Stochastic Energy Harvesting and Relay Selection for Two-Way Dual-Relay Networks

Wei Li,Zhonghua Liang,Yichen Wang,Meng-Lin Ku

doi:10.1109/access.2019.2938550

Abstract

The optimal transmission policy is investigated for two-way (TW) energy harvesting (EH) dual-relay networks with a stochastic EH model. There exist two solar-powered relays which have finite-sized batteries, and at most one relay is selected to facilitate the network’s information exchange. The objective is to optimize the network’s long-term outage performance by adapting the relay selection and power allocation to the system stochastic conditions. Thus, a Markov decision process (MDP) is utilized to formulate the design framework. From the MDP, the optimal transmission policy of the network is derived to indicate the adaptive relay selection and power allocation, and the computation of the network’s expected outage probability is presented. Further, the optimal transmission policy is asymptotically analyzed, and an active relaying property and a power convergency property of the optimal policy are pointed out. Moreover, according to the properties of the optimal policy, the long-term outage probabilities of the network are found to approach the limitation in sufficiently high SNRs, which is determined by the empty probability of the dual-battery under the optimal policy. Finally, computer simulations validate the analysis.

Highlights

Energy harvesting (EH) communications in wireless networks have become popular due to the efficient solutions to energy supply problems for wireless communication nodes which have no fixed power supply [1]
We focus on the TW relay network with two EH relays and investigate the more complicated transmission policy on the joint relay selection and power allocation
Theorem 2: In the TW EH dual-relay network with the optimal relay selection and power allocation, the expected values of the outage probabilities in sufficiently high SNRs are approximately equal to the empty probability of the dual-battery related with the two EH relays

Summary

INTRODUCTION

Energy harvesting (EH) communications in wireless networks have become popular due to the efficient solutions to energy supply problems for wireless communication nodes which have no fixed power supply [1]. Based on the above discussions, in the optimal transmission policy of the considered network, the long-term outage probability-based criterion is proposed to fulfill the adaptive relay selection and power allocation. This problem is basically a type of stochastic optimization about the resource management under the consideration of system stochastic conditions. MARKOV DECISION PROCESS DESIGN In the TW EH dual-relay network, the objective is to select the optimal relay and compute its transmit power jointly and dynamically, so as to optimize the long-term outage performance under the consideration of the causal EH status, the available energy stored in the two relays’ batteries and the wireless channel fading. In order to tackle this stochastic optimization problem, as referring to the optimization method in [5], the system is formulated as an MDP whose elements are described in the following

TRANSMISSION ACTION

SYSTEM STATE

EXPECTED OUTAGE PROBABILITY

ASYMPTOTIC ANALYSIS

SIMULATION RESULTS

CONCLUSION