bvec encode(Convolutional_Code& nsc, int constraint_length, const bvec& encoder_input, int blockSize, bool verbose)
{
if (verbose) {cout << "input : " << encoder_input << endl;}
int codedLen = 2 * (blockSize + (constraint_length - 1));
int nBlocks = encoder_input.length() / blockSize;
ivec window(blockSize);
for (int j = 0; j < blockSize; j++) {
window[j] = j;
}
bvec nsc_coded_bits(codedLen);
bvec tr_coded_bits;
for (int j = 0; j < nBlocks; j++) {
nsc.encode_tail(encoder_input(window), nsc_coded_bits);
window = window + blockSize;
tr_coded_bits = concat(tr_coded_bits, nsc_coded_bits);
}
// Deal with residual sources if remainder exsists
if (nBlocks*blockSize != encoder_input.length()) {
bvec residual_bits = encoder_input.get(nBlocks*blockSize, encoder_input.length()-1);
nsc.encode_tail(residual_bits, nsc_coded_bits);
tr_coded_bits = concat(tr_coded_bits, nsc_coded_bits);
}
if (verbose) {cout << "encoder output: " << tr_coded_bits << endl;}
return tr_coded_bits;
}
int main(int argc, char **argv)
{
// -- modulation and channel parameters (taken from command line input) --
int nC; // type of constellation (1=QPSK, 2=16-QAM, 3=64-QAM)
int nRx; // number of receive antennas
int nTx; // number of transmit antennas
int Tc; // coherence time (number of channel vectors with same H)
if (argc != 5) {
cout << "Usage: cm nTx nRx nC Tc" << endl << "Example: cm 2 2 1 100000 (2x2 QPSK MIMO on slow fading channel)" << endl;
exit(1);
}
else {
sscanf(argv[1], "%i", &nTx);
sscanf(argv[2], "%i", &nRx);
sscanf(argv[3], "%i", &nC);
sscanf(argv[4], "%i", &Tc);
}
cout << "Initializing.. " << nTx << " TX antennas, " << nRx << " RX antennas, "
<< (1 << nC) << "-PAM per dimension, coherence time " << Tc << endl;
// -- simulation control parameters --
const vec EbN0db = "-5:0.5:50"; // SNR range
const int Nmethods = 2; // number of demodulators to try
const int Nbitsmax = 50000000; // maximum number of bits to ever simulate per SNR point
const int Nu = 1000; // length of data packet (before applying channel coding)
int Nbers, Nfers; // target number of bit/frame errors per SNR point
double BERmin, FERmin; // BER/FER at which to terminate simulation
if (Tc == 1) { // Fast fading channel, BER is of primary interest
BERmin = 0.001; // stop simulating a given method if BER<this value
FERmin = 1.0e-10; // stop simulating a given method if FER<this value
Nbers = 1000; // move to next SNR point after counting 1000 bit errors
Nfers = 200; // do not stop on this condition
}
else { // Slow fading channel, FER is of primary interest here
BERmin = 1.0e-15; // stop simulating a given method if BER<this value
FERmin = 0.01; // stop simulating a given method if FER<this value
Nbers = -1; // do not stop on this condition
Nfers = 200; // move to next SNR point after counting 200 frame errors
}
// -- Channel code parameters --
Convolutional_Code code;
ivec generator(3);
generator(0) = 0133; // use rate 1/3 code
generator(1) = 0165;
generator(2) = 0171;
double rate = 1.0 / 3.0;
code.set_generator_polynomials(generator, 7);
bvec dummy;
code.encode_tail(randb(Nu), dummy);
const int Nc = length(dummy); // find out how long the coded blocks are
// ============= Initialize ====================================
const int Nctx = (int)(2 * nC * nTx * ceil(double(Nc) / double(2 * nC * nTx))); // Total number of bits to transmit
const int Nvec = Nctx / (2 * nC * nTx); // Number of channel vectors to transmit
const int Nbitspvec = 2 * nC * nTx; // Number of bits per channel vector
// initialize MIMO channel with uniform QAM per complex dimension and Gray coding
ND_UQAM chan;
chan.set_M(nTx, 1 << (2*nC));
cout << chan << endl;
// initialize interleaver
Sequence_Interleaver<bin> sequence_interleaver_b(Nctx);
Sequence_Interleaver<int> sequence_interleaver_i(Nctx);
sequence_interleaver_b.randomize_interleaver_sequence();
sequence_interleaver_i.set_interleaver_sequence(sequence_interleaver_b.get_interleaver_sequence());
// RNG_randomize();
Array<cvec> Y(Nvec); // received data
Array<cmat> H(Nvec / Tc + 1); // channel matrix (new matrix for each coherence interval)
ivec Contflag = ones_i(Nmethods); // flag to determine whether to run a given demodulator
if (pow(2.0, nC*2.0*nTx) > 256) { // ML decoder too complex..
Contflag(1) = 0;
}
if (nTx > nRx) {
Contflag(0) = 0; // ZF not for underdetermined systems
}
cout << "Running methods: " << Contflag << endl;
cout.setf(ios::fixed, ios::floatfield);
cout.setf(ios::showpoint);
cout.precision(5);
// ================== Run simulation =======================
for (int nsnr = 0; nsnr < length(EbN0db); nsnr++) {
const double Eb = 1.0; // transmitted energy per information bit
const double N0 = inv_dB(-EbN0db(nsnr));
const double sigma2 = N0; // Variance of each scalar complex noise sample
const double Es = rate * 2 * nC * Eb; // Energy per complex scalar symbol
// (Each transmitted scalar complex symbol contains rate*2*nC
// information bits.)
const double Ess = sqrt(Es);
Array<BERC> berc(Nmethods); // counter for coded BER
Array<BERC> bercu(Nmethods); // counter for uncoded BER
Array<BLERC> ferc(Nmethods); // counter for coded FER
for (int i = 0; i < Nmethods; i++) {
ferc(i).set_blocksize(Nu);
}
long int nbits = 0;
while (nbits < Nbitsmax) {
nbits += Nu;
// generate and encode random data
bvec inputbits = randb(Nu);
bvec txbits;
code.encode_tail(inputbits, txbits);
// coded block length is not always a multiple of the number of
// bits per channel vector
txbits = concat(txbits, randb(Nctx - Nc));
txbits = sequence_interleaver_b.interleave(txbits);
// -- generate channel and data ----
for (int k = 0; k < Nvec; k++) {
/* A complex valued channel matrix is used here. An
alternative (with equivalent result) would be to use a
real-valued (structured) channel matrix of twice the
dimension.
*/
if (k % Tc == 0) { // generate a new channel realization every Tc intervals
H(k / Tc) = Ess * randn_c(nRx, nTx);
}
// modulate and transmit bits
bvec bitstmp = txbits(k * 2 * nTx * nC, (k + 1) * 2 * nTx * nC - 1);
cvec x = chan.modulate_bits(bitstmp);
cvec e = sqrt(sigma2) * randn_c(nRx);
Y(k) = H(k / Tc) * x + e;
}
// -- demodulate --
Array<QLLRvec> LLRin(Nmethods);
for (int i = 0; i < Nmethods; i++) {
LLRin(i) = zeros_i(Nctx);
}
QLLRvec llr_apr = zeros_i(nC * 2 * nTx); // no a priori input to demodulator
QLLRvec llr_apost = zeros_i(nC * 2 * nTx);
for (int k = 0; k < Nvec; k++) {
// zero forcing demodulation
if (Contflag(0)) {
chan.demodulate_soft_bits(Y(k), H(k / Tc), sigma2, llr_apr, llr_apost,
ND_UQAM::ZF_LOGMAP);
LLRin(0).set_subvector(k*Nbitspvec, llr_apost);
}
// ML demodulation
if (Contflag(1)) {
chan.demodulate_soft_bits(Y(k), H(k / Tc), sigma2, llr_apr, llr_apost);
LLRin(1).set_subvector(k*Nbitspvec, llr_apost);
}
}
// -- decode and count errors --
for (int i = 0; i < Nmethods; i++) {
bvec decoded_bits;
if (Contflag(i)) {
bercu(i).count(txbits(0, Nc - 1), LLRin(i)(0, Nc - 1) < 0); // uncoded BER
LLRin(i) = sequence_interleaver_i.deinterleave(LLRin(i), 0);
// QLLR values must be converted to real numbers since the convolutional decoder wants this
vec llr = chan.get_llrcalc().to_double(LLRin(i).left(Nc));
// llr=-llr; // UNCOMMENT THIS LINE IF COMPILING WITH 3.10.5 OR EARLIER (BEFORE HARMONIZING LLR CONVENTIONS)
code.decode_tail(llr, decoded_bits);
berc(i).count(inputbits(0, Nu - 1), decoded_bits(0, Nu - 1)); // coded BER
ferc(i).count(inputbits(0, Nu - 1), decoded_bits(0, Nu - 1)); // coded FER
}
}
/* Check whether it is time to terminate the simulation.
Terminate when all demodulators that are still running have
counted at least Nbers or Nfers bit/frame errors. */
int minber = 1000000;
int minfer = 1000000;
for (int i = 0; i < Nmethods; i++) {
if (Contflag(i)) {
minber = min(minber, round_i(berc(i).get_errors()));
minfer = min(minfer, round_i(ferc(i).get_errors()));
}
}
if (Nbers > 0 && minber > Nbers) { break;}
if (Nfers > 0 && minfer > Nfers) { break;}
}
cout << "-----------------------------------------------------" << endl;
cout << "Eb/N0: " << EbN0db(nsnr) << " dB. Simulated " << nbits << " bits." << endl;
cout << " Uncoded BER: " << bercu(0).get_errorrate() << " (ZF); " << bercu(1).get_errorrate() << " (ML)" << endl;
cout << " Coded BER: " << berc(0).get_errorrate() << " (ZF); " << berc(1).get_errorrate() << " (ML)" << endl;
cout << " Coded FER: " << ferc(0).get_errorrate() << " (ZF); " << ferc(1).get_errorrate() << " (ML)" << endl;
cout.flush();
/* Check wheter it is time to terminate simulation. Stop when all
methods have reached the min BER/FER of interest. */
int contflag = 0;
for (int i = 0; i < Nmethods; i++) {
if (Contflag(i)) {
if (berc(i).get_errorrate() > BERmin) { contflag = 1; }
else { Contflag(i) = 0; }
if (ferc(i).get_errorrate() > FERmin) { contflag = 1; }
else { Contflag(i) = 0; }
}
}
if (contflag) { continue; }
else {break; }
}
return 0;
}
int main(void)
{
//general parameters
double threshold_value = 50;
string map_metric="logMAP";
ivec gen = "037 021";//octal form
int constraint_length = 5;
int nb_errors_lim = 1500;
int nb_bits_lim = int(1e6);
int perm_len = pow2i(14);//permutation length
int nb_iter = 10;//number of iterations in the turbo decoder
vec EbN0_dB = "0:0.1:5";
double R = 1.0/4.0;//coding rate (non punctured SCCC)
double Ec = 1.0;//coded bit energy
//other parameters
string filename = "Res/sccc_"+map_metric+".it";
int nb_bits_tail = perm_len/gen.length();
int nb_bits = nb_bits_tail-(constraint_length-1);//number of bits in a block (without tail)
vec sigma2 = (0.5*Ec/R)*pow(inv_dB(EbN0_dB), -1.0);//N0/2
double Lc;//scaling factor for intrinsic information
int nb_blocks;//number of blocks
int nb_errors;
bvec bits(nb_bits);//data bits
bvec nsc_coded_bits;//tail is added
bmat rsc_parity_bits;
ivec perm(perm_len);
ivec inv_perm(perm_len);
int rec_len = gen.length()*perm_len;
bvec coded_bits(rec_len);
vec rec(rec_len);
//SISO RSC
vec rsc_intrinsic_coded(rec_len);
vec rsc_apriori_data(perm_len);
vec rsc_extrinsic_coded;
vec rsc_extrinsic_data;
//SISO NSC
vec nsc_intrinsic_coded(perm_len);
vec nsc_apriori_data(nb_bits_tail);
nsc_apriori_data.zeros();//always zero
vec nsc_extrinsic_coded;
vec nsc_extrinsic_data;
//decision
bvec rec_bits(nb_bits_tail);
int snr_len = EbN0_dB.length();
mat ber(nb_iter,snr_len);
ber.zeros();
register int en,n;
//Non recursive non Systematic Convolutional Code
Convolutional_Code nsc;
nsc.set_generator_polynomials(gen, constraint_length);
//Recursive Systematic Convolutional Code
Rec_Syst_Conv_Code rsc;
rsc.set_generator_polynomials(gen, constraint_length);//initial state should be the zero state
//BPSK modulator
BPSK bpsk;
//AWGN channel
AWGN_Channel channel;
//SISO blocks
SISO siso;
siso.set_generators(gen, constraint_length);
siso.set_map_metric(map_metric);
//BER
BERC berc;
//Progress timer
tr::Progress_Timer timer;
timer.set_max(snr_len);
//Randomize generators
RNG_randomize();
//main loop
timer.progress(0.0);
for (en=0;en<snr_len;en++)
{
channel.set_noise(sigma2(en));
Lc = -2.0/sigma2(en);//take into account the BPSK mapping
nb_errors = 0;
nb_blocks = 0;
while ((nb_errors<nb_errors_lim) && (nb_blocks*nb_bits<nb_bits_lim))//if at the last iteration the nb. of errors is inferior to lim, then process another block
{
//permutation
perm = sort_index(randu(perm_len));
//inverse permutation
inv_perm = sort_index(perm);
//bits generation
bits = randb(nb_bits);
//serial concatenated convolutional code
nsc.encode_tail(bits, nsc_coded_bits);//tail is added here to information bits to close the trellis
nsc_coded_bits = nsc_coded_bits(perm);//interleave
rsc.encode(nsc_coded_bits, rsc_parity_bits);//no tail added
for(n=0;n<perm_len;n++)
{
coded_bits(2*n) = nsc_coded_bits(n);//systematic output
coded_bits(2*n+1) = rsc_parity_bits(n,0);//parity output
}
//BPSK modulation (1->-1,0->+1) + channel
rec = channel(bpsk.modulate_bits(coded_bits));
//turbo decoder
rsc_intrinsic_coded = Lc*rec;//intrinsic information of coded bits
rsc_apriori_data.zeros();//a priori LLR for information bits
for (n=0;n<nb_iter;n++)
{
//first decoder
siso.rsc(rsc_extrinsic_coded, rsc_extrinsic_data, rsc_intrinsic_coded, rsc_apriori_data, false);
//deinterleave+threshold
nsc_intrinsic_coded = threshold(rsc_extrinsic_data(inv_perm), threshold_value);
//second decoder
siso.nsc(nsc_extrinsic_coded, nsc_extrinsic_data, nsc_intrinsic_coded, nsc_apriori_data, true);
//decision
rec_bits = bpsk.demodulate_bits(-nsc_extrinsic_data);//suppose that a priori info is zero
//count errors
berc.clear();
berc.count(bits, rec_bits.left(nb_bits));
ber(n,en) += berc.get_errorrate();
//interleave
rsc_apriori_data = nsc_extrinsic_coded(perm);
}//end iterations
nb_errors += int(berc.get_errors());//get number of errors at the last iteration
nb_blocks++;
}//end blocks (while loop)
//compute BER over all tx blocks
ber.set_col(en, ber.get_col(en)/nb_blocks);
//show progress
timer.progress(1+en);
}
timer.toc_print();
#ifdef TO_FILE
//save results to file
it_file ff(filename);
ff << Name("BER") << ber;
ff << Name("EbN0_dB") << EbN0_dB;
ff << Name("gen") << gen;
ff << Name("R") << R;
ff << Name("nb_iter") << nb_iter;
ff << Name("total_nb_bits") << nb_bits;
ff << Name("nb_errors_lim") << nb_errors_lim;
ff << Name("nb_bits_lim") << nb_bits_lim;
ff.close();
#else
//show BER
cout << ber << endl;
#endif
return 0;
}
int main(void)
{
//general parameters
double threshold_value = 50;
string map_metric = "maxlogMAP";
ivec gen = "07 05";//octal notation
int constraint_length = 3;
int ch_nb_taps = 4;//number of channel multipaths
int nb_errors_lim = 3000;
int nb_bits_lim = int(1e6);
int perm_len = pow2i(14);//permutation length
int nb_iter = 10;//number of iterations in the turbo decoder
vec EbN0_dB = "0:0.5:10";
double R = 1.0 / 2.0;//coding rate of FEC
double Ec = 1.0;//coded bit energy
#ifdef USE_PRECODER
ivec prec_gen = "03 02";//octal notation
int prec_gen_length = 2;
#endif
//other parameters
int nb_bits_tail = perm_len / gen.length();
int nb_bits = nb_bits_tail - (constraint_length - 1);//number of bits in a block (without tail)
vec sigma2 = (0.5 * Ec / R) * pow(inv_dB(EbN0_dB), -1.0);//N0/2
int nb_blocks;//number of blocks
int nb_errors;
bvec bits(nb_bits);//data bits
bvec nsc_coded_bits(perm_len);//tail is added
bvec em_bits(perm_len);
bmat parity_bits;
ivec perm(perm_len);
ivec inv_perm(perm_len);
vec rec(perm_len);
//SISO equalizer
vec eq_apriori_data(perm_len);
vec eq_extrinsic_data;
//SISO NSC
vec nsc_intrinsic_coded(perm_len);
vec nsc_apriori_data(nb_bits_tail);
nsc_apriori_data.zeros();//always zero
vec nsc_extrinsic_coded;
vec nsc_extrinsic_data;
//decision
bvec rec_bits(nb_bits_tail);
int snr_len = EbN0_dB.length();
mat ber(nb_iter, snr_len);
ber.zeros();
register int en, n;
//CCs
Convolutional_Code nsc;
nsc.set_generator_polynomials(gen, constraint_length);
#ifdef USE_PRECODER
Rec_Syst_Conv_Code prec;
prec.set_generator_polynomials(prec_gen, prec_gen_length);
#endif
//BPSK
BPSK bpsk;
//AWGN
AWGN_Channel awgn;
//multipath channel impulse response (Rayleigh fading) with real coefficients
vec ch_imp_response(ch_nb_taps);
vec ini_state = ones(ch_nb_taps);//initial state is zero
MA_Filter<double, double, double> multipath_channel;
//SISO blocks
SISO siso;
siso.set_generators(gen, constraint_length);
siso.set_map_metric(map_metric);
#ifdef USE_PRECODER
siso.set_precoder_generator(prec_gen(0), prec_gen_length);
#endif
//BER
BERC berc;
//Randomize generators
RNG_randomize();
//main loop
for (en = 0;en < snr_len;en++) {
cout << "EbN0_dB = " << EbN0_dB(en) << endl;
awgn.set_noise(sigma2(en));
siso.set_noise(sigma2(en));
nb_errors = 0;
nb_blocks = 0;
while ((nb_errors < nb_errors_lim) && (nb_blocks*nb_bits < nb_bits_lim))//if at the last iteration the nb. of errors is inferior to lim, then process another block
{
//permutation
perm = sort_index(randu(perm_len));
//inverse permutation
inv_perm = sort_index(perm);
//bits generation
bits = randb(nb_bits);
//convolutional code
nsc.encode_tail(bits, nsc_coded_bits);//tail is added here to information bits to close the trellis
//permutation
em_bits = nsc_coded_bits(perm);
#ifdef USE_PRECODER
//precoder
prec.encode(em_bits, parity_bits);
em_bits = parity_bits.get_col(0);
#endif
//BPSK modulation (1->-1,0->+1) + multipath channel
ch_imp_response = randray(ch_nb_taps);
ch_imp_response /= sqrt(sum_sqr(ch_imp_response));//normalized power profile
multipath_channel.set_coeffs(ch_imp_response);
multipath_channel.set_state(ini_state);//inital state is zero
rec = awgn(multipath_channel(bpsk.modulate_bits(em_bits)));
//turbo equalizer
eq_apriori_data.zeros();//a priori information of emitted symbols
siso.set_impulse_response(ch_imp_response);
for (n = 0;n < nb_iter;n++)
{
//first decoder
siso.equalizer(eq_extrinsic_data, rec, eq_apriori_data, false);//no tail
//deinterleave+threshold
nsc_intrinsic_coded = SISO::threshold(eq_extrinsic_data(inv_perm), threshold_value);
//second decoder
siso.nsc(nsc_extrinsic_coded, nsc_extrinsic_data, nsc_intrinsic_coded, nsc_apriori_data, true);//tail
//decision
rec_bits = bpsk.demodulate_bits(-nsc_extrinsic_data);//assume that a priori info is zero
//count errors
berc.clear();
berc.count(bits, rec_bits.left(nb_bits));
ber(n, en) += berc.get_errorrate();
//interleave
eq_apriori_data = nsc_extrinsic_coded(perm);
}//end iterations
nb_errors += int(berc.get_errors());//get number of errors at the last iteration
nb_blocks++;
}//end blocks (while loop)
//compute BER over all tx blocks
ber.set_col(en, ber.get_col(en) / nb_blocks);
}
//save results to file
it_file ff("turbo_equalizer_bersim_multipath.it");
ff << Name("BER") << ber;
ff << Name("EbN0_dB") << EbN0_dB;
ff.close();
return 0;
}
