Phase synchronization and channel reciprocity calibration of antennas via terminal feedback
First Claim
1. A method of phase synchronization and channel reciprocity calibration in a TDD wireless communications network with a predetermined signal bandwidth, wherein said network comprises at least one broadcaster set and at least one terminal set, said broadcaster set comprising at least one broadcaster and a plurality of broadcaster antennas, said terminal set comprising at least one terminal and at least one terminal antenna, comprising:
- (a) sending a downlink calibration signal from said broadcaster set to said terminal set, wherein said downlink calibration signal comprises at least one antenna mapping and a plurality of calibration tones from said broadcaster antennas,(b) sending an uplink calibration signal from said terminal set to said broadcaster set,(c) obtaining a plurality of downlink calibration tone estimates from said downlink calibration signal at said terminal set,(d) sending said plurality of said downlink calibration tone estimates from said terminal set to said broadcaster set,(e) deriving a plurality of broadcaster calibration coefficients for said plurality of said calibration tones from said uplink calibration signal and said plurality of said downlink calibration tone estimates at said broadcaster set, and(f) obtaining a plurality of broadcaster calibration functions within said predetermined signal bandwidth from said plurality of said broadcaster calibration coefficients at said broadcaster set, wherein each of said broadcaster calibration functions is associated with one of said broadcaster antennas.
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Abstract
Multipoint broadcasting relying on channel reciprocity in a TDD network requires that the broadcasters be calibrated. In the cases where the relative amplitude profiles and nonlinear phases are time-invariant or slow-varying, broadcaster calibration reduces to phase synchronization. Methods and apparatus are described that provide broadcaster calibration and phase synchronization with terminal feedback and overcome the drawbacks of self-calibration. The methods and apparatus are capable of calibrating hundreds of broadcaster antennas in massive antenna applications while maintaining an extremely low overhead. Applications of the described methods and apparatus include multipoint broadcasting in wireless networks, also known as coordinated multipoint transmission, or CoMP, in LTE-A (long-term evolution, advanced) networks, and distributed MIMO, massive MIMO, massive beamforming, etc., in other networks including 5G and 802.11. Applications also include frequency and phase synchronization of a cluster of wireless devices.
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Citations
25 Claims
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1. A method of phase synchronization and channel reciprocity calibration in a TDD wireless communications network with a predetermined signal bandwidth, wherein said network comprises at least one broadcaster set and at least one terminal set, said broadcaster set comprising at least one broadcaster and a plurality of broadcaster antennas, said terminal set comprising at least one terminal and at least one terminal antenna, comprising:
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(a) sending a downlink calibration signal from said broadcaster set to said terminal set, wherein said downlink calibration signal comprises at least one antenna mapping and a plurality of calibration tones from said broadcaster antennas, (b) sending an uplink calibration signal from said terminal set to said broadcaster set, (c) obtaining a plurality of downlink calibration tone estimates from said downlink calibration signal at said terminal set, (d) sending said plurality of said downlink calibration tone estimates from said terminal set to said broadcaster set, (e) deriving a plurality of broadcaster calibration coefficients for said plurality of said calibration tones from said uplink calibration signal and said plurality of said downlink calibration tone estimates at said broadcaster set, and (f) obtaining a plurality of broadcaster calibration functions within said predetermined signal bandwidth from said plurality of said broadcaster calibration coefficients at said broadcaster set, wherein each of said broadcaster calibration functions is associated with one of said broadcaster antennas. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. An apparatus for phase synchronization and channel reciprocity calibration in a TDD wireless communications network with a predetermined signal bandwidth, wherein said network comprises at least one broadcaster set and at least one terminal set, said broadcaster set comprising at least one broadcaster and a plurality of broadcaster antennas, said terminal set comprising at least one terminal and at least one terminal antenna, comprising:
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(a) a first downlink transmitter for sending a downlink calibration signal from said broadcaster set to said terminal set, wherein said downlink calibration signal comprises at least one antenna mapping and a plurality of calibration tones from said broadcaster antennas, (b) a first uplink transmitter for sending an uplink calibration signal from said terminal set to said broadcaster set, (c) a calibration tone estimator for obtaining a plurality of downlink calibration tone estimates from said downlink calibration signal at said terminal set, (d) a second uplink transmitter for sending said plurality of said downlink calibration tone estimates from said terminal set to said broadcaster set, (e) a broadcaster calibration coefficient estimator for deriving a plurality of broadcaster calibration coefficients for said plurality of said calibration tones from said uplink calibration signal and said plurality of said downlink calibration tone estimates at said broadcaster set, and (f) a calibration function estimator for obtaining a plurality of broadcaster calibration functions within said predetermined signal bandwidth from said plurality of said broadcaster calibration coefficients at said broadcaster set, wherein each of said broadcaster calibration functions is associated with one of said broadcaster antennas. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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Specification