Coordinated multipoint systems

1. A central processor, comprising:

a fronthaul network transceiver communicatively coupled to a plurality of geographically distributed base transceiver stations via a fronthaul network, the base transceiver stations configured to employ overlapping coverage areas in a Radio Access Network (RAN) to serve a plurality of User Equipments (UEs); and

a cooperative Multiple-Input, Multiple-Output (MIMO) processor configured for:

selecting a plurality of antennas residing on multiple ones of the plurality of geographically distributed base transceiver stations to receive transmissions from each of the plurality of UEs;

collecting RAN signals received by the plurality of antennas;

computing baseband spatial demultiplexing weights for the RAN signals, the baseband spatial demultiplexing weights computed from RAN channel state information; and

combining weighted RAN signals to exploit multipath in the RAN to separate interfering UE transmissions received by the plurality of antennas.

2. The central processor recited in claim 1 , wherein at least one of the RAN channel state information and the demultiplexing weights are computed using at least one of calibrated techniques and non-calibrated techniques.

3. The central processor recited in claim 1 , wherein the Cooperative MIMO processor is configured for at least one of receiving the RAN channel state information estimated at the plurality of UEs and fed back to the plurality of geographically distributed base transceiver stations, receiving the RAN channel state information derived at the geographically distributed base transceiver stations from signals transmitted by the plurality of UEs, and receiving the RAN channel state information derived at the central processor.

4. The central processor recited in claim 1 , comprising at least one of the plurality of geographically distributed base transceiver stations.

5. The central processor recited in claim 1 , wherein at least one of the plurality of UEs, the plurality of geographically distributed base transceiver stations, and the central processor comprises a blind-adaptive processor configured to compute the RAN channel state information based on at least one of estimates of received data and a known property of a received data signal.

6. The central processor recited in claim 1 , comprising a software-defined radio equipped with programmable computational capability configured to perform baseband signal processing.

7. The central processor recited in claim 6 , wherein the software-defined radio is configured to perform processing for multiple layers of a protocol stack for at least one transmission protocol.

8. The central processor recited in claim 6 , wherein the software-defined radio resides on a distributed computing system.

9. The central processor recited in claim 1 , wherein the cooperative MIMO processor is configured to adapt at least one of selecting the plurality of antennas, collecting the RAN signals, computing the baseband demultiplexing weights, and combining the weighted RAN signals with respect to at least one of changing RAN channel conditions, changing UE locations, and changing base transceiver station locations.

10. A base transceiver station, comprising:

a radio access network (RAN) transceiver comprising at least one antenna configured to receive radio-frequency (RF) signals from the RAN;

at least one fronthaul interface that communicatively couples the base transceiver station to a fronthaul network;

a channel state processing system configured to communicate RAN channel state information from the base transceiver station to a central processor via the fronthaul network; and

a cooperative multiple-input, multiple-output (MIMO) processor communicatively coupled to the fronthaul network and configured to receive RAN channel state information from the RAN transceiver and at least one other base transceiver station;

select a plurality of antennas residing on multiple ones of the base transceiver station and the at least one other base transceiver station to receive transmissions from each of a plurality of User Equipments (UEs);

collect RAN signals received by the plurality of antennas;

compute baseband spatial demultiplexing weights for the RAN signals, the baseband spatial demultiplexing weights computed from the RAN channel state information; and

combine weighted RAN signals to exploit multipath in the RAN to separate interfering UE transmissions received by the plurality of antennas.

11. The base transceiver station recited in claim 10 , further comprising at least one of a timing reference receiver and a clock configured for use in regulating timing of signal-processing operations.

12. The base transceiver station recited in claim 10 , comprising a channel estimator configured to calculate the RAN channel state information by measuring training signals transmitted in the RAN.

13. The base transceiver station recited in claim 12 , wherein the channel estimator is configured to compute the RAN channel state information using at least one of calibrated techniques and non-calibrated techniques.

14. The base transceiver station recited in claim 12 , wherein the channel estimator comprises a blind-adaptive processor configured to compute the RAN channel state information based on at least one of data estimates from a received transmission and a known property of data in the received transmission.

15. The base transceiver station recited in claim 10 , wherein the at least one fronthaul interface comprises at least one of an optical fiber interface, a wireline interface, a radio interface, and a wireless optical interface.

16. A system, comprising:

a plurality of geographically distributed base transceiver stations configured to employ overlapping coverage areas in a Radio Access Network (RAN) to serve a plurality of User Equipments (UEs);

a fronthaul network communicatively coupling the plurality of geographically distributed base transceiver stations to a central processor; and

the central processor comprising a cooperative multiple-input, multiple-output (MIMO) processor configured for:

selecting a plurality of antennas residing on multiple ones of the plurality of geographically distributed base transceiver stations to receive transmissions from each of the plurality of UEs;

collecting RAN signals received by the plurality of antennas;

computing baseband spatial demultiplexing weights for the RAN signals, the baseband spatial demultiplexing weights computed from RAN channel state information; and

combining weighted RAN signals to exploit multipath in the RAN to separate interfering UE transmissions received by the plurality of antennas.

17. The system recited in claim 16 , wherein at least one of the central processor, the plurality of geographically distributed base transceiver stations, and the plurality of UEs is configured to calculate the RAN channel state information.

18. The system recited in claim 16 , wherein the central processor resides in one of the plurality of geographically distributed base transceiver stations.

19. The system recited in claim 16 , wherein the cooperative MIMO processor is configured to adapt at least one of selecting the plurality of antennas, collecting the RAN signals, computing the baseband demultiplexing weights, and combining the weighted RAN signals with respect to at least one of changing RAN channel conditions, changing UE locations, and changing base transceiver station locations.

20. The system recited in claim 16 , wherein the central processor comprises a software-defined radio platform programmed to support a plurality of transmission protocols.

21. The system recited in claim 16 , wherein the central processor comprises a distributed computing system.