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/* -*- c++ -*- */
/*
* Copyright 2016,2018 Free Software Foundation, Inc.
*
* This file is part of GNU Radio
*
* GNU Radio 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, or (at your option)
* any later version.
*
* GNU Radio 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 GNU Radio; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
#include "flat_fader_impl.h"
#include <gnuradio/math.h>
namespace gr {
namespace channels {
flat_fader_impl::flat_fader_impl(uint32_t N, float fDTs, bool LOS, float K, uint32_t seed)
: rng_1(seed),
dist_1(-GR_M_PI, GR_M_PI),
rng_2(seed + 1),
dist_2(0, 1),
d_N(N),
d_fDTs(fDTs),
d_theta(dist_1(rng_1)),
d_theta_los(dist_1(rng_1)),
d_step(powf(0.00125 * fDTs, 1.1)), // max step size approximated from Table 2
d_m(0),
d_K(K),
d_LOS(LOS),
d_psi(d_N + 1, 0),
d_phi(d_N + 1, 0),
d_table(8 * 1024),
scale_sin(sqrtf(1.0 / d_N)),
scale_los(sqrtf(d_K) / sqrtf(d_K + 1)),
scale_nlos(1 / sqrtf(d_K + 1))
{
// generate initial phase values
for (int i = 0; i < d_N + 1; i++) {
d_psi[i] = dist_1(rng_1);
d_phi[i] = dist_1(rng_1);
}
}
#if FASTSINCOS == 1
#define _GRFASTSIN(x) gr::fxpt::sin(gr::fxpt::float_to_fixed(x))
#define _GRFASTCOS(x) gr::fxpt::cos(gr::fxpt::float_to_fixed(x))
#elif FASTSINCOS == 2
#define _GRFASTSIN(x) d_table.sin(x)
#define _GRFASTCOS(x) d_table.cos(x)
#else
#define _GRFASTSIN(x) sin(x)
#define _GRFASTCOS(x) cos(x)
#endif
void flat_fader_impl::next_samples(std::vector<gr_complex>& Hvec, int n_samples)
{
Hvec.resize(n_samples);
for (int i = 0; i < n_samples; i++) {
gr_complex H(0, 0);
for (int n = 1; n < d_N + 1; n++) {
float alpha_n = (2 * GR_M_PI * n - GR_M_PI + d_theta) / (4 * d_N);
d_psi[n] =
fmod(d_psi[n] + 2 * GR_M_PI * d_fDTs * _GRFASTCOS(alpha_n), 2 * GR_M_PI);
d_phi[n] =
fmod(d_phi[n] + 2 * GR_M_PI * d_fDTs * _GRFASTCOS(alpha_n), 2 * GR_M_PI);
float s_i = scale_sin * _GRFASTCOS(d_psi[n]);
float s_q = scale_sin * _GRFASTSIN(d_phi[n]);
H += gr_complex(s_i, s_q);
}
if (d_LOS) {
d_psi[0] = fmod(d_psi[0] + 2 * GR_M_PI * d_fDTs * _GRFASTCOS(d_theta_los),
2 * GR_M_PI);
float los_i = scale_los * _GRFASTCOS(d_psi[0]);
float los_q = scale_los * _GRFASTSIN(d_psi[0]);
H = H * scale_nlos + gr_complex(los_i, los_q);
}
update_theta();
Hvec[i] = H;
}
}
gr_complex flat_fader_impl::next_sample()
{
std::vector<gr_complex> v(1);
next_samples(v, 1);
return v[0];
}
void flat_fader_impl::update_theta()
{
d_theta += (d_step * dist_2(rng_2));
if (d_theta > GR_M_PI) {
d_theta = GR_M_PI;
d_step = -d_step;
} else if (d_theta < -GR_M_PI) {
d_theta = -GR_M_PI;
d_step = -d_step;
}
}
} /* namespace channels */
} /* namespace gr */
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