Cognitive Jammers Assisted Covert Communication in Cognitive Radio Networks

In this work,we investigate the covert communication in cognitive radio(CR)networks with the existence of multiple cognitive jammers(CJs).Specifically,the secondary transmitter(ST)helps the primary transmitter(PT)to relay information to primary receiver(PR),as a reward,the ST can use PT's spectrum to transmit private information against the eavesdropper(Eve)under the help of one selected cognitive jammer(CJ).Meanwhile,we propose three jammer-selection schemes,namely,link-oriented jammer selection(LJS),min-max jammer selection(MMJS)and random jammer selection(RJS).For each scheme,we analyze the average covert throughput(ACT)and covert outage probability(COP).Our simulation results show that CJ is helpful to ST's covert communication,the expected minimum detection error probability and ACT can be significantly improved with the increase of false alarm of CJ.Moreover,the LJS scheme achieves best performance in ACT and COP,followed by RJS scheme,and MMJS scheme shows the worst performance.

Multi-Antenna Jammer Assisted Covert Communications in Data Collected IoT with NOMA

In this paper,we investigate covert communications in data collected IoT with NOMA,where the paired sensor nodes S_(m) and S_(n) transmit covert messages to a legitimate receiver(Bob)in the presence of a Warden(Willie).To confuse the detection at Willie,an extra multi-antenna friendly jammer(Jammer)has been employed to transmit artificial noise(AN)with random power.Based on the CSI of Willie is available or not at Jammer,three AN transmission schemes,including null-space artificial noise(NAN),transmit antenna selection(TAS),and zeroforcing beamforming(ZFB),are proposed.Furthermore,the closed-form expressions of expected minimum detection error probability(EMDEP)and joint connection outage probability(JCOP)are derived to measure covertness and reliability,respectively.Finally,the maximum effective covert rate(ECR)is obtained with a given covertness constraint.The numerical results show that ZFB scheme has the best maximum ECR in the case of the number of antennas satisfies N>2,and the same maximum ECR can be achieved in ZFB and NAN schemes with N=2.Moreover,TAS scheme also can improve the maximum ECR compared with the benchmark scheme(i.e.,signal-antenna jammer).In addition,a proper NOMA node pairing can further improve the maximum ECR.

A Coincered Node Based Localization of Jammers in Wireless Sensor Networks

Jammers can awfully interfere with the wireless communications. The transmission and reception of wireless communication is blocked by the jammer. The intruder will place the jammer in a well topological network area and they can easily track the information. It will help them to block the signal transmission and reception. Now, the intention is to track the position of the jammer where it is fixed. The existing methods rely on the indirect measurements and the boundary node to find the jammer’s position which degrades the accuracy of the localization. To improve the efficiency, this paper proposed an efficient method namely Coincered Node Based Localization of jammers to find the position of the jammer with high level of accuracy. The proposed system uses the direct measurements, which is the jammer signal strength. The effectiveness can also be increased by using the coincered node that will stumble across the true position of the jammer. The proposed work is compared with existing methods. Then the proposed mechanism proves better to find the jammer location. The simulation results estimate that the accuracy of the localization achieves better performance than the existing schemes.

Mobile Jammer-Aided Secure UAV Communications via Trajectory Design and Power Control

To further promote the achievable average secrecy rate for UAV-ground communications, a UAV-aided mobile jamming strategy was proposed in this paper. Specifically, an additional cooperative UAV is employed as a mobile jammer to transmit the jamming signal to help keep the source UAV closer to the ground destination, thus establishing more favorable legitimate link and enhancing the secrecy performance. We aimed to maximize the achievable secrecy rate by jointly optimizing the trajectories and transmit power of both source UAV and jammer UAV. To solve the considered non-convex optimization problem, we presented a block coordinate descent based iterative algorithm to address a sequence of approximated convex problems for the optimized parameter block by block to find a local optimal solution. Numerical results verify that the proposed algorithm can achieve significant secrecy rate gain compared to all the benchmark schemes.

Put Others Before Itself:A Multi-Leader One-Follower Anti-Jamming Stackelberg Game Against Tracking Jammer

This paper mainly investigates the coordinated anti-jamming channel access problems in multiuser scenarios where there exists a tracking jammer who senses the spectrum and traces the channel with maximal receiving power.To cope with the challenges brought by the tracking jammer,a multi-leader onefollower anti-jamming Stackelberg(MOAS)game is formulated,which is able to model the complex interactions between users and the tracking jammer.In the proposed game,users act as leaders,chose their channel access strategies and transmit firstly.The tracking jammer acts as the follower,whose objective is to find the optimal jamming strategy at each time slot.Besides,the existence of Stackelberg equilibriums(SEs)is proved,which means users reach Nash Equilibriums(NEs)for each jamming strategy while the jammer finds its best response jamming strategy for the current network access case.An active attraction based anti-jamming channel access(3ACA)algorithm is designed to reach SEs,where jammed users keep their channel access strategies unchanged to create access chances for other users.To enhance the fairness of the system,users will adjust their strategies and relearn after certain time slots to provide access chances for those users who sacrifice themselves to attract the tracking jammer.

Effects of long-term exposure to radiofrequency radiations emitted by mobile Jammers on reproduction parameters in rats

Objective:To evaluate the effect of long-term exposure to radiofrequency radiations emitted from mobile jammers onrat's reproductive parameters.Methods: Eighty male rats were divided into neonatal group (n=20), immature group (n=30) and mature group (n=30). Neonatal rats were randomly divided into two subgroups. Immature and mature rats were randomly divided into three subgroups. Experimental rats were fixed in the restraining tube and were exposed to radiofrequency radiations emitted from mobile jammers at a distance of 100 cm, for 30 d (7 h/d). Sham group rats were also fixed in restraining tube but without radiations. The control group was allowed to move freely without being exposed to radiation. At the end of the experiment, weight of testes, sperm quality, histological testicular sections and serum testosterone levels were evaluated.Results: Long-term exposure to radiofrequency from mobile jammers could adversely affect neonatal rat fertility, but it did not have significant effects on male mature and immature rat's reproduction parameters. However, restraint stress induced by immobilizing them for a long-period could adversely affect male mature rat's reproductive parameters, but it had no significant effect on male immature rat's reproduction parameters.Conclusion:The effects of EMF exposure to be various based on the life stage.

Lightweight jammer localization algorithm in wireless sensor networks

In wireless sensor networks （WSNs）, as the shared nature of the wireless medium, jam- ming attacks can be easily launched and result in a great damage to the network. How to deal with jamming attacks has become a great concern recently. Finding the location of a jammer is important to take security actions against the jammer, and thus to restore the network communication. After a comprehensive study on the jammer localization problem, a lightweight easy-operated algorithm called triple circles localization （TCL） is proposed. The evaluation results have demonstrated that, compared with other approaches, TCL achieves the best jammer localization accuracy under variable conditions.

Enhanced Intrusion Detection System for an EH IoT Architecture Using a Cooperative UAV Relay and Friendly UAV Jammer

In this paper,the detection capabilities and system performance of an energy harvesting(EH)Internet of Things(Io T)architecture in the presence of an unmanned aerial vehicle(UAV)eavesdropper(UE)are investigated.The communication protocol is divided into two phases.In the first phase,a UAV relay(UR)cooperates with a friendly UAV jammer(UJ)to detect the UE,and the UR and UJ harvest energy from a power beacon(PB).In the second phase,a ground base station(GBS)sends a confidential signal to the UR using non-orthogonal multiple access(NOMA);the UR then uses its harvested energy to forward this confidential signal to IoT destinations(IDs)using the decode-and-forward(DF)technique.Simultaneously,the UJ uses its harvested energy to emit an artificial signal to combat the detected UE.A closed-form expression for the probability of detecting the UE(the detection probability,DP)is derived to analyze the detection performance.Furthermore,the intercept probability(IP)and throughput of the considered IoT architecture are determined.Accordingly,we identify the optimal altitudes for the UR and UJ to enhance the system and secrecy performance.Monte Carlo simulations are employed to verify our approach.

Energy-Efficient Jammer Selection Approach for QoS Provisioning in Distributed Wireless Cooperative Networks

Abstract：Aiming at achieving better Quality of Service （QoS） provisioning in distributed wireless cooperative networks, a novel energy efficient jammer selection approach is proposed in this pa per. We employ Secrecy Capacity （SC） to charac terize the security of transmission. In order to ac curately describe the timevarying characteristic, related channels are modeled as FiniteState M ark ov Channels （FSMCs）. The remaining energy of candidate node is considered in a similar way.

安捷伦科技推出业界首款具有在线误码注入功能的PCI EXPRESS Jammer

2009年2月9日，安捷伦科技公司（NYSE：A）日前宣布推出在线误码注入工具（Jammer），用于进行PCI EXPRESS （PCIe）协议测试。Jammer采用了突破性的PCIe测试理念，是一种创新的测试工具，可帮助开发人员缩短测试周期和加快器件的上市速度。

Localizing Jammer in an Indoor Environment by Estimating Signal Strength and Kalman Filter

Localizing a jammer in an indoor environment in wireless sensor networks becomes a significant research problem due to the ease of blocking the communication between legitimate nodes. An adversary may emit radio frequency to prevent the transmission between nodes. In this paper, we propose detecting the position of the jammer indoor by using the received signal strength and Kalman filter (KF) to reduce the noise due to the multipath signal caused by obstacles in the indoor environment. We compare our work to the Linear Prediction Algorithm (LP) and Centroid Localization Algorithm (CL). We observed that the Kalman filter has better results when estimating the distance compared to other algorithms.

电脑音乐DIY系列之三:电脑自动作曲软件Jammer

在我们周围有许多朋友非常喜欢音乐,头脑中时常有一些从不曾听过的音乐飘过,只可惜自己的音乐基础知识太少,无法把这些飘过脑际的美妙音乐记录下来,使它成为一首音乐作品,这点实在令人感到遗憾。先别着急,这里给大家介绍一个能够自动生成音乐的软件——Jammer。你无须学习任何枯燥的音乐理论,只要对音乐有感觉、有鉴赏力。

A Novel Range-Free Jammer Localization Solution in Wireless Network by Using PSO Algorithm

In wireless networks, jamming attacks are easy to launch and can significantly impact the network performance. The technique which localizes the jamming attacker is useful to address this problem. Some range-based localization schemes depend on the additional hardware of wireless nodes too much, and they can not work in resource-constrained wireless networks. Solutions in range-free localization are being pursued as a cost-effective alternative to more expensive range-based approaches.In this paper, we propose a novel range-free algorithm to localize the source of the attacker. We show that our approach only relies on the positions of each jammed or no-jammed node in the network, PSO algorithm is used to get the minimum covering circle of jammed positions and the circle center is the estimated jammer location. We compare our work with some existing range-free solutions via extensive simulations in two models, which are wireless sensor network (WSN) and vehicular ad hoc network (VANET) respectively. The experimental results suggest that our proposed algorithm achieves higher accuracy than the other solutions, and the localization error goes down with larger number of recorded jammed positions. In additional, when the recorded jammed positions are distributed in a specific constrained area, the localization error goes higher, we also propose an improved PSO algorithm to deal with this issue.

Topology-based multi-jammer localization in wireless networks

Jamming attacks and unintentional radio interference are some of the most urgent threats harming the dependability of wireless communication and endangering the successful deployment of pervasive applications built on top of wireless networks.Unlike the traditional approaches focusing on developing jamming defense techniques without considering the location of jammers,we take a different viewpoint that the jammers'position should be identified and exploited for building a wide range of defense strategies to alleviate jamming.In this paper,we address the problem of localizing multiple jamming attackers coexisting in wireless networks by leveraging the network topology changes caused by jamming.We systematically analyze the jamming effects and develop a framework that can partition network topology into clusters and can successfully estimate the positions of multiple jammers even when their jamming areas are overlapping.Our experiments on a multi-hop network setup using MicaZ sensor nodes validate the feasibility of real-time collection of network topology changes under jamming and our extensive simulation results demonstrate that our approach is highly effective in localizing multiple attackers with or without the prior knowledge of the order that the jammers are turned on.

UltraJam:Ultrasonic adaptive jammer based on nonlinearity effect of microphone circuits

The widely used devices(e.g.smartphones,recorders)equipped with microphones have posed a severe threat to confidential conversations.In this paper,we design an inaudible anti-eavesdropping method:UltraJam,to reduce the risk of unwanted and secret recordings.UltraJam uses the ultrasonic signal to mask conversation.By leveraging the nonlinear effect of microphone circuits,the adaptive ultrasonic signal can be recorded and demodulated into low-frequency which can effectively squash the sound.Based on the characteristics of the attenuation coefficient and frequency response,we construct a number of jamming signals with different bandwidths and designed a wideband signal injection array,meanwhile adaptively adjust the power at each bandwidth signal to cover more frequency bands and increase usage scenarios.To verify the security of the microphone jamming system,we also utilize several audio recovery methods to recover the raw signal from jamming noise.The experimental results show that less than 1% of the words are recognized in the jamming recording,and even with the audio recovery method,99% of the words still cannot be recognized in the recovered jamming recording.

基于威胁机制-双重深度Q网络的多功能雷达认知干扰决策

针对传统深度Q网络(deep Q network,DQN)在雷达认知干扰决策中容易产生经验遗忘,从而重复执行错误决策的问题,本文提出了一种基于威胁机制双重深度Q网络(threat warning mechanism-double DQN,TW-DDQN)的认知干扰决策方法,该机制包含威胁网络和经验回放2种机制。为了验证算法的有效性,在考虑多功能雷达(multifunctional radar,MFR)工作状态与干扰样式之间的关联性的前提下,搭建了基于认知电子战的仿真环境,分析了雷达与干扰机之间的对抗博弈过程,并且在使用TW-DDQN进行训练的过程中,讨论了威胁半径与威胁步长参数的不同对训练过程的影响。仿真实验结果表明,干扰机通过自主学习成功与雷达进行了长时间的博弈,有80%的概率成功突防,训练效果明显优于传统DQN和优先经验回放DDQN(prioritized experience replay-DDQN,PER-DDQN)。

Security-Reliability Tradeoff Analysis for Jamming Aided Decode-and-Forward Relay Networks

In this paper,we explore a cooperative decode-and-forward(DF)relay network comprised of a source,a relay,and a destination in the presence of an eavesdropper.To improve physical-layer security of the relay system,we propose a jamming aided decodeand-forward relay(JDFR)scheme combining the use of artificial noise and DF relaying which requires two stages to transmit a packet.Specifically,in stage one,the source sends confidential message to the relay while the destination acts as a friendly jammer and transmits artificial noise to confound the eavesdropper.In stage two,the relay forwards its re-encoded message to the destination while the source emits artificial noise to confuse the eavesdropper.In addition,we analyze the security-reliability tradeoff(SRT)performance of the proposed JDFR scheme,where security and reliability are evaluated by deriving intercept probability(IP)and outage probability(OP),respectively.For the purpose of comparison,SRT of the traditional decode-and-forward relay(TDFR)scheme is also analyzed.Numerical results show that the SRT performance of the proposed JDFR scheme is better than that of the TDFR scheme.Also,it is shown that for the JDFR scheme,a better SRT performance can be obtained by the optimal power allocation(OPA)between the friendly jammer and user.

Covert LEO Satellite Communication Aided by Generative Adversarial Network Based Cooperative UAV Jamming

In this paper,we study the covert performance of the downlink low earth orbit(LEO)satellite communication,where the unmanned aerial vehicle(UAV)is employed as a cooperative jammer.To maximize the covert rate of the LEO satellite transmission,a multi-objective problem is formulated to jointly optimize the UAV’s jamming power and trajectory.For practical consideration,we assume that the UAV can only have partial environmental information,and can’t know the detection threshold and exact location of the eavesdropper on the ground.To solve the multiobjective problem,we propose the data-driven generative adversarial network(DD-GAN)based method to optimize the power and trajectory of the UAV,in which the sample data is collected by using genetic algorithm(GA).Simulation results show that the jamming solution of UAV generated by DD-GAN can achieve an effective trade-off between covert rate and probability of detection errors when only limited prior information is obtained.

空频抗干扰对GNSS载波相位测量的影响

对于全球导航卫星系统(GNSS)的抗干扰,最有效的是采用自适应天线阵技术,但这种抗干扰处理会引入与信号入射方向相关的载波相位测量偏差,限制了其在高精确度测量领域的应用。为减小抗干扰处理的偏差,引入测量偏差及其分析方法,建立仿真模型,并搭建软件接收机进行实验。结果表明,在不增加额外约束的条件下,采用空频最小方差无畸变响应算法实现空频抗干扰处理器,不会引入载波相位测量偏差,非常适用于对抗干扰性能和测量精确度均有苛刻要求的场合。