Systems and methods for beamforming in a massive MIMO system

1. A method for conveying a beamforming vector from a first transceiver to a second transceiver, comprising:

receiving, using a plurality of first antennas of the first transceiver, a plurality of first reference signals transmitted respectively from a plurality of second antennas of the second transceiver;

estimating a channel from the plurality of second antennas to the plurality of first antennas based on the plurality of first reference signals;

decomposing the channel into a first unitary matrix, a diagonal matrix, and a second unitary matrix; and

transmitting, from the plurality of first antennas, one or more beamformed reference signals, the one or more beamformed reference signals resulting from multiplying one or more second reference signals by respective vectors of the first unitary matrix of the channel,

wherein said transmitting comprises transmitting, from the plurality of first antennas, a first beamformed reference signal simultaneously on a same frequency by each of the plurality of first antennas, the first beamformed reference signal resulting from multiplying a respective one of the one or more second reference signals by a first column vector of the first unitary matrix of the channel.

2. The method of claim 1 , wherein the plurality of first reference signals include sounding reference signals.

3. The method of claim 1 , wherein decomposing the channel comprises performing a singular value decomposition of the channel.

4. The method of claim 1 , wherein an estimate of the channel based on the first beamformed reference signal at the second transceiver is proportional to the beamforming vector being conveyed from the first transceiver to the second transceiver.

5. The method of claim 1 , wherein the beamforming vector enables maximum ratio transmission (MRT) beamforming from the second transceiver to the first transceiver over the channel.

6. The method of claim 1 , wherein the one or more second reference signals include Demodulation Reference Signals (DMRS).

7. The method of claim 1 , wherein the first transceiver is a base station and the second transceiver is a user equipment (UE).

8. A transceiver, comprising:

a plurality of first antennas configured to receive a plurality of first reference signals transmitted respectively from a plurality of second antennas of another transceiver;

a channel estimator configured to estimate a channel from the plurality of second antennas to the plurality of first antennas based on the plurality of first reference signals;

a decomposition module configured to decompose the channel into a first unitary matrix, a diagonal matrix, and a second unitary matrix; and

a beamforming module configured to multiply one or more second reference signals by respective vectors of the first unitary matrix of the channel to generate one or more beamformed reference signals,

wherein the one or more beamformed reference signals include a first beamformed reference signal, the first beamformed reference signal resulting from multiplying a respective one of the one or more second reference signals by a first column vector of the first unitary matrix of the channel, and

wherein the plurality of first antennas are further configured to simultaneously transmit on a same frequency the first beamformed reference signal to the other transceiver.

9. The transceiver of claim 8 , wherein the plurality of first reference signals include sounding reference signals.

10. The transceiver of claim 8 , wherein the decomposition module is further configured to perform a singular value decomposition of the channel.

11. The transceiver of claim 8 , wherein the one or more second reference signals include Demodulation Reference Signals (DMRS).

12. The transceiver of claim 8 , wherein the plurality of first antennas are further configured to transmit the one or more beamformed reference signals simultaneously to the other transceiver on orthogonal frequency resources.

13. The transceiver of claim 8 , wherein the transceiver is a base station and the other transceiver is a user equipment (UE).

14. A base station, comprising:

a plurality of first antennas;

a decomposition module configured to decompose a channel from a plurality of second antennas of a user equipment (UE) to the plurality of first antennas into a first unitary matrix, a diagonal matrix, and a second unitary matrix; and

a beamforming module configured to multiply one or more reference signals by respective vectors of the first unitary matrix of the channel to generate one or more beamformed reference signals,

wherein the one or more beamformed reference signals include a first beamformed reference signal, the first beamformed reference signal resulting from multiplying a respective one of the one or more reference signals by a first column vector of the first unitary matrix of the channel, and

wherein the plurality of first antennas are configured to simultaneously transmit on a same frequency the first beamformed reference signal to the UE.

15. The base station of claim 14 , wherein the plurality of first antennas are further configured to receive a plurality of first reference signals transmitted respectively from the plurality of second antennas of the UE.

16. The base station of claim 15 , further comprising:

a channel estimator configured to estimate the channel based on the plurality of first reference signals.

17. The base station of claim 14 , wherein the plurality of first antennas are further configured to transmit the one or more beamformed reference signals to the UE.

18. The base station of claim 15 , wherein the plurality of first reference signals include sounding reference signals.

19. The base station of claim 14 , wherein the decomposition module is further configured to perform a singular value decomposition of the channel.

20. The base station of claim 14 , wherein the one or more reference signals include Demodulation Reference Signals (DMRS).