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Diffstat (limited to 'gr-digital/include/digital_constellation_receiver_cb.h')
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diff --git a/gr-digital/include/digital_constellation_receiver_cb.h b/gr-digital/include/digital_constellation_receiver_cb.h new file mode 100644 index 000000000..0ac80450f --- /dev/null +++ b/gr-digital/include/digital_constellation_receiver_cb.h @@ -0,0 +1,114 @@ +/* -*- 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. + */ + +#ifndef INCLUDED_DIGITAL_CONSTELLATION_RECEIVER_CB_H +#define INCLUDED_DIGITAL_CONSTELLATION_RECEIVER_CB_H + +#include <gr_block.h> +#include <digital_constellation.h> +#include <gri_control_loop.h> +#include <gr_complex.h> +#include <math.h> +#include <fstream> + +class digital_constellation_receiver_cb; +typedef boost::shared_ptr<digital_constellation_receiver_cb> digital_constellation_receiver_cb_sptr; + +// public constructor +digital_constellation_receiver_cb_sptr +digital_make_constellation_receiver_cb (digital_constellation_sptr constellation, + float loop_bw, float fmin, float fmax); + +/*! + * \brief This block takes care of receiving generic modulated signals through phase, frequency, and symbol + * synchronization. + * \ingroup sync_blk + * \ingroup demod_blk + * + * This block takes care of receiving generic modulated signals through phase, frequency, and symbol + * synchronization. It performs carrier frequency and phase locking as well as symbol timing recovery. + * + * The phase and frequency synchronization are based on a Costas loop that finds the error of the incoming + * signal point compared to its nearest constellation point. The frequency and phase of the NCO are + * updated according to this error. + * + * The symbol synchronization is done using a modified Mueller and Muller circuit from the paper: + * + * G. R. Danesfahani, T.G. Jeans, "Optimisation of modified Mueller and Muller + * algorithm," Electronics Letters, Vol. 31, no. 13, 22 June 1995, pp. 1032 - 1033. + * + * This circuit interpolates the downconverted sample (using the NCO developed by the Costas loop) + * every mu samples, then it finds the sampling error based on this and the past symbols and the decision + * made on the samples. Like the phase error detector, there are optimized decision algorithms for BPSK + * and QPKS, but 8PSK uses another brute force computation against all possible symbols. The modifications + * to the M&M used here reduce self-noise. + * + */ + +class digital_constellation_receiver_cb : public gr_block, public gri_control_loop +{ +public: + int general_work (int noutput_items, + gr_vector_int &ninput_items, + gr_vector_const_void_star &input_items, + gr_vector_void_star &output_items); + +protected: + + /*! + * \brief Constructor to synchronize incoming M-PSK symbols + * + * \param constellation constellation of points for generic modulation + * \param alpha gain parameter to adjust the phase in the Costas loop (~0.01) + * \param beta gain parameter to adjust the frequency in the Costas loop (~alpha^2/4) + * \param fmin minimum normalized frequency value the loop can achieve + * \param fmax maximum normalized frequency value the loop can achieve + * + * The constructor also chooses which phase detector and decision maker to use in the + * work loop based on the value of M. + */ + digital_constellation_receiver_cb (digital_constellation_sptr constellation, + float loop_bw, float fmin, float fmax); + + void phase_error_tracking(float phase_error); + +private: + unsigned int d_M; + + digital_constellation_sptr d_constellation; + unsigned int d_current_const_point; + + //! delay line length. + static const unsigned int DLLEN = 8; + + //! delay line plus some length for overflow protection + gr_complex d_dl[2*DLLEN] __attribute__ ((aligned(8))); + + //! index to delay line + unsigned int d_dl_idx; + + friend digital_constellation_receiver_cb_sptr + digital_make_constellation_receiver_cb (digital_constellation_sptr constell, + float loop_bw, float fmin, float fmax); +}; + +#endif |