Solar Energy Harvesting Using a Timer-Based Relay Selection

Abstract

In this paper, the throughput and delay of cooperative communications are derived when solar energy is used and relay node is selected using a timer. The source and relays harvest energy from sun using a photo voltaic system. The harvested power is used by the source to transmit data to the relays. Then, a selected relay amplifies the signal to the destination. Opportunistic, partial and reactive relay selection are used. The relay transmits when its timer elapses. The timer is set to a value proportional to the inverse of its Signal to Noise Ratio (SNR). Therefore, the relay with largest SNR will transmit first and its signal will be detected by the other relays that will remain idle to avoid collisions. Harvesting duration is optimized to maximize the throughput. Packet's waiting time and total delay are also computed. We also derive the statistics of SNR when solar energy is used. The harvested power from sun is proportional to the sum of a deterministic radiation intensity and a random attenuation due to weather effects and clouds occlusion. The fixed radiation intensity depends on season, month and time t in hour. The throughput of cooperative communications with energy harvesting from sun was not yet studied.