Mirror/aicodix___modem
1
0
Fork 0
mirror of https://github.com/aicodix/modem.git synced 2026-04-27 22:35:41 +00:00
Code Issues Projects Releases Packages Wiki Activity

limit introduced noise to active carriers only

Browse source
This commit is contained in:
Ahmet Inan 2021-06-14 15:52:53 +02:00
commit 42144b8e8a
1 changed files with 19 additions and 4 deletions
Download patch file Download diff file Expand all files Collapse all files

23
encode.cc
View file

@ -42,6 +42,7 @@ struct Encoder
static const int mls3_poly = 0b10001000000001011;
static const int mls4_poly = 0b10111010010000001;
DSP::WritePCM<value> *pcm;
DSP::FastFourierTransform<symbol_len, cmplx, -1> fwd;
DSP::FastFourierTransform<symbol_len, cmplx, 1> bwd;
CODE::CRC<uint16_t> crc0;
CODE::BoseChaudhuriHocquenghemEncoder<255, 71> bchenc0;
@ -50,6 +51,7 @@ struct Encoder
int8_t code[ldpc_bits], bint[ldpc_bits];
cmplx fdom[symbol_len];
cmplx tdom[symbol_len];
cmplx temp[symbol_len];
cmplx guard[guard_len];
cmplx papr_min, papr_max;
int code_off;
@ -64,16 +66,29 @@ struct Encoder
{
return 1 - 2 * bit;
}
void symbol()
void improve_papr()
{
bwd(tdom, fdom);
for (int i = 0; i < symbol_len; ++i)
tdom[i] /= sqrt(value(4 * symbol_len));
for (int i = 0; i < symbol_len; ++i) {
value amp = std::max(std::abs(tdom[i].real()), std::abs(tdom[i].imag()));
if (amp > value(1))
tdom[i] /= amp;
}
fwd(temp, tdom);
for (int i = 0; i < symbol_len; ++i)
if (norm(fdom[i]))
temp[i] /= sqrt(value(symbol_len));
else
temp[i] = 0;
bwd(tdom, temp);
for (int i = 0; i < symbol_len; ++i)
tdom[i] /= sqrt(value(symbol_len));
}
void symbol()
{
bwd(tdom, fdom);
for (int i = 0; i < symbol_len; ++i)
tdom[i] /= sqrt(value(4 * symbol_len));
improve_papr();
for (int i = 0; i < guard_len; ++i) {
value x = value(i) / value(guard_len - 1);
x = value(0.5) * (value(1) - std::cos(DSP::Const<value>::Pi() * x));