Research On Cooperative Jamming Technology In Relaying System

In the field of information security,the classic cryptographic mechanism uses encryption algorithms to encrypt data at the upper layer of the network protocol,which can ensure the secure transmission of information to a certain degree,but it also has certain limitations.For example,the management and update of the key will increase the overhead,and with the continuous enhancement of the computing power of the equipment,the key encryption algorithm becomes more and more difficult to ensure the security of the system.Therefore,as a security supplementary strategy to the classic cryptographic mechanism,the physical layer security technology ensures the secure transmission of the wireless communication system by increasing the difference between the main channel and the eavesdropping channel,which has attracted the attention of researchers.As a key component of physical layer security technology,the cooperative jamming technology introduces artificial noise to worsen the eavesdropping channel while not affecting the performance of legitimate users as much as possible,thereby improving the security performance of the communication system.Therefore,this thesis focuses on the research of cooperative jamming technology in the relay system.The main work is as follows:Firstly,this thesis introduces the research background and research status of physical layer security technology,and then briefly describes related knowledge of physical layer security technology,and introduces important indicators used to measure system performance such as system outage probability and interception probability.Then the forwarding protocols commonly used by relay nodes are analyzed and compared,and finally,the cooperative jamming technology is emphasized.The above content laid the theoretical foundation for the follow-up research.Secondly,the cooperative jamming technology under the Decode-and-Forward(DF)relay system is studied.Aiming at the cooperative jamming model of multiple relays and multiple antennas in the source node single-antenna scenario,a joint relay and jammer selection strategy is proposed.The strategy jointly selects the relay node and the transmitting antenna at the relay to maximize the channel gain of legitimate users,and interfering node sends artificial noise,deteriorates the receiving performance of the eavesdropper,and effectively improves the safety and reliability of the system.Under the Rayleigh fading channel,the closed expressions of the system outage probability and the intercept probability when using this strategy are respectively derived.Through software simulation analysis,the relationship between outage probability,intercept probability and system signal-to-noise ratio is explored,and compared with different schemes,the effectiveness of joint relay and jammer selection strategy is verified.Since the use of a multi-antenna network can effectively improve the system diversity gain,on the basis of this model,the source node single antenna is extended to multiple antennas to study the security performance of the system in complex communication scenarios.Aiming at the cooperative jamming model in the scenario of multi-antenna source and multi-relay multi-antenna,a joint relay and antenna selection strategy is proposed.By using this strategy to improve the safety and reliability of the system,and to derive the closed expressions of the system outage probability and intercept probability.Finally,simulations verify the correctness of the theoretical analysis and the effectiveness of the joint relay and antenna selection strategy.Finally,this thesis further studies the cooperative jamming technology based on Amplifyand-Forward(AF)relay system.Aiming at the multi-relay multi-antenna cooperative jamming model in the source node multi-antenna scenario,a joint two-stage channel relay and antenna selection strategy is proposed based on the criterion of minimizing the system outage probability.The thesis analyzes the safety and reliability of the selection strategy,and then validates the effectiveness and superiority of the strategy in improving system performance through simulation analysis.At the same time,the two different situations of using the AF protocol and the DF protocol in the relay system under the same scenario are analyzed and compared.In the source node multi-antenna,multi-relay multi-antenna scenario,the security performance of the DF selection scheme is slightly better than that of the AF selection scheme.However,the performance of the DF selection scheme is improved at the cost of complexity,while the AF protocol does not require signal decoding,the process and implementation are relatively simple,and the complexity is low.Therefore,the AF and DF methods have their own advantages and disadvantages,and they can be selected according to different focuses in practical applications.