Nakagami衰落信道下噪声跟踪干扰检测性能分析

针对慢跳频通信中噪声跟踪干扰的检测问题,提出了一种新的噪声跟踪干扰检测算法.该检测算法应用认知无线电中协作频谱感知方法,分析了接收信号的条件概率密度函数,研究了加性高斯白噪声信道下单跳信号存在干扰的检测性能.在此基础上,推导了Nakagami衰落信道下单跳信号存在干扰的检测概率和虚警概率,通过对检测概率和虚警概率中的多重积分进行化简,得到了检测概率和虚警概率的级数表达式.单跳信号检测后,把检测结果上报到融合中心,应用协作频谱感知中的“k out of n”准则分析了噪声跟踪干扰的检测性能.仿真结果验证了理论分析的正确性.     

无线通信中跟踪干扰信号检测方法及检测性能

根据跟踪干扰随通信信号变频的特征,提出一种检测跟踪干扰的方法。该方法对空闲信道采用能量检测法进行检测,对通信信道采用在信号中插入训练序列进行检测,根据干扰是否连续多次伴随信号出现、消失来判断系统是否受到跟踪干扰,并推导出该方法在加性高斯白噪声(AWGN)信道条件下的检测概率。通过对该方法进行计算机仿真,计算出不同仿真条件下的检测概率,验证了该方法的正确性和有效性。理论分析和仿真结果表明,信道改变次数越多,检测结果的可信度越高,但检测概率越低;在低信干比条件下,仿真检测概率与理论值较为符合,在高信干比条件下,检测性能受信道噪声影响较大。     

最小能量框架的跟踪干扰识别和去噪算法

讨论了基于离散信号空间上的最小能量（小波）框架的跟踪干扰信号识别和去噪算法。利用一组框架对采用相位调制的接收信号进行分解,如果受到跟踪干扰,则未干扰区信号和干扰区信号的3个分解子信号将呈现明显不同的能量分布特征,据此提出了一种跟踪干扰信号识别和自适应阈值去噪算法。理论分析和仿真结果表明,识别算法具备低虚警率和漏警率性能,而去噪算法有效抑制了干扰信号能量,10-2 误包率时,BPSK+1/2 Turbo信号中1/16尾部信号受到干信比值10 dB的高斯噪声干扰后,去噪算法获得了约4 dB的增益;而QPSK+1/2 Turbo信号中1/8尾部信号受到干信比值10 dB的高斯噪声干扰后,去噪算法可以把误包率性能从1降低至约0.67的水平。     

一种基于随机共振的GNSS干扰检测算法

针对低干噪比下全球导航卫星系统干扰检测问题,文中利用非线性随机共振系统对微弱信号的增强作用,提出一种基于随机共振的GNSS干扰检测算法,并详细阐述了算法的实现过程,以传统能量检测算法为对比算法,分析两种算法在相同条件下检测性能的差异。仿真表明:在高斯白噪声信道、低干噪比条件下,所提算法的检测性能明显优于传统能量检测算法。相同信道环境及检测概率下,所提算法需要的数据长度更短,检测耗费时长更少,且能保证更低的虚警概率。     

基于Stackelberg模型的弹载雷达和干扰波形设计

现代电子战中,弹载雷达与干扰机间存在着二元零和动态博弈。针对博弈条件下弹载雷达和干扰机性能降低问题,分别以雷达和干扰为博弈主导者,建立Stackelberg博弈模型,基于信干噪比准则提出了二次注水的波形设计方法。在雷达主导的博弈模型中,干扰通过min策略最小化雷达接收端信干噪比,雷达通过二次注水的maxmin策略分配信号频域功率,降低干扰影响;在干扰主导的博弈中,雷达通过max策略最大化自身信干噪比,干扰机利用minmax策略提高干扰效能。实验仿真表明,maxmin策略中雷达检测性能较min策略最高提升9.17%,而minmax策略中目标被探测概率较max策略最多降低11.42%;为博弈条件下雷达信号和干扰信号的优化分别提供了解决方案。      

干扰背景下MIMO雷达部分相关信号设计

在干扰背景下,集中式MIMO雷达可以通过设计发射波形提高系统的输出信干噪比,然而优化后的波形通常会具有较高的自相关旁瓣,降低了接收机对弱目标的检测性能。该文提出一种干扰背景下MIMO雷达部分相关信号设计方法。该方法在兼顾发射信号峰均比(PAPR)的同时,在发射天线对正交恒模波形进行加权处理,并以最大化接收机系统的输出信干噪比为准则建立目标函数,给出一种基于拟牛顿法的连续优化算法求解目标函数,获得最优加权,使得系统的输出信干噪比得到提升。仿真结果表明,该方法能够有效地抑制干扰,并可自适应地将发射信号能量辐射向目标方向,提高系统输出信干噪比。     

一种应用于车地无线通信系统的干扰检测方法

城市轨道交通的车地无线通信,正处在一个日益复杂的电磁环境中.文中提出了一种针对城市轨道交通车地无线通信系统的干扰检测算法.该算法采用频域能量检测的方法,通过设置自适应门限对车地无线通信进行干扰的有无检测和频率参数估计.针对经典干扰频率估计方法在低干信比或频谱峰值偏离干扰中心频率,估计误差较大的问题提出了一种改进方法.计算机仿真结果表明:当信号数据速率为5.5 MSPS且干信比达到-7 dB以上时,干扰检测概率接近于100％;当信号数据速率为11 MSPS且干信比达到-8 dB以上时,干扰检测概率接近于100％.提出的改进频率估计算法,随着干扰信号比的提高,频率估计误差呈现单调减小趋势,在干信比大于10dB时,其性能优于经典算法.     

噪声干扰背景下压缩感知雷达波形优化设计

为改善压缩感知雷达（Compressive Sensing Radar,CSR）在干扰噪声背景下目标检测及距离-多普勒参数的估计性能,该文提出一种感知矩阵平均相干系数（Averaged Coherence of the Sensing Matrix,ACSM）与信干噪比（Signal to Interference and Noise Ratio,SINR）联合优化的波形设计方法.文中首先建立了CSR距离-多普勒二维参数感知模型,推导了波形联合优化设计的目标函数,其次以多相编码信号作为优化码型并采用模拟退火（Simulated Annealing,SA）算法对目标函数进行优化求解.与传统CSR波形相比,优化设计的波形提高了CSR在低信干噪比条件下的成功检测概率,同时有效降低了目标距离-多普勒参数估计误差,由此改善了CSR在干扰噪声背景下的距离-多普勒成像质量.计算机仿真验证了该方法的有效性.     

基于RD和CS算法的SAR噪声干扰效果评估与对比

该文针对RD与CS两种成像算法的差异,首先分析了两种算法在压制性噪声干扰环境下信号与噪声干扰的成像处理增益,推导出两种算法的信号-干扰功率比(信干比)处理增益公式并进行了分析。理论分析结果表明,在采样率仅略大于信号带宽条件下,RD和CS成像算法的信干比处理增益基本一致;在过采样条件下,RD算法由于两维匹配处理从而获得比CS算法大的信干比处理增益,但如果对过采样信号进行滤波处理后,CS算法的信干比处理增益与RD算法一致。最后,采用对计算机仿真数据和真实数据进行处理的方法验证了该文的理论分析和结论。     

LMS算法输出信干噪比数学模型及仿真

通过对LMS算法的分析及运用矩阵理论,得出了LMS算法波束形成干扰数学模型,并假设信号与干扰互不相关时,得出了输出信干噪比数学模型。在此基础上,进一步分析了算法在无干扰信号时(只有噪声)的抗噪性能,在有干扰时得出了干扰较小和较大时,算法对干扰起的作用是完全不同的这一结论。通过数学仿真验证了仿真结果与理论分析的一致性。     

存在检测误差的抗跟踪干扰最优跳速设计

跟踪干扰对跳频通信构成严重威胁。首先采用Stackelberg博弈模型对存在检测误差条件下的通信干扰与抗干扰进行建模,在该模型中,存在一个先行者和一个跟随者,其中,通信方作为先行者进行跳频通信,跟踪干扰方作为跟随者检测跳频通信信号并实施干扰。分别推导了通信方的最优跳速,以及干扰方最优检测时间与干扰时间的分配策略,证明了当信噪比小于一定门限时,干扰方的最优干扰策略是盲干扰,通信方的最优抗干扰策略是慢速跳频。最后,对理论分析结果进行了计算机仿真验证,并将所提算法与盲跳频和变速跳频进行了比较,结果表明,所提算法的抗跟踪干扰性能显著优于已有算法。      

Anomaly‐based intrusion detection of jamming attacks,local versus collaborative detection

We present intrusion detection algorithms to detect physical layer jamming attacks in wireless networks. We compare the performance of local algorithms on the basis of the signal‐to‐interference‐plus‐noise ratio (SINR) executing independently at several monitors, with a collaborative detection algorithm that fuses the outputs provided by these algorithms. The local algorithms fall into two categories: simple threshold that raise an alarm if the output of the SINR‐based metrics we consider deviates from a predefined detection threshold and cumulative sum (cusum) algorithms that raise an alarm if the aggregated output exceeds the predefined threshold. For collaborative detection, we use the Dempster–Shafer theory of evidence algorithm. We collect SINR traces from a real IEEE 802.11 network, and with the use of a new evaluation method, we evaluate both the local and the Dempster–Shafer algorithms in terms of the detection probability, false alarm rate, and their robustness to different detection threshold values, under different attack intensities. The evaluation shows that the cusums achieve higher performance than the simple threshold algorithms under all attack intensities. The Dempster–Shafer algorithm when combined with the simple algorithms, it can increase their performance by more than 80%, but for the cusum algorithms it does not substantially improve their already high performance.Copyright © 2013 John Wiley & Sons, Ltd.     

Frequency-hopped spread-spectrum transmission with band-efficientmodulations and simplified noncoherent sequence estimation

Frequency-hopped spread-spectrum transmission using band-efficient modulations that are phase-continuous during each hop, is presented. A range of system parameters is considered, including signaling spectrum, reception, system complexity, and performance in the presence of noise and jamming. The particular cases where the hopped modulation is minimum-shift-keying (MSK), duobinary minimum-shift-keying (DMSK), or tamed-FM (TFM), are studied in detail. Results are presented for various modulation indexes, rectangular and raised cosine pulse shapings, and a range of hop interval lengths. Sequence estimation on a hop-by-hop basis is considered. The noncoherent likelihood sequence receiver must keep all possible paths, and so the computation and complexity becomes large for system transmitting many bits per hop. Therefore, a simplified noncoherent Viterbi-like sequence estimation algorithm with reduced complexity is introduced. System performance has been evaluated in Gaussian noise, partial-band jamming and multiple-tone jamming, using bounds and a system simulation. The compact nature of the hopped spectrum, when a number of bits are transmitted per hop, offers greater spectrum utilization and the prospect of improved performance in the presence of multiple-tone jamming or interference     

Performance of FHSS systems employing carrier jitter againstone-dimensional tone jamming

The performance of a frequency-hop spread-spectrum system employing carrier jitter against one-dimensional tone jamming (n=1 band multitone jamming) is investigated. First, noncoherent BFSK signaling under continuous-wave (CW) tone interference with arbitrary frequency offset is analyzed. A closed-form expression is derived for the error probability when there is one interfering CW tone and the background noise is negligible. When the background noise is significant, an expression involving one numerical integration is derived for the probability of error. It is shown that an interfering CW tone with power less than that of the signal can still cause errors with significant probability for certain ranges of carrier offsets. Next, the authors apply these results in analyzing the performance of a FHSS communications system under one-dimensional tone jamming when the communicator pseudorandomly jitters his carrier frequency from hop to hop. Two different methods of carrier jittering are considered. It is found that one of the schemes offers approximately a 3 dB gain in signal-to-noise ratio over a system without carrier jittering while the other scheme offers no significant gain     

Design and analysis of a fast frequency-hopped DBPSK communicationsystem. I. Error performance in AWGN plus partial-band noisejamming

The purpose of the paper is to present the design and performance analysis of a fast frequency-hopped (FFH) spread spectrum communication system employing differential binary phase-shifted-keying (DBPSK) modulation and differentially coherent demodulation. The receiver utilizes a hop time tracking loop to “lock” the hop clock. The authors present an analysis of the average bit error probability of the overall system when it is operating in additive white Gaussian noise plus partial-band noise jamming. The effect of channel phase distortion is also studied     

HTRCI and Channel Ranking Based Joint Symbols Detection for MQRD-PCM/MIMO-OFDM

MIMO-OFDM is considered a key technology in emerging high-data rate systems. In MIMO-OFDM systems, channel estimation and signal detection are important to distinguish transmit signals from multiple transmit antennas. Previously, we have proposed a parallel detection algorithm using multiple QR decompositions (Q is an orthogonal square matrix, R is upper triangular matrix) with permuted channel matrix (MQRD-PCM) to reduce the system complexity of MIMO-OFDM. This method achieves a good BER performance with a low system complexity. However, since MQRD-PCM is a kind of parallel detection method, the wrong detection probability is increased due to the bad channel signal-to-interference plus noise power ratio (SINR) of the transmitted signals. As a result, the average BER performance is influenced by the wrong detection probability of the bad channel SINR. To overcome the above-mentioned problems, in this paper, we propose the high time resolution carrier interferometry and channel ranking based joint signal detection for MQRD-PCM/MIMO-OFDM.     

Impact of co‐channel interference on performance of dual‐hop wireless ad hoc networks over α−μ fading channels

In this work, we investigate the performance of a dual‐hop cooperative network over α?μ fading channels with the presence of co‐channel interference (CCI) at both the relay and destination nodes. Amplify‐and‐forward (AF) relaying is considered in the relay node. The upper bound of the signal‐to‐interference‐plus‐noise ratio (SINR) of the dual‐hop relay link is used to determine the system performance. The probability density function (PDF) and the cumulative distribution function (CDF) of the upper bound of the SINR are analyzed. The system performance is determined in terms of the outage and error probabilities. Numerical results are used to present the performance analysis of the system.     

OFDM系统中宽带干扰的差分检测算法的研究

提出了一种基于导频辅助的宽带干扰(WBJ)差分检测算法,不但能判断干扰出现的位置,而且还能计算出每个子载波的SINR(包括干扰和噪声的信噪比).通过理论的分析和仿真,验证了本文提出的算法能够比较准确地检测出宽带干扰的位置和每个子载波的信干噪比(SINR).     

ML-based follower jamming rejection in slow FH/MFSK systems with an antenna array

The jamming robustness of frequency hopping (FH) systems with M-ary frequency shift keying (MFSK) modulation may be potentially neutralized by a follower partial-band jammer. In this paper, a maximum likelihood (ML)-based algorithm that uses a two-element array is proposed for joint follower jamming rejection and symbol detection in slow FH/MFSK systems over quasi-static flat Rayleigh fading channels. The algorithm is derived by treating both the received jamming components and the unknown data symbols as deterministic quantities to be jointly estimated in an integrated ML operation. In addition, an approximate expression for the symbol error rate (SER) of the proposed scheme is derived when BFSK signaling is employed in a jamming dominant scenario. Analytical and simulated results show that the proposed approach is able to remove jamming and outperform the conventional and sample matrix inversion (SMI)-based beam-formers in the presence of a follower partial-band jammer.