Maximum likelihood multiuser timing synchronization scheme for asynchronous multirate multicarrier CDMA system

In this paper, a robust multiuser timing synchronization algorithm based on maximum likelihood (ML) for asynchronous multirate multicarrier (MC-) code division multiple access (CDMA) system over frequency selective fading channel is proposed. Channel fading is assumed to be time invariant over the synchronization period. Both the spreading codes and preamble sequences for all users are assumed to be known by the base station receiver. The proposed synchronization algorithm is decoupled to make the algorithm computational efficient. Simulation results show the robustness and effectiveness of the proposed synchronization algorithm, in terms of its strong resistance to the noise, total number of users, near far problem and multipaths fading.