WIRELESS COMMUNICATION SYSTEM, WIRELESS COMMUNICATION DEVICE AND WIRELESS COMMUNICATION METHOD, AND COMPUTER PROGRAM

• US 20100091675A1
• Filed: 09/15/2009
• Published: 04/15/2010
• Est. Priority Date: 10/10/2008
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: SAWAI, Ryo
• Granted Patent: US 8,289,869 B2
• Time in Patent Office: Days
• US Class Current: 370/252
• CPC Class Codes: H04B 7/063 Parameters other than those covered in groups H04B7/0623 - H04B7/0634, e.g. channel matrix rank or transmit mode selection
• CPC Class Codes: H04B 7/086 using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming
• CPC Class Codes: H04L 1/0023 characterised by the signalling
• CPC Class Codes: H04L 1/06 using space diversity
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 25/03019 adaptive, i.e. capable of adjustment during data reception
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end
• CPC Class Codes: H04L 27/2601 Multicarrier modulation systems

Abstract

A wireless communication system which includes a transmitter and receiver each having two or more antennae, the system including: a channel condition determining unit which determines a condition of a channel between the transmitter and the receiver; and a system control unit which changes a transmitting system in the transmitter and a receiving system in the receiver in accordance with a determination result obtained by the channel condition determining unit.

Claims

1. A wireless communication system which includes a transmitter and a receiver each having two or more antennae, the system comprising:

a channel condition determining unit which determines a condition of a channel between the transmitter and the receiver; and

a system control unit which changes a transmitting system in the transmitter and a receiving system in the receiver in accordance with a determination result obtained by the channel condition determining unit.

2. The wireless communication system according to claim 1, wherein:

the channel condition determining unit calculates one of a determinant of a channel matrix and a rank of an eigenvalue estimated between the transmitter and the receiver to determine the number of streams that can be used for communication and a modulating system that can be used for communication;

the system control unit adopts a transmitting system based on a linear area equalization algorithm in the transmitter and a receiving system based on a linear area equalization algorithm when communication is established with the number of streams or modulating system within the determination result obtained by the channel condition determining unit and cancels adaptation of the transmitting system based on a linear area equalization algorithm in the transmitter and adopts a receiving system based on a non-linear area equalization algorithm when communication is established with the number of streams or modulating system outside of the determination result of the channel condition determining unit.

3. The wireless communication system according to claim 2 wherein:

the channel condition determining unit determines a rank number and SNR of the channel matrix between the transmitter and the receiver;

the system control unit adopts a transmitting system based on a linear area equalization algorithm in the transmitter and a receiving system based on a linear area equalization algorithm in the receiver when the rank number of the channel matrix is high enough to allow two or more streams to pass through; and

cancels adaptation of the transmitting system based on a linear area equalization algorithm in the transmitter and adopts a receiving system based on a non-linear area equalization algorithm when the rank number of the channel matrix is lowered to an extent that two or more streams do not pass through but SNR of the two or more streams is high.

4. The wireless communication system according to claim 2, wherein, when M streams are to be transmitted with respect to M transmitting antennae, the system control unit cancels adaptation of the transmitting system based on a linear area equalization algorithm in the transmitter and adopts a receiving system based on a non-linear area equalization algorithm.

5. The wireless communication system according to claim 2 wherein, if a receiving system according to a non-linear area waveform equalization algorithm is adopted, the receiver returns a response packet with NonValid Sounding in response to a request to transmit a Sounding packet including a training sequence in order to excite the channel matrix from the transmitter.

6. The wireless communication system according to claim 2, wherein the receiver returns a response packet with NonValid Sounding when a link adaptation request is received from an M-antenna transmitter in which the number of the streams is specified.

7. The wireless communication system according to claim 2, wherein the channel condition determining unit determines whether or not the transmitter should adopt a transmitting system based on a linear area equalization algorithm according to an eigenvalue provided by a linear evaluation function according to an SNR of a channel between the transmitter and the receiver and an eigenvalue of the channel matrix, evaluation on the SNR alone, and an evaluation function for determining whether or not the condition of the channel is unsuitable for the non-linear area equalization algorithm.

8. The wireless communication system according to claim 7, wherein:

the channel condition unsuitable for the non-linear area equalization algorithm is one in which the channel matrix H is a unitary matrix that obtains an inappropriate power gain between the receiving antennae; and

the system control unit applies a receiving system based on a linear area equalization algorithm in the receiver in accordance with the determination result.

9. The wireless communication system according to claim 8, wherein the channel condition determining unit estimates an eigenvalue on the basis of a channel matrix H of a beam-formed packet from the total electric power of the channel from the transmitting antenna, normalizes the channel matrix H with the estimated eigenvalue, calculates whether the elements of each antenna of the normalized channel matrix H'"'"' are orthogonal to one another and determines that the channel matrix H is a unitary matrix if the calculation result is smaller than a predetermined threshold.

10. The wireless communication system according to claim 2, wherein the channel condition determining unit has several constellation patterns for examination, calculates a metric distance in accordance with acquisition of the channel matrix H and, if the metric distance is smaller than a predetermined threshold, determines that the transmitter should not perform beam-forming.

11. The wireless communication system according to claim 2, wherein the channel condition determining unit has several constellation patterns for examination, calculates a metric distance to a receiving system based on a non-linear area equalization algorithm in accordance with acquisition of the channel matrix H and, if the metric distance is smaller than a predetermined threshold, determines that the transmitter should not perform beam-forming.

12. The wireless communication system according to claim 2, wherein, if it is determined that the receiver is currently receiving a beam-forming transmission signal, then the receiver adopts a receiving system based on a linear area equalization algorithm.

13. The wireless communication system according to claim 12, wherein the receiver determines that the receiver is currently receiving a beam-forming transmission signal when the channel matrix H is a unitary matrix which obtains an inappropriate power gain between the receiving antennae.

14. The wireless communication system according to claim 13, wherein the receiver estimates an eigenvalue on the basis of a channel matrix H of a beam-formed packet from the total electric power of the channel from the transmitting antenna, normalizes the channel matrix H with the estimated eigenvalue, calculates whether the elements of each antenna of the normalized channel matrix H′

are orthogonal to one another and determines that the channel matrix H is a unitary matrix if the calculation result is smaller than a predetermined threshold.

15. A wireless communication device comprising:

two or more antennae;

a channel condition determining unit which determines a condition of a channel with a communication partner;

a communication unit which transmits and receives a packet; and

a system control unit which switches transmitting and receiving systems in the communication unit in accordance with a determination result obtained by the channel condition determining unit.

16. The wireless communication device according to claim 15, wherein:

the channel condition determining unit calculates one of a determinant of a channel matrix and a rank of an eigenvalue estimated between the wireless communication device and the communication partner to determine a number of streams that can be used for communication and a modulating system that can be used for communication; and

the system control unit adopts a transmitting system or a receiving system based on a linear area equalization algorithm and a receiving system based on a linear area equalization algorithm when communication is established with the number of streams or modulating system within the determination result of the channel condition determining unit, and cancels adaptation of the transmitting system based on a linear area equalization algorithm and adopts a receiving system based on a non-linear area equalization algorithm when communication is established with the number of streams or modulating system outside of the determination result of the channel condition determining unit.

17. The wireless communication device according to claim 16, wherein:

the channel condition determining unit determines a rank number and SNR of the channel matrix between the wireless communication device and the communication partner; and

the system control unit adopts one of a transmitting system and a receiving system based on a linear area equalization algorithm and a receiving system based on a linear area equalization algorithm when the rank number of the channel matrix is high enough to allow two or more streams to pass through and cancels adaptation of the transmitting system based on a linear area equalization algorithm and adopts a receiving system based on a non-linear area equalization algorithm when the rank number of the channel matrix is lowered to an extent that two or more streams do not pass through but SNR of the two or more streams is high.

18. The wireless communication device according to claim 16, further comprising M transmitting antennae;

wherein the system control unit cancels adaptation of the transmitting system based on a linear area equalization algorithm when M streams are to be transmitted.

19. The wireless communication device according to claim 16, wherein the system control unit adopts a receiving system based on a non-linear area equalization algorithm when a packet transmitted from M-antenna communication partner through M streams is to be received.

20. The wireless communication device according to claim 16, wherein the channel condition determining unit determines whether or not the communication partner should adopt a transmitting system based on a linear area equalization algorithm according to an eigenvalue of provided by a linear evaluation function according to an SNR of a channel between the wireless communication device and the communication partner and an eigenvalue of the channel matrix, evaluation on the SNR alone, and an evaluation function for examining whether or not the condition of the channel is unsuitable for the non-linear area equalization algorithm.

21. The wireless communication device according to claim 20, wherein the condition of the channel is determined to be unsuitable for the non-linear area equalization algorithm if the channel matrix H is a unitary matrix that obtains an inappropriate power gain between the receiving antennae;

and the system control unit applies a receiving system based on a linear area equalization algorithm in accordance with the determination result.

22. The wireless communication device according to claim 21, wherein the channel condition determining unit estimates an eigenvalue on the basis of a channel matrix H of a beam-formed packet from the total electric power of the channel from the transmitting antenna, normalizes the channel matrix H with the estimated eigenvalue, calculates whether the elements of each antenna of the normalized channel matrix H′

are orthogonal to one another and determines that the channel matrix H is a unitary matrix if the calculation result is smaller than a predetermined threshold.

23. The wireless communication device according to claim 16, wherein the channel condition determining unit has several constellation patterns for examination, calculates a metric distance in accordance with acquisition of the channel matrix H and, if the metric distance is smaller than a predetermined threshold, determines that the communication partner should not perform beam-forming.

24. The wireless communication device according to claim 16, wherein the channel condition determining unit has several constellation patterns for examination, calculates a metric distance to a receiving system based on a non-linear area equalization algorithm in accordance with acquisition of the channel matrix H and, if the metric distance is smaller than a predetermined threshold, determines that the communication partner should not perform beam-forming.

25. The wireless communication device according to claim 16, wherein the system control unit applies a receiving system based on a linear area equalization algorithm if it is determined that the channel condition determining unit is receiving a beam-forming transmission signal.

26. The wireless communication device according to claim 25, wherein it can be determined that a beam-forming transmission signal is received when the channel matrix H is a unitary matrix which obtains inappropriate power gain between the receiving antennae.

27. The wireless communication device according to claim 26, wherein the channel condition determining unit estimates an eigenvalue on the basis of a channel matrix H of a beam-formed packet from the total electric power of the channel from the transmitting antenna, normalizes the channel matrix H with the estimated eigenvalue, calculates whether the elements of each antenna of the normalized channel matrix H′

are orthogonal to one another and determines that the channel matrix H is a unitary matrix if the calculation result is smaller than a predetermined threshold.

28. A wireless communication method using two or more antennae, the method comprising the steps of:

determining a condition of a channel with a communication partner;

performing a communication by transmitting and receiving a packet; and

performing system control by switching transmitting and receiving systems in accordance with a determination result obtained by a channel condition determining unit.

29. A computer program described in a computer-readable format for performing a wireless communication process using two or more antennae on a computer, the computer program allowing the computer to function as:

a channel condition determining unit which determines a condition of a channel with a communication partner;

a communication unit which transmits and receives a packet; and

a system control unit which switches between transmitting and receiving systems in the communication unit in accordance with a determination result obtained by the channel condition determining unit.