Performance Analysis of Wireless Powered DF Relay System Under Nakagami-$m$ Fading

Abstract

In this paper, we analyze the average symbol error rate (SER) for a wireless powered three-node decode-and-forward (DF) relaying system in Nakagami- $m$ fading environment. $M$ -ary phase-shift keying modulated data at source is communicated to destination through energy-constrained relay node in three time slots. In the first slot, the signal transmitted by the source is used for energy harvesting at the relay node. Next two slots are employed for selective DF relaying, where relay transmits using the energy harvested from the source node. The source node is assumed to have a dedicated power supply. We analyze the end-to-end average SER expressions using the moment generating function based approach for two relaying scenarios: i) the direct link between the source and the destination exists and ii) the direct link is deeply faded and therefore can be ignored. The asymptotic approximations of the average SER are also obtained to determine the optimal energy allocated for each transmission. Since energy is related to the power transmitted at a node and the slot duration, the optimal energy expression can be judiciously used to optimize power and time for the corresponding slot. The effects of modulation order, relay placement, and channel conditions on the performance of the system with and without optimal resource allocation are investigated. The achievable diversity order and the throughput are also analyzed.