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split pilot tones to get more side info bits

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This commit is contained in:
Ahmet Inan 2025-07-11 14:24:00 +02:00
commit 1caa5b174e
3 changed files with 74 additions and 50 deletions
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79
decode.cc
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@ -49,7 +49,7 @@ struct Decoder : Common
DSP::BipBuffer<cmplx, buffer_len> input_hist;
DSP::TheilSenEstimator<value, tone_count> tse;
SchmidlCox<value, cmplx, search_pos, symbol_len, guard_len> correlator;
CODE::HadamardDecoder<7> hadamard_decoder;
CODE::HadamardDecoder<6> hadamard_decoder;
CODE::PolarListDecoder<mesg_type, code_max> polar_decoder;
mesg_type mesg[bits_max];
code_type code[bits_max], perm[bits_max];
@ -232,14 +232,16 @@ struct Decoder : Common
fwd(fdom, tdom);
CODE::MLS seq1(mls1_poly);
auto clamp = [](int v){ return v < -127 ? -127 : v > 127 ? 127 : v; };
for (int i = 0; i < pilot_tones; ++i)
meta[i] = clamp(std::nearbyint(127 * demod_or_erase(fdom[bin(i*block_length+first_pilot+tone_off)], chan[i*block_length+first_pilot]).real() * nrz(seq1())));
int mode = hadamard_decoder(meta) & 31;
for (int i = 0; i < meta_tones; ++i) {
meta[i] = clamp(std::nearbyint(127 * demod_or_erase(fdom[bin(i*block_length+first_meta+tone_off)], chan[i*block_length+first_meta]).real() * nrz(seq1())));
seq1();
}
int mode = hadamard_decoder(meta);
if (mode < 0 || mode > 27) {
std::cerr << "operation mode " << mode << " unsupported." << std::endl;
continue;
}
oper_mode = mode;
setup(mode);
std::cerr << "oper mode: " << oper_mode << std::endl;
if (oper_mode >= 10) {
for (int i = 0; i < tone_count; ++i)
@ -247,10 +249,10 @@ struct Decoder : Common
for (int i = 0; i < tone_count; ++i)
chan[i] = DSP::lerp(chan[i], tone[i], value(0.5));
}
setup(oper_mode);
value worst = 1000;
for (int j = 0, k = 0; j < symbol_count; ++j) {
pilot_off = (block_skew * j + first_pilot) % block_length;
meta_off = (block_skew * j + first_meta) % block_length;
seed_off = (block_skew * j + first_seed) % block_length;
if (j) {
for (int i = 0; i < extended_len; ++i)
correlator(buf = next_sample());
@ -268,23 +270,36 @@ struct Decoder : Common
}
for (int i = 0; i < tone_count; ++i)
tone[i] = fdom[bin(i+tone_off)];
for (int i = 0; i < pilot_tones; ++i)
tone[block_length*i+pilot_off] *= nrz(seq1());
for (int i = 0; i < tone_count; ++i)
if (i % block_length == meta_off || i % block_length == seed_off)
tone[i] *= nrz(seq1());
for (int i = 0; i < tone_count; ++i)
demod[i] = demod_or_erase(tone[i], chan[i]);
for (int i = 0; i < pilot_tones; ++i)
meta[i] = clamp(std::nearbyint(127 * demod[i*block_length+pilot_off].real()));
for (int i = 0; i < meta_tones; ++i)
meta[i] = clamp(std::nearbyint(127 * demod[i*block_length+meta_off].real()));
int meta_data = hadamard_decoder(meta);
hadamard_encoder(meta, meta_data);
for (int i = 0; i < pilot_tones; ++i) {
tone[block_length*i+pilot_off] *= meta[i];
demod[block_length*i+pilot_off] *= meta[i];
for (int i = 0; i < meta_tones; ++i) {
tone[block_length*i+meta_off] *= meta[i];
demod[block_length*i+meta_off] *= meta[i];
}
for (int i = 0; i < pilot_tones; ++i) {
index[i] = tone_off + block_length * i + pilot_off;
phase[i] = arg(demod[block_length*i+pilot_off]);
for (int i = 0; i < meta_tones; ++i) {
index[i] = tone_off + block_length * i + meta_off;
phase[i] = arg(demod[block_length*i+meta_off]);
}
tse.compute(index, phase, pilot_tones);
for (int i = 0; i < seed_tones; ++i)
seed[i] = clamp(std::nearbyint(127 * demod[i*block_length+seed_off].real()));
int seed_data = hadamard_decoder(seed);
hadamard_encoder(seed, seed_data);
for (int i = 0; i < seed_tones; ++i) {
tone[block_length*i+seed_off] *= seed[i];
demod[block_length*i+seed_off] *= seed[i];
}
for (int i = 0; i < seed_tones; ++i) {
index[i+meta_tones] = tone_off + block_length * i + seed_off;
phase[i+meta_tones] = arg(demod[block_length*i+seed_off]);
}
tse.compute(index, phase, meta_tones + seed_tones);
//std::cerr << "Theil-Sen slope = " << tse.slope() << std::endl;
//std::cerr << "Theil-Sen yint = " << tse.yint() << std::endl;
for (int i = 0; i < tone_count; ++i)
@ -295,17 +310,19 @@ struct Decoder : Common
for (int i = 0; i < tone_count; ++i)
chan[i] = fdom[bin(i+tone_off)];
} else {
for (int i = pilot_off; i < tone_count; i += block_length)
for (int i = meta_off; i < tone_count; i += block_length)
chan[i] = DSP::lerp(chan[i], tone[i], value(0.5));
for (int i = seed_off; i < tone_count; i += block_length)
chan[i] = DSP::lerp(chan[i], tone[i], value(0.5));
}
CODE::MLS seq2(mls2_poly, meta_data);
CODE::MLS seq2(mls2_poly, seed_data);
for (int i = 0; i < tone_count; ++i)
if (i % block_length != pilot_off)
if (i % block_length != meta_off && i % block_length != seed_off)
demod[i] *= nrz(seq2());
value sp = 0, np = 0;
for (int i = 0, l = k; i < tone_count; ++i) {
cmplx hard(1, 0);
if (i % block_length != pilot_off) {
if (i % block_length != meta_off && i % block_length != seed_off) {
int bits = mod_bits;
if (oper_mode >= 7 && oper_mode <= 9 && l % 32 == 30)
bits = 2;
@ -323,15 +340,15 @@ struct Decoder : Common
worst = std::min(worst, precision);
precision = std::min(precision, value(127));
for (int i = 0; i < tone_count; ++i) {
if (i % block_length == pilot_off)
continue;
int bits = mod_bits;
if (oper_mode >= 7 && oper_mode <= 9 && k % 32 == 30)
bits = 2;
if (oper_mode >= 21 && oper_mode <= 23 && k % 64 == 60)
bits = 4;
demap_soft(perm+k, demod[i], precision, bits);
k += bits;
if (i % block_length != meta_off && i % block_length != seed_off) {
int bits = mod_bits;
if (oper_mode >= 7 && oper_mode <= 9 && k % 32 == 30)
bits = 2;
if (oper_mode >= 21 && oper_mode <= 23 && k % 64 == 60)
bits = 4;
demap_soft(perm+k, demod[i], precision, bits);
k += bits;
}
}
}
std::cerr << "Es/N0 (dB): " << DSP::decibel(worst) << std::endl;