Transmitter and receiver calibration for obtaining the channel reciprocity for time division duplex MIMO systems
First Claim
1. A communication device having a receive path comprising:
- a number M antennas and respective radio modules, wherein the M antennas and respective radio modules support N×
N multiple-input multiple-output (MIMO) transmissions and receptions, wherein M≧
N;
a processor operable in a baseband domain and configured to perform a self-calibration procedure by which a correction factor is computed for a channel reciprocity level, determined by said self-calibration procedure;
a plurality of switches and receive paths in each one of said radio modules, said switches configured to select a receive path for regular MIMO operation or a plurality of receive paths during said self-calibration procedure, wherein at least one of said plurality of receive paths includes a path loss element between the respective antenna and a low noise amplifier (LNA); and
a digital attenuator configured to adjust calibration signals in the baseband domain, wherein the M antennas are configured to alternate transmitting and receiving periods on a single channel according to a time division duplex (TDD) communication protocol, wherein the M antennas are configured to define phases employed in MIMO transmission and selected using information measured at the communication device during the receiving periods based on the channel reciprocity level,wherein the digital attenuator is further configured to digitally attenuate the calibration signals by an amount that is sufficient to prevent the LNA in one of the plurality of receive paths that is undergoing calibration from saturating,wherein the communication device is further operable to perform the self-calibration procedure in which a first antenna/radio pair (i and j), (i) acts as a transmitter and the other antenna/radio (j) acts as the receiver during the self-calibration procedure, the self-calibration procedure comprising;
performing the following for each of the two antennas/radios (i and j);
emitting a first calibration signal with a signal strength equivalent to a signal strength used during regular MIMO operation, the receiver using the receive path with the path loss element to prevent the LNA from saturation and recording a received calibration signal Ra—
ji;
transmitting a second calibration signal that is digitally attenuated, the receiver continually employing the same one receive path used in said emitting step and recording a received calibration signal Rb—
ji;
transmitting a third calibration signal that is digitally attenuated, the receiver switch selecting the receive path used for regular MIMO operation and recording a received calibration signal Rc—
ji; and
reversing roles of transmitter and receiver for the two antennas/radios (i and j) to repeat said self-calibration procedure and recording the measured calibrated signals;
Ra—
ij, Rb—
ij, and Rc—
ij.
1 Assignment
0 Petitions
Accused Products
Abstract
A communication device operating in time division duplex (TDD) mode using multiple antennas is provided herein. The communication device uses receive channel estimation measurements to perform transmit beamforming and multiple input multiple output (MIMO) transmission, based on self-calibration of the various up/down paths via a method of transmission and reception between its own antennas, thus achieving reciprocity mapping between up and down links. Either user equipment (UE) or a base station may routinely perform this self-calibration to obtain the most current correction factor for the channel reciprocity to reflect the most current operating conditions present during TDD MIMO operation.
353 Citations
12 Claims
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1. A communication device having a receive path comprising:
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a number M antennas and respective radio modules, wherein the M antennas and respective radio modules support N×
N multiple-input multiple-output (MIMO) transmissions and receptions, wherein M≧
N;a processor operable in a baseband domain and configured to perform a self-calibration procedure by which a correction factor is computed for a channel reciprocity level, determined by said self-calibration procedure; a plurality of switches and receive paths in each one of said radio modules, said switches configured to select a receive path for regular MIMO operation or a plurality of receive paths during said self-calibration procedure, wherein at least one of said plurality of receive paths includes a path loss element between the respective antenna and a low noise amplifier (LNA); and a digital attenuator configured to adjust calibration signals in the baseband domain, wherein the M antennas are configured to alternate transmitting and receiving periods on a single channel according to a time division duplex (TDD) communication protocol, wherein the M antennas are configured to define phases employed in MIMO transmission and selected using information measured at the communication device during the receiving periods based on the channel reciprocity level, wherein the digital attenuator is further configured to digitally attenuate the calibration signals by an amount that is sufficient to prevent the LNA in one of the plurality of receive paths that is undergoing calibration from saturating, wherein the communication device is further operable to perform the self-calibration procedure in which a first antenna/radio pair (i and j), (i) acts as a transmitter and the other antenna/radio (j) acts as the receiver during the self-calibration procedure, the self-calibration procedure comprising; performing the following for each of the two antennas/radios (i and j); emitting a first calibration signal with a signal strength equivalent to a signal strength used during regular MIMO operation, the receiver using the receive path with the path loss element to prevent the LNA from saturation and recording a received calibration signal Ra — ji;transmitting a second calibration signal that is digitally attenuated, the receiver continually employing the same one receive path used in said emitting step and recording a received calibration signal Rb — ji;transmitting a third calibration signal that is digitally attenuated, the receiver switch selecting the receive path used for regular MIMO operation and recording a received calibration signal Rc — ji; andreversing roles of transmitter and receiver for the two antennas/radios (i and j) to repeat said self-calibration procedure and recording the measured calibrated signals;
Ra— ij, Rb— ij, and Rc— ij. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method comprising:
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deploying a number M antennas and respective radio modules, wherein the M antennas and respective radio modules support N×
N multiple-input multiple-output (MIMO) transmissions and receptions, wherein M≧
N;using a processor to perform a self-calibration procedure; selecting, from a plurality of receive paths using at least one of a plurality of switches in each radio module, a receive path for regular MIMO operation or a plurality of receive paths during said self-calibration method, and wherein a path loss element is included in at least one receive path between the respective antenna and a low noise amplifier (LNA); adjusting calibration signals in the baseband domain using a digital attenuator, to compute a correction factor for a channel reciprocity level in a communication device; alternatively transmitting and receiving with an antenna set for alternating periods on a single channel according to a TDD communication protocol; defining phases employed in MIMO transmissions for selecting said antenna set based on information measured at the communication device during the receiving periods and the channel reciprocity level; digitally attenuating the calibration signals by an amount that is sufficient to prevent the LNA in one of the paths that is undergoing calibration from saturating; and performing the self-calibration procedure on a first antenna/radio pair in which a first antenna/radio pair (i and j), (i) acts as a transmitter and the other antenna/radio (j) acts as the receiver during the self-calibration procedure, the self-calibration procedure comprising; performing the following for each of the two antennas/radios (i and j); emitting a first calibration signal with a signal strength equivalent to a signal strength used during regular MIMO operation, the receiver using the receive path with the path loss element to prevent the LNA from saturation and recording a received calibration signal Ra — ji;transmitting a second calibration signal that is digitally attenuated, the receiver continually employing the same one receive path used in said emitting step and recording a received calibration signal Rb — ji;transmitting a third calibration signal that is digitally attenuated, the receiver switch selecting the receive path used for regular MIMO operation and recording a received calibration signal Rc — ji; andreversing roles of transmitter and receiver for the two antennas/radios (i and j) to repeat said self-calibration procedure and recording the measured calibrated signals;
Ra— ij, Rb— ij, and Rc— ij. - View Dependent Claims (8, 9, 10, 11, 12)
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Specification