Patent ID: 7336598

Claim:
A guard interval length determining apparatus in an OFDM (orthogonal frequency division multiplexing) system, comprising: a signal supply section which outputs a reception signal and a delayed reception signal obtained by delaying said reception signal by a length of an effective symbol section; and a guard interval length determining section which adaptively determines a final guard interval section length from said reception signal and said delayed reception signal, wherein said guard interval length determining section calculates at least a correlation value between a part of an effective symbol section of said reception signal and a part of a guard interval section of said delayed reception signal, determines a guard interval section length based on said correlation value, and outputs said final guard interval section length based on the determined guard interval section length, wherein said guard interval length determining section comprises: a correlation processing section which calculates said correlation value between the part of said effective symbol section of said reception signal and the part of said guard interval section of said delayed reception signal; an averaging section which averages said correlation values over a plurality of symbols, and outputs the average as a correlation value; and a determining section which determines the guard interval section length based on the correlation value from the averaging section, and determines said final guard interval section length based on the determined guard interval section length.