Relay selection schemes in threshold DF cooperative systems with wireless power transfer

In this work, a dual-hop cooperative wireless energy harvesting system, in which there are a Source-Destination (S−D) pair and several relay candidates is considered. all relay candidates adopt threshold decode-and-forward (DF) relaying scheme to decide whether to aid S−D pair information transmission or not. We assumed that these relay candidates and S are all equipped with single receiving antenna while D is equipped multiple receiving antenna and adopts generalized selection combining scheme to achieve receiving diversity gain. We also consider that relay candidates and S can harvest energy from D with finite energy storage capacity under time switching scheme. Three kinds of best relay selection (RS) schemes based threshold (TH) DF relay scheme, that is, the TH optimal source-relay link, the TH optimal relay-destination link, and the TH optimal source-relay-destination link, are proposed and studied. Closed-form analytical expressions for the outage probability over the three proposed RS schemes are derived and verified by Monte-Carol simulations.