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compensate using comb type pilots
This commit is contained in:
Ahmet Inan
parent
71cc33e481
commit
b93079de81
2 changed files with 66 additions and 47 deletions
81
decode.cc
81
decode.cc
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@ -181,7 +181,11 @@ struct Decoder
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static const int guard_len = symbol_len / 8;
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static const int extended_len = symbol_len + guard_len;
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static const int max_bits = 2720 + 32;
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static const int cons_cols = 256;
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static const int comb_cols = 8;
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static const int code_cols = 256;
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static const int cons_cols = code_cols + comb_cols;
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static const int comb_dist = cons_cols / comb_cols;
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static const int comb_off = comb_dist / 2;
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static const int cons_rows = 4;
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static const int cons_total = cons_rows * cons_cols;
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static const int code_off = - cons_cols / 2;
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@ -198,7 +202,7 @@ struct Decoder
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DSP::BlockDC<value, value> blockdc;
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DSP::Hilbert<cmplx, filter_len> hilbert;
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DSP::BipBuffer<cmplx, buffer_len> input_hist;
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DSP::TheilSenEstimator<value, cons_cols> tse;
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DSP::TheilSenEstimator<value, comb_cols> tse;
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SchmidlCox<value, cmplx, search_pos, symbol_len/2, guard_len> correlator;
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CODE::CRC<uint16_t> crc0;
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CODE::CRC<uint32_t> crc1;
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@ -211,7 +215,7 @@ struct Decoder
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code_type code[code_len];
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cmplx cons[cons_total], prev[cons_cols];
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cmplx fdom[symbol_len], tdom[symbol_len];
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value index[cons_cols], phase[cons_cols];
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value index[comb_cols], phase[comb_cols];
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value cfo_rad, sfo_rad;
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const uint32_t *frozen_bits;
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int symbol_pos;
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@ -361,6 +365,7 @@ struct Decoder
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for (int i = 0; i < cons_cols; ++i)
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prev[i] = fdom[bin(i+code_off)];
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std::cerr << "demod ";
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CODE::MLS seq0(mls0_poly);
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for (int j = 0; j < cons_rows; ++j) {
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for (int i = 0; i < extended_len; ++i)
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buf = next_sample();
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@ -371,48 +376,46 @@ struct Decoder
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fwd(fdom, tdom);
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for (int i = 0; i < cons_cols; ++i)
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cons[cons_cols*j+i] = demod_or_erase(fdom[bin(i+code_off)], prev[i]);
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if (1) {
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for (int i = 0; i < cons_cols; ++i) {
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code_type tmp[mod_bits];
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mod_hard(tmp, cons[cons_cols*j+i]);
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index[i] = i + code_off;
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phase[i] = arg(cons[cons_cols*j+i] * conj(mod_map(tmp)));
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}
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tse.compute(index, phase, cons_cols);
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//std::cerr << "Theil-Sen slope = " << tse.slope() << std::endl;
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//std::cerr << "Theil-Sen yint = " << tse.yint() << std::endl;
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for (int i = 0; i < cons_cols; ++i)
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cons[cons_cols*j+i] *= DSP::polar<value>(1, -tse(i+code_off));
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for (int i = 0; i < cons_cols; ++i)
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prev[i] *= DSP::polar<value>(1, tse(i+code_off));
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for (int i = 0; i < comb_cols; ++i)
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cons[cons_cols*j+comb_dist*i+comb_off] *= nrz(seq0());
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for (int i = 0; i < comb_cols; ++i) {
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index[i] = code_off + comb_dist * i + comb_off;
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phase[i] = arg(cons[cons_cols*j+comb_dist*i+comb_off]);
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}
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tse.compute(index, phase, comb_cols);
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//std::cerr << "Theil-Sen slope = " << tse.slope() << std::endl;
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//std::cerr << "Theil-Sen yint = " << tse.yint() << std::endl;
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for (int i = 0; i < cons_cols; ++i)
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cons[cons_cols*j+i] *= DSP::polar<value>(1, -tse(i+code_off));
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for (int i = 0; i < cons_cols; ++i)
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if (i % comb_dist == comb_off)
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prev[i] = fdom[bin(i+code_off)];
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else
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prev[i] *= DSP::polar<value>(1, tse(i+code_off));
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std::cerr << ".";
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}
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std::cerr << " done" << std::endl;
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if (1) {
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std::cerr << "Es/N0 (dB):";
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value sp = 0, np = 0;
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for (int j = 0; j < cons_rows; ++j) {
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for (int i = 0; i < cons_cols; ++i) {
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code_type tmp[mod_bits];
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mod_hard(tmp, cons[cons_cols*j+i]);
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cmplx hard = mod_map(tmp);
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cmplx error = cons[cons_cols*j+i] - hard;
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sp += norm(hard);
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np += norm(error);
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}
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value precision = sp / np;
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value snr = DSP::decibel(precision);
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std::cerr << " " << snr;
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for (int i = 0; i < cons_cols; ++i)
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mod_soft(code+mod_bits*(cons_cols*j+i), cons[cons_cols*j+i], precision);
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std::cerr << "Es/N0 (dB):";
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value sp = 0, np = 0;
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for (int j = 0, k = 0; j < cons_rows; ++j) {
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for (int i = 0; i < comb_cols; ++i) {
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cmplx hard(1, 0);
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cmplx error = cons[cons_cols*j+comb_dist*i+comb_off] - hard;
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sp += norm(hard);
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np += norm(error);
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}
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value precision = sp / np;
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// precision = 8;
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value snr = DSP::decibel(precision);
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std::cerr << " " << snr;
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for (int i = 0; i < cons_cols; ++i) {
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if (i % comb_dist == comb_off)
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continue;
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mod_soft(code+k, cons[cons_cols*j+i], precision);
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k += mod_bits;
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}
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std::cerr << std::endl;
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} else {
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value precision = 8;
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for (int i = 0; i < cons_total; ++i)
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mod_soft(code+mod_bits*i, cons[i], precision);
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}
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std::cerr << std::endl;
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int data_bits = 0;
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switch (oper_mode) {
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case 17:
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32
encode.cc
32
encode.cc
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@ -35,7 +35,11 @@ struct Encoder
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static const int symbol_len = (1280 * rate) / 8000;
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static const int guard_len = symbol_len / 8;
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static const int max_bits = 2720 + 32;
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static const int cons_cols = 256;
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static const int comb_cols = 8;
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static const int code_cols = 256;
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static const int cons_cols = code_cols + comb_cols;
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static const int comb_dist = cons_cols / comb_cols;
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static const int comb_off = comb_dist / 2;
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static const int cons_rows = 4;
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static const int mls0_len = 127;
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static const int mls0_poly = 0b10001001;
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@ -176,10 +180,10 @@ struct Encoder
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CODE::set_be_bit(data, i+55, (cs>>i)&1);
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bchenc(data, parity);
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CODE::MLS seq1(mls1_poly);
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value mls1_fac = std::sqrt(value(symbol_len) / value(mls1_len));
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value cons_fac = std::sqrt(value(symbol_len) / value(cons_cols));
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for (int i = 0; i < symbol_len; ++i)
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fdom[i] = 0;
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fdom[bin(mls1_off-1)] = mls1_fac;
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fdom[bin(mls1_off-1)] = cons_fac;
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for (int i = 0; i < 71; ++i)
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fdom[bin(i+mls1_off)] = nrz(CODE::get_be_bit(data, i));
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for (int i = 71; i < mls1_len; ++i)
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@ -188,6 +192,10 @@ struct Encoder
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fdom[bin(i+mls1_off)] *= fdom[bin(i-1+mls1_off)];
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for (int i = 0; i < mls1_len; ++i)
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fdom[bin(i+mls1_off)] *= nrz(seq1());
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for (int i = 0; i < comb_cols / 2; ++i) {
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fdom[bin(i+code_off)] = cons_fac * nrz(seq1());
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fdom[bin(i+mls1_off+mls1_len)] = cons_fac * nrz(seq1());
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}
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symbol();
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}
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cmplx mod_map(code_type *b)
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@ -247,10 +255,17 @@ struct Encoder
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shuffle(code);
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for (int i = 0; i < cons_cols; ++i)
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prev[i] = fdom[bin(i+code_off)];
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for (int j = 0; j < cons_rows; ++j) {
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for (int i = 0; i < cons_cols; ++i)
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fdom[bin(i+code_off)] = prev[i] *
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mod_map(code+mod_bits*(cons_cols*j+i));
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CODE::MLS seq0(mls0_poly);
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for (int j = 0, k = 0; j < cons_rows; ++j) {
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for (int i = 0; i < cons_cols; ++i) {
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if (i % comb_dist == comb_off) {
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prev[i] *= nrz(seq0());
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fdom[bin(i+code_off)] = prev[i];
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} else {
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fdom[bin(i+code_off)] = prev[i] * mod_map(code+k);
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k += mod_bits;
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}
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}
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symbol();
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}
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}
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@ -308,8 +323,9 @@ int main(int argc, char **argv)
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return 1;
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}
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const int comb_pilots = 8;
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const int reserved_tones = 8;
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const int band_width = 1600 + (25 * reserved_tones) / 4;
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const int band_width = 1600 + (25 * (comb_pilots + reserved_tones)) / 4;
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if ((output_chan == 1 && freq_off < band_width / 2) || freq_off < band_width / 2 - output_rate / 2 || freq_off > output_rate / 2 - band_width / 2) {
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std::cerr << "Unsupported frequency offset." << std::endl;
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