Quasi-Synchronous Cooperative Networks: A Practical Cooperative Transmission Protocol

In this article, we propose a cooperative space-time coding (STC) protocol, amalgamating the concepts of asynchronous cooperation, noncoherent detection, as well as distributed turbo coding (DTC), where neither symbol-level time synchronization nor channel-state information (CSI) estimation is required at any of the cooperating nodes, while attaining high performance even at low signal-to-noise ratios (SNRs). More specifically assuming the system configuration of a single source node, multiple relay nodes, and a single destination node, each having a single antenna element (AE)a practical cooperative differential space-time spreading (CDSTS) scheme is designed using interference rejection spreading codes, to eliminate the effect of synchronization errors between the relay nodes without the assistance of channel estimation or equalization.