水声跳频通信系统抗干扰性能仿真研究

跳频通信系统与常规定频通信系统相比具有较强的抗干扰能力。在介绍水声跳频通信基本原理的基础上,分析了在部分频带干扰下的跳频通信系统的抗干扰性能,并提出利用信号分集技术解决部分频带干扰问题。借助MATLAB仿真工具,得到不同情况下的误码率．信噪比曲线,从而验证了理论分析的结果。     

短波FH/OFDM通信系统抗跟踪式干扰性能分析

对于短波多载波跳频通信系统,跟踪式干扰是一种有效的干扰模式。分析了正交频分复用( OFDM)部分子信道干扰与符号误码率的关系,通过仿真获得了最佳跟踪干扰的部分时间参数,结合OFDM频谱结构与干扰频谱关系,推导了高斯信道条件下部分频带干扰和多音干扰时系统误码率,分析了短波FH/OFDM通信系统抗跟踪式干扰的误码率性能,仿真结果表明：跟踪干扰时间窗口对误码率的影响与部分频带干扰因子和信干比有关;在部分频带干扰与部分时间干扰之间,存在等效的干扰效果区域;多音干扰因子越大,系统所受影响越大,跟踪干扰时间窗口对误码率的影响与多音干扰因子和信干比有关,针对OFDM符号的多音干扰影响要远大于部分频带干扰的影响;跳频与OFDM技术的结合、提高载波跳速、减小跟踪式干扰对OFDM符号的影响,也是消除多音干扰的重要手段。     

短波自适应跳频通信抗干扰技术研究

针对军事无线通信抗干扰和保密性需求，给出了自适应跳频通信系统模型。采用双态信道模型，深入分析了自适应跳频系统的抗干扰性能。分别在部分频带噪声干扰和多音干扰下，对常规跳频系统和自适应跳频系统性能进行了仿真，结果表明自适应跳频系统对上述两种干扰有较好的抗干扰性能。     

短波差分跳频系统抗部分频带干扰性能分析

对接收端采用非相干平方律能量检测器及维特比译码器的短波差分跳频通信系统,在无衰落信道和频率非选择性慢衰落信道下抗部分频带干扰的性能进行了理论分析.若信道存在衰落,则假设每跳所经历的衰落过程是相互独立的,且服从瑞利分布.部分频带干扰被模拟为加性高斯噪声,分析中考虑了背景热噪声.结果表明:差分跳频相邻两跳频率之间的相关性为系统提供了良好的抗部分频带干扰的能力.若忽略背景热噪声,则当信干比为20dB时,在无衰落信道下最坏情况比特误码率可达10-5,而在频率非选择性瑞利慢衰落信道下最坏情况比特误码率可达10-3.     

部分频带干扰对跳频通信系统影响分析

部分频带压制干扰是现有的对跳频通信系统最有效的干扰方式之一。在分析了部分频带干扰对跳频同步和系统误码率影响的基础上,仿真了干扰条件下的同步捕获性能和系统误码率曲线。验证了部分频带压制干扰在覆盖同步频率时能有效降低同步捕获概率,当不覆盖同步频率时也能提高系统误码率,达到破坏敌方通信的目的。     

基于Simulink的跳频通信系统抗干扰性能分析

跳频通信方式是军事通信的主要手段,保证跳频通信系统的正常工作十分重要,研究了跳频通信的几种常见干扰样式,用Simulink仿真工具搭建跳频通信系统仿真平台,并模拟几种常见干扰源,包括宽带或部分频带阻塞干扰、梳状阻塞干扰及跟踪干扰。分别在信道注入各种干扰,得到相应的误码率曲线,分析并评价其抗干扰性能。     

一种基于认知的动态频谱抗干扰新技术

针对传统的“固定频谱”通信体制在未来信息化战争中所存在的不足,基于认知无线电中机会频谱接入的思想,提出一种动态频谱抗干扰新体制。对动态频谱抗干扰体制的基本原理进行了简要阐述,并在短波干扰信道模型下,对采用硬判决译码的简化动态频谱抗干扰系统的信道容量进行了分析,定量给出了其相对于固定频谱通信体制的性能改善。最后,对动态频谱抗干扰实现中应解决的关键技术进行了探讨。     

跳频通信系统抗干扰性能分析

在介绍跳频通信基本原理的基础上,分析了在部分频带干扰和宽带阻塞干扰这两种常见干扰下的跳频通信系统的抗干扰性能,并借助计算机仿真工具MATLAB进行程序仿真,得到了在两种干扰下的误码率—信噪比曲线,从而验证了由理论分析而来的结果。同时,提出了用信号分集来克服部分边带干扰,并分析了其效果。     

跳频通信技术研究及仿真分析

跳频通信系统具有较强的抗干扰能力,在现代通信中具有广泛的应用.了解跳频通信基本原理及不同干扰样式下抗干扰性能,能在通信对抗中实施更有效的干扰与反干扰.在对跳频通信基本原理进行分析阐述的基础上,采用Matlab/Simulink对跳频通信系统进行了仿真.针对宽度噪声干扰、 部分频带干扰和单音干扰3种特定干扰样式下跳频通信...     

自适应跳频通信系统抗干扰性能分析

部分频带噪声干扰和多音干扰对常规跳频通信系统危害较大,自适应跳频系统能够改善跳频通信系统的抗干扰性能。基于自适应理论,对两个系统的抗干扰性能进行了仿真和比较,结果表明,自适应跳频通信系统对抗这两种干扰性能较强,适用于军事通信和其它易受人为干扰的通信领域。     

A Robust Acquisition Scheme for FH Signal in Adverse Environments

Both partial-band jamming and multi- tone jamming have severe effect on the acquisition of frequency-hopping (FH) signal in adverse environments. In this paper, an anti-jamming FH signal acquisition scheme based on cognitive correlation process is proposed to boost the robustness of acquisition. The main idea of this scheme is to utilize a priori knowledge of FH speed and FH pattern to distinguish jamming signal from received signal. Furthermore, theoretic analysis on detection probability and false probability is given to demonstrate the robust performance of the FH signal acquisition method compared with conventional acquisition scheme without any prior information on FH speed and pattern in adverse environments.     

用不同调制方式实现跳／扩频混合通信的抗干扰性能

介绍了BPSK,QPSK,16PSK,FSK,MSK及GMSK 6种数字调制方式的特点,采用Matlab中的Simulink建立了各种调制方式实现DS/FH混合扩频系统的仿真模型.重点研究了跳/扩频通信系统在具有扫频干扰、跟踪干扰以及两者共存的环境下,采用不同调制方式时抗干扰性能的差异,并通过仿真计算误码率给出比较结果,由此得到的结论是：3种相移键控中的BPSK抗干扰性能最好,3种频移键控中的2FSK抗干扰性能最好,并且BPSK的抗干扰性能优于2FSK.     

Diversity and Coding for FH/MFSK Systems with Fading and Jamming--Part I: Multichannel Diversity

The performance of diversity and/or coding is evaluated for FH/MFSK signaling over Rayleigh fading channels in the presence of jamming. The effects of partial-band tone and partial-band noise jamming on uncoded and coded systems are considered. The results indicate that FH/MFSK signaling with diversity provides satisfactory performance for jammed fading channels. For coded FH/MFSK signaling over fading channels, noise jamming may be more effective than tone jamming. The amount of improvement resulting from the use of diversity in conjunction with coding depends upon many factors, including the nature of the channel, the degree of channel state information available at the decoder, the type of decoding, and the modulation alphabet size.     

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.     

MC-SS系统抗部分频带干扰性能分析

多载波扩频(MC-SS)技术结合了OFDM和扩频技术的优点,具有很强的抗干扰能力。MC-SS系统、MC-DS-SS系统和MT-SS系统是3种主要的多载波扩频系统。而部分频带干扰是一种常见的干扰类型。在介绍几种主要的多载波扩频系统的基础上,分析了多载波扩频系统的抗部分频带干扰的能力,给出了在干扰信息状态(JSI)已知和未知状态下的误码率。     

卷积码差分跳频系统抗部分频带干扰的性能

基于对无编码差分跳频系统抗部分频带干扰性能的研究,将卷积码引入差分跳频系统,研究了在有精确干扰状态信息的情况下,采用无迭代译码和迭代译码时相对于无编码系统的性能改善.同时,在无法得到精确干扰状态信息的情况下,提出了一种迭代干扰状态估计及译码算法.理论分析结果表明:在有精确干扰状态信息的情况下,采用卷积纠错编码和无迭代译码,对可用频率数为8的差分跳频系统,当比特误码率(BER)为10~(-6)时,性能改善约为2.5dB;而采用迭代译码,当BER为10~(-10)时,相对于无迭代译码,性能可进一步改善6dB.仿真结果则验证了迭代估计及译码算法的正确性,采用该算法可使编码系统在无精确干扰状态信息的情况下,仍能保持良好的抗干扰能力.     

Probability of Error Analyses of a BFSK Frequency-Hopping System with Diversity Under Partial-Band Jamming Interference--Part I: Performance of Square-Law Linear Combining Soft Decision Receiver

In this paper, error probability analyses are performed for a binary frequency-shift-keying (BFSK) system employingLhop/bit frequency-hopping (FH) spread-spectrum waveforms transmitted over a partial-band Gaussian noise jamming channel. The error probabilities for theLhop/bit BFSK/FH systems are obtained as the performance measure of the square-law linear combining soft decision receiver under the assumption of the worst-case partial-band jamming. The receiver in our analysis assumes no knowledge of jamming state (side information). Both exact and approximate (multiple bound-parameter Chernoff bound) solutions are obtained under two separate assumptions: with and without the system's thermal noise in the analyses. Numerical results of the error rates are graphically displayed as a function of signal-to-jamming power ratio withLand signal-to-noise ratio as parameters. All of our results, exact and approximate, indicated that the higher number of hops per bit produced higher error probabilities as a result of increased combining losses when the square-law linear combining soft decision receiver is employed in demodulating the multihop-per-bit waveform.