A robust joint estimator for OFDM timing and frequency offsets based on PN codes

A joint estimator for OFDM symbol timing and fractional frequency offsets is proposed based on cyclic shifting and autocorrelation properties of PN (pseudo noise) codes. In the proposed scheme, for the joint estimation of both timing and frequency offsets, a newly designed time domain preamble sequence which has the same length with the number of IFFT points and consists of twice-repeated PN codes, is utilized. Moreover, in order to achieve robustness in multipath fading channels, a new timing metric by considering delay spread of the multipath channel is also applied. Simulation results show that the proposed estimation scheme is more robust to multipath channels than the conventional OFDM symbol timing estimation schemes. Furthermore, the proposed joint estimator also provides quite reliable fractional frequency estimation.