# US 12,764,627 B2 · Relay communication management in response to cellular connection radio link failure (RLF) > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,764,627 B2 - Document ID: US12764627B2 - Status: Granted - Kind: B2 - Application number: 18/287,443 - Filed: 2022-05-06 - Published: 2024-06-27 - Granted: 2026-10-13 - Earliest claimed: 2021-05-10 - Assignees: KYOCERA Corporation - Applicants: Kyocera Corporation; Henry Chang; Masato Fujishiro - Inventors: Henry Chang; Masato Fujishiro - Web page: https://patentgrep.com/patent/US12764627B2 ## CPC - H04W 36/305: {Handover due to radio link failure (control signalling for hand-off failure H04W36/0079)} - H04W 36/033: {in pre-organised networks} - H04W 40/22: using selective relaying for reaching a BTS [Base Transceiver Station] or an access point - H04W 88/04: adapted for relaying to or from another terminal or user - H04W 92/18: between terminal devices - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract An initial relay user equipment (UE) device transmits a llu radio link failure (RLE) notification to a remote UE device when the Uu communication link from the initial relay UE device to the serving base station fails. The remote UE device refrains from sending signals to the serving base station through the initial relay UE device at least until receiving a Uu link reestablished notification indicating that the Uu communication link has been reestablished. In some situations, the remote UE device identifies a preferred candidate relay UE device after receiving the Uu RLF notification and selects the preferred candidate relay UE device for relay communication in response to receiving a Uu link reestablished notification indicating the Uu communication link could not be reestablished. ## Claims ### Claim 1 A remote user equipment device (UE) comprising: a transceiver comprising a transmitter and a receiver, the transceiver configured to communicate with a base station through an initial relay UE device that is communicating with the base station over a Uu communication link; a controller configured to determine that a radio link failure (RLF) of the Uu communication link has occurred; the receiver configured to receive a link re-establishment notification indicating whether the Uu communication link has been re-established; the transmitter configured to: in response to the determination of the occurrence of the RLF, refrain from transmitting signals to the base station, in response to the receiver receiving the link re-establishment notification indicating the Uu communication link has been re-established, transmit a signal to the base station. ### Claim 2 (depends on 1) The remote UE device of claim 1, wherein the receiver is further configured to receive a RLF notification indicating the RLF has occurred and wherein the controller is configured to determine that the Uu RLF has occurred based on the RLF notification. ### Claim 3 (depends on 2) The remote UE device of claim 2, wherein the controller is further configured to: in response to the determination that the RLF of the Uu communication link has occurred, perform a relay reselection procedure. ### Claim 4 (depends on 3) The remote UE device of claim 3, wherein the relay reselection procedure establishes an alternate relayed connection through an alternate relay UE device to the base station, the transmitter configured to send an RRC reestablishment request to the base station after the alternate relayed connection has been established, the RRC reestablishment request comprising an RLF indicator indicating a cause of a failure of an initial relayed connection to the base station through the initial relay UE device. ### Claim 5 (depends on 4) The remote UE device of claim 4, wherein the RLF indicator indicates one of a PC5 RLF and a Uu RLF. ### Claim 6 (depends on 2) The remote UE device of claim 2, wherein the controller is further configured to: in response to the receiver receiving the link re-establishment notification indicating the Uu communication link could not be re-established, perform a relay reselection procedure. ### Claim 7 (depends on 6) The remote UE device of claim 6, wherein the relay reselection procedure establishes an alternate relayed connection through an alternate relay UE device to the base station, the transmitter configured to send an RRC reestablishment request to the base station after the alternate relayed connection has been established, the RRC reestablishment request comprising an RLF indicator indicating a cause of a failure of an initial relayed connection to the base station through the initial relay UE device. ### Claim 8 (depends on 7) The remote UE device of claim 7, wherein the RLF indicator indicates one of a PC5 RLF and a Uu RLF. ### Claim 9 (depends on 6) The remote UE device of claim 6, wherein: the receiver is configured to receive a first radio resource control (RRC) connection status notification indicating a current connection status of a first candidate relay UE device to a base station; the receiver is configured to receive a second RRC connection status notification indicating a current connection status of a second candidate relay UE device to the base station; and the controller is configured to perform the relay reselection procedure to identify a preferred candidate relay UE device, from the first candidate relay UE device and the second candidate relay UE device, based at least partially on the first RRC connection status notification and the second RRC connection status notification. ### Claim 10 (depends on 9) The remote UE device of claim 9, wherein the first RRC connection status notification is received in a first discovery message from the first candidate relay UE device and the second RRC connection status notification is received in a second discovery message from the second candidate relay UE device. ### Claim 11 (depends on 10) The remote UE device of claim 10, wherein each of the first RRC connection status notification and the second RRC connection status notification is indicative of one of a plurality of RRC connected states comprising connected (RRC CONN), idle (RRC IDLE), or inactive (RRC INACTIVE). ### Claim 12 (depends on 2) The remote UE device of claim 2, wherein the controller is further configured to: in response to receiving the RLF notification, identify a preferred candidate relay UE device and, in response to the receiver receiving the link reestablishment notification indicating the Uu communication link could not be reestablished, selecting the preferred candidate relay UE device for communication to the base station. ### Claim 13 (depends on 12) The remote UE device of claim 12, wherein the controller is further configured to select the preferred candidate relay UE device to establish an alternate relayed connection through the preferred candidate relay UE device to the base station, the transmitter configured to send an RRC reestablishment request to the base station after the alternate relayed connection has been established, the RRC reestablishment request comprising an RLF indicator indicating a cause of a failure of an initial relayed connection to the base station through the initial relay UE device. ### Claim 14 (depends on 13) The remote UE device of claim 13 wherein the RLF indicator indicates one of a PC5 RLF and a Uu RLF. ### Claim 15 (depends on 12) The remote UE device of claim 12, wherein: the receiver is configured to receive a first radio resource control (RRC) connection status notification indicating a current connection status of a first candidate relay UE device to a base station; the receiver is configured to receive a second RRC connection status notification indicating a current connection status of a second candidate relay UE device to the base station; and the controller is configured to identify the preferred candidate relay UE device, from the first candidate relay UE device and the second candidate relay UE device, based at least partially on the first RRC connection status notification and the second RRC connection status notification. ### Claim 16 (depends on 15) The remote UE device of claim 15, wherein the first RRC connection status notification is received in a first discovery message from the first candidate relay UE device and the second RRC connection status notification is received in a second discovery message from the second candidate relay UE device. ### Claim 17 (depends on 16) The remote UE device of claim 16, wherein each of the first RRC connection status notification and the second RRC connection status notification is indicative of one of a plurality of RRC connected states comprising connected (RRC CONN), idle (RRC IDLE), or inactive (RRC INACTIVE).