Technique for full-duplex transmission in many-antenna MU-MIMO systems
Technique for full-duplex transmission in many-antenna multi-user (MU) multiple-input multiple-output (MIMO) systems is presented in this disclosure. An estimate of a self-interference channel between a plurality of transmit antennas and a plurality of receive antennas is first obtained. A precoder for self-interference reduction is generated based on minimizing a self-interference power related to the self-interference channel that is present at the plurality of receive antennas. Transmission data are modified using the precoder by projecting the transmission data onto a defined number of singular vectors of the self-interference channel that correspond to the defined number of smallest singular values of the self-interference channel. Data are received in full-duplex mode via the plurality of receive antennas simultaneously with transmitting the modified transmission data.
1. A method for wireless communications, comprising:
obtaining an estimate of a self-interference channel between a plurality of transmit antennas and a plurality of receive antennas;
generating a self-interference reduction precoder (P self ) using the estimate of the self-interference channel based on minimizing a self-interference power related to the self-interference channel, the self-interference power being present at the plurality of receive antennas, wherein said self-interference reduction precoder (P self ) based on minimizing self-interference power, is defined as:
P
Self
=
arg
min
P
H
Self
P
F
2
,
subject
to
P
H
P
=
I
D
Tx
×
D
Tx
,
wherein P self is a M Tx ×D Tx matrix representing the precoder, H Self is a matrix representing the estimate of the self-interference channel, D Tx is the defined number of singular vectors, and ∥⋅∥ F 2 is the squared Frobenius norm, measuring the total self-interference power; generating, using said precoder (P Self ), a modified version of transmission data for minimizing the self-interference power, the generating comprising projecting the transmission data onto a defined number of singular vectors of the self-interference channel that correspond to the defined number of smallest singular values of the self-interference channel;
transmitting the modified version of the transmission data via the plurality of transmit antennas; and
receiving data via the plurality of receive antennas, the receiving occurring simultaneously with the transmitting of the modified version of the transmission data.
2. The method of claim 1 , wherein the generated precoder comprises a defined number of D Tx orthonormal columns ensuring that D Tx effective antennas are preserved for efficient MU-MIMO downlink signaling.
3. The method of claim 1 , wherein the modified version of the transmission data are projected when being transmitted via the plurality of transmit antennas onto the defined number of left singular vectors of the self-interference channel.
4. The method of claim 1 , further comprising:
processing the received data to cancel an interference of the modified version of the transmission data into the received data, the interference having the self-interference power being minimized.
5. The method of claim 4 , wherein processing the received data to cancel the interference is based on digital cancellation.
6. The method of claim 1 , further comprising:
estimating an effective downlink channel created by operating the precoder on a downlink channel;
generating a second precoder based on the estimated effective downlink channel; and
precoding transmission symbols using the second precoder to generate the transmission data for the precoder,
wherein the second precoder comprises a minimum mean square error (MMSE) based beamforming.
7. The method of claim 1 , further comprising:
partitioning an antenna array into the plurality of transmit antennas and the plurality of receive antennas to reduce the self-interference power below a defined threshold.
8. The method of claim 1 , further comprising:
receiving, at the plurality of receive switched transmit antennas of a base station, first orthogonal pilots transmitted from a plurality of user terminals;
receiving, at the plurality of receive antennas of a base station, second orthogonal pilots transmitted from the plurality of user terminals; and
estimating at least one of uplink channels between a base station and the plurality of user terminals, downlink channels between a base station and the plurality of user terminals, self-interference channels, or interference related to user terminals, based on the first and second orthogonal pilots, wherein user terminals are either (1) user terminals controlled by a network associated with the many-antenna base station or (2) user terminals not controlled b the network or the many-antenna base station.
9. The method of claim 1 , wherein:
switching of said transmitter from transmitter to receiver is further configured to switch the plurality of transmit antennas into a receive mode;
listening, via said plurality of transmit antennas in the receive mode, for one or more signals transmitted from one or more interfering antennas;
receiving interference from antennas that are either controlled by a network associated with the many-antenna base station or not controlled by a network associated with the many-antenna base station; and
estimating self-interference or interference channels from the one or more interfering antennas and apply the method of claim 1 to reduce interference.
10. An apparatus for wireless communications, comprising:
an estimator configured to obtain an estimate of a self-interference channel between a plurality of transmit antennas at the apparatus and a plurality of receive antennas;
a circuit configured to generate a precoder using the estimate of the self-interference channel based on minimizing a self-interference power related to the self-interference channel, the self-interference power being present at the plurality of receive antennas;
said circuit configured to generate a precoder based on minimizing the self-interference power computes:
P
Self
=
arg
min
P
H
Self
P
F
2
,
subject
to
P
H
P
=
I
D
Tx
×
D
Tx
,
where P Self is a M Tx ×D Tx matrix representing the precoder, H Self is a matrix representing the estimate of the self-interference channel, D Tx is the defined number of singular vectors, and ∥⋅∥ F 2 is the squared Frobenius norm, measuring the total self-interference power;
the precoder configured to generate a modified version of transmission data for minimizing the self-interference power by projecting the transmission data onto a defined number of singular vectors of the self-interference channel that correspond to the defined number of smallest singular values of the self-interference channel; and
a transmitter configured to transmit the modified version of the transmission data via the plurality of transmit antennas, wherein
receiving data via the plurality of receive antennas occurs simultaneously with the transmitting the modified version of the transmission data from the transmitter.
11. The apparatus of claim 10 , wherein the modified version of the transmission data are projected when being transmitted via the plurality of transmit antennas onto the defined number of left singular vectors of the self-interference channel.
12. The apparatus of claim 10 , further comprising a receiver configured to:
process the received data to cancel an interference of the modified version of the transmission data into the received data, the interference having the self-interference power being minimized.
13. The apparatus of claim 12 , wherein the receiver comprises a digital cancellation circuit configured to process the received data to cancel the interference.
14. The apparatus of claim 10 , wherein:
the estimator is further configured to estimate an effective downlink channel created by operating the precoder on a downlink channel; and
the circuit is further configured to generate a second precoder based on the estimated effective downlink channel, and wherein
the second precoder is configured to precode transmission symbols to generate the transmission data for the precoder.
15. The apparatus of claim 10 , further comprising:
a processor configured to determine a partition of an antenna array at the apparatus into the plurality of transmit antennas and the plurality of receive antennas to reduce the self-interference power below a defined threshold.
16. The apparatus of claim 10 , further comprising a receiver, wherein:
the transmitter is further configured to switch to a receive mode of operation and receive signals transmitted from one or more wireless devices, via the plurality of RF switched transmit antennas, first orthogonal pilots transmitted from a plurality of user terminals;
the receiver is configured to receive, via the plurality of receive antennas, second orthogonal pilots transmitted from the plurality of user terminals; and
the estimator is further configured to estimate at least one of uplink and downlink channels between the apparatus and the plurality of user terminals, the self-interference channel, or interference related to user terminals, based on the first and second orthogonal pilots, wherein user terminals may be controlled by a network associated with the many-antenna base station or not controlled by a network associated with the many-antenna base station.
17. The apparatus of claim 10 , wherein a number of antennas employed at the apparatus causes further reduction of the self-interference power, and wherein the self-interference power and an inter-terminal interference between a pair of user terminals communicating with the apparatus in accordance with full duplex communication are set to provide a defined capacity of the full duplex communication.
18. The apparatus of claim 10 , wherein:
the transmitter is further configured to transmit pilots from the plurality of transmit antennas; and
the estimator is configured to obtain the estimate of the self-interference channel based on the pilots received at the plurality of receive antennas.
19. The apparatus of claim 10 , wherein:
the transmitter is further configured to switch the plurality of transmit antennas into a receive mode;
the plurality of transmit antennas in the receive mode are configured to listen for one or more signals transmitted from one or more interfering antennas;
said interfering antennas either controlled by a network associated with the many-antenna base station or not controlled by a network associated with the many-antenna base station; and
the estimator is further configured to estimate the interference channel to the one or more interfering antennas and apply the apparatus of claim 10 to reduce interference.