void TurboCode::Decoder_term(const itpp::cvec &in1,
const itpp::cvec &in2,
double n0, int iteration) const
{
int memory = rsc1_.Constraint() - 1;
static itpp::vec llrZeros(0);
if (llrZeros.size() != memory){
llrZeros.set_size(memory);
llrZeros.zeros();
} // if
for (int ite = 0; ite < iteration; ++ite){
itpp::vec llrFromRsc1;
rsc1_.Decode(in1, llrToRsc1_, &llrFromRsc1, n0);
itpp::vec llrToRsc2 = Interleave(llrFromRsc1.left(interleaver_.size()), interleaver_);
llrToRsc2 = itpp::concat(llrToRsc2, llrZeros);
itpp::vec llrFromRsc2;
rsc2_.Decode(in2, llrToRsc2, &llrFromRsc2, n0);
llrToRsc1_ = Deinterleave(llrFromRsc2.left(interleaver_.size()), interleaver_);
llrToRsc1_ = itpp::concat(llrToRsc1_, llrZeros);
} // for ite
}
void TurboCodeWithZP::Decoder_term(const itpp::cvec& in1,
const itpp::cvec& in2,
double n0, int iterations) const
{
// std::cout << "## zeroPadding_ = " << zeroPadding_.PadPositions() << std::endl;
int memory = rsc1_.Constraint() - 1;
static itpp::vec llrZeros(0);
if (llrZeros.size() != memory){
llrZeros.set_size(memory);
llrZeros.zeros();
} // if
for (int ite = 0; ite < iterations; ++ite){
itpp::vec llrToRsc1_mod = zeroPadding_.ModifyLLR(llrToRsc1_);
itpp::vec llrFromRsc1;
rsc1_.Decode(in1, llrToRsc1_mod, &llrFromRsc1, n0);
itpp::vec llrFromRsc1_mod = zeroPadding_.ModifyLLR(llrFromRsc1);
itpp::vec llrToRsc2 = Interleave(llrFromRsc1_mod.left(interleaver_.size()), interleaver_);
llrToRsc2 = itpp::concat(llrToRsc2, llrZeros);
itpp::vec llrFromRsc2;
rsc2_.Decode(in2, llrToRsc2, &llrFromRsc2, n0);
llrToRsc1_ = Deinterleave(llrFromRsc2.left(interleaver_.size()), interleaver_);
llrToRsc1_ = itpp::concat(llrToRsc1_, llrZeros);
} // for ite
}
itpp::bvec Rsc::HardDecision(const itpp::vec &lambda)
{
int length = lambda.size();
itpp::bvec outputBits(length);
for (int i = 0; i < length; ++i){
if (lambda[i] > 0){
outputBits[i] = 1;
} // if
else{
outputBits[i] = 0;
} // else
} // for i
return outputBits;
}
void SISO::equalizer_maxlogMAP(itpp::vec &extrinsic_data, const itpp::vec &rec_sig, const itpp::vec &apriori_data)
/*
extrinsic_data - extrinsic information for channel input symbols
rec_sig - received symbols
apriori_data - a priori information for channel input symbols
*/
{
//get parameters
int N = rec_sig.length();//length of the received frame
//other parameters
register int n,k,m;
int pstates[2];
int nstates[2];
int inputs[2];
double C[2];//log(gamma)
double sum;
double sumbis;
double buffer;
//initialize trellis
gen_chtrellis();
//initialize log(alpha) and log(beta)
double* A = new double[chtrellis.stateNb*(N+1)];
double* B = new double[chtrellis.stateNb*(N+1)];
A[0] = 0;
for (n=1; n<chtrellis.stateNb; n++)
A[n] = -INFINITY;
B[N*chtrellis.stateNb] = 0;
sum = (tail?-INFINITY:0);
for (n=1; n<chtrellis.stateNb; n++)
B[n+N*chtrellis.stateNb] = sum;//if tail==false the final state is not known
#pragma omp parallel sections private(n,sum,m,k,C)
{
//forward recursion
for (n=1; n<=N; n++)
{
sum = -INFINITY;//normalization factor
for (m=0; m<chtrellis.stateNb; m++) //final state
{
for (k=0; k<2; k++)
{
pstates[k] = chtrellis.prevState[m+chtrellis.stateNb*k];//determine previous states
inputs[k] = chtrellis.input[m+chtrellis.stateNb*k];//determine input
C[k] = (inputs[k])*apriori_data[n-1]-itpp::sqr(rec_sig[n-1]-chtrellis.output[pstates[k]+chtrellis.stateNb*inputs[k]])/(2*sigma2);//compute log of gamma
}
A[m+n*chtrellis.stateNb] = std::max(A[pstates[0]+(n-1)*chtrellis.stateNb]+C[0], A[pstates[1]+(n-1)*chtrellis.stateNb]+C[1]);
sum = std::max(sum, A[m+n*chtrellis.stateNb]);
}
for (m=0; m<chtrellis.stateNb; m++)
A[m+n*chtrellis.stateNb] -= sum;
}
//backward recursion
#pragma omp section
for (n=N-1; n>=0; n--)
{
sum = -INFINITY;//normalisation factor
for (m=0; m<chtrellis.stateNb; m++) //initial state
{
for (k=0; k<2; k++)
{
nstates[k] = chtrellis.nextState[m+k*chtrellis.stateNb];//determine next states
C[k] = (k)*apriori_data[n]-itpp::sqr(rec_sig[n]-chtrellis.output[m+k*chtrellis.stateNb])/(2*sigma2);//compute log of gamma
}
B[m+n*chtrellis.stateNb] = std::max(B[nstates[0]+(n+1)*chtrellis.stateNb]+C[0], B[nstates[1]+(n+1)*chtrellis.stateNb]+C[1]);
sum = std::max(sum, B[m+n*chtrellis.stateNb]);
}
for (m=0; m<chtrellis.stateNb; m++)
B[m+n*chtrellis.stateNb] -= sum;
}
}
//compute extrinsic_data
extrinsic_data.set_size(N);
for (n=1; n<=N; n++)
{
sum = -INFINITY;
sumbis = -INFINITY;
for (m=0; m<chtrellis.stateNb; m++) //initial state
{
for (k=0; k<2; k++) //input index
{
nstates[k] = chtrellis.nextState[m+k*chtrellis.stateNb];//determine next states
C[k] = (k)*apriori_data[n-1]-itpp::sqr(rec_sig[n-1]-chtrellis.output[m+k*chtrellis.stateNb])/(2*sigma2);//compute log of gamma
buffer = A[m+(n-1)*chtrellis.stateNb]+C[k]+B[nstates[k]+n*chtrellis.stateNb];
if (k)
sum = std::max(sum, buffer);//1
else
sumbis = std::max(sumbis, buffer);//0
}
}
extrinsic_data[n-1] = (sum-sumbis)-apriori_data[n-1];
}
//free memory
delete[] chtrellis.output;
delete[] chtrellis.nextState;
delete[] chtrellis.prevState;
delete[] chtrellis.input;
delete[] A;
delete[] B;
}
