Preamble-aided symbol and frequency synchronization scheme for OFDM systems

Orthogonal frequency division multiplexing is considered to be an appealing modulation technique for high-speed wireless communication systems owing to its spectral efficiency and robustness against multipath fading. However, an OFDM system is very sensitive to synchronization and a small frequency or timing offset may cause a large inter-carrier interference (ICI), leading to a dramatic degradation in the system performance. This paper presents an efficient symbol and frequency synchronization scheme for OFDM systems that is compatible with IEEE 802.16a standard. A timing algorithm is proposed based on the preamble defined in IEEE 802.16a. The conjugate symmetry of the preamble structure is exploited to reduce computational complexity. It is shown that the new scheme not only reduces the estimation error significantly but also allows for an independent symbol synchronization compared to the conventional methods where a fine timing usually has to be done after the frequency offset correction.