Patent ID: 7450669
Filing Date: 2008-11-11
Classification: H04L

Abstract:
1. An Orthogonal Frequency Division Multiplexing (“OFDM”) demodulation apparatus for receiving an OFDM signal having an effective symbol period among a plurality of effective symbol periods, and demodulating the received OFDM signal, comprising: a transmission mode determining unit determining the effective symbol period of the received OFDM signal, wherein the transmission mode determining unit includes: a plurality of correlators that respectively correspond to the plurality of effective symbol periods, each of the plurality of correlators delaying the received OFDM signal by a corresponding effective symbol period, and outputting a correlation signal that indicates correlation between the delayed OFDM signal and the received OFDM signal; a combiner generating a first correlation signal by combining a plurality of correlation signals output from the plurality of correlators, and outputting the generated first correlation signal; and means for determining the effective symbol period of the received OFDM signal in accordance with the first correlation signal, wherein the OFDM signal further has a guard interval period among a plurality of guard interval periods, and the means for determining the effective symbol period of the received OFDM signal in accordance with the first correlation signal includes: an integrator generating an integration signal by accumulating periods, each of which is a shortest period among the plurality of effective symbol periods and the plurality of guard interval periods, in a predetermined period of the first correlation signal; a delayer generating as many delayed signals as a number of combinations of the plurality of effective symbol periods and the plurality of effective symbol periods, each of the delayed signals being generated by delaying the generated integration signal by a different combination of one of the plurality of effective symbol periods and one of the plurality of guard interval periods; a correlator outputting a plurality of second correlation signals each of which is a correlation signal indicating a correlation between a different one of the delayed signals and the integration signal; and means for determining the effective symbol period and the guard interval period of the received OFDM signal in accordance with a second correlation signal that indicates a largest correlation level among the plurality of second correlation signals.