clear;

clc;

% 1.產生長度為2000的0/1隨機序列，進行BPSK調制，通過沖激響應為h[1,0.8,0.3]的信道傳送，信道的高斯噪聲為20dB。

%用LMS算法進行均衡輸出，均衡抽頭數為8，步長為0.03，訓練序列長度為200。

% 2.繪制出星座圖顯示理想信號、均衡器輸入信號、均衡器輸出信號。

% 繪制出重復20次實驗的瞬時誤差平方的統計平均收斂曲線。更改LMS算法步長和抽頭個數，觀察瞬時均方收斂曲線有什么變化。

% 分析步長因子和抽頭個數變化對LMS算法性能的影響。

N = 2000;M = 2;weight = 8;stepSize = 0.03;trainLen = 200;

g = randi(2,N,1) - 1;

cp = [];mod1 = [];f = 0.1 * 3 * pi;t = 0.19;

for n = 1 : length(g)

if g(n) == 0

A = zeros(1,20);

else

A = ones(1,20);

end

cp = [cp A];

c = cos(f*t);

mod1 = [mod1 c];

end

figure(1);

subplot(3,1,1);

plot(cp);

axis([0 200 -1 2]);

subplot(3,1,2);

plot(mod1);

axis([0 200 -2 2]);

cm = [];mod = [];

for n = 1 : length(g)

if g(n) == 0

c = cos(f*t + pi / 2);

else

c = -cos(f*t + pi / 2);

end

mod = [mod c];

end

subplot(3,1,3);

plot(mod);

axis([0 200 -2 2]);

figure(2);

subplot(4,1,1);

plot(mod);

axis([0 200 -2 2]);

mod = awgn(mod, 20);

subplot(4,1,2);

plot(mod);

axis([0 200 -2 2]);

%h = [1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0.599971];

%h = [0.734189,0,0,0,0,0,0,0,0,0,0,0,0,1,-0.406511,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0.295130];

h = [1,0.8,0.3];??%沖激響應為h[1,0.8,0.3]的信道傳送

rxsig = conv(mod.',h);

subplot(4,1,3);

plot(rxsig);

axis([0 200 -2 2]);

eqlms = lineareq(weight,lms(stepSize));

eqlms.RefTap = 1;

y = equalize(eqlms,rxsig,mod(1:trainLen));

subplot(4,1,4);

plot(y);

axis([0 200 -2 2]);

hold on;

modmsg = pskmod(g,M);

filtmsg = conv(h,modmsg);

eq1.SigConst = pskmod([0,M - 1],M);

[symbolest,yd] = equalize(eqlms,filtmsg,modmsg(1:trainLen));

h = scatterplot(filtmsg,1,trainLen,'rx');

hold on;

scatterplot(symbolest,1,trainLen,'g.',h);

scatterplot(eq1.SigConst,1,0,'k*',h);

legend('Filtered signal','Equalized signal','Ideal sinal constellation');

hold off;

總結

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