mirror of https://github.com/gnss-sdr/gnss-sdr
317 lines
9.6 KiB
C++
317 lines
9.6 KiB
C++
/*!
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* \file gps_l5_signal.cc
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* \brief This class implements signal generators for the GPS L5 signals
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* \author Javier Arribas, 2017. jarribas(at)cttc.es
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*
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* Detailed description of the file here if needed.
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*
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* -------------------------------------------------------------------------
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*
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* Copyright (C) 2010-2017 (see AUTHORS file for a list of contributors)
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*
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* GNSS-SDR is a software defined Global Navigation
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* Satellite Systems receiver
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*
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* This file is part of GNSS-SDR.
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*
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* GNSS-SDR is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* GNSS-SDR is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with GNSS-SDR. If not, see <http://www.gnu.org/licenses/>.
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*
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* -------------------------------------------------------------------------
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*/
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#include "gps_l5_signal.h"
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#include "GPS_L5.h"
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#include <cinttypes>
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#include <cmath>
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#include <complex>
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#include <deque>
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std::deque<bool> l5i_xa_shift(std::deque<bool> xa)
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{
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if (xa == std::deque<bool>{1,1,1,1,1,1,1,1,1,1,1,0,1})
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{
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return std::deque<bool>{1,1,1,1,1,1,1,1,1,1,1,1,1};
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}
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else
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{
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std::deque<bool> out(xa.begin(), xa.end() - 1);
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out.push_front(xa[12] xor xa[11] xor xa[9] xor xa[8]);
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return out;
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}
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}
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std::deque<bool> l5q_xa_shift(std::deque<bool> xa)
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{
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if (xa == std::deque<bool>{1,1,1,1,1,1,1,1,1,1,1,0,1})
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{
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return std::deque<bool>{1,1,1,1,1,1,1,1,1,1,1,1,1};
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}
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else
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{
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std::deque<bool> out(xa.begin(), xa.end() - 1);
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out.push_front(xa[12] xor xa[11] xor xa[9] xor xa[8]);
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return out;
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}
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}
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std::deque<bool> l5i_xb_shift(std::deque<bool> xb)
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{
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std::deque<bool> out(xb.begin(), xb.end() - 1);
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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]);
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return out;
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}
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std::deque<bool> l5q_xb_shift(std::deque<bool> xb)
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{
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std::deque<bool> out(xb.begin(), xb.end()-1);
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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]);
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return out;
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}
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std::deque<bool> make_l5i_xa()
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{
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std::deque<bool> xa = {1,1,1,1,1,1,1,1,1,1,1,1,1};
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std::deque<bool> y(GPS_L5i_CODE_LENGTH_CHIPS, 0);
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for (int i = 0; i < GPS_L5i_CODE_LENGTH_CHIPS; i++)
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{
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y[i] = xa[12];
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xa = l5i_xa_shift(xa);
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}
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return y;
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}
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std::deque<bool> make_l5i_xb()
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{
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std::deque<bool> xb = {1,1,1,1,1,1,1,1,1,1,1,1,1};
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std::deque<bool> y(GPS_L5i_CODE_LENGTH_CHIPS,0);
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for (int i = 0; i < GPS_L5i_CODE_LENGTH_CHIPS; i++)
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{
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y[i] = xb[12];
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xb = l5i_xb_shift(xb);
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}
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return y;
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}
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std::deque<bool> make_l5q_xa()
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{
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std::deque<bool> xa = {1,1,1,1,1,1,1,1,1,1,1,1,1};
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std::deque<bool> y(GPS_L5q_CODE_LENGTH_CHIPS, 0);
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for (int i = 0; i < GPS_L5q_CODE_LENGTH_CHIPS; i++)
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{
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y[i] = xa[12];
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xa = l5q_xa_shift(xa);
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}
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return y;
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}
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std::deque<bool> make_l5q_xb()
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{
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std::deque<bool> xb = {1,1,1,1,1,1,1,1,1,1,1,1,1};
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std::deque<bool> y(GPS_L5q_CODE_LENGTH_CHIPS, 0);
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for (int i = 0; i < GPS_L5q_CODE_LENGTH_CHIPS; i++)
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{
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y[i] = xb[12];
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xb = l5q_xb_shift(xb);
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}
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return y;
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}
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void make_l5i(int32_t * _dest, int prn)
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{
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int xb_offset = GPS_L5i_INIT_REG[prn];
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std::deque<bool> xb = make_l5i_xb();
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std::deque<bool> xa = make_l5i_xa();
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std::deque<bool> xb_shift(GPS_L5i_CODE_LENGTH_CHIPS, 0);
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for (int n = 0; n < GPS_L5i_CODE_LENGTH_CHIPS; n++)
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{
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xb_shift[n] = xb[(xb_offset + n) % GPS_L5i_CODE_LENGTH_CHIPS];
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}
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std::deque<bool> out_code(GPS_L5i_CODE_LENGTH_CHIPS, 0);
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for (int n = 0; n < GPS_L5i_CODE_LENGTH_CHIPS; n++)
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{
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_dest[n] = xa[n] xor xb_shift[n];
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}
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}
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void make_l5q(int32_t * _dest, int prn)
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{
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int xb_offset = GPS_L5q_INIT_REG[prn];
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std::deque<bool> xb = make_l5q_xb();
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std::deque<bool> xa = make_l5q_xa();
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std::deque<bool> xb_shift(GPS_L5q_CODE_LENGTH_CHIPS, 0);
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for (int n = 0; n < GPS_L5q_CODE_LENGTH_CHIPS; n++)
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{
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xb_shift[n] = xb[(xb_offset + n) % GPS_L5q_CODE_LENGTH_CHIPS];
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}
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std::deque<bool> out_code(GPS_L5q_CODE_LENGTH_CHIPS, 0);
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for (int n = 0; n < GPS_L5q_CODE_LENGTH_CHIPS; n++)
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{
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_dest[n] = xa[n] xor xb_shift[n];
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}
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}
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void gps_l5i_code_gen_complex(std::complex<float>* _dest, unsigned int _prn)
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{
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int32_t* _code = new int32_t[GPS_L5i_CODE_LENGTH_CHIPS];
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if (_prn > 0 and _prn < 51)
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{
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make_l5i(_code, _prn - 1);
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}
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for (signed int i = 0; i < GPS_L5i_CODE_LENGTH_CHIPS; i++)
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{
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_dest[i] = std::complex<float>(1.0 - 2.0 * _code[i], 0.0);
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}
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delete[] _code;
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}
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/*
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* Generates complex GPS L5i code for the desired SV ID and sampled to specific sampling frequency
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*/
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void gps_l5i_code_gen_complex_sampled(std::complex<float>* _dest, unsigned int _prn, signed int _fs)
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{
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int32_t* _code = new int32_t[GPS_L5i_CODE_LENGTH_CHIPS];
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if (_prn > 0 and _prn < 51)
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{
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make_l5i(_code, _prn - 1);
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}
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signed int _samplesPerCode, _codeValueIndex;
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float _ts;
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float _tc;
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const signed int _codeLength = GPS_L5i_CODE_LENGTH_CHIPS;
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//--- Find number of samples per spreading code ----------------------------
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_samplesPerCode = static_cast<int>(static_cast<double>(_fs) / (static_cast<double>(GPS_L5i_CODE_RATE_HZ) / static_cast<double>(_codeLength)));
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//--- Find time constants --------------------------------------------------
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_ts = 1.0 / static_cast<float>(_fs); // Sampling period in sec
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_tc = 1.0 / static_cast<float>(GPS_L5i_CODE_RATE_HZ); // C/A chip period in sec
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//float aux;
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for (signed int i = 0; i < _samplesPerCode; i++)
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{
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//=== Digitizing =======================================================
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//--- Make index array to read L5 code values -------------------------
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//TODO: Check this formula! Seems to start with an extra sample
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_codeValueIndex = ceil((_ts * (static_cast<float>(i) + 1)) / _tc) - 1;
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//aux = (_ts * (i + 1)) / _tc;
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//_codeValueIndex = static_cast<int>(static_cast<long>(aux)) - 1;
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//--- Make the digitized version of the L2C code -----------------------
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if (i == _samplesPerCode - 1)
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{
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//--- Correct the last index (due to number rounding issues) -----------
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_dest[i] = std::complex<float>(1.0 - 2.0 * _code[_codeLength - 1], 0);
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}
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else
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{
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_dest[i] = std::complex<float>(1.0 - 2.0 * _code[_codeValueIndex], 0); //repeat the chip -> upsample
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}
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}
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delete[] _code;
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}
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void gps_l5q_code_gen_complex(std::complex<float>* _dest, unsigned int _prn)
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{
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int32_t* _code = new int32_t[GPS_L5q_CODE_LENGTH_CHIPS];
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if (_prn > 0 and _prn < 51)
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{
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make_l5q(_code, _prn - 1);
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}
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for (signed int i = 0; i < GPS_L5q_CODE_LENGTH_CHIPS; i++)
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{
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_dest[i] = std::complex<float>(1.0 - 2.0 * _code[i], 0.0);
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}
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delete[] _code;
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}
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/*
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* Generates complex GPS L5i code for the desired SV ID and sampled to specific sampling frequency
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*/
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void gps_l5q_code_gen_complex_sampled(std::complex<float>* _dest, unsigned int _prn, signed int _fs)
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{
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int32_t* _code = new int32_t[GPS_L5q_CODE_LENGTH_CHIPS];
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if (_prn > 0 and _prn < 51)
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{
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make_l5q(_code, _prn - 1);
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}
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signed int _samplesPerCode, _codeValueIndex;
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float _ts;
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float _tc;
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const signed int _codeLength = GPS_L5q_CODE_LENGTH_CHIPS;
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//--- Find number of samples per spreading code ----------------------------
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_samplesPerCode = static_cast<int>(static_cast<double>(_fs) / (static_cast<double>(GPS_L5q_CODE_RATE_HZ) / static_cast<double>(_codeLength)));
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//--- Find time constants --------------------------------------------------
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_ts = 1.0 / static_cast<float>(_fs); // Sampling period in sec
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_tc = 1.0 / static_cast<float>(GPS_L5q_CODE_RATE_HZ); // C/A chip period in sec
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//float aux;
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for (signed int i = 0; i < _samplesPerCode; i++)
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{
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//=== Digitizing =======================================================
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//--- Make index array to read L5 code values -------------------------
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//TODO: Check this formula! Seems to start with an extra sample
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_codeValueIndex = ceil((_ts * (static_cast<float>(i) + 1)) / _tc) - 1;
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//aux = (_ts * (i + 1)) / _tc;
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//_codeValueIndex = static_cast<int>(static_cast<long>(aux)) - 1;
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//--- Make the digitized version of the L2C code -----------------------
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if (i == _samplesPerCode - 1)
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{
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//--- Correct the last index (due to number rounding issues) -----------
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_dest[i] = std::complex<float>(1.0 - 2.0 * _code[_codeLength - 1], 0);
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}
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else
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{
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_dest[i] = std::complex<float>(1.0 - 2.0 * _code[_codeValueIndex], 0); //repeat the chip -> upsample
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}
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}
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delete[] _code;
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}
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