Wireless communication system and wireless communication method

Abstract

A base station includes: a MIMO preceding section ( 32 ) for converting transmission data addressed to a mobile station to two data streams that respectively correspond to two reception antennas included in the mobile station, by performing MIMO precoding on the transmission data; a weight calculating section for calculating a transmission weight to be used for forming a directivity pattern directed toward each of the two reception antennas; and a weighting/combining section ( 34 ) for generating two combined data streams that are to be supplied to the respective antennas ( 20 - 1 and 20 - 2 ), by weighting each of the two data streams with the transmission weight calculated with respect to the reception antenna of the mobile station that corresponds to the data stream, and combining the two weighted data streams for each of the antennas ( 20 ). The two combined data streams are respectively transmitted from the antennas ( 20 - 1 and 20 - 2 ).

1 . A wireless communication system, comprising:
 a transmission device comprising a plurality of transmission antennas; and   a MIMO reception device comprising a plurality of reception antennas, wherein   the transmission device comprising:
 MIMO precoding means for converting transmission data addressed to the MIMO reception device to a plurality of data streams that respectively correspond to the plurality of reception antennas, by performing predetermined MIMO precoding on the transmission data; 
 weight calculating means for calculating a transmission weight with respect to each of the plurality of reception antennas so that the plurality of transmission antennas form a directivity pattern directed toward the each of the plurality of reception antennas; 
 weighting/combining means for generating a plurality of combined data streams that are to be supplied respectively to the plurality of transmission antennas, by weighting each of the plurality of data streams with the transmission weight calculated with respect to the reception antenna that corresponds to the each of the plurality of data streams, and combining the plurality of weighted data streams for each of the plurality of transmission antennas; and 
 means for respectively transmitting the plurality of combined data streams from the plurality of transmission antennas, and 
   the MIMO reception device comprising:
 means for receiving, by the plurality of reception antennas, the plurality of combined data streams respectively transmitted from the plurality of transmission antennas; and 
 MIMO decoding means for acquiring the transmission data by performing MIMO decoding that corresponds to the predetermined MIMO precoding on the plurality of combined data streams received by the plurality of reception antennas. 
   
     
     
         2 . The wireless communication system according to  claim 1 , wherein
 the MIMO reception device further comprises means for respectively transmitting a plurality of known reference symbols having a low correlation thereamong from the plurality of reception antennas at the same frequency and at the same timing,   the transmission device further comprises means for receiving, by the plurality of transmission antennas, the plurality of known reference symbols respectively transmitted from the plurality of reception antennas, and   the weight calculating means calculates, based on the plurality of known reference symbols received by the plurality of transmission antennas, the transmission weight for forming the directivity pattern in which, with respect to the each of the plurality of reception antennas, a main beam is directed toward the each of the plurality of reception antennas and a null is directed toward the reception antenna other than the each of the plurality of reception antennas.   
     
     
         3 . The wireless communication system according to  claim 1 , wherein
 the plurality of data streams each contain a known control symbol,   the MIMO reception device further comprises propagation path characteristic estimating means for estimating a characteristic of a radio propagation path that exists between the transmission device and the MIMO reception device based on the plurality of combined data streams received by the plurality of reception antennas and the known control symbols, and   the MIMO decoding means performs the MIMO decoding based on the characteristic of the radio propagation path, which is estimated by the propagation path characteristic estimating means.   
     
     
         4 . The wireless communication system according to  claim 1 , wherein the predetermined MIMO precoding comprises MIMO precoding of a space-time block coding (STBC) scheme or a spatial multiplexing (SM) scheme. 
     
     
         5 . A transmission device including a plurality of transmission antennas, comprising:
 MIMO precoding means for converting transmission data addressed to a MIMO reception device to a plurality of data streams that respectively correspond to a plurality of reception antennas included in the MIMO reception device, by performing predetermined MIMO precoding on the transmission data;   weight calculating means for calculating a transmission weight with respect to each of the plurality of reception antennas so that the plurality of transmission antennas form a directivity pattern directed toward the each of the plurality of reception antennas;   weighting/combining means for generating a plurality of combined data streams that are to be supplied respectively to the plurality of transmission antennas, by weighting each of the plurality of data streams with the transmission weight calculated with respect to the reception antenna that corresponds to the each of the plurality of data streams, and combining the plurality of weighted data streams for each of the plurality of transmission antennas; and   means for respectively transmitting the plurality of combined data streams from the plurality of transmission antennas.   
     
     
         6 . A wireless communication method for a wireless communication system which includes:
 a transmission device comprising a plurality of transmission antennas; and   a MIMO reception device comprising a plurality of reception antennas, the wireless communication method comprising:   converting, by the transmission device, transmission data addressed to the MIMO reception device to a plurality of data streams that respectively correspond to the plurality of reception antennas, by performing predetermined MIMO precoding on the transmission data;   calculating, by the transmission device, a transmission weight with respect to each of the plurality of reception antennas so that the plurality of transmission antennas form a directivity pattern directed toward the each of the plurality of reception antennas;   generating, by the transmission device, a plurality of combined data streams that are to be supplied respectively to the plurality of transmission antennas, by weighting each of the plurality of data streams with the transmission weight calculated with respect to the reception antenna that corresponds to the each of the plurality of data streams, and combining the plurality of weighted data streams for each of the plurality of transmission antennas;   respectively transmitting, by the transmission device, the plurality of combined data streams from the plurality of transmission antennas;   receiving, by the plurality of reception antennas of the MIMO reception device, the plurality of combined data streams respectively transmitted from the plurality of transmission antennas; and   acquiring, by the MIMO reception device, the transmission data by performing MIMO decoding that corresponds to the predetermined MIMO precoding on the plurality of combined data streams received by the plurality of reception antennas.