%%QPSK
clc;
clear all;
close all;
nsymbol = 50000;%%每种信噪比下符号数的发送符号数
data = randi([0,1],1,nsymbol*2); %%产生1行,nsymbol列均匀分布的随机数0,1 qpsk_mod1 = zeros(1,nsymbol);
qpsk_mod2 = zeros(1,nsymbol);
data_receive1 = zeros(1,nsymbol);
data_receive2 = zeros(1,nsymbol);
data_receive = zeros(1,nsymbol*2);
Wrongnumber = 0;
SymbolWrongnumber = 0;
for i=1:nsymbol %%调制
symbol1 = data(2*i-1);
symbol2 = data(2*i);
if symbol1 == 0 & symbol2 == 0
qpsk_mod1(i) = 1;
qpsk_mod2(i) = 0;
elseif symbol1 == 0 & symbol2 == 1
qpsk_mod1(i) = 0;
qpsk_mod2(i) = 1;
elseif symbol1 == 1 & symbol2 == 1
qpsk_mod1(i) = -1;
qpsk_mod2(i) = 0;
elseif symbol1 == 1 & symbol2 == 0
qpsk_mod1(i) = 0;
qpsk_mod2(i) = -1;
end
end
SNR_dB = 1:10;%%%信噪比dB形式
SNR = 10.^(SNR_dB/10);%%信噪比转化为线性值
for loop= 1:10
sigma = sqrt(1/(2*SNR(loop)));%%%根据符号功率求噪声功率
qpsk_receive1 = qpsk_mod1 + sigma * randn(1,nsymbol);
qpsk_receive2 = qpsk_mod2 + sigma * randn(1,nsymbol); %%添加复高斯白噪声for k=1:nsymbol
if qpsk_receive2(k) > qpsk_receive1(k)
data_receive2(k) = 1;
end
if qpsk_receive2(k) < qpsk_receive1(k)
data_receive2(k) = 0;
end
if qpsk_receive2(k) > -qpsk_receive1(k)
data_receive1(k) = 0;
end
if qpsk_receive2(k) < -qpsk_receive1(k)
data_receive1(k) = 1;
end
data_receive(2*k-1) = data_receive1(k);
data_receive(2*k) = data_receive2(k);
end
for p=1:(nsymbol*2)
if data_receive(p) ~= data(p)
Wrongnumber = Wrongnumber + 1;
end
end
for l=1:nsymbol
if data_receive1(l)~=data(2*l-1);
SymbolWrongnumber = SymbolWrongnumber + 1;
elseif data_receive2(l) ~= data(2*l);
SymbolWrongnumber = SymbolWrongnumber + 1;
end
end
Pe(loop)=SymbolWrongnumber/nsymbol;
Pb(loop)=Wrongnumber/(nsymbol*2);
Wrongnumber = 0 ;
SymbolWrongnumber = 0;
end
Pe_theory = 1-(1-qfunc(sqrt(SNR))).^2;
Pb_theory = 0.5* erfc(sqrt(SNR/2));
semilogy(SNR_dB,Pb,'-k*',SNR_dB,Pb_theory,'-bo',SNR_dB,Pe,'-r',SNR_dB,Pe_theory,'g') title('QPSK信号在AWGN信道下的性能');
xlabel('信噪比/dB');ylabel('误码率');
legend('误比特率','理论误比特率','误码率','理论误码率');
grid on;