Radio communication system, radio communication method, radio transmitter and radio receiver

A radio communication method for a radio communication system including a radio transmitter having a plurality of transmission antennas and a radio receiver having a plurality of reception antennas, said method comprising the steps of,

• in the radio transmitter,
• selectively producing (a) transmission data to be transmitted with a directive multibeam from said plurality of transmission antennas in a first mode or (b) transmission data to be independently transmitted from said plurality of transmission antennas in a second mode;
• carrying out an orthogonal transformation on a plurality of pilot signals having an orthogonal relation to each other so as to form said directive multibeam having the orthogonal relation;
• multiplexing the orthogonally transformed pilot signals and said transmission data and transmitting the multiplexed data through said plurality of transmission antennas;
• and
• in said radio receiver,
• correlating, for each of said reception antennas, a received signal received by said reception antenna with a replica signal of each of said pilot signals to obtain a channel estimate of said directive multibeam;
• carrying out an inverse transformation of said orthogonal transformation on the obtained channel estimate of said directive multibeam to obtain a channel estimate corresponding to one of said plurality of transmission antennas;
• and
• selectively conducting (a) first received signal processing on the basis of said channel estimate of said directive multibeam and said received signal in said first mode, or (b) second received signal processing on the basis of said channel estimate corresponding to said one of said plurality of transmission antennas, obtained through said inverse transformation, and said received signal in said second mode.

A radio transmitter comprising:

• a plurality of transmission antennas;
• a transmission data producing unit selectively producing (a) transmission data to be transmitted with a directive multibeam from said plurality of transmission antennas in a first mode or (b) transmission data to be independently transmitted from the plurality of transmission antennas in a second mode;
• an orthogonal transformation unit carrying out an orthogonal transformation on a plurality of pilot signals having orthogonal relation to each other so as to form said directive multibeam having the orthogonal relation;
• and
• a pilot multiplexing unit multiplexing said orthogonally transformed pilot signals produced by said orthogonal transformation unit and said transmission data produced by said transmission data producing unit.

A radio receiver comprising:

• a plurality of reception antennas for receiving a signal transmitted from a plurality of transmission antennas, said signal being a multiplexed signal of pilot signals having orthogonal relation to each other and first transmission data to be transmitted through a directive multibeam from said plurality of transmission antennas in a first mode, or said signal being a multiplexed signal of said pilot signals and second transmission data to be transmitted independently from said plurality of transmission antennas in a second mode, said pilot signals being carried out by an orthogonal transformation between the plurality of transmission antennas of a radio transmitter;
• a channel estimation unit correlating, for each of said reception antennas, said received signal received by said reception antenna with a replica signal of each of said pilot signals to obtain a channel estimate of said directive multibeam;
• an inverse transformation unit carrying out an inverse transformation of said orthogonal transformation on said channel estimate of said directive multibeam obtained by said channel estimation unit to obtain a channel estimate corresponding to one of said plurality of transmission antennas;
• and
• a received signal processing unit selectively conducting (a) first received signal processing on the basis of said channel estimate of said directive multibeam obtained by said channel estimation unit and the received signal in said first mode, or (b) second received signal processing on the basis of said channel estimate corresponding to said one of said plurality of transmission antennas obtained by said inverse transformation unit and the received signal in said second mode.