# US 2021/0243748 A1 · Sidelink beam failure detection > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0243748 A1 - Document ID: US20210243748A1 - Status: Published application - Kind: A1 - Application number: 17/248,162 - Filed: 2021-01-12 - Published: 2021-08-05 - Earliest claimed: 2020-02-03 - Assignees: QUALCOMM Incorporated - Applicants: QUALCOMM Incorporated - Inventors: Jung Ho RYU; Ling DING; Sony AKKARAKARAN; Kiran VENUGOPAL; Tianyang BAI; Junyi LI; Tao LUO - Web page: https://patentgrep.com/patent/US20210243748A1 ## CPC - H04B 7/06964: {Re-selection of one or more beams after beam failure} - H04B 7/0408: using two or more beams, i.e. beam diversity - H04B 7/088: {using beam selection} - H04L 5/0023: {Time-frequency-space} - H04W 16/28: using beam steering - H04W 72/046: {the resource being in the space domain, e.g. beams} - H04L 5/0048: {Allocation of pilot signals, i.e. of signals known to the receiver (allocation of control signalling H04L5/0053; use of control signalling H04L5/0091)} - H04W 4/40: for vehicles, e.g. vehicle-to-pedestrians [V2P] - H04W 24/08: Testing, {supervising or monitoring} using real traffic - H04W 76/14: Direct-mode setup - H04W 76/19: Connection re-establishment - H04W 92/18: between terminal devices - H04B: TRANSMISSION - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a first node may transmit, to a second node on a beamformed link from the first node to the second node, a first signal, wherein the first node and the second node are associated with common timing; determine whether a second signal, based at least in part on the first signal, is received on a beamformed link from the second node to the first node; and transmit a third signal based at least in part on receiving the second signal or perform a sidelink beam failure recovery procedure based at least in part on determining that the second signal is not received. Numerous other aspects are provided. ## Claims ### Claim 1 A first node for wireless communication, comprising: a memory; and one or more processors operatively coupled to the memory, the memory and the one or more processors configured to: transmit, to a second node on a beamformed link from the first node to the second node, a first signal, wherein the first node and the second node are associated with common timing; determine whether a second signal, based at least in part on the first signal, is received on a beamformed link from the second node to the first node; and transmit a third signal on the beamformed link from the first node to the second node based at least in part on receiving the second signal; or perform a sidelink beam failure recovery procedure based at least in part on determining that the second signal is not received. ### Claim 2 (depends on 1) The first node of claim 1, wherein at least one of the first signal, the second signal, or the third signal comprise channel state information reference signals. ### Claim 3 (depends on 1) The first node of claim 1, wherein the first signal, the second signal, and the third signal are associated with respective resource allocations that are known to the first node and the second node before transmission of the first signal. ### Claim 4 (depends on 3) The first node of claim 3, wherein the respective resource allocations are determined by one or more of the first node or the second node. ### Claim 5 (depends on 3) The first node of claim 3, wherein the respective resource allocations are determined by a base station associated with the first node or the second node. ### Claim 6 (depends on 1) The first node of claim 1, wherein the beamformed link from the first node to the second node and the beamformed link from the second node to the first node are a same link. ### Claim 7 (depends on 1) The first node of claim 1, wherein the common timing is determined based at least in part on a base station associated with the first node and the second node. ### Claim 8 (depends on 1) The first node of claim 1, wherein the common timing is determined based at least in part on positioning systems of the first node and the second node. ### Claim 9 (depends on 1) The first node of claim 1, wherein the beamformed link from the first node to the second node and the beamformed link from the second node to the first node are associated with a ProSe sidelink interface. ### Claim 10 (depends on 1) The first node of claim 1, wherein the first node and the second node comprise user equipment. ### Claim 11 (depends on 1) The first node of claim 1, wherein the first node and the second node comprise integrated access and backhaul nodes. ### Claim 12 (depends on 1) The first node of claim 1, wherein the one or more processors, when performing the sidelink beam failure recovery procedure, are configured to perform the sidelink beam failure recovery procedure based at least in part on failing to receive the second signal a threshold number of times. ### Claim 13 A second node for wireless communication, comprising: a memory; and one or more processors operatively coupled to the memory, the memory and the one or more processors configured to: determine whether a first signal is received from a first node on a beamformed link from the first node to the second node, wherein the first node and the second node are associated with common timing; determine whether to transmit, on a beamformed link from the second node to the first node, a second signal based at least in part on whether the first signal is received; and receive a third signal based at least in part on the second signal; or perform a sidelink beam failure recovery procedure based at least in part on failing to receive the first signal or the third signal. ### Claim 14 (depends on 13) The second node of claim 13, wherein the one or more processors are further configured to transmit the second signal based at least in part on receiving the first signal. ### Claim 15 (depends on 13) The second node of claim 13, wherein the beamformed link from the first node to the second node and the beamformed link from the second node to the first node are a same link. ### Claim 16 (depends on 13) The second node of claim 13, wherein the beamformed link from the first node to the second node and the beamformed link from the second node to the first node are associated with a ProSe sidelink interface. ### Claim 17 (depends on 13) The second node of claim 13, wherein the one or more processors, when performing the sidelink beam failure recovery procedure, are configured to: perform the sidelink beam failure recovery procedure based at least in part on failing to receive one or more of the first signal or the third signal a threshold number of times. ### Claim 18 A method of wireless communication performed by a first node, comprising: transmitting, to a second node on a beamformed link from the first node to the second node, a first signal, wherein the first node and the second node are associated with common timing; determining whether a second signal, based at least in part on the first signal, is received on a beamformed link from the second node to the first node; and transmitting a third signal on the beamformed link from the first node to the second node based at least in part on receiving the second signal; or performing a sidelink beam failure recovery procedure based at least in part on determining that the second signal is not received. ### Claim 19 (depends on 18) The method of claim 18, wherein at least one of the first signal, the second signal, or the third signal comprise channel state information reference signals. ### Claim 20 (depends on 18) The method of claim 18, wherein the first signal, the second signal, and the third signal are associated with respective resource allocations that are known to the first node and the second node before transmission of the first signal. ### Claim 21 (depends on 18) The method of claim 18, wherein the beamformed link from the first node to the second node and the beamformed link from the second node to the first node are a same link. ### Claim 22 (depends on 18) The method of claim 18, wherein the beamformed link from the first node to the second node and the beamformed link from the second node to the first node are associated with a ProSe sidelink interface. ### Claim 23 (depends on 18) The method of claim 18, wherein performing the sidelink beam failure recovery procedure further comprises performing the sidelink beam failure recovery procedure based at least in part on failing to receive the second signal a threshold number of times. ### Claim 24 A method of wireless communication performed by a second node, comprising: determining whether a first signal is received from a first node on a beamformed link from the first node to the second node, wherein the first node and the second node are associated with common timing; determining whether to transmit, on a beamformed link from the second node to the first node, a second signal based at least in part on whether the first signal is received; and receiving a third signal based at least in part on the second signal; or performing a sidelink beam failure recovery procedure based at least in part on failing to receive the first signal or the third signal. ### Claim 25 (depends on 24) The method of claim 24, further comprising transmitting the second signal based at least in part on receiving the first signal. ### Claim 26 (depends on 24) The method of claim 24, wherein the beamformed link from the first node to the second node and the beamformed link from the second node to the first node are a same link. ### Claim 27 (depends on 24) The method of claim 24, wherein the beamformed link from the first node to the second node and the beamformed link from the second node to the first node are associated with a ProSe sidelink interface. ### Claim 28 (depends on 24) The method of claim 24, wherein the first node and the second node comprise user equipment. ### Claim 29 (depends on 24) The method of claim 24, wherein the first node and the second node comprise integrated access and backhaul nodes. ### Claim 30 (depends on 24) The method of claim 24, wherein performing the sidelink beam failure recovery procedure further comprises: performing the sidelink beam failure recovery procedure based at least in part on failing to receive one or more of the first signal or the third signal a threshold number of times.