-UE relay sends a direct communication request message to initiate a unicast layer 2 link establishment procedure with the target 5G ProSe layer 3 end UE. The parameters included in the direct communication request message are described in Section 6.4.3.7.

[0189] The source layer 2 ID of the direct communication request message is assigned by the 5G ProSe layer 3 inter-UE relay, and the destination layer 2 ID is the unicast layer 2 ID of the target 5G ProSe layer 3 end UE associated with the user information ID of the target 5G ProSe layer 3 end UE.

[0190] 5G ProSe layer 3 inter-UE relay will select different source layer 2 IDs for PC5 links for different types of services (i.e., IP services, Ethernet services, and unstructured services).

[0191] If the PC5 link is used to deliver unstructured traffic, the 5G ProSe layer 3 inter-UE relay will select different source layer 2 IDs for different pairs of source and target 5G ProSe layer 3 end UEs.

[0192] 6. If the user information ID and RSC of the target 5G ProSe layer 3 end UE contained in the direct communication request match the user information ID of the target UE and the RSC supported by the target UE, the target 5G ProSe layer 3 end UE responds by establishing security with the 5G ProSe layer 3 inter-UE relay. When security protection is enabled, the 5G ProSe layer 3 inter-UE relay sends the parameters as described in Section 6.4.3.7 to the target 5G ProSe layer 3 end UE.

[0193] The source layer 2 ID used for the security establishment procedure is self-assigned by the target 5G ProSe layer 3 end UE, and the destination layer 2 ID is set to the source layer 2 ID of the received direct communication request message.

[0194] After receiving the security establishment procedure message, the 5G ProSe layer 3 inter-UE relay obtains the layer 2 ID of the target 5G ProSe layer 3 end UE for future communications, thereby being used for signaling and data services of this unicast link.

[0195] 7. The target 5G ProSe layer 3 end UE sends a direct communication accept message to the 5G ProSe layer 3 inter-UE relay with which security has been successfully established. The parameters included in the direct communication accept message are described in Section 6.4.3.7.

[0196] 8. For IP services, an IPv6 prefix or IPv4 address is allocated to the target 5G ProSe Layer 3 UE as defined in Section 5.5.1.4.

[0197] 9. After receiving the Direct Communication Accept message from the target 5G ProSe Layer 3 end UE, the 5G ProSe Layer 3 Inter-UE Relay sends a Direct Communication Accept message to the source 5G ProSe Layer 3 end UE with which security has been successfully established. The parameters included in the Direct Communication Accept message are described in Section 6.4.3.7.

[0198] 10. For IP services, an IPv6 prefix or IPv4 address is allocated to the source 5G ProSe layer 3 end UE as defined in Section 5.5.1.4.

[0199] 11. For IP communication, the 5G ProSe layer 3 inter-UE relay may store the association of the user information ID with the IP address of the target 5G ProSe layer 3 end UE in its DNS entry, and the 5G ProSe layer 3 inter-UE relay may act as a DNS server for other UEs. If the IP address of the target 5G ProSe layer 3 end UE is not received in step 9, the source 5G ProSe layer 3 end UE may send a DNS query to the 5G ProSe layer 3 inter-UE relay after step 10 to request the IP address of the target 5G ProSe layer 3 end UE, and the 5G ProSe layer 3 inter-UE relay transmits the IP address of the target 5G ProSe layer 3 end UE back to the source 5G ProSe layer 3 end UE.

[0200] For Ethernet communications, the 5G ProSe Layer 3 inter-UE relay maintains the association between the PC5 link and the Ethernet MAC address received from the 5G ProSe Layer 3 end UE.

[0201] For unstructured service communications, for each pair of source and target 5G ProSe layer 3 end UEs, the 5G ProSe layer 3 inter-UE relay maintains a 1:1 mapping between the PC5 link and the source 5G ProSe layer 3 end UE and between the PC5 link and the target 5G ProSe layer 3 end UE.

[0202] 12. The source 5G ProSe layer 3 end UE communicates with the target 5G ProSe layer 3 end UE via the 5G ProSe layer 3 inter-UE relay.

[0203] In the case where a source 5G ProSe layer 3 end UE communicates with multiple target 5G ProSe layer 3 end UEs, according to RSC, the PC5 link between the source 5G ProSe layer 3 end UE and the 5G ProSe layer 3 inter-UE relay can be shared among the multiple target 5G ProSe layer 3 end UEs, while according to RSC, the PC5 link can be established individually between the 5G ProSe layer 3 inter-UE relay and the target 5G ProSe layer 3 end UE. For the shared PC5 link, the layer 2 link modification procedure should be used.

[0204] In the case where multiple source 5G ProSe layer 3 end UEs communicate with one target 5G ProSe layer 3 end UE, the PC5 link between the 5G ProSe layer 3 inter-UE relay and the target 5G ProSe layer 3 end UE can be shared according to RSC, while the PC5 link can be established individually between the source 5G ProSe layer 3 end UE and the 5G ProSe layer 3 inter-UE relay according to RSC. For the shared PC5 link, the layer 2 link modification procedure should be used.

[0205] […]

[0206] 3GPP R2-2307920 introduces NR sidelink relay enhancements to the NR Phase 2 specification (i.e. TS 38.300). The enhancements to inter-UE relay are as follows:

[0207] 16.12 Sidelink Relay

[0208] 16.12.1 Overview

[0209] 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] .

[0210] The U2N relay UE shall be in RRC_CONNECTED to perform relay of unicast data.

[0211] For L2 U2N relay operation, the following RRC state combinations are supported:

[0212] - 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

[0213] - 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.

[0214] 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.

[0215] 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.

[0216] The U2U relay UE will support the inter-UE relay (U2U relay) functionality as specified in TS23.304 to provide coverage extension of the sidelink transmission between two U2U remote UEs. For coverage extension, the U2U remote UE can communicate with a peer U2U remote UE that is no longer reachable within the sidelink coverage. The U2U relay UE and the U2U remote UE can be in any RRC state. The U2U relay UE and the U2U remote UE can be in the coverage of different cells. For U2U relay, NR PC5 side link is supported between the U2U relay UE and the U2U remote UE. Only unicast is supported between the U2U relay UE and the U2U remote UE.

[0217] […]

[0218] 16.12.2.x L2 Inter-UE Relay

[0219] The protocol stacks for the user plane and control plane for the L2 U2N relay architecture are illustrated in Figure 16.12.2.x-1 and Figure 16.12.2.x-2. The SRAP sublayer is disposed above the RLC sublayer for both CP and UP at two PC5 interfaces. Sidelink SDAP, PDCP and RRC terminate between two L2 U2U remote UEs, while SRAP, RLC, MAC and PHY terminate in each PC5 link, where each link is between a L2 U2U remote UE and a L2 U2U relay UE.

[0220] [Figure 16.12.2.x-1 of 3GPP R2-2307920 entitled "User Plane Protocol Stack for L2 Inter-UE Relay" is reproduced as Figure 8 ]

[0221] [Figure 16.12.2.x-2 of 3GPP R2-2307920 entitled "Control Plane Protocol Stack for L2 Inter-UE Relay" is reproduced as Fig. 9 ]

[0222] For L2 inter-UE relay, the SRAP sublayer at the L2 U2U remote UE:

[0223] - The SRAP sublayer at the L2 U2U remote UE performs bearer mapping between the end-to-end SL radio bearers (SRB, DRB) of the L2 U2U remote UE and the PC5 relay RLC channels through the L2 U2U relay UE. When the U2U remote UE receives a data packet via the same egress PC5 relay RLC channel for different end-to-end bearers, the U2U remote UE can identify the data packet by using both the end-to-end bearer ID and the U2U remote UE ID.

[0224] - The PC5 SRAP sublayer at the L2 U2U Remote UE supports identification of peer L2 U2U Remote UEs. An ID that can be mapped to a peer L2 U2U Remote UE is included in the SRAP header of traffic from the L2 U2U Remote UE to the L2 U2U Relay. An ID that can be mapped to a L2 U2U Remote UE is included in the SRAP header of traffic from the L2 U2U Relay UE to the peer L2 U2U Remote UE.

[0225] For L2 inter-UE relay, the SRAP sublayer at the L2 U2U relay UE:

[0226] - The SRAP sublayer at the L2 U2U relay UE performs bearer mapping between the ingress PC5 relay RLC channel and the egress PC5 relay RLC channel by using both the end-to-end bearer ID and the U2U remote UE ID.

[0227] -The SRAP sublayer at the L2 U2U relay UE may perform data multiplexing from multiple ingress PC5 relay RLC channels of the same / different L2 U2U remote UEs to the same PC5 relay RLC channel of the peer L2 U2U remote UE for different end-to-end bearers. The SRAP sublayer at the L2 U2U relay UE may perform data demultiplexing from the same ingress PC5 relay RLC channel of the L2 U2U remote UE to multiple egress PC5 relay RLC channels of different peer L2 U2U remote UEs for different end-to-end bearers.

[0228] Editor's note: Details on whether to use L2 ID / shortened ID or whether to include two or one ID in the SRAP header are for further study.

[0229] 16.12.3 Relay Discovery

[0230] 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 illustrated in Figure 16.12.3-1.

[0231] [Figure 16.12.3.1 of 3GPP R2-2307920 entitled "Protocol stack for discovery messages for UE to network / inter-UE relay" is reproduced as Fig.10 ]

[0232] 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 the relay discovery message 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.

[0233] 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.

[0234] U2U remote UE and U2U relay UE may perform relay discovery messaging and may listen for relay discovery messages when in RRC_IDLE, RRC_INACTIVE or RRC_CONNECTED. The network may provide relay discovery configuration using broadcast or dedicated signaling. In addition, U2N remote UE and L3 U2N relay UE may use pre-configuration for relay discovery.

[0235] The resource pool for NR side link communication can be used for relay discovery or the network can configure a resource pool dedicated to relay discovery. The resource pool dedicated to relay discovery can be configured simultaneously with the resource pool used for NR side link communication in system information, dedicated signaling and / or pre-configuration. Whether the dedicated resource pool for relay discovery is configured based on the network implementation plan. If a resource pool dedicated to relay discovery is configured, only those resource pools dedicated to relay discovery are applied to relay discovery. If only a resource pool for NR side link communication is configured, all configured resource pools can be used for relay discovery and NR side link communication.

[0236] 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.

[0237] 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.

[0238] For both in-coverage and out-of-coverage U2N remote UEs or U2U relay UEs, the NR sidelink resource allocation principles (both Mode-1 and Mode-2) are applied for relay discovery messaging.

[0239] The sidelink power control for transmission of relay discovery messages is the same as the sidelink power control used for NR sidelink communication.

[0240] Ciphering or integrity protection in the PDCP layer shall not be used for the Relay Discovery Message.

[0241] U2N / U2U remote UE and U2N / U2U relay UE can determine whether the gNB supports relay discovery, non-relay discovery, or both based on SIB12.

[0242] Editor's Note: A detailed description for forwarding discovery messages based on PC5 RSRP threshold according to the discovery model (Model A / B, Integrated Discovery) will be added after further discussion.

[0243] 16.12.4 Relay Selection / Reselection

[0244] 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.

[0245] 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.

[0246] 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 suitable U2N Relay UEs, it is up to the U2N Remote UE implementation to select one of them. For L2 U2N Relay (re)selection, PLMN ID and Cell ID may be used as additional AS criteria.

[0247] The U2N remote UE triggers the U2N relay selection in the following cases:

[0248] -The direct Uu signal strength of the current serving cell of the U2N remote UE is below the configured signal strength threshold;

[0249] - Indicated by upper layers of the U2N remote UE.

[0250] The U2N remote UE can trigger U2N relay reselection in the following situations:

[0251] -The current PC5 signal strength of the U2N relay UE is lower than the (pre-)configured signal strength threshold;

[0252] - Cell reselection, handover, Uu RLF or Uu RRC connection establishment / recovery failure has been indicated by the U2N relay UE via PC5-RRC signalling;

[0253] -When the U2N remote UE receives a PC5-S link release message from the U2N relay UE;

[0254] -When the U2N remote UE detects PC5 RLF;

[0255] -Instructed by upper layer.

[0256] For L2 U2N remote UE and L3 U2N remote UE in RRC_IDLE or RRC_INACTIVE, the cell (re)selection procedure and the relay (re)selection procedure run independently. If both a suitable cell and a suitable U2N relay UE are available, the cell or U2N relay UE is selected depending on the U2N remote UE implementation. The L3 U2N remote UE can select both a cell and a L3 U2N relay UE at the same time, and this depends on the implementation of the L3 U2N remote UE.

[0257] For both L2 and L3 U2N relay UEs in RRC_IDLE or RRC_INACTIVE, when the U2N relay UE selects a new cell, the PC5-RRC message is used to notify its connected U2N remote UEs. The 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 a handover, detects Uu RLF, or its Uu RRC connection establishment / recovery fails. After receiving the PC5 RRC message for notification, it depends on 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 can perform cell or relay reselection.

[0258] The U2U remote UE performs radio measurements (ie, SD-RSRP and / or SL-RSRP) at the PC5 interface and uses them together with higher layer criteria as specified in TS 23.304

[48] for U2U relay selection and reselection.

[0259] For relay selection, when there is data transmission from the U2U Remote UE to the peer U2U Remote UE, the U2U Remote UE uses the SL-RSRP measurement for the peer U2U Remote UE for relay selection trigger evaluation. For relay reselection, when there is data transmission from the U2U Remote UE to the U2U Relay UE, the U2U Remote UE uses the SL-RSRP measurement for the U2U Relay UE for relay reselection trigger evaluation. In the absence of data transmission from the U2U Remote UE to the peer U2U Remote UE or U2U Relay UE, it will depend on the U2U Remote UE implementation to decide whether to use SL-RSRP or SD-RSRP for relay selection or reselection trigger evaluation. The thresholds for SD-RSRP and SL-RSRP are configured separately for triggering U2U relay selection or reselection.

[0260] If the PC5 link quality measured by the U2U remote UE for the U2U relay UE exceeds a configured threshold, the U2U remote UE considers the U2U relay UE to be suitable in terms of radio calibration.

[0261] The U2U remote UE triggers the U2U relay selection in the following cases:

[0262] - PC5 signal strength between U2U remote UEs is below a (pre-)configured signal strength threshold;

[0263] - Indicated by upper layers of the U2U remote UE.

[0264] The U2U remote UE triggers U2U relay reselection in the following cases:

[0265] -The current PC5 signal strength of the U2U relay UE is lower than the (pre)configured signal strength threshold;

[0266] -When the U2U remote UE detects PC5 RLF;

[0267] -When the U2U Remote UE receives a PC5 RLF indication from the U2U Relay UE;

[0268] -When the U2U remote UE receives a PC5-S link release message from the U2U relay UE;

[0269] - Indicated by upper layers of the U2U remote UE.

[0270] Relay selection / reselection may be triggered by each U2U remote UE based on the current hop quality.

[0271] For discovery model A, the U2U relay UE shall only notify the neighboring U2U remote UEs whose SD-RSRP / SL-RSRP between the U2U relay and the neighboring U2U remote UE is higher than the configured threshold in the discovery notification message. After the discovery message reception, if the SD-RSRP for the U2U relay UE is higher than the configured threshold and the upper layer criteria are met, the U2U remote UE regards the U2U relay UE as a candidate U2U relay UE.

[0272] For discovery model B, after discovery response message reception, if the SD-RSRP for the U2U relay UE is above the configured threshold and meets the upper layer criteria, the U2U remote UE considers the U2U relay UE as a candidate U2U relay UE.

[0273] For integrated discovery, upon receiving a DCR message from one or more U2U relay UEs, the U2U remote UE shall consider candidate U2U relay UEs whose SL-RSRP is above the configured threshold to respond and meet the upper layer criteria, and select a U2U relay UE from among them.

[0274] 3GPP R2-2309185 introduces NR sidelink inter-UE relay into NR Phase 3 specification (ie TS 38.331). The notification message procedure is as follows:

[0275] 5.8.9.10 Notification Message

[0276] 5.8.9.10.1 Overview

[0277] [3GPP R2-2309185 entitled "Notification Messages in Sidelink" Figure 5 .8.9.8.1-1 reproduced as Fig.11 ]

[0278] This procedure is used by a U2N relay UE to send notifications to a connected U2N remote UE. This procedure is also used by a U2U relay UE to send notifications to a connected U2U remote UE.

[0279] 5.8.9.10.2 Initiation

[0280] The relay UE may initiate the procedure when one of the following conditions is met:

[0281] 1> If the UE acts as a U2N relay UE:

[0282] 2> after the Uu RLF as specified in 5.3.10;

[0283] 2>After receiving RRCReconfiguration containing reconfigurationWithSync;

[0284] 2>After the cell is reselected;

[0285] 2> after an RRC connection failure of the L2 U2N relay UE including an RRC Connection Reject as specified in 5.3.3.5 and 5.3.13.10, and T300 expires as specified in 5.3.3.7 and RRC recovery fails as specified in 5.3.13.5;

[0286] 1> If the UE acts as a U2U relay UE:

[0287] 2> After PC5 RLF is detected by the U2U remote UE as specified in 5.8.9.3;

[0288] Editor's note: Whether the remote UE in the previous protocol "When the remote UE receives the PC5-RLF indication from the U2U relay UE, it shall notify the upper layer and rely on the upper layer to trigger relay reselection (or not)" applies to both the source and target remote UEs, and whether it applies to both L2 and L3 U2U relays is for further study.

[0289] 5.8.9.10.3 Actions related to the delivery of NotificationMessageSidelink messages

[0290] The relay UE shall set the indication type as follows:

[0291] 1> If the UE acts as a U2N relay UE;

[0292] 2> If the UE initiates the transmission of the NotificationMessageSidelink message due to Uu RLF:

[0293] 3>Set indicationType to relayUE-Uu-RLF;

[0294] 2> Otherwise, if the UE initiates the transmission of the NotificationMessageSidelink message due to reconfiguration using synchronization:

[0295] 3> Set indicationType to relayUE HO;

[0296] 2> Otherwise, if the UE initiates the transmission of the NotificationMessageSidelink message due to cell reselection:

[0297] 3>Set indicationType to relayUE-CellReselection;

[0298] 2> If the UE initiates the transmission of the NotificationMessageSidelink message due to a failure in UuRRC connection establishment / recovery:

[0299] 3>Set indicationType to relayUE-Uu-RRC-Failure;

[0300] 2> Submit the NotificationMessageSidelink message to the lower layer for transmission;

[0301] 1> If the UE acts as a U2U relay UE:

[0302] 2> If the UE initiates the transmission of the NotificationMessageSidelink message due to PC5 RLF:

[0303] 3>Set sl-IndicationType to relayUE-PC5-RLF.

[0304] 5.8.9.10.4 Actions related to the receipt of NotificationMessageSidelink messages

[0305] Upon receiving the NotificationMessageSidelink, the remote UE shall:

[0306] 1> If the UE acts as a U2N remote UE:

[0307] 2> If indicationType is included:

[0308] 3> If the UE is a L2 U2N remote UE in RRC_CONNECTED:

[0309] 4> If T301 is not running, initiate the RRC connection re-establishment procedure as specified in 5.3.7;

[0310] 3> Otherwise (UE is L3 U2N remote UE or L2 U2N remote UE in RRC_IDLE or RRC_INACTIVE):

[0311] 4> If it is determined that the PC5-RRC connection with the U2N relay UE is to be released, then:

[0312] 5> Instruct the upper layer to trigger the release of PC5 unicast link;

[0313] 4> Otherwise (i.e., maintain PC5 RRC connection):

[0314] 5> If the UE is a L2 U2N remote UE and indicationType is relayUE-HO or relayUE-CellReselection:

[0315] 6> Consider cell reselection;

[0316] NOTE 1: For a L3 U2N remote UE or L2 U2N remote UE in RRC_IDLE or RRC_INACTIVE, it is up to the remote UE implementation to decide whether to release or maintain the PC5 unicast link.

[0317] NOTE 2: If the L2 U2N remote UE has not released the PC5 unicast link on the source side during the indirect to direct path handover, i.e., T304 is running, it may ignore the NotificationMessageSidelink.

[0318] 1> If the UE acts as a U2U remote UE:

[0319] 2> If sl-IndicationType is relayUE-PC5-RLF:

[0320] 3> Instruct the upper layer to trigger the reselection of the NR sidelink U2U relay UE;

[0321] Editor's note: Whether there are any constraints on the remote UE's implementation behavior to maintain or release the PC5 link with the relay UE is for further study.

[0322] […]

[0323] -NotificationMessageSidelink

[0324] The NotificationMessageSidelink message is used to send a notification message from a U2N relay UE to a connected U2N remote UE or from a U2U relay UE to a connected U2U remote UE.

[0325] Signaling Radio Bearer: SL-SRB3

[0326] RLC-SAP:AM

[0327] Logical channel: SCCH

[0328] Direction: U2N relay UE to U2N remote UE or U2U relay UE to U2U remote UE

[0329] NotificationMessageSidelinkMessage

[0330]

[0331] 3GPP TS23.304 introduced inter-UE (U2U) relay in Release 18. For single-hop inter-UE relay, the inter-UE relay can be used to support data communication between two remote UEs when the two remote UEs cannot communicate directly with each other. The inter-UE relay needs to establish a PC5 unicast link (or PC5 RRC connection) with each of the source remote UE and the target remote UE. In the case of layer 2 inter-UE relay, after the first two PC5 unicast links have been established between the inter-UE relay and the two remote UEs, an end-to-end link (or connection) for unicast communication can be established between the two remote UEs.

[0332] After connecting to the U2U relay UE to communicate with each other via the U2U relay UE, the remote UE may keep performing measurements of the signal strength of the PC5 unicast link with the U2U relay UE for relay reselection. In addition, the U2U relay UE may also keep performing measurements of the signal strength of the PC5 unicast link with the remote UE. As captured in R2-2309185, when the U2U relay UE detects a PC5 (or sidelink) radio link failure (RLF) with one remote UE, it may send a notification message (i.e., NotificationMessageSidelink) to the peer remote UE so that the peer remote UE may instruct the upper layer to trigger relay reselection. The notification message contains an sl-IndicationType indicating relayUE-PC5-RLF. Since according to 3GPP TS 23.304, one remote UE can connect or communicate with multiple remote UEs via one U2U relay UE, the U2U relay UE is required to include information for identifying the remote UE that detected the PC5 RLF in the notification message so that the upper layer of the peer remote UE can perform relay reselection for the identified remote UE. The information for identifying the remote UE may be a layer 2 ID, an application layer ID, or a user information ID of the remote UE. Alternatively, the information for identifying the remote UE may be a local / short ID for identifying the remote UE in the SRAP header or a pair ID for identifying the remote UE and the peer remote UE pair in the SRAP header.

[0333] It is also beneficial for the U2U relay UE to send a notification message to the peer remote UE when releasing a PC5 unicast link (or PC5 RRC connection) with a remote UE so that the peer remote UE can indicate the sl-IndicationType to the upper layer to trigger relay reselection. In this case, the notification message may contain an sl-IndicationType indicating relayUE-PC5-release and information identifying the remote UE with which the PC5 unicast link (or PC5 RRC connection) is released. Fig.12 An example of notification messaging for single-hop U2U relay is described.

[0334] It is also beneficial for the U2U relay UE to send a notification message to the peer remote UE when the channel quality on the PC5 unicast link (or PC5 RRC connection) with one remote UE is below a threshold, so that the peer remote UE can indicate the sl-IndicationType to the upper layer to trigger relay reselection. In this case, the notification message may contain an sl-IndicationType indicating, for example, poor channel quality and information identifying the remote UE with which the channel quality of the PC5 unicast link (or PC5 RRC connection) is below the threshold.

[0335] For example, in Fig.12 In the present invention, UE1 (i.e., the source UE or the first remote UE) can communicate with UE2 and UE3 (i.e., the target UE or the second remote UE) via a single relay UE (i.e., relay 1). In response to detecting PC5 RLF, PC5 connection release, or poor channel quality on UE2, relay 1 can send a notification message to UE1. In the notification message, in addition to sl-IndicationType, the layer 2 ID, application layer ID, or user information ID of UE2 may also be included. Alternatively, a local / short ID for identifying UE2 in the SRAP header may be included in the notification message. Alternatively, a pair ID for identifying a pair of UE1 and UE2 in the SRAP header may be included in the notification message.

[0336] It is also feasible that the notification message may contain information identifying the remote UE involved and may not contain any SL indication type, because the peer remote UE may perform relay reselection in response to receiving the notification message regardless of the reason for the SL indication type. In other words, a notification message containing information identifying the remote UE involved (but not containing the SL indication type) may imply PC5 RLF detection, RC5 connection release, or poor channel quality on the remote UE involved.

[0337] Fig.13 1300 is a flowchart for notification message transition. In step 1305, an inter-UE (U2U) relay UE establishes a first PC5 radio resource control (RRC) connection with a first remote UE, and establishes one or more second PC5 RRC connections with one or more additional remote UEs, so that the first remote UE can communicate with the one or more additional remote UEs via the U2U relay UE. In step 1310, the U2U relay UE transmits a notification message to the first remote UE, wherein the notification message includes a sidelink indication type and information identifying a second remote UE among the one or more additional remote UEs.

[0338] In one embodiment, each of the first PC5 RRC connection and the plurality of second PC5 RRC connections may be a layer 2 link over a PC5 reference point. The side link indication type may be a PC5 radio link failure (RLF) with the second remote UE. When the U2U relay UE detects a PC5 RLF with the second remote UE, a notification message may be transmitted.

[0339] In one embodiment, the sidelink indication type may be a PC5 RRC connection release with the second remote UE. A notification message may be transmitted when the PC5 RRC connection between the U2U relay UE and the second remote UE is released.

[0340] Return to reference Figure 3 and Figure 4 , in an exemplary embodiment from the perspective of an inter-UE (U2U) relay UE. The U2U relay UE 300 includes program code 312 stored in a memory 310. The CPU 308 can execute the program code 312 to enable the U2U relay UE to: (i) establish a first PC5 radio resource control (RRC) connection with a first remote UE and establish one or more second PC5 RRC connections with one or more additional remote UEs, so that the first remote UE can communicate with the one or more additional remote UEs via the U2U relay UE, and (ii) transmit a notification message to the first remote UE, wherein the notification message includes a sidelink indication type and information identifying a second remote UE in the one or more additional remote UEs. 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.

[0341] Fig.14 1400 is a flow chart for notification message transition. In step 1405, a first remote UE communicates with one or more additional remote UEs via an inter-UE (U2U) relay UE. In step 1410, the first remote UE receives a notification message from the U2U relay UE, wherein the notification message includes a sidelink indication type and information identifying a second remote UE in the one or more additional remote UEs. In step 1415, the first remote UE indicates to an upper layer a sidelink indication type associated with the second remote UE.

[0342] In one embodiment, a first PC5 RRC connection may be established between a first remote UE and a U2U relay UE and one or more second PC5 RRC connections may be established between the U2U relay UE and one or more additional remote UEs. The sidelink indication type may be a PC5 radio link failure (RLF) with a second remote UE. After the U2U relay UE detects a PC5 RLF with the second remote UE, a notification message may be received.

[0343] In one embodiment, the sidelink indication type may be a PC5 RRC connection release with the second remote UE.After releasing the PC5 RRC connection between the U2U relay UE and the second remote UE, a notification message may be received.

[0344] Return to reference Figure 3 and Figure 4, in an exemplary embodiment from the perspective of a first remote UE. The first remote UE 300 includes program code 312 stored in a memory 310. The CPU 308 can execute the program code 312 to enable the first remote UE to: (i) communicate with one or more additional remote UEs via a U2U relay UE; (ii) receive a notification message from the U2U relay UE, wherein the notification message includes a sidelink indication type and information identifying a second remote UE in the one or more additional remote UEs; and (iii) indicate to an upper layer the sidelink indication type associated with the second remote 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.

[0345] Various aspects of the present disclosure have been described above. It should be understood that the teachings herein can be implemented 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 set forth herein can be used to implement a device or practice method. In addition, other structures, functionality, or structures and functionality other than one or more aspects set forth herein or different from the aspects can be used to implement such devices or practice such methods. As examples 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 hopping sequences. In some aspects, parallel channels can be established based on pulse repetition frequencies, pulse positions or offsets, and time hopping sequences.

[0346] 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.

[0347] 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 various aspects disclosed herein may be implemented as electronic hardware (e.g., a digital implementation, an analog implementation, or a combination of the two that may be designed using source decoding or some other technique), various forms of programs or design code incorporating instructions (which, for convenience, may be referred to herein as "software" or "software modules"), or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is 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 functionality 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.

[0348] 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. The 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. The processor may also be implemented as a combination of computing devices, such as 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.

[0349] 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 the elements of the various steps in a sample order and are not intended to be limited to the specific order or hierarchy presented.

[0350] The steps of the method or algorithm described in conjunction with the various aspects disclosed herein can be implemented directly with hardware, with a software module executed by a processor, or with a combination of the two. Software modules (e.g., including executable instructions and related data) and other data can 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 a computer-readable storage medium known in the art. An example storage medium can be coupled to a machine such as a computer / processor (for convenience, the machine can be referred to as a "processor" in this article) so that the processor can read information (e.g., code) from the storage medium and write information to the storage medium. An example storage medium can be integrated with a processor. The processor and the storage medium can reside in an ASIC. The ASIC can reside in a user device. In an alternative, the processor and the storage medium can 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 a code related to one or more of the various aspects of the present disclosure. In some aspects, a computer program product may include packaging materials.

[0351] Although the present invention has been described in conjunction with various aspects, it will be appreciated that the invention is capable of further modification. This application is intended to cover any changes, uses or adaptations of the present invention that generally follow the principles of the invention and include such deviations from the present disclosure that are within the scope of known and customary practice in the technical field to which the invention pertains.

Claims

1. A method for transmitting a notification message, characterized in that: include: The inter-user equipment relay user equipment establishes a first PC5 radio resource control connection with a first remote user equipment, and establishes one or more second PC5 radio resource control connections with one or more additional remote user equipments, so that the first remote user equipment can communicate with the one or more additional remote user equipments via the inter-user equipment relay user equipment; as well as The inter-UE relay UE transmits a notification message to the first remote UE, wherein the notification message includes a sidelink indication type and information identifying a second remote UE among the one or more additional remote UEs.

2. The method according to claim 1, characterized in that The first PC5 radio resource control connection and each of the one or more second PC5 radio resource control connections is a layer 2 link over a PC5 reference point.

3. The method according to claim 1, characterized in that The side link indication type is a PC5 radio link failure with the second remote user equipment.

4. The method according to claim 3, characterized in that The notification message is transmitted when the inter-UE relay UE detects a failure of the PC5 radio link with the second remote UE.

5. The method according to claim 1, characterized in that The sidelink indication type is a PC5 radio resource control connection release with the second remote user equipment.

6. The method according to claim 5, characterized in that The notification message is transmitted when a PC5 radio resource control connection between the inter-UE relay UE and the second remote UE is released.

7. A user equipment relaying user equipment, characterized in that: include: Control circuit; a processor, the processor being installed in the control circuit; as well as a memory installed in the control circuit and operably coupled to the processor; wherein the processor is configured to execute program code stored in the memory to: establishing a first PC5 radio resource control connection with a first remote user equipment, and establishing one or more second PC5 radio resource control connections with one or more additional remote user equipments, so that the first remote user equipment can communicate with the one or more additional remote user equipments via the inter-user equipment relay user equipment; as well as A notification message is transmitted to the first remote user equipment, wherein the notification message includes a sidelink indication type and information identifying a second remote user equipment among the one or more additional remote user equipments.

8. The inter-user equipment relay user equipment according to claim 7, characterized in that: The first PC5 radio resource control connection and each of the one or more second PC5 radio resource control connections is a layer 2 link over a PC5 reference point.

9. The inter-user equipment relay user equipment according to claim 7, characterized in that: The side link indication type is a PC5 radio link failure with the second remote user equipment.

10. The inter-user equipment relay user equipment according to claim 9, characterized in that: The notification message is transmitted when the inter-UE relay UE detects a failure of the PC5 radio link with the second remote UE.

11. The inter-user equipment relay user equipment according to claim 7, characterized in that: The sidelink indication type is a PC5 radio resource control connection release with the second remote user equipment.

12. The inter-user equipment relay user equipment according to claim 11, characterized in that: The notification message is transmitted when a PC5 radio resource control connection between the inter-UE relay UE and the second remote UE is released.

13. A method for notifying message reception, characterized in that: include: The first remote user equipment communicates with one or more additional remote user equipment via an inter-user equipment relay user equipment; The first remote user equipment receives a notification message from the inter-user equipment relay user equipment, wherein the notification message includes a sidelink indication type and information identifying a second remote user equipment among the one or more additional remote user equipments; as well as The first remote user equipment indicates, to an upper layer, the sidelink indication type associated with the second remote user equipment.

14. The method according to claim 13, characterized in that A first PC5 radio resource control connection is established between the first remote user equipment and the inter-user equipment relay user equipment and one or more second PC5 radio resource control connections are established between the inter-user equipment relay user equipment and the one or more additional remote user equipments.

15. The method according to claim 13, characterized in that The side link indication type is a PC5 radio link failure with the second remote user equipment.

16. The method according to claim 15, characterized in that The notification message is received after the inter-UE relay UE detects a failure of the PC5 radio link with the second remote UE.

17. The method according to claim 13, characterized in that The sidelink indication type is a PC5 radio resource control connection release with the second remote user equipment.

18. The method according to claim 17, characterized in that The notification message is received after releasing a PC5 radio resource control connection between the inter-UE relay UE and the second remote UE.

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