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average sync symbols only for coherent modes

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This commit is contained in:
Ahmet Inan 2025-07-07 12:32:35 +02:00
commit fcd5910db4
1 changed files with 18 additions and 15 deletions
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33
decode.cc
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@ -169,45 +169,48 @@ struct Decoder : Common
tdom[i] = buf[i+symbol_pos] * osc();
fwd(fdom, tdom);
for (int i = 0; i < tone_count; ++i)
chan[i] = fdom[bin(i+tone_off)];
tone[i] = fdom[bin(i+tone_off)];
for (int i = 0; i < symbol_len; ++i)
tdom[i] = buf[i+symbol_pos+symbol_len] * osc();
for (int i = 0; i < guard_len; ++i)
osc();
fwd(fdom, tdom);
for (int i = 0; i < tone_count; ++i)
tone[i] = fdom[bin(i+tone_off)];
chan[i] = fdom[bin(i+tone_off)];
CODE::MLS seq0(mls0_poly, mls0_seed);
for (int i = 0; i < tone_count; ++i) {
value sign = nrz(seq0());
tone[i] *= sign;
chan[i] *= sign;
}
for (int i = 0; i < tone_count; ++i) {
index[i] = tone_off + i;
phase[i] = arg(demod_or_erase(tone[i], chan[i]));
phase[i] = arg(demod_or_erase(chan[i], tone[i]));
}
tse.compute(index, phase, tone_count);
std::cerr << "coarse sfo: " << -1000000 * tse.slope() / Const::TwoPi() << " ppm" << std::endl;
std::cerr << "residual cfo: " << tse.yint() * rate / (Const::TwoPi() * symbol_len) << " Hz" << std::endl;
for (int i = 0; i < tone_count; ++i)
chan[i] *= DSP::polar<value>(1, tse(i+tone_off));
for (int i = pilot_off; i < tone_count; i += block_length)
chan[i] = DSP::lerp(chan[i], tone[i], value(0.5));
CODE::MLS seq0(mls0_poly, mls0_seed);
for (int i = 0; i < tone_count; ++i)
chan[i] *= nrz(seq0());
for (int i = 0; i < symbol_len; ++i)
tdom[i] = buf[i+symbol_pos+symbol_len+extended_len] * osc();
for (int i = 0; i < guard_len; ++i)
osc();
fwd(fdom, tdom);
for (int i = 0; i < tone_count; ++i)
tone[i] = fdom[bin(i+tone_off)];
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)
mode[i] = clamp(std::nearbyint(127 * demod_or_erase(tone[i*block_length+first_pilot], chan[i*block_length+first_pilot]).real() * nrz(seq1())));
mode[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 oper_mode = hadamard_decoder(mode);
if (oper_mode < 0 || oper_mode > 27) {
std::cerr << "operation mode " << oper_mode << " unsupported." << std::endl;
continue;
}
std::cerr << "oper mode: " << oper_mode << std::endl;
if (oper_mode >= 10) {
for (int i = 0; i < tone_count; ++i)
tone[i] *= DSP::polar<value>(1, tse(i+tone_off));
for (int i = 0; i < tone_count; ++i)
chan[i] = DSP::lerp(chan[i], tone[i], value(0.5));
}
setup(oper_mode);
std::cerr << "Es/N0 (dB):";
for (int j = 0, k = 0; j < symbol_count; ++j) {
@ -219,14 +222,14 @@ struct Decoder : Common
for (int i = 0; i < guard_len; ++i)
osc();
fwd(fdom, tdom);
for (int i = 0; i < tone_count; ++i)
tone[i] = fdom[bin(i+tone_off)];
} else {
for (int i = 0; i < symbol_pos+symbol_len+extended_len; ++i)
correlator(buf = next_sample());
seq1.reset();
hadamard_encoder(mode, oper_mode);
}
for (int i = 0; i < tone_count; ++i)
tone[i] = fdom[bin(i+tone_off)];
pilot_off = (block_skew * j + first_pilot) % block_length;
reserved_off = (block_skew * j + first_reserved) % block_length;
for (int i = 0; i < pilot_tones; ++i)