基于卫星移动MIMO系统的天线相关性性能分析

研究了卫星移动MIMO系统中,上、下行信道存在阴影衰落和空间相关条件下的系统性能,利用围线积分、留数定理及特殊函数积分等方法推导了系统中断概率(OP),平均符号错误概率(SER)的闭合表达式。利用Monte-Carlo仿真分析了系统在不同相关系数、天线数目及调制方式下的性能表现。仿真结果表明,尽管阴影衰落和空间相关性降低了系统性能,但与单天线系统相比,卫星移动MIMO系统的OP及SER改善明显。     

子载波序列调制GO-MC-CDMA系统的性能分析

SIM-GO-MC-CDMA是GO-MC-CDMA与子载波序列调制相结合的系统。分析了SIM-GO-MC-CDMA采用迫零检测时系统性能;比较不同数字调制方式对误比特率(BER)的影响。通过蒙特卡洛仿真分析表明:SIM-GO-MC-CDMA的系统可得到低误码率。     

Effects on correlation between two mobile radio base-station antennas

The correlation between signals received by two mobile radio base-station antennas is investigated to determine spacing requirements for space diversity. Measurements of the fading of UHF signals received by two base-station horn antennas oriented at different angles with respect to the incoming mobile radio signal were made for different antenna spacings. The experimental results are compared with an analytical expression derived in this paper; they agree fairly well. A further experiment was made after removing the possible local scatterers surrounding the base station. Comparing these two experimental results, we find that the following are true. 1) Propagation in the direction of a line connecting the two base-station antennas is the critical case and requires a large separation of 70 wavelengths. As soon as the incoming wave is 10° away from the in-line axis, the spacing requirement drops to 30 wavelengths. 2) Local scatterers at the base station tend to decrease the correlation between signals received at the two antennas. We conclude that an upper limit to the spacing of antennas used for diversity can be obtained and that it is within the achievable range.     

基于灰色关联算法的雷达反隐身性能评估

雷达反隐身的性能评估对现代空防战争具有重要意义。在深入分析雷达反隐身技术及相关基础理论基础上建立了雷达反隐身性能指标体系,提出了采用基于自适应熵权的灰色关联算法来进行雷达反隐身性能评估,解决了评价权重模糊问题,并结合经典最小二乘法和拉格朗日函数建立了优化评估模型,最后通过算例分析给出了该算法模型的应用过程,分析结果表明该算法能有效实现对雷达反隐身性能的排序和优选。     

基于信道相关性的物理层安全性能分析

针对物理层安全研究中主窃信道具有相关性的场景,研究了主窃信道间的相关性对系统安全性能产生的影响,推导得到了遍历保密容量及中断概率的精确计算式,以及主窃信道的信道状态差异较大和较小这2种场景下的渐近计算式,并通过仿真验证了理论分析的正确性.研究结果表明,信道相关性会造成遍历保密容量的损失,但信道相关性强并不一定表明通信中...     

基于自适应响应融合的相关滤波红外目标跟踪

红外目标跟踪在军事和民用视频监控领域有重要的研究意义,但受热成像原理限制,红外目标分辨率低、对比度低、纹理信息缺失。针对红外目标特征信息量少导致跟踪性能较低的问题,提出一种基于自适应响应融合的相关滤波跟踪算法。该算法基于连续卷积运算的相关滤波跟踪框架,通过构造视觉显著性特征来增强目标外观描述,并结合对冲决策理论对由不同特征计算得到的多个滤波响应进行自适应融合,最终根据融合响应预测目标中心位置。此外,通过尺度滤波器来实现目标的尺度预测,得到完整的跟踪结果。在公开的红外视频数据集VOT-TIR2016进行测试,实验结果表明:与同类算法相比,该算法表现出更高的跟踪精确度和鲁棒性。     

Breaking two secure communication systems based on chaotic masking

This paper describes the security weakness of two generalized nonlinear state-space observers-based approaches for both chaos synchronization and secure communication, using chaotic masking and chaotic modulation of a Lorenz system. We show that the security is compromised without any knowledge of the chaotic system parameter values and even without knowing the transmitter structure.     

基于感知与性能相关性的网络负荷问题研究

随着网络演进及业务发展,数据业务呈现爆炸式的增长,移动网络高负荷问题日益突出,严重影响了用户业务质量.本文介绍了一种基于用户感知的网络负荷分析方法,通过大数据用户感知与网络性能的相关性分析,可以智能地判断网络负荷对于用户业务质量的影响,准确识别高负荷网元,应用于网络运维优化,提升网络质量.     

异步DS-CDMA系统中基于符号级相关阵的DOA估计

针对异步DS-CDMA系统多用户环境，本文提出了一种有效的DOA估计算法。首先，将天线阵分为等阵元的两组，并且在符号级构造出不含噪声项的组间相关阵；然后，根据最小二乘准则分离出DOA信息；最后，利用MUSIC算法逐个估计出各路径的DOA。算法具有分辨率高，顽健性强及硬件要求低等优点。仿真实验验证了算法的有效性。     

基于最佳相关序列的MIMO-OFDM系统信道估计

基于序列相关性提出了一种多输入多输出-正交频分复用(MIMO-OFDM)系统的时域信道估计方法。通过在OFDM符号间插入一种具有最佳相关性的实训练序列,在接收端将接收序列与训练序列作相关运算,得到信道的时域冲激响应。并通过信道阶数估计,进一步提高算法估计性能。理论分析和实验仿真结果均表明,与现有方法相比,本文方法具有更高的系统传输效率和更高的估计性能。     

基于SOA的两种干涉仪结构性能分析

对基于半导体光放大器的萨格奈克型(Sagnac)和马赫曾德型(MZ)两种干涉仪结构的性能进行了分析比较.首先讨论了干涉仪在对数据进行逻辑操作时出现的光能量泄漏问题,并给出了试验结果.随后对数据帧宽度、数据流占空比和光纤环长的关系进行了详细分析.     

一种基于Bigram二级哈希的中文索引结构

为通过构建高速的中文索引结构来提高Off-line模式的串匹配速度,提出了一种基于Bigram二级哈希的中文索引结构。该索引采用中文GB2312编码处理中文汉字,以中文Bigram项作为词汇项,并实现了基于二级哈希的词汇表存储结构。实验数据显示,本文索引结构虽然占用存储空间为词索引的2倍多,但其匹配速度是词索引的4倍多。结果表明本文索引在中文匹配中具有速度优势。     

基于混沌参数调制的多进制数字通信系统的性能比较

基于混沌参数调制方式,设计和实现了一种多进制的数字扩频通信方案-CPSM(Chaotic parameter spreading modulation),研究了用不同的混沌系统作为载波信号并在不同的扩频因子条件下,二进制和四进制数字扩频通信系统的性能,并分析了影响系统性能的因素.仿真结果表明加大扩频因子有助于提高这些系统的性能,同时也发现Chua系统的信号更适合于多进制数字通信.此外,这些系统具有较好的抗干扰能力,且易于实现.     

基于大系统方法的上行CDMA蜂窝系统性能分析

结合大尺度和小尺度衰落,采用大系统分析方法对CDMA蜂窝系统上行链路的性能进行分析。首先分析了小区内多址干扰和小区间干扰的情况;其次推导出了通过匹配滤波器后的信干噪比值,该值只与小区负载、用户功率、信道增益有关;最后分析了系统的误码率、吞吐量和频谱效率,并通过仿真验证了分析的准确性。仿真结果发现,随着小区负载的增大,系统的误码率增大,吞吐量下降,但频谱效率有所提高。     

基于蒙特卡罗仿真的多种二进制通信系统性能分析

介绍了在加性高斯噪声干扰条件下,多种二进制通信系统信号的传递与最佳接收,根据蒙特卡罗仿真方法基本思想,建立在加性噪声干扰下的相关检测系统蒙特卡罗仿真模型。模型通过Matlab软件方法实现,最终仿真结果与对应系统的理论误码率基本符合。     

An improved channel estimation method based on the correlation of preambles in FBMC/OQAM systems

Filter bank multicarrier transmission with offset QAM (FBMC/OQAM) is recognized as one of candidates for the next generation of multi-carrier modulation scheme due to its high spectral efficiency and extremely low out-of-band attenuation. However, channel estimation (CE) performance may be seriously deteriorated by the intrinsic interference in practice. Because the correlations of preambles at the receiver may not be taken into account for traditional methods, which are recognized as inter-symbol interference. This paper proposes an improved preamble-based CE method, which has lower preamble power and higher time efficiency, and a CE algorithm using correlation between adjacent subcarriers is introduced to improve performances further. Finally, the CE algorithm with correlations between adjacent K subcarriers is deduced. Simulation results show that the proposed scheme has lower BER and preamble power, compared to the traditional methods.     

Time-domain channel estimator based on cyclic correlation for OFDM systems with guard interval

Channel impulse response （CIR） can be estimated on the basis of cyclic correlation in time-domain for orthogonal frequency division multiplexing （OFDM） systems, This article proposes a generalized channel estimation method to reduce the estimation error by taking the average of different CIRs. Channel impulse responses are derived according to the different starting points of cyclic correlation. In addition, an effective CIR length estimation algorithm is also presented. The whole proposed methods are more effective to OFDM systems, especialiy to those with longer cyclic prefix. The analysis and the simulation results verify that the mean square error performance is 4-5 dB better than the conventional schemes under the same conditions.     

Performance of two 4×4 guided-wave photonic switching systems

Data from two photonic switching systems are presented, the first is a 4×4 crossbar, and the second is a 4×4 passive splitter/active combiner broadcast switch. The 4×4 crossbar has operated continuously and reliably for 18 months with no noticeable performance degradation. The 4×4 passive splitter/active combiner has operated for six months and yields excellent bit-error-rate (BER) performance at 1.7 Gb/s, showing that the influence of optical crosstalk in a small guided-wave optical switching system does not significantly affect the BER     

Full-duplex radio-over-fiber transport systems based on two modes injection-locked FP LD

A full-duplex radio-over-fiber (ROF) transport system based on two modes injection-locked Fabry–Perot laser diode (FP LD) is proposed and demonstrated. Performances over a 40-km standard single-mode fiber (SMF) full-duplex transmission were investigated. Good performances of bit error rate (BER) and error vector magnitude (EVM) were obtained in our proposed systems. Since our proposed systems use only one FP LD as light source for both down-link and up-link transmissions, it reveals a prominent alternative with advantages in simplicity and cost.