Systems and methods for radio frequency calibration exploiting channel reciprocity in distributed input distributed output wireless communications
Systems and methods are described for radio frequency (RF) calibration in a multiple antenna system (MAS) with multi-user (MU) transmissions (“MU-MAS”) exploiting uplink/downlink channel reciprocity. The RF calibration is used to compute open-loop downlink precoder based on uplink channel estimates, thereby avoiding feedback overhead for channel state information as in closed-loop schemes. For example, a MU-MAS of one embodiment comprises a wireless cellular network with one or multiple beacon stations, multiple client devices and multiple distributed antennas operating cooperatively via precoding methods to eliminate inter-client interference and increase network capacity.
1. A wireless transceiver station comprising:
(a) a first set of N antennas of the wireless transceiver station in a radio access network (RAN) within a coverage area, where N is an integer greater than 8; and
(b) hard-wired logic connected to each antenna in the first set of N antennas, which when executed causes the wireless transceiver station to perform a method comprising steps of:
(1) sending a plurality of training signals from at least a first antenna of the first set of N antennas to at least a second antenna of the first set of N antennas;
(2) processing the plurality of training signals to estimate a plurality of radio frequency calibration coefficients;
(3) determining uplink (UL) channel state information (CSI) in response to receiving a plurality of UL transmissions by one or more of the first set of N antennas from one or more of a second set of M antennas of a plurality of user equipment devices (UEs);
(4) preconditioning a matrix of UL CSI using the plurality of radio frequency calibration coefficients to obtain a matrix of downlink (DL) CSI; and
(5) based on the matrix of DL CSI, precoding a plurality of radio signals transmitted concurrently by the first set of N antennas, to cause the plurality of radio signals to deliberately interfere to create concurrent, non-interfering channels at a respective location of each antenna in the second set of M antennas.
2. The wireless transceiver station of claim 1 , wherein the DL CSI is derived from the UL CSI using the radio frequency calibration coefficients and reciprocity between UL and DL channels.
3. The wireless transceiver station of claim 1 , wherein the method further performs the step of:
determining the UL CSI from a plurality of UL transmissions received by one or more of the first set of N antennas from one or more of the second set of M antennas.
4. The wireless transceiver station of claim 1 , wherein the RAN has no cells.
5. The wireless transceiver station of claim 1 , wherein the hard-wired logic is also operatively connected to a third set of P antennas of a one or more of a plurality of other wireless transceiver stations that does not include the wireless transceiver station in the RAN.
6. A wireless transceiver station comprising:
(a) a first set of N antennas of the wireless transceiver station in a RAN within a coverage area, where N is an integer greater than 8; and
(b) a processor operatively connected to memory and operatively connected to each antenna in the first set of N antennas, wherein the memory includes instructions stored that in conjunction with hard-wired logic, when executed cause the wireless transceiver station to perform a method comprising steps of:
(1) sending a plurality of training signals from at least a first antenna of the first set of N antennas to at least a second antenna of the first set of N antennas;
(2) processing the plurality of training signals to estimate a plurality of radio frequency calibration coefficients;
(3) determining uplink (UL) channel state information (CSI) in response to receiving a plurality of UL transmissions by one or more of the first set of N antennas from one or more of a second set of M antennas of a plurality of user equipment devices (UEs);
(4) preconditioning a matrix of UL CSI using the plurality of radio frequency calibration coefficients to obtain a matrix of downlink (DL) CSI; and
(5) based on the matrix of DL CSI, precoding a plurality of radio signals transmitted concurrently by the first set of N antennas, to cause the plurality of radio signals to deliberately interfere to create concurrent, non-interfering channels at a respective location of each antenna in the second set of M antennas.
7. The wireless transceiver station of claim 6 , wherein the DL CSI is derived from the UL CSI using the radio frequency calibration coefficients and reciprocity between UL and DL channels.
8. The wireless transceiver station of claim 6 , wherein the method further performs the step of:
determining the UL CSI from a plurality of UL transmissions received by one or more of the first set of N antennas from one or more of the second set of M antennas.
9. The wireless transceiver station of claim 6 , wherein the RAN has no cells.
10. The wireless transceiver station of claim 6 , wherein the hard-wired logic is also operatively connected to a third set of P antennas of a one or more of a plurality of other wireless transceiver stations that does not include the wireless transceiver station in the RAN.
11. The wireless transceiver station of claim 6 , wherein the processor is operatively connected to a third set of P antennas of a one or more of a plurality of other wireless transceiver stations that does not include the wireless transceiver station in the RAN.
12. A method comprising:
(1) sending a plurality of training signals from at least a first antenna of a first set of N antennas of a wireless transceiver station in a RAN within a coverage area, to at least a second antenna of the first set of N antennas, where N is an integer greater than 8;
(2) processing the plurality of training signals to estimate a plurality of radio frequency calibration coefficients;
(3) determining UL CSI in response to receiving a plurality of UL transmissions by one or more of the first set of N antennas from one or more of a second set of M antennas of a plurality of UEs;
(4) preconditioning a matrix of UL CSI using the plurality of radio frequency calibration coefficients to obtain a matrix of DL CSI; and
(5) based on the matrix of DL CSI, precoding a plurality of radio signals transmitted concurrently by the first set of N antennas, to cause the plurality of radio signals to deliberately interfere to create concurrent, non-interfering channels at a respective location of each antenna in the second set of M antennas.
13. The method of claim 12 , further comprising the step of:
deriving the DL CSI from the UL CSI using the radio frequency calibration coefficients and reciprocity between UL and DL channels.
14. The method of claim 12 , further comprising the step of:
determining the UL CSI from a plurality of UL transmissions received by one or more of the first set of N antennas from one or more of the second set of M antennas.
15. The method of claim 12 , wherein the RAN has no cells.
16. The method of claim 12 , wherein each antenna in the first set of N antennas is operatively connected to hard-wired logic.
17. The method of claim 12 , wherein each antenna in the first set of N antennas is operatively connected to a processor operatively connected to memory.
18. The method of claim 12 , wherein each antenna in the first set of N antennas is operatively connected to hard-wired logic and to a processor operatively connected to memory.
19. The method of claim 12 , wherein each antenna in the first set of N antennas is operatively connected to hard-wired logic and the hard-wired logic is also operatively connected to a third set of P antennas of a second wireless transceiver station in the RAN, where P is an integer greater than 8.
20. The method of claim 12 , wherein each antenna in the first set of N antennas is operatively connected to a processor operatively connected to memory and the processor is also operatively connected to a third set of P antennas of a second wireless transceiver station in the RAN, where P is an integer greater than 8.
21. A method comprising:
(1) estimating a plurality of radio frequency calibration coefficients for a first set of N antennas of a wireless transceiver station in a RAN within a coverage area where N is an integer greater than 8;
(2) determining uplink (UL) channel state information (CSI) in response to receiving a plurality of UL transmissions by one or more of the first set of N antennas from one or more of a second set of M antennas of a plurality of UEs;
(3) preconditioning a matrix of UL CSI using the plurality of radio frequency calibration coefficients to obtain a matrix of DL CSI;
(4) based on the matrix of DL CSI, precoding a plurality of radio signals transmitted concurrently by the first set of N antennas, to cause the plurality of radio signals to deliberately interfere to create concurrent, non-interfering channels at a respective location of each antenna in the second set of M antennas.
22. The method of claim 21 , further comprising the step of:
deriving the DL CSI from the UL CSI using the radio frequency calibration coefficients and reciprocity between UL and DL channels.
23. The method of claim 21 , further comprising the step of:
determining the UL CSI from a plurality of UL transmissions received by one or more of the first set of N antennas from one or more of the second set of M antennas.
24. The method of claim 21 , wherein the RAN has no cells.
25. The method of claim 21 , wherein each antenna in the first set of N antennas is operatively connected to hard-wired logic.
26. The method of claim 21 , wherein each antenna in the first set of N antennas is operatively connected to a processor operatively connected to memory.
27. The method of claim 21 , wherein each antenna in the first set of N antennas is operatively connected to hard-wired logic and to a processor operatively connected to memory.
28. The method of claim 21 , wherein each antenna in the first set of N antennas is operatively connected to hard-wired logic and the hard-wired logic is also operatively connected to a third set of P antennas of a second wireless transceiver station in the RAN, where P is an integer greater than 8.
29. The method of claim 21 , wherein each antenna in the first set of N antennas is operatively connected to a processor operatively connected to memory and the processor is also operatively connected to a third set of P antennas of a second wireless transceiver station in the RAN, where P is an integer greater than 8.
30. The method of claim 21 , wherein each antenna in the first set of N antennas is operatively connected to hard-wired logic and to a processor operatively connected to memory and the hard-wired logic and the processor are operatively connected to a third set of P antennas of a second wireless transceiver station in the RAN, where P is an integer greater than 8.