共查询到19条相似文献,搜索用时 62 毫秒
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自适应跳频是建立在自动信道质量分析基础上的一种技术,能够自动避开被干扰频点,具有较好的灵活性、可靠性和保密性的特点.这里首先介绍了一种自适应跳频系统的模型,阐述了自适应跳频的工作原理和通信过程;然后,对比了最新的几种典型频率自适应算法,给出了不同频率自适应算法的流程图;最后,对几种典型的频率自适应算法的优点和不足之处进行了总结,为实际的工程应用提供了重要的参考. 相似文献
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鉴于自适应跳频系统的良好抗干扰性能,提出了一种自适应跳频卫星通信系统的设计方案。在简要介绍自适应跳频技术基本原理的基础上,叙述了自适应跳频通信系统的结构和通信过程,重点讨论了自适应跳频卫星通信系统的设计模型、同步方式、频率集更新算法和抗干扰性能,最后,给出了自适应跳频卫星通信抗干扰终端设备的基本实现过程。 相似文献
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OFDM系统中多导频的FFT信道估计算法 总被引:5,自引:1,他引:4
论文提出了OFDM系统中基于FFT的信道估计方法,包括基于时域插值及变换域插值方法。时域插值算法的理论基础是利用FFT频域采样定理,可由频域有限频点的采样值经过IFFT/FFT得到整个频域传输函数的估计值,而不发生混叠。变换域插值算法的理论基础是利用FFT时域抽样定理,利用OFDM信号特点和信道特性,经过FFT/IFFT将信号和噪声分离,并在此基础上进行加窗改进算法,以减小插值中的频谱泄漏,提高估计效果。仿真结果说明,加窗的基于FFT变换域的方法性能有了很大改善。 相似文献
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文章基于进一步提高跳扩频通信系统的抗干扰性能,提出了在混合直接序列扩频(DS/SFHCDMA)通信系统中实现自适应跳频(AFH)方式,给出了基于优化考虑的自适应跳频地址编码方法,在给出信道仿真参数的前提下,对自适应跳频系统的误码性能进行了分析。结果表明自适应方式优于传统方式。 相似文献
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基于均匀矩形阵列,利用阵列接收信号及其共轭信息,推导出2维的虚拟空间平滑算法。通过构造2维虚拟子阵,消除干扰信号与期望信号之间的相关性,避免了有效阵列孔径的损失,提高了算法的空间谱分辨率。将该算法与相位补偿技术相结合,给出了一种抗跟踪式干扰的跳频通信系统。通过理论分析和模拟仿真,验证了该系统对跟踪式干扰具有较好抑制能力,在干扰方向的零陷抑制深度达50 dB以上,并且与普通跳频系统相比在-3 dB的强干扰环境下具有优良的误码率特性。 相似文献
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基于概率映射的短波自适应跳频方法 总被引:1,自引:1,他引:0
短波通信以其通信距离远,设备简单等诸多优点近几年来受到越来越多的关注和应用。但是短波信道环境复杂,天波传输时受电离层电磁环境影响大,信号在传输过程中会产生瑞利衰落现象,加之各种干扰的影响,信息传输可靠性不高。自适应跳频作为抗干扰的一种有效措施,能够提高通信系统的吞吐量。自适应跳频技术应用于短波通信中以提高其抗干扰能力及通信质量。利用信噪比检测的方式,由各个信道的检测出的信噪比产生一个概率分布函数,该函数由接收方反馈到发送方。双方握手成功后,发送方按照质量好的频点选择概率大、质量差的频点选择概率小的原则选取频率集中某频点传输信息。 相似文献
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跳频通信中的抗干扰同步算法研究 总被引:1,自引:0,他引:1
跳频通信体制以其较好的抗干扰和低截获性能,在军事通信中有着广泛的应用,其中跳频同步是该体制的关键技术之一。为提高跳频通信系统抗干扰性能,提出了一种具有自适应抗干扰能力的跳频同步方案,并给出了系统框图及关键算法分析及性能讨论。最后仿真结果表明,该同步方案具有抗干扰能力强,捕获概率高,虚警概率低的特点,而且在保证同步时间要求的前提下,具有根据信道特性,自适应地调整抗干扰门限的能力。 相似文献
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针对在跳频信号跳变时刻和跳变频率估计方面实时性和估计精度无法同时兼顾的问题,提出了一种基于短时傅立叶变换(STFT)和多重信号分类(MUSIC)算法的跳频信号参数估计方法。在建立跳频信号数学模型的基础上,利用STFT选取较大时间窗对整个信号在时域进行粗搜索,生成时频谱图,提取时频脊线从而获得跳变时刻,然后选取较小时间窗在已知跳变时间段利用STFT进行跳变时刻的细估计,并利用MUSIC算法进行频率的精确估计。该方法利用STFT的二次估计,减少了MUSIC搜索范围,从而降低了时间开销。仿真表明该算法的跳变时刻频率估计精度高,实时性能满足参数测量需求。 相似文献
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The Generalized S-transform (GST) applied in Instantaneous Frequency (IF) estimation is addressed in this paper. The analytical model for IF estimation error using the GST is established, which reveals that the estimation bias is determined directly by two variables: the standard deviation of the Gaussian window and the Instantaneous Frequency Rate (IFR) of the test signal. Based on the mathematical model, performance of the GST as an IF estimator is analyzed by three steps. Firstly, the time-varying expression for IF estimation Relative Error (RE) using the GST is derived. Secondly, the relationships between the RE and the signal’s frequency characters are found. Thirdly, the effects of the window parameters on the RE are discussed. Consequently, a novel Adaptive Generalized S-transform (AGST) is developed, in which the window parameters are automatically adjusted in order to process signals with fast changing frequency characters. The proposed method is evaluated through several kinds of test signals to show its efficiency in IF estimation. 相似文献
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Mechanisms based on frequency hopping have been widely used to enable short-range wireless networks to use resources from the unlicensed spectrum without frequency planning. Bluetooth piconet is a prime example of an FH-based network with unlicensed operation. As a price for open access, the piconet may experience adverse interference from other collocated FH piconets or other wireless devices that are transmitting in the same unlicensed band. A basic approach to mitigate this interference is that the piconet applies adaptive FH (AFH) and attempts to hop over a set (hopset) of less interfered channels. On the other hand, the regulation of unlicensed operation sets constraints on possible hopset adaptations. In this article we present two novel AFH strategies: adaptive frequency rolling (AFR) and dynamic AFH (DAFH). AFR avoids self-interference while preserving the dynamics of spectrum usage as required by the current regulation. DAFH is a distributed mechanism by which collocated piconets select nonconflicting hopsets while trying to keep the hopset size as large as possible. DAFH is not completely compliant with current regulations, but the rationale given for its design contains new rules of behavior for the unlicensed spectrum. Both approaches significantly outperform the conventional AFH strategy 相似文献
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Qingxin Chen Sousa E.S. Pasupathy S. 《Selected Areas in Communications, IEEE Journal on》1996,14(9):1852-1858
A modified multicarrier (MC) direct-sequence code-division multiple-access (DS-CDMA) system has been proposed for use over slow multipath fading channels with frequency selectivity in the reverse link transmission of a cellular network. Instead of transmitting data substreams uniformly through subchannels, data substreams hop over subchannels with the hopping patterns adaptively adjusted to the channel fading characteristics. The problem of determining the optimal hopping pattern is formulated as a multiobjective optimization problem, for which an efficient algorithm, based on the water-filling (WF) principle, is designed to solve the problem practically. Simulation results show that the performance in terms of the average bit-error probability (BEP) (over all users) is better than that of single carrier RAKE receiver systems, conventional MC CDMA systems applying moderate error protection, or diversity systems with different combining techniques 相似文献
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针对超密集组网中导频复用将产生导频干扰,严重影响移动用户下行链路信道估计准确性的问题,提出了一种使用短导频的幂函数稀疏度自适应匹配追踪(Power Sparsity Adaptive Matching Pursuit,PSAMP)算法.该算法由稀疏度预估计和追踪重构两部分构成.首先通过幂函数试探得到一个略小于真实稀疏度的预估值,再通过压缩采样匹配追踪重构信号,改善估计结果;若不能成功重构,则逐渐增加信号原子数量.仿真结果表明,相较于传统自适应压缩感知重建算法,所提的P SAMP算法在高信噪比区域具有更好的信道估计性能. 相似文献
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