A novel three-hop cooperative diversity system model is proposed in this paper comparing to conventional dual-hop cooperative systems, assuming all terminals have only one antenna for size limitation. This system model avoids complex relay selection criterions and data forwarding strategies which are necessary for conventional cooperative systems to optimize their performance. Both source node and destination node request free nodes around them to perform as virtual antenna arrays based on the simplest selection criterion, and then a virtual multiple-input multiple-output (MIMO) system is constructed. Different from the systems reported in literatures, signals from source node need three hops before arriving at destination. We show that if channels between destination node and its virtual antennas are better than channels between source and destination, symbol error rate (SER) of this virtual MIMO system can approximate the performance of actual MIMO system.