A receiver employing an OFDM system which uses a frequency band that is constituted by a plurality of subchannels, and receiving a signal added a phase rotation which is made to respectively differ for each transmission antennas of transmitter and transmitted from the transmission antennas, having an informing portion which informs the transmitter of an information in subchannel units for deciding a phase rotation which is added to the signal.
1. A communication system comprising:
a receiver; and
a transmitter;
the receiver employing an OFDM system which uses a frequency band that is constituted by a plurality of subchannels, and receiving a signal added a phase rotation which is made to respectively differ for each transmission antennas of the transmitter and transmitted from the transmission antennas, the receiver comprising:
an informing portion which informs the transmitter of an information for adding a same phase rotation to a plurality of consecutive subcarriers of the subchannels;
a receiving portion which receives subcarriers for propagation path estimation in which phase rotation has not been added at the transmitter side; and
a quality estimating portion which estimates a quality of the received subcarriers; and
the transmitter comprising:
a phase rotating portion applying a first phase rotation amount to a first group and a second phase rotation amount to a second group,
wherein the first group comprises a first plurality of consecutive subcarriers,
wherein the second group comprises a second plurality of consecutive subcarriers, and
wherein the first plurality of consecutive subcarriers are different subcarriers than the second plurality of consecutive subcarriers.