diff options
Diffstat (limited to 'gr-digital/lib/mpsk_snr_est.cc')
| -rw-r--r-- | gr-digital/lib/mpsk_snr_est.cc | 84 |
1 files changed, 55 insertions, 29 deletions
diff --git a/gr-digital/lib/mpsk_snr_est.cc b/gr-digital/lib/mpsk_snr_est.cc index 6edb0274f5..4e7825b894 100644 --- a/gr-digital/lib/mpsk_snr_est.cc +++ b/gr-digital/lib/mpsk_snr_est.cc @@ -1,19 +1,19 @@ /* -*- 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, @@ -33,6 +33,8 @@ namespace gr { mpsk_snr_est::mpsk_snr_est(double alpha) { + d_signal = 0; + d_noise = 0; set_alpha(alpha); } @@ -65,6 +67,18 @@ namespace gr { throw std::runtime_error("mpsk_snr_est: Unimplemented"); } + double + mpsk_snr_est::signal() + { + return 10.0*log10(d_signal); + } + + double + mpsk_snr_est::noise() + { + return 10.0*log10(d_noise); + } + /*****************************************************************/ @@ -74,18 +88,27 @@ namespace gr { { d_y1 = 0; d_y2 = 0; + d_counter = 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; + int i = 0; + if(d_counter == 0) { + d_y1 = abs(input[0]); + d_y2 = 0; + d_counter++; + i++; + } - double y2 = real(input[i]*input[i]); - d_y2 = d_alpha*y2 + d_beta*d_y2; + for(; i < noutput_items; i++) { + double x = abs(input[i]); + double m = d_y1 + (x - d_y1)/d_counter; + d_y2 = d_y2 + (x - d_y1)*(x - m); + d_y1 = m; + d_counter++; } return noutput_items; } @@ -93,9 +116,10 @@ namespace gr { 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); + d_signal = d_y1; + d_noise = 2 * d_y2 / (d_counter - 1); + + return 10.0*log10(d_signal/d_noise); } @@ -107,7 +131,7 @@ namespace gr { { d_y1 = 0; d_y2 = 0; - d_y3 = 0; + d_counter = 1; } int @@ -118,16 +142,15 @@ namespace gr { double y1 = abs(input[i]); d_y1 = d_alpha*y1 + d_beta*d_y1; - double y2 = real(input[i]*input[i]); + 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; + double d = abs(input[i]) - d_y1; + double d_i = d / (i+1); + d_y3 = (d*d_i*i)*d_i*(i-1) - 3.0*d_i*d_y2; } return noutput_items; } @@ -136,9 +159,11 @@ namespace gr { 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)); + d_signal = d_y1*d_y1; + double x = d_signal - d_y2; + d_noise = 2*(x + y3*d_signal); + + return 10.0*log10(d_signal/d_noise); } @@ -170,8 +195,9 @@ namespace gr { 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))); + d_signal = sqrt(2*y1_2 - d_y2); + d_noise = d_y1 - sqrt(2*y1_2 - d_y2); + return 10.0*log10(d_signal / d_noise); } @@ -206,12 +232,12 @@ namespace gr { { double M2 = d_y1; double M4 = d_y2; - double s = M2*(d_kw - 2) + + d_signal = 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); + d_noise = M2 - d_signal; + + return 10.0*log10(d_signal / d_noise); } @@ -234,7 +260,7 @@ namespace gr { double x1 = abs(input[i]); 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; } @@ -245,7 +271,7 @@ namespace gr { mpsk_snr_est_svr::snr() { double x = d_y1 / (d_y2 - d_y1); - return 10.0*log10(2.*((x-1) + sqrt(x*(x-1)))); + return 10.0*log10(x - 1 + sqrt(x*(x-1))); } } /* namespace digital */ |