通信原理 移动通信实验 信道程序版本二

一、高斯信道的模拟matlab仿真

程序如下： clear,clc; N=0:1000; fs=1024;

t=N./fs; y=3*sin(2*pi*t); x=wgn(1,1001,2); i=y+x;

% i=awgn(y,2);

subplot(3,1,1),plot(x); subplot(3,1,2),plot(y); subplot(3,1,3),plot(i)

图1 高斯白噪声的仿真结果

二、信噪比与误比特率关系matlab

x=0:15; y=x;

FrequencySeparation=24000; BitRate=10000; SamplesPerSymbol=2; Velocity=40; LightSpeed=3*10^8; Frequency=825*10^6;

WaveLength=LightSpeed/Frequency; Fd=Velocity*10^3/3600/WaveLength;

hold off;

for i=1:length(x); SNR=x(i); Sim('untitled3'); y(i)=mean(BitErrorRate); end

Semilogy(x,y); hold on;

图2 高斯白噪声信道下误码率与信噪比曲线

三、 瑞利分布的概率分布密度图示

图3 瑞利分布的概率分布密度

四、瑞利信道仿真

clc; clear; fc=2*10^9; v=110;

c=300*10^6; fm=fc*(v*10^3/3600)/c; N =128;

gap = 2*fm/(N-1); T = 1/gap;

sf0 = 1.5/(pi*fm); for n = 1:(N-2)/2

sf(n) = 1.5/(pi*fm*sqrt(1-(n*gap/fm)^2)); end

SEf = [fliplr(sf),sf0,sf]; figure(1); plot(SEf);

title('多普勒功率谱'); xlabel('f'); ylabel('size'); grid;

x1=randn(1,N); x2=randn(1,N); x=x1+1i*x2;

pha=2*pi*rand(1,N); i= linspace(1,N,N); sigma=sqrt(var(x)/2);

syms t;

tt=linspace(0,0.35,N); ci=sigma*(2/N).^0.5;

fi=fm.*sin(pi/(2*N)*(i-1/2)); ph=2.*pi.*fi*t+pha; Tc1=ci.*cos(ph); Ts1=ci.*sin(ph); Tc2=sum(Tc1); Ts2=sum(Ts1); Tc=subs(Tc2,t,tt); Ts=subs(Ts2,t,tt);

st=Tc.*cos(2*pi.*tt)-Ts.*sin(2*pi.*tt); rt = sqrt((real(Tc).^2 + real(Ts).^2)); % rt=sqrt(Tc.^2+Ts.^2) rt_db=20*log10(rt); st_db=20*log10(st); figure(2); plot(tt,rt_db); % axis([0 20 0 100]); title('瑞利衰落信道'); xlabel('t'); ylabel('dB'); grid; figure(3) n=0:0.1:10;

r=sqrt(sigma*(x1.^2+x2.^2)); h=hist(r,n);

fr_approx=h/(0.1*sum(h)); pijun=sum(r)/N;

junfanghe=(r-pijun).^2; junfang=sum(junfanghe)/N; u=0;

cdf=raylcdf(n,sigma); subplot(3,1,1); plot(n,cdf); title('CDF');

pdf=raylpdf(n,sigma); subplot(3,1,2); plot(n,pdf); title('PDF'); hold on;

plot(n,fr_approx,'ko'); axis([0 8 0 1]) wucha=fr_approx-pdf; subplot(3,1,3); plot(n,wucha); title('误差');

R=raylrnd(sigma,1,1000); E=mean(R);

D=cov(R); figure(4) plot(Tc,'.');

title('时域高斯信号(Tc)'); xlabel('N'); ylabel('正交信号'); grid; figure(5) plot(Ts,'.');

title('时域高斯信号(Ts)'); xlabel('N'); ylabel('正交信号'); grid;

瑞利衰落信道1050-5dB-10-15-20-2500.050.10.15t0.20.250.30.35

多普勒功率谱0.020.0180.0160.0140.0120.010.0080.0060.0040.002size0204060f80100120140