Wireless data communication system and wireless data communication method

• US 20060198461A1
• Filed: 08/26/2005
• Published: 09/07/2006
• Est. Priority Date: 03/02/2005
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Hayase, Shigenori
• Granted Patent: US 8,345,785 B2
• Time in Patent Office: Days
• US Class Current: 375/267
• CPC Class Codes: H04B 7/0413 MIMO systems
• CPC Class Codes: H04B 7/0619 using feedback from receiving side feedback signaling for adaptive modulation/coding H04L1/0001
• CPC Class Codes: H04B 7/0678 using different spreading codes between antennas code allocation H04J13/16
• CPC Class Codes: H04L 25/0226 sounding signals per se
• CPC Class Codes: H04L 27/364 Arrangements for overcoming imperfections in the modulator, e.g. quadrature error or unbalanced I and Q levels
• CPC Class Codes: H04L 27/3863 Compensation for quadrature error in the received signal

Abstract

In MIMO transmission which executes quadrature modulation of M transmission antennas and N reception antennas, a transmission signal vector will be set as a vector having the element number of 2M that comprises the in-phase components and quadrature components of M complex signals, a reception signal vector will be set as a vector having the element number of 2N that comprises the in-phase components and quadrature components of N complex signals, and a transfer matrix will be 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 arrangement, it is possible, in MIMO wireless data transmission, to compensate deterioration in a bit error rate that is caused by IQ mismatch in a quadrature modulator and a quadrature demodulator.

Claims

1. A wireless data communication system which executes data communication between a transmitter having M transmission antennas and a receiver having N reception antennas, wherein:

said transmitter includes a modulator that modulates a transmission signal associated with each of the transmission antennas and a demodulator that modulates a reception signal from each of the reception antennas;

a training signal is transmitted to said receiver from said transmitter;

based on an in-phase component and a quadrature component of M transmission signal vectors, and an in-phase component and a quadrature component of N transmission signal vectors, 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 occurs during a demodulation process in said demodulator; and

after said training signal is transmitted, according to data to be transmitted to said receiver from said transmitter, an arithmetic operation is performed on the in-phase component and the quadrature component to be input to said demodulator based on said transfer matrix.

2. The wireless data communication system according to claim 1,

wherein, to determine said transfer matrix, a training signal having at least two linearly-independent signal points on a constellation for a transmission antenna is used.

3. The wireless data communication system according to claim 1,

wherein said training signal is configured by quadrature phase shift keying.

4. The wireless data communication system according to claim 2,

wherein respective signal points are extracted from a first training signal and a second training signal, and said training signals 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.

5. The wireless data communication system according to claim 2,

wherein said training signal is configured by binary phase shift keying and a phase of a signal point on constellation of said training signal is rotated by 90 degrees each time said training signal is transmitted.

6. 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 said transmission antenna,

said receiver being a receiver that demodulates the reception signal from each of said reception antennas and extracts data, and

said wireless data communication method comprising the steps of:

transmitting a training signal to said receiver from said transmitter;

based on an in-phase component and a quadrature component of M transmission signal vectors, 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 is transmitted, transmitting data from said transmission antenna to said reception antenna so as to transmit the data from said transmitter to said receiver; and

arithmetically operating the in-phase component and the quadrature component to be input to said demodulator through data transmitted, based on said transfer matrix.

7. The wireless data communication method according to claim 6,

wherein said training signal is configured by quadrature phase shift keying.

8. The wireless data communication method according to claim 6,

wherein respective signal points are extracted from a first training signal and a second training signal, and said training signals 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.

9. The wireless data communication method according to claim 6,

wherein said training signal is configured by binary phase shift keying and a phase of a signal point on constellation of said training signal is rotated by 90 degrees each time said training signal is transmitted.