Analysis And Optimization Of SWIPT-based QF Relay Cooperative System

With the speedy progress and development of modern wireless communication technology,the energy loss generated is very huge.So as to comply with the sustainable development strategy,green communication came into being,and greatly reduced the pollution of wireless communications to the global environment.Simultaneously Wireless Information and Power Transfer(SWIPT)technology as a key technology of green communication has gradually become a research hotspot.SWIPT technology can transmit information and energy at the same time,which is an effective method to extend the survival time of wireless communication systems.In the cooperation technology,because the quantized signal is easy to store and exchange,the quantize-and-forward(QF)cooperation method is more conducive to the encryption processing and secure transmission of the signal,and its implementation complexity is lower.So as to settle the issue of the energy restriction of the relay and enhance the performance of the system to realize trustworthy and green communication,in this paper,we research the QF relay cooperation based on SWIPT technology,which is reachable to the system in two modes of half duplex and full duplex.The main researches are as follows:(1)The half-duplex relay Quantize-and-Forward(QF)cooperative system based on Simultaneous Wireless Information and Power Transfer(SWIPT)is studied.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 the slow fading channel,the expected rate of SWIPT-based QF cooperation is further analyzed.Finally,the theoretical analysis and simulation results show that the achievable rate or expected rate of SWIPT-based QF cooperation is obviously superior to that of traditional AF and DF 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.(2)The QF cooperative system with half-duplex dual-source single-relay based on SWIPT technology is studied.The SWIPT technology is added to the traditional half-duplex dual-source single-relay QF cooperation system,a SWIPT-based half-duplex dual-source single-relay QF cooperative system model is established.Then,the achievable rate of the SWIPT-based dual-source single-relay QF cooperative system is derived.For the slow fading channel,the expected sum rate of SWIPT-based dual-source single-relay QF cooperation is further analyzed.Through analysis of simulation results,it is shown that that the expected rate of SWIPT-based dual-source single-relay QF cooperation is obviously superior to that of traditional single-source single-relay QF cooperative system,and the system can achieve the expected rate performance similar to the traditional dualsource single-relay QF cooperative system under the high signal-to-noise ratio.(3)The QF cooperative system with full-duplex relaying based on SWIPT technology is studied.Firstly,a SWIPT-based full-duplex relay QF cooperative system model is established.Then,the achievable rate of the proposed system over the Additive White Gaussian Noise(AWGN)channels is derived.Meanwhile,for the power-splitting protocol,when the additive noise at the relay is ignored,the optimal power-splitting factor is solved,which further improves the system performance.Finally,the theoretical analysis and simulation results show that the achievable rate performance of the proposed system is obviously superior to the SWIPT-based full-duplex relay Decode-and-Forward(DF)cooperative system.In addition,it is also found that the system can achieve the achievable rate performance similar to the traditional full-duplex relay QF cooperative system under the high signalto-noise ratio,and it is more suitable for practical situations where energy is limited.