Preamble-based joint frame and frequency synchronization for OFDM — WMAN systems

Orthogonal frequency-division multiplexing (OFDM) is a well known multi-carrier digital modulation scheme in which a transmitted data is split into multiple streams that are modulated at different frequencies. The OFDM system is very sensitive to frame and frequency synchronization errors. In this paper, we propose a preamble for frame and frequency synchronization in OFDM systems. The preamble is generated by loading the BPSK data on alternate subcarriers in a symmetric manner. By using the proposed preamble, a frame synchronization method for OFDM systems is described. And, it is shown that the proposed frame synchronization method yields sharp peak at the frame boundary and is independent of carrier frequency offset. Also, we proposed preamble based fractional as well as integer frequency offset estimation techniques. These techniques do not require the prior knowledge of PN sequence or CP length used at the transmitter. Simulations are conducted for AWGN and frequency selective channels to demonstrate the performance of the proposed methods. Simulations show that the proposed frame and frequency synchronization techniques yield good results for SNR >; 2dB.