Wireless communication apparatus and wireless communication method

1. A wireless communication apparatus which receives, by multiple antennas, receive signals created by spatially multiplexing multiple transmit streams subjected to power allocation, the wireless communication apparatus comprising:

a channel matrix estimator which estimates a channel matrix of spatially multiplexed channels based on the received signals;

a receive buffer which temporarily stores the receive signals;

a spatial demultiplexer which obtains an antenna receive weight matrix from the estimated channel matrix and demultiplexes the receive signals temporarily stored in the receive buffer into multiple receive streams by multiplying the receive signals by the antenna receive weight matrix;

wherein the receive signals that have been demultiplexed using the channel matrix are stored in the receive buffer; and

a power estimator which estimates power allocation information as to each stream;

wherein the channel matrix estimator re-estimates the channel matrix based on the power allocation information; and

wherein the spatial demultiplexer re-demultiplexes the demultiplexed receive signals in the receive buffer according to the re-estimated channel matrix.

2. The wireless communication apparatus according to claim 1 , wherein the spatial demultiplexer calculates an antenna receive weight matrix in accordance with an MMSE (Minimum Mean Square Error) algorithm based on a logic of maximizing the ratio of signal power to square error and multiplies the receive signals by the antenna receive weight matrix.

3. The wireless communication apparatus according to claim 1 , wherein the power estimator acquires power allocation information from each receive stream into which the spatial demultiplexer has spatially demultiplexed and feeds back the power allocation information to the channel matrix estimator.

4. The wireless communication apparatus according to claim 3 , wherein the re-estimated channel matrix provides an antenna receive weight matrix for the spatial demultiplexer to re-demultiplex the receive signals.

5. The wireless communication apparatus according to claim 1 , wherein

a spatial multiplexing signal includes a known signal series;

the channel matrix estimator estimates the channel matrix based on a known signal series; and

the power estimator calculates power allocation to each stream based on the known signal series extracted from each stream after spatial demultiplexing.

6. The wireless communication apparatus according to claim 5 , wherein

in spatial multiplexing communication, there is adopted an OFDM transmission scheme for performing OFDM mapping on multiple subcarriers orthogonal to each other on a frequency axis, and

the power estimator calculates power allocation to each stream based on reception power of a pilot carrier included in user data of each stream after spatial demultiplexing.

7. The wireless communication apparatus according to claim 5 , wherein the known signal series complies with one of IEEE802.11a, IEEE802.11g, and HiperLAN/type2.

8. A wireless communication method comprising:

receiving, by multiple antennas, receive signals created by spatially multiplexing multiple transmit streams subjected to power allocation;

estimating a channel matrix of spatially multiplexed channels based on the receive signals;

obtaining an antenna receive weight matrix from the estimated channel matrix;

temporarily storing the receive signals of the antennas in a receive buffer;

demultiplexing the receive signals temporarily stored in the receive buffer into multiple receive streams by multiplying the receive signals by the antenna receive weight matrix;

storing the receive signals that have been demultiplexed in the receive buffer;

estimating power allocation information as to each stream;

re-estimating the channel matrix based on the power allocation information; and

re-demultiplexing the demultiplexed receive signals stored in the receive buffer according to the re-estimated channel matrix.

9. The wireless communication method according to claim 8 , further comprising:

calculating an antenna receive weight matrix in accordance with an MMSE (Minimum Mean Square Error) algorithm based on a logic of maximizing the ratio of signal power to square error; and

multiplying the receive signals by the antenna receive weight matrix.

10. The wireless communication method according to claim 8 , further comprising:

acquiring power allocation information from each receive stream that has been demultiplexed; and

feeding back the power allocation information for re-estimating the channel matrix.

11. The wireless communication method according to claim 10 , wherein re-demultiplexing the receive signal further comprises:

obtaining an antenna receive weight matrix from the re-estimated channel matrix for re-demultiplexing the receive signal.

12. The wireless communication method according to claim 8 , wherein

a spatial multiplexing signal includes a known signal series;

the estimating the channel matrix further comprises estimating the channel matrix based on the known signal series; and

the estimating power allocation information further comprises calculating power allocation to each stream based on the known signal series extracted from each stream after demultiplexing.

13. The wireless communication method according to claim 12 , wherein

in spatial multiplexing communication, there is adopted an OFDM transmission scheme for performing OFDM mapping on multiple subcarriers orthogonal to each other on a frequency axis, and

the estimating power allocation information further comprises calculating power allocation to each stream based on reception power of a pilot carrier included in user data of each stream after demultiplexing.

14. The wireless communication method according to claim 12 , wherein the known signal series complies with one of IEEE802.11a, IEEE802.11g, and HiperLAN/type2.