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:
receiving downlink pilot signals from a base station;
determining, based on the pilot signals, a combining vector for receiving signals from the base station through the plurality of UE antennas, wherein individual components of the combining vector respectively correspond to the plurality of UE antennas;
transmitting a known pilot sequence to the base station using the determined combining vector;
receiving, through the plurality of UE antennas, a communication signal from the base station after transmitting the known pilot sequence; and
determining using the combining vector, the data carried in the received communication signal.
2. The method of claim 1 , further comprising:
receiving channel output symbols from respective UE antennas of the plurality of 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 of the plurality of UE antennas with respectively corresponding components of the combining vector.
3. The method of claim 1 , wherein the combining vector is determined based on an estimate of the channel using the pilot signals from the base station.
4. The method of claim 1 , wherein the base station is configured to weight a data signal using a weighting vector in order to determine channel input symbols received by the UE device.
5. The method of claim 4 , wherein the weighting vector is based on the known pilot sequence sent to the base station using the determined combining vector.
6. The method of claim 5 , wherein the weighting vector is further based on uplink transmissions from one or more additional UE devices.
7. The method of claim 1 , wherein the combining vector is a selected right singular vector of a channel estimate, wherein selected right singular vector corresponds to a maximal singular value of the channel estimate.
8. A user equipment (UE) device comprising:
a plurality of UE antennas; and
a transceiver coupled to the UE antennas and configured to:
receive downlink pilot signals from a base station;
determine, based on the pilot signals, a combining vector for receiving signals from the base station through the plurality of UE antennas, wherein individual components of the combining vector respectively correspond to the plurality of UE antennas;
transmit a known pilot sequence to the base station using the determined combining vector;
receive, through the plurality of LTE antennas, a communication signal from the base station after transmitting the known pilot sequence; and
determine, using the combining vector, the data carried in the received communication signal.
9. The UE device of claim 8 , wherein the ransceiver is further configured to:
receive channel output symbols from respective UE antennas of the plurality of 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 of the plurality of UE antennas with respectively corresponding components of the combining vector.
10. The UE device of claim 8 , wherein the transceiver is further configured to determine the combining vector based on an estimate of the channel using the pilot signals from the base station.
11. The UE device of claim 8 , wherein the base station is configured to weight a data signal using a weighting vector in order to determine channel input symbols received by the UE device.
12. The UE device of claim 11 , wherein the weighting vector is based on the known pilot sequence sent to the base station using the determined combining vector.
13. The UE device of claim 12 , wherein the weighting vector is further based on uplink transmissions from one or more additional UE devices.
14. The UE device of claim 8 , wherein the combining vector is a selected right singular vector of a channel estimate, wherein selected right singular vector corresponds to a maximal singular value of the channel estimate.
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:
receiving downlink pilot signals from a base station;
determining, based on the pilot signals, a combining vector for receiving signals from the base station through the plurality of UE antennas, wherein individual components of the combining vector respectively correspond to the plurality of UE antennas;
transmitting a known pilot sequence to the base station using the determined combining vector;
receiving, through the plurality of UE antennas, a communication signal from the base station after transmitting the known pilot sequence; and
determining, using the combining vector, the data carried in the received communication signal.
16. The memory medium of claim 15 , wherein the program instructions, when executed by the processor, further cause the UE device to implement:
receiving channel output symbols from respective UE antennas of the plurality of 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 of the plurality of UE antennas with respectively corresponding components of the combining vector.
17. The memory medium of claim 15 , wherein the combining vector is determined based on an estimate of the channel using the pilot signals from the base station.
18. The memory medium of claim 15 , wherein the base station is configured to weight a data signal using a weighting vector in order to determine channel input symbols received by the UE device.
19. The memory medium of claim 18 , wherein the weighting vector is based on the known pilot sequence sent to the base station using the determined combining vector, and wherein the weighting vector is further based on uplink transmissions from one or more additional UE devices.
20. The memory medium of claim 15 , wherein the combining vector is a selected right singular vector of a channel estimate, wherein selected right singular vector corresponds to a maximal singular value of the channel estimate.