AR自编码扩频通信系统的研究

在自编码扩频通信原理的基础上,介绍了利用自回归(Auto-Regressive,AR)滤波的方法从信源序列中提取扩频码的AR自编码扩频系统,并对该系统的误码性能和多址通信能力进行了理论分析和仿真.结果表明,AR自编码扩频系统改善了普通自编码扩频系统的误码性能,提高了系统的多址能力,为自编码扩频通信的实际应用提供了可选的方案.     

AR-SESS通信系统中扩频序列的相关性

介绍了利用自回归(Auto-Regressive, AR)滤波的方法从信源序列中提取扩频码的AR自编码扩频通信系统(AR-SESS).在扩频通信中,扩频序列的相关特性对扩频系统的性能有重要影响.从理论上分析了采用AR滤波方式产生的扩频序列的相关特性,并进行Matlab仿真试验.仿真结果表明,自编码扩频序列具有良好的自相关和互相关特性,可以在扩频通信中实现多径识别和多址用户的区分.     

自编码扩频通信的捕获

自编码扩频通信的扩频序列是由待传输的信息中获得的,这种特殊性决定了其同步捕获方式的不同.提出一种基于发送同步码并周期复位的同步方案.理论分析及实验仿真表明,在高斯白噪声信道中,该捕获方案的性能接近传统扩频通信的同步捕获方案,且同步码周期的提高能有效改善其捕获性能.     

基于Gram-Schmidt正交化法的串行干扰消除算法

基于Gram-Schmidt正交化法,提出了一种改进的串行干扰消除算法.不同于传统的串行干扰消除算法,该算法运用Gram-Schmidt正交化法,通过扩频序列获取正交序列作为最优解扩码,使得检测器每一级最强用户的解扩码与其他用户的扩频码所张的子空间正交,从而实现对多址干扰的完全抑制.给出了具有幅度失配的系统误码率近似公式,讨论了幅度失配对检测性能的影响.仿真结果表明,改进算法能有效抑制CDMA系统中的多址干扰,改善系统性能.     

基于优化方法的自适应跳频地址编码方法

为提高跳扩频通信系统抗干扰性能，提出了在多载 直接序列跳扩频（ＭＣ－ＤＳ／ＦＨＣＤ－ＭＡ）通信系统中实现自适应跳频（ＡＦＨ）方式时，基于优化的自适应跳频地址编码方法。在给定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。     

多径Rayleigh衰落信道中二元正交码扩频多址通信系统的性能分析

研究了随机二元正交码直接序列扩频多址信号在多径Ｒａｙｌｅｉｇｈ衰落信道传输中，在非相干ＲＡＫＥ接收机中采用两种不同最大选择接收方案（最大输出信噪比选择及最大输出功率选择分集接收）时，系统的差错特性和差错概率表达式。数值计算结果示出了在多径衰落信道中，分集接收对扩频多址系统性能的影响，同时表明在多径Ｒａｙｌｅｉｇｈ衰落信道中，最大输出功率选择分集接收时扩频系统的差错性能优于最大输出信噪比选择时扩频系     

直接序列扩频通信中扩频码捕获系统的研究

围绕扩频通信中的关键技术-扩频码的捕获展开讨论.针对直接序列扩频通信中的同步速度问题,研究了扩频码的捕获原理;通过状态分析,利用编码序列相位转移图,研究了扩频码的捕获过程;论述了虚警产生的原因、虚警概率和虚警对同步捕获速度的影响.在此基础上,提出了一种带有辅助电路的扩频码捕获系统,该系统可大大降低非相关状态下输入门限检测器的等效噪声电压,从而降低虚警概率,缩短捕获时间,提高通信效率.     

直接序列扩频通信中扩频码捕获系统的研究

围绕扩频通信中的关键技术-扩频码的捕获展开讨论．针对直接序列扩频通信中的同步速度问题。研究了扩频码的捕获原理；通过状态分析，利用编码序列相位转移图，研究了扩频码的捕获过程；论述了虚警产生的原因、虚警概率和虚警对同步捕获速度的影响．在此基础上，提出了一种带有辅助电路的扩频码捕获系统，该系统可大大降低非相关状态下输入门限检测器的等效噪声电压，从而降低虚警概率，缩短捕获时间，提高通信效率．     

联合多址系统中扩频码的分配算法

在基于码分多址（CDMA）和空分多址（SDMA）技术的联合多址系统中，扩频码的分配应根据移动用户空间向量的正交性来进行。文中给现一扩频码的分配算法。应用该算法，相同的扩频码可分配给同一小区内不同SDMA信道的用户，进而提高CDMA系统的通信容量。     

变长序列相关性与DS-CDMA性能分析

基于对变长扩频序列相关特性的分析，研究了采用0VSF扩频序列的多速率异步DS—CDMA系统性能，导出以序列非周期部分相关表示的多址干扰分析结果．数值分析结果表明，干扰用户序列长度对期望用户BER能有较大影响，而期望用户所采用的序列长度对自身BER性能的影响较小。     

衰落信道下基于空时分集编码的解相关检测技术研究

多用户检测技术能够抑制小区干扰,增加系统容量,而多输入多输出(MIMO)系统可以增加系统空间分集度来抑制信道衰落,提高系统可靠性.作者在码分多址(CDMA)系统瑞利衰落信道环境下,采用MIMO多天线空间分集技术,探究解相关检测器的相关性能,并通过对不同情况下信噪比与误码率的仿真、分析和比较,实现了预期效果.     

A Novel Iterative Receiver Based on Extrinsic Information Update for MIMO Systems

A novel iterative receiver for multiple input multiple output (MIMO) systems was introduced. Its basis concept is that the reliability of extrinsic information will be strengthened with continuous iterations. Extrinsic information of present iteration is added with prior information of last iteration to obtain performance gain. The simulation results show that the improved iterative receiver can approach the 5th iteration performance of conventional soft interference cancellation (SIC)-minimum mean square error (MMSE) iterative receiver after the 2nd iteration with less computational complexity. Compared with conventional iterative receiver, the improved iterative receiver has 1dB performance gain at bit error rate (BER) of 10~ -5 , with four transmit antennas and four receive antennas system.     

New applications of EXIT chart for iterative decoding systems

Applications on iterative control and multiple input multiple output （MIMO） system were developed. Two new charts derived from extrinsic information transfer （EXIT） chart were employed as the designing tools, which are called as output mutual information chart with defined iterative degree （DID） chart and near optimum output mutual information （NOMI） chart respectively. Different from the EXIT chart, they can show the iterative performance on the whole signal-to-noise ratio range with one single curve, whereas computation complexity is greatly reduced compared with conventional bit error ratio （BER） performance curve. The iterative control was implemented according to a near-optimum iterative degree vector determined by NOMI chart, the reasonability of uncertain parameters was analyzed in one MIMO system. The concepts were illustrated based on bit-interleaved coded modulation with iterative decoding （BICM-ID）.     

A Soft Parallel Interference Cancellation Algorithm in WCDMA

A two-stage soft parallel interference cancellation (SPIC) algorithm in WCDMA system is proposed. The performance of the algorithm is analysed in perfect power control and near-far case, and the influence of the timing error on the system BER is discussed. Analysis and simulation show that the SPIC technique can enhance system capacity, and have a good ability to resist near-far impact. With its simple structure, it has good potential for practical applications.     

Admission control scheme for handover service in high-speed train communication system

Admission control in high-speed train communication system is quite different from admission control in traditional cellular networks. Conventional admission control strategies cannot be directly applied to this special communication scenario. In this paper, the problem of admission control for handover service is investigated in high-speed train communication environment. An admission control scheme considering bit error rate(BER)and bandwidth borrowing strategy is proposed. On the basis of admission control decision rule taking BER into account, a part of bandwidth obtained by compressing variable rate service in the networks is provided for handover services. The admission control scheme can admit handover services as more as possible while it guarantees the lowest data rate of different services in the networks. Simulation results show that the proposed admission control scheme has a better performance than existing admission control schemes.     

基于Simulink的Turbo码系统仿真

在Turbo码编码、译码基本理论和结构的基础上,提出了一种用Simulink构建的Turbo码编、译码可控仿真模型,并在BPSK(binary phase-shift keying)调制的高斯白噪声信道(AWGN)中进行了系统建模和仿真实验.通过研究Turbo编码、卷积编码和无信道编码方案仿真系统的BER(bit error rate)性能,结果表明,所提出的Turbo编码的误码率优于其他2种方案1个数量级以上,尤低信噪比时更具优势.     

复制窗口不等保护喷泉码的与或树渐进性能分析

采用与或树分析方法,结合算法的构造,推导出复制窗口不等保护算法中各类数据的译码失败概率迭代公式.从数学的角度验证算法性能.通过Matlab性能仿真,给出在不同复制因数下复制窗口不等保护算法与算法误比特率性能关系曲线.通过与基于权重的不等保护算法及拓展窗口喷泉码的渐进性能仿真结果进行对比,证明了该算法在相同译码开销下,可将保护级别提高3~4个数量级.此外,本文研究了复制因数对算法性能的影响,在不同的译码开销下,通过Matlab仿真给出复制因数与算法性能的关系曲线.     

Simulation and Analysis of Typical Mobile Radio Channels

In this paper, the bit error rate (BER) performance for typical mobile radio channels is simulated and analyzed based on a tapped delay line model. The investigation is focused on the propagation environments determined by the average delay profile and the Doppler spectra. The profile characteristics and their influences on channel behavior are also examined.     

A Secret Sharing Featured Secure Communication System Based on Dual Synchronization of Chaos in Colpitts Circuits

Introduction Synchronizationofchaoshasrecentlyattract-edgreatinterestbecauseofitspotentialapplica-tionsinsecurecommunications[1]andspreadspec-trumcommunications.Inasecurecommunication system,itcanbeusedforsharingtheidentical chaosinthetransmitterandreceiverasacrypto-graphiccode.Synchronizationofchaosinonewaycoupled onepairchaoticcircuitshasbeenstudiedinalarge volumeofliteratures[2-4].Inrecentyears,anew conceptofchaossynchronization,namely“dual synchronizationofchaos”,israised[5].Dualsyn-chr…