Beam tracking in wireless communication

1. A method comprising:

receiving, at a base station, an unsolicited beam change feedback transmitted by a user equipment, wherein

the user equipment transmits the unsolicited beam change feedback in response to detecting a change in the best beams from the base station to the user equipment,

detecting the change in the best beams from the base station to the user equipment comprises

maintaining a signal power history of previously received beams transmitted by the base station, and

comparing a power of a currently received beam to the powers of the previously received beams; and

applying, at the base station, updated beamforming weights based on the unsolicited beam change feedback to transmit an updated beam to the user equipment.

2. The method of claim 1 , further comprising:

scheduling, at the base station, a periodic opportunity for the user equipment to transmit the unsolicited beam change feedback.

3. The method of claim 1 , further comprising:

at the base station, scheduling a physical uplink control channel resource for the user equipment to transmit a beam change feedback,

wherein said receiving comprises receiving from the user equipment on the physical uplink control channel resource a beam change feedback.

4. The method of claim 3 , further comprising:

issuing, at the base station, in response to receiving the beam change feedback, an uplink grant for the user equipment to communicate to the base station additional information regarding the change in best beams.

5. The method of claim 4 , further comprising:

receiving, at the base station, additional information regarding the updated best beam from the user equipment;

calculating, at the base station, an updated beam direction based on the additional information; and

applying beamforming weights corresponding to the updated beam direction to transmit the updated beam to the user equipment.

6. A method comprising:

providing, at a base station, a beam change feedback channel for a user equipment to communicate an unsolicited beam change feedback;

applying, at the base station, updated beamforming weights based on the unsolicited beam change feedback to transmit an updated beam to the user equipment;

issuing, by the base station, an uplink grant for the user equipment to communicate, to the base station, information regarding the beams received by the user equipment in response to receiving the beam change feedback;

receiving, by the base station, additional information from the user equipment regarding the beams received by the user equipment;

calculating, by the base station, an updated beam direction based on the additional information; and

applying, by the base station, beamforming weights corresponding to the updated beam direction to transmit the updated beam to the user equipment.

7. The method of claim 6 , further comprising:

scheduling, at the base station, a periodic opportunity for the user equipment to transmit the unsolicited beam change feedback.

8. The method of claim 7 , wherein said scheduling comprises scheduling a physical uplink control channel resource.

9. The method of claim 7 , wherein the periodic opportunity is periodic with an offset.

10. The method of claim 7 , wherein a frequency of the periodic opportunity is based on at least one of a measurement and feedback capability of the user equipment.

11. The method of claim 7 , wherein the base station adjusts the frequency of the periodic opportunity based on mobility of the user equipment.

12. The method of claim 7 , wherein the periodic opportunity can be dependent on beam measurement occasions available to the user equipment, so that the user equipment can make an update after a measurement occasion.

13. A user equipment comprising:

a signal power detector configured to detect a change in best beams received by the user equipment from a base station;

a signal power history of previously received beams transmitted by the base station;

a comparator configured to compare a power of a currently received beam to the powers of the previously received beams based on the signal power history with a threshold value; and

a transmitter configured to communicate an unsolicited beam change feedback to the base station regarding beams received by the user equipment from the base station in response to the signal power detector detecting the change in the best beams and the comparator determining the power difference is greater than the threshold.

14. The user equipment of claim 13 , wherein transmitter is configured to transmit the beam change feedback on a beam change feedback channel comprising an opportunity scheduled by the base station on a physical uplink control channel resource.

15. A method executed by a user equipment in a wireless communication system, the method comprising:

detecting a change in best beams received by the user equipment from a base station;

comparing, against a threshold value, a power of a currently received beam to powers of previously received beams based on a signal power history when a change best beams is detected; and

transmitting an unsolicited beam change feedback message to the base station regarding beams received by the user equipment from the base station in response to determining the power difference is greater than the threshold.

16. The method of claim 15 further comprising:

transmitting the unsolicited beam change feedback on a beam change feedback channel comprising an opportunity scheduled by the base station on a physical uplink control channel resource.

17. The method of claim 15 further comprising:

storing strengths of previously received best beams in the signal power history,

wherein said comparing comprises comparing the signal-to-noise ratio of the best beams received by the user equipment to the signal-to-noise ratio of previously received best beams.

18. The method of claim 15 further comprising:

receiving a request from the base station for detailed information regarding the unsolicited beam change feedback;

transmitting comprehensive feedback information to the base station in response to the request from the base station for detailed information.