短波信道模拟的计算机仿真

在通信系统的仿真中,信道模拟器对真实信道的逼近程度,直接影响到通信系统仿真所得性能参数的有效性。因而,开发性能良好的短波信道模拟器是十分必要的。详细叙述了短波电离层信道Watterson模型的原理,根据军标所给短波信道参数,提出了具体的短波信道模拟器实现方案,并给出了计算机仿真结果,较好地模拟了短波信道的时间选择性衰落特性和频率选择性衰落特性。     

短波电离层反射信道模型的建立与仿真

工作在短波波段的电子战设备进行天波通信时,会受到电离层高度变化和多径传播的影响,使信号产生多普勒展宽和多径时延,表现为时间选择性衰落和频率选择性衰落,严重影响信号质量.本文介绍了短波电离层反射信道对信号的影响,推导出信道的理论模型,提出了实现方案,并利用systemview进行了信道仿真,结果表明,该模型基本上反映了短波信道的特点.     

一种话音带宽的短波信道模拟器的设计与实现

文中介绍了话音带宽条件下一种基于 DSP 平台的短波信道模拟器的设计与实现,该模拟器采用Watterson 模型,不仅可以模拟短波信道的主要特点,如多径传输、瑞利衰落、多普勒频移等,而且实现了对传输信号的全数字化实时处理。     

基于谐波叠加的短波信道模拟器设计

在基于Watterson模型的短波信道模拟器设计中,常采用滤波法实现短波信道的多普勒扩展和衰落,其运算复杂度较高。给出一种新的短波信道模拟器实现方法,采用谐波叠加法设计抽头增益函数,模拟短波信道的多普勒扩展和衰落,有效降低了运算复杂度。最后,采用单音信号对信道模拟器多径？多普勒扩展和多普勒频移等性能进行了仿真,仿真结果证明了用谐波叠加法设计短波信道模拟器的有效性。     

基于多站观测的短波电离层信道一致性与相参性研究

对分布式短波雷达系统与短波时差定位而言,短波电离层信道特性参数的一致性与相参性是需要重点考虑的因素. 本文利用自主设备在武汉、道孚、乐山三处初步开展了同步组网的多站短波电离层信道斜向探测实验. 结果表明,太阳地磁活动平静期间,武汉-道孚、武汉-乐山两条相近链路信道群距离日变化、群距离展宽、多普勒频移、多普勒展宽等相关特性的统计特征基本相同,道孚、乐山接收到的武汉所发信号经电离层传播后仍可得到明显的相关峰,并同时具有线性相位变化规律和稳定的相位差. 研究表明,在相距不远的范围上,临近的短波电离层信道可以有着较好的参数一致性和相参性.     

基于Watterson模型的短波信道仿真

短波信道是一种典型的时变参数信道,短波信道的建模仿真在短波通信系统研究中具有重要的意义,本文从分析比较经典的Watterson信道模型着手,仿真分析并讨论了短波电离层传输的时变传输多径、多普勒频移和多普勒频扩等性质。     

一种低复杂度信道模拟器的设计

针对TD-LTE射频一致性测试系统专项的需求及通用信道模拟器设计周期长、复杂度高的现状,研究了影响无线信道特性的路径损耗、阴影衰落、多径多普勒效应和高斯白噪声等因素,并相应提出了一种新的计算正余弦函数方法和高斯白噪声产生方法。通过信道理论建模、Matlab链路搭建进行模型优化分析以及基于Xilinx公司Virtex-6芯片的模型FPGA实现,得到了一种简单有效的信道模拟器。实验表明,用TD-LTE基带信号作为激励,该信道冲激响应与Matlab理论值误差在2‰之内,且模型不涉及SCM、WINNER等模型天线方向图、多链路等高复杂度模块,说明该信道模拟器具有简便性和可靠性。     

移动通信设备中的多信道选取模型设计与改进

传统的设备信道选取模型分析方法复杂、模型模拟器电路过于简化,应加以改进。提出并设计一种移动通信设备多信道选取模型并改进。介绍模型模拟器的组成以及仿真原理,通过改变移动通信距离偏角并添加白噪声,排除模型中的多普勒效应和通信噪声。改进模型模拟器A/D电路中的可控增益放大器,提高多信道中信号的干扰排除操作强度。用分布式计算系统替换原模型中的密集型计算系统,提高模型计算精度。实验结果表明,改进后的模型取得了更高的电平过载率和更短的衰减时间。     

时变多普勒衰落信道硬件模拟的FPGA实现

针对不同散射环境下衰落信道具有不同的多普勒功率谱形状,提出了一种改进的复谐波叠加模型用于时变多普勒衰落信道的模拟,仿真分析了该方法输出信道衰落的幅值及相位连续性,并据此设计了基于FPGA硬件平台的时变多普勒衰落信道模拟器。硬件实测结果表明,该模拟器输出的时变多普勒功率谱与理论仿真非常吻合,可用于实际中多普勒功率谱实时变化场景的模拟。     

卫星移动通信信道特性与模型研究

从多径效应、阴影效应、多普勒效应和电离层闪烁等方面具体分析了卫星移动通信信道传输特性,并从单状态统计模型和多状态统计模型两方面详细介绍了瑞利信道模型、莱斯信道模型、对数正态衰落信道模型、Loo模型、Corazza模型、Lutz两状态信道模型和五状态M arkov信道模型,最后对未来卫星移动通信信道模型研究做了展望。     

Real-Time HF Channel Parameter Estimation

An efficient real-time realization for the estimation of the HF channel parameters is presented and the estimation errors are evaluated. The parameters that were chosen are the Doppler spread, multipath spread, Doppler shift and signal-to-noise ratio, which are the dominant ionospheric propagation parameters. The estimation procedures were real-time implemented on a digital signal processor and tested on a real-time HF channel simulator based on the so-called Watterson model. The estimated parameters can be used in numerous ways in adaptive HF communication setups, including real-time channel quality evaluation for link or equipment adaptation.     

On the Capacity of Mid-latitude High Frequency Ionospheric Channel

In this paper we consider the theoretical characterization of the ionospheric transmission. More accurately, we derive a closed form expression of the average capacity for Mid-latitude High Frequency (HF) ionospheric channels. Heretofore, this problem has been studied for Rayleigh channels when each tap of the impulse response has a Rayleigh distribution without characterizing the variance of this distribution. In this paper, we extend these works to HF ionospheric channels by evaluating the variance of the amplitude attenuation versus the Doppler spread and then the channel capacity. For a multipath HF ionospheric channel, we model the Doppler phenomenon as a Gaussian profile which is suggested for HF environments. Finally, we derive a closed form expression of the average channel capacity using the probability density function (pdf) of the instantaneous impulse response. Numerical results on both simulated and real measured data are derived at the end of the paper.     

基于Watterson模型的短波信道实时软件模拟

针对短波信道多径、衰落、多普勒频移及扩展等特点，设计了一种基于Watterson模型的短波信道模拟器，该模拟器采用全软件实现，具有简单易行、可移植性强、费用低等优点，并可实时嵌入到调制解调器中。通过对仿真中关键技术进行改进，提高了系统性能。仿真结果验证了该模拟器的有效性。     

The Calculation of Ionospheric Doppler Spread on HF Communication Channels

Using some basic concepts of ionospheric propagation, multipath and Doppler spread calculations are obtained for the HF ionospheric communication channel. Because of sensitivity to the solar control mechanism, the Doppler spread results are found to demonstrate a pronounced dependence on time of day and operating frequency. The practical consequences of these calculations are discussed in detail. This includes the definition and generation of the "Doppler reduction factor," comparable to the "multipath reduction factor," which can be used to determine the appropriate operating frequency on a given HF link.     

基于Watterson模型的短波航空移动信道建模与仿真

信道建模与仿真是短波航空通信系统性能分析评估的基础,该文通过分析研究飞行器最大移动速度、加速度、机动频率、运动轨迹等机动状态参数对短波航空移动信道时变多普勒频移的影响,提出一种基于Watter-son模型的短波航空移动信道模型.该模型能够充分描述由收发两端相对运动引入的信道多普勒频移与扩展,适用于短波超视距航空移动通信...     

改进Watterson模型的无人机短波信道仿真

Watterson模型是多年来仿真短波信道的标准表示方法,其对短波信道多径时延、多普勒扩展、多径增益等特性都有全面的描述。针对无人机短波通信信道的特点,结合无人机的各种不同飞行状态,提出一种改进的Watterson模型,并在Simulink软件平台上对改进模型进行了仿真验证,仿真结果主要分析了不同飞行状态对短波通信性能的影响。在当前没有权威实测数据的情况下,对无人机等高速移动通信的信道衰落研究具有重大意义。     

A Discrete-Time Channel Simulator Driven by Measured Scattering Functions

In-situ measurements of the scattering function are used to drive a channel simulator developed in the context of underwater acoustic telemetry. Two operation modes of the simulator are evaluated. A replay mode is accomplished by interpolation of measured impulse responses. A second, stochastic mode delivers multiple realizations of a given scattering function. The initial assumption of wide-sense stationary uncorrelated scattering is violated by strong phase correlations between taps. It is shown that time-varying Doppler shifts due to platform motion must be eliminated from measured scattering functions in order to provide the stochastic tap gains with the true Doppler spectrum of the channel. The simulator is validated through a comparison of acoustic data measured at sea, and emulated data, governed by the same scattering function. This comparison is based on scattering and coherence functions, multipath phase measurements, and application of a decisionfeedback equalizer. After the Doppler correction, the synthetic data are indistinguishable from the acoustic data in terms of delay-Doppler spread, temporal coherence, phase behavior, equalizer mean square error, and bit error ratio.