Beamforming for non-collaborative, space division multiple access systems
A wireless communication system non-collaborative, multiple input, multiple output (MIMO) space division multiple access (SDMA) system determines subscriber station combining and weighting vectors that yield a high average signal-to-interference plus noise ratio (SINR). Each subscriber station independently transmits information to a base station that allows the base station to determine a weight vector w i for each subscriber station using the determined combining vector of the subscriber station. The i th combining vector corresponds to a right singular vector corresponding to a maximum singular value of a channel matrix between a base station and the i th subscriber station. Each subscriber station transmits signals using a weight vector v i , which corresponds to a left singular vector corresponding to a maximum singular value of a channel matrix between the i th subscriber station and the base station. The base station uses the weight vector w i to determine the signal transmitted by the i th subscriber station.
1. A method for operating a user equipment (UE) device that includes a plurality of UE antennas, the method comprising:
determining feedback information based on an estimate of a channel from a base station to the UE device, wherein the feedback information includes information identifying a combining vector, wherein individual components of the combining vector respectively correspond to the UE antennas;
transmitting the feedback information to the base station;
receiving channel output symbols from respective UE antennas in response to a transmission of channel input symbols by the base station; and
recovering an estimate of a data signal by weighting the channel output symbols from the respective UE antennas with respectively corresponding components of the combining vector.
2. The method of claim 1 , wherein the estimate of the channel is determined based on pilot signals that are inserted in a downlink transmission from the base station.
3. The method of claim 1 , wherein the base station is configured to weight the data signal using a weighting vector in order to determine the channel input symbols.
4. The method of claim 3 , wherein the weighting vector is determined based on the feedback information and additional feedback information from one or more additional UE devices.
5. The method of claim 1 , wherein the channel input symbols result from weighting the data signal using a weighting vector.
6. The method of claim 1 , wherein the combining vector is a selected right singular vector of the channel estimate, wherein selected right singular vector corresponds to a maximal singular value of the channel estimate.
7. The method of claim 1 , further comprising:
weighting an uplink signal using a weight vector to obtain transmit signals, wherein the weight vector is determined based on the channel estimate;
transmitting the transmit signals respectively from the UE antennas.
8. A user equipment (UE) device comprising:
a plurality of UE antennas; and
a transceiver coupled to the UE antennas and configured to:
determine feedback information based on an estimate of a channel from a base station to the UE device, wherein the feedback information includes information identifying a combining vector, wherein individual components of the combining vector respectively correspond to the UE antennas;
transmit the feedback information to the base station;
receive channel output symbols from respective UE antennas in response to a transmission of channel input symbols by the base station; and
recover an estimate of a data signal by weighting the channel output symbols from the respective UE antennas with respectively corresponding components of the combining vector.
9. The UE device of claim 8 , wherein the estimate of the channel is determined based on pilot signals that are inserted in a downlink transmission from the base station.
10. The UE device of claim 8 , wherein the base station is configured to weight the data signal using a weighting vector in order to determine the channel input symbols.
11. The UE device of claim 10 , wherein the weighting vector is determined based on the feedback information and additional feedback information from one or more additional UE devices.
12. The UE device of claim 8 , wherein the channel input symbols result from weighting the data signal using a weighting vector.
13. The UE device of claim 8 , wherein the combining vector is a selected right singular vector of the channel estimate, wherein selected right singular vector corresponds to a maximal singular value of the channel estimate.
14. The UE device of claim 8 , wherein the transceiver is further configured to:
weight an uplink signal using a weight vector to obtain transmit signals, wherein the weight vector is determined based on the channel estimate; and
transmit the transmit signals respectively from the UE antennas.
15. A non-transitory memory medium for operating a user equipment (UE) device that includes a plurality of UE antennas, wherein the memory medium stores program instructions, wherein the program instructions, when executed by a processor, cause the UE device to implement:
determining feedback information based on an estimate of a channel from a base station to the UE device, wherein the feedback information includes information identifying a combining vector, wherein individual components of the combining vector respectively correspond to the UE antennas;
transmitting the feedback information to the base station;
receiving channel output symbols from respective UE antennas in response to a transmission of channel input symbols by the base station;
recovering an estimate of a data signal by weighting the channel output symbols from the respective UE antennas with respectively corresponding components of the combining vector.
16. The memory medium of claim 15 , wherein the estimate of the channel is determined based on pilot signals that are inserted in a downlink transmission from the base station.
17. The memory medium of claim 15 , wherein the base station is configured to weight the data signal using a weighting vector in order to determine the channel input symbols.
18. The memory medium of claim 17 , wherein the weighting vector is determined based on the feedback information and additional feedback information from one or more additional UE devices.
19. The memory medium of claim 15 , wherein the channel input symbols result from weighting the data signal using a weighting vector.
20. The memory medium of claim 15 , further comprising:
weighting an uplink signal using a weight vector to obtain transmit signals, wherein the weight vector is determined based on the channel estimate; and
transmitting the transmit signals respectively from the UE antennas.