Research On Cooperative Jamming Technology Based On Space Power Synthesis

In recent years,the rapid development of wireless communication technology has promoted the progress of society and enriched people's lives,but the security of wireless network can not be ignored.Although encryption methods based on cryptography theory can guarantee information security to a certain extent,they often have large computational complexity,which causes them not suitable for "low end devices".And in the face of eavesdroppers with supercomputing power,these key encryption methods have also been challenged.Therefore,physical layer security methods that can be complemented with high-level encryption are gradually paid attention to.Different from high-level encryption,physical layer security makes full use of various characteristics of physical channels.It aims to achieve secure transmission at physical layer,providing a new solution for information network security protection.At present,physical layer security has obtained a lot of research results,but most of the research is done under the assumption that channel state information of eavesdroppers is known.It is obvious that the accurate channel state information of the eavesdropper is difficult to obtain due to the uncertainty of the channel.Especially when eavesdroppers are only in the case of passive eavesdropping,any information of eavesdroppers will not be obtained.Therefore,it is necessary to design security strategies of the physical layer without pre-known channel state information of eavesdroppers.In this thesis,a novel cooperative jamming strategy based on space power synthesis is investigated to resist eavesdroppers without channel state information,so as to achieve secure transmission.Specifically,the main research contents and innovations of this thesis are as follows:Firstly,this thesis provides a multi-jammer anti-eavesdropping model,and formulates the model through the multi-interference signal superposition theory.This thesis pioneers the use of the space power synthesis technology to introduce differential jamming,aiming at minimizing the synthetic power of jamming signals at a legitimate receiver,but still existing certain interference in other locations.Secondly,based on the multi-jammer anti-eavesdropping model,this thesis analyzes the power density at various places within a certain system area after the jamming signals are superimposed.According to the different positional relationship of multiple jammers,corresponding cooperative jamming strategies are proposed.Through the formula deduction and theoretical proof,these cooperative jamming strategies can achieve the synthetic power of multiple jamming signals is zero at a legitimate receiver,and not zero at other locations within the system.Therefore,in the case of unknown eavesdroppers' channel state information,these proposed cooperative jamming strategies can also guarantee the secure transmission of information.Thirdly,based on these cooperative jamming strategies,this thesis further proposes a power allocation scheme to maximize the worst-case secrecy rate of legitimate users.Due to the non-convex and nonlinearity of the power allocation optimization equation,this thesis divides it into two sub-optimization problems to find its optimal solution,and proposes a simulated annealing algorithm to solve them.In order to reduce the complexity of the algorithm,two kinds of search algorithms are proposed in this thesis.Finally,through the sequential optimization of the two sub-optimization problems,a feasible solution of the original problem can be found.