Physical layer non-line-of-sight (LOS) path discrimination using multiple frequency carriers

1. A method at a wireless device of determining a line-of-sight (LOS) path between a transmitter and the wireless device, comprising:

sending, to the transmitter, an indication that the wireless device is capable of measuring a time of arrival of a reference signal on multiple frequency bands within a given accuracy;

receiving, from the transmitter, a first reference signal on a first frequency band of the multiple frequency bands at a first time of arrival;

receiving, from the transmitter, a second reference signal on a second frequency band of the multiple frequency bands at a second time of arrival, wherein the second frequency band is different from the first frequency band; and

determining, at least based on a comparison of the first time of arrival to the second time of arrival, whether the first reference signal, the second reference signal, or both followed the LOS path between the transmitter and the wireless device.

2. The method of claim 1 , further comprising:

tuning, by a first radio of the wireless device, to the first frequency band to receive the first reference signal; and

tuning, by a second radio of the wireless device, to the second frequency band to receive the second reference signal.

3. The method of claim 2 , wherein the first radio and the second radio are synchronized in time with each other.

4. The method of claim 3 , wherein the first radio and the second radio are synchronized in time with the transmitter.

5. The method of claim 1 , further comprising:

tuning, by a radio of the wireless device, to the first frequency band to receive the first reference signal; and

tuning, by the radio of the wireless device, to the second frequency band to receive the second reference signal.

6. The method of claim 1 , wherein the first frequency band comprises a high frequency band and the second frequency band comprises a low frequency band.

7. The method of claim 6 , wherein the first time of arrival is after the second time of arrival.

8. The method of claim 7 , further comprising:

determining, based on the first time of arrival being after the second time of arrival, that the first reference signal did not follow the LOS path.

9. The method of claim 7 , further comprising:

determining, based on the first time of arrival being after the second time of arrival and a signal strength of the second reference signal being above a threshold, that the second reference signal followed the LOS path.

10. The method of claim 7 , further comprising:

determining, based on the first time of arrival being after the second time of arrival and a signal strength of the second reference signal being below a threshold, that both the first reference signal and the second reference signal did not follow the LOS path.

11. The method of claim 6 , wherein the first time of arrival is the same as the second time of arrival.

12. The method of claim 11 , further comprising:

determining, based on the first time of arrival being the same as the second time of arrival, that both the first reference signal and the second reference signal followed the LOS path.

13. The method of claim 11 , further comprising:

determining, based on the first time of arrival being the same as the second time of arrival and a signal strength of the second reference signal being higher than a signal strength of the first reference signal, that both the first reference signal and the second reference signal followed the LOS path through an obstacle.

14. The method of claim 11 , further comprising:

determining, based on the first time of arrival being the same as the second time of arrival and a signal strength of the second reference signal being below a threshold, that both the first reference signal and the second reference signal did not follow the LOS path.

15. The method of claim 1 , further comprising:

reporting, to the transmitter, which of the first reference signal and/or the second reference signal followed the LOS path.

16. The method of claim 15 , wherein a time of arrival of whichever of the first reference signal and/or the second reference signal followed the LOS path is used by a positioning entity in a round-trip-time positioning procedure.

17. The method of claim 1 , further comprising:

estimating a location of the wireless device based on a time of arrival of whichever of the first reference signal and/or the second reference signal followed the LOS path.

18. The method of claim 1 , further comprising:

reporting, to the transmitter, the first time of arrival, the second time of arrival, a signal strength of the first reference signal, and a signal strength of the second reference signal.

19. The method of claim 1 , further comprising:

reporting, to the transmitter, a difference between the first time of arrival and the second time of arrival, a signal strength of the first reference signal, and a signal strength of the second reference signal.

20. The method of claim 1 , wherein:

the wireless device comprises a user equipment and the transmitter comprises a base station or transmission-reception point (TRP), or

the wireless device comprises a first base station or TRP and the transmitter comprises a second base station or TRP, or

the wireless device comprises a base station or TRP and the transmitter comprises a user equipment, or

the wireless device comprises a user equipment and the transmitter comprises a user equipment.

21. The method of claim 1 , wherein the first and second reference signals are transmitted at the same time or with a known offset to be used to adjust the first time of arrival, the second time of arrival, or both.

22. The method of claim 21 , further comprising:

receiving an indication of the known offset from the transmitter.

23. A wireless device, comprising:

a memory;

at least one transceiver; and

at least one processor communicatively coupled to the memory and the at least one transceiver, wherein the at least one processor is configured to:

send, to a transmitter via the at least one transceiver, an indication that the wireless device is capable of measuring a time of arrival of a reference signal on multiple frequency bands within a given accuracy;

receive, from the transmitter via the at least one transceiver, a first reference signal on a first frequency band of the multiple frequency bands at a first time of arrival;

receive, from the transmitter via the at least one transceiver, a second reference signal on a second frequency band of the multiple frequency bands at a second time of arrival, wherein the second frequency band is different from the first frequency band; and

determine, at least based on a comparison of the first time of arrival to the second time of arrival, whether the first reference signal, the second reference signal, or both followed a line of site (LOS) path between the transmitter and the wireless device.

24. The wireless device of claim 23 , further comprising:

a first radio of the at least one transceiver configured to tune to the first frequency band to receive the first reference signal; and

a second radio of the at least one transceiver configured to tune to the second frequency band to receive the second reference signal.

25. The wireless device of claim 24 , wherein the first radio and the second radio are synchronized in time with each other.

26. The wireless device of claim 25 , wherein the first radio and the second radio are synchronized in time with the transmitter.

27. The wireless device of claim 23 , further comprising:

a radio of the at least one transceiver configured to tune to the first frequency band to receive the first reference signal, and configured to tune to the second frequency band to receive the second reference signal.

28. The wireless device of claim 23 , wherein the first frequency band comprises a high frequency band and the second frequency band comprises a low frequency band.

29. The wireless device of claim 28 , wherein the first time of arrival is after the second time of arrival.

30. The wireless device of claim 29 , wherein, based on the first time of arrival being after the second time of arrival, the at least one processor is configured to determine that the first reference signal did not follow the LOS path.

31. The wireless device of claim 29 , wherein, based on the first time of arrival being after the second time of arrival and a signal strength of the second reference signal being above a threshold, the at least one processor is configured to determine that the second reference signal followed the LOS path.

32. The wireless device of claim 29 , wherein, based on the first time of arrival being after the second time of arrival and a signal strength of the second reference signal being below a threshold, the at least one processor is configured to determine that both the first reference signal and the second reference signal did not follow the LOS path.

33. The wireless device of claim 28 , wherein the first time of arrival is the same as the second time of arrival.

34. The wireless device of claim 33 , wherein, based on the first time of arrival being the same as the second time of arrival, the at least one processor is configured to determine that both the first reference signal and the second reference signal followed the LOS path.

35. The wireless device of claim 33 , wherein, based on the first time of arrival being the same as the second time of arrival and a signal strength of the second reference signal being higher than a signal strength of the first reference signal, the at least one processor is configured to determine that both the first reference signal and the second reference signal followed the LOS path through an obstacle.

36. The wireless device of claim 33 , wherein, based on the first time of arrival being the same as the second time of arrival and a signal strength of the second reference signal being below a threshold, the at least one processor is configured to determine that both the first reference signal and the second reference signal did not follow the LOS path.

37. The wireless device of claim 23 , wherein the at least one processor is further configured to:

cause the at least one transceiver to report, to the transmitter, which of the first reference signal and/or the second reference signal followed the LOS path.

38. The wireless device of claim 37 , wherein a time of arrival of whichever of the first reference signal and/or the second reference signal followed the LOS path is used by a positioning entity in a round-trip-time positioning procedure.

39. The wireless device of claim 23 , wherein the at least one processor is further configured to:

estimate a location of the wireless device based on a time of arrival of whichever of the first reference signal and/or the second reference signal followed the LOS path.

40. The wireless device of claim 23 , wherein the at least one processor is further configured to:

cause the at least one transceiver to report, to the transmitter, the first time of arrival, the second time of arrival, a signal strength of the first reference signal, and a signal strength of the second reference signal.

41. The wireless device of claim 23 , wherein the at least one processor is further configured to:

cause the at least one transceiver to report, to the transmitter, a difference between the first time of arrival and the second time of arrival, a signal strength of the first reference signal, and a signal strength of the second reference signal.

42. The wireless device of claim 23 , wherein:

the wireless device comprises a user equipment and the transmitter comprises a base station or transmission-reception point (TRP), or

the wireless device comprises a first base station or TRP and the transmitter comprises a second base station or TRP, or

the wireless device comprises a base station or TRP and the transmitter comprises a user equipment, or

the wireless device comprises a user equipment and the transmitter comprises a user equipment.

43. The wireless device of claim 23 , wherein the first and second reference signals are transmitted at the same time or with a known offset to be used to adjust the first time of arrival, the second time of arrival, or both.

44. The wireless device of claim 23 , wherein the at least one processor is further configured to:

receive, via the at least one transceiver, an indication of the known offset from the transmitter.

45. A wireless device, comprising:

means for sending, to a transmitter, an indication that the wireless device is capable of measuring a time of arrival of a reference signal on multiple frequency bands within a given accuracy;

means for receiving, from the transmitter, a first reference signal on a first frequency band of the multiple frequency bands at a first time of arrival;

means for receiving, from the transmitter, a second reference signal on a second frequency band of the multiple frequency bands at a second time of arrival, wherein the second frequency band is different from the first frequency band; and

means for determining, at least based on a comparison of the first time of arrival to the second time of arrival, whether the first reference signal, the second reference signal, or both followed the LOS path between the transmitter and the wireless device.

46. A non-transitory computer-readable medium storing computer-executable instructions, the computer-executable instructions comprising:

at least one instruction instructing a wireless device to send, to a transmitter, an indication that the wireless device is capable of measuring a time of arrival of a reference signal on multiple frequency bands within a given accuracy;

at least one instruction instructing the wireless device to receive, from the transmitter, a first reference signal on a first frequency band of the multiple frequency bands at a first of arrival;

at least one instruction instructing the wireless device to receive, from the transmitter, a second reference signal on a second frequency band of the multiple frequency bands at a second time of arrival, wherein the second frequency band is different from the first frequency band; and

at least one instruction instructing the wireless device to determine, at least based on a comparison of the first time of arrival to the second time of arrival, whether the first reference signal, the second reference signal, or both followed the LOS path between the transmitter and the wireless device.