基于SWIPT的半双工中继QF协作可达速率分析

为解决中继节点能量受限的问题及提高系统能量效率以实现可靠绿色通信，提出了基于无线携能传输（SWIPT）技术的半双工中继量化转发（QF）协作系统.首先，建立基于SWIPT的半双工中继QF协作系统模型，信源节点和目的节点由电源供电，中继节点通过SWIPT技术同时实现信息传输和能量收集；其次，在功率分割协议下，推导出基于SWIPT的QF协作的可达速率表达式，证明可达速率是关于功率分割因子的凸函数，并求解出最优功率分割因子以优化可达速率；然后，针对慢衰落信道，进一步分析了基于SWIPT的QF协作的预期速率；最后，理论分析与仿真结果表明，基于SWIPT的QF协作的可达速率或预期速率均明显优于传统放大转发和译码转发协作，并且基于SWIPT的QF协作在中继节点没有外部供电的情形下，能达到与传统QF协作相近的性能.

Achievable Rate of the SWIPT-Based Half-Duplex Relay QF Cooperative System

Aiming to solve the problem of energy limitation of relay node and improve the energy efficiency of the system for achieving reliable green communication,the half-duplex relay quantize-and-forward(QF) cooperative system is studied based on simultaneous wireless information and power transfer(SWIPT). Firstly,a SWIPT-based half-duplex relay QF cooperative system model is established. The source node and destination node are powered by external power. The relay node simultaneously implements information transmission and energy harvesting by SWIPT. Then,for the power-splitting protocol,the achievable rate expression of the SWIPT-based QF cooperation is derived. It is proved that the achievable rate is a convex function with respect to the power-splitting factor,and the optimal power-splitting factor is obtained to maximize achievable rate. Furthermore,for slow fading channels,the expected rate of SWIPT-based QF cooperation is further analyzed. Finally,the analysis and simulation shows that the achievable rate or expected rate of SWIPT-based QF cooperation is obviously superior to that of traditional amplify-and-forward and decode-and-forward cooperation,and SWIPT-based QF cooperation achieves similar performance to that of traditional QF cooperation in the absence of external power supply for the relay.