Add code for C/A signal generation for glonass

src/algorithms/libs/CMakeLists.txt

@@ -23,6 +23,7 @@ set(GNSS_SPLIBS_SOURCES
     gnss_sdr_valve.cc
     gnss_signal_processing.cc
     gps_sdr_signal_processing.cc
+    glonass_l1_signal_processing.cc
     pass_through.cc
     galileo_e5_signal_processing.cc
     complex_byte_to_float_x2.cc

src/algorithms/libs/glonass_l1_signal_processing.cc

@@ -0,0 +1,131 @@
+/*!
+ * \file glonass_l1_signal_processing.cc
+ * \brief This class implements various functions for GLONASS L1 CA signals
+ * \author Javier Arribas, 2011. jarribas(at)cttc.es
+ *
+ * Detailed description of the file here if needed.
+ *
+ * -------------------------------------------------------------------------
+ *
+ * Copyright (C) 2010-2015  (see AUTHORS file for a list of contributors)
+ *
+ * GNSS-SDR is a software defined Global Navigation
+ *          Satellite Systems receiver
+ *
+ * This file is part of GNSS-SDR.
+ *
+ * GNSS-SDR 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 of the License, or
+ * (at your option) any later version.
+ *
+ * GNSS-SDR 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 GNSS-SDR. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * -------------------------------------------------------------------------
+ */
+
+#include "glonass_l1_signal_processing.h"
+
+auto auxCeil = [](float x){ return static_cast<int>(static_cast<long>((x)+1)); };
+
+void glonass_l1_ca_code_gen_complex(std::complex<float>* _dest/*, signed int _prn, unsigned int _chip_shift*/)
+{
+    const unsigned int _code_length = 511;
+    bool G1[_code_length];
+    bool G1_register[9];
+    bool feedback1;
+    bool aux;
+    unsigned int lcv, lcv2;
+
+    for(lcv = 0; lcv < 9; lcv++)
+        {
+            G1_register[lcv] = 1;
+        }
+
+    /* Generate G1 Register */
+    for(lcv = 0; lcv < _code_length; lcv++)
+        {
+            G1[lcv] = G1_register[2];
+
+            feedback1 = G1_register[4]^G1_register[0];
+
+            for(lcv2 = 0; lcv2 < 8; lcv2++)
+                {
+                    G1_register[lcv2] = G1_register[lcv2 + 1];
+                }
+
+            G1_register[8] = feedback1;
+        }
+
+    /* Generate PRN from G1 Register */
+    for(lcv = 0; lcv < _code_length; lcv++)
+        {
+            aux = G1[lcv];
+            if(aux == true)
+                {
+                    _dest[lcv] = std::complex<float>(1, 0);
+                }
+            else
+                {
+                    _dest[lcv] = std::complex<float>(-1, 0);
+                }
+        }
+}
+
+
+/*
+ *  Generates complex GLONASS L1 C/A code for the desired SV ID and sampled to specific sampling frequency
+ */
+void glonass_l1_ca_code_gen_complex_sampled(std::complex<float>* _dest, unsigned int _prn, signed int _fs, unsigned int _chip_shift)
+{
+    // This function is based on the GNU software GPS for MATLAB in the Kay Borre book
+    std::complex<float> _code[511];
+    signed int _samplesPerCode, _codeValueIndex;
+    float _ts;
+    float _tc;
+    float aux;
+    const signed int _codeFreqBasis = 511000; //Hz
+    const signed int _codeLength = 511;
+
+    //--- Find number of samples per spreading code ----------------------------
+    _samplesPerCode = static_cast<signed int>(static_cast<double>(_fs) / static_cast<double>(_codeFreqBasis / _codeLength));
+
+    //--- Find time constants --------------------------------------------------
+    _ts = 1.0 / static_cast<float>(_fs);   // Sampling period in sec
+    _tc = 1.0 / static_cast<float>(_codeFreqBasis);  // C/A chip period in sec
+    glonass_l1_ca_code_gen_complex(_code); //generate C/A code 1 sample per chip
+
+    for (signed int i = 0; i < _samplesPerCode; i++)
+        {
+            //=== Digitizing =======================================================
+
+            //--- Make index array to read C/A code values -------------------------
+            // The length of the index array depends on the sampling frequency -
+            // number of samples per millisecond (because one C/A code period is one
+            // millisecond).
+
+            // _codeValueIndex = ceil((_ts * ((float)i + 1)) / _tc) - 1;
+            aux = (_ts * (i + 1)) / _tc;   
+            _codeValueIndex = auxCeil( aux ) - 1;
+
+            //--- Make the digitized version of the C/A code -----------------------
+            // The "upsampled" code is made by selecting values form the CA code
+            // chip array (caCode) for the time instances of each sample.
+            if (i == _samplesPerCode - 1)
+                {
+                    //--- Correct the last index (due to number rounding issues) -----------
+                    _dest[i] = _code[_codeLength - 1];
+
+                }
+            else
+                {
+                    _dest[i] = _code[_codeValueIndex]; //repeat the chip -> upsample
+                }
+        }
+}

src/algorithms/libs/glonass_l1_signal_processing.h

@@ -0,0 +1,47 @@
+/*!
+ * \file glonass_l1_signal_processing.h
+ * \brief This class implements various functions for GLONASS L1 CA signals
+ * \author Gabriel Araujo, 2017. gabriel.araujo(at)ieee.org
+ *
+ * Detailed description of the file here if needed.
+ *
+ * -------------------------------------------------------------------------
+ *
+ * Copyright (C) 2010-2017  (see AUTHORS file for a list of contributors)
+ *
+ * GNSS-SDR is a software defined Global Navigation
+ *          Satellite Systems receiver
+ *
+ * This file is part of GNSS-SDR.
+ *
+ * GNSS-SDR 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 of the License, or
+ * (at your option) any later version.
+ *
+ * GNSS-SDR 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 GNSS-SDR. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * -------------------------------------------------------------------------
+ */
+
+#ifndef GNSS_SDR_GPS_SDR_SIGNAL_PROCESSING_H_
+#define GNSS_SDR_GPS_SDR_SIGNAL_PROCESSING_H_
+
+#include <complex>
+
+//!Generates complex GLONASS L1 C/A code for the desired SV ID and code shift, and sampled to specific sampling frequency
+void glonass_l1_ca_code_gen_complex(std::complex<float>* _dest/*, signed int _prn, unsigned int _chip_shift*/);
+
+//! Generates N complex GLONASS L1 C/A codes for the desired SV ID and code shift
+void glonass_l1_ca_code_gen_complex_sampled(std::complex<float>* _dest, unsigned int _prn, signed int _fs, unsigned int _chip_shift, unsigned int _ncodes);
+
+//! Generates complex GLONASS L1 C/A code for the desired SV ID and code shift
+void glonass_l1_ca_code_gen_complex_sampled(std::complex<float>* _dest, unsigned int _prn, signed int _fs, unsigned int _chip_shift);
+
+#endif /* GNSS_SDR_GPS_SDR_SIGNAL_PROCESSING_H_ */