--- /dev/null
+/* -*- c++ -*- */
+/*
+ * Copyright 2005,2006,2007 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.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <gr_io_signature.h>
+#include <gr_prefs.h>
+#include <gr_mpsk_receiver_cc.h>
+#include <stdexcept>
+#include <gr_math.h>
+#include <gr_expj.h>
+#include <gri_mmse_fir_interpolator_cc.h>
+
+
+#define M_TWOPI (2*M_PI)
+#define VERBOSE_MM 0 // Used for debugging symbol timing loop
+#define VERBOSE_COSTAS 0 // Used for debugging phase and frequency tracking
+
+// 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)
+{
+ return gr_mpsk_receiver_cc_sptr (new gr_mpsk_receiver_cc (M, theta,
+ alpha, beta,
+ fmin, fmax,
+ mu, gain_mu,
+ omega, gain_omega, omega_rel));
+}
+
+gr_mpsk_receiver_cc::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)
+ : gr_block ("mpsk_receiver_cc",
+ gr_make_io_signature (1, 1, sizeof (gr_complex)),
+ gr_make_io_signature (1, 1, sizeof (gr_complex))),
+ d_M(M), d_theta(theta),
+ d_alpha(alpha), d_beta(beta), d_freq(0), d_max_freq(fmax), d_min_freq(fmin), d_phase(0),
+ d_current_const_point(0),
+ d_mu(mu), d_gain_mu(gain_mu), d_gain_omega(gain_omega),
+ d_omega_rel(omega_rel), d_max_omega(0), d_min_omega(0),
+ d_p_2T(0), d_p_1T(0), d_p_0T(0), d_c_2T(0), d_c_1T(0), d_c_0T(0)
+{
+ d_interp = new gri_mmse_fir_interpolator_cc();
+ d_dl_idx = 0;
+
+ set_omega(omega);
+
+ if (omega <= 0.0)
+ throw std::out_of_range ("clock rate must be > 0");
+ if (gain_mu < 0 || gain_omega < 0)
+ throw std::out_of_range ("Gains must be non-negative");
+
+ assert(d_interp->ntaps() <= DLLEN);
+
+ // zero double length delay line.
+ for (unsigned int i = 0; i < 2 * DLLEN; i++)
+ d_dl[i] = gr_complex(0.0,0.0);
+
+ // build the constellation vector from M
+ make_constellation();
+
+ // Select a phase detector and a decision maker for the modulation order
+ switch(d_M) {
+ case 2: // optimized algorithms for BPSK
+ d_phase_error_detector = &gr_mpsk_receiver_cc::phase_error_detector_bpsk; //bpsk;
+ d_decision = &gr_mpsk_receiver_cc::decision_bpsk;
+ break;
+
+ case 4: // optimized algorithms for QPSK
+ d_phase_error_detector = &gr_mpsk_receiver_cc::phase_error_detector_qpsk; //qpsk;
+ d_decision = &gr_mpsk_receiver_cc::decision_qpsk;
+ break;
+
+ default: // generic algorithms for any M (power of 2?) but not pretty
+ d_phase_error_detector = &gr_mpsk_receiver_cc::phase_error_detector_generic;
+ d_decision = &gr_mpsk_receiver_cc::decision_generic;
+ break;
+ }
+}
+
+gr_mpsk_receiver_cc::~gr_mpsk_receiver_cc ()
+{
+ delete d_interp;
+}
+
+void
+gr_mpsk_receiver_cc::forecast(int noutput_items, gr_vector_int &ninput_items_required)
+{
+ unsigned ninputs = ninput_items_required.size();
+ for (unsigned i=0; i < ninputs; i++)
+ ninput_items_required[i] = (int) ceil((noutput_items * d_omega) + d_interp->ntaps());
+}
+
+// FIXME add these back in an test difference in performance
+float
+gr_mpsk_receiver_cc::phase_error_detector_qpsk(gr_complex sample) const
+{
+ float phase_error = 0;
+ if(fabsf(sample.real()) > fabsf(sample.imag())) {
+ if(sample.real() > 0)
+ phase_error = -sample.imag();
+ else
+ phase_error = sample.imag();
+ }
+ else {
+ if(sample.imag() > 0)
+ phase_error = sample.real();
+ else
+ phase_error = -sample.real();
+ }
+
+ return phase_error;
+}
+
+float
+gr_mpsk_receiver_cc::phase_error_detector_bpsk(gr_complex sample) const
+{
+ return -(sample.real()*sample.imag());
+}
+
+float gr_mpsk_receiver_cc::phase_error_detector_generic(gr_complex sample) const
+{
+ //return gr_fast_atan2f(sample*conj(d_constellation[d_current_const_point]));
+ return -arg(sample*conj(d_constellation[d_current_const_point]));
+}
+
+unsigned int
+gr_mpsk_receiver_cc::decision_bpsk(gr_complex sample) const
+{
+ return (gr_branchless_binary_slicer(sample.real()) ^ 1);
+ //return gr_binary_slicer(sample.real()) ^ 1;
+}
+
+unsigned int
+gr_mpsk_receiver_cc::decision_qpsk(gr_complex sample) const
+{
+ unsigned int index;
+
+ //index = gr_branchless_quad_0deg_slicer(sample);
+ index = gr_quad_0deg_slicer(sample);
+ return index;
+}
+
+unsigned int
+gr_mpsk_receiver_cc::decision_generic(gr_complex sample) const
+{
+ unsigned int min_m = 0;
+ float min_s = 65535;
+
+ // Develop all possible constellation points and find the one that minimizes
+ // the Euclidean distance (error) with the sample
+ for(unsigned int m=0; m < d_M; m++) {
+ gr_complex diff = norm(d_constellation[m] - sample);
+
+ if(fabs(diff.real()) < min_s) {
+ min_s = fabs(diff.real());
+ min_m = m;
+ }
+ }
+ // Return the index of the constellation point that minimizes the error
+ return min_m;
+}
+
+
+void
+gr_mpsk_receiver_cc::make_constellation()
+{
+ for(unsigned int m=0; m < d_M; m++) {
+ d_constellation.push_back(gr_expj((M_TWOPI/d_M)*m));
+ }
+}
+
+void
+gr_mpsk_receiver_cc::mm_sampler(const gr_complex symbol)
+{
+ gr_complex sample, nco;
+
+ d_mu--; // skip a number of symbols between sampling
+ d_phase += d_freq; // increment the phase based on the frequency of the rotation
+
+ // Keep phase clamped and not walk to infinity
+ while(d_phase > M_TWOPI)
+ d_phase -= M_TWOPI;
+ while(d_phase < -M_TWOPI)
+ d_phase += M_TWOPI;
+
+ nco = gr_expj(d_phase+d_theta); // get the NCO value for derotating the current sample
+ sample = nco*symbol; // get the downconverted symbol
+
+ // Fill up the delay line for the interpolator
+ d_dl[d_dl_idx] = sample;
+ d_dl[(d_dl_idx + DLLEN)] = sample; // put this in the second half of the buffer for overflows
+ d_dl_idx = (d_dl_idx+1) % DLLEN; // Keep the delay line index in bounds
+}
+
+void
+gr_mpsk_receiver_cc::mm_error_tracking(gr_complex sample)
+{
+ gr_complex u, x, y;
+ float mm_error = 0;
+
+ // Make sample timing corrections
+
+ // set the delayed samples
+ d_p_2T = d_p_1T;
+ d_p_1T = d_p_0T;
+ d_p_0T = sample;
+ d_c_2T = d_c_1T;
+ d_c_1T = d_c_0T;
+
+ d_current_const_point = (*this.*d_decision)(d_p_0T); // make a decision on the sample value
+ d_c_0T = d_constellation[d_current_const_point];
+
+ x = (d_c_0T - d_c_2T) * conj(d_p_1T);
+ y = (d_p_0T - d_p_2T) * conj(d_c_1T);
+ u = y - x;
+ mm_error = u.real(); // the error signal is in the real part
+ mm_error = gr_branchless_clip(mm_error, 1.0); // limit mm_val
+
+ d_omega = d_omega + d_gain_omega * mm_error; // update omega based on loop error
+ d_omega = d_omega_mid + gr_branchless_clip(d_omega-d_omega_mid, d_omega_rel); // make sure we don't walk away
+
+ d_mu += d_omega + d_gain_mu * mm_error; // update mu based on loop error
+
+#if VERBOSE_MM
+ printf("mm: mu: %f omega: %f mm_error: %f sample: %f+j%f constellation: %f+j%f\n",
+ d_mu, d_omega, mm_error, sample.real(), sample.imag(),
+ d_constellation[d_current_const_point].real(), d_constellation[d_current_const_point].imag());
+#endif
+}
+
+
+void
+gr_mpsk_receiver_cc::phase_error_tracking(gr_complex sample)
+{
+ float phase_error = 0;
+
+ // Make phase and frequency corrections based on sampled value
+ phase_error = (*this.*d_phase_error_detector)(sample);
+
+ phase_error = gr_branchless_clip(phase_error, 1.0);
+
+ d_freq += d_beta*phase_error; // adjust frequency based on error
+ d_phase += d_freq + d_alpha*phase_error; // adjust phase based on error
+
+ // Make sure we stay within +-2pi
+ while(d_phase > M_TWOPI)
+ d_phase -= M_TWOPI;
+ while(d_phase < -M_TWOPI)
+ d_phase += M_TWOPI;
+
+ // Limit the frequency range
+ d_freq = gr_branchless_clip(d_freq, d_max_freq);
+
+#if VERBOSE_COSTAS
+ printf("cl: phase_error: %f phase: %f freq: %f sample: %f+j%f constellation: %f+j%f\n",
+ phase_error, d_phase, d_freq, sample.real(), sample.imag(),
+ d_constellation[d_current_const_point].real(), d_constellation[d_current_const_point].imag());
+#endif
+}
+
+int
+gr_mpsk_receiver_cc::general_work (int noutput_items,
+ gr_vector_int &ninput_items,
+ gr_vector_const_void_star &input_items,
+ gr_vector_void_star &output_items)
+{
+ const gr_complex *in = (const gr_complex *) input_items[0];
+ gr_complex *out = (gr_complex *) output_items[0];
+
+ int i=0, o=0;
+
+ while((o < noutput_items) && (i < ninput_items[0])) {
+ while((d_mu > 1) && (i < ninput_items[0])) {
+ mm_sampler(in[i]); // puts symbols into a buffer and adjusts d_mu
+ i++;
+ }
+
+ if(i < ninput_items[0]) {
+ gr_complex interp_sample = d_interp->interpolate(&d_dl[d_dl_idx], d_mu);
+
+ mm_error_tracking(interp_sample); // corrects M&M sample time
+ phase_error_tracking(interp_sample); // corrects phase and frequency offsets
+
+ out[o++] = interp_sample;
+ }
+ }
+
+ #if 0
+ printf("ninput_items: %d noutput_items: %d consuming: %d returning: %d\n",
+ ninput_items[0], noutput_items, i, o);
+ #endif
+
+ consume_each(i);
+ return o;
+}
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