Performance analysis of OFDMA uplink synchronization based on phase shift of channel responses between adjacent subcarriers

Time offset estimation is one of the main tasks of the initial ranging process in orthogonal frequency-division multiple access (OFDMA)-based network. Recently, the multiuser time offset estimation based on phase shift over adjacent subcarriers has been presented. This method can reduce the huge computation complexity of the timing recovery based on peak correlation searching of long PN codes. The performance of this multiuser uplink synchronization method under the multipath fading environment is investigated in this paper. Specifically, the dependence of time offset estimation error on subcarrier spacing, SNR and frequency selectivity of the channel impulse response is studied. Simulation results show that with the increase of subcarrier spacing, the accuracy of time offset estimation will be improved. However, the maximum time offset delay to be estimated will be reduced. Furthermore, this method is very sensitive to SNR when the subcarrier spacing is small and the accuracy of time offset estimation will be reduced with the increasing of multipath delay spread.