Wireless communication system

Abstract

In order to transmit a large amount of data in series at a time with a MIMO communication scheme while avoiding deterioration of decoding characteristics due to change over time by a channel matrix, a wireless communication system uses an open-loop type and a closed-loop type of MIMO communication modes in combination and switches to the open-loop MIMO communication mode in response to the information that the amount of data to be transmitted at a time has exceeded a predetermined amount of bits or a predetermined transmission time during data transmission under the closed-loop MIMO communication mode. By discontinuing useless closed-loop MIMO communication and switching to the open-loop MIMO communication mode that is better than Zero-forcing, the decoding characteristics are prevented from simply becoming deteriorated.

What is claimed is: 
     
       1. A wireless communication system in which a transmitter having a plurality of antennas and a receiver having a plurality of antennas form a pair and spatially multiplex and communicate a signal, the wireless communication system comprising:
 a closed-loop spatial multiplexing communication mode in which the transmitter transmits a signal for acquiring channel information to the receiver and the receiver sends feedback of the channel information to the transmitter;   an open-loop spatial multiplexing communication mode in which only the transmitter transmits a signal for acquiring channel information to the receiver; and   a mode switcher configured to switch between the closed-loop spatial multiplexing communication mode and the open-loop spatial multiplexing communication mode, and switch to the open-loop spatial multiplexing communication mode in response to information indicating that an amount of data to be transmitted has exceeded a predetermined data limit or a transmission time during data transmission under the closed-loop spatial multiplexing communication mode has exceeded a predetermined time limit.   
     
     
       2. The wireless communication system of  claim 1 , wherein
 the mode switcher is further configured to switch to the open-loop spatial multiplexing communication mode in response to the information that an error rate has exceeded a predetermined value during data transmission under the closed-loop spatial multiplexing communication mode.   
     
     
       3. The wireless communication system according to  claim 1 , wherein the transmitter transmits data that the transmitter does not apply a transmission weight to under the open-loop spatial multiplexing communication mode. 
     
     
       4. The wireless communication system of  claim 1 , wherein
 the receiver performs an open-loop spatial multiplexing communication operation other than a communication scheme for providing a reception weight based on an inverse matrix H −  of a channel matrix obtained from a propagation path condition under the open-loop spatial multiplexing communication mode.   
     
     
       5. The wireless communication system according to  claim 1 , wherein
 said mode switcher is further configured to switch between the closed-loop spatial multiplexing communication mode and the open-loop spatial multiplexing communication mode, and inform the receiver that a mode has been switched to the open-loop spatial multiplexing communication mode.   
     
     
       6. A wireless communication system in which a transmitter having a plurality of antennas and a receiver having a plurality of antennas form a pair and spatially multiplex and communicate a signal, the wireless communication system comprising:
 a closed-loop spatial multiplexing communication mode in which the transmitter transmits a signal for acquiring channel information to the receiver, the receiver sends feedback of the channel information to the transmitter, the receiver finds a channel matrix H by receiving a reference signal sent from the transmitter, obtains a reception weight matrix U H , a diagonal matrix D and a transmission weight matrix V by performing singular value decomposition of the channel matrix H into UDV H , and sends feedback of the transmission weight matrix V to the transmitter, there is performed Singular Value Decomposition-Multiple Input Multiple Output (SVD-MIMO) communication in which the transmitter performs weighted transmission with the transmission weight matrix V and the receiver performs weighted reception with the reception weight matrix U H ;   an open-loop spatial multiplexing communication mode in which only the transmitter transmits a signal for acquiring channel information to the receiver; and   a mode switcher configured to switch between the closed-loop spatial multiplexing communication mode and the open-loop spatial multiplexing communication mode, and switch to the open-loop spatial multiplexing communication mode in response to the information that the transmission weight matrix V obtained by the singular value decomposition has changed beyond a predetermined value during data transmission under the closed-loop spatial multiplexing communication mode.   
     
     
       7. A wireless communication apparatus having a plurality of antennas that spatially multiplexes and transmits a signal to a receiver having a plurality of antennas, the wireless communication apparatus comprising:
 a closed-loop spatial multiplexing communication mode in which the apparatus performs weighted transmission based on feedback information from the receiver;   an open-loop spatial multiplexing communication mode in which the apparatus performs non-weighted transmission; and   a mode switcher configured to switch between the closed-loop spatial multiplexing communication mode and the open-loop spatial multiplexing communication mode, and switch to the open-loop spatial multiplexing communication mode in response to information indicating that an amount of data to be transmitted has exceeded a predetermined data limit or a transmission time during data transmission under the closed-loop spatial multiplexing communication mode has exceeded a predetermined time limit.   
     
     
       8. The wireless communication apparatus of  claim 7 , wherein
 said mode switcher is further configured to switch between the closed-loop spatial multiplexing communication mode and the open-loop spatial multiplexing communication mode, and switch to the open-loop spatial multiplexing communication mode in response to information that an error rate has exceeded a predetermined value during data transmission under the closed-loop spatial multiplexing communication mode.   
     
     
       9. A wireless communication apparatus having a plurality of antennas that spatially multiplexes and transmits a signal to a receiver having a plurality of antennas, the wireless communication apparatus comprising:
 a closed-loop spatial multiplexing communication mode in which the apparatus performs weighted transmission based on feedback information from the receiver;   an open-loop spatial multiplexing communication mode in which the apparatus performs non-weighted transmission; and   a mode switcher configured to switch between the closed-loop spatial multiplexing communication mode and the open-loop spatial multiplexing communication mode, and switch to the open-loop spatial multiplexing communication mode in response to the information from the receiver that a mode has been switched to the open-loop spatial multiplexing communication mode.   
     
     
       10. A wireless communication apparatus having a plurality of antennas that spatially multiplexes and transmits a signal to a receiver having a plurality of antennas, the wireless communication apparatus comprising:
 a closed-loop spatial multiplexing communication mode in which the apparatus performs weighted transmission based on feedback information from the receiver;   an open-loop spatial multiplexing communication mode in which the apparatus performs non-weighted transmission;   a mode switcher configured to switch between the closed-loop spatial multiplexing communication mode and the open-loop spatial multiplexing communication mode;   a feedback information receiving section configured to receive feedback information for acquiring a transmission weight matrix V from the receiver and perform Singular Value Decomposition-Multiple Input Multiple Output (SVD-MIMO) transmission of weighted transmission by the transmission weight matrix V under the closed-loop spatial multiplexing communication mode; and   a transmitting section configured to transmit data to which the apparatus does not apply the transmission weight V under the open-loop spatial multiplexing communication mode.   
     
     
       11. A wireless communication apparatus having a plurality of antennas that receives a multiplexed signal from a transmitter having a plurality of antennas, the wireless communication apparatus comprising:
 a closed-loop spatial multiplexing communication mode in which the apparatus sends feedback of channel information to the transmitter, finds a channel matrix H by receiving a reference signal sent from the transmitter, obtains a reception weight matrix U H , a diagonal matrix D and a transmission weight matrix V by performing singular value decomposition of the channel matrix H into UDV H , and performs Singular Value Decomposition-Multiple Input Multiple Output (SVD-MIMO) communication using weighted reception with the reception weight matrix U H  and sends feedback of the transmission weight matrix V to the transmitter;   an open-loop spatial multiplexing communication mode in which the apparatus does not send feedback of channel information to the transmitter; and   a mode switcher configured to switch between the closed-loop spatial multiplexing communication mode and the open-loop spatial multiplexing communication mode, and switch to the open-loop spatial multiplexing communication mode in response to the information that the transmission weight matrix V obtained by the singular value decomposition has changed beyond a predetermined value during data transmission under the closed-loop spatial multiplexing communication mode.   
     
     
       12. A wireless communication apparatus having a plurality of antennas that receives a multiplexed signal from a transmitter having a plurality of antennas, the wireless communication apparatus comprising:
 a closed-loop spatial multiplexing communication mode in which the apparatus sends feedback of channel information to the transmitter;   an open-loop spatial multiplexing communication mode in which the apparatus does not send feedback of channel information to the transmitter; and   a mode switcher configured to switch between the closed-loop spatial multiplexing communication mode and the open-loop spatial multiplexing communication mode, and inform the transmitter that a mode has been switched to the open-loop spatial multiplexing communication mode.   
     
     
       13. The wireless communication apparatus of  claim 12 , wherein the
 mode switcher is further configured to switch to the open-loop spatial multiplexing communication mode in response to the information from the transmitter that a mode has been switched to the open-loop spatial multiplexing communication mode.   
     
     
       14. A wireless communication apparatus having a plurality of antennas that receives a multiplexed signal from a transmitter having a plurality of antennas, the wireless communication apparatus comprising:
 a closed-loop spatial multiplexing communication mode in which the apparatus sends feedback of channel information to the transmitter;   an open-loop spatial multiplexing communication mode in which the apparatus does not send feedback of channel information to the transmitter;   a mode switcher configured to switch between the closed-loop spatial multiplexing communication mode and the open-loop spatial multiplexing communication mode; and   a communication section configured to perform an open-loop spatial multiplexing communication operation other than a communication scheme for providing a reception weight based on an inverse matrix I-V of a channel matrix obtained from a propagation path condition under the open-loop spatial multiplexing communication mode.   
     
     
       15. A wireless communication method for spatially multiplexing and transmitting a signal to a receiver having a plurality of antennas in a transmitter having a plurality of antennas, the wireless communication method comprising:
 performing closed-loop spatial multiplexing communication based on feedback information from the receiver, the closed-loop spatial multiplexing communication allowing the transmitter to perform weighted transmission;   switching to open-loop spatial multiplexing communication in response to information indicating that an amount of data to be transmitted has exceeded a predetermined data limit or a transmission time during data transmission under the closed-loop spatial multiplexing communication mode has exceeded a predetermined time limit; and performing the open-loop spatial multiplexing communication.   
     
     
       16. A wireless communication method for receiving a multiplexed signal from a transmitter having a plurality of antennas in a receiver having a plurality of antennas, the wireless communication method comprising the steps of:
 performing closed-loop spatial multiplexing communication on the assumption that a transmission weight has been applied by the transmitter, the closed-loop spatial multiplexing communication allowing the receiver to perform weighted reception;   switching to open-loop spatial multiplexing communication in response to a change in a reception characteristic, the open-loop spatial multiplexing communication allowing the receiver to perform weighted reception;   performing the open-loop spatial multiplexing communication on the assumption that a transmission weight has been applied by the transmitter.   
     
     
       17. A computer-readable medium storing a computer program which when executed on a computer causes the computer to perform processing for spatially multiplexing and transmitting a signal to a receiver having a plurality of antennas from a transmitter having a plurality of antennas, comprising:
 performing closed-loop spatial multiplexing communication based on feedback information from the receiver, the closed-loop spatial multiplexing communication allowing the transmitter to perform weighted transmission;   switching to open-loop spatial multiplexing communication in response to information indicating that an amount of data to be transmitted has exceeded a predetermined data limit or a transmission time during data transmission under the closed-loop spatial multiplexing communication mode has exceeded a predetermined time limit; and   performing the open-loop spatial multiplexing communication.   
     
     
       18. A computer-readable medium storing a computer program which when executed on a computer causes the computer to perform processing for spatially multiplexing and transmitting a signal to a receiver having a plurality of antennas, in a transmitter having a plurality of antennas, comprising:
 performing closed-loop spatial multiplexing communication by performing weighted transmission based on feedback information from the receiver;   performing open-loop spatial multiplexing communication in which the transmitter performs non-weighted transmission;   switching between the closed-loop spatial multiplexing communication and the open-loop spatial multiplexing communication, and switching to the open-loop spatial multiplexing communication in response to information from the receiver that a mode has been switched to the open-loop spatial multiplexing communication mode.   
     
     
       19. An information processing apparatus comprising:
 processing circuitry configured to:   receive feedback information from a receiver in a closed loop spatial multiplexing communication mode;   send a signal in the closed loop spatial multiplexing communication mode or a different spatial coding communication mode in which control information is used; and   switch to the different spatial coding communication mode according to a failure of communication.   
     
     
       20. An information processing apparatus comprising:
 processing circuitry configured to:   transmit feedback information in a closed loop spatial multiplexing communication mode;   receive a signal in the closed loop spatial multiplexing communication mode or a different spatial coding communication mode in which control information is used;   switch to the different spatial communication mode according to a failure of communication.   
     
     
       21. A wireless communication apparatus having one or more antennas comprising:
 processing circuitry configured to:   send training signals to a receiver;   receive feedback information from the receiver in a closed loop spatial multiplexing communication mode;   calculate transmit weights in consideration of the feedback information;   transmit a signal in the closed loop spatial multiplexing communication mode using the transmit weights or a different spatial coding communication mode in which control information is used; and   switch to the different spatial coding communication mode according to a change in a communication quality.   
     
     
       22. A wireless communication apparatus of claim 21, wherein the processing circuitry is further configured to:
 estimate channel state information based on training signals transmitted from receiver.   
     
     
       23. A wireless communication apparatus comprising:
 a plurality of antennas;   processing circuitry configured to:   estimate a channel state information based on training signals transmitted from a transmitter;   transmit feedback information in a closed loop spatial multiplexing communication mode;   receive a signal in the closed loop spatial multiplexing communication mode and a different spatial coding communication mode in which control information is used; and   switch to the different spatial communication mode according to a failure of communication.   
     
     
       24. A wireless communication apparatus of claim 23, wherein the processing circuitry is further configured to:
 send training signals to the transmitter.   
     
     
       25. A wireless communication apparatus comprising:
 a plurality of antennas configured to transmit and receive signals from another wireless communication apparatus having a plurality of antennas;   a feedback information calculating unit configured to calculate feedback information to transmit in a closed loop spatial multiplexing communication mode;   a control unit configured to determine which receiving scheme to use, for the closed loop spatial multiplexing communication mode or for a different spatial coding communication mode in which control information is used, in response to a detection of a change in a reception characteristic;   a receive weight calculating unit configured to calculate receive weights based on the determined receiving scheme.   
     
     
       26. A wireless communication apparatus of claim 25,
 wherein the receive weight calculating unit calculate receive weights according to at least one of MMSE, BLAST, MMSE+BLAST, maximum likelihood estimation criteria when the determined receiving scheme is for the different spatial coding communication mode.   
     
     
       27. A wireless communication apparatus comprising:
 a plurality of antennas configured to transmit and receive signals from another wireless communication apparatus having one or more antennas;   a feedback information calculating unit configured to calculate feedback information to transmit in a closed loop spatial multiplexing communication mode; and   a control unit configured to determine which receiving scheme to use, for the closed loop spatial multiplexing communication mode or for a different spatial coding communication mode in which control information is used, in response to a detection of a change in a reception characteristic;   a receive signal processing unit configured to decode receive signals in a processing scheme corresponding to the determined receiving scheme.   
     
     
       28. A wireless communication apparatus having one or more antennas comprising:
 a transmitting unit configured to transmit feedback information in a closed loop spatial multiplexing communication mode;   a receiving unit configured to receive a signal in the closed loop spatial multiplexing communication mode and a different spatial coding communication mode in which control information is used;   a controller configured to switch to the different spatial communication mode according to a change in a communication quality.   
     
     
       29. A wireless communication apparatus having one or more antennas comprising:
 a receiving unit configured to receive feedback information from a receiver in a closed loop spatial multiplexing communication mode;   a transmitting unit configured to transmit a signal in the closed loop spatial multiplexing communication mode and a different spatial coding communication mode in which control information is used; and   a controller configured to switch to the different spatial coding communication mode according to a failure of communication.   
     
     
       30. A wireless communication apparatus of claim 29, wherein the feedback information indicates transmission weight information. 
     
     
       31. A wireless communication apparatus of claim 29, wherein the different spatial coding communication is spatial multiplexing communication. 
     
     
       32. A wireless communication apparatus of claim 29, wherein the different spatial coding communication is open-loop spatial multiplexing communication. 
     
     
       33. A wireless communication apparatus of claim 29, further comprising a plurality of antennas by which the transmit unit transmitting a signal in the closed loop spatial multiplexing communication mode and the different spatial coding communication mode. 
     
     
       34. A wireless communication apparatus of claim 33, wherein the different spatial coding communication is open-loop spatial multiplexing communication. 
     
     
       35. A wireless communication apparatus of claim 29, wherein the receiving unit receives information from a mobile station which reception characteristic is changed. 
     
     
       36. A wireless communication apparatus of claim 29, further comprising a circuit commonly used in both the closed loop spatial multiplexing communication mode and the different spatial coding communication mode. 
     
     
       37. A wireless communication apparatus of claim 29, wherein switch to the different spatial coding communication mode when a communication quality becomes worse. 
     
     
       38. A wireless communication apparatus of claim 29, wherein switch to the different spatial coding communication mode in response to information indicating that an amount of data to be transmitted has exceeded a predetermined data limit,
 a transmission time during data transmission under the closed-loop spatial multiplexing communication mode has exceeded a predetermined time limit,   or an error rate has exceeded a predetermined value during data transmission under the closed-loop spatial multiplexing communication mode.   
     
     
       39. A wireless communication apparatus having one or more antennas comprising:
 a transmitting unit configured to transmit feedback information in a closed loop spatial multiplexing communication mode;   a receiving unit configured to receive a signal in the closed loop spatial multiplexing communication mode and a different spatial coding communication mode in which control information is used;   a controller configured to switch to the different spatial communication mode according to a failure of communication.   
     
     
       40. A wireless communication apparatus of claim 39, wherein the feedback information indicates transmission weight information. 
     
     
       41. A wireless communication apparatus of claim 39, wherein the different spatial coding communication is spatial multiplexing communication. 
     
     
       42. A wireless communication apparatus of claim 39, wherein the different spatial coding communication is open-loop spatial multiplexing communication. 
     
     
       43. A wireless communication apparatus of claim 39, further comprising a plurality of antennas by which the transmit unit transmitting a signal in the closed loop spatial multiplexing communication mode and the different spatial coding communication mode. 
     
     
       44. A wireless communication apparatus of claim 39, wherein the wireless communication apparatus is a mobile station. 
     
     
       45. A wireless communication apparatus of claim 39, wherein the transmitting unit transmits information according to a change of reception characteristic. 
     
     
       46. A wireless communication apparatus of claim 39, further comprising a circuit commonly used in both the closed loop spatial multiplexing communication mode and the different spatial coding communication mode. 
     
     
       47. A wireless communication apparatus of claim 46, wherein the circuit is an OFDM decoder. 
     
     
       48. A wireless communication apparatus of claim 39, wherein switch to the different spatial coding communication mode when the reception characteristic becomes worse. 
     
     
       49. A wireless communication apparatus of claim 39, wherein switch to the different spatial coding communication mode in response to information indicating that an amount of data to be transmitted has exceeded a predetermined data limit,
 a transmission time during data transmission under the closed-loop spatial multiplexing communication mode has exceeded a predetermined time limit,   or an error rate has exceeded a predetermined value during data transmission under the closed-loop spatial multiplexing communication mode.   
     
     
       50. A wireless communication apparatus of claim 39, further comprising a unit executes a singular value decomposition (SVD). 
     
     
       51. An information processing apparatus comprising:
 processing circuitry configured to:   transmit a signal to a receiver in at least one of a closed-loop spatial multiplexing communication mode using feedback information or a spatial coding communication mode, wherein there is more feedback information in the closed-loop spatial multiplexing communication mode than in the spatial coding communication mode; and   switch to the spatial coding communication mode from the closed-loop multiplexing communication mode in response to deterioration of reception characteristics.   
     
     
       52. An information processing apparatus comprising:
 processing circuitry configured to:   transmit a signal to a receiver in at least one of a first spatial multiplexing communication mode or a second spatial multiplexing communication mode,   wherein the first spatial multiplexing communication mode uses feedback information, and there is more feedback information in the first spatial multiplexing communication mode than in the second spatial multiplexing communication mode; and   switch to the second spatial multiplexing communication mode form the first spatial multiplexing communication mode in response to deterioration of reception characteristics.   
     
     
       53. An information processing apparatus comprising:
 processing circuitry configured to:   receive a signal from a transmitter in at least one of a first spatial multiplexing communication mode or a second spatial multiplexing communication mode,   wherein the first spatial multiplexing communication mode uses feedback information, and there is more feedback information in the first spatial multiplexing communication mode than in the second spatial multiplexing communication mode; and   switch to the second spatial multiplexing communication mode form the first spatial multiplexing communication mode in response to deterioration of reception characteristics.   
     
     
       54. An information processing apparatus comprising:
 processing circuitry configured to:   receive a signal from a transmitter in at least one of a first spatial multiplexing communication mode or a second spatial multiplexing communication mode,   wherein the first spatial multiplexing communication mode uses feedback information, and there is more feedback information in the first spatial multiplexing communication mode than in the second spatial multiplexing communication mode; and   set the information processing apparatus to the second spatial multiplexing communication mode in response to a notification from the transmitter indicating that the transmitter is in the second spatial multiplexing communication mode.