Outage analysis of cognitive relay networks with energy harvesting and information transfer

We investigate a wireless energy harvesting and information transfer protocol in cognitive relay networks, where an energy harvesting secondary network shares the spectrum as well as harvests energy by assisting the primary transmission. In particular, the secondary transmitter scavenges energy from the received primary signal and then forwards the resulting signals along with the secondary signal. The secondary receiver can also harvest the ambient energy, and use the remaining signal to remove the primary interference. We analytically derive the exact expressions of the outage probabilities for both primary and secondary networks. Based on the proposed protocol, we analyze the rate-energy trade-off between the maximum ergodic capacity and the maximum harvested energy in the secondary network. Our results demonstrate that the proposed protocol not only achieves both the primary and secondary transmissions but also harvests the ambient energy without the performance loss.