| #!/usr/bin/env python |
| # -*- coding: utf-8 -*- |
| # @file |
| # @author Piotr Krysik <ptrkrysik@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. |
| # |
| # |
| from math import floor, ceil |
| from random import uniform |
| from grgsm import fn_time_delta_cpp |
| |
| __hyper_frame = 26*51*2048 |
| __symb_rate = 13.0e6/48.0 |
| __ts_period = 156.25/__symb_rate |
| __frame_period = 8*__ts_period |
| |
| #The functions below are crucial part of synchronization between |
| #transmitter and receiver. |
| |
| #fnmod_delta computes difference between two frame numbers modulo |
| #__hyper_frame. The result is correct if difference between the frame |
| #numbers is not bigger than __hyper_frame/2. |
| def fnmod_delta(fn1, fn2): |
| h2 = __hyper_frame/2 |
| delta = (fn1%__hyper_frame)-(fn2%__hyper_frame) |
| |
| if delta >= h2: |
| delta = delta - __hyper_frame |
| elif delta < -h2: |
| delta = delta + __hyper_frame |
| |
| return delta |
| |
| def fn_time_diff_delta(fn_x, fn_ref, time_diff_hint=0): |
| frames_diff = int(round(time_diff_hint/__frame_period)) |
| fn_ref_hint = (fn_ref + frames_diff) |
| fn_delta = fnmod_delta(fn_x,fn_ref_hint)+frames_diff |
| |
| return fn_delta |
| |
| #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: |
| #* fn_ref - reference frame number modulo __hyper_frame |
| #* time_ref - precise timestamp of the first sample in the frame fn_ref |
| #* fn_x - second frame number modulo __hyper_frame, |
| #* 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) |
| #* ts_num - number of timeslot in the frame |
| |
| def fn_time_delta(fn_ref, time_ref, fn_x, time_hint=None, ts_num=0, ts_ref=0): |
| if time_hint is None: |
| time_hint = time_ref |
| |
| time_diff_hint = time_hint-time_ref |
| fn_delta = fn_time_diff_delta(fn_x,fn_ref, time_diff_hint) |
| time_x_precise = fn_delta*__frame_period+time_ref+(ts_num-ts_ref)*__ts_period |
| |
| return fn_delta, time_x_precise |
| |
| |
| if __name__ == "__main__": |
| fn1 = 10000 |
| ts_ref = 4 |
| time1 = 10.5 |
| for fn2 in xrange(__hyper_frame/2+fn1-10,__hyper_frame/2*10+fn1+100,10): |
| ts_x = int(uniform(0,8)) |
| time2 = time1 + (fn2-fn1)*__frame_period + (ts_x-ts_ref)*__ts_period |
| error = uniform(-6200,6200) |
| time2_err = time2+error |
| fn_delta, time2_precise = fn_time_delta(fn1, time1, fn2, time2_err, ts_x, ts_ref) |
| time2_precise_cpp = fn_time_delta_cpp(fn1, (int(time1),time1-int(time1)), fn2, (int(time2_err),time2_err-int(time2_err)), ts_x, ts_ref) |
| if fn_delta != fn2-fn1: |
| print "bad fn:", fn2, error#, 'fn_delta:'+str(fn_delta), time2, error, frames_diff_h4, (time2-time1)/(__hyper_frame*__frame_period), time_diff_hint_h4_prev, time_diff_hint |
| # time_diff_hint = time2 - time2_precise |
| time_diff_hint = time2_precise_cpp[0]+time2_precise_cpp[1] - time2_precise |
| |
| if abs(time_diff_hint) > 0.0001: |
| print "time2_precise_cpp",time2_precise_cpp," time2_precise",time2_precise," time_ref",time1," time_hint",time2_err |
| print "" |