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https://github.com/aicodix/modem.git
synced 2026-04-27 14:30:34 +00:00
integrated new preamble
This commit is contained in:
Ahmet Inan
parent
b8fb5e7dd6
commit
bca52ea9e8
3 changed files with 80 additions and 47 deletions
100
decode.cc
100
decode.cc
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@ -177,6 +177,27 @@ struct Decoder : Common
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tmp = hilbert(blockdc(tmp.real()));
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return input_hist(tmp);
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}
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int64_t meta_data()
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{
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shuffle(code, perm, 8);
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polar_decoder(nullptr, mesg, code, frozen_256_71, 8);
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int best = -1;
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for (int k = 0; k < mesg_type::SIZE; ++k) {
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crc0.reset();
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for (int i = 0; i < 71; ++i)
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crc0(mesg[i].v[k] < 0);
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if (crc0() == 0) {
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best = k;
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break;
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}
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}
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if (best < 0)
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return -1;
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uint64_t md = 0;
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for (int i = 0; i < 55; ++i)
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md |= uint64_t(mesg[i].v[best] < 0) << i;
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return md;
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}
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Decoder(DSP::ReadPCM<value> *pcm, const char *const *output_names, int output_count) : pcm(pcm), correlator(mls0_seq())
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{
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blockdc.samples(filter_len);
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@ -210,12 +231,6 @@ struct Decoder : Common
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fwd(fdom, tdom);
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for (int i = 0; i < tone_count; ++i)
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chan[i] = fdom[bin(i+tone_off)];
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CODE::MLS seq0(mls0_poly, mls0_seed);
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for (int i = 0; i < tone_count; ++i) {
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value sign = nrz(seq0());
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tone[i] *= sign;
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chan[i] *= sign;
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}
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for (int i = 0; i < tone_count; ++i) {
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index[i] = tone_off + i;
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phase[i] = arg(demod_or_erase(chan[i], tone[i]));
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@ -223,6 +238,13 @@ struct Decoder : Common
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tse.compute(index, phase, tone_count);
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std::cerr << "coarse sfo: " << -1000000 * tse.slope() / Const::TwoPi() << " ppm" << std::endl;
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std::cerr << "residual cfo: " << 1000 * tse.yint() * rate / (Const::TwoPi() * symbol_len) << " mHz" << std::endl;
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for (int i = 0; i < tone_count; ++i)
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tone[i] *= DSP::polar<value>(1, tse(i+tone_off));
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for (int i = 0; i < tone_count; ++i)
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chan[i] = DSP::lerp(chan[i], tone[i], value(0.5));
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CODE::MLS seq0(mls0_poly, mls0_seed);
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for (int i = 0; i < tone_count; ++i)
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chan[i] *= nrz(seq0());
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for (int i = 0; i < symbol_len; ++i)
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tdom[i] = buf[i+symbol_pos+symbol_len+extended_len] * osc();
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for (int i = 0; i < guard_len; ++i)
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@ -230,24 +252,10 @@ struct Decoder : Common
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fwd(fdom, tdom);
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CODE::MLS seq1(mls1_poly);
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auto clamp = [](int v){ return v < -127 ? -127 : v > 127 ? 127 : v; };
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for (int i = 0; i < head_tones; ++i) {
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head[i] = clamp(std::nearbyint(127 * demod_or_erase(fdom[bin(i*block_length+first_head+tone_off)], chan[i*block_length+first_head]).real() * nrz(seq1())));
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seq1();
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}
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int head_data = hadamard_decoder(head);
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if (head_data < 0) {
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std::cerr << "head data damaged" << std::endl;
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continue;
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}
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setup(head_data >> 3);
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std::cerr << "oper mode: " << oper_mode << std::endl;
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if (oper_mode >= 3) {
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for (int i = 0; i < tone_count; ++i)
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tone[i] *= DSP::polar<value>(1, tse(i+tone_off));
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for (int i = 0; i < tone_count; ++i)
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chan[i] = DSP::lerp(chan[i], tone[i], value(0.5));
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}
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for (int j = 0, k = 0; j < symbol_count; ++j) {
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mod_bits = 1;
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oper_mode = -1;
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symbol_count = 0;
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for (int j = 0, k = 0; j < symbol_count + 1; ++j) {
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head_off = (block_skew * j + first_head) % block_length;
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tail_off = (block_skew * j + first_tail) % block_length;
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if (j) {
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@ -258,12 +266,6 @@ struct Decoder : Common
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for (int i = 0; i < guard_len; ++i)
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osc();
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fwd(fdom, tdom);
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for (int i = 0; i < tone_count; ++i)
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tone[i] = fdom[bin(i+tone_off)];
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} else {
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for (int i = 0; i < symbol_pos+symbol_len+extended_len; ++i)
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correlator(buf = next_sample());
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seq1.reset();
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}
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for (int i = 0; i < tone_count; ++i)
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tone[i] = fdom[bin(i+tone_off)];
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@ -311,17 +313,8 @@ struct Decoder : Common
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demod[i] *= DSP::polar<value>(1, -tse(i+tone_off));
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for (int i = 0; i < tone_count; ++i)
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chan[i] *= DSP::polar<value>(1, tse(i+tone_off));
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if (differential) {
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for (int i = 0; i < tone_count; ++i)
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chan[i] = fdom[bin(i+tone_off)];
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} else {
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for (int i = head_off; i < tone_count; i += block_length)
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chan[i] = DSP::lerp(chan[i], tone[i], value(0.5));
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for (int i = tail_off; i < tone_count; i += block_length)
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chan[i] = DSP::lerp(chan[i], tone[i], value(0.5));
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}
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CODE::XorShiftMask<int, 14, 1, 5, 10, 1> combination;
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int trial = j ? (head_data << 6) | tail_data : (head_data & 7) << 6 | tail_data;
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int trial = (head_data << 6) | tail_data;
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int comb = 0;
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for (int i = 0; i <= trial; ++i)
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comb = combination();
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@ -364,7 +357,34 @@ struct Decoder : Common
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k += bits;
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}
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}
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if (!j) {
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int64_t meta_info = meta_data();
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if (meta_info < 0) {
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std::cerr << "preamble decoding error." << std::endl;
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break;
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}
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if (meta_info > 7) {
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std::cerr << "unsupported operation mode: " << meta_info << std::endl;
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break;
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}
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k = 0;
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setup(meta_info);
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for (int i = 0; i < symbol_pos+symbol_len+extended_len; ++i)
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correlator(buf = next_sample());
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std::cerr << "oper mode: " << oper_mode << std::endl;
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}
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if (differential) {
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for (int i = 0; i < tone_count; ++i)
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chan[i] = fdom[bin(i+tone_off)];
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} else {
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for (int i = head_off; i < tone_count; i += block_length)
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chan[i] = DSP::lerp(chan[i], tone[i], value(0.5));
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for (int i = tail_off; i < tone_count; i += block_length)
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chan[i] = DSP::lerp(chan[i], tone[i], value(0.5));
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}
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}
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if (oper_mode < 1)
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continue;
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DSP::quick_sort(snr, symbol_count);
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std::cerr << "Es/N0 (dB): " << DSP::decibel(snr[0]) << " .. " << DSP::decibel(snr[symbol_count/2]) << " .. " << DSP::decibel(snr[symbol_count-1]) << std::endl;
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crc_bits = data_bits + 32;
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