Transmit Power Minimization for Wireless Networks with Energy Harvesting Relays

TL;DR

This paper proposes a relay-assisted energy harvesting framework for wireless networks, optimizing power and relay selection to minimize source transmit power, achieving near-optimal performance with fewer relays and energy diversity benefits.

Contribution

It introduces a joint power assignment and relay selection framework for EH relays, with a novel feasibility condition that enables efficient sub-optimal algorithms and reduces reliance on non-causal EH information.

Findings

Achieves near-optimal power minimization performance.

Significantly reduces the number of relays needed.

Demonstrates the energy hardening effect and its benefits.

Abstract

Energy harvesting (EH) has recently emerged as a key technology for green communications as it can power wireless networks with renewable energy sources. However, directly replacing the conventional non-EH transmitters by EH nodes will be a challenge. In this paper, we propose to deploy extra EH nodes as relays over an existing non-EH network. Specifically, the considered non-EH network consists of multiple source-destination (S-D) pairs. The deployed EH relays will take turns to assist each S-D pair, and energy diversity can be achieved to combat the low EH rate of each EH relay. To make the best of these EH relays, with the source transmit power minimization as the design objective, we formulate a joint power assignment and relay selection problem, which, however, is NP-hard. We thus propose a general framework to develop efficient sub-optimal algorithms, which is mainly based on a sufficient condition for the feasibility of the optimization problem. This condition yields useful design insights and also reveals an energy hardening effect, which provides the possibility to exempt the requirement of non-causal EH information. Simulation results will show that the proposed cooperation strategy can achieve near-optimal performance and provide significant power savings. Compared to the greedy cooperation method that only optimizes the performance of the current transmission block, the proposed strategy can achieve the same performance with much fewer relays, and the performance gap increases with the number of S-D pairs.