Asynchronous Cooperative MIMO Communication

We consider a cluster-based cooperative transmission scheme where the source node and destination node form clusters for transmission. Instead of using perfect synchronization technique, we assume the cooperative transmission is asynchronous. Each member in transmitting cluster relays signal to the receiving cluster after obtaining information from source node. A general decision feedback equalizer (DFE) is used in the receiving cluster members to equalize the received MISO signal and detect as soft symbols. The receiving cluster members send the soft- decision outputs to the destination node. Thus, the decision node combines the soft-decision outputs and makes hard-decision detection for the transmitted information. The performance of proposed system is shown and compared with conventional MIMO system. Major factors for system performance is discussed. The over-sampling rate plays an important role in system performance. We also present a simple capacity analysis for proposed cooperative transmission system. The capacity ratio between cooperative MIMO system and direct transmission (SISO) system is also presented and compared to the capacity ratio of conventional MIMO system and direct transmission (SISO) system. We also extend the analysis to heterogeneous network and show the capacity ratio.