Wireless data communication system and wireless data communication method
In MIMO transmission between M transmission antennas and N reception antennas, a transmission signal vector is set as a vector having 2M elements comprising in-phase components and quadrature components of M complex signals, a reception signal vector is set as a vector having 2N elements comprising in-phase components and quadrature components of N complex signals, and a transfer matrix is set as a real matrix comprising 2N rows and 2M columns. Then, a transfer matrix containing IQ mismatch is obtained based on a training signal, thereby executing MIMO encoding and decoding. For learning of the transfer matrix, a training signal which has two linearly-independent signal points on a constellation for each of the transmission antennas is used. With such an arrangement, in MIMO transmission, IQ mismatch in a quadrature modulator and a quadrature demodulator can be compensated and a bit error rate can be improved.
1. A wireless data communication system comprising:
a transmitter having M transmission antennas; and
a receiver having N reception antennas,
wherein data communication is executed between said transmitter and said receiver,
wherein said transmitter includes a modulator that modulates a transmission signal associated with each of the transmission antennas and a demodulator that demodulates a reception signal from each of the reception antennas,
wherein said data communication is executed based on a real number signal which consists of in-phase components and quadrature components of said transmission signal and said reception signal,
wherein training signal vectors consist of at least two signal vectors whose component vectors for each antenna are linearly-independent of each other,
wherein based on a real number transmission signal vector which has 2M components, and a real number reception signal vector which has 2N components, an arithmetic operation is performed on a 2N-row-2M-column transfer matrix which shows a relationship between a transmission signal vector and a reception signal vector which each contain deviation in an in-phase component and deviation in a quadrature component that occur during a modulation process in said modulator and deviation in an in-phase component and deviation in a quadrature component that occur during a demodulation process in said demodulator, and
wherein after said training signal vectors are transmitted, said transfer matrix is estimated by using received training signal vectors, according to data to be transmitted to said receiver from said transmitter, and an arithmetic operation is performed on the real number reception signal vector to be input to said demodulator based on said transfer matrix.
2. The wireless data communication system according to claim 1 ,
wherein respective signal points are extracted from said training signal vectors, and said training signal vectors are configured by binary phase shift keying signals in which phases on constellations on said extracted signal points differ from each other by 90 degrees.
3. The wireless data communication system according to claim 1 ,
wherein said training signal vectors are configured by binary phase shift keying, respectively, and a phase of a signal point on a constellation of each training signal vector is rotated by 90 degrees each time said training signal vector is transmitted.
4. A wireless data communication method for executing data communication between a transmitter having M transmission antennas and a receiver having N reception antennas,
said transmitter being a transmitter that modulates a transmission signal to each of said transmission antennas and transmits data from each of said transmission antennas,
said receiver being a receiver that demodulates the reception signal from each of said reception antennas and extracts data,
said data communication being executed based on real number signal which consists of in-phase components and quadrature components of said transmission signal and said reception signal, and
said wireless data communication method comprising the steps of:
transmitting signal vectors consisting of at least two signal vectors whose component vectors for each antenna are linearly-independent of each other;
based on a real-number transmission signal vector which has 2M components, and a real-number reception signal vector which has 2N components, and an in-phase component and a quadrature component of N reception signal vectors, arithmetically operating a 2N-row-2M-column transfer matrix which shows a relationship between a transmission signal vector and a reception signal vector which each contain deviation in an in-phase component and deviation in a quadrature component that occur during a modulation process in a modulator and deviation in an in-phase component and deviation in a quadrature component that occur during a demodulation process in a demodulator;
after said training signal vectors are transmitted, estimating said transfer matrix by using received training signal vectors;
transmitting data from said transmission antennas to said reception antennas so as to transmit the data from said transmitter to said receiver; and
arithmetically operating the real number reception signal vector to be input to said demodulator through data transmission based on said transfer matrix.
5. The wireless data communication method according to claim 4 ,
wherein respective signal points are extracted from said training signal vectors, and said training signal vectors are configured by binary phase shift keying signals in which phases on constellations on said extracted signal points differ from each other by 90 degrees.
6. The wireless data communication method according to claim 4 ,
wherein said training signal vectors are configured by binary phase shift keying and a phase of a signal point on a constellation of each training signal vector is rotated by 90 degrees each time said training signal vector is transmitted.