Patent ID: 7639748

Claim:
A method for fine timing synchronization in an orthogonal frequency division multiplexing (OFDM) baseband receiver for IEEE 802.11a or 802.11g wireless local area network (LAN) standards, wherein a received signal of the OFDM baseband receiver has been sampled into a plurality of samples, and the received signal comprises a short preamble, a long preamble, a signal symbol, and a plurality of data symbols, wherein the long preamble is composed of a guard interval and a first long training symbol (LTS) and a second long training symbol (LTS), the method comprising the steps of: detecting an end point of the short preamble; delivering the samples after the end point to a matched filter which correlates the samples with an impulse response of an ideal long training symbol to generate a plurality of correlation peaks; searching the correlation peaks generated from the samples of the first long training symbol for a first maximal peak point where its correlation peak has a first maximal intensity, and obtaining a first time index of the first maximal peak point; storing the correlation peaks which are generated from the samples of the first long training symbol and occur before the first maximal peak point into a shift register; searching the correlation peaks stored in the shift register for a pre-peak point where its correlation peak forms a pre-peak appearing before and nearest from the first maximal peak point, and obtaining a second time index of the pre-peak point; and estimating a third time index of a start point of the second long training symbol according to the first and second time indexes; wherein the samples since the third time index are fed to a fast Fourier transform (FFT) block to perform FFT for channel estimation, so as to achieve fine timing synchronization.