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

do the clipping in 4x oversampled time domain

Browse source
This commit is contained in:
Ahmet Inan 2021-06-14 21:43:45 +02:00
commit 40ec9a5604
1 changed files with 27 additions and 16 deletions
Download patch file Download diff file Expand all files Collapse all files

43
encode.cc
View file

@ -42,15 +42,16 @@ 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;
DSP::FastFourierTransform<4*symbol_len, cmplx, -1> fwd4;
DSP::FastFourierTransform<4*symbol_len, cmplx, 1> bwd4;
CODE::CRC<uint16_t> crc0;
CODE::BoseChaudhuriHocquenghemEncoder<255, 71> bchenc0;
CODE::BoseChaudhuriHocquenghemEncoder<65535, 65343> bchenc1;
CODE::LDPCEncoder<DVB_T2_TABLE_A3> ldpcenc;
int8_t code[ldpc_bits], bint[ldpc_bits];
cmplx fdom[symbol_len];
cmplx tdom[symbol_len];
cmplx fdom[symbol_len], fdom4[4*symbol_len];
cmplx tdom[symbol_len], tdom4[4*symbol_len];
cmplx temp[symbol_len];
cmplx guard[guard_len];
cmplx papr_min, papr_max;
@ -62,33 +63,43 @@ struct Encoder
{
return (carrier + symbol_len) % symbol_len;
}
static int bin4(int carrier)
{
return (carrier + 4*symbol_len) % (4*symbol_len);
}
static int nrz(bool bit)
{
return 1 - 2 * bit;
}
void improve_papr()
{
for (int i = 0; i < symbol_len; ++i) {
value amp = std::max(std::abs(tdom[i].real()), std::abs(tdom[i].imag()));
for (int i = 0; i < 4*symbol_len; ++i)
fdom4[i] = 0;
for (int i = -symbol_len/2; i < symbol_len/2; ++i)
fdom4[bin4(i)] = fdom[bin(i)];
bwd4(tdom4, fdom4);
for (int i = 0; i < 4*symbol_len; ++i)
tdom4[i] /= sqrt(value(4*symbol_len));
for (int i = 0; i < 4*symbol_len; ++i) {
value amp = std::max(std::abs(tdom4[i].real()), std::abs(tdom4[i].imag()));
if (amp > value(1))
tdom[i] /= amp;
tdom4[i] /= amp;
}
fwd(temp, tdom);
for (int i = 0; i < symbol_len; ++i)
if (norm(fdom[i]))
temp[i] /= sqrt(value(symbol_len));
fwd4(fdom4, tdom4);
for (int i = -symbol_len/2; i < symbol_len/2; ++i)
if (norm(temp[bin(i)]))
temp[bin(i)] = fdom4[bin4(i)] / sqrt(value(4*symbol_len));
else
temp[i] = 0;
bwd(tdom, temp);
for (int i = 0; i < symbol_len; ++i)
tdom[i] /= sqrt(value(symbol_len));
temp[bin(i)] = 0;
}
void symbol()
{
bwd(tdom, fdom);
for (int i = 0; i < symbol_len; ++i)
tdom[i] /= sqrt(value(4 * symbol_len));
temp[i] = fdom[i];
improve_papr();
bwd(tdom, temp);
for (int i = 0; i < symbol_len; ++i)
tdom[i] /= sqrt(value(8*symbol_len));
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));