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.

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.

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.

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.

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.

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。

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。

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.

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.

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.

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)。

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。

一种高效低成本小型无人机干扰器的设计

当前,小型无人机黑飞问题越来越严重。因此,分析了小型无人机的特点,总结对比目前探测、处置主要的技术手段,调研国内外产品,提出了一种高效低成本的干扰器设计,最后进行了试验验证。

基于多干扰机协同的极化SAR干扰方法

针对单极化干扰机生成的干扰会被极化合成孔径雷达(SAR)鉴别和对消的问题,本文提出了一种基于多干扰机协同的极化SAR干扰方法。该方法在不改变现有干扰机单极化发射结构的基础上,通过时序协同不同位置的多个单极化干扰机,实现对极化SAR的干扰。具体来说,根据极化SAR抗压制和欺骗干扰处理方式的不同,该方法利用不同位置的多个单极化干扰机同时发射,使极化SAR无法准确估计出干扰机发射天线极化比,从而无法对消压制干扰,实现压制干扰的目的;使用不同位置的多个单极化干扰机交替发射,有效破坏相邻两个接收脉冲之间的相关性,使极化SAR无法实现假目标对消,从而实现对极化SAR欺骗干扰的目的,并且多部单极化干扰机交替发射也能实现方位向间歇采样的干扰效果,增加欺骗干扰生成虚假目标的复杂性。由于实际应用中不需要改变现有单极化干扰机发射结构,该文所提方法为实现对极化SAR干扰带来了便利。并且该方法在生成压制和欺骗干扰时均使用模板调制干扰方式,通过简单的模板修改就能实现可控的压制和欺骗干扰效果。文中首先分析了极化SAR抗压制和欺骗干扰的方法,然后分别给出了多干扰机生成压制和欺骗干扰的时序协同方式,最后以模板调制干扰为基础具体分析了多干扰机协同生成干扰的方法,并分析了多干扰机的布局和干扰机数量选取准则。理论推导和仿真实验证明了本文方法能够实现对极化SAR的干扰。

基于时间调制阵列的共孔径干扰辅助短包隐蔽通信

该文首次研究了基于时间调制阵列(TMA)的共孔径干扰辅助短包隐蔽通信。首先提出并设计了共口径干扰的TMA架构,提出一种优化方法,能够在最大化目标方向信号增益的同时对非目标方向形成干扰。基于上述模型,推导出隐蔽性约束和隐蔽吞吐量的闭合表达式。在此基础上,该文进一步对发送功率和数据包长进行联合优化,以最大化隐蔽吞吐量。仿真结果表明,存在一个使隐蔽吞吐量最大化的最优包长,所提方案相比基准方案实现了更好的隐蔽通信性能。

基于非脉冲矢量网络分析仪的非反向交叉眼干扰实验设计与分析

交叉眼技术是对抗单脉冲雷达最有效的方式之一。针对交叉眼干扰多侧重于仿真建模、实验设计及实施复杂等特点,基于交叉眼干扰原理、单脉冲测角原理和矢量网络分析仪幅相精确测量等特性,设计了基于喇叭天线、微带天线、幅相调节器和非脉冲矢量网络分析仪组成的非反向交叉眼干扰实验系统。在微波暗室环境下,先后开展了基于矢量网络分析仪的测角实验和非反向交叉眼干扰实验,并通过建立干扰天线相位中心电磁仿真模型,对误差展开了分析。实验和仿真结果表明:交叉眼干扰下实验测量的角度值与理论角度值随相位差变化趋势一致,其理论最大角度值与实际最大角度值误差不超过2°,对应的交叉眼增益误差小于0.5;基于矢量网络分析仪设计的非反向交叉眼实验系统可行,可模拟非反向交叉眼干扰对被动单脉冲雷达干扰,亦可部分模拟反向交叉眼干扰应用场景,为交叉眼干扰机设计和测试提供一定的指导。