# US 11,310,021 B2 · Uplink doppler metric estimation based on a downlink reference signal > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,310,021 B2 - Document ID: US11310021B2 - Status: Granted - Kind: B2 - Application number: 16/876,575 - Filed: 2020-05-18 - Published: 2021-11-18 - Granted: 2022-04-19 - Earliest claimed: 2020-05-18 - Assignees: QUALCOMM Incorporated - Applicants: QUALCOMM Incorporated - Inventors: Michael Levitsky; Assaf Touboul; Ran Berliner; Shay Landis; Lior Uziel - Web page: https://patentgrep.com/patent/US11310021B2 ## CPC - H04L 5/10: with dynamo-electric generation of carriers; with mechanical filters or demodulators - H04B 7/01: Reducing phase shift - H04B 17/336: Signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR] - H04L 5/0051: {of dedicated pilots, i.e. pilots destined for a single user or terminal} - H04L 5/0094: {Indication of how sub-channels of the path are allocated} - H04L 25/0222: {Estimation of channel variability, e.g. coherence bandwidth, coherence time, fading frequency} - H04L 25/0226: {sounding signals per se} - H04L 27/2613: {Structure of the reference signals} - H04B 7/0456: Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04B: TRANSMISSION ## Abstract Methods, systems, and devices for wireless communications are described. A base station may transmit repetitions of a tracking reference signal to a user equipment (UE). The UE may determine a Doppler frequency for the downlink channel by measuring the repetitions of the tracking reference signal. The UE may transmit an indication of the downlink Doppler frequency to the base station. The base station may determine the uplink Doppler frequency based on the downlink Doppler frequency. The base station may use the uplink Doppler frequency to select an uplink demodulation reference signal (DMRS) configuration for the UE. ## Claims ### Claim 1 A method for wireless communication at a user equipment (UE), comprising: measuring a first repetition and a second repetition of a tracking reference signal received over a downlink channel between the UE and a base station; determining a correlation in time between the first and second repetitions of the tracking reference signal based at least in part on measuring the first and second repetitions of the tracking reference signal; determining a Doppler metric for the downlink channel based at least in part on measuring the tracking reference signal and on the correlation in time between the first and second repetitions of the tracking reference signal; transmitting an indication of the Doppler metric for the downlink channel to the base station; and receiving, based at least in part on transmitting the indication of the Doppler metric for the downlink channel, an indication of a configuration for an uplink demodulation reference signal. ### Claim 2 (depends on 1) The method of claim 1, wherein the first and second repetitions of the tracking reference signal are received in the same subframe. ### Claim 3 (depends on 1) The method of claim 1, wherein the first and second repetitions of the tracking reference signal are received in consecutive subframes. ### Claim 4 (depends on 1) The method of claim 1, further comprising: determining a delay spread for the downlink channel based at least in part on measuring the first and second repetitions of the tracking reference signal; and transmitting an indication of the delay spread for the downlink channel, wherein the configuration for the uplink demodulation reference signal is based at least in part on the indication of the delay spread. ### Claim 5 (depends on 1) The method of claim 1, further comprising: transmitting the uplink demodulation reference signal according to the configuration for the uplink demodulation reference signal. ### Claim 6 (depends on 1) The method of claim 1, further comprising: receiving signaling that indicates the UE is to transmit the indication of the Doppler metric periodically, aperiodically, or semi-persistently, wherein the indication of the Doppler metric is transmitted based at least in part on the signaling. ### Claim 7 (depends on 1) The method of claim 1, wherein the Doppler metric comprises Doppler shift. ### Claim 8 A method for wireless communication at a base station, comprising: transmitting, to a user equipment (UE), a first repetition of a tracking reference signal in a first symbol of a subframe and a second repetition of the tracking reference signal in a second symbol of the subframe; receiving, from the UE, an indication of a Doppler metric for a downlink channel between the base station and the UE, the Doppler metric based at least in part on the first and second repetitions of the tracking reference signal; selecting a configuration for an uplink demodulation reference signal based at least in part on the Doppler metric for the downlink channel; and transmitting an indication of the configuration for the uplink demodulation reference signal to the UE. ### Claim 9 (depends on 8) The method of claim 8, further comprising: receiving an indication of a delay spread for the downlink channel, wherein the configuration for the uplink demodulation reference signal is based at least in part on the indication of the delay spread. ### Claim 10 (depends on 8) The method of claim 8, further comprising: receiving the uplink demodulation reference signal according to the configuration for the uplink demodulation reference signal. ### Claim 11 (depends on 8) The method of claim 8, further comprising: transmitting, to the UE, signaling that indicates the Doppler metric is to be transmitted periodically, aperiodically, or semi-persistently, wherein the indication of the Doppler metric is received based at least in part on the signaling. ### Claim 12 (depends on 8) The method of claim 8, further comprising: determining a reciprocity between the Doppler metric for the downlink channel and a corresponding Doppler metric for an uplink channel between the UE and the base station, wherein the configuration for the uplink demodulation reference signal is based at least in part on the reciprocity. ### Claim 13 (depends on 12) The method of claim 12, further comprising: determining that one or more conditions for reciprocity are satisfied, wherein the reciprocity is determined based on determining that the one or more conditions for reciprocity are satisfied. ### Claim 14 (depends on 8) The method of claim 8, further comprising: receiving a sounding reference signal from the UE; and measuring the sounding reference signal. ### Claim 15 (depends on 14) The method of claim 14, further comprising: determining a delay spread for an uplink channel between the UE and the base station based at least in part on measuring the sounding reference signal, wherein the configuration for the uplink demodulation reference signal is based at least in part on the delay spread. ### Claim 16 (depends on 14) The method of claim 14, further comprising: determining a signal-to-noise-ratio (SNR) for an uplink channel between the UE and the base station based at least in part on measuring the sounding reference signal, wherein the configuration for the uplink demodulation reference signal is based at least in part on the SNR. ### Claim 17 (depends on 8) The method of claim 8, wherein the Doppler metric comprises Doppler shift. ### Claim 18 An apparatus for wireless communication at a user equipment (UE), comprising: a processor, memory coupled with the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to: measure a first repetition and a second repetition of a tracking reference signal received over a downlink channel between the UE and a base station; determine a correlation in time between the first and second repetitions of the tracking reference signal based at least in part on measuring the first and second repetitions of the tracking reference signal; determine a Doppler metric for the downlink channel based at least in part on measuring the tracking reference signal and on the correlation in time between the first and second repetitions of the tracking reference signal; transmit an indication of the Doppler metric for the downlink channel to the base station; and receive, based at least in part on transmitting the indication of the Doppler metric for the downlink channel, an indication of a configuration for an uplink demodulation reference signal. ### Claim 19 (depends on 18) The apparatus of claim 18, wherein the first and second repetitions of the tracking reference signal are received in the same subframe. ### Claim 20 (depends on 18) The apparatus of claim 18, wherein the first and second repetitions of the tracking reference signal are received in the same subframe. ### Claim 21 (depends on 18) The apparatus of claim 18, wherein the instructions are further executable by the processor to cause the apparatus to: determine a delay spread for the downlink channel based at least in part on measuring the first and second repetitions of the tracking reference signal; and transmit an indication of the delay spread for the downlink channel, wherein the configuration for the uplink demodulation reference signal is based at least in part on the indication of the delay spread. ### Claim 22 (depends on 18) The apparatus of claim 18, wherein the instructions are further executable by the processor to cause the apparatus to: transmit the uplink demodulation reference signal according to the configuration for the uplink demodulation reference signal. ### Claim 23 (depends on 18) The apparatus of claim 18, wherein the instructions are further executable by the processor to cause the apparatus to: receive signaling that indicates the UE is to transmit the indication of the Doppler metric periodically, aperiodically, or semi-persistently, wherein the indication of the Doppler metric is transmitted based at least in part on the signaling. ### Claim 24 (depends on 18) The apparatus of claim 18, wherein the Doppler metric comprises Doppler shift. ### Claim 25 An apparatus for wireless communication at a base station, comprising: a processor, memory coupled with the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to: transmit, to a user equipment (UE), a first repetition of a tracking reference signal in a first symbol of a subframe and a second repetition of the tracking reference signal in a second symbol of the subframe; receive, from the UE, an indication of a Doppler metric for a downlink channel between the base station and the UE, the Doppler metric based at least in part on the first and second repetitions of the tracking reference signal; select a configuration for an uplink demodulation reference signal based at least in part on the Doppler metric for the downlink channel; and transmit an indication of the configuration for the uplink demodulation reference signal to the UE. ### Claim 26 (depends on 25) The apparatus of claim 25, wherein the instructions are further executable by the processor to cause the apparatus to: receive an indication of a delay spread for the downlink channel, wherein the configuration for the uplink demodulation reference signal is based at least in part on the indication of the delay spread. ### Claim 27 (depends on 25) The apparatus of claim 25, wherein the instructions are further executable by the processor to cause the apparatus to: receiving the uplink demodulation reference signal according to the configuration for the uplink demodulation reference signal. ### Claim 28 (depends on 25) The apparatus of claim 25, wherein the instructions are further executable by the processor to cause the apparatus to: transmit, to the UE, signaling that indicates the Doppler metric is to be transmitted periodically, aperiodically, or semi-persistently, wherein the indication of the Doppler metric is received based at least in part on the signaling. ### Claim 29 (depends on 25) The apparatus of claim 25, wherein the instructions are further executable by the processor to cause the apparatus to: determine a reciprocity between the Doppler metric for the downlink channel and a corresponding Doppler metric for an uplink channel between the UE and the base station, wherein the configuration for the uplink demodulation reference signal is based at least in part on the reciprocity. ### Claim 30 (depends on 25) The apparatus of claim 25, wherein the Doppler metric comprises Doppler shift.