Performance of Wireless Powered DF Relay System Under Nakagami-$m$ Fading: Relay Assists Energy-Constrained Source

We consider a two-hop decode-and-forward relay system with an energy-constrained source node. Relay node wirelessly powers the source and assists in forwarding the data to the destination. The direct link is considered to be deeply faded and other links are Nakagami-
$m$
faded. Data at the source are transmitted in two time-slots. In the odd time slot, the source sends data to the relay node and in the even time slot, the relay node forwards the data. Since source and destination are in the coverage range of the relay node, both receive radio frequency signal transmitted by the node in even slot. The received signal is used simultaneously at the source to harvest energy and at the destination to detect the relayed data. Harvested energy at the source is used to transfer data to the relay node in the subsequent time slot. The average symbol error rate (SER) of the system is derived when data are 1)
$M$
-ary phase-shift keying modulated with coherent detection and 2) orthogonal
$M$
-ary frequency-shift keying modulated with noncoherent detection. The corresponding high-signal-to-noise ratio (SNR) approximations of the average SER are obtained. The effects of modulation order, channel conditions, and relay placement on the system’s performance are investigated.