--- /dev/null
+/* -*- c++ -*- */
+/*
+ * Copyright 2004,2007 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_GR_MPSK_RECEIVER_CC_H
+#define INCLUDED_GR_MPSK_RECEIVER_CC_H
+
+#include <gr_block.h>
+#include <gr_complex.h>
+#include <fstream>
+
+class gri_mmse_fir_interpolator_cc;
+
+class gr_mpsk_receiver_cc;
+typedef boost::shared_ptr<gr_mpsk_receiver_cc> gr_mpsk_receiver_cc_sptr;
+
+// public constructor
+gr_mpsk_receiver_cc_sptr
+gr_make_mpsk_receiver_cc (unsigned int M, float theta,
+ float alpha, float beta,
+ 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 gr_mpsk_receiver_cc : public gr_block
+{
+ public:
+ ~gr_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; }
+
+
+
+ // Member function related to the phase/frequency tracking portion of the receiver
+ //! (CL) Returns the value for alpha (the phase gain term)
+ float alpha() const { return d_alpha; }
+
+ //! (CL) Returns the value of beta (the frequency gain term)
+ float beta() const { return d_beta; }
+
+ //! (CL) Returns the current value of the frequency of the NCO in the Costas loop
+ float freq() const { return d_freq; }
+
+ //! (CL) Returns the current value of the phase of the NCO in the Costal loop
+ float phase() const { return d_phase; }
+
+ //! (CL) Sets the value for alpha (the phase gain term)
+ void set_alpha(float alpha) { d_alpha = alpha; }
+
+ //! (CL) Setss the value of beta (the frequency gain term)
+ void set_beta(float beta) { d_beta = beta; }
+
+ //! (CL) Sets the current value of the frequency of the NCO in the Costas loop
+ void set_freq(float freq) { d_freq = freq; }
+
+ //! (CL) Setss the current value of the phase of the NCO in the Costal loop
+ void set_phase(float phase) { d_phase = phase; }
+
+
+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 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
+ * \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.
+ */
+ gr_mpsk_receiver_cc (unsigned int M, float theta,
+ float alpha, float beta,
+ 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;
+
+ // Members related to carrier and phase tracking
+ float d_alpha;
+ float d_beta;
+ float d_freq, d_max_freq, d_min_freq;
+ float d_phase;
+
+/*!
+ * \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 (gr_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 (gr_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_complex d_dl[2*DLLEN] __attribute__ ((aligned(8)));
+
+ //! index to delay line
+ unsigned int d_dl_idx;
+
+ friend gr_mpsk_receiver_cc_sptr
+ gr_make_mpsk_receiver_cc (unsigned int M, float theta,
+ float alpha, float beta,
+ float fmin, float fmax,
+ float mu, float gain_mu,
+ float omega, float gain_omega, float omega_rel);
+};
+
+#endif
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