Wireless communication system

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 UH, a diagonal matrix D and a transmission weight matrix V by performing singular value decomposition of the channel matrix H into UDVH, 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 UH;
• 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.

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.

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.

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.

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 UH, a diagonal matrix D and a transmission weight matrix V by performing singular value decomposition of the channel matrix H into UDVH, and performs Singular Value Decomposition-Multiple Input Multiple Output (SVD-MIMO) communication using weighted reception with the reception weight matrix UH 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.

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.

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.

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.

A non-transitory 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.