Digital port expansion for hybrid massive MIMO systems

1. A signal transmission method comprising:

receiving from a base band unit M·N digital transmit signal streams, each digital transmit signal stream representing a transmit signal for a different corresponding antenna element of an M×N array of antenna elements;

generating P digital transmit-beam signal streams from the M·N digital transmit signal streams, wherein each of the P digital transmit-beam signal streams is a corresponding linear combination of the M·N digital transmit signal streams;

within an R×T Hybrid Massive MIMO system having R·T antenna elements, by applying appropriate phase shifts in an analog domain, causing the R×T Hybrid Massive MIMO system to simultaneously generate a set of P independent, differently directed transmit beams; and

within the R×T Hybrid Massive MIMO system, mapping each of the P digital transmit beam signal streams to a corresponding different one of the P independent, differently directed transmit beams of the set of P independent, differently directed transmit beams, wherein M, N, P, R and T are integers, wherein R·T M·N, and wherein P<M·N.

2. The signal transmission method of claim 1 , wherein R·T=M·N.

3. The signal transmission method of claim 1 , wherein P is much less than M·N.

4. The signal transmission method of claim 1 , wherein each of the P digital transmit-beam signal streams is a corresponding different linear combination of the M·N digital transmit signal streams.

5. The signal transmission method of claim 4 , wherein each of the P digital transmit-beam signal streams is a corresponding different linear combination of all of the M·N digital transmit signal streams.

6. The signal transmission method of claim 1 , wherein the P independent, differently directed transmit beams of the set of P independent, differently directed transmit beams are narrow beams.

7. The signal transmission method of claim 1 , wherein the R×T Hybrid Massive MIMO system has a field of view and wherein the P independent, differently directed transmit beams of the set of P independent, differently directed transmit beams are arranged to form a full aperture covering set for the field of view.

8. The signal transmission method of claim 1 , wherein the linear combinations used to form the P digital transmit-beam signal streams are defined so as to cause the antenna system to operate as a Digital Massive MIMO system.

9. The signal transmission method of claim 1 , wherein R=T=M=N=P=8.

10. The signal transmission method of claim 1 , wherein all of the R·T antenna elements of the R×T Hybrid Massive MIMO system are used to generate each of the P independent, differently directed transmit beams of the set of P independent, differently directed transmit beams.

11. A signal receiving method comprising:

within an R×T Hybrid Massive MIMO system having R·T antenna elements, by applying appropriate phase shifts in the analog domain, causing the R×T Hybrid Massive MIMO system to simultaneously generate a set of P independent, differently directed receive beams;

simultaneously receiving P received beam signal streams, each received beam signal stream of the P received beam signal streams received over a different corresponding one of the P independent, differently directed receive beams of the set of P independent, differently directed receive beams;

generating M·N digital, up-converted signal streams from the P received beam signal streams, wherein each of the M·N digital, up-converted signal streams is a corresponding different linear combination of the P received beam signal streams; and

sending the M·N digital, up-converted signal streams to a base band unit, wherein M, N, P, R and T are integers, wherein R·T M·N, and wherein P<M·N.

12. The signal receiving method of claim 11 , wherein R·T=M·N.

13. The signal receiving method of claim 11 , wherein P is much less than M·N.

14. The signal receiving method of claim 11 , wherein each of the M·N digital up-converted transmit signal streams is a corresponding different linear combination of the P received beam signal streams.

15. The signal receiving method of claim 14 , wherein each of the M·N digital up-converted transmit signal streams is a corresponding different linear combination of all of the P received beam signal streams.

16. The signal receiving method of claim 11 , wherein the P independent, differently directed receive beams of the set of P independent, differently directed receive beams are narrow beams.

17. The signal receiving method of claim 11 , wherein the R×T Hybrid Massive MIMO system has a field of view and wherein the P independent, differently directed receive beams of the set of P independent, differently directed receive beams are arranged to form a full aperture covering set for the field of view.

18. The signal receiving method of claim 11 , wherein the linear combinations used to form the M·N digital, up-converted signal streams are defined so as to cause the antenna system to operate as a Digital Massive MIMO system.

19. The signal receiving method of claim 11 , wherein R=T=M=N=P=8.

20. The signal receiving method of claim 11 , wherein all of the R·T antenna elements of the R×T Hybrid Massive MIMO system are used to generate each of the P independent, differently directed receive beams of the set of P independent, differently receive transmit beams.

21. An antenna system comprising:

a down converter module having M·N inputs for receiving M·N digital transmit signal streams, each digital transmit signal stream representing a transmit signal for a different corresponding antenna element of an M×N array of antenna elements, said down converter module programmed to generate P digital transmit-beam signal streams from the M·N digital transmit signal streams, wherein each of the P digital transmit-beam signal streams is a corresponding linear combination of the M·N digital transmit signal streams; and

an R×T Hybrid Massive MIMO system having R·T antenna elements, said R×T Hybrid Massive MIMO system configured to apply appropriate phase shifts in an analog domain that cause the R×T Hybrid Massive MIMO system to simultaneously generate a set of P independent, differently directed transmit beams and further configured to map each of the P digital transmit beam signal streams to a corresponding different one of the P independent, differently directed transmit beams of the set of P independent, differently directed transmit beams, wherein M, N, P, R and T are integers, wherein R·T M·N, and wherein P<M·N.

22. The antenna system of claim 21 , wherein each of the P digital transmit-beam signal streams is a corresponding different linear combination of all of the M·N digital transmit signal streams.

23. The antenna system of claim 21 , wherein the R×T Hybrid Massive MIMO system has a field of view and wherein the P independent, differently directed transmit beams of the set of P independent, differently directed transmit beams are arranged to form a full aperture covering set for the field of view.

24. The antenna system of claim 21 , wherein the linear combinations used to form the P digital transmit-beam signal streams are defined so as to cause the antenna system to operate as a Digital Massive MIMO system.

25. The antenna system of claim 21 , wherein the R×T Hybrid Massive MIMO system provides full aperture connectivity for each of the P independent, differently directed transmit beams of the set of P independent, differently directed transmit beams.

26. An antenna system comprising:

an R×T Hybrid Massive MIMO system having R·T antenna elements, said R×T Hybrid Massive MIMO system configured to apply appropriate phase shifts in the analog domain that cause the R×T Hybrid Massive MIMO system to simultaneously generate P independent, differently directed receive beams for receiving P received beam signal streams, each received beam signal stream of the P received beam signal streams received over a different corresponding one of the P differently directed receive beams;

an up-converter module having P inputs for receiving the P received beam signal streams from the R×T Hybrid Massive MIMO system, said up-converter module programmed to generate M·N digital, up-converted signal streams from the P received beam signal streams, wherein each of the M·N digital up-converted signal streams is a corresponding different linear combination of the P received beam signal streams and output the M·N digital up-converted signal streams for a base band unit, wherein M, N, P, R and T are integers, wherein R·T M·N, and wherein P<M·N.

27. The antenna system of claim 26 , wherein each of the M·N digital up-converted transmit signal streams is a corresponding different linear combination of all of the P received beam signal streams.

28. The antenna system of claim 26 , wherein the R×T Hybrid Massive MIMO system has a field of view and wherein the P independent, differently directed receive beams of the set of P independent, differently directed receive beams are arranged to form a full aperture covering set for the field of view.

29. The antenna system of claim 26 , wherein the linear combinations used to form the M·N digital, up-converted signal streams are defined so as to cause the antenna system to operate as a Digital Massive MIMO system.

30. The antenna system of claim 26 , wherein the R×T Hybrid Massive MIMO system provides full aperture connectivity for each of the P independent, differently directed transmit beams of the set of P independent, differently directed transmit beams.