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 wireless device comprising:
a receiver configured to receive signals on k multiple antennas, wherein “k” is an integer greater than one (1);
a module configured to:
combine, during at least a first period of time, the signals using a combining vector v 1 , wherein the combining vector v 1 corresponds to a right singular vector corresponding to a substantially maximal singular value of channel matrix H 1 , wherein H 1 represents a channel between the first device and a second device; and
determine, during at least the first period of time, a data signal using the combining vector v 1 ; and
a transmitter configured to transmit information that allows another device to use the combining vector v 1 to design a weight vector.
2. The device of claim 1 , the transmitter further configured to transmit a signal to the another device using a weight vector v 1 , wherein the weight vector v 1 corresponds to a left singular vector corresponding to the maximal singular value of an uplink channel matrix H i .
3. The device of claim 1 , the module further configured to:
determine whether the combining vector v 1 or a combining vector v A provides better signal-to-interference plus noise ratio; and
during at least a second period of time, determine the data signal using the combining vector v 1 if the combining vector v 1 provides a better signal-to-interference plus noise ratio and otherwise determining the combined signal using the combining vector v A .
4. The device of claim 3 wherein the combining vector v A is determined based on statistical interference and instantaneous interference.
5. The device of claim 1 , the module further configured to determine the combining vector v 1 using a processor of the first device.
6. The device of claim 1 , the module further configured to determine the combining vector v 1 independently of combining vectors and channel matrices of all other devices in the MIMO-SDMA system.
7. The device of claim 1 wherein:
y 1 is a k element reception vector for the wireless device;
w 1 H is an N element, conjugate transpose of a signal weighting vector w 1 ;
y 1 =s 1 H 1 H w 1 +interference;
z 1 represents the combined signal; and
the module configured to determine the data signal using the combining vector v 1 includes the module further configured to determine a dot product of a conjugate transpose of the combining vector v 1 and the reception vector y 1 such that zi=v 1 H y 1 and z 1 represents the data signal.
8. The device of claim 1 wherein the information transmitted to the another device allows the another device to use the combining vector v 1 to generate a weight vector for transmission of signals from the second device to the first device.
9. A wireless device comprising:
a module configured to determine a weight vector v 1 corresponding to a left singular vector corresponding to a substantially maximal singular value of channel matrix H 1 , wherein H 1 represents a channel between a first device and a second device;
a transmitter configured to transmit information to another device from the wireless device that allows the another device to use a combining vector v 1 corresponding to a right singular vector corresponding to a substantially maximal singular value of channel matrix H 1 to design a weight vector w 1 ; and
the transmitter further configured to transmit a signal to the another device using the weight vector v 1 .
10. A wireless device comprising:
a module configured to estimate a channel matrix H 1 representing a channel to a first receiving device; and
a transmitter configured to transmit a first feedback vector or information representative thereof to a first transmitting device that allows the first transmitting device to use the first feedback vector along with other feedback vectors from other receiving devices to design a weight vector w 1 for the first receiving device, wherein the first transmitting device does not feed forward the weight vector w 1 to the first receiving device.
11. The device of claim 10 , the module further configured to determine a combining vector v 1 based on an estimated channel matrix H 1 at the first receiving device, where the combining vector v 1 is used for receiving signals on k multiple antennas of the first receiving device, wherein k is an integer greater than one.
12. The device of claim 11 , the transmitter configured to transmit the first feedback vector or information representative thereof includes the transmitter further configured to transmit the first feedback vector which is a function of the combining vector v 1 and the channel matrix H 1 or information representative thereof to the first transmitting device.
13. The device of claim 11 , the transmitter configured to transmit the first feedback vector or information representative thereof includes the transmitter further configured to transmit the first feedback vector which is a product of the combining vector v 1 and the channel matrix H 1 or information representative thereof to the first transmitting device.