Angle of arrival estimation in a radio communications network
There is provided mechanisms for estimating angle of arrival of a radio signal in a radio communications network. A method is performed by a radio transceiver device. The radio transceiver device comprises an antenna array that, by means of analog beamforming, is configured to shift between at least two phase center locations. The method comprises obtaining measurements of the radio signal as received by the antenna array using two mutually different phase center locations. The method comprises estimating the angle of arrival of the radio signal using the measurements as obtained using the two mutually different phase center locations.
1. A radio transceiver device for estimating angle of arrival of a radio signal in a radio communications network, the radio transceiver device comprising:
an antenna array; and
processing circuitry, the processing circuitry being configured to cause the radio transceiver device to:
configure the antenna array to have a first phase center location (p 1 );
while the antenna array is configured to have the first phase center location obtain a first measurement of the radio signal;
configure the antenna array to have a second phase center location (p 2 ), wherein p 2 is different than p 1 ;
while the antenna array is configured to have the second phase center location obtain a second measurement of the radio signal; and
estimate the angle of arrival of the radio signal using the obtained measurements, wherein
the angle of arrival of the radio signal is estimated using a phase difference between measurements as obtained using the first phase center location (p 1 ) and measurements as obtained using the second phase center location (p 2 ).
2. The radio transceiver device of claim 1 , wherein the radio transceiver device is a radio access network (RAN) node.
3. The radio transceiver device of claim 1 , wherein the radio transceiver device is a user equipment (UE).
4. The radio transceiver device of claim 1 , wherein p 1 and p 2 are separated at least by half a wavelength of an operating frequency of the received radio signal.
5. The radio transceiver device of claim 1 , wherein the antenna array comprises antenna elements, and wherein adjacent antenna elements are separated at least by half a wavelength of an operating frequency of the received radio signal.
6. The radio transceiver device of claim 1 , wherein
the antenna array comprises a first set of antenna elements and a second set of antenna elements,
when the radio signal is received by the antenna array using the first phase center location (p 1 ) only the first set of the antenna elements is used to receive the radio signal,
when the radio signal is received by the antenna array using the second phase center location (p 2 ) only the second set of the antenna elements is used to receive the radio signal, and
the second set of antenna elements is partly but not fully overlapping with the first set of antenna elements.
7. The radio transceiver device of claim 1 , wherein
the antenna array comprises antenna elements, and
the antenna array is configured to shift between the first phase center location and the second phase center location by selectively switching on and off at least one of the antenna elements.
8. The radio transceiver device of claim 7 , wherein at least one of the antenna elements is configured to be selectively switched on and off by selectively switching on and off a low-noise amplifier, an attenuator, or a switch of said at least one of the antenna elements.
9. The radio transceiver device of claim 7 , wherein the antenna elements have two mutually orthogonal polarizations, and wherein both orthogonal polarizations are simultaneously switched on and off as the at least one of the antenna elements is selectively switched on and off.
10. The radio transceiver device of claim 1 , wherein
the antenna array comprises antenna elements, and
the antenna array is configured to shift between the first phase center location and the second phase center location by selectively increasing and reducing gain of a low-noise amplifier of at least one of the antenna elements.
11. The radio transceiver device of claim 1 , wherein the antenna array is configured to simultaneously receive the radio signal in two mutually orthogonal polarizations.
12. The radio transceiver device of claim 11 , wherein one intermediate value of the angle of arrival is estimated for each of the two mutually orthogonal polarizations, and wherein the angle of arrival is estimated using a combination of the intermediate values.
13. The radio transceiver device of claim 1 , wherein
a first receive beam is used to receive the radio signal while the antenna array has the first phase center location (p 1 ),
a second receive beam is used to receive the radio signal while the antenna array has the second phase center location (p 2 ),
the first receive beam is created only using phase shifts of antenna elements of the antenna array, and
the second receive beam is created only using phase shifts of antenna elements of the antenna array.
14. The radio transceiver device of claim 1 , wherein
a first receive beam is used to receive the radio signal while the antenna array has the first phase center location (p 1 ),
a second receive beam is used to receive the radio signal while the antenna array has the second phase center location (p 2 ),
the first receive beam is created using a combination of phase shifts and amplitude tapering of antenna elements of the antenna array, and
the second receive beam is created using a combination of phase shifts and amplitude tapering of antenna elements of the antenna array.
15. The radio transceiver device of claim 1 , wherein
the antenna array is a two-dimensional antenna array, and
the angle of arrival is estimated in two dimensions.
16. The radio transceiver device of claim 1 , wherein
the radio signal is received from a second radio transceiver device, and
the first recited radio transceiver device is configured to: i) select a beam according to the angle of arrival and ii) communicate with the second radio transceiver device using the selected beam.
17. A method for estimating angle of arrival of a radio signal in a radio communications network, the method comprising:
configuring the antenna array to have a first phase center location (p 1 );
while the antenna array is configured to have the first phase center location, obtaining a first measurement of the radio signal;
configure the antenna array to have a second phase center location (p 2 ), wherein p 2 is different than p 1 ;
while the antenna array is configured to have the second phase center location, obtaining a second measurement of the radio signal; and
estimating the angle of arrival of the radio signal using the obtained measurements wherein
estimating the angle of arrival of the radio signal using the obtained measurements comprises estimating the angle of arrival using a phase difference between measurements as obtained using the first phase center location (p 1 ) and measurements as obtained using the second phase center location (p 2 ).
18. The method of claim 17 , wherein the radio transceiver device is a radio access network (RAN) node.
19. The method of claim 17 , wherein the radio transceiver device is a user equipment (UE).
20. The method of claim 17 , wherein p 1 and p 2 are separated at least by half a wavelength of an operating frequency of the received radio signal.
21. The method of claim 17 , wherein the antenna array comprises antenna elements, and wherein adjacent antenna elements are separated at least by half a wavelength of an operating frequency of the received radio signal.
22. The method of claim 17 , wherein
the antenna array comprises a first set of antenna elements and a second set of antenna elements,
when the radio signal is received by the antenna array using the first phase center location (p 1 ) only the first set of the antenna elements is used to receive the radio signal,
when the radio signal is received by the antenna array using the second phase center location (p 2 ) only the second set of the antenna elements is used to receive the radio signal, and
the second set of antenna elements is partly but not fully overlapping with the first set of antenna elements.
23. The method of claim 17 , wherein
the antenna array comprises antenna elements, and
the antenna array is configured to shift between the first phase center location and the second phase center location by selectively switching on and off at least one of the antenna elements.
24. The method of claim 23 , wherein at least one of the antenna elements is configured to be selectively switched on and off by selectively switching on and off a low-noise amplifier, an attenuator, or a switch of said at least one of the antenna elements.
25. The method of claim 23 , wherein the antenna elements have two mutually orthogonal polarizations, and wherein both orthogonal polarizations are simultaneously switched on and off as the at least one of the antenna elements is selectively switched on and off.
26. The method of claim 17 , wherein
the antenna array comprises antenna elements, and
the antenna array is configured to shift between the first phase center location and the second phase center location by selectively increasing and reducing gain of a low-noise amplifier of at least one of the antenna elements.
27. The method of claim 17 , wherein the antenna array is configured to simultaneously receive the radio signal in two mutually orthogonal polarizations.
28. The method of claim 27 , wherein one intermediate value of the angle of arrival is estimated for each of the two mutually orthogonal polarizations, and wherein the angle of arrival is estimated using a combination of the intermediate values.
29. The method of claim 17 , wherein
a first receive beam is used to receive the radio signal while the antenna array has the first phase center location (p 1 ),
a second receive beam is used to receive the radio signal while the antenna array has the second phase center location (p 2 ),
the first receive beam is created only using phase shifts of antenna elements of the antenna array, and
the second receive beam is created only using phase shifts of antenna elements of the antenna array.
30. The method of claim 17 , wherein
a first receive beam is used to receive the radio signal while the antenna array has the first phase center location (p 1 ),
a second receive beam is used to receive the radio signal while the antenna array has the second phase center location (p 2 ),
the first receive beam is created using a combination of phase shifts and amplitude tapering of antenna elements of the antenna array, and
the second receive beam is created using a combination of phase shifts and amplitude tapering of antenna elements of the antenna array.
31. The method of claim 17 , wherein
the antenna array is a two-dimensional antenna array, and
the angle of arrival is estimated in two dimensions.
32. The method of claim 17 , wherein
the radio signal is received from a second radio transceiver device, and
the first recited radio transceiver device is configured to: i) select a beam according to the angle of arrival and ii) communicate with the second radio transceiver device using the selected beam.