Cooperation diversity using differential distributed space-time codes

We develop a protocol that permits effective use of differential space-time coding schemes for cooperative diversity systems. The consideration of system design without assuming the knowledge of channel state information (CSI) at the receiver becomes therefore more realistic. With the use of the proposed protocol, it is shown that the use of differential space-time codes in space-time cooperation is feasible with the performance degraded only by 3 dB noise enhancement compared with the coherent detection. The performance of the cooperative diversity system is analyzed for a two-user case for different channel environments in terms of the diversity gain and the diversity product. The optimization of the power allocation between source and relay terminals is considered for the maximization of the diversity product.