System Outage Performance Of SWIPT Enabled Two-Way Relay Networks With Residual Hardware Impairments

With the assistance of simultaneous wireless information and power transfer(SWIPT),two-way relay networks(TWRNs)can not only achieve the high-reliability communication,but also prolong the operation life of energy-constrained relay nodes.The existing works on the system outage performance of SWIPT based TWRNs have assumed ideal hardware at all nodes.In other word,the influence of various impairments on transceivers,such as phase noise,high power amplifier(HPA)nonlinearities and so on,is not considered.However,in practical communication system,all transceivers are inevitably affected by many factors.Although several sophisticated algorithms have been developed to mitigate the effects of RHIs,the residual hardware impairments(RHIs)remain and is detrimental for networks.Therefore,this thesis considers a EH based TWRN,and study the impact of RHIs on the system outage performance in terms of the system outage probability and diversity gain respectively.The main contributions are summarized below.For a SWIPT based TWRN with amplification-and-forward(AF)protocol,this thesis studies the impact of RHIs on the system outage performance.More specially,we obtain the closed-form for the system outage probability.Based the derived expression,we further identify two ceilings cased by RHIs,viz.,relay cooperation ceiling(RCC)and overall system ceiling(OSC).Specifically,when the data rate is larger than the RCC threshold,the AF relaying operation ceases;when the data rate goes beyond the OSC threshold that is larger than the RCC threshold,the system goes in outage.Moreover,we derive the achievable diversity gain of the considered network and results show that when the data rate is below the OSC threshold,the achievable diversity gain equals the shape parameter of the direct link;when the data rate exceeds the OSC threshold,the diversity gain is always zero.Specially,no matter what data rate is,the diversity gain from the relay link is always zero.This is due to the fact that the relay node with the AF protocol amplifies the useful signal and distortion noises concurrently.Finally,numerical simulations are provided to validate the above analysis.Compared with AF protocol,the decode-and-forward(DF)protocol has the advantage of eliminating noise accumulated at the relay node,and thus the distortion noise amplification can be avoid.Based on the above observations,we investigate the system outage performance of a SWIPT enabled two-way DF relay network.Firstly,we derive the system outage probability into a closed-form.Based the derived expression,we identify the OSC effect and obtain the achievable diversity gain of our studied network.Specifically,when data rate goes beyond the OSC threshold,the overall system is in outage and the diversity gain is zero;otherwise,both the direct and relaying links contribute to enhancing the system outage performance and the resulting diversity gain is the sum of the shape parameter of the direct link and the smaller shape parameter of two-hop relay links.Finally,numerical simulations validate the above analysis,and further compare the system outage performance of the AF and DF protocols.To sum up,for a SWIPT based TWRN,this thesis derives the system outage probability and diversity gain respectively,and reveals the influence of RHIs on the system outage performance.The research of this thesis can lay a solid foundation for the practical deployment of SWIPT based TWRNs.