Wireless-Powered Cooperative Communications: Power-Splitting Relaying with Energy Accumulation

TL;DR

This paper introduces a harvest-use-store power splitting relaying strategy with distributed beamforming for wireless-powered multi-relay networks, optimizing energy utilization and throughput through layered and greedy methods under different CSI conditions.

Contribution

It proposes a novel energy accumulation strategy with joint PS and battery operation optimization, extending to causal CSI scenarios and providing practical greedy algorithms.

Findings

Layered optimization achieves near-optimal performance with non-causal CSI.

Greedy method offers a low-complexity alternative with acceptable performance.

Proposed strategy outperforms conventional PS and time switching relaying methods.

Abstract

A harvest-use-store power splitting (PS) relaying strategy with distributed beamforming is proposed for wirelesspowered multi-relay cooperative networks in this paper. Different from the conventional battery-free PS relaying strategy, harvested energy is prioritized to power information relaying while the remainder is accumulated and stored for future usage with the help of a battery in the proposed strategy, which supports an efficient utilization of harvested energy. However, PS affects throughput at subsequent time slots due to the battery operations including the charging and discharging. To this end, PS and battery operations are coupled with distributed beamforming. A throughput optimization problem to incorporate these coupled operations is formulated though it is intractable. To address the intractability of the optimization,a layered optimization method is proposed to achieve the optimal joint PS and battery operation design with non-causal channel state information (CSI), in which the PS and the battery operation can be analyzed in a decomposed manner. Then, a general case with causal CSI is considered, where the proposed layered optimization method is extended by utilizing the statistical properties of CSI. To reach a better tradeoff between performance and complexity, a greedy method that requires no information about subsequent time slots is proposed. Simulation results reveal the upper and lower bound on performance of the proposed strategy, which are reached by the layered optimization method with non-causal CSI and the greedy method, respectively. Moreover, the proposed strategy outperforms the conventional PS-based relaying without energy accumulation and time switching-based relaying strategy.