Outage Analysis of Energy Harvesting based Opportunistic Cooperative Communication Systems

Wireless energy harvesting constitutes an effective way to prolong the lifetime of wireless networks. In this paper, an opportunistic decode-and-forward cooperative communication system is investigated, where the energy-constrained relays harvest energy from the received information signal and the co-channel interference (CCI) signals and then use that harvested energy to forward the correctly decoded signal to the destination. Different from conventional relaying system with constant energy supplier, the transmission power of the energy-constrained relay depends on the available energy that harvested, which is a random process. Best relay selection that takes into account all the impacting ingredients on the received signal quality at the destination is deployed. The exact closed-form expression of the outage probability is derived, and the optimal value of the energy harvesting ratio for achieving minimum outage is numerically investigated. In addition, the impacts of the CCI signals on the system's outage and diversity performances are analyzed. It is shown that the proposed relaying scheme can achieve full diversity order equal to the number of relays without the need of fixed power supplier.