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Diffstat (limited to 'gr-digital/lib/mpsk_snr_est.cc')
| -rw-r--r-- | gr-digital/lib/mpsk_snr_est.cc | 252 |
1 files changed, 252 insertions, 0 deletions
diff --git a/gr-digital/lib/mpsk_snr_est.cc b/gr-digital/lib/mpsk_snr_est.cc new file mode 100644 index 0000000000..1457a1a918 --- /dev/null +++ b/gr-digital/lib/mpsk_snr_est.cc @@ -0,0 +1,252 @@ +/* -*- c++ -*- */ +/* + * Copyright 2011,2012 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. + */ + +#ifdef HAVE_CONFIG_H +#include <config.h> +#endif + +#include <digital/mpsk_snr_est.h> +#include <stdexcept> +#include <cstdio> + +namespace gr { + namespace digital { + + mpsk_snr_est::mpsk_snr_est(double alpha) + { + set_alpha(alpha); + } + + mpsk_snr_est::~mpsk_snr_est() + {} + + void + mpsk_snr_est::set_alpha(double alpha) + { + d_alpha = alpha; + d_beta = 1.0-alpha; + } + + double + mpsk_snr_est::alpha() const + { + return d_alpha; + } + + int + mpsk_snr_est::update(int noutput_items, + const gr_complex *input) + { + throw std::runtime_error("mpsk_snr_est: Unimplemented"); + } + + double + mpsk_snr_est::snr() + { + throw std::runtime_error("mpsk_snr_est: Unimplemented"); + } + + + /*****************************************************************/ + + + mpsk_snr_est_simple::mpsk_snr_est_simple(double alpha) : + mpsk_snr_est(alpha) + { + d_y1 = 0; + d_y2 = 0; + } + + int + mpsk_snr_est_simple::update(int noutput_items, + const gr_complex *input) + { + for(int i = 0; i < noutput_items; i++) { + double y1 = abs(input[i]); + d_y1 = d_alpha*y1 + d_beta*d_y1; + + double y2 = real(input[i]*input[i]); + d_y2 = d_alpha*y2 + d_beta*d_y2; + } + return noutput_items; + } + + double + mpsk_snr_est_simple::snr() + { + double y1_2 = d_y1*d_y1; + double y3 = y1_2 - d_y2 + 1e-20; + return 10.0*log10(y1_2/y3); + } + + + /*****************************************************************/ + + + mpsk_snr_est_skew::mpsk_snr_est_skew(double alpha) : + mpsk_snr_est(alpha) + { + d_y1 = 0; + d_y2 = 0; + d_y3 = 0; + } + + int + mpsk_snr_est_skew::update(int noutput_items, + const gr_complex *input) + { + for(int i = 0; i < noutput_items; i++) { + double y1 = abs(input[i]); + d_y1 = d_alpha*y1 + d_beta*d_y1; + + double y2 = real(input[i]*input[i]); + d_y2 = d_alpha*y2 + d_beta*d_y2; + + // online algorithm for calculating skewness + // See: + // http://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Higher-order_statistics + double d = abs(input[i]) - d_y1; + double d_i = d / (i+1); + double y3 = (d*d_i*i)*d_i*(i-1) - 3.0*d_i*d_y2; + d_y3 = d_alpha*y3 + d_beta*d_y3; + } + return noutput_items; + } + + double + mpsk_snr_est_skew::snr() + { + double y3 = d_y3*d_y3 / (d_y2*d_y2*d_y2); + double y1_2 = d_y1*d_y1; + double x = y1_2 - d_y2; + return 10.0*log10(y1_2 / (x + y3*y1_2)); + } + + + /*****************************************************************/ + + + mpsk_snr_est_m2m4::mpsk_snr_est_m2m4(double alpha) : + mpsk_snr_est(alpha) + { + d_y1 = 0; + d_y2 = 0; + } + + int + mpsk_snr_est_m2m4::update(int noutput_items, + const gr_complex *input) + { + for(int i = 0; i < noutput_items; i++) { + double y1 = abs(input[i])*abs(input[i]); + d_y1 = d_alpha*y1 + d_beta*d_y1; + + double y2 = abs(input[i])*abs(input[i])*abs(input[i])*abs(input[i]); + d_y2 = d_alpha*y2 + d_beta*d_y2; + } + return noutput_items; + } + + double + mpsk_snr_est_m2m4::snr() + { + double y1_2 = d_y1*d_y1; + return 10.0*log10(2.0*sqrt(2*y1_2 - d_y2) / + (d_y1 - sqrt(2*y1_2 - d_y2))); + } + + + /*****************************************************************/ + + + snr_est_m2m4::snr_est_m2m4(double alpha, double ka, double kw) : + mpsk_snr_est(alpha) + { + d_y1 = 0; + d_y2 = 0; + d_ka = ka; + d_kw = kw; + } + + int + snr_est_m2m4::update(int noutput_items, + const gr_complex *input) + { + for(int i = 0; i < noutput_items; i++) { + double y1 = abs(input[i])*abs(input[i]); + d_y1 = d_alpha*y1 + d_beta*d_y1; + + double y2 = abs(input[i])*abs(input[i])*abs(input[i])*abs(input[i]); + d_y2 = d_alpha*y2 + d_beta*d_y2; + } + return noutput_items; + } + + double + snr_est_m2m4::snr() + { + double M2 = d_y1; + double M4 = d_y2; + double s = M2*(d_kw - 2) + + sqrt((4.0-d_ka*d_kw)*M2*M2 + M4*(d_ka+d_kw-4.0)) / + (d_ka + d_kw - 4.0); + double n = M2 - s; + + return 10.0*log10(s / n); + } + + + /*****************************************************************/ + + + mpsk_snr_est_svr::mpsk_snr_est_svr(double alpha) : + mpsk_snr_est(alpha) + { + d_y1 = 0; + d_y2 = 0; + } + + int + mpsk_snr_est_svr::update(int noutput_items, + const gr_complex *input) + { + for(int i = 0; i < noutput_items; i++) { + double x = abs(input[i]); + double x1 = abs(input[i-1]); + double y1 = (x*x)*(x1*x1); + d_y1 = d_alpha*y1 + d_beta*d_y1; + + double y2 = x*x*x*x; + d_y2 = d_alpha*y2 + d_beta*d_y2; + } + return noutput_items; + } + + double + mpsk_snr_est_svr::snr() + { + double x = d_y1 / (d_y2 - d_y1); + return 10.0*log10(2.*((x-1) + sqrt(x*(x-1)))); + } + + } /* namespace digital */ +} /* namespace gr */ |