Relay Selection in Energy Harvesting Two-way Communication Networks

In this work, a bi-directional network is considered where two single-antenna transceivers communicate with each other through multiple energy harvesting relay nodes. This communication is accomplished using a single-carrier scheme by exchanging the signal blocks between the transceivers. Since the distances between the transceivers through different relaying paths are not the same, the propagation delay of each path is different than the others. As a result, at sufficiently high data rates, the end-to-end multi-path channel is time-dispersive (frequency-selective) and inter-symbol-interference (LSI) is not avoidable at the both transceivers (in our single-carrier scheme the received signal blocks experience inter-block-interference (IBI)). A relay selection scheme is proposed to combat such an IBI by switching on the relay nodes that contribute to a single tap of the end-to-end channel and turning off the remaining relays. For each tap of the channel, an optimal relay beamformer is designed in order to maximize the transmission rate when the energy consumed by the relays to transmit a signal block is restricted to the harvested energy so far and a minimum desired signal-to-noise ratio (SNR) at the both transceivers is guaranteed. The performance of such an energy harvesting network design is illustrated by presenting the simulation results.