Piotr Krysik | 34ce7a0 | 2017-10-31 11:30:59 +0100 | [diff] [blame] | 1 | /* -*- c++ -*- */ |
| 2 | /* @file |
| 3 | * @author Piotr Krysik <ptrkrysik@gmail.com> |
| 4 | * @author Vadim Yanitskiy <axilirator@gmail.com> |
| 5 | * @section LICENSE |
| 6 | * |
| 7 | * Gr-gsm is free software; you can redistribute it and/or modify |
| 8 | * it under the terms of the GNU General Public License as published by |
| 9 | * the Free Software Foundation; either version 3, or (at your option) |
| 10 | * any later version. |
| 11 | * |
| 12 | * Gr-gsm is distributed in the hope that it will be useful, |
| 13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 15 | * GNU General Public License for more details. |
| 16 | * |
| 17 | * You should have received a copy of the GNU General Public License |
| 18 | * along with gr-gsm; see the file COPYING. If not, write to |
| 19 | * the Free Software Foundation, Inc., 51 Franklin Street, |
| 20 | * Boston, MA 02110-1301, USA. |
| 21 | * |
| 22 | */ |
| 23 | |
| 24 | #include <grgsm/misc_utils/fn_time.h> |
| 25 | #include <math.h> |
Piotr Krysik | 34ce7a0 | 2017-10-31 11:30:59 +0100 | [diff] [blame] | 26 | |
| 27 | #define GSM_HYPER_FRAME 26 * 51 * 2048 |
| 28 | #define GSM_SYM_RATE 13.0e6 / 48.0 |
| 29 | |
| 30 | #define GSM_TS_PERIOD 156.25 / GSM_SYM_RATE |
| 31 | #define GSM_FN_PERIOD 8 * GSM_TS_PERIOD |
| 32 | |
| 33 | namespace gr { |
| 34 | namespace gsm { |
Piotr Krysik | 34ce7a0 | 2017-10-31 11:30:59 +0100 | [diff] [blame] | 35 | /** |
| 36 | * Computes difference between two frame numbers modulo |
| 37 | * GSM_HYPER_FRAME / 2. The result is correct if difference |
| 38 | * between the frame numbers is not bigger than GSM_HYPER_FRAME / 2. |
| 39 | * @param fn1 first frame number |
| 40 | * @param fn2 second frame number |
| 41 | * @return computed difference |
| 42 | */ |
| 43 | static uint32_t fnmod_delta(uint32_t fn1, uint32_t fn2) |
| 44 | { |
| 45 | uint32_t delta, h2; |
| 46 | |
| 47 | delta = (fn1 % GSM_HYPER_FRAME) - (fn2 % GSM_HYPER_FRAME); |
| 48 | h2 = GSM_HYPER_FRAME / 2; |
| 49 | |
| 50 | if (delta >= h2) |
| 51 | delta -= GSM_HYPER_FRAME; |
| 52 | else |
| 53 | delta += GSM_HYPER_FRAME; |
| 54 | |
| 55 | return delta; |
| 56 | } |
| 57 | |
| 58 | static int fn_time_diff_delta(uint32_t fn, uint32_t fn_ref, |
| 59 | time_spec_t time_diff_hint) |
| 60 | { |
| 61 | int frames_diff, fn_delta; |
| 62 | |
| 63 | frames_diff = int(round(time_diff_hint.get_real_secs() / GSM_FN_PERIOD)); |
| 64 | fn_delta = fnmod_delta(fn, fn_ref + frames_diff) + frames_diff; |
| 65 | |
| 66 | return fn_delta; |
| 67 | } |
| 68 | |
| 69 | /** |
| 70 | * Computes difference between reference frame number |
| 71 | * and a second frame number. |
| 72 | * @param fn_ref reference frame number modulo GSM_HYPER_FRAME |
| 73 | * @param fn second frame number modulo GSM_HYPER_FRAME |
| 74 | * @param time_ref precise timestamp of the first sample in the fn_ref |
| 75 | * @param time_hint coarse time for fn that is used as a hint to avoid |
| 76 | * ambiguities caused by modulo operation applied to |
| 77 | * frame numbers |
| 78 | * @return difference between fn_ref and fn |
| 79 | */ |
Piotr Krysik | 1dd2afe | 2017-10-31 12:57:26 +0100 | [diff] [blame] | 80 | time_spec_t fn_time_delta2(uint32_t fn_ref, time_spec_t time_ref, uint32_t fn_x, |
Piotr Krysik | 34ce7a0 | 2017-10-31 11:30:59 +0100 | [diff] [blame] | 81 | time_spec_t time_hint, uint32_t ts_num, uint32_t ts_ref) |
| 82 | { |
| 83 | time_spec_t time_diff_hint = time_hint - time_ref; |
| 84 | uint32_t fn_delta = fn_time_diff_delta(fn_x,fn_ref, time_diff_hint); |
| 85 | time_spec_t time_x_precise = fn_delta * GSM_FN_PERIOD |
| 86 | + time_ref + (ts_num - ts_ref) * GSM_TS_PERIOD; |
| 87 | |
| 88 | return time_x_precise; |
| 89 | } |
| 90 | /* |
| 91 | def fn_time_delta(fn_ref, time_ref, fn_x, time_hint=None, ts_num=0, ts_ref=0): |
| 92 | if time_hint is None: |
| 93 | time_hint = time_ref |
| 94 | |
| 95 | time_diff_hint = time_hint-time_ref |
| 96 | fn_delta = fn_time_diff_delta(fn_x,fn_ref, time_diff_hint) |
| 97 | time_x_precise = fn_delta*__frame_period+time_ref+(ts_num-ts_ref)*__ts_period |
| 98 | |
| 99 | return fn_delta, time_x_precise |
| 100 | */ |
| 101 | } /* namespace gsm */ |
| 102 | } /* namespace gr */ |
| 103 | |