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use hard decisions to estimate SNR per symbol

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This commit is contained in:
Ahmet Inan 2025-07-08 14:29:00 +02:00
commit 3bc6b7a950
1 changed files with 51 additions and 4 deletions
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55
decode.cc
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@ -85,7 +85,25 @@ struct Decoder : Common
fdom[bin(i+tone_off)] = prv * (cur = nrz(seq0()));
return fdom;
}
void demap_bits(code_type *b, cmplx c, value precision, int bits)
cmplx map_bits(code_type *b, int bits)
{
switch (bits) {
case 1:
return PhaseShiftKeying<2, cmplx, code_type>::map(b);
case 2:
return PhaseShiftKeying<4, cmplx, code_type>::map(b);
case 3:
return PhaseShiftKeying<8, cmplx, code_type>::map(b);
case 4:
return QuadratureAmplitudeModulation<16, cmplx, code_type>::map(b);
case 6:
return QuadratureAmplitudeModulation<64, cmplx, code_type>::map(b);
case 8:
return QuadratureAmplitudeModulation<256, cmplx, code_type>::map(b);
}
return 0;
}
void demap_soft(code_type *b, cmplx c, value precision, int bits)
{
switch (bits) {
case 1:
@ -102,6 +120,23 @@ struct Decoder : Common
return QuadratureAmplitudeModulation<256, cmplx, code_type>::soft(b, c, precision);
}
}
void demap_hard(code_type *b, cmplx c, int bits)
{
switch (bits) {
case 1:
return PhaseShiftKeying<2, cmplx, code_type>::hard(b, c);
case 2:
return PhaseShiftKeying<4, cmplx, code_type>::hard(b, c);
case 3:
return PhaseShiftKeying<8, cmplx, code_type>::hard(b, c);
case 4:
return QuadratureAmplitudeModulation<16, cmplx, code_type>::hard(b, c);
case 6:
return QuadratureAmplitudeModulation<64, cmplx, code_type>::hard(b, c);
case 8:
return QuadratureAmplitudeModulation<256, cmplx, code_type>::hard(b, c);
}
}
void shuffle(code_type *dest, const code_type *src)
{
if (code_order == 11) {
@ -260,9 +295,21 @@ struct Decoder : Common
chan[i] = DSP::lerp(chan[i], tone[i], value(0.5));
}
value sp = 0, np = 0;
for (int i = 0; i < pilot_tones; ++i) {
for (int i = 0, l = k; i < tone_count; ++i) {
if (i % block_length == reserved_off)
continue;
cmplx hard(1, 0);
cmplx error = demod[block_length*i+pilot_off] - hard;
if (i % block_length != pilot_off) {
int bits = mod_bits;
if (oper_mode >= 7 && oper_mode <= 9 && l % 32 == 30)
bits = 2;
if (oper_mode >= 21 && oper_mode <= 23 && l % 64 == 60)
bits = 4;
demap_hard(perm+l, demod[i], bits);
hard = map_bits(perm+l, bits);
l += bits;
}
cmplx error = demod[i] - hard;
sp += norm(hard);
np += norm(error);
}
@ -279,7 +326,7 @@ struct Decoder : Common
bits = 2;
if (oper_mode >= 21 && oper_mode <= 23 && k % 64 == 60)
bits = 4;
demap_bits(perm+k, demod[i], precision, bits);
demap_soft(perm+k, demod[i], precision, bits);
k += bits;
}
}