/*! * \file gps_l5_signal.cc * \brief This class implements signal generators for the GPS L5 signals * \author Javier Arribas, 2017. jarribas(at)cttc.es * * Detailed description of the file here if needed. * * ------------------------------------------------------------------------- * * Copyright (C) 2010-2018 (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 . * * ------------------------------------------------------------------------- */ #include "gps_l5_signal.h" #include "GPS_L5.h" #include std::deque l5i_xa_shift(std::deque xa) // GPS-IS-705E Figure 3-4 pp. 15 { if (xa == std::deque{true, true, true, true, true, true, true, true, true, true, true, false, true}) { return std::deque{true, true, true, true, true, true, true, true, true, true, true, true, true}; } std::deque out(xa.begin(), xa.end() - 1); out.push_front(xa[12] xor xa[11] xor xa[9] xor xa[8]); return out; } std::deque l5q_xa_shift(std::deque xa) { if (xa == std::deque{true, true, true, true, true, true, true, true, true, true, true, false, true}) { return std::deque{true, true, true, true, true, true, true, true, true, true, true, true, true}; } std::deque out(xa.begin(), xa.end() - 1); out.push_front(xa[12] xor xa[11] xor xa[9] xor xa[8]); return out; } std::deque l5i_xb_shift(std::deque xb) // GPS-IS-705E Figure 3-5 pp. 16 { std::deque out(xb.begin(), xb.end() - 1); out.push_front(xb[12] xor xb[11] xor xb[7] xor xb[6] xor xb[5] xor xb[3] xor xb[2] xor xb[0]); return out; } std::deque l5q_xb_shift(std::deque xb) { std::deque out(xb.begin(), xb.end() - 1); out.push_front(xb[12] xor xb[11] xor xb[7] xor xb[6] xor xb[5] xor xb[3] xor xb[2] xor xb[0]); return out; } std::deque make_l5i_xa() { std::deque xa = {true, true, true, true, true, true, true, true, true, true, true, true, true}; std::deque y(GPS_L5I_CODE_LENGTH_CHIPS, false); for (int32_t i = 0; i < GPS_L5I_CODE_LENGTH_CHIPS; i++) { y[i] = xa[12]; xa = l5i_xa_shift(xa); } return y; } std::deque make_l5i_xb() { std::deque xb = {true, true, true, true, true, true, true, true, true, true, true, true, true}; std::deque y(GPS_L5I_CODE_LENGTH_CHIPS, false); for (int32_t i = 0; i < GPS_L5I_CODE_LENGTH_CHIPS; i++) { y[i] = xb[12]; xb = l5i_xb_shift(xb); } return y; } std::deque make_l5q_xa() { std::deque xa = {true, true, true, true, true, true, true, true, true, true, true, true, true}; std::deque y(GPS_L5Q_CODE_LENGTH_CHIPS, false); for (int32_t i = 0; i < GPS_L5Q_CODE_LENGTH_CHIPS; i++) { y[i] = xa[12]; xa = l5q_xa_shift(xa); } return y; } std::deque make_l5q_xb() { std::deque xb = {true, true, true, true, true, true, true, true, true, true, true, true, true}; std::deque y(GPS_L5Q_CODE_LENGTH_CHIPS, false); for (int32_t i = 0; i < GPS_L5Q_CODE_LENGTH_CHIPS; i++) { y[i] = xb[12]; xb = l5q_xb_shift(xb); } return y; } void make_l5i(gsl::span _dest, int32_t prn) { int32_t xb_offset = GPS_L5I_INIT_REG[prn]; std::deque xb = make_l5i_xb(); std::deque xa = make_l5i_xa(); std::deque xb_shift(GPS_L5I_CODE_LENGTH_CHIPS, false); for (int32_t n = 0; n < GPS_L5I_CODE_LENGTH_CHIPS; n++) { xb_shift[n] = xb[(xb_offset + n) % GPS_L5I_CODE_LENGTH_CHIPS]; } for (int32_t n = 0; n < GPS_L5I_CODE_LENGTH_CHIPS; n++) { _dest[n] = xa[n] xor xb_shift[n]; } } void make_l5q(gsl::span _dest, int32_t prn) { int32_t xb_offset = GPS_L5Q_INIT_REG[prn]; std::deque xb = make_l5q_xb(); std::deque xa = make_l5q_xa(); std::deque xb_shift(GPS_L5Q_CODE_LENGTH_CHIPS, false); for (int32_t n = 0; n < GPS_L5Q_CODE_LENGTH_CHIPS; n++) { xb_shift[n] = xb[(xb_offset + n) % GPS_L5Q_CODE_LENGTH_CHIPS]; } for (int32_t n = 0; n < GPS_L5Q_CODE_LENGTH_CHIPS; n++) { _dest[n] = xa[n] xor xb_shift[n]; } } void gps_l5i_code_gen_complex(gsl::span> _dest, uint32_t _prn) { std::unique_ptr _code{new int32_t[GPS_L5I_CODE_LENGTH_CHIPS]}; gsl::span _code_span(_code, GPS_L5I_CODE_LENGTH_CHIPS); if (_prn > 0 and _prn < 51) { make_l5i(_code_span, _prn - 1); } for (int32_t i = 0; i < GPS_L5I_CODE_LENGTH_CHIPS; i++) { _dest[i] = std::complex(1.0 - 2.0 * _code_span[i], 0.0); } } void gps_l5i_code_gen_float(gsl::span _dest, uint32_t _prn) { std::unique_ptr _code{new int32_t[GPS_L5I_CODE_LENGTH_CHIPS]}; gsl::span _code_span(_code, GPS_L5I_CODE_LENGTH_CHIPS); if (_prn > 0 and _prn < 51) { make_l5i(_code_span, _prn - 1); } for (int32_t i = 0; i < GPS_L5I_CODE_LENGTH_CHIPS; i++) { _dest[i] = 1.0 - 2.0 * static_cast(_code_span[i]); } } /* * Generates complex GPS L5i code for the desired SV ID and sampled to specific sampling frequency */ void gps_l5i_code_gen_complex_sampled(gsl::span> _dest, uint32_t _prn, int32_t _fs) { std::unique_ptr _code{new int32_t[GPS_L5I_CODE_LENGTH_CHIPS]}; gsl::span _code_span(_code, GPS_L5I_CODE_LENGTH_CHIPS); if (_prn > 0 and _prn < 51) { make_l5i(_code_span, _prn - 1); } int32_t _samplesPerCode, _codeValueIndex; float _ts; float _tc; const int32_t _codeLength = GPS_L5I_CODE_LENGTH_CHIPS; //--- Find number of samples per spreading code ---------------------------- _samplesPerCode = static_cast(static_cast(_fs) / (static_cast(GPS_L5I_CODE_RATE_HZ) / static_cast(_codeLength))); //--- Find time constants -------------------------------------------------- _ts = 1.0 / static_cast(_fs); // Sampling period in sec _tc = 1.0 / static_cast(GPS_L5I_CODE_RATE_HZ); // L5I primary chip period in sec for (int32_t i = 0; i < _samplesPerCode; i++) { //=== Digitizing ======================================================= //--- Make index array to read L5 code values ------------------------- _codeValueIndex = static_cast(std::ceil(_ts * static_cast(i + 1) / _tc)) - 1; //--- Make the digitized version of the L5I code ----------------------- if (i == _samplesPerCode - 1) { //--- Correct the last index (due to number rounding issues) ----------- _dest[i] = std::complex(1.0 - 2.0 * _code_span[_codeLength - 1], 0.0); } else { _dest[i] = std::complex(1.0 - 2.0 * _code_span[_codeValueIndex], 0.0); // repeat the chip -> upsample } } } void gps_l5q_code_gen_complex(gsl::span> _dest, uint32_t _prn) { std::unique_ptr _code{new int32_t[GPS_L5Q_CODE_LENGTH_CHIPS]}; gsl::span _code_span(_code, GPS_L5Q_CODE_LENGTH_CHIPS); if (_prn > 0 and _prn < 51) { make_l5q(_code_span, _prn - 1); } for (int32_t i = 0; i < GPS_L5Q_CODE_LENGTH_CHIPS; i++) { _dest[i] = std::complex(1.0 - 2.0 * _code_span[i], 0.0); } } void gps_l5q_code_gen_float(gsl::span _dest, uint32_t _prn) { std::unique_ptr _code{new int32_t[GPS_L5Q_CODE_LENGTH_CHIPS]}; gsl::span _code_span(_code, GPS_L5Q_CODE_LENGTH_CHIPS); if (_prn > 0 and _prn < 51) { make_l5q(_code_span, _prn - 1); } for (int32_t i = 0; i < GPS_L5Q_CODE_LENGTH_CHIPS; i++) { _dest[i] = 1.0 - 2.0 * static_cast(_code_span[i]); } } /* * Generates complex GPS L5Q code for the desired SV ID and sampled to specific sampling frequency */ void gps_l5q_code_gen_complex_sampled(gsl::span> _dest, uint32_t _prn, int32_t _fs) { std::unique_ptr _code{new int32_t[GPS_L5Q_CODE_LENGTH_CHIPS]}; gsl::span _code_span(_code, GPS_L5Q_CODE_LENGTH_CHIPS); if (_prn > 0 and _prn < 51) { make_l5q(_code_span, _prn - 1); } int32_t _samplesPerCode, _codeValueIndex; float _ts; float _tc; const int32_t _codeLength = GPS_L5Q_CODE_LENGTH_CHIPS; //--- Find number of samples per spreading code ---------------------------- _samplesPerCode = static_cast(static_cast(_fs) / (static_cast(GPS_L5Q_CODE_RATE_HZ) / static_cast(_codeLength))); //--- Find time constants -------------------------------------------------- _ts = 1.0 / static_cast(_fs); // Sampling period in sec _tc = 1.0 / static_cast(GPS_L5Q_CODE_RATE_HZ); // L5Q chip period in sec //float aux; for (int32_t i = 0; i < _samplesPerCode; i++) { //=== Digitizing ======================================================= //--- Make index array to read L5 code values ------------------------- _codeValueIndex = static_cast(std::ceil(_ts * static_cast(i + 1) / _tc)) - 1; //--- Make the digitized version of the L5Q code ----------------------- if (i == _samplesPerCode - 1) { //--- Correct the last index (due to number rounding issues) ----------- _dest[i] = std::complex(1.0 - 2.0 * _code_span[_codeLength - 1], 0); } else { _dest[i] = std::complex(1.0 - 2.0 * _code_span[_codeValueIndex], 0); // repeat the chip -> upsample } } }