Power Allocation for Virtual MIMO-Based Three-Stage Relaying in Wireless Ad Hoc Networks

In the conventional dual-hop cooperative communications, relays with imbalanced channel condition to the source or the destination may become the bottleneck of the overall cooperation. Therefore, in this paper, a Three-Stage Relaying (TSR) framework is proposed for clustered networks to extend the dual-hop cooperation to three stages by dividing relays into two groups. The long-haul communication between two groups form a virtual multi-input multi-output (MIMO) link with which the bottleneck between the relay and the source (or the destination) can be removed. We focus on the power allocation problem based on this framework, with the objective of minimizing the outage probability at the destination under the total power constraint. To address the computational complexity, the problem is decomposed into two subproblems, one deals with the power allocation of the source and the first-hop relays, the other deals with the power allocation of the second-hop relays. We design the algorithms for each subproblem by exploiting their special structure, and then develop a master procedure to handle the power allocation across these subproblems. The performance of the proposed scheme is evaluated through simulation study, which shows that the TSR framework achieves significant improvement on the outage probability compared with the dual-hop cooperation scheme, and the power consumption is more fairly distributed across relays.