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scramble I and Q using two independent sequences

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This commit is contained in:
Ahmet Inan 2021-06-11 22:52:01 +02:00
commit a07fe52134
2 changed files with 27 additions and 9 deletions
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26
decode.cc
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@ -171,6 +171,8 @@ struct Decoder
static const int mls1_len = 255;
static const int mls1_off = -127;
static const int mls1_poly = 0b100101011;
static const int mls3_poly = 0b10001000000001011;
static const int mls4_poly = 0b10111010010000001;
static const int buffer_len = (code_rows + 8) * (symbol_len + guard_len);
static const int search_pos = buffer_len - 4 * (symbol_len + guard_len);
DSP::ReadPCM<value> *pcm;
@ -337,6 +339,7 @@ struct Decoder
for (int i = 0; i < buffer_len; ++i)
tdom[i] = resam[i] * osc();
CODE::MLS seq3(mls3_poly), seq4(mls4_poly);
value precision = 16;
if (1) {
cmplx *cur = tdom + symbol_pos - (code_rows + 1) * (symbol_len + guard_len);
@ -348,10 +351,11 @@ struct Decoder
fwd(fdom, cur += symbol_len+guard_len);
for (int i = 0; i < code_cols; ++i) {
int8_t tmp[Mod::BITS];
cmplx symbol = fdom[bin(i+code_off)] / head[bin(i+code_off)];
Mod::hard(tmp, symbol);
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 = symbol - hard;
cmplx error = con - hard;
sp += norm(hard);
np += norm(error);
}
@ -365,12 +369,17 @@ struct Decoder
}
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)
Mod::soft(code+Mod::BITS*(code_cols*j+i), fdom[bin(i+code_off)]/head[bin(i+code_off)], precision);
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(code+Mod::BITS*(code_cols*j+i), con, precision);
}
}
int count = ldpcdec(code, code+data_bits+32+12*16);
if (count < 0)
@ -378,6 +387,8 @@ struct Decoder
if (1) {
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)
@ -387,9 +398,10 @@ struct Decoder
int8_t tmp[Mod::BITS];
for (int k = 0; k < Mod::BITS; ++k)
tmp[k] = 1 - 2 * (code[Mod::BITS*(code_cols*j+i)+k] < 0);
cmplx symbol = fdom[bin(i+code_off)] / head[bin(i+code_off)];
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 = symbol - hard;
cmplx error = con - hard;
sp += norm(hard);
np += norm(error);
}

10
encode.cc
View file

@ -37,6 +37,8 @@ struct Encoder
static const int mls1_len = 255;
static const int mls1_poly = 0b100101011;
static const int mls2_poly = 0b100101010001;
static const int mls3_poly = 0b10001000000001011;
static const int mls4_poly = 0b10111010010000001;
DSP::WritePCM<value> *pcm;
DSP::FastFourierTransform<symbol_len, cmplx, 1> bwd;
CODE::CRC<uint16_t> crc0;
@ -166,9 +168,13 @@ struct Encoder
for (int i = 0; i < data_bits+32+12*16; ++i)
code[i] = 1 - 2 * CODE::get_le_bit(inp, i);
ldpcenc(code, code+data_bits+32+12*16);
CODE::MLS seq3(mls3_poly), seq4(mls4_poly);
for (int j = 0; j < code_rows; ++j) {
for (int i = 0; i < code_cols; ++i)
fdom[bin(i+code_off)] *= Mod::map(code+Mod::BITS*(code_cols*j+i));
for (int i = 0; i < code_cols; ++i) {
cmplx con = Mod::map(code+Mod::BITS*(code_cols*j+i));
con = cmplx(con.real() * (1 - 2 * seq3()), con.imag() * (1 - 2 * seq4()));
fdom[bin(i+code_off)] *= con;
}
symbol();
}
schmidl_cox();