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Hello,
I know how to calculate gama values, you should do this las follows, but I have a question for you, I did the same thing as you but my MMSE detector doesn't work, that is my code,
function [LLR1,LLR0]=SISO_MMSE_MIMO(H,y,Es,N0,Omega,List,La0,La1,nt,nr,m);
%Es: is the symbol energy of the constellation
%z=constellation points in bits format
%sz: constellation points in complex format
% m * n_t of a priori p(b=1) (La1) and p(b=0)(La0)
%Omega= constelatiopn set
% List : binary form of constellation list
for i=1: nt
La1i(i,:)=La1((i-1)*m+1:i*m);
La0i(i,:)=La0((i-1)*m+1:i*m);
for k=1:2^m
p(i,k)=prod(La1i(find(List(k,:)==1)))* prod(La0i(find(List(k,:)==0)));
end
mean(i)=sum( p(i,:)*Omega);
sigma(i)= sum(p(i,:)* (abs(Omega).^2))- abs(mean(i))^2;
end
for i=1:nt
Gamai=diag([sigma(1:i-1),Es, sigma(i+1:nt)]);
ztilt(i)=Es.*(y-[mean(1:i-1), 0, mean(i+1:nt)]*H)* inv((H')* Gamai*H+N0.*eye(nr))*H(i,:)';
mu(i)=(Es)* H(i,:) * inv((H')* Gamai*H+N0.*eye(nr))* H(i,:)';
for k=1:2^m
pztilti(i,k)=exp(-abs(ztilt(i)- mu(i)* Omega(k)).^2/(mu(i)*(1-mu(i))*Es))/(mu(i)*(1-mu(i))*Es*pi);
end
end
LLR1=[];
LLR0=[];
for i=1:nt
sk=[];
sk0=[];
for k=1:m
sk=find(List(:,k)==1);
sk0=find(List(:,k)==0);
xi1(i,k)=pztilti(i,sk)*p(i,sk).';
xi0(i,k)=pztilti(i,sk0)*p(i,sk0).';
xi(i,k)=log(xi1(i,k)/xi0(i,k))-log(La1i(i,k)/La0i(i,k)) ;
end
LLR1=[LLR1 exp(xi(i,:))./(1+exp(xi(i,:)))];
LLR0=[LLR0 1./(1+exp(xi(i,:)))];
end
I did it using Nicolas Gresset phd thesis. Can you help me?
and yours :
function [Lambda2_1,Lambda2_0,Ld_out_1,Ld_out_0,test]=siso_dec(lambda1_1,lambda1_0,G,k,tran,com_s,bra_o,flag);
% Copyright 2003 for academic use only
% SISO module for decoding of general convolutional codes
% tran, com_s, bra_o: description of trellis;
[n,Kk]=size(G);
K=Kk/k;
M=(K-1)*k;mx=2^M;
[n,l]=size(lambda1_1);
c=ones(1,l);
if flag==0;
Ld_out=zeros(k,l);
end
%alpha_0(mx,:)=10^(-9);
alpha_0(mx,:)=0;
alpha_0(1,1)=1;
% Calculate alpha(:,1)
for s2=1:mx
alpha(s2,1)=0;
for p=1:2^k
b=bra_o(com_s(s2,p)+(s2-1)*mx,:)';
B=1;
for i=1:length(b)
if b(i)==1 B=B.*lambda1_1(i,1);
else
B=B.*lambda1_0(i,1);
end;
end;
%if B==0 B=1e-40;end;
%alpha(s2,1)=alpha(s2,1)+alpha_0(com_s(s2,p),1)*prod(0.5*(1+b.*tanh(0.5*lambda1(:,1))));
alpha(s2,1)=alpha(s2,1)+alpha_0(com_s(s2,p),1)*B;
end
end
%for i=1:mx if (alpha(i,1)< 1e-15) alpha(i,1)=1e-15;end;end;
c(1)=sum(alpha(:,1))^(-1);%if c(1)<1e-10 c(1)=1e-10;end;
%al1=alpha;
%al0=alpha_0;
alpha_T(:,1)=c(1)*alpha(:,1);
% Start forward recursion to calculate alpha(mx,2:l-1): Note the last index is (l-1)
for ik=2:l-1,
for s2=1:mx,
alpha_H(s2,ik)=0;
for p=1:2^k,
b=bra_o(com_s(s2,p)+(s2-1)*mx,:)';
B=1;
for i=1:length(b)
if b(i)==1 B=B.*lambda1_1(i,ik);
else
B=B.*lambda1_0(i,ik);
end;
end;
%if B==0 B=1e-40;end;
alpha_H(s2,ik)=alpha_H(s2,ik)+alpha_T(com_s(s2,p),ik-1)*B;
end
end
c(ik)=sum(alpha_H(:,ik))^(-1);if c(ik)<1e-10 c(ik)=1e-10;end;
%if (c(ik)>1e+60) c(ik)=1e+60;end;
alpha_T(:,ik)=c(ik)*alpha_H(:,ik);
end
%al=alpha_T;
%beta(mx,l)=10^(-9);
beta(mx,l)=0;
beta(1,l)=1;
%beta_T(mx,l)=10^(-9);
beta_T(mx,l)=0;
beta_T(1,l)=1;
% Calculate beta(:,l-1)
for s1=1:mx
beta(s1,l-1)=0;
for p=1:2^k
b=bra_o(s1+(tran(s1,p)-1)*mx,:)';
B=1;
for i=1:length(b)
if b(i)==1 B=B.*lambda1_1(i,l);
else
B=B.*lambda1_0(i,l);
end;
end;
%if B==0 B=1e-40;end;
beta(s1,l-1)=beta(s1,l-1)+beta(tran(s1,p),l)*B;
end
end
beta_T(:,l-1)=c(l-1)*beta(:,l-1);
% Start backward recursion to calculate beta(mx,1:l-2)
for ik=l-2:-1:1,
for s1=1:mx,
beta_H(s1,ik)=0;
for p=1:2^k
b=bra_o(s1+(tran(s1,p)-1)*mx,:)';
B=1;
for i=1:length(b)
if b(i)==1 B=B.*lambda1_1(i,ik+1);
else
B=B.*lambda1_0(i,ik+1);
end;
end;
%if B==0 B=1e-40;end;
beta_H(s1,ik)=beta_H(s1,ik)+beta_T(tran(s1,p),ik+1)*B;
end
end
beta_T(:,ik)=c(ik)*beta_H(:,ik);
end
%be=beta_T;
% Now we are ready to give the outputs
for ik=1:l, %actual index is 1:l
top=zeros(n,1);bot=zeros(n,1);
top_d=zeros(k,1);bot_d=zeros(k,1);
for s1=1:mx, % scanning over all sigma_k states
for edge=1:2^k, % scanning over all branches comming out from sigma_k state
d=bin_stat(edge-1,k);
b=bra_o(s1+(tran(s1,edge)-1)*mx,:)';
if (ik==1)
for t=1:n
pro_index=find([1:n]~=t);
pro=1;
for r=1:n-1
q=pro_index(r);
if b(q)==1
pro=pro.*lambda1_1(q,ik);
else
pro=pro.*lambda1_0(q,ik);
end;
end
if (b(t)==1)
top(t)=top(t)+alpha_0(s1,ik)*beta_T(tran(s1,edge),ik)*pro;
else
bot(t)=bot(t)+alpha_0(s1,ik)*beta_T(tran(s1,edge),ik)*pro;
end
end
else
for t=1:n
pro_index=find([1:n]~=t);
pro=1;
for r=1:n-1
q=pro_index(r);
if (b(q)==1)
pro=pro.*lambda1_1(q,ik);
else
pro=pro.*lambda1_0(q,ik);
end;
end
if (b(t)==1)
top(t)=top(t)+alpha_T(s1,ik-1)*beta_T(tran(s1,edge),ik)*pro;
else
bot(t)=bot(t)+alpha_T(s1,ik-1)*beta_T(tran(s1,edge),ik)*pro;
end
end
end
if flag==1
if (ik==1)
for jj=1:k
if (d(jj)==1)
B=1;
for i=1:length(b)
if b(i)==1 B=B.*lambda1_1(i,ik);
else
B=B.*lambda1_0(i,ik);
end;
end;
top_d(jj)=top_d(jj)+alpha_0(s1,ik)*beta_T(tran(s1,edge),ik)*B;
else
B=1;
for i=1:length(b)
if b(i)==1 B=B.*lambda1_1(i,ik);
else
B=B.*lambda1_0(i,ik);
end;
end;
bot_d(jj)=bot_d(jj)+alpha_0(s1,ik)*beta_T(tran(s1,edge),ik)*B;
end
end
else
for jj=1:k
if (d(jj)==1)
B=1;
for i=1:length(b)
if b(i)==1 B=B.*lambda1_1(i,ik);
else
B=B.*lambda1_0(i,ik);
end;
end;
top_d(jj)=top_d(jj)+alpha_T(s1,ik-1)*beta_T(tran(s1,edge),ik)*B;
else
B=1;
for i=1:length(b)
if b(i)==1 B=B.*lambda1_1(i,ik);
else
B=B.*lambda1_0(i,ik);
end;
end;
bot_d(jj)=bot_d(jj)+alpha_T(s1,ik-1)*beta_T(tran(s1,edge),ik)*B;
end
end
end
end
end
end
% bot(find(bot==0))=10^(-10);top(find(top==0))=10^(-10);
% bot_d(find(bot_d==0))=10^(-10);top_d(find(top_d==0))=10^(-10);
bot(find(bot<10^(-10)))=10^(-10);top(find(top<10^(-10)))=10^(-10);
bot_d(find(bot_d<10^(-10)))=10^(-10);top_d(find(top_d<10^(-10)))=10^(-10);
lambda2_1(:,ik)=top;
lambda2_0(:,ik)=bot;
Ld_out_1(:,ik)=top_d;
Ld_out_0(:,ik)=bot_d;
end
%Lambda2_1=lambda2_1+lambda1_1;
%Lambda2_0=lambda2_0+lambda1_0;
Lambda2_1=lambda2_1;
Lambda2_0=lambda2_0;
test=Ld_out_1+Ld_out_0;
%Lambda2=lambda2;
but I "birhane Alemayoh" <birhanea@gmail.com> wrote in message <hi21go$26a$1@fred.mathworks.com>...
> Dear all
> I am implementing a soft input soft output (SISO) MMSE detector and SISO decoder in an iterative fashion (turbo receiver). A de-interleaver and interleaver is used in between the detector and decoder. I am using a convolution encoder at the transmitter side. Therefore, my decoder is the Log MAP decoder.
> I have computed the extrinsic information of the output of the SISO MMSE detector and those will be delivered to the Log MAP decoder.
> My question is, how do I calculate the gama parameter for the decoder having the a priori information from the detector.
> I know that, in normal Log MAP decoder implemented with just BPSK, the main input to the decoder is the received signal. and the gama parameter (branch metric) may be calculated by computing the correlation of the received signal and all possible coded bits with in the corresponding time intervals.
> please help me.
> I am waiting your valuable response.
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