QoS aware power allocation in multi-hop multi-relay network

Considering the quality-of-service (QoS), power allocation is a critical importance issue in realizing multi-hop relay systems. In this paper considering the QoS Constraints in term of BER or instantaneous SNR, an optimal power allocation scheme that minimized the total power consumption in an amplify-and-forward (AF) multi-hop multi-branch transmission system is proposed. Considering an asymptotic expression for the target SNR as the QoS Constraint, we formulate our optimization problem as two standard convex optimization problems. Solving these problems we present an optimum power allocation algorithm which at first performs a branch selection phase holding the QoS Constraint, and then, drive a minimum total consumption value and also an optimal power allocation coefficient for their corresponding source and relay nodes. Optimized power allocation demonstrates a significant power saving performance over the uniform power allocation while guarantees the target SNR.