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author | Piotr Krysik <ptrkrysik@gmail.com> | 2017-09-19 07:52:34 +0200 |
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committer | Piotr Krysik <ptrkrysik@gmail.com> | 2017-09-19 07:52:34 +0200 |
commit | d890cd3b368abba73003482327ee5740d5dfcf69 (patch) | |
tree | 627fd471aefbf9b2c1b7c6e60d8729a2975db77b /python/misc_utils | |
parent | 9b5617a3ef6a3a048a0521035c7454faf49d62d8 (diff) |
Added frame number operations
Diffstat (limited to 'python/misc_utils')
-rw-r--r-- | python/misc_utils/fn_time.py | 84 |
1 files changed, 84 insertions, 0 deletions
diff --git a/python/misc_utils/fn_time.py b/python/misc_utils/fn_time.py new file mode 100644 index 0000000..71e93db --- /dev/null +++ b/python/misc_utils/fn_time.py @@ -0,0 +1,84 @@ +#!/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 + +__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 + +#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=None): + if time_hint is None: + time_hint = time_ref + + if ts_num is None: + ts_num = 0 + + time_diff = time_hint-time_ref + frames_diff = int(round(time_diff/__frame_period)) + fn_ref = (fn_ref + frames_diff) + fn_delta = fnmod_delta(fn_x,fn_ref)+frames_diff + time2_precise = fn_delta*__frame_period+time_ref+ts_num*__ts_period + + return fn_delta, time2_precise + + +if __name__ == "__main__": + fn1 = 10000 + time1 = 10 + for fn2 in xrange(__hyper_frame/2+fn1-10,__hyper_frame/2*10+fn1+10,10): + time2 = time1 + (fn2-fn1)*__frame_period + error = uniform(-6200,6200) + time2_err = time2+error + fn_delta, time2_precise = fn_time_delta(fn1, time1, fn2, time2_err) + if fn_delta != fn2-fn1: + 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 + time_diff = time2 - time2_precise + if time_diff > 0.1: + print "dupa" + |