Outage Performance of Multi-relay System with Energy Harvesting and Storage

Abstract

This paper analyzes the performance of a two-hop half-duplex multi-relay system based on energy harvesting. The relay has energy harvesting and storage functions, and adopts an adaptive AF/DF transmission strategy and PS protocol. Based on three relay selection schemes, namely Energy Optimal Selection (EOS), Channel Gain Optimal Selection (GOS), and Energy and Channel Gain Optimal Selection (EGOS), the outage performance is compared. First, the finite state Markov chain (FSMC) is used to model the energy arrival and use status of each relay, and the energy transfer steady-state matrix is obtained. Then we use the Gauss Chebyshev formula to derive the analytical expression of the communication outage probability (COP). Finally, an optimization model for minimizing the COP for three relay selection schemes is constructed. The EOS and GOS schemes optimize power allocation for energy harvesting and information transmission, and the EGOS scheme jointly optimizes power allocation and energy thresholds. We use a one-dimensional search algorithm based on the golden section and a two-dimensional search algorithm based on iteration to solve these optimization problems. The simulation results show that the EGOS is the best among the three relay selection schemes.