Method and apparatus for performing stream weighting in an SDMA communication system
View Patent ↗A method and apparatus for performing stream weighting in a spatial-division multiple access communication system is provided herein. During operation the base station receiver receives channel information from mobiles (also known as users or nodes) and calculates transmit antenna weights that that maximize the power delivered to each mobile while allowing for a small amount of crosstalk to exist between users. Information or data is transmitted to the nodes utilizing the appropriate stream weights. By allowing tolerable amounts of cross talk, the coherent gain to the desired SDMA user can be increased, and thus the overall performance is improved.
1. A method for performing stream weighting in a spatial division multiple access (SDMA) communication system, the method comprising the steps of:
receiving a plurality of data streams for each of a plurality of nodes;
determining downlink channel information from the plurality of nodes;
choosing an allowable amount of crosstalk based on the determined downlink channel information;
creating, by a base station, a mathematical channel having the allowable amount of crosstalk, wherein the mathematical channel is a multiplication of a channel matrix for node u by an inverse matrix containing channels to other nodes;
computing stream weights based on the mathematical channel for each of the plurality of data streams, wherein the stream weights maximize power to node u while allowing at least the allowable amount of crosstalk to exist at the other nodes;
weighting the plurality of data streams with the stream weights; and
transmitting the weighted data streams to the plurality of nodes.
2. The method of claim 1 wherein the step of creating, by the base station, the mathematical channel comprises the step of computing a mathematical channel which is a multiplication of a channel matrix for the node u by a projection matrix designed to give a desired level of crosstalk.
3. The method of claim 1
wherein the step of creating, by the base station, the mathematical channel is based on the downlink channel information from the plurality of nodes.
4. A method in a communication device comprising the steps of:
determining downlink channel information from a plurality of nodes;
determining a crosstalk threshold based on the downlink channel information;
creating, by a base station, a mathematical channel having an allowable amount of crosstalk, wherein the mathematical channel is a multiplication of a channel matrix for node u by an inverse matrix containing channels to other nodes; and
computing antenna weights for the mathematical channel, wherein the antenna weights are based on the crosstalk threshold and the mathematical channel.
5. The method of claim 4 further comprising the step of:
transmitting data to the plurality of nodes, wherein the data is weighted with the antenna weights.
6. The method of claim 4 wherein the crosstalk threshold enables an allowable amount of crosstalk.
7. The method of claim 4 wherein the antenna weights are designed for a plurality of data streams to each of the plurality of nodes.
8. An apparatus comprising:
stream weighting circuitry for
receiving a plurality of data streams for each of a plurality of nodes,
determining downlink channel information from the plurality of nodes, wherein the down link, channel in information is utilized to choose an allowable amount of crosstalk;
creating, by a base station, a mathematical channel having the allowable amount of crosstalk, wherein the mathematical channel is a multiplication of a channel matrix for node u by an inverse matrix containing channels to other nodes,
computing stream weights based on the mathematical channel for each of the plurality of data streams, wherein the stream weights maximize power to node u while allowing at least the allowable amount of crosstalk to exist at the other nodes, and
weighting the plurality of data streams with the stream weights; and
transmit circuitry for transmitting the weighted streams to the plurality of nodes.
9. The apparatus of claim 8 wherein the mathematical channel is a multiplication of a channel matrix for the node u by a projection matrix designed to give a desired level of crosstalk.
10. The apparatus of claim 8 further comprising:
a receiver receiving the downlink channel information from the plurality of nodes; and
wherein the stream weights are based on the downlink channel information from the plurality of nodes.