Switch-and-stay combining for energy harvesting relaying systems

In this paper, we study the switch-and-stay combining technique into the energy-harvesting relaying networks, where the relay obtains its transmit power from the source through wireless energy harvesting. The moderate shadow environments are applied, so that the data transmission from the source to the destination can go through the direct link. Although the conventional selection combining technique can exploit both the direct and relaying branches for data transmission, it has to require to know the channel parameters of both branches, and results into frequent branch switching. To solve these issues, switch-and-stay combining (SSC) is proposed into the energy-harvesting relaying networks, where the same branch keeps to be used for data transmission when it can support the transmission quality. The branch switching occurs only when the branch cannot support the transmission quality. We study the system transmission performance by deriving expression for the system analytical outage probability. We also provide the asymptotic outage probability when the transmit power is high, from which we obtain more insights on the system design, such as the system diversity order and the impact of parameters on the system performance. Simulation and numerical results are provided to validate the proposed studies in this paper.