Research On An Intermittent Cooperative Jamming Scheme For A Non-slotted Scenario

In scenarios of massive machine-type communications(m MTC)and smart transportation,terminals communicate with each other through a wireless channel.Unfortunately,the broadcast nature of wireless communications may threaten legitimate signal transmission between terminals in these scenarios.One of the main threats is signal eavesdropping.Cooperative jamming based physical layer security is an effective method to against eavesdropping,which consists of continuous jamming strategy(CJS)and intermittent jamming strategy(IJS).CJS used to be a primary physical layer security technology,which sends artificial noise(AN)as cooperative jamming signals to guarantee the security of legitimate signals.However,Internet of things(Io T)devices are generally energy constrained.Therefore,these devices can not support the excessive energy consumption of sending jamming signals with CJS scheme.To solve these problems,energy efficiency of IJS and the security in non-slotted scenarios has been studied in this paper,and listed as follows.(1)Firstly,we study the existing cooperative jamming schemes and make a comparison of the energy efficiency of these schemes.Conventional designs of secure communication with energy constraints focus on two methods.The first one focuses rationally utilizing the limited energy,while the second one aims to harvest energy from wireless environment so as to support the energy consumption.Intelligent reflecting surface(IRS),IJS and optimal jammer selection improves the energy efficiency in channel selection,reduces energy consumption and reduces jamming loss respectively.It’s necessary to point out that IJS is able to increase the energy efficiency while guaranteeing the security directly compared to CJS.(2)Secondly,we study the security performance of IJS while taking the security degradation of legitimate receiver caused by jamming signals into consideration.We solve the maximization problem of BER gap(BG)between legitimate receiver and eavesdropper under a jamming constrained scenario.Then,we discuss the existence of optimal jamming duration proportion(JDP)under different channel coefficients.The simulation results show that optimal JDP is available in specific channel conditions.(3)Finally,we solve the synchronization problem between legitimate signals and jamming signals in non-slotted scenarios.We construct a jamming precision maximization problem of IJS by optimizing the mode durations of the cooperate jammer with a sense-jam-harvest mode.By obtaining the statistically JDP that satisfies both security requirements and energy constraints,IJS is able to ensure system security and improving energy efficiency in non-slotted scenarios.The simulation results show that the proposed strategy can ensure safety in non-slotted scenarios and can significantly improve the working time of the cooperative jammer.This thesis consists of 5 chapters,including 27 figures,6 tables and 89 references.