# US 11,445,425 B2 · Beam failure recovery mechanism > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,445,425 B2 - Document ID: US11445425B2 - Status: Granted - Kind: B2 - Application number: 17/171,523 - Filed: 2021-02-09 - Published: 2021-08-26 - Granted: 2022-09-13 - Earliest claimed: 2020-02-21 - Assignees: Nokia Technologies Oy - Applicants: Nokia Technologies Oy - Inventors: Timo Koskela; Samuli Turtinen; Chunli Wu - Web page: https://patentgrep.com/patent/US11445425B2 ## CPC - H04W 36/305: {Handover due to radio link failure (control signalling for hand-off failure H04W36/0079)} - H04B 7/0639: {Using selective indices, e.g. of a codebook, e.g. pre-distortion matrix index [PMI] or for beam selection} - H04B 7/06964: {Re-selection of one or more beams after beam failure} - H04W 36/06: Reselecting a communication resource in the serving access point - H04W 36/10: Reselecting an access point controller - H04W 74/0833: Random access procedures, e.g. with 4-step access - H04W 74/0838: using contention-free random access [CFRA] - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) - H04B: TRANSMISSION ## Abstract Example embodiments of the present disclosure relate to beam failure recovery mechanism. According to embodiments of the present disclosure, there are provided an improved solution for reporting candidate beams in serving cells. If a beam failure occurs in a serving cell, the first device determines a candidate beam for beam failure recovery from a plurality of beams in the serving cell based on link qualities of the plurality of beams. The first device also determines a resource configuration for a random access for the beam failure recovery for the first device or a resource to be used for the random access, The first device further generates an indication for indicating a characteristic of the candidate beam or a characteristic of a beam for performing the random access, based on at least one of the determined resource configuration or the determined resource. The first device also transmits an identity of the candidate beam and the indication to a second device. The second device performs the beam failure recovery based on the candidate beam and the characteristic of the candidate beam. ## Claims ### Claim 1 A first device, comprising: at least one processor; and at least one memory including computer program codes; the at least one memory and the computer program codes are configured to, with the at least one processor, cause the first device to: in accordance with a determination that a beam failure occurs in a special cell, initiate a contention-based random access procedure for beam failure recovery of the special cell; indicate by the first device a candidate beam for beam failure recovery of the special cell to a second device via a preamble during the contention-based random access procedure; include an indication for indicating the beam failure for the special cell into a media access control (MAC) control element (CE); and transmit the MAC CE to the second device via a Msg. 3 during the contention-based random access procedure; wherein the special cell comprises a primary cell or a primary secondary cell, and wherein the MAC CE omits information related to the candidate beam for beam failure recovery of the special cell. ### Claim 2 (depends on 1) The first device of claim 1, where the MAC CE includes a bitmap indicating beam failure detection for the special cell and at least one secondary cell. ### Claim 3 (depends on 1) The first device of claim 1, wherein the MAC CE includes a field indicating candidate beam related information for at least one secondary cell. ### Claim 4 (depends on 1) The first device of claim 1, wherein the omitted information related to the candidate beam comprises a candidate availability indication and a candidate reference signal index for the special cell. ### Claim 5 A method for communication, comprising: in accordance with a determination that a beam failure occurs in a special cell, initiating, by a first device, a contention-based random access procedure for beam failure recovery of the special cell; indicate by the first device a candidate beam for beam failure recovery of the special cell to a second device via a preamble during the contention-based random access procedure; including, by the first device, an indication for indicating the beam failure for the special cell into a media access control (MAC) control element (CE); and transmitting, by the first device, the MAC CE to the second device via a Msg. 3 during the contention-based random access procedure; wherein the special cell comprises a primary cell or a primary secondary cell, and wherein the MAC CE omits information related to the candidate beam for beam failure recovery of the special cell. ### Claim 6 (depends on 5) The method of claim 5, where the MAC CE includes a bitmap indicating beam failure detection for the special cell and at least one secondary cell. ### Claim 7 (depends on 5) The method of claim 5, wherein the MAC CE includes a field indicating candidate beam related information for at least one secondary cell. ### Claim 8 (depends on 5) The method of claim 5, wherein the omitted information related to the candidate beam comprises a candidate availability indication and a candidate reference signal index for the special cell. ### Claim 9 A non-transitory computer readable medium comprising program instructions for causing a first device to: in accordance with a determination that a beam failure occurs in a special cell, initiate a contention-based random access procedure for beam failure recovery of the special cell; indicate by the first device a candidate beam for beam failure recovery of the special cell to a second device via a preamble during the contention-based random access procedure; include an indication for indicating the beam failure for the special cell into a media access control (MAC) control element (CE); and transmit the MAC CE to the second device via a Msg. 3 during the contention-based random access procedure; wherein the special cell comprises a primary cell or a primary secondary cell, and wherein the MAC CE omits information related to the candidate beam for beam failure recovery of the special cell. ### Claim 10 (depends on 9) The non-transitory computer readable medium of claim 9, where the MAC CE includes a bitmap indicating beam failure detection for the special cell and at least one secondary cell. ### Claim 11 (depends on 1) The non-transitory computer readable medium of claim 1, wherein the MAC CE includes a field indicating candidate beam related information for at least one secondary cell. ### Claim 12 (depends on 9) The non-transitory computer readable medium of claim 9, wherein the omitted information related to the candidate beam comprises a candidate availability indication and a candidate reference signal index for the special cell.