ML synchronization algorithm and estimation bounds for cooperative systems

In this paper, we propose a maximum-likelihood (ML) estimation method for synchronization in decode-and-forward (DF) cooperative systems. We focus on the estimation problem of the multi timing and frequency offsets in the second phase, the multiple-input-single-output (MISO) multiple access phase of cooperative communications. Different from the conventional methods which estimate the timing or frequency offsets separately, we propose a joint timing-frequency offsets and channel estimation scheme to achieve better performance. In addition, the lower bounds, the Cramér-Rao bounds (CRB) of the multiple parameter estimation are also provided. The simulation results show that the performance of our estimation scheme can reach the CRB.