Technique for detection of line-of-sight transmissions using millimeter wave communication devices
Systems and methods for wireless communications are disclosed. More particularly, aspects of the present disclosure generally relate to techniques for wireless communications by a first apparatus comprising obtaining, via at least first and second receive antennas having different polarizations, first and second training signals transmitted from a second apparatus via at least first and second transmit antennas having different polarizations, determining, based on the first and second training signals, one or more characteristics for different transmit-receive antenna pairs, each pair comprising one of the first or second transmit antennas and one of the first or second receive antennas, and generating, based on one or more characteristics, a parameter indicative of whether a link path between the first and second apparatuses is line of sight (LOS).
1. A first apparatus for wireless communications, comprising:
a first interface for obtaining, via at least first and second receive antennas having different polarizations, first and second training signals transmitted from a second apparatus via at least first and second transmit antennas having different polarizations;
a processing system configured to:
determine, based on the first and second training signals, at least first and second characteristics for different transmit-receive antenna pairs, each pair comprising one of the first or second transmit antennas and one of the first or second receive antennas, and
generate, based on a difference or a ratio between the first and second characteristics, a parameter indicative of whether a link path between the first and second apparatuses is line of sight (LOS), wherein the first characteristic is determined based on the first training signal and the second characteristic is determined based on the second training signal; and
a second interface for outputting the parameter for transmission to the second apparatus.
2. The first apparatus of claim 1 , wherein the first and second characteristics comprise receive power of training signals transmitted and received via a given one of the transmit-receive antenna pairs.
3. The first apparatus of claim 1 , wherein the first and second characteristics comprise receive phase of training signals transmitted and received via a given one of the transmit-receive antenna pairs.
4. The first apparatus of claim 1 , wherein:
the first characteristic is determined based on the first training signal as received on the first receive antenna; and
the second characteristic is determined based on the second training signal as received on the second receive antenna.
5. The first apparatus of claim 4 , wherein the processing system is configured to indicate, via the parameter, that the link path between the first and second apparatuses is LOS if the difference or the ratio between the first and second characteristics is equal to or below a threshold value.
6. The first apparatus of claim 5 , wherein the first and second characteristics and the threshold value are adjusted based on a factor.
7. The first apparatus of claim 6 , wherein the factor is based on at least one of a cross-polarization number or polarization coefficients.
8. The first apparatus of claim 6 , wherein the factor is based on at least an indication received from the second apparatus.
9. The first apparatus of claim 4 , wherein:
the first characteristic is determined based on the first training signal as received on the second receive antenna; and
the second characteristic is determined based on the second training signal as received on the first receive antenna.
10. The first apparatus of claim 9 , wherein the processing system is configured to indicate, via the parameter, that the link path between the first and second apparatuses is LOS if the difference or the ratio between the first and second characteristics is equal to or below a threshold value.
11. The first apparatus of claim 1 , wherein the first and second training signals are received as a part of a beamforming training procedure.
12. The first apparatus of claim 1 , wherein:
the different polarizations of the first and second transmit antennas correspond to horizontal and vertical polarizations.
13. The first apparatus of claim 1 , wherein:
the different polarizations of the first and second receive antennas correspond to horizontal and vertical polarizations.
14. The first apparatus of claim 1 , wherein:
at least the first and second receive and transmit antennas comprise a dual polarized antenna.
15. The first apparatus of claim 1 , wherein at least one of the first or second antenna is circularly polarized.
16. A method for wireless communications by a first apparatus, comprising:
obtaining, via at least first and second receive antennas having different polarizations, first and second training signals transmitted from a second apparatus via at least first and second transmit antennas having different polarizations;
determining, based on the first and second training signals, at least first and second characteristics for different transmit-receive antenna pairs, each pair comprising one of the first or second transmit antennas and one of the first or second receive antennas;
generating, based on a difference or a ratio between the first and second characteristics, a parameter indicative of whether a link path between the first and second apparatuses is line of sight (LOS), wherein the first characteristic is determined based on the first training signal and the second characteristic is determined based on the second training signal; and
outputting the parameter for transmission to the second apparatus.
17. The method of claim 16 , wherein the first and second characteristics comprise receive power of training signals transmitted and received via a given one of the transmit-receive antenna pairs.
18. The method of claim 16 , wherein the first and second characteristics comprise receive phase of training signals transmitted and received via a given one of the transmit-receive antenna pairs.
19. The method of claim 16 , wherein:
the first characteristic is determined based on the first training signal as received on the first receive antenna; and
the second characteristic is determined based on the second training signal as received on the second receive antenna.
20. The method of claim 16 , wherein the first and second training signals are received as a part of a beamforming training procedure.
21. The method of claim 16 , wherein:
the different polarizations of the first and second transmit antennas correspond to horizontal and vertical polarizations.
22. The method of claim 16 , wherein:
the different polarizations of the first and second receive antennas correspond to horizontal and vertical polarizations.
23. A first apparatus for wireless communications, comprising:
means for obtaining, via at least first and second receive antennas having different polarizations, first and second training signals transmitted from a second apparatus via at least first and second transmit antennas having different polarizations;
means for determining, based on the first and second training signals, at least first and second characteristics for different transmit-receive antenna pairs, each pair comprising one of the first or second transmit antennas and one of the first or second receive antennas;
means for generating, based on a difference or a ratio between the first and second characteristics, a parameter indicative of whether a link path between the first and second apparatuses is line of sight (LOS), wherein the first characteristic is determined based on the first training signal and the second characteristic is determined based on the second training signal; and
means for outputting the parameter for transmission to the second apparatus.
24. A wireless station, comprising:
at least first and second receive antennas having different polarizations;
a receiver for receiving, via the first and second receive antennas, first and second training signals transmitted from an apparatus via at least first and second transmit antennas having different polarizations; and
a processing system configured to:
determine, based on the first and second training signals, at least first and second characteristics for different transmit-receive antenna pairs, each pair comprising one of the first or second transmit antennas and one of the first or second receive antennas,
generate, based on a difference or a ratio between the first and second characteristics, a parameter indicative of whether a link path between the wireless station and the apparatus is line of sight (LOS), wherein the first characteristic is determined based on the first training signal and the second characteristic is determined based on the second training signal; and
a transmitter configured to transmit the parameter to the apparatus.
25. The wireless station of claim 24 , wherein the first and second receive antennas comprise at least one vertically polarized receive antenna and at least one horizontally polarized receive antenna.
26. The method of claim 16 , wherein:
the first characteristic is determined based on the first training signal as received on the second receive antenna; and
the second characteristic is determined based on the second training signal as received on the first receive antenna.
27. The method of claim 16 , further comprising indicating, via the parameter, that the link path between the first and second apparatuses is LOS if the difference or the ratio between the first and second characteristics is equal to or below a threshold value.
28. The method of claim 27 , wherein the first and second characteristics and the threshold value are adjusted based on a factor.
29. The method of claim 28 , wherein the factor is based on at least one of a cross-polarization number or polarization coefficients.