mirror of
https://github.com/aicodix/modem.git
synced 2026-04-27 14:30:34 +00:00
moved Schmidl & Cox correlator to own header
This commit is contained in:
Ahmet Inan
parent
2ec2af1ec9
commit
d5a0b5c2f2
2 changed files with 130 additions and 124 deletions
125
decode.cc
125
decode.cc
|
|
@ -9,10 +9,10 @@ Copyright 2021 Ahmet Inan <inan@aicodix.de>
|
|||
#include <cstdint>
|
||||
#include <cmath>
|
||||
namespace DSP { using std::abs; using std::min; using std::cos; using std::sin; }
|
||||
#include "schmidl_cox.hh"
|
||||
#include "bip_buffer.hh"
|
||||
#include "theil_sen.hh"
|
||||
#include "xorshift.hh"
|
||||
#include "trigger.hh"
|
||||
#include "complex.hh"
|
||||
#include "permute.hh"
|
||||
#include "decibel.hh"
|
||||
|
|
@ -21,7 +21,6 @@ namespace DSP { using std::abs; using std::min; using std::cos; using std::sin;
|
|||
#include "phasor.hh"
|
||||
#include "bitman.hh"
|
||||
#include "delay.hh"
|
||||
#include "sma.hh"
|
||||
#include "wav.hh"
|
||||
#include "pcm.hh"
|
||||
#include "fft.hh"
|
||||
|
|
@ -33,128 +32,6 @@ namespace DSP { using std::abs; using std::min; using std::cos; using std::sin;
|
|||
#include "polar_tables.hh"
|
||||
#include "polar_parity_aided.hh"
|
||||
|
||||
template <typename value, typename cmplx, int search_pos, int symbol_len, int guard_len>
|
||||
struct SchmidlCox
|
||||
{
|
||||
typedef DSP::Const<value> Const;
|
||||
static const int match_len = guard_len | 1;
|
||||
static const int match_del = (match_len - 1) / 2;
|
||||
DSP::FastFourierTransform<symbol_len, cmplx, -1> fwd;
|
||||
DSP::FastFourierTransform<symbol_len, cmplx, 1> bwd;
|
||||
DSP::SMA4<cmplx, value, symbol_len, false> cor;
|
||||
DSP::SMA4<value, value, 2*symbol_len, false> pwr;
|
||||
DSP::SMA4<value, value, match_len, false> match;
|
||||
DSP::Delay<value, match_del> align;
|
||||
DSP::SchmittTrigger<value> threshold;
|
||||
DSP::FallingEdgeTrigger falling;
|
||||
cmplx tmp0[symbol_len], tmp1[symbol_len];
|
||||
cmplx kern[symbol_len];
|
||||
cmplx cmplx_shift = 0;
|
||||
value timing_max = 0;
|
||||
value phase_max = 0;
|
||||
int index_max = 0;
|
||||
|
||||
static int bin(int carrier)
|
||||
{
|
||||
return (carrier + symbol_len) % symbol_len;
|
||||
}
|
||||
static cmplx demod_or_erase(cmplx curr, cmplx prev, value pwr)
|
||||
{
|
||||
if (!(norm(curr) > pwr))
|
||||
return 0;
|
||||
if (!(norm(prev) > pwr))
|
||||
return 0;
|
||||
cmplx cons = curr / prev;
|
||||
if (!(norm(cons) <= 4))
|
||||
return 0;
|
||||
return cons;
|
||||
}
|
||||
public:
|
||||
int symbol_pos = 0;
|
||||
value cfo_rad = 0;
|
||||
value frac_cfo = 0;
|
||||
|
||||
SchmidlCox(const cmplx *sequence) : threshold(value(0.17*match_len), value(0.19*match_len))
|
||||
{
|
||||
fwd(kern, sequence);
|
||||
for (int i = 0; i < symbol_len; ++i)
|
||||
kern[i] = conj(kern[i]) / value(symbol_len);
|
||||
}
|
||||
bool operator()(const cmplx *samples)
|
||||
{
|
||||
cmplx P = cor(samples[search_pos+symbol_len] * conj(samples[search_pos+2*symbol_len]));
|
||||
value R = value(0.5) * pwr(norm(samples[search_pos+2*symbol_len]));
|
||||
value min_R = 0.00001 * symbol_len;
|
||||
R = std::max(R, min_R);
|
||||
value timing = match(norm(P) / (R * R));
|
||||
value phase = align(arg(P));
|
||||
|
||||
bool collect = threshold(timing);
|
||||
bool process = falling(collect);
|
||||
|
||||
if (!collect && !process)
|
||||
return false;
|
||||
|
||||
if (timing_max < timing) {
|
||||
timing_max = timing;
|
||||
phase_max = phase;
|
||||
index_max = match_del;
|
||||
} else if (index_max < symbol_len + guard_len + match_del) {
|
||||
++index_max;
|
||||
}
|
||||
|
||||
if (!process)
|
||||
return false;
|
||||
|
||||
frac_cfo = phase_max / value(symbol_len);
|
||||
|
||||
DSP::Phasor<cmplx> osc;
|
||||
osc.omega(frac_cfo);
|
||||
symbol_pos = search_pos - index_max;
|
||||
index_max = 0;
|
||||
timing_max = 0;
|
||||
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)
|
||||
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];
|
||||
bwd(tmp1, tmp0);
|
||||
|
||||
int shift = 0;
|
||||
value peak = 0;
|
||||
value next = 0;
|
||||
for (int i = 0; i < symbol_len; ++i) {
|
||||
value power = norm(tmp1[i]);
|
||||
if (power > peak) {
|
||||
next = peak;
|
||||
peak = power;
|
||||
shift = i;
|
||||
} else if (power > next) {
|
||||
next = power;
|
||||
}
|
||||
}
|
||||
if (peak <= next * 4)
|
||||
return false;
|
||||
|
||||
int pos_err = std::nearbyint(arg(tmp1[shift]) * symbol_len / Const::TwoPi());
|
||||
if (abs(pos_err) > guard_len / 2)
|
||||
return false;
|
||||
symbol_pos -= pos_err;
|
||||
|
||||
cfo_rad = shift * (Const::TwoPi() / symbol_len) - frac_cfo;
|
||||
if (cfo_rad >= Const::Pi())
|
||||
cfo_rad -= Const::TwoPi();
|
||||
return true;
|
||||
}
|
||||
};
|
||||
|
||||
void base37_decoder(char *str, long long int val, int len)
|
||||
{
|
||||
for (int i = len-1; i >= 0; --i, val /= 37)
|
||||
|
|
|
|||
129
schmidl_cox.hh
Normal file
129
schmidl_cox.hh
Normal file
|
|
@ -0,0 +1,129 @@
|
|||
/*
|
||||
Schmidl & Cox correlator
|
||||
|
||||
Copyright 2021 Ahmet Inan <inan@aicodix.de>
|
||||
*/
|
||||
|
||||
#pragma once
|
||||
|
||||
#include "fft.hh"
|
||||
#include "sma.hh"
|
||||
#include "phasor.hh"
|
||||
#include "trigger.hh"
|
||||
|
||||
template<typename value, typename cmplx, int search_pos, int symbol_len, int guard_len>
|
||||
class SchmidlCox {
|
||||
typedef DSP::Const<value> Const;
|
||||
static const int match_len = guard_len | 1;
|
||||
static const int match_del = (match_len - 1) / 2;
|
||||
DSP::FastFourierTransform<symbol_len, cmplx, -1> fwd;
|
||||
DSP::FastFourierTransform<symbol_len, cmplx, 1> bwd;
|
||||
DSP::SMA4<cmplx, value, symbol_len, false> cor;
|
||||
DSP::SMA4<value, value, 2 * symbol_len, false> pwr;
|
||||
DSP::SMA4<value, value, match_len, false> match;
|
||||
DSP::Delay<value, match_del> align;
|
||||
DSP::SchmittTrigger<value> threshold;
|
||||
DSP::FallingEdgeTrigger falling;
|
||||
cmplx tmp0[symbol_len], tmp1[symbol_len];
|
||||
cmplx kern[symbol_len];
|
||||
value timing_max = 0;
|
||||
value phase_max = 0;
|
||||
int index_max = 0;
|
||||
|
||||
static int bin(int carrier) {
|
||||
return (carrier + symbol_len) % symbol_len;
|
||||
}
|
||||
|
||||
static cmplx demod_or_erase(cmplx curr, cmplx prev, value pwr) {
|
||||
if (norm(curr) > pwr && norm(prev) > pwr) {
|
||||
cmplx cons = curr / prev;
|
||||
if (norm(cons) < value(4))
|
||||
return cons;
|
||||
}
|
||||
return 0;
|
||||
}
|
||||
|
||||
public:
|
||||
int symbol_pos = 0;
|
||||
value cfo_rad = 0;
|
||||
value frac_cfo = 0;
|
||||
|
||||
SchmidlCox(const cmplx *sequence) : threshold(value(0.17 * match_len), value(0.19 * match_len)) {
|
||||
fwd(kern, sequence);
|
||||
for (int i = 0; i < symbol_len; ++i)
|
||||
kern[i] = conj(kern[i]) / value(symbol_len);
|
||||
}
|
||||
|
||||
bool operator()(const cmplx *samples) {
|
||||
cmplx P = cor(samples[search_pos + symbol_len] * conj(samples[search_pos + 2 * symbol_len]));
|
||||
value R = value(0.5) * pwr(norm(samples[search_pos + 2 * symbol_len]));
|
||||
value min_R = 0.00001 * symbol_len;
|
||||
R = std::max(R, min_R);
|
||||
value timing = match(norm(P) / (R * R));
|
||||
value phase = align(arg(P));
|
||||
|
||||
bool collect = threshold(timing);
|
||||
bool process = falling(collect);
|
||||
|
||||
if (!collect && !process)
|
||||
return false;
|
||||
|
||||
if (timing_max < timing) {
|
||||
timing_max = timing;
|
||||
phase_max = phase;
|
||||
index_max = match_del;
|
||||
} else if (index_max < symbol_len + guard_len + match_del) {
|
||||
++index_max;
|
||||
}
|
||||
|
||||
if (!process)
|
||||
return false;
|
||||
|
||||
frac_cfo = phase_max / value(symbol_len);
|
||||
|
||||
DSP::Phasor<cmplx> osc;
|
||||
osc.omega(frac_cfo);
|
||||
symbol_pos = search_pos - index_max;
|
||||
index_max = 0;
|
||||
timing_max = 0;
|
||||
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)
|
||||
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];
|
||||
bwd(tmp1, tmp0);
|
||||
|
||||
int shift = 0;
|
||||
value peak = 0;
|
||||
value next = 0;
|
||||
for (int i = 0; i < symbol_len; ++i) {
|
||||
value power = norm(tmp1[i]);
|
||||
if (power > peak) {
|
||||
next = peak;
|
||||
peak = power;
|
||||
shift = i;
|
||||
} else if (power > next) {
|
||||
next = power;
|
||||
}
|
||||
}
|
||||
if (peak <= next * 4)
|
||||
return false;
|
||||
|
||||
int pos_err = std::nearbyint(arg(tmp1[shift]) * symbol_len / Const::TwoPi());
|
||||
if (abs(pos_err) > guard_len / 2)
|
||||
return false;
|
||||
symbol_pos -= pos_err;
|
||||
|
||||
cfo_rad = shift * (Const::TwoPi() / symbol_len) - frac_cfo;
|
||||
if (cfo_rad >= Const::Pi())
|
||||
cfo_rad -= Const::TwoPi();
|
||||
return true;
|
||||
}
|
||||
};
|
||||
Loading…
Add table
Add a link
Reference in a new issue