digital: moving mpsk_receiver from gnuradio-core to gr-digital. Added QA code for it.

1 files changed, 322 insertions, 0 deletions

diff --git a/gr-digital/lib/digital_mpsk_receiver_cc.cc b/gr-digital/lib/digital_mpsk_receiver_cc.cc
new file mode 100644
index 000000000..3b2ea9840
--- /dev/null
+++ b/gr-digital/lib/digital_mpsk_receiver_cc.cc
@@ -0,0 +1,322 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2005,2006,2007,2010,2011 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.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <gr_io_signature.h>
+#include <gr_prefs.h>
+#include <digital_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
+
+digital_mpsk_receiver_cc_sptr 
+digital_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 gnuradio::get_initial_sptr(new digital_mpsk_receiver_cc (M, theta, 
+							    alpha, beta,
+							    fmin, fmax,
+							    mu, gain_mu, 
+							    omega, gain_omega, omega_rel));
+}
+
+digital_mpsk_receiver_cc::digital_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 = &digital_mpsk_receiver_cc::phase_error_detector_bpsk; //bpsk;
+    d_decision = &digital_mpsk_receiver_cc::decision_bpsk;
+    break;
+
+  case 4: // optimized algorithms for QPSK
+    d_phase_error_detector = &digital_mpsk_receiver_cc::phase_error_detector_qpsk; //qpsk;
+    d_decision = &digital_mpsk_receiver_cc::decision_qpsk;
+    break;
+
+  default: // generic algorithms for any M (power of 2?) but not pretty
+    d_phase_error_detector = &digital_mpsk_receiver_cc::phase_error_detector_generic;
+    d_decision = &digital_mpsk_receiver_cc::decision_generic;
+    break;
+  }
+}
+
+digital_mpsk_receiver_cc::~digital_mpsk_receiver_cc ()
+{
+  delete d_interp;
+}
+
+void
+digital_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
+digital_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
+digital_mpsk_receiver_cc::phase_error_detector_bpsk(gr_complex sample) const
+{
+  return -(sample.real()*sample.imag());
+}
+
+float digital_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
+digital_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
+digital_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
+digital_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
+digital_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
+digital_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
+digital_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
+digital_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);
+    
+  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
+digital_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;
+}