diff options
| author | Vadim Yanitskiy <axilirator@gmail.com> | 2017-12-05 01:00:51 +0700 |
|---|---|---|
| committer | Vadim Yanitskiy <axilirator@gmail.com> | 2017-12-06 00:42:40 +0700 |
| commit | 9dded9b9f6e3a8a0412c2ab8f5b3e49b376d1b04 (patch) | |
| tree | 67bf34926b6aac1ad958f74e4f32c37d66b0f7ed /python | |
| parent | 7f121d6470d04242bebe4ada80bf14bd1b8c00f7 (diff) | |
trx/radio_if.py: clean up and explain GSM timings
Diffstat (limited to 'python')
| -rw-r--r-- | python/trx/radio_if.py | 16 |
1 files changed, 12 insertions, 4 deletions
diff --git a/python/trx/radio_if.py b/python/trx/radio_if.py index f84a710..e0678ab 100644 --- a/python/trx/radio_if.py +++ b/python/trx/radio_if.py @@ -66,9 +66,17 @@ class radio_if(gr.top_block): # Application state flags trx_started = False - # GSM timings - delay_correction = 285.616e-6 - ul_dl_shift = -(6.0/1625000*(156.25)*3) + # GSM timings (in microseconds [uS]) + # One timeslot duration is 576.9 μs = 15/26 ms, + # or 156.25 symbol periods (a symbol period is 48/13 μs) + GSM_SYM_PERIOD_uS = 48.0 / 13.0 + GSM_TS_PERIOD_uS = GSM_SYM_PERIOD_uS * 156.25 + GSM_UL_DL_SHIFT_uS = -(GSM_TS_PERIOD_uS * 3) + + # FIXME: shall be measured (automatically?) for + # particular device and particular clock rate. + # The current value is measured for USRP B2X0 at 26e6. + delay_correction = (285.616 + 2 * GSM_SYM_PERIOD_uS) * 1e-6 def __init__(self, phy_args, phy_sample_rate, phy_rx_gain, phy_tx_gain, phy_ppm, @@ -154,7 +162,7 @@ class radio_if(gr.top_block): self.tx_time_setter = grgsm.txtime_setter( 0xffffffff, 0, 0, 0, 0, 0, - self.delay_correction + self.ul_dl_shift) + self.delay_correction + self.GSM_UL_DL_SHIFT_uS * 1e-6) self.tx_burst_proc = grgsm.preprocess_tx_burst() |