From 856eaf18810dfe56dd94832038778f68ad663993 Mon Sep 17 00:00:00 2001
From: Javier Arribas <javiarribas@gmail.com>
Date: Fri, 3 Aug 2018 12:05:40 +0200
Subject: [PATCH] Unified tracking algorithm improvement

---
 .../tracking/gnuradio_blocks/dll_pll_veml_tracking.cc  | 10 ++++++----
 src/algorithms/tracking/libs/dll_pll_conf.cc           |  1 +
 src/algorithms/tracking/libs/dll_pll_conf.h            |  1 +
 3 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/src/algorithms/tracking/gnuradio_blocks/dll_pll_veml_tracking.cc b/src/algorithms/tracking/gnuradio_blocks/dll_pll_veml_tracking.cc
index 3cb599866..4362e87b3 100755
--- a/src/algorithms/tracking/gnuradio_blocks/dll_pll_veml_tracking.cc
+++ b/src/algorithms/tracking/gnuradio_blocks/dll_pll_veml_tracking.cc
@@ -363,6 +363,7 @@ dll_pll_veml_tracking::dll_pll_veml_tracking(const Dll_Pll_Conf &conf_) : gr::bl
         }
 
     // --- Initializations ---
+    multicorrelator_cpu.set_fast_resampler(trk_parameters.use_fast_resampler);
     // Initial code frequency basis of NCO
     d_code_freq_chips = d_code_chip_rate;
     // Residual code phase (in chips)
@@ -742,8 +743,7 @@ void dll_pll_veml_tracking::run_dll_pll()
     d_carr_error_filt_hz = d_carrier_loop_filter.get_carrier_nco(d_carr_error_hz);
     // New carrier Doppler frequency estimation
     d_carrier_doppler_hz = d_acq_carrier_doppler_hz + d_carr_error_filt_hz;
-    // New code Doppler frequency estimation
-    d_code_freq_chips = (1.0 + (d_carrier_doppler_hz / d_signal_carrier_freq)) * d_code_chip_rate;
+
 
     // ################## DLL ##########################################################
     // DLL discriminator
@@ -757,6 +757,9 @@ void dll_pll_veml_tracking::run_dll_pll()
         }
     // Code discriminator filter
     d_code_error_filt_chips = d_code_loop_filter.get_code_nco(d_code_error_chips);  // [chips/second]
+
+    // New code Doppler frequency estimation
+    d_code_freq_chips = (1.0 + (d_carrier_doppler_hz / d_signal_carrier_freq)) * d_code_chip_rate - d_code_error_filt_chips;
 }
 
 
@@ -778,13 +781,12 @@ void dll_pll_veml_tracking::update_tracking_vars()
 {
     T_chip_seconds = 1.0 / d_code_freq_chips;
     T_prn_seconds = T_chip_seconds * static_cast<double>(d_code_length_chips);
-    double code_error_filt_secs = T_prn_seconds * d_code_error_filt_chips * T_chip_seconds;  //[seconds]
 
     // ################## CARRIER AND CODE NCO BUFFER ALIGNMENT #######################
     // keep alignment parameters for the next input buffer
     // Compute the next buffer length based in the new period of the PRN sequence and the code phase error estimation
     T_prn_samples = T_prn_seconds * trk_parameters.fs_in;
-    K_blk_samples = T_prn_samples + d_rem_code_phase_samples + code_error_filt_secs * trk_parameters.fs_in;
+    K_blk_samples = T_prn_samples + d_rem_code_phase_samples;
     //d_current_prn_length_samples = static_cast<int>(round(K_blk_samples));  // round to a discrete number of samples
     d_current_prn_length_samples = static_cast<int>(std::floor(K_blk_samples));  // round to a discrete number of samples
 
diff --git a/src/algorithms/tracking/libs/dll_pll_conf.cc b/src/algorithms/tracking/libs/dll_pll_conf.cc
index 89c6a1256..4cecdfcc5 100644
--- a/src/algorithms/tracking/libs/dll_pll_conf.cc
+++ b/src/algorithms/tracking/libs/dll_pll_conf.cc
@@ -36,6 +36,7 @@
 Dll_Pll_Conf::Dll_Pll_Conf()
 {
     /* DLL/PLL tracking configuration */
+    use_fast_resampler = true;
     fs_in = 0.0;
     vector_length = 0;
     dump = false;
diff --git a/src/algorithms/tracking/libs/dll_pll_conf.h b/src/algorithms/tracking/libs/dll_pll_conf.h
index 2cee8c405..a8f3ad10b 100644
--- a/src/algorithms/tracking/libs/dll_pll_conf.h
+++ b/src/algorithms/tracking/libs/dll_pll_conf.h
@@ -53,6 +53,7 @@ public:
     float early_late_space_narrow_chips;
     float very_early_late_space_narrow_chips;
     int extend_correlation_symbols;
+    bool use_fast_resampler;
     int cn0_samples;
     int carrier_lock_det_mav_samples;
     int cn0_min;