理论-信道建模

Mr.Wenxin2025年4月1日大约 4 分钟

理论-信道建模

https://ww2.mathworks.cn/discovery/channel-model.html

By using channel models with your wireless system design in MATLAB® and Simulink®, you can optimize link performance, perform system architecture tradeoffs, and provide a realistic assessment of the overall system performance.

通过在 MATLAB® 和 Simulink® 中将信道模型与无线系统设计结合使用，您可以优化链路性能、执行系统架构权衡，并对整体系统性能进行实际评估。

1.依照性质分类

Path loss 路径损失
路径损耗信道模型表示传输信号穿过无线介质时的功率降低。它们不对信号执行任何过滤。这些通道模型基于信号传播的介质，例如自由空间、雨、雾或气体。您可以使用 MATLAB 中的 fspl 函数来计算通信链路的自由空间路径损耗。
Purely stochastic 纯随机
纯随机信道模型可解决热噪声生成和多径衰落信道问题。它们不需要任何关于正在建模的链路的几何形状的知识。加性高斯白噪声 (AWGN) 通道对接收器前端中的电子噪声进行建模。
awgn
Spatial 空间分集
现代无线系统通常使用波束成形将能量引导至所需的接收器并远离干扰源
这些信道模型可以预测无线系统中信号的出发角 (AoD) 和到达角 (AoA)。这些模型通常定义将传输信号反射到接收器的散射体。
The WINNER II channel model is one such spatial channel model (SCM), and it utilizes a cluster delay line (CDL) to model individual links and multi-link systems.
Ray tracing 射线追踪
当空间通道模型没有明确指定散射体的位置时，光线追踪通道模型会明确指定散射体的位置。他们使用精确的建筑物位置信息来生成室外通道模型，并使用精确的房间信息来生成室内模型。射线追踪分析的输出之一是脉冲响应，可用于过滤输入信号。
raytrace

2. 重要性

They are essential to predict link performance (e.g., BER) in a single-user scenario.
They are crucial to predict system performance (e.g., throughput, latency) in a multi-user scenario.
They reduce the need for costly channel measurement projects.

3. 实际分类

3.1 路径损耗

3.2 纯随机

AWGN
Multipath Fading Channel 多径衰落信道
WLAN Channel
LTE
5G TDL

3.3 空间

3.3 光线追踪

4.AWGN

介绍：https://ww2.mathworks.cn/help/comm/ug/awgn-channel.html
函数：https://ww2.mathworks.cn/help/comm/ref/awgn.html

Y = awgn(X,snr,signalpower) ;
%accepts an input signal power value in dBW. 

Y = awgn(X,snr);
%assumes that the power of X is 0 dBW

5. Multipath Fading Channel 多径衰落信道

https://ww2.mathworks.cn/help/comm/ug/fading-channels.html#bq5zk36
https://ww2.mathworks.cn/help/comm/ug/multipath-fading-channel.html

5.1 延迟与衰减

sampleRate500KHz = 500e3;    % Sample rate of 500 KHz
sampleRate20KHz  = 20e3;     % Sample rate of 20 KHz
maxDopplerShift  = 200; % Max Doppler shift of diffuse components (Hz)
delayVector = (0:5:15)*1e-6; % Discrete delays of four-path channel (s)
gainVector  = [0 -3 -6 -9];  % Average path gains (dB)

maxDopplerShift=v\times f/c

the maximum Doppler shift of 200 Hz (as above) corresponds to a mobile speed of 65 mph (30 m/s) and a carrier frequency of 2 GHz.

按照惯例，第一路径的延迟通常设置为零。
对于后续路径，1 微秒的延迟对应于 300 m 的路径长度差异。
一般情况，平均路径增益随延迟呈指数衰减（dB 值线性衰减），但具体延迟分布取决于传播环境。
在上面指定的延迟曲线中，我们假设路径延迟每 5 微秒，平均功率就会降低 3 dB。

5.2 控制莱斯通道系统对象

KFactor = 10;           % Linear ratio of specular to diffuse power
specDopplerShift = 100; % Doppler shift of specular component (Hz)

The Doppler shift of the specular component is typically smaller than the maximum Doppler shift ( maxDopplerShift ) and depends on the direction of travel of the mobile relative to the direction of the specular component.
The K-factor specifies the linear ratio of average received power from the specular component relative to that of the associated diffuse components.

5.3 创建信道对象

% 瑞利信道
rayChan = comm.RayleighChannel( ...
    SampleRate=sampleRate500KHz, ...
    PathDelays=delayVector, ...
    AveragePathGains=gainVector, ...
    MaximumDopplerShift=maxDopplerShift, ...
    RandomStream="mt19937ar with seed", ...
    Seed=10, ...
    PathGainsOutputPort=true);
% 莱斯信道
ricChan = comm.RicianChannel( ...
    SampleRate=sampleRate500KHz, ...
    PathDelays=delayVector, ...
    AveragePathGains=gainVector, ...
    KFactor=KFactor, ...
    DirectPathDopplerShift=specDopplerShift, ...
    MaximumDopplerShift=maxDopplerShift, ...
    RandomStream="mt19937ar with seed", ...
    Seed=100, ...
    PathGainsOutputPort=true);

6. MATLAB实现

https://mp.weixin.qq.com/s/l3zNh8F14u_UjVaJsV1J2Q

贡献者

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