Virtual MIMO Channels in Cooperative Multi-hop Wireless Sensor Networks

In this paper we analyze the performance of virtual multiple-input-multiple-output (MIMO) channels for multi-hop transmission in wireless sensor networks. First, we propose a clustered network topology with sensor nodes grouped in collaborative sets attending to proximity. Then, we propose that all nodes belonging to any given cluster cooperatively transmit and receive data from other clusters, exploiting the diversity advantages of cluster-to-cluster virtual MIMO channels. In order to construct the cooperative transmission, we arrange each hop into two consecutive time slots: the intracluster slot, that accounts for data sharing within the cluster, and the intercluster slot for transmission between clusters; and we devise a cooperative reception protocol within the clusters based upon a simplified selection diversity algorithm. Optimum time assignment and power allocation for both slots are derived taking the cluster-to-cluster probability of outage as the metric. Results for one hop networks and for multi-hop networks are obtained, showing substantial diversity gains and energy savings. Furthermore, results show that the performance of the proposed virtual MIMO channels is equal to that of real MIMO channels but for a small SNR loss.