matlab 计算误码率,关于误码率的问题 急！！！！！ -ag凯发k8国际

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求助各位大佬

要求是2ask调制 通过滚降系数为0,0.5,1的升余弦滚降滤波器，信道加入1-15db的高斯白噪声，

相干解调，匹配滤波后计算出误码率与信噪比的关系图与理论值拟合。

现在问题是计算出的误码率过高无法拟合，请教各位大佬应该怎么修改。明天就要交论文了 曲线一直拟合不上

好急

%%---baseband signal parameters---%%

d_r = 32e3; �te rate = 32kbps

p_d = 1/d_r; %pulse duration

%signal generation

bits = 16;

rand_data = randi([0 1], 1,16);

input = repmat(rand_data',1,2000)';

input = input(:)';

t = linspace(0,bits,numel(input));

figure(1);

subplot(3,1,1);

plot(t,input);

title('input bit stream');

xlabel('samples');

ylabel('amplitude');

grid on

%�rrier generation

fc = 10;

carrier = cos(2 * pi * fc * t);

subplot(3,1,2);

plot(t,carrier);

title('carrier');

xlabel('samples');

ylabel('amplitude');

grid;

%%raised cosine rolloff filter

%%rolloff = 0

rolloff = 0;

span = 20;

sps = 50;

rcosfilter_1 = rcosdesign(rolloff, span, sps,'sqrt');

shapedsignal_1 = conv(input,rcosfilter_1,'same');

figure(2)

subplot(3,1,1);

plot(t,shapedsignal_1);

title('shaped signal rolloff = 0');

xlabel('samples');

ylabel('amplitude');

rolloff = 0.5;

span = 20;

sps = 50;

rcosfilter_2 = rcosdesign(rolloff, span, sps,'sqrt');

shapedsignal_2 = conv(input,rcosfilter_2,'same');

subplot(3,1,2);

plot(t,shapedsignal_2);

title('shaped signal rolloff = 0.5');

xlabel('samples');

ylabel('amplitude');

rolloff = 1;

span = 20;

sps = 50;

rcosfilter_3 = rcosdesign(rolloff, span, sps,'sqrt');

shapedsignal_3 = conv(input,rcosfilter_3,'same');

subplot(3,1,3);

plot(t,shapedsignal_3);

title('shaped signal rolloff = 1');

xlabel('samples');

ylabel('amplitude');

%%ask modulation

modulationsignal_1 = carrier .* shapedsignal_1;

figure(3);

subplot(3,1,1);

plot(t,modulationsignal_1);

title('modulation signal rolloff = 0');

xlabel('samples');

ylabel('amplitude');

grid on;

modulationsignal_2 = carrier .* shapedsignal_2;

subplot(3,1,2);

plot(t,modulationsignal_2);

title('modulation signal rolloff = 0.5');

xlabel('samples');

ylabel('amplitude');

grid on;

modulationsignal_3 = carrier .* shapedsignal_3;

subplot(3,1,3);

plot(t,modulationsignal_3);

title('modulation signal rolloff = 1');

xlabel('samples');

ylabel('amplitude');

grid on;

lpf = fdesign.lowpass('fp,fst,ap,ast',1,20,1,60,100);

lowpass = design(lpf,'equiripple');

%[ a b c d] = butter(10,[1 5]/50);

[b a] = butter(5,0.95,'low');

%d=designfilt('bandpassfir','filterorder',50, ...

%'cutofffrequency1',1,'cutofffrequency2',5, ...

%'samplerate',100);

%�d noise

h = 1;j = 1;

for snr = 1:1:15

snrlin = 10.^(snr./10);

rxsig_1=awgn(modulationsignal_3,snr,'measured',1);

%�modulation

x = rxsig_1.* carrier;

%e = filter(d,x);

y = filter(lowpass,x);

%e = envelope(y);

z = conv(y,rcosfilter_3,'same');

%e = envelope(z);

figure(4);

subplot(4,4,snr);

plot(t,rxsig_1,'g','linewidth',2);

hold on;

plot(t,modulationsignal_3,'b');

title(['snr:',num2str(snr),'db']);

xlabel('samples');

ylabel('amplitude');

%%comparator

l = length(y);

for i = 1:1:l

if z(i)> 2

output(i) = 1;

else

output(i) = 0;

end

end

figure(5);

xlabel('samples');

ylabel('amplitude');

subplot(5,3,snr);

plot(t,output);

title(['snr:',num2str(snr),'db'])

error = length(find(output ~= input));

cber(h) = error/32000;

h = h 1;

tber(j) = qfunc(sqrt(snrlin));

snrdb(j) = snr;

j = j 1;

end

figure(4);

legend('signal with noise','signal after filteration');

figure(5);

legend('received bits with different singal to noise radio');

figure('name','comparison b/w theoretical&calculated ber');

semilogy(snrdb,cber,'-bo',snrdb,tber,'-mh');

hold on;

grid on;

legend('ber calculated','ber theoretical')

xlabel('snr in db');

ylabel('bit error rate');

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