Research On Beamforming And Power Optimization In Secure Spatial Modulation Network

Spatial modulation(SM)is emerged as a low-cost,low power-efficiency and high performance communication technique.SM exploits both the index of activated antenna and amplitude phase modulation signal to transmit messages,which reduces the implementation complexity at the transmitter and receiver,and reduces the radio frequency cost.However,due to the broadcast characteristic of wireless transmission,confidential information might be eavesdropped by illegal receivers.Therefore,it is urgent to study the secure transmission technology of SM system.This paper focuses on the physical layer security of SM system with a full-duplex(FD)illegal receiver and that of intelligent reflecting surface aided SM system.The main contributions of this work can be listed as follows:(1)In a secure SM system with a FD malicious attacker owning eavesdropping capacity,where the FD eavesdropper transmit malicious jamming to interfere with the legitimate user while eavesdropping on private information,effective receive beamformers(RBFs)are crucial to eliminate jamming and improve the security performance of the system.Three highperformance RBFs design methods are proposed: maximizing receive power based on whitening-filter(Max-RP-WF),maximizing receive power with zero-forcing constraint(MaxRP-ZFC)and maximizing signal-to-jamming-plus-noise ratio(Max-SJNR).All proposed methods have closed-form expressions and can effectively suppress malicious interference.Simulation results show that three proposed methods harvest a substantial performance gain over conventional maximizing receive power method.Among them,Max-RP-WF almost achieves the same performance as Max-SJNR,and they perform better than the other algorithms in terms of the secrecy rate(SR)performance.(2)For the IRS-assisted SM system,effective design of beamforming at IRS and transmit power at transmitter plays an important role in improving security performance of the system.In consideration of the lack of closed expression for SR,the approximate secrecy rate based on cut-off rate(ASR-COR)is first derived,and the approximate secrecy rate of sum-of-multipleratio(ASR-SMR)is proposed.Then,taking ASR-SMR and ASR-COR as objective functions,two alternating iterative schemes for jointly designing IRS beamforming and transmit power at transmitter are proposed: Maximizing ASR-SMR(Max-ASR-SMR)and maximizing ASRCOR(Max-ASR-COR)solutions.Max-ASR-SMR scheme designs IRS beamforming and transmit power using semi-definite relaxation and quadratic transform respectively,and MaxASR-COR scheme designs IRS beamforming and transmit power using alternating direction method of multipliers and successive convex approximation method respectively.The simulation results show that the proposed ASR-SMR expression is closer to the accurate SR than the ASR-COR expression.At the same time,compared with the existing alternating iterative method,the proposed Max-ASR-SMR and Max-ASR-COR methods can significantly improve security performance of the IRS-aided SM system.Accordingly,the security performance of Max-ASR-SMR is higher than that of Max-ASR-COR method,but Max-ASRCOR significantly reduce the computational complexity.