移动通信中的无线信道技术

从移动无线信道的时变冲激响应的功率密度谱函数和相关函数出发,研究广义平稳非相关散射(WSSUS)无线信道特性的统计参数,对无线移动衰落信道的特性进行了分类。分析了无线通信中影响移动无线通信信号传输质量的原因,对提高移动通信质量的可行性提供参考。     

移动通信中无线信道特性的研究

从等效低通信道的时变冲激响应的相关函数和功率密度谱函数出发,研究了一些描述广义平稳非相关散射(WSSUS)的无线信道特性的统计参数,并对无线移动衰落信道的特性进行分类。分析了3种常见的小尺度多径衰落信道的统计模型,给出了在平坦衰落信道中系统传输比特误码率的一般分析方法。最后,利用这些模型和方法,给出了一些常见数字调制信号的传输误码率的数值结果。结果表明：衰落对无线移动通信系统传输性能的影响是很大的,在实际中应设法消除它。     

无线信道

与有线通信中良好的信道状况(一般可以用加性白色高斯噪声信道来仿真)完全不同，移动通信中的无线信道状况非常恶劣，信道是多径、时变的，从而使无线信号在短时间或短距离传播后幅度快速衰落。即产生小尺度衰落现象。     

无线信道的可视化建模和仿真

无线信道是移动通信的传输媒体,研究其特性并建立一个与实际传输环境相符合的无线信道仿真模型都有着十分重要的现实意义。本文首先提出无线多径衰落信道的广义平稳非相关散射（Wide-Sense Stationary Un-correlated Scattering,简称WSSUS）假设,并在该假设下对该信道的计算机仿真模型进行了研究;最后选择MATLAB6.X的仿真工具箱SIMULINK作为图形建模的支持环境,对多径无线信道的冲激响应进行可视化建模和仿真。     

无线寻呼网的同播研究

本文建立一个两基站的模式研究无线寻呼网的同播信道特性，证明其信道是平坦衰落信道，具有较小的时延差，指出深衰落可能发生的区域及条件。移动通信技术     

移动通信衰落测试解决方案

1 概述 移动通信系统的性能主要受到无线信道的制约。收发系统之间的传播路径损耗非常复杂：视距、衰落、多径和随机变化是无线信道的基本特征。衰落信道作为移动通信中的环境条件,对通信系统的影响非常显著甚至是具有决定性的作用。因而对于不同衰落特性的仿真是在各种环境中评估系统性能的基本要求。为了满足移动通信系统的测试要求,实际测试中我们需要衰落模拟器来模拟真实的信道类型。     

OFDM-ROF下行链路的性能研究

OFDM技术与ROF技术结合为实现低成本、高速数据传输的移动网络提供了可能,但光纤链路的非线性以及无线信道的多径衰落降低了系统性能。在建立ROF下行链路的传输函数模型基础上,分析ROF下行链路对OFDM信号性能的影响。传输模型包括激光器,光纤链路以及无线信道。分析在不同光调制指数、光纤长度及无线多径信道下接收信号的误差矢量、三阶非线性失真和互调失真。仿真结果显示：随着调制指数、光纤长度的增加,以及无线信道的多径衰落使得接收信号性能下降。此分析为OFDM-ROF下行链路的线性化以及无线信道均衡方案选择提供了理论基础。     

无线信道中的电波传播

分析了信号在无线信道中传输时所经受的两种衰落,介绍了主要的无线传播模型,在此基础上提出了对抗衰落的措施。     

基于无线移动通信的信道研究与仿真分析

本文详细讨论了无线移动通信系统中的信道性能及信道模型的仿真方法.重点讲述了多径衰落信道的原理及其数学模型的构造,并给出了一个基于简单多径信道模型的QPSK系统性能的仿真结果,总结了不同参数的多径衰落对无线移动通信系统性能的影响.     

无线视频通信中信道特性的研究

在无线视频通信中，无线信道环境的好坏将直接影响到通信质量，信号传输中的带宽．波动、高误码率和接收的异种性为视频通信系统的设计带来了极大的困难。讨论了无线信道电波传播的特性，给出了无线时变衰落信道的模型并分析了视频传输的信道失真，为复杂无线环境下的视频通信系统的设计提供了理论依据。     

W-CDMA无线多媒体通信系统设计考虑

为了研究和开发第三代移动通信系统,进行Ｗ－ＣＤＭＡ 无线多媒体通信系统和技术的研究十分必要。针对我们个人通信与扩频实验室正在研究开发国家８６３ 高技术通信主题Ｗ－ＣＤＭＡ无线多媒体通信技术的实验系统,我们提出了Ｗ－ＣＤＭＡ无线多媒体通信系统的系统结构,系统信道配置和功能安排,Ｗ－ＣＤＭＡ通信方式,分析了信号调制解调的性能,提出信号功率控制方法。     

无线移动通信中的OFDM系统参数设计方法

基于OFDM系统工作原理和无线移动通信信道时频二维衰落特性，研究OFDM系统的参数（包括子载波个数和循环前缀长度）设计准则，并用一个设计实例和仿真结果加以验证说明。研究结果可为OFDM系统的设计提供理论依据。     

Simulation of mobile fading channels

Many aspects of a mobile radio system are basically determined by the propagation characteristics of the channel. Therefore, an understanding and good knowledge of mobile radio channels is essential for the analysis, design, and operation of wireless systems. It allows the successful development, evaluation, and testing of any current or future communication system, whether it is for cellular mobile telephony, for radio paging, or for mobile satellite systems. This article tries to present a simple and efficient way to simulate mobile channels for development and testing of mobile wireless systems, using some of the commercial circuit-analysis and simulation programs. So, in parallel with an overview of fading-channel propagation mechanisms and aspects, compact simulation models are given that can effectively be used for further analysis and understanding of the operation of mobile fading channels.     

Statistical analysis of mobile radio reception: an extension of clarke?s model

Statistical analysis and modeling of wireless channels is essential to wireless communication systems. Clarke?s model [1] and the corresponding statistical analysis of mobile radio reception has been widely accepted in numerous wireless applications. Since the component phases in Clarke?s model are assumed to be constant in time, the well-known results of statistical analysis based on this model, such as the autocorrelation and Doppler power spectrum, are not appropriate to describe real wireless channels for which the random environments (radio propagation paths) are time-varying and accordingly for which the channel is non-constant in the absence of Doppler frequency shift. In this paper, we extend the traditional Clarke?s model incorporating the effect of fluctuations in the component phases, and perform the statistical analysis which results in a closed-form expression of the autocorrelation of the fading. The theoretical power spectral density function, which is the Fourier transform of the resultant autocorrelation of the fading, is shown to fit the practical measured spectra, which is in contrast to the traditional theoretical flat fading channel spectra (Jakes? spectrum in [2]). The proposed model and statistical results should have important implications for detailed spectral analysis and channel simulations for real wireless communications systems in random fluctuating electromagnetic propagation environments.     

基于网络编码的系统中断性能分析

在无线通信中,信道的衰落会降低信号传输的可靠性,影响通信质量。协同分集技术作为一种对抗衰落的有效手段,能提高无线通信性能,已经得到了广泛的研究和应用。为了更有效地利用信道资源,本文提出了基于机会式网络编码的协同机制。在两个节点A和B与一个中继节点R相互协同向基站D发送数据的仿真场景下,研究非协同通信机制、传统协同通信机制和机会式网络编码的协同通信机制下的系统中断概率。理论分析和系统仿真表明,当节点A与B之间的链路以及节点A,B到中继R的链路存在衰落的情况下,机会式网络编码的协同策略具有较好的性能。      

Analysis on characteristics of aeronautical wireless channels

In aeronautical mobile communication systems, wireless channels characteristics are different in scenarios of Parking, En-Route, Taxi, and Arrival/Take-off. By considering fading types, power spectrum density and delay characterization of aeronautical wireless channels, typical parameters of aeronautical wireless channels model are investigated to analyze characteristics of aeronautical wireless channels.     

Marine Mobile Wireless Channel Modeling Based on Improved Spatial Partitioning Ray Tracing

In 5G era,it is expected to achieve wireless network coverage including offshore areas.Modeling of marine wireless channels is the basis of constructing a marine communication system.In this paper,a communication scene between an unmanned aerial vehicle(UAV)and a boat is simulated to study the marine wireless channel.Firstly,an improved spatial partitioning ray tracing algorithm is proposed to track the propagation path of electromagnetic waves at sea surface.Secondly,a mobile channel is simulated and modeled based on the track results.Finally,a loss measurement is carried out in the coastal waters based on the simple wireless channel loss measuring platform,and a path loss propagation model is built.Then we compare the actual measurement data with the simulation results and find that the two are have good consistency,which further verifies the reliability of the simulation.     

不同衰落下的并行信道建模与容量分析

无线信道的分析与建模是无线通信研究的基础的工作,信号在传输过程中会受到不同衰落环境的影响,例如频率选择性衰落、时间选择性衰落和空间选择性衰落。为了分析无线传播环境在这三种衰落条件下的信道特性,分别对三种衰落信道进行并行信道建模,在此基础上将注水原理分别应用于这三种衰落信道中,即分别在频率、时间和空间上进行最佳功率分配,只对信道状况良好的子信道分配功率,最后得到不同衰落信道下的信道容量。