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preparing to play with partial transmit sequence

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This commit is contained in:
Ahmet Inan 2025-08-07 00:14:22 +02:00
commit 2c05efe8cd
3 changed files with 53 additions and 70 deletions
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45
decode.cc
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@ -29,7 +29,6 @@ namespace DSP { using std::abs; using std::min; using std::cos; using std::sin;
#include "psk.hh"
#include "qam.hh"
#include "polar_list_decoder.hh"
#include "hadamard_decoder.hh"
template <typename value, typename cmplx, int rate>
struct Decoder : Common
@ -51,7 +50,6 @@ 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::PolarListDecoder<mesg_type, code_max> polar_decoder;
mesg_type mesg[bits_max];
code_type code[bits_max], perm[bits_max];
@ -278,12 +276,11 @@ struct Decoder : Common
osc();
fwd(fdom, tdom);
CODE::MLS seq1(mls1_poly);
auto clamp = [](int v){ return v < -127 ? -127 : v > 127 ? 127 : v; };
mod_bits = 1;
oper_mode = -1;
symbol_count = 0;
for (int j = 0, k = 0; j < symbol_count + 1; ++j) {
seed_off = (block_skew * j + first_seed) % block_length;
pilot_off = (block_skew * j + first_pilot) % block_length;
if (j) {
for (int i = 0; i < extended_len; ++i)
correlator(buf = next_sample());
@ -295,44 +292,38 @@ struct Decoder : Common
}
for (int i = 0; i < tone_count; ++i)
tone[i] = fdom[bin(i+tone_off)];
for (int i = seed_off; i < tone_count; i += block_length)
for (int i = pilot_off; i < tone_count; i += block_length)
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 < seed_tones; ++i)
seed[i] = clamp(std::nearbyint(127 * demod[i*block_length+seed_off].real()));
int seed_value = hadamard_decoder(seed);
if (seed_value < 0) {
std::cerr << "seed value damaged" << std::endl;
value pilot_sum = 0;
for (int i = 0; i < pilot_tones; ++i)
pilot_sum += demod[i*block_length+pilot_off].real();
int pilot_phase = DSP::signum(pilot_sum);
if (std::abs(pilot_sum) < pilot_tones / 4) {
std::cerr << "pilot phase damaged" << std::endl;
oper_mode = -1;
break;
}
hadamard_encoder(seed, seed_value);
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 < tone_count; ++i) {
tone[i] *= pilot_phase;
demod[i] *= pilot_phase;
}
for (int i = 0; i < seed_tones; ++i) {
index[i] = tone_off + block_length * i + seed_off;
phase[i] = arg(demod[block_length*i+seed_off]);
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]);
}
tse.compute(index, phase, seed_tones);
tse.compute(index, phase, pilot_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)
demod[i] *= DSP::polar<value>(1, -tse(i+tone_off));
for (int i = 0; i < tone_count; ++i)
chan[i] *= DSP::polar<value>(1, tse(i+tone_off));
if (seed_value) {
CODE::MLS seq(mls2_poly, seed_value);
for (int i = 0; i < tone_count; ++i)
if (i % block_length != seed_off)
demod[i] *= nrz(seq());
}
value sp = 0, np = 0;
for (int i = 0, l = k; i < tone_count; ++i) {
cmplx hard(1, 0);
if (i % block_length != seed_off) {
if (i % block_length != pilot_off) {
int bits = mod_bits;
if (mod_bits == 3 && l % 32 == 30)
bits = 2;
@ -354,7 +345,7 @@ struct Decoder : Common
snr[j] = precision;
precision = std::min(precision, value(1023));
for (int i = 0; i < tone_count; ++i) {
if (i % block_length != seed_off) {
if (i % block_length != pilot_off) {
int bits = mod_bits;
if (mod_bits == 3 && k % 32 == 30)
bits = 2;
@ -391,7 +382,7 @@ struct Decoder : Common
correlator(buf = next_sample());
std::cerr << "oper mode: " << oper_mode << std::endl;
}
for (int i = seed_off; i < tone_count; i += block_length)
for (int i = pilot_off; i < tone_count; i += block_length)
chan[i] = DSP::lerp(chan[i], tone[i], value(0.5));
}
if (oper_mode < 0)