diff options
Diffstat (limited to 'gr-digital/include/digital_mpsk_receiver_cc.h')
| -rw-r--r-- | gr-digital/include/digital_mpsk_receiver_cc.h | 301 |
1 files changed, 301 insertions, 0 deletions
diff --git a/gr-digital/include/digital_mpsk_receiver_cc.h b/gr-digital/include/digital_mpsk_receiver_cc.h new file mode 100644 index 000000000..f8aa4e341 --- /dev/null +++ b/gr-digital/include/digital_mpsk_receiver_cc.h @@ -0,0 +1,301 @@ +/* -*- c++ -*- */ +/* + * Copyright 2004,2007,2011 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_MPSK_RECEIVER_CC_H +#define INCLUDED_DIGITAL_MPSK_RECEIVER_CC_H + +#include <gruel/attributes.h> +#include <gri_control_loop.h> +#include <gr_block.h> +#include <gr_complex.h> +#include <fstream> + +class gri_mmse_fir_interpolator_cc; + +class digital_mpsk_receiver_cc; +typedef boost::shared_ptr<digital_mpsk_receiver_cc> digital_mpsk_receiver_cc_sptr; + +// public constructor +digital_mpsk_receiver_cc_sptr +digital_make_mpsk_receiver_cc (unsigned int M, float theta, + float loop_bw, + float fmin, float fmax, + float mu, float gain_mu, + float omega, float gain_omega, float omega_rel); + +/*! + * \brief This block takes care of receiving M-PSK modulated signals + * through phase, frequency, and symbol synchronization. + * \ingroup sync_blk + * \ingroup demod_blk + * + * This block takes care of receiving M-PSK modulated signals through + * phase, frequency, and symbol synchronization. It performs carrier + * frequency and phase locking as well as symbol timing recovery. It + * works with (D)BPSK, (D)QPSK, and (D)8PSK as tested currently. It + * should also work for OQPSK and PI/4 DQPSK. + * + * 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. There are optimized phase error + * detectors for BPSK and QPSK, but 8PSK is done using a brute-force + * computation of the constellation points to find the minimum. + * + * 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_mpsk_receiver_cc : public gr_block, public gri_control_loop +{ + public: + ~digital_mpsk_receiver_cc (); + void forecast(int noutput_items, gr_vector_int &ninput_items_required); + int general_work (int noutput_items, + gr_vector_int &ninput_items, + gr_vector_const_void_star &input_items, + gr_vector_void_star &output_items); + + + // Member functions related to the symbol tracking portion of the receiver + //! (M&M) Returns current value of mu + float mu() const { return d_mu;} + + //! (M&M) Returns current value of omega + float omega() const { return d_omega;} + + //! (M&M) Returns mu gain factor + float gain_mu() const { return d_gain_mu;} + + //! (M&M) Returns omega gain factor + float gain_omega() const { return d_gain_omega;} + + //! (M&M) Sets value of mu + void set_mu (float mu) { d_mu = mu; } + + //! (M&M) Sets value of omega and its min and max values + void set_omega (float omega) { + d_omega = omega; + d_min_omega = omega*(1.0 - d_omega_rel); + d_max_omega = omega*(1.0 + d_omega_rel); + d_omega_mid = 0.5*(d_min_omega+d_max_omega); + } + + //! (M&M) Sets value for mu gain factor + void set_gain_mu (float gain_mu) { d_gain_mu = gain_mu; } + + //! (M&M) Sets value for omega gain factor + void set_gain_omega (float gain_omega) { d_gain_omega = gain_omega; } + +protected: + + /*! + * \brief Constructor to synchronize incoming M-PSK symbols + * + * \param M modulation order of the M-PSK modulation + * \param theta any constant phase rotation from the real axis of the constellation + * \param loop_bw Loop bandwidth to set gains of phase/freq tracking loop + * \param fmin minimum normalized frequency value the loop can achieve + * \param fmax maximum normalized frequency value the loop can achieve + * \param mu initial parameter for the interpolator [0,1] + * \param gain_mu gain parameter of the M&M error signal to adjust mu (~0.05) + * \param omega initial value for the number of symbols between samples (~number of samples/symbol) + * \param gain_omega gain parameter to adjust omega based on the error (~omega^2/4) + * \param omega_rel sets the maximum (omega*(1+omega_rel)) and minimum (omega*(1+omega_rel)) omega (~0.005) + * + * The constructor also chooses which phase detector and decision maker to use in the work loop based on the + * value of M. + */ + digital_mpsk_receiver_cc (unsigned int M, float theta, + float loop_bw, + float fmin, float fmax, + float mu, float gain_mu, + float omega, float gain_omega, float omega_rel); + + void make_constellation(); + void mm_sampler(const gr_complex symbol); + void mm_error_tracking(gr_complex sample); + void phase_error_tracking(gr_complex sample); + + + /*! + * \brief Phase error detector for MPSK modulations. + * + * \param sample the I&Q sample from which to determine the phase error + * + * This function determines the phase error for any MPSK signal by + * creating a set of PSK constellation points and doing a + * brute-force search to see which point minimizes the Euclidean + * distance. This point is then used to derotate the sample to the + * real-axis and a atan (using the fast approximation function) to + * determine the phase difference between the incoming sample and + * the real constellation point + * + * This should be cleaned up and made more efficient. + * + * \returns the approximated phase error. + */ + float phase_error_detector_generic(gr_complex sample) const; // generic for M but more costly + + /*! + * \brief Phase error detector for BPSK modulation. + * + * \param sample the I&Q sample from which to determine the phase error + * + * This function determines the phase error using a simple BPSK + * phase error detector by multiplying the real and imaginary (the + * error signal) components together. As the imaginary part goes to + * 0, so does this error. + * + * \returns the approximated phase error. + */ + float phase_error_detector_bpsk(gr_complex sample) const; // optimized for BPSK + + /*! + * \brief Phase error detector for QPSK modulation. + * + * \param sample the I&Q sample from which to determine the phase error + * + * This function determines the phase error using the limiter + * approach in a standard 4th order Costas loop + * + * \returns the approximated phase error. + */ + float phase_error_detector_qpsk(gr_complex sample) const; + + + + /*! + * \brief Decision maker for a generic MPSK constellation. + * + * \param sample the baseband I&Q sample from which to make the decision + * + * This decision maker is a generic implementation that does a + * brute-force search for the constellation point that minimizes the + * error between it and the incoming signal. + * + * \returns the index to d_constellation that minimizes the error/ + */ + unsigned int decision_generic(gr_complex sample) const; + + + /*! + * \brief Decision maker for BPSK constellation. + * + * \param sample the baseband I&Q sample from which to make the decision + * + * This decision maker is a simple slicer function that makes a + * decision on the symbol based on its placement on the real axis of + * greater than 0 or less than 0; the quadrature component is always + * 0. + * + * \returns the index to d_constellation that minimizes the error/ + */ + unsigned int decision_bpsk(gr_complex sample) const; + + + /*! + * \brief Decision maker for QPSK constellation. + * + * \param sample the baseband I&Q sample from which to make the decision + * + * This decision maker is a simple slicer function that makes a + * decision on the symbol based on its placement versus both axes + * and returns which quadrant the symbol is in. + * + * \returns the index to d_constellation that minimizes the error/ + */ + unsigned int decision_qpsk(gr_complex sample) const; + +private: + unsigned int d_M; + float d_theta; + + /*! + * \brief Decision maker function pointer + * + * \param sample the baseband I&Q sample from which to make the decision + * + * This is a function pointer that is set in the constructor to + * point to the proper decision function for the specified + * constellation order. + * + * \return index into d_constellation point that is the closest to the recieved sample + */ + unsigned int (digital_mpsk_receiver_cc::*d_decision)(gr_complex sample) const; // pointer to decision function + + + std::vector<gr_complex> d_constellation; + unsigned int d_current_const_point; + + // Members related to symbol timing + float d_mu, d_gain_mu; + float d_omega, d_gain_omega, d_omega_rel, d_max_omega, d_min_omega, d_omega_mid; + gr_complex d_p_2T, d_p_1T, d_p_0T; + gr_complex d_c_2T, d_c_1T, d_c_0T; + + /*! + * \brief Phase error detector function pointer + * + * \param sample the I&Q sample from which to determine the phase error + * + * This is a function pointer that is set in the constructor to + * point to the proper phase error detector function for the + * specified constellation order. + */ + float (digital_mpsk_receiver_cc::*d_phase_error_detector)(gr_complex sample) const; + + + //! get interpolated value + gri_mmse_fir_interpolator_cc *d_interp; + + //! delay line length. + static const unsigned int DLLEN = 8; + + //! delay line plus some length for overflow protection + __GR_ATTR_ALIGNED(8) gr_complex d_dl[2*DLLEN]; + + //! index to delay line + unsigned int d_dl_idx; + + friend digital_mpsk_receiver_cc_sptr + digital_make_mpsk_receiver_cc (unsigned int M, float theta, + float loop_bw, + float fmin, float fmax, + float mu, float gain_mu, + float omega, float gain_omega, float omega_rel); +}; + +#endif |