cm_sm32.m

高斯噪声下的8psk误码率检测与理论值比较

function[pb,ps]=cm_sm32(snr_in_dB)
%[pb,ps]=cm_sm32(snr_in_dB)
%        CM_SM32求出QPSK以dB为单位的给定信噪比的
%        比特误码率和符号误码率
N=10000;
E=1;                      %每符号能量
snr=10^(snr_in_dB/10);    %信噪比
sgma=sqrt(E/(3*2*snr));       %噪声标准方差
%信号映射
s000=[1,0];
s001=[cos(pi/4),sin(pi/4)];
s011=[0,1];
s010=[cos(3*pi/4),sin(3*pi/4)];
s110=[-1,0];
s111=[cos(5*pi/4),sin(5*pi/4)];
s101=[0,-1];
s100=[cos(7*pi/4),sin(7*pi/4)];
%数据源的产生
for i=1:N,
	temp=rand;         %在区间（0，1 )间的一个均匀随机变量
	if  (temp<0.125),        %信源输出为“000”的概率为1/8
	    dsource1(i)=0;    
	    dsource2(i)=0;
        dsource3(i)=0;
	elseif (temp<0.25),      %信源输出为“001”的概率为1/8
	    dsource1(i)=0;
	    dsource2(i)=0;
        dsource3(i)=1;
	elseif (temp<0.375),     %信源输出为“010”的概率为1/8
	    dsource1(i)=0;
	    dsource2(i)=1;
        dsource3(i)=0;
	elseif (temp<0.5),       %信源输出为“011”的概率为1/8
    	dsource1(i)=0; 
	    dsource2(i)=1;
        dsource3(i)=1;
    elseif (temp<0.625),     %信源输出为“100”的概率为1/8
    	dsource1(i)=1; 
	    dsource2(i)=0;
        dsource3(i)=0;
   elseif (temp<0.75),       %信源输出为“101”的概率为1/8
    	dsource1(i)=1; 
	    dsource2(i)=0;
        dsource3(i)=1;
   elseif (temp<0.875),      %信源输出为“110”的概率为1/8
    	dsource1(i)=1; 
	    dsource2(i)=1;
        dsource3(i)=0;
   else                      %信源输出为“111”的概率为1/8
    	dsource1(i)=1; 
	    dsource2(i)=1;
        dsource3(i)=1;
	end;
end;
%判决、误码率的计算
numofsymbolerror=0;
numofbiterror=0;
for i=1:N,
    %在判决器处的接收信号，对于第i个符号为：
	n(1)=gngauss(sgma);
	n(2)=gngauss(sgma);
    if     ((dsource1(i)==0) & (dsource2(i)==0)& (dsource3(i)==0)),
		r=s000+n;
	elseif ((dsource1(i)==0) & (dsource2(i)==0)& (dsource3(i)==1)),
		r=s001+n;
	elseif ((dsource1(i)==0) & (dsource2(i)==1)& (dsource3(i)==0)),
		r=s010+n;
	elseif ((dsource1(i)==0) & (dsource2(i)==1)& (dsource3(i)==1)), 
		r=s011+n;
    elseif ((dsource1(i)==1) & (dsource2(i)==0)& (dsource3(i)==0)), 
		r=s100+n;
    elseif ((dsource1(i)==1) & (dsource2(i)==0)& (dsource3(i)==1)), 
		r=s101+n;
    elseif ((dsource1(i)==1) & (dsource2(i)==1)& (dsource3(i)==0)), 
		r=s110+n;
    else
		r=s111+n;   
	end;
    %以下为计算互相关量度
	c000=dot(r , s000);
	c001=dot(r , s001);	
	c010=dot(r , s010);
	c011=dot(r , s011);
    c100=dot(r , s100);
	c101=dot(r , s101);	
	c110=dot(r , s110);
	c111=dot(r , s111);
    %第i个符号的判决按如下方式进行
	c_max=max([c000 c001 c010 c011 c100 c101 c110 c111]);
	if (c000==c_max)
		decis1=0;decis2=0;decis3=0;
	elseif (c001==c_max)
		decis1=0;decis2=0;decis3=1;
	elseif (c010==c_max)
		decis1=0;decis2=1;decis3=0;
	elseif (c011==c_max)
		decis1=0;decis2=1;decis3=1;
    elseif (c100==c_max)
		decis1=1;decis2=0;decis3=0;
	elseif (c101==c_max)
		decis1=1;decis2=0;decis3=1;
	elseif (c110==c_max)
		decis1=1;decis2=1;decis3=0;
	else
		decis1=1;decis2=1;decis3=1;    
	end;
	%如果判决不对，计错器加1
	symbolerror=0;
	if (decis1~=dsource1(i)),
		numofbiterror=numofbiterror+1;
		symbolerror=1;
	end;
	if (decis2~=dsource2(i)),
		numofbiterror=numofbiterror+1;
		symbolerror=1;
	end;
    if (decis3~=dsource3(i)),
	    numofbiterror=numofbiterror+1;
		symbolerror=1;
	end;
	if (symbolerror==1),
		numofsymbolerror=numofsymbolerror+1;
	end;
end;
ps=numofsymbolerror/N;     %因为总共有N个符号
pb=numofbiterror/(3*N);    %因为发送了3N个比特