Wireless communications have become one of the main stake holders on which our contemporary world relies for carrying out many daily activities. In this era, the number of connected devices is increasing rapidly, contemplating not only smart phone, but also growing connectivity of machines, sensors, and so on. Therefore, it is important to investigate the alternative energy sources for powering these connected small devices. In this paper, we design an RF wireless power transfer scheme for multiple access relay system model with different signal transmission schemes. Here, it is assumed that the sources and relay are self-powered devices and fitted in with rechargeable batteries. Therefore, each node is powered by an RF wireless power transfer that relies on a dedicated energy beam sent from the destination (serves as a power beacon) and other RF transmission links and such approach is referred as opportunistic-harvesting (OH) scheme. An idea of message combining resorting to network coding (NC) and physical layer NC is presented. Performance is demonstrated in terms of error rate and outage probability analyses by using OH. The schemes presented in this paper contribute substantially to sustaining the energy in the proposed scheme. © 2013 IEEE.