Error Performance Evaluation of Wireless Communication Systems Using Maximal Ratio Combining with Multiple Interferers

In this paper we evaluate the error performance of wireless communication systems using M-branch maximal ratio combining (MRC) with multiple cochannel interference. Three cochannel interference models are considered: (A) L independent identically distributed (i.i.d.) Nakagami-m cochannel interferers; (B) L independent cochannel interferers consisting of L-N Nakagami-m interferers and N Rayleigh interferers; (C) L independent cochannel interferers in which each interferer follows Nakagami-m distribution for a fraction of time and Rayleigh distribution for the remaining time. In addition, the desired signal assumes Nakagami-m fading. This paper considers that an exponential correlation model is assumed for the desired signals received on each branch, while the interferers are assumed independent. Closed-form expressions are derived for the probability density functions (PDFs) of the instantaneous signal-to-interference power ratio (SIR) at the output of the MRC for the three interference models. Using these SIR PDFs, further closed-form expressions to evaluate the outage probability (OTP) and the average bit error probability (BEP) of differential phase-shift keying (DPSK) are derived. Numerical results showing the impacts of the system parameters on the OTP and the average BEP are then presented.     

用于WCDMA系统的一种新型神经元MOS复数匹配滤波器

提出了一种新型神经元MOS复数匹配滤波器结构,用于实现WCDMA系统中复四相扩频调制信号的解扩运算.主要对关键电路进行了分析,与线性运算器件实现的复数匹配滤波器电路相比,具有结构简单的优点,大大降低了器件数目,HSPICE仿真结果验证了该电路结构的可行性.     

匹配滤波器同步捕获技术FPGA设计

匹配滤波器在信号检测和通信系统的同步捕获中起着关键的作用。基于软件无线电思想,分析了匹配滤波器的基本原理,采用一种可编程的分布算术式匹配滤波器同步捕获技术,可用于直接序列扩频接收机。模块采用Altera公司的FPGA Cyclone II EP2C35F672进行设计,仅占用全部逻辑资源的1%。对设计中部分功能单元进行了ModelSim功能仿真,给出了数值实验结果。     

Diversity Combining and Equalization with TCM for Wireless Communications

This paper presents an equalization structure in which antennadiversity, adaptive decision feedback equalization (DFE), interleavingand trellis-coded modulation (TCM) can be effectively combined to combatboth ISI and cochannel interference in cellular mobile radioenvironments. The feedback filter of the DFE can use either tentative orfinal decision symbols of the TCM Viterbi decoding to cancel tail ISIwith the square root Kalman algorithm. A performance bound on theaverage pairwise error probability for TCM under perfect interleavingand equalization is obtained by analysis. Some simulation results whichillustrate the potential of the proposed system will also be given. Inparticular, a performance comparison between the proposed method anduncoded QPSK modulation will be undertaken.     

Ds Signal Data Detection Using Matched Filter with Median Filter and with Transversal Filter in CW Jamming

Analysis and simulation results of a DS spread spectrum system in which data detection is based on a matched filter and a median filter are introduced. The results are compared with a simple linear interference cancellation method using a transversal filter. The probability of bit error is calculated in the AWGN channel and with continuous tone jamming when ideal autocorrelation function of the spreading code is assumed. The effect of CW jamming can be eliminated by both methods, so the comparisons are made in the AWGN channel. It is concluded that the median filter causes a loss compared with the transversal filter. The loss is about 1.2 dB when the window length is the minimum. The loss decreases as the window length increases, being, e.g., about 0.35 dB with window length 7 and 0.1 dB with length 19. Therefore, no other cancellation method is needed in data detection when the median filter is already used as an aiding device in the code acquisition process.     

DS/CDMA通信中匹配滤波器的FPGA设计

匹配滤波器因具有大的时间带宽积而在扩频和CDMA通信中受到极大重视，不仅作为快速捕获和RAKE分集等传统技术的最佳方案，而且在多用户检测、智能天线、多速率甚至是软切换等方面也都能发挥其优势；对匹配滤波器捕获的基本原理进行了研究并着重讨论了其多种FPGA实现结构。     

可变长度的数字匹配滤波器的原理与设计

数字匹配滤波器具有很强的信号处理能力，是通信系统中常用的一种部件。文中介绍可变长度的通用数字匹配滤波器的原理与设计。     

一种基于神经元MOS的直扩匹配滤波器新结构

鉴于神经元MOS晶体管的多输入信号控制以及可变阈值等特点,本文提出一种基于神经元MOS的直接序列扩频(DS)通信系统中匹配滤波器的新结构,并对其进行了MATLAB结构验证和HSPICE电路仿真。与我们前期提出的基于神经元MOS的匹配滤波器相比,新结构的匹配滤波器提高了抗干扰能力,简化了电路结构。     

双基地声呐中匹配滤波旁瓣抑制的优化方法

对于双基地声呐而言,回波信号经常会被淹没在强直达波信号的脉冲压缩旁瓣干扰中。提出了一种匹配滤波输出的旁瓣抑制方法。该方法的思想是在匹配滤波输出端设计一个FIR滤波器,使得输出的积分旁瓣电平最小,同时保持主峰输出不变。利用二阶锥凸优化算法获得了旁瓣抑制滤波器的最优解。利用数值仿真,比较了旁瓣抑制方法与常规的汉明加窗方法,结果表明,该方法可在保持输出不变的情况下,提高30 d B的旁瓣抑制性能。利用该方法设计的近中心旁瓣抑制滤波器,局部的抑制性能可达-80 d B。     

一种基于差分匹配滤波的高效捕获算法

扩频接收机系统中,载波的捕获是衡量系统性能的重要指标。当系统接入多路叠加并行信号时,若需要在二维对信号进行捕获,所需捕获时间、所耗资源和接收机功耗将成倍增加。文中针对此问题,提出了一种基于差分滤波器的分集接收方案,大幅降低了系统资源的占用,从而减少了功耗、成本和捕获时间。利用伪随机码的双极性和差分滤波结构减少了所用加法器的数量,并结合对伪随机码并行分集的结构,在多路中对滤波结果进行复用。通过对传统快速相关捕获算法、快速捕获算法、频率相关法以及文中基于差分滤波的并行分集结构进行了复杂度对比。其结果显示,基于差分滤波的并行分集结构在节省资源、提高效率上均具有较大优势。     

An Improved Switched Diversity Combining Using Fuzzy Adaptive Control

Diversity combining techniques, due to their extreme effectiveness incounteracting fading effects in wireless environment, have been extensivelystudied in recent years. In this paper, we propose an improved switchedcombining scheme using fuzzy adaptive control, namely, fuzzy adaptive switcheddiversity (FASD), which is applicable for implementation at mobile units.Specifically, the fuzzy adaptive control dynamically adjusts the thresholdlevel, at which switching is performed, based on the present varying channelconditions. By incorporating the statistics of mobile fading channels andextensive simulations, we have achieved an effective system design of FASDwhich has a significant improvement in system performance in terms of both thediversity gain and BER (bit error rate), while maintaining reasonablesimplicity in implementation.     

基于Simulink的匹配滤波器设计与实验

针对“匹配滤波器”教学内容中缺乏相关课程实验与实现的教学环节,基于Simulink仿真平台搭建了二进制确知数字信号的匹配滤波型最佳接收机架构,并采用了四种传输函数进行对比验证。这一实验教学活动的引入有助于增强教学内容的趣味性,激发学生的学习热情,使原本抽象且枯燥的知识点变得具体、生动形象,加深了学生对匹配滤波器原理的理解与应用。     

无线通信系统中发射分集技术研究

在无线通信系统中,不同场景下有不同的传播模型。为了研究发射分集技术对抗多径效应的性能,文中总结了无线通讯系统中室外场景下的传播模型。针对传统的Okumura-Hata传播模型来研究不同环境下发射信号的功率损耗,在接收端计算各信号副本的接收功率,通过与预设的接收功率门限作比较,得出每个信号副本以及各副本等增益合并后的信号可用性,从而研究发射分集对于信号可用性的提升作用。仿真结果表明,分集技术能明显提升接收机接收信号的可用性。     

用计算全息制作改进的Mexican-hat子波匹配滤波器实现二维光学子波变换

提出了应用计算全息制作改进的Ｍｅｘｉｃａｎ－ｈａｔ子波匹配滤波器,在一个光学４ｆ系统中实现了二维子波变换,给出了简要的理论分析和实验结果,实验结果与计算机模拟完全一致。     

传输分集技术在第三代移动通信系统中的应用

本文首先分析了衰落信道中采用分集技术时卷积编码Viterbi软判算法的性能,指出具有独立衰落特性的分集信道数越多,接收的性能越好.并给出了采用不同的分集技术时系统性能的仿真结果,结果表明采用传输分集技术可以明显提高前向链路的性能,而不增加移动终端的复杂度.传输分集是一种有效可行的对抗衰落的技术,有望在第三代移动通信系统中得到广泛应用.     

自适应滤波在扩频信号分集接收中的应用研究

使用自适应滤波器完成对扩频信号的扩频码捕获后,传输信道中由于信号衰落造成的多径信号的幅度就可以从自适应滤波器收敛后的系数权值向量上体现出来.根据分集接收的理论分析,依据多径信号的信号幅度值进行分集接收在理论上是可行的,因此利用自适应滤波器对接收到的多径信号进行隐分集接收是完全可行的.使用自适应滤波器在完成扩频码捕获的同时,在不增加额外硬件支路的情况下就可以实现对多径信号的分集接收功能,从而改善在多径衰落环境下的信道传输性能.     

Space-Time Optimum Combining for CDMA Overlay for Personal Communications Systems

The requirement to suppress narrowband interferences in CDMA communication stems from the overlay concept, i.e., coexistence of different types of signals in the same frequency band. This paper describes the performance analysis of a direct-sequence (DS) CDMA personal communication system sharing a common spectrum with narrowband microwave radio links in the 1.85 to 1.99 GHz band. The coexistence of these two systems within the same frequency band will improve the overall spectrum efficiency, but will also cause interference to both systems. In this paper it is shown that joint spatial and temporal optimum combining provides an efficient means of improving the performance of the DS-CDMA system through cancellation of the narrowband signal and the co-channel interferences. The proposed space-time architecture provides degrees of freedom for both diversity and interference cancellation. It is shown that the joint space-time receiver is robust with respect to the narrowband interference signal bandwidth and its carrier frequency offset from the DS-CDMA carrier frequency.     

A Protocol for Multimedia CDMA Personal Communication Networks

In this paper, a joint CDMA/TDMA protocol has been proposed for integratedvideo-phone/voice/data traffic in personal communication networks (PCN). Thevideophone service is implemented according to H.261 standard. The concept ofdynamic boundary is adopted in both code and time domains to meet thedifferent requirements for videophone, voice and data traffic.Two mathematical analysis methods are adopted to evaluate the systemperformance. One is the traditional Markov analysis (TDMA), which is used tocalculate the average videophone and voice call blocking probabilities. Theother is Transient Fluid Analysis (TFA), which is adopted to evaluate the datadelay and channel utilization performance. Results show that two dynamicboundaries can be adjusted to achieve the optimal system performance, andsuggestions of how to adjust these boundaries are also given.     

存在同信道干扰和多用户分集的多蜂窝系统性能分析

考虑存在来自其他蜂窝的不同功率同信道干扰的多用户上行链路,分析了基站采用多用户调度和最大比合并接收时的系统性能.在期望信号和干扰信号分别为Nakgami-m和Rayleigh时,运用基于概率密度函数的性能分析法推导了系统中断概率和平均误符号率(ASER)的闭合表达式.仿真结论显示,系统中断概率和ASER的解析曲线与数值仿真结果一致,系统性能随着天线数和用户数的增大而提升,多天线和多用户分集增益明显,干扰功率有较大差异时系统中断概率性能有所下降.