Research On Physical Layer Security Methods Based On Cooperative Communication Technology

As is known to all,communication quality is generally measured in three aspects:effectiveness,which is measured by the communication capacity achieved under the same bandwidth conditions;reliability,which is refered to the bit error rate caused by unavoidable noise or interference;security,termed as the resistance to human-induced damage and threats during data transmission.With the era of big data,cyber security has become more and more important,and even to the extent that there is no national security without cyber security.Compared to closed wired communication systems,wireless networks are more vulnerable to security threats due to the openness of their media.Traditional information security relies on the upper layer data encryption technology,which not only requires a certain degree of computational complexity,but also requires a certain overhead in the high-level secure transmission method implemented by encryption.In this context,the study of physical layer security has gradually become a recent research topic.Physical layer security essentially utilizes the various specialities of the wireless channel to transform the original unfavorable factors into various favorable factors,and realize the secure transmission of information in physical layer.Compared with traditional encryption methods,physical layer security has many advantages,such as doesn't need highly complex algorithms and key exchange.This dissertation is inspired from the various practical factors faced by terminal user in wireless network,and uses cooperative communication means to solve the physical layer security problem under these factors.The dissertation mainly considers three factors,namely user mobility,user service characteristics and user terminal energy consumption.Following that,the dissertation proposes physical layer security enhancement methods based on cooperative communication under different conditions,and deeply analyzes the corresponding performance.The work of this dissertation has played a certain role in promoting the actual deployment of physical layer security.(l)To deal with user mobility,in order to ensure the security performance of users in different locations,such as cell center and cell overlap,this dissertation proposes the concept of "Seamless Security",which means security performance is ganrateed wherever the use is.To achieve this goal,the main idea is to use macro diversity,and propose a comnination of transmit antenna selection(TAS)and cooperative communication method.First,two base stations are equipped with multiple antennas.With antenna selection technology,each base station selects the antenna that can maximize the signal to noise ratio(SNR)of the legitimate receiver to transmit confidential information.Second,when the user moves between the two base stations,the two base stations cooperate with each other to dynamically adjust their transmission power,and the terminal receiver seeks the best security performance through a certain merging algorithm.The analysis shows that the proposed method can effectively guarantee the security performance of users in different locations of the cell.(2)In actual networks,user's traffic characteristics often follow certain distribution,such as Poisson distribution,which will inevitably affect the user's security strategy.This dissertation introduces a cooperation mechanism:when the user is idle,the channel resources are "rented" to the third party,so that the third party itself has the opportunity to transmit;in return,during liscenced user's transmission,the third party applies "friendly" interference,which only affects the receive quality of the eavesdropping user,thereby improving the security performance of legitimate users.To be more specific,this dissertation proposes a cooperative approach to physical layer security based on game theory.Firstly,the continuous time Markov chain is used to model the user's business model.Secondly,the utility functions of the primary user and the secondary user are designed.The secondary users can be used as friendly jamming nodes to improve the security performance of the primary user.In return,the primary user squeezes part of the spectrum for secondary users to transmit data.By solving the optimal strategy of game theory,it is concluded that the primary and secondary users can get higher benefits through cooperating with each other.(3)In order to pursue the security performance of the physical layer,and at the mean time,in order to minimize the power consumption of the terminal and thus achieve the goal of "green communication",this dissertation proposes an adaptive transmission strategy.In the two-hop multi-relay single eavesdropping system model,the source node and the destination node can perform relaying through the intermediate nodes.This dissertation proposes two transmission strategies,that is,only relay node(OR)transmission strategy and relay and jamming pair(RJP)transmission strategy.When a single relay node can satisfy the predetermined security performance,the OR transmission strategy is selected in order to save energy.When a single relay node cannot satisfy the predetermined security performance,the RJP transmission strategy selected.The system can adaptively switch between the two policies according to certain rules.Compared with the direct transmission method without intermediate node cooperation,the cooperative relay transmission method proposed in this dissertation can effectively reduce the total power consumption of the system while satisfying the security performance.