Antenna systems and methods for massive MIMO communication
View Patent ↗Antenna systems and methods for Massive Multi-Input-Multi-Output (MIMO) (M-MIMO) communication are provided. Antennas systems include a M-MIMO transmitter architecture with a hybrid matrix structure. The hybrid matrix structure protects against transmit path component failures and ensures that a spatial rate of the MIMO transmitter is not degraded by the failures. Antenna systems and methods also include antenna selection schemes for selecting a subset of antennas from a plurality of antennas to transmit to a receiver.
1. A Multi-Input-Multi-Output (MIMO) antenna system, comprising;
a plurality of first antennas; and
a measurement module, coupled to the plurality of first antennas, configured to estimate a channel from the plurality of first antennas to a plurality of second antennas and to select a subset of the plurality of first antennas for transmitting a plurality of signals to the plurality of second antennas,
wherein a size of the selected subset of the plurality of first antennas is equal to M, and
wherein the measurement module is further configured to, for each subset of size M of the plurality of first antennas:
form, using the estimated channel, a sub-channel matrix h corresponding to a sub-channel between the subset and the plurality of second antennas,
form a channel matrix equal to a product of a conjugate transpose of h by h,
perform a singular value decomposition (SVD) of the channel matrix to determine a unitary matrix U, a diagonal matrix D having positive diagonal elements, and an orthogonal matrix V, and
compute a function of the positive diagonal elements of the diagonal matrix D to select the subset of the plurality of first antennas.
2. The MIMO antenna system of claim 1 , wherein the plurality of first antennas are located at a base station, and the plurality of second antennas are located at a user equipment (UE).
3. The MIMO antenna system of claim 1 , further comprising:
an antenna selection matrix configured to receive the plurality of signals for transmission,
wherein the measurement module is further configured to control the antenna selection matrix to couple the plurality of signals to the selected subset of the plurality of first antennas.
4. The MIMO antenna system of claim 3 , wherein the antenna selection matrix includes an M-input N-output switch matrix, where M is equal to a number of the plurality of signals and N is equal to a number of the plurality of first antennas.
5. The MIMO antenna system of claim 4 , further comprising:
a first M-input M-output hybrid matrix configured to receive a plurality of input signals and to generate a respective plurality of hybrid signals, wherein each of the plurality of hybrid signals is a combination of the plurality of input signals;
a plurality of power amplifiers (PAs) each configured to receive a respective one of the plurality of hybrid signals and to generate a respective one of a plurality of amplified hybrid signals; and
a second M-input M-output hybrid matrix configured to receive the plurality of amplified hybrid signals and to generate the plurality of signals, wherein each of the plurality of signals is a combination of the plurality of amplified hybrid signals.
6. The MIMO antenna system of claim 1 , wherein the measurement module is further configured to receive, from at least one of the plurality of first antennas, a plurality of reference signals transmitted respectively by the plurality of second antennas and to estimate the channel using the plurality of reference signals.
7. The MIMO antenna system of claim 6 , wherein the plurality of reference signals include sounding reference signals (SRS).
8. The MIMO antenna system of claim 1 , wherein the function is a sum of the positive diagonal elements of the diagonal matrix D.
9. The MIMO antenna system of claim 1 wherein the measurement module is further configured to choose a subset with a largest function as the selected subset of the plurality of first antennas.
10. The MIMO antenna system of claim 1 , wherein the function is a logarithmic sum of the positive diagonal elements of the diagonal matrix D.
11. The MIMO antenna system of claim 1 , wherein the plurality of first antennas are located at a user equipment (UE), and the plurality of second antennas are located at a base station.
12. A method for Massive Multi-Input-Multi-Output (MIMO) (M- MIMO) antenna selection, comprising:
estimating a channel from a plurality of first antennas to a plurality of second antennas;
forming, using the estimated channel, a sub-channel matrix h corresponding to a sub-channel between a subset of the plurality of first antennas and the plurality of second antennas;
forming a channel matrix equal to a product of a conjugate transpose of h by h;
performing a singular value decomposition (SVD) of the channel matrix formed using the estimated channel to determine a unitary matrix U, a diagonal matrix D having positive diagonal elements, and an orthogonal matrix V;
computing a function of the positive diagonal elements of the diagonal matrix D to select the subset of the plurality of first antennas; and
transmitting a plurality of signals to the plurality of second antennas using the subset of the plurality of first antennas, wherein a size of the selected subset of the plurality of first antennas is equal to M.
13. The method of claim 12 , wherein the plurality of first antennas are located at a base station, and the plurality of second antennas are located at a user equipment (UE).
14. The method of claim 12 , further comprising:
receiving, from at least one of the plurality of first antennas, a plurality of reference signals transmitted respectively by the plurality of second antennas; and
estimating the channel using the plurality of reference signals.
15. The method of claim 14 , wherein the plurality of reference signals include sounding reference signals (SRS).
16. The method of claim 12 , wherein the function is a sum of the positive diagonal elements of the diagonal matrix D.
17. The method of claim 12 , wherein the function is a logarithmic sum of the positive diagonal elements of the diagonal matrix D.
18. The method of claim 12 , wherein the plurality of first antennas are located at a user equipment (UE), and the plurality of second antennas are located at a base station.
19. A Multi-Input-Multi-Output (MIMO) antenna system, comprising:
a first hybrid matrix configured to receive a plurality of input signals and to generate a respective plurality of hybrid signals, wherein each of the plurality of hybrid signals is a combination of the plurality of input signals;
a plurality of power amplifiers (PAs) each configured to receive a respective one of the plurality of hybrid signals and to generate a respective one of a plurality of amplified hybrid signals;
a second hybrid matrix configured to receive the plurality of amplified hybrid signals and to generate a respective plurality of output signals, wherein each of the plurality of output signals is a combination of the plurality of amplified hybrid signals; and
a plurality of antennas each configured to transmit a respective one of the plurality of output signals.
20. The MIMO antenna system of claim 19 , wherein the first hybrid matrix and the second hybrid matrix have inverse transfer functions.