WiMAX timing and frequency synchronization based on training sequence

In all wireless communication systems and especially in OFDM and MIMO-OFDM system synchronization is crucial. The receivers do not know the beginning and the end of the OFDM symbols, so the placement of the FFT window. Moreover, they have their own sampling frequency asynchronous with that of the transmitter. These two points show two synchronization concepts: time and frequency. An error of time synchronization in the reception may cause loss of the orthogonality of subcarriers. This is why it is important to have a robust synchronization algorithm and know its effect on system performance. Several estimation techniques for time and frequency offset have been proposed in the literature, but varied test conditions make comparison difficult. In this paper, we use Schmidl and Cox algorithm as a symbol timing synchronization algorithm for OFDM system. We also see the preamble structure using the equations provided in the IEEE 802.16d. Simulation results show the effect caused by carrier frequency offset (CFO) and timing frequency offset (STO) on the performance of an OFDM system in a WiMAX context.