Transmitter

#The present invention relates to a transmitter employing an orthogonal frequency division multiplexing (OFDM) system.

#Priority is claimed on Japanese Patent Application No. 2005-314429, filed Oct. 28, 2005, the content of which is incorporated herein by reference.

#In recent years, multi-carrier transmission has been proposed that uses cyclic delay transmit (CDT) diversity that simultaneously performs transmission from a transmitter that is provided with a plurality of transmission antennas while adding a (cyclic) delay that differs for each transmission antenna (Non-patent document 1). When using this diversity method, since the frequency selectivity of channels can always be strongly achieved, excellent average bit error rate (BER) performance can be obtained.

#FIG. 1A is an outline view in the case of a transmitter and a receiver performing communication.

#FIG. 1B is a drawing that shows the constitution of a signal s5 that is transmitted from the transmitter 3a.

#FIG. 1C is a drawing that shows the constitution of a signal s6 that is transmitted from the transmitter 3b.

#Hereinbelow, embodiments of the present invention will be described with reference to the attached drawings. Note that the numeric values used in the embodiments of the present invention e.g. the numbers of frequency subchannels are merely examples.

#In the first to third embodiments of the present invention, an orthogonal frequency division multiple access (OFDMA) system shall be described assuming that the number of frequency subchannels is 12, the number of subcarriers is 768, and the number of FFT points is 1,024. Also, the frequency subchannel that realizes the path diversity differs for every frame. That is, the description is given for the cases of whether or not to perform soft combining for each frequency subchannel or the delay amount being independently determined for each frequency subchannel, but is not limited thereto.

#The first embodiment of the present invention will be described first. The present embodiment shows an example using two differing transmitters that use OFDMA and performing communication with some receivers. FIG. 1A is a schematic diagram of the case of transmitters communicating with receivers. During the time that the OFDMA frame that is the object of the description being transmitted, the receivers 4a to 4c perform communication with the transmitter 3a. Also, the receivers 4b to 4e perform communication with the transmitter 3b. That is, the receivers 4b and 4c combine and receive the same signals from both transmitters 3a and 3b by soft combining.