Using doppler for multipath detection and mitigation in RF-based positioning
Aspects presented herein may improve the performance and accuracy of RF-based positioning. Aspects presented herein may enable a device to use RF Doppler measurements to detect and mitigate multipath effects in RF-based positioning. The RF-based positioning may include satellite navigation, terrestrial positioning system, and/or indoor positioning. In one aspect, a UE receives, via a receiver, signals from one or more entities. The UE determines whether each received signal is a multipath signal based on a Doppler shift measurement. The UE de-weights or excludes one or more signals of the received signals in estimating a position of the UE based on whether the respective received signal is determined to be a multipath signal.
1. An apparatus of positioning at a user equipment (UE), comprising:
at least one memory;
a receiver; and
at least one processor coupled to the at least one memory and the receiver, the at least one processor is configured to:
receive, via the receiver, signals from one or more entities;
determine whether each received signal is a multipath signal based on a Doppler shift measurement; and
de-weight by W a measurement of each signal in one or more signals of the received signals in estimating a position of the UE when the respective received signal is determined to be the multipath signal, where 0≤W<1.
2. The apparatus of claim 1 , wherein, to determine whether each received signal is the multipath signal based on the Doppler shift measurement, the at least one processor is further configured to:
measure a Doppler shift of the received signal; and
determine whether residual of the measured Doppler shift for the received signal exceeds a threshold Doppler shift,
wherein the received signal is determined to be the multipath signal when the residual of the measured Doppler shift for the received signal exceeds the threshold Doppler shift.
3. The apparatus of claim 2 , wherein the threshold Doppler shift is equal to an expected Doppler shift plus or minus a Doppler shift range.
4. The apparatus of claim 3 , wherein the Doppler shift range is one of:
a constant value,
a function of the measured Doppler shift,
a function of the residual of the measured Doppler shift,
a function of a velocity of the UE, or
a function of an environment of the UE.
5. The apparatus of claim 1 , wherein W is based on a difference between the measured Doppler shift and a threshold Doppler shift.
6. The apparatus of claim 1 , wherein a first number N is equal to a number of the one or more entities, a second number M is equal to a number of transmitters of the one or more entities from which signals are received that are determined to be multipath, and W is based on a comparison of the first number N and the second number M.
7. The apparatus of claim 1 , further comprising a transmitter, wherein the at least one processor is further configured to transmit, via the transmitter, to at least one location server, measurement information or a UE position estimate associated with the de-weighted one or more signals.
8. The apparatus of claim 7 , wherein the at least one processor is further configured to transmit, to the at least one location server, information indicating whether the measurement information or the UE position estimate is associated with one or more multipath signals.
9. The apparatus of claim 1 , wherein the multipath signal includes a non-line-of-sight (NLOS) signal.
10. The apparatus of claim 1 , wherein the one or more entities include one or more satellites, one or more base stations, or a combination thereof.
11. A method of positioning at a user equipment (UE), comprising:
receiving, via the receiver, signals from one or more entities;
determining whether each received signal is a multipath signal based on a Doppler shift measurement; and
de-weighting by W a measurement of each signal in one or more signals of the received signals in estimating a position of the UE when the respective received signal is determined to be the multipath signal, where 0≤W<1.
12. The method of claim 11 , wherein the determining whether each received signal is the multipath signal based on the Doppler shift measurement comprises:
measuring a Doppler shift of the received signal; and
determining whether residual of the measured Doppler shift for the received signal exceeds a threshold Doppler shift,
wherein the received signal is determined to be the multipath signal when the residual of the measured Doppler shift for the received signal exceeds the threshold Doppler shift.
13. The method of claim 12 , wherein the threshold Doppler shift is equal to an expected Doppler shift plus or minus a Doppler shift range.
14. The method of claim 13 , wherein the Doppler shift range is one of:
a constant value,
a function of the measured Doppler shift,
a function of the residual of the measured Doppler shift,
a function of a velocity of the UE, or
a function of an environment of the UE.
15. The method of claim 11 , wherein W is based on a difference between the measured Doppler shift and a threshold Doppler shift.
16. The method of claim 11 , wherein a first number N is equal to a number of the one or more entities, a second number M is equal to a number of transmitters of the one or more entities from which signals are received that are determined to be multipath, and W is based on a comparison of the first number N and the second number M.
17. The method of claim 11 , further comprising:
transmitting, via a transmitter, to at least one location server, measurement information or a UE position estimate associated with the de-weighted one or more signals; and
transmitting, to the at least one location server, information indicating whether the measurement information or the UE position estimate is associated with one or more multipath signals.
18. An apparatus for wireless communication at a user equipment (UE), comprising:
means for receiving, via the receiver, signals from one or more entities;
means for determining whether each received signal is a multipath signal based on a Doppler shift measurement and
means for de-weighting by W a measurement of each signal in one or more signals of the received signals in estimating a position of the UE when the respective received signal is determined to be the multipath signal, where 0≤W<1.
19. A non-transitory computer-readable medium storing computer executable code at a <user equipment (UE), the code when executed by at least one processor causes the at least one processor to:
receive, via the receiver, signals from one or more entities;
determine whether each received signal is a multipath signal based on a Doppler shift measurement; and
de-weight by W a measurement of each signal in one or more signals of the received signals in estimating a position of the UE when the respective received signal is determined to be the multipath signal, where 0≤W<1.