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/* -*- 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;
/*! \brief update the system gains from the loop bandwidth and damping factor
*
* This function updates the system gains based on the loop
* bandwidth and damping factor of the system.
* These two factors can be set separately through their own
* set functions.
*/
void update_gains();
friend digital_constellation_receiver_cb_sptr
digital_make_constellation_receiver_cb (digital_constellation_sptr constell,
float loop_bw, float fmin, float fmax);
};
#endif
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