Research On Jammer Power Allocation Strategy For Proactive Eavesdropping System

Due to the nature of broadcast transmission of signals under wireless communication,wireless communication cannot avoid the eavesdropping of potential eavesdroppers.The use of wireless channel commonality among communication users to implement the wireless communication information security technology in the security mode is collectively referred to as physical layer security.At present,a large number of defense mechanisms have been studied by the academic community for this communication security issue.Although the traditional cryptography mechanism also provides an effective management method for information security communications,in recent years,as the number of illegal eavesdroppers has increased,traditional password mechanism is facing unprecedented challenges to maintain the current security status.In the existing research on eavesdropping technology,most of the work is devoted to optimizing the system's security capacity,so as to prevent effective information from being intercepted by eavesdroppers in an illegal manner.However,from another perspective,from a broader perspective of national security,an eavesdropper may actually be in an proactive listening mode.When eavesdropping failed,interferes with the destination user to receive suspicious transmission signals.This is collectively referred as proactive eavesdropping.Actually using legitimate monitoring technology to intercept communication between illegal users is very challenging because legitimate listeners may be far away from suspicious transmitters;wireless channels will also attenuate severely over time.Therefore,in the long-distance communication mode,it is considered to add several relays to overcome the signal distortion caused by long-distance communication and ensure the integrity of the received signal.From the current research status of proactive eavesdropping technologies,most of the considerations are the application of legal eavesdroppers to integrate interference technologies,and consider the scenario of using jammer devices alone;and under the relay system,only the consideration is that eavesdropper switches to the interference mode to transmit the interference signal to the suspicious relay or receiver in a single time slot,preventing the occurrence of suspicious communication.Therefore,aiming atthe above two points,this paper proposes a strategy of proactive eavesdropping based on jammers,and considers point-to-point suspicious wireless communication links through a legitimate monitor in long-distance and near-distance application scenarios.According to the eavesdropping decision condition,when the suspicious link channel gain is greater than the eavesdropping link channel gain,the suspicious receiver is blocked by the jammer to prevent the suspicious signal from being transmitted.For the eavesdropping decision condition,the jammer uses the adaptive power adjustment strategy to adjust the interference power to the optimal value in the current situation and maximize the legal eavesdropping rate of the active eavesdropping system.The following are interference power optimization strategies in two scenarios:1 ? Near-field communication scenario: in the fading channel,when the eavesdropping rate is greater than the suspect communication rate,the legitimate eavesdropper can successfully decode and eavesdrop on the suspicious communication link.On the other hand,through the adaptive power allocation principles of jamming,the purpose is to change the suspicious user communication rate(for example,for smaller data transfer rate),improving the eavesdropping performance of the system.The legal eavesdropper can be eliminated self-interference by the advanced technology or eavesdroppers themselves can also be affected by interference machine.The main focus is on the legal wiretap rate,respectively,by using interior-point method and Lagrangian optimization method to optimize the transmission power of the jamming machine,in order to improve the lawful interception rate of the system.2?Telecommunication scenario: A novel lawful interception strategy is proposed for the double-hop decode and forward(DF)relay eavesdropping system.The relay passes the time-division strategy and monitors suspicious source transmission signal in the first transmission time slot,and in the second slot time through the amplification and forwarding technology to send signals to the suspect receiver.The specific strategy proposed in this paper is designed for lawful listeners and the interference equipment.According to the channel state in two slot time,it is determined whether the eavesdropping is successful in the current time slot.If it is determined that the eavesdropper fails to eavesdrop in the current time slot,the interference equipment isused to interference relays and receivers to receive signals,for the interference power adjustment strategy,given the current optimal interference power under the time slot to maximize the system's eavesdropping performance.