Method and apparatus for performing spatial-division multiple access
A method and apparatus for performing spatial-division multiple access within a communication system is provided herein. During operation, nodes will return null subspace information along with their channel subspace information. The null subspace is similar to the channel subspace except that the null subspace information directs a base station to the matrix in a predefined codebook that results in minimum power being received at the node. The null subspace for each node is taken into consideration when communicating with a particular node.
1. A method comprising the steps of:
transmitting pilot data to a first and a second node from multiple antennas;
receiving a first and a second channel subspace information from the first and the second nodes in response to the transmission;
determining first and second null subspace information wherein the first null subspace information comprises a matrix that is used to minimize the transmit energy to the first node and the second null subspace information comprises a matrix that is used to minimize the energy to the second node;
utilizing the first channel subspace information and the second null subspace information to determine antenna weights for the first node;
utilizing the second channel subspace information and the first null subspace information to determine antenna weights for the second node; and
transmitting data to the first and the second nodes simultaneously utilizing the first and the second antenna weights, respectively.
2. The method of claim 1 wherein the channel subspace information comprises a codebook entry.
3. The method of claim 1 wherein the null subspace information comprises a codebook entry.
4. The method of claim 1 wherein first channel subspace information comprises a codebook entry that maximizes transmit energy to the first node and the second channel subspace information comprises a codebook entry that maximizes energy to the second node.
5. The method of claim 1 further comprising the step of:
receiving the first and the second channel subspace information from the first and the second nodes in response to the transmission.
6. An apparatus comprising:
a transmitter transmitting pilot data;
a receiver receiving first and second channel subspace information from a first and a second node and first and second null subspace information from the first and the second node, wherein the first null subspace information comprises a matrix that is used to minimize the transmit energy to the first node and the second null subspace information comprises a matrix that is used to minimize the energy to the second node; and
stream weighting circuitry utilizing the first channel subspace information and the second null subspace information to determine first antenna/stream weights for the first node, the stream weighting circuitry additionally utilizing the second channel subspace information and the first null subspace information to determine second antenna/stream weights for the second node.
7. The apparatus of claim 6 wherein the transmitter additionally transmits information to the first and the second nodes simultaneously utilizing the first and the second antenna/stream weights.
8. The apparatus of claim 6 wherein the channel subspace information comprises a first and a second codebook entry.
9. The apparatus of claim 6 wherein the first and the second null subspace information comprises a first and a second codebook entry.
10. The apparatus of claim 6 wherein first channel subspace information comprises a codebook entry that maximizes transmit energy to the first node and the second channel subspace information comprises a codebook entry that maximizes energy to the second node.