Multi-hop relay discovery announcement

Abstract

An intermediate relay terminal receives a first relay discovery announcement message from a parent terminal that is not PC5-S connected to the intermediate relay terminal. The first relay discovery announcement message comprises a first hop-count indicator indicating the parent terminal supports a multi-hop communication link to a cell and indicating a number of hops from the parent terminal to a cell. After determining that the intermediate relay terminal should transmit a second relay discovery announcement message, the intermediate relay terminal establishes a PC5-S connection with the parent terminal. After the PC5-S connection is established with the parent terminal, intermediate relay terminal transmits the second relay discovery announcement message comprising a second hop-count indicator that is the first hop indicator incremented by one.

Description

PCT / US25 / 40849 06 August 2025 (06.08.2025)TUTL 00405 PC-1 -MULTI-HOP RELAY DISCOVERY ANNOUNCEMENTCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to Provisional Application No. 63 / 680,963, entitled “Discovery and Relay (Re)selection Under Multihop Relay” and filed August 08, 2024, assigned to the assignee hereof and hereby expressly incorporated by reference in its entirety.FIELD

[0002] This invention generally relates to wireless communications and more particularly to multi-hop relay discovery announcements.BACKGROUND

[0003] Many wireless communication systems that employ several base stations (network nodes) that provide wireless service to terminals (user equipment (UE) devices) enable sidelink communication between two or more terminals where the terminals can communicate directly with other terminals. In addition, one or more terminal can be used as relay devices to form relay communication links between terminal and a cell of a base station or between a source UE device and a destination UE device. A relayed connection between a remote UE and the network through a relay device is often referred to as a UE-to-Network (U2N) link. The U2N link includes a PC5 link between the relay device and the remote UE and Uu link between the relay device and a cell of a base station in the network. Accordingly, a remote terminal (remote UE) may be connected to a cell of a network node through one or more intermediate relay terminals (relay UEs) forming the U2N link. The relay terminal directly connected to the cell is typically referred to as the last relay terminal or last relay UE (LRU). In some situations, multiple relay terminals can form a connection from the remote terminal to the network. Such an arrangement is typically referred to as a multi-hop relay communication link where each relay terminal provides one hop.PCT / US25 / 40849 06 August 2025 (06.08.2025)TUTL 00405 PC-2-

[0004] In some conventional systems, the U2N communication links use a Sidelink Relay Adaptation Protocol (SRAP) defined by one or more revisions of the 3rdGeneration Partnership Project (3GPP) standards to transmit control and data signals over the PC5 link and the Uu link. The SRAP is used to perform bearer mapping (signaling radio bearers (SRBs) and data radio bearers (DRBs)) between the two links. For U2N relays, a local Remote UE ID is included in both the PC5 SRAP header and the Uu SRAP header. The Layer 2 (L2) U2N Relay UE is configured by the gNB (network node) with the local Remote UE ID to be used in SRAP headers. In some situations, the U2N communication link may include more than one relay terminal.SUMMARY

[0005] An intermediate relay terminal receives a first relay discovery announcement message from a parent terminal that is not PC5-S connected to the intermediate relay terminal. The first relay discovery announcement message comprises a first hop-count indicator indicating the parent terminal supports a multi-hop communication link to a cell and indicating a number of hops from the parent terminal to a cell. After determining that the intermediate relay terminal should transmit a second relay discovery announcement message, the intermediate relay terminal establishes a PC5-S connection with the parent terminal. After the PC5-S connection is established with the parent terminal, intermediate relay terminal transmits the second relay discovery announcement message comprising a second hop-count indicator that is the first hop indicator incremented by one. The second hop indicator indicating the intermediate relay terminal supports the multi-hop communication link to the cell and indicating a second number of hops from the intermediate relay terminal to the cell. In some situations, the discovery announcement messages include a resource pool indicator indicating a discovery resource pool for transmission of discovery announcement messages.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIG. 1A is a block diagram of an example of a communication system where a first terminal transmits a first multi-hop discovery announcement and a secondPCT / US25 / 40849 06 August 2025 (06.08.2025)TUTL 00405 PC-3- terminal 106 transmits a second first multi-hop discovery announcement based on the first multi-hop discovery announcement.

[0007] FIG. 1 B is a block diagram of an example of a multi-hop relay discovery announcement.

[0008] FIG. 2 is a block diagram of an example of a base station suitable for use as the network node providing the serving cell.

[0009] FIG. 3 is a block diagram of an example of a UE device suitable for use as each of the terminals including remote terminal and relay terminals including the relay terminals.

[0010] FIG. 4 is a message flow diagram for an example where an intermediate relay terminal establishes an RRC-S connection with a parent terminal before forwarding a multi-hop relay discovery announcement received from the parent terminal.

[0011] FIG. 5 is a flow chart of an example of method of transmitting multi-hop relay discovery messages (discovery announcements).DETAILED DESCRIPTION

[0012] As discussed above, a relay communication link can be established between a serving cell and a remote terminal (remote user equipment (UE) device) through one or more relay terminals (relay UE devices). The relay communication link, often referred to as a UE-to-Network (U2N) communication link, includes PC5 links between the remote terminal and the relay terminal and between relay terminals when more than one relay terminal forms the U2N communication link. The remote terminal is connected through a first PC5 link to a first relay terminal. The first relay terminal is connected through a second PC5 link to the second relay terminal and the second relay terminal is connected to the serving cell over a Uu link. The relay communication link may include any number of intermediate relay terminals where a PC5 ingress link of each relay terminal is a PC5 egress link of an adjacent relay terminal. Except for the last relay terminal, therefore, each relay terminal in the U2N link has a PC5 ingress link to a terminal and a PC5 egress link to another terminal.PCT / US25 / 40849 06 August 2025 (06.08.2025)TUTL 00405 PC-4-

[0013] For multi-hop relay communication links, all terminals including remote terminals and intermediate relay terminals may perform discovery transmissions and Direct Communication Request (DCR) messages with integrated discovery transmissions while in coverage or out-of-coverage regardless of the RRC state. Communication standards allow U2N terminals to transmit discovery messages when both a maximum Uu RSRP threshold and / or a minimum Uu RSRP threshold are met when configured.

[0014] Current communication standards do not restrict transmission of discovery messages based on the connection status of a potential intermediate relay terminal to the next closest relay terminal (parent terminal) to the cell in a potential multi-hop communication link. Accordingly, it is possible for a terminal (e.g., remote terminal) to select a potential intermediate relay terminal transmitting a discovery message when the potential intermediate relay terminal is not yet PC5-connected to a parent terminal. If the remote terminal selects the potential intermediate relay terminal and the potential intermediate relay terminal fails to connect to the parent terminal, such as the U2N relay terminal, the remote terminal’s (re)selection would fail. This will result in failure in the remote terminal’s relay (re)selection which should be prevented. For the examples herein, however, the potential intermediate relay terminal does not transmit a relay discovery message unless the potential intermediate relay terminal has a PC5-S connection to the parent terminal. In some situations, a potential intermediate relay terminal determines that the discovery message should be forwarded and establishes the PC5-S connection before forwarding the discovery message. In other situations, the U2N relay terminal informs the cell of the PC5-RRC connection and, if needed, the cell pages the intermediate relay terminal or the cell requests that the U2N relay terminal to inform the remote terminal to initiate PC5-RRC connection.

[0015] A network node is any apparatus, equipment, device, or combination of devices, on the network side of the communication system that is connected to the communication network or is part of communication network. Some examples of a network node include a base station, a node B, an E-UTRA Node B, Evolved Node B, eNodeB, eNB, a New Generation eNB (ng-eNB), a gNodeB (also known as a gNB) inPCT / US25 / 40849 06 August 2025 (06.08.2025)TUTL 00405 PC-5- new radio (NR) technology, a macro station, pico station, and a femto station. The network node may form, or be a part of, the radio access network (RAN) that provides a connection between the core network and terminal communication devices. A RAN may be organized into three functional blocks including a Radio Unit (RU), a Distributed Unit (DU) and a Centralized Unit (CU). The RU transmits, receives, amplifies, and digitizes radio frequency signals and typically located near, or integrated into, the antenna. The DU and CU perform computations and / or processing to send and receive digitalized radio signals to and from the core network. The DU is typically located at or near the RU and the CU may be closer to the core network. The infrastructure or connection between the RU and the DU is often referred to as fronthaul and the infrastructure or connection between the DU and the CU is often referred to as a midhaul. The communication node, therefore, may perform the functions of one or more of the RU, DU and / or CU depending on the particular implementation.

[0016] A terminal communication device (terminal), such as a remote terminal and a relay terminal, is a communication device on the terminal side of the communication system and is sometimes referred to as user equipment (UE), a UE device, a terminal device, wireless mobile device, wireless communication device and other terms. Some examples of a terminal communication device include a mobile phone, a smart phone, a personal digital assistant (PDA), tablet, and laptop computer. In some situations, the terminal communication device is a machine type communication (MTC) communication device or Internet-of-Things (IOT) device. In addition, the terminal communication device may be, or may be a part of, a wearable device or a vehicle where the vehicle may be terrestrial vehicle, watercraft, or aircraft (including unmanned aerial vehicles). The terminal communication device, therefore, is any fixed, mobile, or portable equipment that performs the functions of the terminal device described herein.

[0017] A parent terminal is a terminal that is connected to a child terminal where the parent terminal is typically closer to the cell of the network node by one hop. The parent terminal, therefore, has one less hop to the network than the child terminal. For example, an intermediate relay terminal is a child terminal of a U2N relay terminal that is Uu connected to the cell of the network node and the U2N relay terminal is parent terminal of the intermediate relay terminal. In another example, a remote terminal is aPCT / US25 / 40849 06 August 2025 (06.08.2025)TUTL 00405 PC-6- child terminal of an intermediate relay terminal and the intermediate relay terminal is parent terminal of the remote terminal.

[0018] An access node is a terminal or a cell that provides access to the network. Accordingly, a cell may be an access node for a terminal. A U2N relay terminal may be an access node as well as an intermediate relay terminal that is (or can) connect to the cell via a U2N relay terminal or via one or more intermediate relay terminals and a U2N relay terminal.

[0019] FIG. 1A is a block diagram of an example of a communication system 100 where a first terminal 102 transmits a first multi-hop discovery announcement 104 and a second terminal 106 transmits a second first multi-hop discovery announcement 108 based on the first multi-hop discovery announcement 104. For the example, the terminals 102, 106 are potential relay terminals in a multi-hop relay communication link 110 that may be established. The terminals 102, 106 form at least a portion of the multihop relay communication link 110, when established, from a third terminal 112 to a cell 114 connected to a network 116. The second terminal 106 is an intermediate relay terminal 106 that is parent terminal to the third terminal 112 and a child terminal to the first terminal 102. Accordingly, the third terminal 112 is a child terminal 112 of the intermediate relay terminal 106, and the first terminal 102 is a parent terminal of the intermediate relay terminal 106. For the example, the first terminal 102 is referred to as the parent terminal 102, and the third terminal is referred to as the child terminal 112.

[0020] The terminals 102, 112 may be different types of terminals depending on where the terminals 102, 106, 112 are positioned within the multi-hop relay communication link 110 and the number of total hops within the multi-hop relay communication link 110. For a first situation 118, the child terminal 112 is a remote terminal, and the parent terminal 102 is another intermediate terminal. For the first situation 118, therefore, the parent terminal 102 may be connected to a last relay terminal that is connected to the cell 114. For the first situation 118, the parent terminal 102 may connected to a third intermediate relay terminal that is connected to a fourth intermediate relay terminal or the last relay terminal. For the second situation 120, the child terminal 112 is a remote terminal, and the parent terminal 102 is the last relay terminal connected to the cell. For a third situation 122, the child terminal 112 is anotherPCT / US25 / 40849 06 August 2025 (06.08.2025)TUTL 00405 PC-7- intermediate relay terminal and the parent terminal 102 is the last relay terminal connected to the cell 114. For the third situation 122, therefore, the child terminal 112 may be connected to third intermediate relay terminal or a remote terminal.

[0021] For the example, the intermediate relay terminal 106 does not transmit the second multi-hop relay discovery announcement 108 unless the intermediate relay terminal 106 has a PC5-S connection 124 to the parent terminal 102. Upon successful PC5-S connection, the two terminals are also assumed to be PC5-RRC connected (for AS layer control). For the examples herein, therefore, the PC5-S and PC5-RRC connections are established before the second multi-hop relay discovery announcement 108 is transmitted. As discussed below, the intermediate relay terminal 106 may autonomously determine to establish the PC5-S connection to the parent terminal in order to transmit the second discovery announcement 108. For example, intermediate relay terminal 106 may determine that is should transmit the second discovery announcement after receiving the first discovery announcement 104 from the parent terminal 102 while the intermediate relay terminal 106 is not PC5-S connected to the parent terminal 102. As a result, the intermediate relay terminal 106 sends a Direct Communication Request (DCR) to initiate the procedure to establish the PC5-S connection to the parent terminal 102.

[0022] In some situations, it may be beneficial for the intermediate relay terminal 106 to be in RRC_CONNECTED before transmitting the discovery announcement. In one example, the intermediate relay terminal 106 autonomously transitions to the RRC_CONNECTED state. In another example, the cell (or network node) transmits a page to the intermediate relay terminal 106 instructing the intermediate relay terminal 106 to transition to RRC_CONNECTED. For example, the last relay terminal may transmit a message to the cell indicating that the intermediate relay terminal 106 is PC5- RRC connected to the last relay terminal. The cell, which is aware of the RRC connection status of the intermediate relay terminal, may transmit a page to the intermediate relay terminal 106 if the intermediate relay terminal 106 is not in RRC_CONNECTED. In such a situation, the last relay terminal may not be aware of the actual RRC connection status of the intermediate relay terminal 106 since the intermediate relay terminal may have experienced a failure that the last relay terminalPCT / US25 / 40849 06 August 2025 (06.08.2025)TUTL 00405 PC-8- has not detected or the cell had sent an RRC Release message to intermediate relay terminal which was delivered transparently to the intermediate relay terminal via the last relay terminal. In other situations, the last relay terminal may be aware of the RRC connection status of the intermediate relay terminal and does not transmit the PC5-RRC status of the intermediate relay terminal to the cell. The last relay not send the PC5- RRC status where the last relay terminal was involved in the connection establishment procedure initiated by the intermediate relay terminal. For example, where the intermediate relay terminal sends an RRCSetupRequest in SL-RLCO to the last relay terminal and the last relay terminal delivers the RRCSetup message from the cell to the intermediate relay terminal, the last relay terminal may determine that the intermediate relay terminal is in RRC CONN and there is no need for the last relay terminal to send the PC5-RRC connection information to the cell.

[0023] FIG. 1 B is a block diagram of an example of a multi-hop relay discovery announcement 150. The multi-hop relay discovery announcement 150 is an example of the first multi-hop relay discovery announcement 104 and the second multi-hop relay discovery announcement 108. For the example, the multi-hop relay discovery announcement 150 includes a hop count field 152, a source layer-2 ID field 154, a destination layer-2 ID field 156, an announcer information field 158, a relay service code (RSC) field 160 and a discovery resource pool field 162. One or more fields may be omitted and additional fields may be included. For example, the discovery resource pool field may be omitted in some situations. In addition, one or more field may be combined into a single field in some situations. The multi-hop relay discovery announcement 150 includes a hop count field. The value of the filed is set to “1” when the announcement is transmitted by the U2N relay terminal (last relay terminal) connected to the cell and is incremented by one by each intermediate relay terminal before retransmission of the discovery announcement. For example, where the intermediate relay terminal 106 of FIG 1A received the first discovery announcement 104 from the last relay terminal, the received discovery announcement has a hop count of “1” and the second discovery announcement 108 transmitted by the intermediate relay terminal 106 has a hop count of 2. If the intermediate relay terminal 106 determines that the incremented value of the hop count exceeds the maximum hop count allowed by the associated relay servicePCT / US25 / 40849 06 August 2025 (06.08.2025)TUTL 00405 PC-9- code, the incoming discovery announcement 104 is not forwarded and, therefore, the intermediate relay terminal 106 does not transmit the second discovery announcement 108.

[0024] The source layer-2 ID field 154 is set to the source Layer-2 ID of the intermediate relay terminal 106. The destination layer-2 ID field 156 is selected based on the configuration and is typically the same Destination Layer-2 ID of the incoming announcement message received by the intermediate relay terminal 106. For Model A discovery, Destination Layer-2 ID is typically used to address the intended recipient(s) and may designate an individual terminal or a group of terminals. The announcer information field 158 provide identify information (i.e., User Info ID) of the announcing intermediate relay terminal 106. The relay service code (RSC) field 160 in the forwarded discovery announcement is the same as the RSC of the received discovery announcement message. Accordingly, the RSC field content in the second discovery announcement 108 is the same as the RSC field content in the first discovery announcement 104.

[0025] The discovery resource pool field 162 includes information identifying the resource pool that should be used for transmitting the multi-hop relay discovery announcements. The contents of the discovery resource pool field 162 in a forwarded discovery announcement is the same in the contents of the discovery resource pool field 162 of the received announcement. The field 162 ensures that the same resource pool is used for the transmission of multi-hop relay discovery announcements.

[0026] In some situations, the U2N relay terminal (last relay terminal) is configured by dedicated signaling to us a specific resource pool. Without any notification, the intermediate relay terminal would use the resource pool based on pre-configuration settings. Where the intermediate relay terminal is out-of-coverage, therefore, different resource pools are likely to be used by the two relay terminals. By identifying the resource pool in the discovery announcement, however, all relay terminals transmitting the discovery announcement use the same resource pool. In another example, the last relay terminal (or other parent terminal) informs the intermediate relay terminal of the selected resource pool via PC5-RRC messaging.PCT / US25 / 40849 06 August 2025 (06.08.2025)TUTL 00405 PC-10-

[0027] FIG. 2 is a block diagram of an example of a base station 200 suitable for use as the network node providing the serving cell 11 . The base station 200 includes a controller 204, transceiver 205 that includes a transmitter 206 and receiver 208, and an antenna 210, as well as other electronics, hardware, and code. The base station 200 is any fixed, mobile, or portable equipment that performs the functions described herein. The various functions and operations of the blocks described with reference to the network nodes providing cells and base station 200 may be implemented in any number of devices, circuits, or elements. Two or more of the functional blocks may be integrated in a single device, and the functions described as performed in any single device may be implemented over several devices. The base station 200 may be a fixed device or apparatus that is installed at a particular location at the time of system deployment. Examples of such equipment include fixed base stations or fixed transceiver stations. Although the base station 200 may be referred to by different terms, the base station 200 is typically referred to as a gNodeB or gNB when operating in accordance with one or more communication specifications of the 3GPP V2X operation. In some situations, the base station 200 may be mobile equipment that is temporarily installed at a particular location. Some examples of such equipment include mobile transceiver stations that may include power generating equipment such as electric generators, solar panels, and / or batteries. Larger and heavier versions of such equipment may be transported by trailer. In still other situations, the base station 200 may be a portable device that is not fixed to any particular location.

[0028] The controller 204 includes any combination of hardware, software, and / or firmware for executing the functions described herein as well as facilitating the overall functionality of the base station 200. An example of a suitable controller 204 includes code running on a microprocessor or processor arrangement connected to memory. The transmitter 206 includes electronics configured to transmit wireless signals. In some situations, the transmitter 206 may include multiple transmitters. The receiver 208 includes electronics configured to receive wireless signals. In some situations, the receiver 208 may include multiple receivers. The receiver 208 may receive signals through multiple antennas or through a selected antenna of a plurality of antennas ofPCT / US25 / 40849 06 August 2025 (06.08.2025)TUTL 00405 PC-11 - the antenna 210. The antenna 210 may include separate transmit and receive antennas or separate arrays in some situations.

[0029] The transmitter 206 and receiver 208 in the example of FIG. 2 perform radio frequency (RF) processing including modulation and demodulation. The receiver 208, therefore, may include components such as low noise amplifiers (LNAs) and filters. The transmitter 206 may include filters and amplifiers. Other components may include isolators, matching circuits, and other RF components. These components in combination or cooperation with other components perform the base station functions. The required components may depend on the particular functionality required by the base station.

[0030] The transmitter 206 includes a modulator (not shown), and the receiver 208 includes a demodulator (not shown). The modulator modulates the signals to be transmitted as part of the downlink signals and can apply any one of a plurality of modulation orders. The demodulator demodulates any uplink signals received at the base station 200 in accordance with one of a plurality of modulation orders.

[0031] The base station 200 includes a communication interface 212 for transmitting and receiving messages with other base stations such as the network nodes providing target cells and / candidate target cells. The communication interface 212 may be connected to a backhaul or network enabling communication with other base stations. In some situations, the link between base stations may include at least some wireless portions. The communication interface 212, therefore, may include wireless communication functionality and may utilize some of the components of the transmitter 206 and / or receiver 208.

[0032] FIG. 3 is a block diagram of an example of a UE device 300 suitable for use as each of the terminals including remote terminal and relay terminals, such as the parent terminal 102, the intermediate relay terminal 106, the child terminal 112, the remote terminal, and another other intermediate relay terminals. In some examples, the UE device 300 is any wireless communication device such as a mobile phone, a transceiver modem, a personal digital assistant (PDA), a tablet, or a smartphone. In other examples, the UE device 300 is a machine type communication (MTC)PCT / US25 / 40849 06 August 2025 (06.08.2025)TUTL 00405 PC-12- communication device or Internet-of-Things (IOT) device. The UE device 300, therefore is any fixed, mobile, or portable equipment that performs the functions described herein. The various functions and operations of the blocks described with reference to UE device 300 may be implemented in any number of devices, circuits, or elements. Two or more of the functional blocks may be integrated in a single device, and the functions described as performed in any single device may be implemented over several devices.

[0033] The UE device 300 includes at least a controller 302, a transmitter 304, and a receiver 306. The controller 302 includes any combination of hardware, software, and / or firmware for executing the functions described herein as well as facilitating the overall functionality of a communication device. An example of a suitable controller 302 includes code running on a microprocessor or processor arrangement connected to memory 310. The transmitter 304 includes electronics configured to transmit wireless signals. In some situations, the transmitter 304 may include multiple transmitters. The receiver 306 includes electronics configured to receive wireless signals. In some situations, the receiver 306 may include multiple receivers. The receiver 306 and transmitter 304 receive and transmit signals, respectively, through the antenna 308. The antenna 308 may include separate transmit and receive antennas. In some circumstances, the antenna 308 may include multiple transmit and receive antennas.

[0034] The transmitter 304 and receiver 306 in the example of FIG. 3 perform radio frequency (RF) processing including modulation and demodulation. The receiver 306, therefore, may include components such as low noise amplifiers (LNAs) and filters. The transmitter 304 may include filters and amplifiers. Other components may include isolators, matching circuits, and other RF components. These components in combination or cooperation with other components perform the communication device functions. The required components may depend on the particular functionality required by the communication device.

[0035] The transmitter 304 includes a modulator (not shown), and the receiver 306 includes a demodulator (not shown). The modulator can apply any one of a plurality of modulation orders to modulate the signals to be transmitted as part of the uplink signals. The demodulator demodulates the downlink signals in accordance with one of a plurality of modulation orders.PCT / US25 / 40849 06 August 2025 (06.08.2025)TUTL 00405 PC-13-

[0036] The UE device 300 is capable of transmitting and receiving sidelink signals to and from other UE devices as well as communicating with a base station. The controller 302, in conjunction with the receiver 306, measures signals, such as discovery signals, transmitted by nearby UE devices to generate the neighbor list that includes neighbor UE devices within the maximum distance. The neighbor list is stored in the memory 310 and transmitted to the base station 106 when the UE device 300 is a reporting UE device. The receiver 306 and controller 302 also measure signals transmitted by the base station to determine the wide-beam precoder and the UE-specific precoder information.

[0037] FIG. 4 is a message flow diagram 400 for an example where an intermediate relay terminal 106 establishes an PC5-S connection with a parent terminal 102 before forwarding a multi-hop relay discovery announcement received from the parent terminal 102. For the example, the parent terminal 102 the last relay terminal connected to the cell 114 and the child terminal 112 is remote terminal. The example begins with the intermediate terminal without a PC5-S or PC5-RRC connection to the parent terminal 102.

[0038] At transmission 402, the parent terminal (last relay terminal) 102 transmits a multi-hop relay discovery message (discovery announcement) that is received by the intermediate relay terminal 106. For the example, the discovery announcement message has a configuration and structure as discussed with the example of FIG. 1 B.

[0039] At event 404, the intermediate relay terminal 106 determines that the discovery announcement should be forwarded to other terminals. The intermediate relay terminal 106 determines whether it is authorized to act as a relay UE for the specific RSC that is received in the incoming discovery announcement. The intermediate relay terminal further evaluates whether it can support one more hop for discovery transmission based on the maximum number of hops supported by the intermediate relay terminal. For the example, the intermediate relay terminal supports the RSC and the hop count of the incoming discovery announcement is “1” where the intermediate relay terminal supports more than “1” hop.PCT / US25 / 40849 06 August 2025 (06.08.2025)TUTL 00405 PC-14-

[0040] At transmission 406, the intermediate relay terminal 106 sends a direct communication request (DCR) to the parent terminal 102. At transmission 408, the parent terminal 102 sends a direct communication acknowledgement (DCA) to the intermediate relay terminal 106. The transmissions 406, 408 are performed in accordance with known techniques and standards to the establish the PC5-S between the intermediate relay terminal 106 and the parent terminal 102. At event 410, the intermediate relay terminal 106 and the parent terminal 102 are PC5-S / PC5-RRC connected.

[0041] In some situations, the intermediate relay terminal 106 transitions to the RRC- CONNECTED state before forwarding the discovery announcements. The transition is optional and the terminal may remain in a non-RRC_CONNECTED state (i.e. , IDLE or INACTIVE) when forwarding the discovery announcement. Accordingly, the transmissions 412, 414, 416 to transition the intermediate relay terminal 106 to RRC_CONNECTED can be omitted in some situations. One advantage of having the intermediate relay terminal in the RRC-CONNECTED state when discovery is transmitted is a reduced latency when the child terminal in IDLE or INACTIVE attempts to connect to the cell through the intermediate relay terminal. In such situations in conventional systems, the intermediate relay terminal must first transition to RRC- CONNECTED before transmitting messages for transitioning the child terminal to RRC_CONNECTED. By transitioning to RRC_CONNECTED before transmitting the discovery message, the intermediate relay terminal can more quickly address the messaging for the child terminal transition to RRC CONNECTED when initiated.Another advantage may be realized during path-switch when the target relay UE is already in RRC CONN, the path switch can be completed with little delay and will have less chance for experiencing PC5-RLF in any of the links before connection on the new path can be established.

[0042] At transmission 412, the intermediate relay terminal 106 sends an RRC Setup Request to the cell 414 via the parent terminal 102. At transmission 414, the parent terminal 102 sends an RRC Setup message to the intermediate relay terminal 106. At transmission 416, the intermediate relay terminal 106 sends an RRC Setup CompletePCT / US25 / 40849 06 August 2025 (06.08.2025)TUTL 00405 PC-15- message to the cell 11 completing the transition of the intermediate relay terminal to RRC-CONNECTED at event 418.

[0043] At transmission 420, the intermediate relay terminal 106 transmits a multi-hop relay discovery message (discovery announcement) that is based on the discovery announcement received from the parent terminal 102. For the example, the discovery announcement message has a configuration and structure as discussed with the example of FIG. 1 B. The intermediate relay terminal increments the hop count and generates the discovery announcement before transmission the discovery announcement to nearby terminals. The child terminal 112 receives the discovery announcement which may be used to perform relay selection to establish the multi-hop relay communication link 110.

[0044] FIG. 5 is a flow chart of an example of method of transmitting multi-hop relay discovery messages (discovery announcements). The method may be performed in a system such as the system 100 discussed herein. For the example, the method is performed by a terminal that may be selected to perform the functions of an intermediate relay terminal, such as the intermediate relay terminal 106. The method may be performed using any of several techniques involving any combination of software, hardware, and firmware. For example, software code running on electronics including a processor, computer or other processor arrangement within the terminal may facilitate the generation, formatting, reception and transmission of signals and messages. One or more of the steps may be omitted, combined, performed in parallel, or performed in a different order than that described herein or shown in FIG. 5. In still further examples, additional steps may be added that are not explicitly described in connection with the example discussed with reference to FIG. 5.

[0045] At step 502, the intermediate relay terminal receives a multi-hop relay discovery message (discovery announcement) from its parent terminal. The parent terminal may be a U2N relay terminal in some situations.

[0046] At step 504, the intermediate relay terminal determines whether the discovery message should be forwarded. For the example, the intermediate relay terminal evaluates hop count and a maximum allowable hop count the intermediate relayPCT / US25 / 40849 06 August 2025 (06.08.2025)TUTL 00405 PC-16- terminal can support and RSC indicated in the received discovery message to determine whether the discovery message should be forwarded. For example, if the intermediate relay terminal 106 determines that the incremented value of the hop count exceeds the maximum hop count allowed by the associated relay service code, the incoming discovery announcement 104 is not forwarded and, therefore, the intermediate relay terminal 106 does not transmit the second discovery announcement 108. In one example, the intermediate relay terminal evaluates signaling related to the application layer and that application layer signaling indicates the max number of hops for the RSC. The intermediate relay terminal then determines whether the max hops associated with the specific RSC indicated in the received discovery announcement is less than the hop count in the received discovery announcement plus 1 . If the message is not to be forwarded, the method returns to step 502. Otherwise, the method proceeds to step 506.

[0047] At step 506, the intermediate relay terminal 106 determines whether it is PC5- S connected to its parent terminal. If the intermediate relay terminal 106 is not PC5-S connected to its parent terminal, the intermediate relay terminal 106 establishes the PC5-S connection at step 508. Otherwise, the method precedes to step 510

[0048] At step 510, the intermediate relay terminal 106 determines whether it is in the RRC_CONNECTED state with its serving cell. If the intermediate relay terminal is not in RRC_CONNECTED, the method proceeds to step 512. Otherwise, the method proceeds to step 514.

[0049] At step 512, the intermediate relay terminal 106 establishes the RRC_CONNECTED state with the serving cell. Therefore, if the intermediate relay terminal 106 is in RRCJNACTIVE or RRCJDLE, the intermediate relay terminal transmits an RRC connection request to the serving cell through its parent terminal. After receiving the RRC Setup message from the serving cell via the parent terminal, the intermediate relay terminal sends an RRC complete message to establish RRC_CONNECTED. Steps 510 and 512 are optional and may be omitted in some situations.

[0050] At step 514, the intermediate relay terminal 106 generates a multi hop relay discovery message based on the received multi-hop relay discovery message.PCT / US25 / 40849 06 August 2025 (06.08.2025)TUTL 00405 PC-17-Accordingly, a second discovery announcement is generated based on the first discovery announcement where the information in the first discovery message is included in the second discovery message with the hop count incremented by one.

[0051] At step 516, the second multi-hop discovery message is transmitted. The broadcasted multi-hop discovery message may be received by one or more child terminals and used to establish multi-hop relay links through the intermediate relay terminal. In some situations, the parent relay terminal may provide a relay discovery resource pool that is to be used for the transmission of relay discovery messages. The relay discovery resource pool may be identifying in the first discovery announcement. In another example, the last relay terminal (or other parent terminal) informs the intermediate relay terminal of the selected resource pool via PC5-RRC messaging.

[0052] To clearly illustrate this interchangeability of hardware, firmware 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, firmware or software, or a combination of these techniques, depends upon the particular application and design constraints imposed on the overall system. The described functionality may be implemented in various ways for each particular application, but such implementation decisions do not cause a departure from the scope of the present disclosure. In accordance with various embodiments, a processor, device, component, circuit, structure, machine, module, etc. can be configured to perform one or more of the functions described herein. The term "configured to" or "configured for" as used herein with respect to a specified operation or function refers to processors, devices, components, circuits, electronics, and equipment that are physically constructed, programmed, instructed and / or arranged to perform the specified operation or function. Furthermore, the various illustrative logical blocks, modules, devices, components and circuits described herein can be implemented within or performed by an integrated circuit (IC) that can include a general-purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), other electronics or combinations thereof. (ASIC), a field programmable gate array (FPGA) or other programmable logic device, or any combination thereof. The logical blocks, electronics, and circuits can further include antennas and / or transceivers toPCT / US25 / 40849 06 August 2025 (06.08.2025)TUTL 00405 PC-18- communicate with various components within the network or within the device. A general-purpose processor can be a microprocessor, but in the alternative, the processor can be any conventional processor, controller, or state machine. A processor can also be implemented as a combination of computing devices, e.g., 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 suitable configuration to perform the functions described herein.

[0053] When implemented in software, the functions can be stored as one or more instructions or code on a computer-readable medium. Thus, the steps of a method or algorithm disclosed herein can be implemented as software stored on a computer- readable medium. Computer readable media includes both computer storage media and communication media including any medium that can be enabled to transfer a computer program or code from one place to another. A storage media can be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer.

[0054] Therefore, the methods and apparatus of this invention may take the form, at least partially, of program logic or program code (i.e. , instructions) embodied in tangible media, such as a machine-readable storage medium. When the program code is loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the invention. The methods and apparatus of the present invention may also be embodied in the form of program code that is transmitted over some transmission medium, such as over electrical wiring or cabling, through fiber optics, or via any other form of transmission. When the program code is received and loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the invention. When implemented on a general-purpose processor, the program code combines with the processor to provide a unique apparatus that operates analogously to specific logic circuits.PCT / US25 / 40849 06 August 2025 (06.08.2025)TUTL 00405 PC-19-

[0055] Additionally, memory or other storage, as well as communication components, may be employed in embodiments of the present disclosure. It will be appreciated that, for clarity purposes, the above description has described embodiments of the present disclosure with reference to different functional units and processors. However, it will be apparent that any suitable distribution of functionality between different functional units, processing logic elements or domains may be used without detracting from the present disclosure. For example, functionality illustrated to be performed by separate processing logic elements, or controllers, may be performed by the same processing logic element, or controller. Therefore, references to specific functional units are only references to a suitable means for providing the described functionality, rather than indicative of a strict logical or physical structure or organization.

[0056] Clearly, other embodiments and modifications of this invention will occur readily to those of ordinary skill in the art in view of these teachings. The above description is illustrative and not restrictive. This invention is to be limited only by the following claims, which include all such embodiments and modifications when viewed in conjunction with the above specification and accompanying drawings. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents.

Claims

PCT / US25 / 40849 06 August 2025 (06.08.2025)TUTL 00405 PC-20-CLAIMS1 . A method comprising: receiving, at an intermediate relay terminal, a first multi-hop relay discovery message from a parent relay terminal; determining, at the intermediate relay terminal, to transmit a second multi-hop relay discovery message based on the first multi-hop relay discovery message; establishing a PC5-S connection with the parent relay terminal; transmitting, after the PC5-S connection is established, the second multi-hop relay discovery message.

2. The method of claim 1 , further comprising: establishing a Radio Resource Control (RRC) connection with a cell of a network node through the relay terminal to transition to an RRC_CONNECTED state before transmitting the second multi-hop relay discovery message.

3. The method of claim 2, wherein establishing the RRC connection with the cell of the network node comprises: sending an RRC Setup Request to the network node through the parent relay terminal; and receiving an RRC Setup response from the network node through the parent relay terminal.

4. The method of claim 3, wherein establishing the RRC connection with the cell comprises: sending the RRC Setup Request message in response to receiving a page from the network node through the parent relay terminal.

5. The method of claim 4, wherein the page is transmitted from the network node in response to a notification, from the parent terminal, indicating a PC5-RRC connection status between the intermediate relay terminal and the parent terminal, the parentPCT / US25 / 40849 06 August 2025 (06.08.2025)TUTL 00405 PC-21 - terminal being a last relay terminal connected to cell in a multi-hop relay communication link between the child terminal and the cell.

6. The method of claim 1 , wherein the determining to transmit the second multi-hop relay discovery message comprises: evaluating a hop count indicator in the first multi-hop relay discovery signal and a maximum allowable hop count for the intermediate relay terminal.

7. The method of claim 6, wherein the determining to transmit the second multi-hop relay discovery message further comprises: evaluating relay service code (RSC) in the first multi-hop discovery message and RSC capabilities of the intermediate relay terminal.

8. The method of claim 1 , further comprising: receiving, at the intermediate relay terminal, a relay discovery resource pool indicator from the parent relay terminal, the relay discovery resource pool indicator indicating a pool of resources for transmitting relay discovery signals; and transmitting the second relay discovery signal using an intermediate relay terminal selected resource from the pool of resources for transmitting relay discovery signals.

9. The method of claim 8, wherein the first relay discovery signal is transmitted from the relay terminal using a relay terminal selected resource from the pool of resources for transmitting relay discovery signals, the relay discovery resource pool indicator received at the parent relay terminal from the network node.

10. The method of claim 7, wherein the first multi-hop relay discovery message comprises the discovery relay discovery resource pool indicator.11 . The method of claim 8, wherein the discovery relay discovery resource pool indicator is received from the parent relay terminal in a PC5-RRC message.PCT / US25 / 40849 06 August 2025 (06.08.2025)TUTL 00405 PC-22-12. An intermediate relay terminal comprising: a receiver configured to receive a first multi-hop relay discovery message from a parent relay terminal; controller configured to determine to transmit a second multi-hop relay discovery message based on the first multi-hop relay discovery message and to establish a PC5- S connection with the parent relay terminal; and a transmitter configured to transmit, after the PC5-S connection is established, the second multi-hop relay discovery message.

13. A method comprising: receiving, at an intermediate relay terminal, a first multi-hop relay discovery message from a parent relay terminal; receiving, at the intermediate relay terminal, a relay discovery resource pool indicator from the parent relay terminal, the relay discovery resource pool indicator indicating a pool of resources for transmitting relay discovery signals; transmitting a second relay discovery signal using an intermediate relay terminal selected resource from the pool of resources for transmitting relay discovery signals, the second multi-hop relay discovery message based on the first multi-hop relay discovery message.

14. The method of claim 13, wherein the first relay discovery signal is transmitted from the relay terminal using a relay terminal selected resource from the pool of resources for transmitting relay discovery signals, the relay discovery resource pool indicator received at the parent relay terminal from the network node.

15. The method of claim 13, wherein the first multi-hop relay discovery message comprises the discovery relay discovery resource pool indicator.

16. The method of claim 15, wherein the second multi-hop relay discovery message comprises the discovery relay discovery resource pool indicator.PCT / US25 / 40849 06 August 2025 (06.08.2025)TUTL 00405 PC-23-17. The method of claim 13, wherein the discovery relay discovery resource pool indicator is received from the parent relay terminal in a PC5-RRC message.

18. The method of claim 13, wherein the first multi-hop relay discovery message comprises a first hop count indictor indicating a number of relay hops from the parent terminal to a serving cell.

19. The method of claim 18, further comprising generating the second relay discovery signal comprising a second hop count indicator indicating a number of relay hops from the intermediate relay terminal to the serving cell, the second hop count indicator equal to the first hop count indicator incremented by 1 .

20. An intermediate relay terminal comprising: a receiver configured to receive a first multi-hop relay discovery message from a parent relay terminal and to receive a relay discovery resource pool indicator from the parent relay terminal, the relay discovery resource pool indicator indicating a pool of resources for transmitting relay discovery signals; and a transmitted configured to transmit a second relay discovery signal using an intermediate relay terminal selected resource from the pool of resources for transmitting relay discovery signals, the second multi-hop relay discovery message based on the first multi-hop relay discovery message.

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