Symbol synchronization in OFDM

Abstract

Orthogonal frequency division multiplexing (OFDM) is a popular transmission technique for high data rate applications. It uses orthogonal subcarriers to transmit data with long symbol duration and thus reduce the effect of inter-symbol-interference due to the multipath channel. However, the successful data detection at the receiver relies on locating the FFT window correctly at the received data sequence ---- the so-called symbol synchronization. In this project, various symbol synchronization techniques are investigated and compared. These include S&C's method, Minn's first method, Minn's second method and Park's method. The performance under an Additive White Gaussian Noise (AWGN), frequency offset, phase offset and multipath channels are investigated. Simulation results and theoretical analysis show that (a) Park's method has the best performance under AWGN channel; (b) all of them are not sensitive to frequency offset and phase offset; (c) they all suffer from the degradation due to multipath channel. In this project, a new symbol synchronization algorithm is proposed. The proposed method uses the combination of Park's method with multiplying the sum of a window on Park's timing metric. The computation complexity is comparable to Park's method. Simulation results show that it has lower estimation mean and variance compared with the above four methods under some multipath channels.