# US 2022/0286340 A1 · Fast feedback techniques for high frequency bands in wireless communications systems > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2022/0286340 A1 - Document ID: US20220286340A1 - Status: Published application - Kind: A1 - Application number: 17/191,585 - Filed: 2021-03-03 - Published: 2022-09-08 - Earliest claimed: 2021-03-03 - Assignees: QUALCOMM Incorporated - Applicants: QUALCOMM Incorporated - Inventors: Yehonatan Dallal; Ran Berliner; Shay Landis - Web page: https://patentgrep.com/patent/US20220286340A1 ## CPC - H04L 27/26025: {Numerology, i.e. varying one or more of symbol duration, subcarrier spacing, Fourier transform size, sampling rate or down-clocking (allocating sub-channels of the transmission path H04L5/003)} - H04L 27/2646: {using feedback from receiver for adjusting OFDM transmission parameters, e.g. transmission timing or guard interval length} - H04L 27/2607: {Cyclic extensions} - H04L 27/2634: {Inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators in combination with other circuits for modulation} - H04W 76/19: Connection re-establishment - 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 Methods, systems, and devices for wireless communications are described. Generally, the described techniques provide for a base station to transmit a feedback configuration to a user equipment (UE) indicating a subcarrier spacing and a length of a cyclic prefix (CP) that the UE is to use to transmit feedback associated with a second frequency band (e.g., a high frequency band) using a first frequency band (e.g., a low frequency band). The UE may monitor the second frequency band for downlink messages transmitted by the base station and transmit a feedback message accordingly using the indicated subcarrier spacing and applying a CP having the indicated length. ## Claims ### Claim 1 A method for wireless communications at a user equipment (UE), comprising: receiving, from the base station, a feedback configuration for transmitting a feedback message associated with a second frequency band using a first frequency band, the feedback configuration indicating a subcarrier spacing for the first frequency band and a length of a cyclic prefix for the feedback message, wherein the second frequency band is in a higher frequency band than the first frequency band; monitoring the second frequency band for a downlink message from the base station; and transmitting, to the base station, the feedback message for the downlink message over the first frequency band using the subcarrier spacing based at least in part on the feedback configuration and on the monitoring the second frequency band, the feedback message comprising a cyclic prefix having the indicated length. ### Claim 2 (depends on 1) The method of claim 1, wherein transmitting the feedback message comprises: applying, to the feedback message, the cyclic prefix having the indicated length corresponding to a long cyclic prefix, wherein the feedback message comprises a number of resource elements that is less than a number of resource elements configured for data transmissions on the second frequency band. ### Claim 3 (depends on 1) The method of claim 1, further comprising: transmitting, to the base station, an indication of a capability of the UE to transmit feedback messages associated with the second frequency band on the first frequency band. ### Claim 4 (depends on 1) The method of claim 1, further comprising: generating the feedback message using a fast Fourier transform and a cyclic prefix comprising a length that is longer than a buffer length of a buffer associated with an inverse fast Fourier transform. ### Claim 5 (depends on 4) The method of claim 4, wherein the length of the of the cyclic prefix comprises an integer multiple of the buffer length associated with the inverse fast Fourier transform. ### Claim 6 (depends on 1) The method of claim 1, further comprising: generating the feedback message using a fast Fourier transform having a time gap greater than a buffer length of a buffer associated with an inverse fast Fourier transform. ### Claim 7 (depends on 1) The method of claim 1, wherein the length of the cyclic prefix comprises a length that is longer than a default length of a cyclic prefix associated with the first frequency band. ### Claim 8 (depends on 1) The method of claim 1, wherein the subcarrier spacing for the first frequency band is equal to a subcarrier spacing associated with the second frequency band. ### Claim 9 (depends on 1) The method of claim 1, wherein the subcarrier spacing for the first frequency band comprises an integer multiple of a subcarrier spacing associated with the second frequency band. ### Claim 10 (depends on 1) The method of claim 1, wherein transmitting the feedback message comprises: transmitting the feedback message using a subset of available subcarriers associated with the first frequency band. ### Claim 11 (depends on 1) The method of claim 1, wherein: the subcarrier spacing for the first frequency band comprises a subcarrier spacing that is greater than 60 kilohertz; and the first frequency band comprises a sub-6 gigahertz band associated with a fifth generation radio access technology. ### Claim 12 A method for wireless communications at a base station, comprising: transmitting, to the UE, a feedback configuration for transmitting a feedback message associated with a second frequency band using a first frequency band, the feedback configuration indicating a subcarrier spacing for the first frequency band and a length of a cyclic prefix for the feedback message, wherein the second frequency band is in a higher frequency band than the first frequency band; transmitting a downlink message to the UE on the second frequency band; and receiving, from the UE, the feedback message for the downlink message over the first frequency band using the subcarrier spacing based at least in part on the feedback configuration and transmitting the downlink message on the second frequency band, the feedback message comprising a cyclic prefix having the indicated length. ### Claim 13 (depends on 12) The method of claim 12, further comprising: determining the subcarrier spacing for the first frequency band based at least in part on conditions associated with a channel between the base station and the UE. ### Claim 14 (depends on 12) The method of claim 12, further comprising: receiving, from the UE, an indication of a capability of the UE to transmit feedback messages associated with the second frequency band on the first frequency band. ### Claim 15 (depends on 12) The method of claim 12, wherein the subcarrier spacing for the first frequency band is equal to a subcarrier spacing associated with the second frequency band. ### Claim 16 (depends on 12) The method of claim 12, wherein the subcarrier spacing for the first frequency band is an integer multiple of a subcarrier spacing associated with the second frequency band. ### Claim 17 (depends on 12) The method of claim 12, further comprising: transmitting, to the UE, control signaling over the first frequency band using the subcarrier spacing based at least in part on the feedback configuration. ### Claim 18 (depends on 17) The method of claim 17, further comprising: detecting a failure condition associated with the second frequency band at the UE, wherein transmitting the control signaling comprises transmitting control signaling indicating the UE to perform a recovery procedure based at least in part on the failure condition. ### Claim 19 (depends on 12) The method of claim 12, wherein receiving the feedback message comprises: receiving the feedback message using a subset of available subcarriers associated with the first frequency band. ### Claim 20 (depends on 12) The method of claim 12, wherein the length of the cyclic prefix is greater than a length of a cyclic prefix associated with the second frequency band. ### Claim 21 (depends on 12) The method of claim 12, wherein: the subcarrier spacing for the first frequency band comprises a subcarrier spacing that is greater than 60 kilohertz; and the first frequency band comprises a sub-6 gigahertz band associated with a fifth generation radio access technology. ### Claim 22 An apparatus for wireless communications at a user equipment (UE), comprising: a processor; memory in electronic communication with the processor; and instructions stored in the memory, wherein the instructions are executable by the processor to: receive, from the base station, a feedback configuration for transmitting a feedback message associated with a second frequency band using a first frequency band, the feedback configuration indicating a subcarrier spacing for the first frequency band and a length of a cyclic prefix for the feedback message, wherein the second frequency band is in a higher frequency band than the first frequency band; monitor the second frequency band for a downlink message from the base station; and transmit, to the base station, the feedback message for the downlink message over the first frequency band using the subcarrier spacing based at least in part on the feedback configuration and on the monitoring the second frequency band, the feedback message comprising a cyclic prefix having the indicated length. ### Claim 23 (depends on 22) The apparatus of claim 22, wherein the instructions executable by the processor to transmit the feedback message comprise instructions executable by the processor to: apply, to the feedback message, the cyclic prefix having the indicated length corresponding to a long cyclic prefix, wherein the feedback message comprises a number of resource elements that is less than a number of resource elements configured for data transmissions on the second frequency band. ### Claim 24 (depends on 22) The apparatus of claim 22, wherein the instructions are further executable by the processor to: transmit, to the base station, an indication of a capability of the UE to transmit feedback messages associated with the second frequency band on the first frequency band. ### Claim 25 (depends on 22) The apparatus of claim 22, wherein the instructions are further executable by the processor to: generate the feedback message using a fast Fourier transform and a cyclic prefix comprising a length that is longer than a buffer length of a buffer associated with an inverse fast Fourier transform. ### Claim 26 (depends on 22) The apparatus of claim 22, wherein the instructions are further executable by the processor to: generate the feedback message using a fast Fourier transform having a time gap greater than a buffer length of a buffer associated with an inverse fast Fourier transform. ### Claim 27 (depends on 22) The apparatus of claim 22, wherein the length of the cyclic prefix comprises a length that is longer than a default length of a cyclic prefix associated with the first frequency band. ### Claim 28 (depends on 22) The apparatus of claim 22, wherein the subcarrier spacing for the first frequency band is equal to a subcarrier spacing associated with the second frequency band. ### Claim 29 (depends on 22) The apparatus of claim 22, wherein the subcarrier spacing for the first frequency band comprises an integer multiple of a subcarrier spacing associated with the second frequency band. ### Claim 30 An apparatus for wireless communications at a base station, comprising: a processor; memory in electronic communication with the processor; and instructions stored in the memory, wherein the instructions are executable by the processor to: transmit, to the UE, a feedback configuration for transmitting a feedback message associated with a second frequency band using a first frequency band, the feedback configuration indicating a subcarrier spacing for the first frequency band and a length of a cyclic prefix for the feedback message, wherein the second frequency band is in a higher frequency band than the first frequency band; transmit a downlink message to the UE on the second frequency band; and receive, from the UE, the feedback message for the downlink message over the first frequency band using the subcarrier spacing based at least in part on the feedback configuration and transmitting the downlink message on the second frequency band, the feedback message comprising a cyclic prefix having the indicated length.