ser_compare.m

ofdm信道估计仿真（ls算法

clc;
clear all;
%生成训练序列
%用BPSK调制
X=zeros(64,64);
d=rand(64,1);
      for i=1:64
       if(d(i)>=0.5)
           d(i)=+1;
       else
           d(i)=-1;
       end
    end
 for i=1:64
     X(i,i)=d(i);
 end
%计算出信道向量G
 %信道特性
  tau=[0.5 3.5];
for k=1:64
      s=0;
      for m=1:2
         s=s+(exp(-j*pi*(1/64)*(k+63*tau(m))) * (( sin(pi*tau(m)) / sin(pi*(1/64)*(tau(m)-k)))));
      end
g(k)=s/sqrt(64);
end
G=g';%信道向量
H=fft(G);% 频域
XFG=X*H;
n1=ones(64,1);
n1=n1*0.000000000000000001i;%加入复高斯白噪声
noise=awgn(n1,8);%设置SNR为8db
variance=var(noise);
N=fft(noise);
Y=XFG+N;

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%求出G的自相关矩阵Rgg
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gg=zeros(64,64);
for i=1:64
    gg(i,i)=G(i);
end
gg_myu = sum(gg, 1)/64;                    
gg_mid = gg - gg_myu(ones(64,1),:);        
sum_gg_mid= sum(gg_mid, 1);
Rgg = (gg_mid' * gg_mid- (sum_gg_mid'  * sum_gg_mid) / 64) / (64 - 1);

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%下面求MMSE算法和LS算法的SER
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%求H_ls
%H_ls=inv(X)*Y;
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
H_ls=(inv(X)) * Y;
Hls=zeros(64,64);
for i=1:64
    Hls(i,i)=H_ls(i);
end

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%求Hmmse
%H_mmse=F*Rgg*inv(Rgy)*Y;
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
u=rand(64,64);
F=fft(u)*inv(u);
I=eye(64,64);
Rgy=Rgg * F'* X';
Ryy=X * F * Rgg * F' *X' + variance * I;
for i=1:64
    yy(i,i)=Y(i);
end
Gmmse=Rgy * inv(Ryy)* Y;
H_mmse=fft(Gmmse);
for i=1:64
  Hmmse(i,i)=H_mmse(i); 
end
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for n=1:6

SNR_send=3*n;
error_count_ls=0;%清空error_count..
error_count_mmse=0;%清空error_count..

for c=1:1000
%生成随机序列
X=zeros(64,64);
d=rand(64,1);
      for i=1:64
       if(d(i)>=0.5)
           d(i)=+1;
       else
           d(i)=-1;
       end
    end
 for i=1:64
     X(i,i)=d(i);
 end
XFG=X*H;
n1=ones(64,1);
n1=n1*0.000000000000000001i;%加入复高斯白噪声
noise=awgn(n1,SNR_send);
variance=var(noise);
N=fft(noise);
Y=XFG+N;
%接收机
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% I:LS估计器的接收：
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    I=inv(Hls)* Y;
     for k=1:64
       
        if(real(I(k))>0)%判决
            I(k)=1;
         else
            I(k)=-1;
         end
     end 
   for k=1:64
        if(I(k)~=d(k))
            error_count_ls=error_count_ls+1;
        end
    end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% I:MMSE估计器的接收：
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    I=inv(Hmmse)* Y;
     for k=1:64
       
        if(real(I(k))>0)%判决
            I(k)=1;
         else
            I(k)=-1;
         end
     end 
   for k=1:64
        if(I(k)~=d(k))
            error_count_mmse=error_count_mmse+1;
        end
    end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
end

ser_ls(n)=error_count_ls/64000;
ser_mmse(n)=error_count_mmse/64000;
ser_ls
ser_mmse
SNR(n)=SNR_send;

end;

%作图
semilogy(SNR,ser_mmse,'-vk');
axis([2,18,0.01,1]);
grid on;
xlabel('SNR in DB');
ylabel('Symbol Error Rate');
title('OFDM系统MMSE和LS算法的比较（SER）');

hold on;
semilogy(SNR,ser_ls,'-*b');
axis([2,18,0.01,1]);
grid on;
xlabel('SNR in DB');
ylabel('Symbol Error Rate');
title('OFDM系统MMSE和LS算法的比较（SER）');
legend('MMSE算法','LS算法');
hold off