Relay Selection in Cooperative Networks with Wireless Battery Charging

This paper studies the problem of relay selection in wireless powered cooperative networks, where spatially random relays are equipped with two-state batteries. In contrast to conventional techniques, the relay nodes can either harvest energy from the source signal (in case of uncharged battery) or attempt to decode and forward it (in case of charged battery). Three relay selection schemes that correspond to different state information requirements and implementation complexities are proposed. The charging/discharging behavior of the battery is modeled as a two-state Markov chain and analytical expressions for the steady-state distribution and the outage probability performance are derived for each relay selection scheme. We prove that energy storage significantly affects the performance of the system and results in a zeroth diversity gain at high signal-to-noise ratios.