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compute descrambled constellations only once

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Ahmet Inan 2021-06-13 11:50:55 +02:00
commit 5f4c2cdba9
2 changed files with 39 additions and 58 deletions
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90
decode.cc
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@ -163,7 +163,8 @@ struct Decoder
static const int code_bits = 64800;
static const int data_bits = code_bits - 32 - 12 * 16 - 21600;
static const int code_cols = 432;
static const int code_rows = code_bits / code_cols / Mod::BITS;
static const int cons_cnt = code_bits / Mod::BITS;
static const int code_rows = cons_cnt / code_cols;
static const int code_off = -216;
static const int mls0_off = -126;
static const int mls0_len = 127;
@ -193,7 +194,7 @@ struct Decoder
int8_t genmat[255*71];
int8_t code[code_bits], bint[code_bits];
uint16_t erasures[24];
cmplx head[symbol_len], tail[symbol_len];
cmplx head[symbol_len], tail[symbol_len], cons[cons_cnt];
cmplx fdom[symbol_len], tdom[buffer_len], resam[buffer_len];
value phase[symbol_len/2];
value cfo_rad, sfo_rad;
@ -249,15 +250,15 @@ struct Decoder
}
void deinterleave()
{
for (int i = 0; i < code_bits/Mod::BITS; ++i)
for (int i = 0; i < cons_cnt; ++i)
for (int k = 0; k < Mod::BITS; ++k)
code[(code_bits/Mod::BITS)*k+i] = bint[Mod::BITS*i+k];
code[cons_cnt*k+i] = bint[Mod::BITS*i+k];
}
void interleave()
{
for (int i = 0; i < code_bits/Mod::BITS; ++i)
for (int i = 0; i < cons_cnt; ++i)
for (int k = 0; k < Mod::BITS; ++k)
bint[Mod::BITS*i+k] = code[(code_bits/Mod::BITS)*k+i];
bint[Mod::BITS*i+k] = code[cons_cnt*k+i];
}
Decoder(uint8_t *out, DSP::ReadPCM<value> *pcm, int skip_count) :
pcm(pcm), resample(rate, (rate * 19) / 40, 2), correlator(mls0_seq()), crc0(0xA8F4), crc1(0xD419CC15)
@ -353,25 +354,27 @@ struct Decoder
tdom[i] = resam[i] * osc();
CODE::MLS seq3(mls3_poly), seq4(mls4_poly);
cmplx *cur = tdom + symbol_pos - (code_rows + 1) * (symbol_len + guard_len);
fwd(fdom, cur);
for (int j = 0; j < code_rows; ++j) {
for (int i = 0; i < code_cols; ++i)
head[bin(i+code_off)] = fdom[bin(i+code_off)];
fwd(fdom, cur += symbol_len+guard_len);
for (int i = 0; i < code_cols; ++i) {
cmplx con = fdom[bin(i+code_off)] / head[bin(i+code_off)];
cons[code_cols*j+i] = cmplx(con.real() * (1 - 2 * seq3()), con.imag() * (1 - 2 * seq4()));
}
}
value precision = 16;
if (1) {
cmplx *cur = tdom + symbol_pos - (code_rows + 1) * (symbol_len + guard_len);
fwd(fdom, cur);
value sp = 0, np = 0;
for (int j = 0; j < code_rows; ++j) {
for (int i = 0; i < code_cols; ++i)
head[bin(i+code_off)] = fdom[bin(i+code_off)];
fwd(fdom, cur += symbol_len+guard_len);
for (int i = 0; i < code_cols; ++i) {
int8_t tmp[Mod::BITS];
cmplx con = fdom[bin(i+code_off)] / head[bin(i+code_off)];
con = cmplx(con.real() * (1 - 2 * seq3()), con.imag() * (1 - 2 * seq4()));
Mod::hard(tmp, con);
cmplx hard = Mod::map(tmp);
cmplx error = con - hard;
sp += norm(hard);
np += norm(error);
}
for (int i = 0; i < cons_cnt; ++i) {
int8_t tmp[Mod::BITS];
Mod::hard(tmp, cons[i]);
cmplx hard = Mod::map(tmp);
cmplx error = cons[i] - hard;
sp += norm(hard);
np += norm(error);
}
value snr = DSP::decibel(sp / np);
std::cerr << "init Es/N0: " << snr << " dB" << std::endl;
@ -380,46 +383,23 @@ struct Decoder
value sigma = std::sqrt(np / (2 * sp));
precision = 1 / (sigma * sigma);
}
cmplx *cur = tdom + symbol_pos - (code_rows + 1) * (symbol_len + guard_len);
fwd(fdom, cur);
seq3.reset();
seq4.reset();
for (int j = 0; j < code_rows; ++j) {
for (int i = 0; i < code_cols; ++i)
head[bin(i+code_off)] = fdom[bin(i+code_off)];
fwd(fdom, cur += symbol_len+guard_len);
for (int i = 0; i < code_cols; ++i) {
cmplx con = fdom[bin(i+code_off)] / head[bin(i+code_off)];
con = cmplx(con.real() * (1 - 2 * seq3()), con.imag() * (1 - 2 * seq4()));
Mod::soft(bint+Mod::BITS*(code_cols*j+i), con, precision);
}
}
for (int i = 0; i < cons_cnt; ++i)
Mod::soft(bint+Mod::BITS*i, cons[i], precision);
deinterleave();
int count = ldpcdec(code, code+data_bits+32+12*16);
if (count < 0)
std::cerr << "payload LDPC decoding did not converge." << std::endl;
if (1) {
interleave();
cmplx *cur = tdom + symbol_pos - (code_rows + 1) * (symbol_len + guard_len);
fwd(fdom, cur);
seq3.reset();
seq4.reset();
value sp = 0, np = 0;
for (int j = 0; j < code_rows; ++j) {
for (int i = 0; i < code_cols; ++i)
head[bin(i+code_off)] = fdom[bin(i+code_off)];
fwd(fdom, cur += symbol_len+guard_len);
for (int i = 0; i < code_cols; ++i) {
int8_t tmp[Mod::BITS];
for (int k = 0; k < Mod::BITS; ++k)
tmp[k] = 1 - 2 * (bint[Mod::BITS*(code_cols*j+i)+k] < 0);
cmplx con = fdom[bin(i+code_off)] / head[bin(i+code_off)];
con = cmplx(con.real() * (1 - 2 * seq3()), con.imag() * (1 - 2 * seq4()));
cmplx hard = Mod::map(tmp);
cmplx error = con - hard;
sp += norm(hard);
np += norm(error);
}
for (int i = 0; i < cons_cnt; ++i) {
int8_t tmp[Mod::BITS];
for (int k = 0; k < Mod::BITS; ++k)
tmp[k] = 1 - 2 * (bint[Mod::BITS*i+k] < 0);
cmplx hard = Mod::map(tmp);
cmplx error = cons[i] - hard;
sp += norm(hard);
np += norm(error);
}
value snr = DSP::decibel(sp / np);
std::cerr << "corr Es/N0: " << snr << " dB" << std::endl;

7
encode.cc
View file

@ -31,7 +31,8 @@ struct Encoder
static const int code_bits = 64800;
static const int data_bits = code_bits - 32 - 12 * 16 - 21600;
static const int code_cols = 432;
static const int code_rows = code_bits / code_cols / Mod::BITS;
static const int cons_cnt = code_bits / Mod::BITS;
static const int code_rows = cons_cnt / code_cols;
static const int mls0_len = 127;
static const int mls0_poly = 0b10001001;
static const int mls1_len = 255;
@ -140,9 +141,9 @@ struct Encoder
}
void interleave()
{
for (int i = 0; i < code_bits/Mod::BITS; ++i)
for (int i = 0; i < cons_cnt; ++i)
for (int k = 0; k < Mod::BITS; ++k)
bint[Mod::BITS*i+k] = code[(code_bits/Mod::BITS)*k+i];
bint[Mod::BITS*i+k] = code[cons_cnt*k+i];
}
Encoder(DSP::WritePCM<value> *pcm, uint8_t *inp, int freq_off, uint64_t call_sign) :
pcm(pcm), crc0(0xA8F4), crc1(0xD419CC15), bchenc0({