diff options
Diffstat (limited to 'gr-digital/lib')
| -rw-r--r-- | gr-digital/lib/CMakeLists.txt | 1 | ||||
| -rw-r--r-- | gr-digital/lib/digital_mpsk_snr_est_cc.cc | 226 |
2 files changed, 227 insertions, 0 deletions
diff --git a/gr-digital/lib/CMakeLists.txt b/gr-digital/lib/CMakeLists.txt index b90757111..73ac5692f 100644 --- a/gr-digital/lib/CMakeLists.txt +++ b/gr-digital/lib/CMakeLists.txt @@ -46,6 +46,7 @@ list(APPEND gr_digital_sources digital_lms_dd_equalizer_cc.cc digital_kurtotic_equalizer_cc.cc digital_mpsk_receiver_cc.cc + digital_mpsk_snr_est_cc.cc digital_ofdm_cyclic_prefixer.cc digital_ofdm_frame_acquisition.cc digital_ofdm_frame_sink.cc diff --git a/gr-digital/lib/digital_mpsk_snr_est_cc.cc b/gr-digital/lib/digital_mpsk_snr_est_cc.cc new file mode 100644 index 000000000..7793eed1d --- /dev/null +++ b/gr-digital/lib/digital_mpsk_snr_est_cc.cc @@ -0,0 +1,226 @@ +/* -*- c++ -*- */ +/* + * Copyright 2011 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_cc.h> +#include <gr_io_signature.h> +#include <cstdio> + +digital_mpsk_snr_est_cc_sptr +digital_make_mpsk_snr_est_cc(snr_est_type_t type, + double alpha) +{ + return gnuradio::get_initial_sptr(new digital_mpsk_snr_est_cc(type, alpha)); +} + +digital_mpsk_snr_est_cc::digital_mpsk_snr_est_cc(snr_est_type_t type, + double alpha) + : gr_sync_block ("mpsk_snr_est_cc", + gr_make_io_signature(1, 1, sizeof(gr_complex)), + gr_make_io_signature(1, 1, sizeof(gr_complex))), + d_type(type), d_y1(0), d_y2(0), d_y3(0), d_y4(0) +{ + set_type(type); + set_alpha(alpha); + set_history(2); +} + +digital_mpsk_snr_est_cc::~digital_mpsk_snr_est_cc() +{ +} + +int +digital_mpsk_snr_est_cc::est_simple(int noutput_items, + gr_vector_const_void_star &input_items, + gr_vector_void_star &output_items) +{ + const gr_complex *in = (const gr_complex *) input_items[0]; + + for (int i = 0; i < noutput_items; i++){ + double y1 = abs(in[i]); + d_y1 = d_alpha*y1 + d_beta*d_y1; + + double y2 = real(in[i]*in[i]); + d_y2 = d_alpha*y2 + d_beta*d_y2; + } + return noutput_items; +} + +double +digital_mpsk_snr_est_cc::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); +} + +int +digital_mpsk_snr_est_cc::est_skew(int noutput_items, + gr_vector_const_void_star &input_items, + gr_vector_void_star &output_items) +{ + const gr_complex *in = (const gr_complex *) input_items[0]; + + for (int i = 0; i < noutput_items; i++){ + double y1 = abs(in[i]); + d_y1 = d_alpha*y1 + d_beta*d_y1; + + double y2 = real(in[i]*in[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(in[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 +digital_mpsk_snr_est_cc::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)); +} + +int +digital_mpsk_snr_est_cc::est_m2m4(int noutput_items, + gr_vector_const_void_star &input_items, + gr_vector_void_star &output_items) +{ + const gr_complex *in = (const gr_complex *) input_items[0]; + + for (int i = 0; i < noutput_items; i++){ + double y1 = abs(in[i])*abs(in[i]); + d_y1 = d_alpha*y1 + d_beta*d_y1; + + double y2 = abs(in[i])*abs(in[i])*abs(in[i])*abs(in[i]); + d_y2 = d_alpha*y2 + d_beta*d_y2; + } + return noutput_items; +} + +double +digital_mpsk_snr_est_cc::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))); +} + + +int +digital_mpsk_snr_est_cc::est_svn(int noutput_items, + gr_vector_const_void_star &input_items, + gr_vector_void_star &output_items) +{ + const gr_complex *in = (const gr_complex *) input_items[0]; + + for (int i = 0; i < noutput_items; i++){ + double x = abs(in[i]); + double x1 = abs(in[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 +digital_mpsk_snr_est_cc::est_svn_snr() +{ + double x = d_y1 / (d_y2 - d_y1); + return 10.0*log10(2.*((x-1) + sqrt(x*(x-1)))); +} + +int +digital_mpsk_snr_est_cc::work(int noutput_items, + gr_vector_const_void_star &input_items, + gr_vector_void_star &output_items) +{ + return (*this.*d_estimator)(noutput_items, input_items, output_items); +} + +double +digital_mpsk_snr_est_cc::snr() +{ + return (*this.*d_calculator)(); +} + +snr_est_type_t +digital_mpsk_snr_est_cc::type() const +{ + return d_type; +} + +double +digital_mpsk_snr_est_cc::alpha() const +{ + return d_alpha; +} + +void +digital_mpsk_snr_est_cc::set_type(snr_est_type_t t) +{ + d_type = t; + d_y1 = 0; + d_y2 = 0; + d_y3 = 0; + d_y4 = 0; + + switch (d_type) { + case(SNR_EST_SIMPLE): + d_estimator = &digital_mpsk_snr_est_cc::est_simple; + d_calculator = &digital_mpsk_snr_est_cc::est_simple_snr; + break; + case(SNR_EST_SKEW): + d_estimator = &digital_mpsk_snr_est_cc::est_skew; + d_calculator = &digital_mpsk_snr_est_cc::est_skew_snr; + break; + case(SNR_EST_M2M4): + d_estimator = &digital_mpsk_snr_est_cc::est_m2m4; + d_calculator = &digital_mpsk_snr_est_cc::est_m2m4_snr; + break; + case(SNR_EST_SVN): + d_estimator = &digital_mpsk_snr_est_cc::est_svn; + d_calculator = &digital_mpsk_snr_est_cc::est_svn_snr; + break; + default: + throw std::invalid_argument("digital_mpsk_snr_est_cc: unknown type specified.\n"); + } +} + +void +digital_mpsk_snr_est_cc::set_alpha(double alpha) +{ + d_alpha = alpha; + d_beta = 1.0-alpha; +} |