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erase weak subcarriers

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This commit is contained in:
Ahmet Inan 2023-12-13 17:15:21 +01:00
commit 12c11b84c9
1 changed files with 10 additions and 6 deletions
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16
decode.cc
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@ -48,7 +48,7 @@ struct SchmidlCox
DSP::SchmittTrigger<value> threshold;
DSP::FallingEdgeTrigger falling;
cmplx tmp0[symbol_len], tmp1[symbol_len], tmp2[symbol_len];
cmplx seq[symbol_len], kern[symbol_len];
cmplx kern[symbol_len];
cmplx cmplx_shift = 0;
value timing_max = 0;
value phase_max = 0;
@ -58,9 +58,11 @@ struct SchmidlCox
{
return (carrier + symbol_len) % symbol_len;
}
static cmplx demod_or_erase(cmplx curr, cmplx prev)
static cmplx demod_or_erase(cmplx curr, cmplx prev, value pwr)
{
if (!(norm(prev) > 0))
if (!(norm(curr) > pwr))
return 0;
if (!(norm(prev) > pwr))
return 0;
cmplx cons = curr / prev;
if (!(norm(cons) <= 4))
@ -74,8 +76,6 @@ public:
SchmidlCox(const cmplx *sequence) : threshold(value(0.17*match_len), value(0.19*match_len))
{
for (int i = 0; i < symbol_len; ++i)
seq[i] = sequence[i];
fwd(kern, sequence);
for (int i = 0; i < symbol_len; ++i)
kern[i] = conj(kern[i]) / value(symbol_len);
@ -116,8 +116,12 @@ public:
for (int i = 0; i < symbol_len; ++i)
tmp1[i] = samples[i+symbol_pos+symbol_len] * osc();
fwd(tmp0, tmp1);
value min_pwr = 0;
for (int i = 0; i < symbol_len; ++i)
tmp1[i] = demod_or_erase(tmp0[i], tmp0[bin(i-1)]);
min_pwr += norm(tmp0[i]);
min_pwr /= symbol_len;
for (int i = 0; i < symbol_len; ++i)
tmp1[i] = demod_or_erase(tmp0[i], tmp0[bin(i-1)], min_pwr);
fwd(tmp0, tmp1);
for (int i = 0; i < symbol_len; ++i)
tmp0[i] *= kern[i];