仿真高斯白噪声信道下QPSK的EbN0与误比特率之间的关系Word文档下载推荐.docx
《仿真高斯白噪声信道下QPSK的EbN0与误比特率之间的关系Word文档下载推荐.docx》由会员分享,可在线阅读,更多相关《仿真高斯白噪声信道下QPSK的EbN0与误比特率之间的关系Word文档下载推荐.docx(12页珍藏版)》请在冰豆网上搜索。
=7);
x1(i)=1;
elsex1(i)=-1;
end
end
t1=[0:
8-0.01];
t2=0:
7-0.01;
t3=-1:
7.1-0.01;
t4=0:
8.1-0.01;
tt1=length(t1);
x2=ones(1,800);
tt1
if(t1(i)>
=0&
t1(i)<
=2)|(t1(i)>
=4&
=8);
x2(i)=1;
elsex2(i)=-1;
f=0:
0.1:
1;
xrc=0.5+0.5*cos(pi*f);
y1=conv(x1,xrc)/5.5;
y2=conv(x2,xrc)/5.5;
n0=randn(size(t2));
f1=1;
i=x1.*cos(2*pi*f1*t);
q=x2.*sin(2*pi*f1*t1);
I=i(101:
800);
Q=q(1:
700);
QPSK=sqrt(1/2).*I+sqrt(1/2).*Q;
QPSK_n=(sqrt(1/2).*I+sqrt(1/2).*Q)+n0;
n1=randn(size(t2));
i_rc=y1.*cos(2*pi*f1*t3);
q_rc=y2.*sin(2*pi*f1*t4);
I_rc=i_rc(101:
Q_rc=q_rc(1:
QPSK_rc=(sqrt(1/2).*I_rc+sqrt(1/2).*Q_rc);
QPSK_rc_n1=QPSK_rc+n1;
figure
(1)
subplot(4,1,1);
plot(t3,i_rc);
axis([-18-11]);
ylabel('
a序列'
);
subplot(4,1,2);
plot(t4,q_rc);
b序列'
subplot(4,1,3);
plot(t2,QPSK_rc);
合成序列'
subplot(4,1,4);
plot(t2,QPSK_rc_n1);
加入噪声'
效果图:
%设定T=1,加入高斯噪声
%调制
bit_in=randint(1e3,1,[01]);
bit_I=bit_in(1:
2:
1e3);
bit_Q=bit_in(2:
data_I=-2*bit_I+1;
data_Q=-2*bit_Q+1;
data_I1=repmat(data_I'
20,1);
data_Q1=repmat(data_Q'
1e4
data_I2(i)=data_I1(i);
data_Q2(i)=data_Q1(i);
end;
data_I2_rc=conv(data_I2,xrc)/5.5;
data_Q2_rc=conv(data_Q2,xrc)/5.5;
t1=0:
1e3+0.9;
n0=rand(size(t1));
I_rc=data_I2_rc.*cos(2*pi*f1*t1);
Q_rc=data_Q2_rc.*sin(2*pi*f1*t1);
QPSK_rc_n0=QPSK_rc+n0;
%解调
I_demo=QPSK_rc_n0.*cos(2*pi*f1*t1);
Q_demo=QPSK_rc_n0.*sin(2*pi*f1*t1);
%低通滤波
I_recover=conv(I_demo,xrc);
Q_recover=conv(Q_demo,xrc);
I=I_recover(11:
10010);
Q=Q_recover(11:
0.05:
1e3-0.05;
t3=0:
1e3-0.1;
%抽样判决
data_recover=[];
20:
10000
data_recover=[data_recoverI(i:
1:
i+19)Q(i:
i+19)];
bit_recover=[];
20000
ifsum(data_recover(i:
i+19))>
data_recover_a(i:
i+19)=1;
bit_recover=[bit_recover1];
else
i+19)=-1;
bit_recover=[bit_recover-1];
error=0;
dd=-2*bit_in+1;
ddd=[dd'
];
ddd1=repmat(ddd,20,1);
2e4
ddd2(i)=ddd1(i);
1e3
ifbit_recover(i)~=ddd(i)
error=error+1;
p=error/1000;
subplot(2,1,1);
plot(t2,ddd2);
axis([0100-22]);
title('
原序列'
subplot(2,1,2);
plot(t2,data_recover_a);
解调后序列'
%设定T=1,不加噪声
t=0:
I_demo=QPSK_rc.*cos(2*pi*f1*t1);
Q_demo=QPSK_rc.*sin(2*pi*f1*t1);
ddd=-2*bit_in+1;
ddd1=repmat(ddd'
10,1);
plot(t3,I);
axis([020-66]);
plot(t3,Q);
plot(t2,data_recover);
plot(t,ddd2);
%QPSK误码率分析
SNRindB1=0:
10;
SNRindB2=0:
length(SNRindB1)
[pb,ps]=cm_sm32(SNRindB1(i));
smld_bit_err_prb(i)=pb;
smld_symbol_err_prb(i)=ps;
length(SNRindB2)
SNR=exp(SNRindB2(i)*log(10)/10);
theo_err_prb(i)=Qfunct(sqrt(2*SNR));
QPSK误码率分析'
semilogy(SNRindB1,smld_bit_err_prb,'
*'
axis([01010e-81]);
holdon;
%semilogy(SNRindB1,smld_symbol_err_prb,'
o'
semilogy(SNRindB2,theo_err_prb);
legend('
仿真比特误码率'
'
理论比特误码率'
holdoff;
function[y]=Qfunct(x)
y=(1/2)*erfc(x/sqrt
(2));
function[pb,ps]=cm_sm32(SNRindB)
N=10000;
E=1;
SNR=10^(SNRindB/10);
sgma=sqrt(E/SNR)/2;
s00=[10];
s01=[01];
s11=[-10];
s10=[0-1];
N
temp=rand;
if(temp<
0.25)
dsource1(i)=0;
dsource2(i)=0;
elseif(temp<
0.5)
dsource2(i)=1;
0.75)
dsource1(i)=1;
else
end;
numofsymbolerror=0;
numofbiterror=0;
n=sgma*randn(size(s00));
if((dsource1(i)==0)&
(dsource2(i)==0))
r=s00+n;
elseif((dsource1(i)==0)&
(dsource2(i)==1))
r=s01+n;
elseif((dsource1(i)==1)&
r=s10+n;
r=s11+n;
c00=dot(r,s00);
c01=dot(r,s01);
c10=dot(r,s10);
c11=dot(r,s11);
c_max=max([c00c01c10c11]);
if(c00==c_max)
decis1=0;
decis2=0;
elseif(c01==c_max)
decis2=1;
elseif(c10==c_max)
decis1=1;
symbolerror=0;
if(decis1~=dsource1(i))
numofbiterror=numofbiterror+1;
symbolerror=1;
if(decis2~=dsource2(i))
if(symbolerror==1)
numofsymbolerror=numofsymbolerror+1;
ps=numofsymbolerror/N;
pb=numofbiterror/(2*N);