Radio frequency sensing with channel impulse response
Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a responding device may receive a signal from an initiating device. The responding device may estimate, from the signal, a channel impulse response (CIR) that represents signal reflections from one or more objects as multiple taps. The responding device may select one or more taps, from the multiple taps, that are within a first time window that starts at a first offset from a reference point and that has a first specified time duration. The responding device may transmit, to the initiating device, a CIR report that indicates the one or more taps. Numerous other aspects are described.
1 . A responding device for wireless communication, comprising:
one or more memories; and
one or more processors, coupled to the one or more memories, configured to:
receive a signal from an initiating device;
estimate, from the signal, a channel impulse response (CIR) that represents signal reflections from one or more objects as multiple taps;
select one or more taps, from the multiple taps, that are within a first time window that starts at a first offset from a reference point and that has a first specified time duration; and
transmit, to the initiating device, a CIR report that indicates the one or more taps, wherein the CIR report includes the first specified time duration and the first offset.
2 . The responding device of claim 1 , wherein the first offset is based at least in part on a transmission time and a reference time associated with a sensing range of interest.
3 . The responding device of claim 1 , wherein the one or more processors are configured to negotiate the reference point with one or more sensing devices.
4 . The responding device of claim 1 , wherein the reference point includes an earliest tap, a strongest tap, a packet detection time, or a center of mass for the multiple taps.
5 . The responding device of claim 1 , wherein the one or more processors, to select the one or more taps, are configured to select the one or more taps from within the first time window and a second time window having a second specified time duration and a second offset.
6 . The responding device of claim 5 , wherein the one or more processors are configured to negotiate, with a sensing device, one or more of the first specified time duration, a starting point of the first time window, the second specified time duration, a starting point of the second time window, or a quantity of time windows.
7 . The responding device of claim 5 , wherein the one or more processors are configured to receive, from one or more sensing devices, one or more of a supported window time duration or a supported quantity of windows.
8 . The responding device of claim 5 , wherein the one or more processors are configured to:
negotiate, among sensing devices, one or more of the first specified time duration, the reference point, or the first offset; and
select one or more of the first specified time duration, the reference point, or the first offset based at least in part on a range of interest.
9 . The responding device of claim 5 , wherein the multiple taps are at non-interpolated sampling time occasions, and wherein selecting the one or more taps from the multiple taps includes generating, by interpolation, one or more interpolated taps between consecutive taps of the multiple taps.
10 . The responding device of claim 9 , wherein a first interpolated tap of the one or more interpolated taps is separated in time from a non-interpolated sampling occasion by an interpolation offset, and wherein the interpolation offset is included in the CIR report.
11 . The responding device of claim 1 , wherein a sampling rate for the one or more taps is based at least in part on a UWB chip rate or a multiple of the UWB chip rate.
12 . The responding device of claim 1 , wherein the one or more processors are configured to negotiate, with a sensing device or the initiating device, a quantity of bits for representing quantized values of the one or more taps in the CIR report.
13 . The responding device of claim 1 , wherein the CIR report indicates, for each tap in the CIR report, an in-phase and quadrature value, wherein for each tap in the CIR report, the in-phase and quadrature value may be normalized with a normalization factor, and wherein the normalization factor is included in the CIR report.
14 . The responding device of claim 1 , wherein the one or more processors, to receive the signal, are configured to receive the signal at multiple receive antennas, wherein transmitting the CIR report includes transmitting a CIR report for each antenna of the multiple receive antennas, and wherein the reference point is a common reference point among the multiple receive antennas.
15 . The responding device of claim 14 , wherein the common reference point is based at least in part on an earliest arrival path of an antenna among the multiple receive antennas with a strongest energy signal.
16 . The responding device of claim 14 , wherein the common reference point is based at least in part on a median or an average of estimated time for earliest arrival paths for the multiple receive antennas.
17 . The responding device of claim 14 , wherein the common reference point is based at least in part on adding powers or amplitudes of multiple antenna CIRs and an estimation of an earliest arrival path for the multiple receive antennas based at least in part on interpolation from a combined CIR.
18 . The responding device of claim 14 , wherein the one or more processors are configured to transmit an indication of a time offset for a CIR of each antenna relative to the common reference point.
19 . The responding device of claim 1 , wherein the one or more processors, to transmit the CIR report, are configured to transmit the CIR report for a first antenna and an indication of an angle of arrival for each of the one or more taps.
20 . The responding device of claim 1 , wherein the one or more processors are configured to:
switch antennas during scrambled timestamp sequence (STS) gaps between STS segments, wherein each STS segment has an STS sensing part transmitted by an antenna of multiple transmit antennas; and
insert short STS sequences between the STS segments for settling of an automatic gain control (AGC) value.
21 . The responding device of claim 1 , wherein the one or more processors are configured to:
switch transmit antennas during scrambled timestamp sequence (STS) gaps between STS segments, wherein each STS segment has an STS sensing part transmitted by an antenna of multiple transmit antennas; and
set an automatic gain control (AGC) value for each STS segment based at least in part on previous AGC values.
22 . The responding device of claim 21 , wherein the one or more processors are configured to negotiate an antenna sequence to be included in preambles of the STS segments.
23 . The responding device of claim 1 , wherein the one or more processors are configured to switch antennas between scrambled timestamp sequence (STS) packets.
24 . A method of wireless communication performed by a responding device, comprising:
receiving a signal from an initiating device;
estimating, from the signal, a channel impulse response (CIR) that represents signal reflections from one or more objects as multiple taps;
selecting one or more taps, from the multiple taps, that are within a first time window that starts at a first offset from a reference point and that has a first specified time duration; and
transmitting, to the initiating device, a CIR report that indicates the one or more taps, wherein the CIR report includes the first specified time duration and the first offset.
25 . The method of claim 24 , wherein the first offset is based at least in part on a transmission time and a reference time associated with a sensing range of interest.
26 . The method of claim 24 , further comprising negotiating the reference point with one or more sensing devices.
27 . The method of claim 24 , wherein the reference point includes an earliest tap, a strongest tap, a packet detection time, or a center of mass for the multiple taps.
28 . The method of claim 24 , wherein selecting the one or more taps comprises selecting the one or more taps from within the first time window and a second time window having a second specified time duration and a second offset.
29 . The method of claim 28 , further comprising negotiating, with a sensing device, one or more of the first specified time duration, a starting point of the first time window, the second specified time duration, a starting point of the second time window, or a quantity of time windows.
30 . The method of claim 28 , further comprising receiving, from one or more sensing devices, one or more of a supported window time duration or a supported quantity of windows.