| /* -*- c++ -*- */ |
| /* @file |
| * @author Piotr Krysik <ptrkrysik@gmail.com> |
| * @author Vadim Yanitskiy <axilirator@gmail.com> |
| * @section LICENSE |
| * |
| * Gr-gsm 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. |
| * |
| * Gr-gsm 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 gr-gsm; see the file COPYING. If not, write to |
| * the Free Software Foundation, Inc., 51 Franklin Street, |
| * Boston, MA 02110-1301, USA. |
| * |
| */ |
| |
| #include <grgsm/misc_utils/fn_time.h> |
| #include <grgsm/misc_utils/time_spec.h> |
| #include <math.h> |
| |
| #define GSM_HYPER_FRAME (26 * 51 * 2048) |
| #define GSM_SYM_RATE (13.0e6 / 48.0) |
| |
| #define GSM_TS_PERIOD (156.25 / GSM_SYM_RATE) |
| #define GSM_FN_PERIOD (8 * GSM_TS_PERIOD) |
| |
| namespace gr { |
| namespace gsm { |
| /** |
| * Computes difference between two frame numbers modulo |
| * GSM_HYPER_FRAME / 2. The result is correct if difference |
| * between the frame numbers is not bigger than GSM_HYPER_FRAME / 2. |
| * @param fn1 first frame number |
| * @param fn2 second frame number |
| * @return computed difference |
| */ |
| static int fnmod_delta(uint32_t fn1, uint32_t fn2) |
| { |
| int delta, h2; |
| |
| delta = (fn1 % GSM_HYPER_FRAME) - (fn2 % GSM_HYPER_FRAME); |
| |
| h2 = GSM_HYPER_FRAME / 2; |
| |
| if (delta >= h2) { |
| delta -= GSM_HYPER_FRAME; |
| } else if(delta < -h2) { |
| delta += GSM_HYPER_FRAME; |
| } |
| |
| return delta; |
| } |
| |
| static int fn_time_diff_delta(uint32_t fn, uint32_t fn_ref, |
| time_spec_t time_diff_hint) |
| { |
| int frames_diff, fn_delta; |
| frames_diff = int(round(time_diff_hint.get_real_secs() / GSM_FN_PERIOD)); |
| fn_delta = fnmod_delta(fn, fn_ref + frames_diff) + frames_diff; |
| |
| return fn_delta; |
| } |
| |
| /** |
| * Computes difference between reference frame number |
| * and a second frame number. |
| * @param fn_ref reference frame number modulo GSM_HYPER_FRAME |
| * @param fn second frame number modulo GSM_HYPER_FRAME |
| * @param time_ref precise timestamp of the first sample in the fn_ref |
| * @param time_hint coarse time for fn that is used as a hint to avoid |
| * ambiguities caused by modulo operation applied to |
| * frame numbers |
| * @return difference between fn_ref and fn |
| */ |
| time_format fn_time_delta_cpp(uint32_t fn_ref, time_format time_ref, uint32_t fn_x, |
| time_format time_hint, uint32_t ts_num, uint32_t ts_ref) |
| { |
| time_spec_t time_diff_hint = time_spec_t(time_hint.first, time_hint.second) - time_spec_t(time_ref.first, time_ref.second); |
| int fn_delta = fn_time_diff_delta(fn_x, fn_ref, time_diff_hint); |
| time_spec_t time_x_precise = fn_delta * GSM_FN_PERIOD + time_spec_t(time_ref.first, time_ref.second) + (static_cast<int>(ts_num) - static_cast<int>(ts_ref)) * GSM_TS_PERIOD; |
| |
| return time_format(time_x_precise.get_full_secs(), time_x_precise.get_frac_secs()); |
| } |
| |
| } /* namespace gsm */ |
| } /* namespace gr */ |
| |