Piotr Krysik | d890cd3 | 2017-09-19 07:52:34 +0200 | [diff] [blame] | 1 | #!/usr/bin/env python |
| 2 | # -*- coding: utf-8 -*- |
| 3 | # @file |
| 4 | # @author Piotr Krysik <ptrkrysik@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 | from math import floor, ceil |
| 24 | from random import uniform |
| 25 | |
| 26 | __hyper_frame = 26*51*2048 |
| 27 | __symb_rate = 13.0e6/48.0 |
| 28 | __ts_period = 156.25/__symb_rate |
| 29 | __frame_period = 8*__ts_period |
| 30 | |
| 31 | #The functions below are crucial part of synchronization between |
| 32 | #transmitter and receiver. |
| 33 | |
| 34 | #fnmod_delta computes difference between two frame numbers modulo |
| 35 | #__hyper_frame. The result is correct if difference between the frame |
| 36 | #numbers is not bigger than __hyper_frame/2. |
| 37 | def fnmod_delta(fn1, fn2): |
| 38 | h2 = __hyper_frame/2 |
| 39 | delta = (fn1%__hyper_frame)-(fn2%__hyper_frame) |
| 40 | |
| 41 | if delta >= h2: |
| 42 | delta = delta - __hyper_frame |
| 43 | elif delta < -h2: |
| 44 | delta = delta + __hyper_frame |
| 45 | |
| 46 | return delta |
| 47 | |
| 48 | #fn_time_delta computes difference between reference frame number and a second frame number. It also computes timestamp of the second frame number. The full list of parameters is following: |
| 49 | #* fn_ref - reference frame number modulo __hyper_frame |
| 50 | #* time_ref - precise timestamp of the first sample in the frame fn_ref |
| 51 | #* fn_x - second frame number modulo __hyper_frame, |
| 52 | #* time_hint - coarse time for fn_x that is used as a hint to avoid ambiguities caused by modulo operation applied to frame numbers. The correct are values from range <time2_precise-__hiperframe/2, time2_precise+__hiperframe/2> (where time2_precise is exact time of the first sample in frame fn_x) |
| 53 | #* ts_num - number of timeslot in the frame |
| 54 | |
| 55 | def fn_time_delta(fn_ref, time_ref, fn_x, time_hint=None, ts_num=None): |
| 56 | if time_hint is None: |
| 57 | time_hint = time_ref |
| 58 | |
| 59 | if ts_num is None: |
| 60 | ts_num = 0 |
| 61 | |
| 62 | time_diff = time_hint-time_ref |
| 63 | frames_diff = int(round(time_diff/__frame_period)) |
| 64 | fn_ref = (fn_ref + frames_diff) |
| 65 | fn_delta = fnmod_delta(fn_x,fn_ref)+frames_diff |
| 66 | time2_precise = fn_delta*__frame_period+time_ref+ts_num*__ts_period |
| 67 | |
| 68 | return fn_delta, time2_precise |
| 69 | |
| 70 | |
| 71 | if __name__ == "__main__": |
| 72 | fn1 = 10000 |
| 73 | time1 = 10 |
| 74 | for fn2 in xrange(__hyper_frame/2+fn1-10,__hyper_frame/2*10+fn1+10,10): |
| 75 | time2 = time1 + (fn2-fn1)*__frame_period |
| 76 | error = uniform(-6200,6200) |
| 77 | time2_err = time2+error |
| 78 | fn_delta, time2_precise = fn_time_delta(fn1, time1, fn2, time2_err) |
| 79 | if fn_delta != fn2-fn1: |
| 80 | print "dupa:", fn2, error#, 'fn_delta:'+str(fn_delta), time2, error, frames_diff_h4, (time2-time1)/(__hyper_frame*__frame_period), time_diff_h4_prev, time_diff |
| 81 | time_diff = time2 - time2_precise |
| 82 | if time_diff > 0.1: |
| 83 | print "dupa" |
| 84 | |