A New Synchronization Scheme for OFDM-Based Cooperative Relay Systems

In cooperative relay systems, relayed signals propagate through different channels and are received at the destination node with distinct timing and carrier frequency offsets (CFOs). This feature makes synchronization a rather challenging task as compared with centralized multiple-input multiple-output systems. Unlike conventional preamble designs with good correlation properties only in time domain or frequency domain, a new preamble that has good correlation properties in both time domain and frequency domain is proposed for synchronization in orthogonal frequency-division multiplexing (OFDM) based cooperative relay systems. According to the proposed preamble, a synchronization scheme is developed and a practical threshold is derived that jointly considers the statistic distribution of the correlation function output and the inevitable interference originated from residual CFOs to assist fine timing synchronization. Simulation results verify that the proposed scheme provides notable performance improvement as compared with a previous related work.