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use long preamble for channel estimation and add lms equalizer

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Bastian Bloessl
2015-04-17 10:23:25 +02:00
parent 5dd30e5e84
commit 48950a502b
9 changed files with 364 additions and 60 deletions
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lib/equalizer/base.h
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/*
* Copyright (C) 2015 Bastian Bloessl <bloessl@ccs-labs.org>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef INCLUDED_IEEE802_11_EQUALIZER_BASE_H
#define INCLUDED_IEEE802_11_EQUALIZER_BASE_H
#include <gnuradio/gr_complex.h>
namespace gr {
namespace ieee802_11 {
namespace equalizer {
class base {
public:
virtual ~base() {};
virtual void equalize(const gr_complex *in, gr_complex *out, int n) = 0;
};
} /* namespace channel_estimation */
} /* namespace ieee802_11 */
} /* namespace gr */
#endif /* INCLUDED_IEEE802_11_EQUALIZER_BASE_H */
lib/equalizer/linear_comb.cc
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/*
* Copyright (C) 2015 Bastian Bloessl <bloessl@ccs-labs.org>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "linear_comb.h"
using namespace gr::ieee802_11::equalizer;
void linear_comb::equalize(const gr_complex *in, gr_complex *out, int n) {
if(n < 2)
return;
double avg_mag = (abs(in[11]) + abs(in[25]) + abs(in[39]) + abs(in[53])) / 4;
gr_complex p = POLARITY[(n - 2) % 127 ];
double p1 = arg( p * in[11]);
double p2 = arg( p * in[25] * conj(p * in[11])) + p1;
double p3 = arg( p * in[39] * conj(p * in[25])) + p2;
double p4 = arg(-p * in[53] * conj(p * in[39])) + p3;
double my = (p1 + p2 + p3 + p4) / 4;
double mx = (11.0 + 25 + 39 + 53) / 4;
double var = (((11.0 * 11.0) + (25.0 * 25.0) + (39.0 * 39.0) + (53.0 * 53.0)) / 4) - (mx * mx);
double cov = (( (p1 * 11) + (p2 * 25) + (p3 * 39) + (p4 * 53) ) / 4) - (mx * my);
double beta = cov / var;
double alpha = my - beta * mx;
int c = 0;
for(int n = 0; n < 64; n++) {
if( (n == 11) || (n == 25) || (n == 32) || (n == 39) || (n == 53) || (n < 6) || ( n > 58)) {
continue;
} else {
out[c] = in[n] * exp(gr_complex(0, -n * beta - alpha)) * gr_complex(1 / avg_mag, 0);
c++;
}
}
}
const gr_complex linear_comb::POLARITY[127] = {
1, 1, 1, 1,-1,-1,-1, 1,-1,-1,-1,-1, 1, 1,-1, 1,
-1,-1, 1, 1,-1, 1, 1,-1, 1, 1, 1, 1, 1, 1,-1, 1,
1, 1,-1, 1, 1,-1,-1, 1, 1, 1,-1, 1,-1,-1,-1, 1,
-1, 1,-1,-1, 1,-1,-1, 1, 1, 1, 1, 1,-1,-1, 1, 1,
-1,-1, 1,-1, 1,-1, 1, 1,-1,-1,-1, 1, 1,-1,-1,-1,
-1, 1,-1,-1, 1,-1, 1, 1, 1, 1,-1, 1,-1, 1,-1, 1,
-1,-1,-1,-1,-1, 1,-1, 1, 1,-1, 1,-1, 1, 1, 1,-1,
-1, 1,-1,-1,-1, 1, 1, 1,-1,-1,-1,-1,-1,-1,-1 };
lib/equalizer/linear_comb.h
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/*
* Copyright (C) 2015 Bastian Bloessl <bloessl@ccs-labs.org>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef INCLUDED_IEEE802_11_EQUALIZER_LINEAR_COMB_H
#define INCLUDED_IEEE802_11_EQUALIZER_LINEAR_COMB_H
#include "base.h"
namespace gr {
namespace ieee802_11 {
namespace equalizer {
class linear_comb: public base {
public:
virtual void equalize(const gr_complex *in, gr_complex *out, int n);
private:
static const gr_complex POLARITY[127];
};
} /* namespace channel_estimation */
} /* namespace ieee802_11 */
} /* namespace gr */
#endif /* INCLUDED_IEEE802_11_EQUALIZER_LINEAR_COMB_H */
lib/equalizer/lms.cc
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/*
* Copyright (C) 2015 Bastian Bloessl <bloessl@ccs-labs.org>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "lms.h"
#include <cstring>
#include <iostream>
using namespace gr::ieee802_11::equalizer;
void lms::equalize(const gr_complex *in, gr_complex *out, int n) {
static float freq_offset = 0;
static float freq_sum = 0;
static float alpha = 0.9;
if(n == 0) {
std::memcpy(carrier, in, 64 * sizeof(gr_complex));
} else if(n == 1) {
gr_complex sum =
(carrier[11] * conj(in[11])) +
(carrier[25] * conj(in[25])) +
(carrier[39] * conj(in[39])) +
(carrier[53] * conj(in[53]));
freq_offset = arg(sum);
freq_sum = 0;
for(int i = 0; i < 64; i++) {
carrier[i] += in[i];
carrier[i] *= ref[i] * gr_complex(0.5, 0);
}
} else {
gr_complex p = POLARITY[(n - 2) % 127];
gr_complex sum =
(carrier[11] * conj(in[11]) * p) +
(carrier[25] * conj(in[25]) * p) +
(carrier[39] * conj(in[39]) * p) +
(carrier[53] * conj(in[53]) * -p);
freq_offset = (1 - alpha) * freq_offset + alpha * arg(sum);
freq_sum += freq_offset;
//std::cout << "lms: symbol " << n
// << " p1 " << abs(carrier[11] * conj(in[11]) * p)
// << " p2 " << abs(carrier[25] * conj(in[25]) * p)
// << " p3 " << abs(carrier[39] * conj(in[39]) * p)
// << " p4 " << abs(carrier[53] * conj(in[53]) * -p)
// << std::endl;
//std::cout << "lms: symbol " << n
// << " p1 " << arg(carrier[11] * conj(in[11]) * p)
// << " p2 " << arg(carrier[25] * conj(in[25]) * p)
// << " p3 " << arg(carrier[39] * conj(in[39]) * p)
// << " p4 " << arg(carrier[53] * conj(in[53]) * -p)
// << std::endl;
carrier[11] = in[11] * p;
carrier[25] = in[25] * p;
carrier[39] = in[39] * p;
carrier[53] = in[53] * -p;
int c = 0;
for(int i = 0; i < 64; i++) {
if( (i == 11) || (i == 25) || (i == 32) || (i == 39) || (i == 53) || (i < 6) || ( i > 58)) {
continue;
} else {
out[c] = in[i] / carrier[i] * exp(gr_complex(0, freq_sum));
c++;
}
}
}
}
const gr_complex lms::ref[] = {
0, 0, 0, 0, 0, 0, 1, 1, -1, -1,
1, 1, -1, 1, -1, 1, 1, 1, 1, 1,
1, -1, -1, 1, 1, -1, 1, -1, 1, 1,
1, 1, 0, 1, -1, -1, 1, 1, -1, 1,
-1, 1, -1, -1, -1, -1, -1, 1, 1, -1,
-1, 1, -1, 1, -1, 1, 1, 1, 1, 0,
0, 0, 0, 0
};
const gr_complex lms::POLARITY[127] = {
1, 1, 1, 1,-1,-1,-1, 1,-1,-1,-1,-1, 1, 1,-1, 1,
-1,-1, 1, 1,-1, 1, 1,-1, 1, 1, 1, 1, 1, 1,-1, 1,
1, 1,-1, 1, 1,-1,-1, 1, 1, 1,-1, 1,-1,-1,-1, 1,
-1, 1,-1,-1, 1,-1,-1, 1, 1, 1, 1, 1,-1,-1, 1, 1,
-1,-1, 1,-1, 1,-1, 1, 1,-1,-1,-1, 1, 1,-1,-1,-1,
-1, 1,-1,-1, 1,-1, 1, 1, 1, 1,-1, 1,-1, 1,-1, 1,
-1,-1,-1,-1,-1, 1,-1, 1, 1,-1, 1,-1, 1, 1, 1,-1,
-1, 1,-1,-1,-1, 1, 1, 1,-1,-1,-1,-1,-1,-1,-1 };
lib/equalizer/lms.h
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/*
* Copyright (C) 2015 Bastian Bloessl <bloessl@ccs-labs.org>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef INCLUDED_IEEE802_11_EQUALIZER_LMS_H
#define INCLUDED_IEEE802_11_EQUALIZER_LMS_H
#include "base.h"
#include <vector>
namespace gr {
namespace ieee802_11 {
namespace equalizer {
class lms: public base {
public:
virtual void equalize(const gr_complex *in, gr_complex *out, int n);
private:
gr_complex carrier[64];
static const gr_complex ref[64];
static const gr_complex POLARITY[127];
};
} /* namespace channel_estimation */
} /* namespace ieee802_11 */
} /* namespace gr */
#endif /* INCLUDED_IEEE802_11_EQUALIZER_LMS_H */