Energy efficiency of cooperative diversity at PHY layer in wireless sensor networks

In this paper, the energy efficiency of a method to implement cooperative diversity at PHY layer is studied for the reach-back problem in wireless sensor networks, in which orthogonal channel allocation and network synchronization are not necessary. The conditions under which PHY cooperative diversity outperforms direct transmission in terms of total energy consumption including transmission and circuit energy are analyzed. To avoid synchronization among all cooperative nodes, random delay is introduced before relaying, which can achieve the trade-off between energy efficiency and system complexity.