Patent ID: 7298692

Claim:
A radio base station apparatus comprising: a receiving section that receives a spread uplink signal; a despreading processing section that performs despreading on the received uplink signal; a demodulating section that demodulates the despread signal and acquires delay profile information contained in the uplink signal, comprising information of a delay profile; a guard interval determining section that determines a guard interval in OFDM using the acquired delay profile information; a first modulating section that modulates a data portion; an OFDM processing section that performs OFDM processing on the data portion modulated in the first modulating section using the guard interval; a second modulating section that modulates a preamble portion comprising a known signal for use by a communication terminal apparatus to generate the delay profile; a first spreading section that performs spreading on the preamble portion modulated in the second modulating section; a multiplexing section that multiplexes the data portion subjected to the OFDM processing with the preamble portion subjected to the spreading; and a first transmitting section that transmits the multiplexed data portion subjected to the OFDM processing and the preamble portion subjected to the spreading as a downlink signal.