Battery-Aware Relay Selection for Energy Harvesting Cooperative Networks
  The use of energy harvesting (EH) nodes as cooperative relays is an emerging solution for enabling green wireless systems. In this paper, we consider multiple EH relay nodes harvesting energy from the radio frequency (RF) signal received from the source and use that harvested energy to forward the source information to the destination. Unlike conventional relays with fixed power supplies, EH relays may not be permanently available to assist the source transmission due to the limited energy conversion efficiency, the mismatch between the charging and discharging profiles, and the finite energy storage capacity. We propose the battery-aware relay selection (BARS) scheme, which jointly considers the channel condition and the battery status for relay selection. The outage probability of the proposed scheme is analyzed using a Markov chain model. Simulations are performed to validate the analysis accuracy. Through numerical results, we show that the proposed BARS scheme can achieve full diversity order equal to the number of relays without the need of fixed power cables. 
Yu-Hsien Lee and Kuang-Hao Liu
cs.IT math.IT