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Feature #1545

continuous timing advance loop using PTCCH

Added by laforge over 3 years ago. Updated about 1 month ago.

Status:
Stalled
Priority:
Normal
Assignee:
Target version:
-
Start date:
02/23/2016
Due date:
% Done:

0%

Spec Reference:
44.006 7.8 + 7.9 | 44.018 3.5.3.1 | 45.010 6.5.2 | 45.002 7 Mapping Table 6

Description

We currently only implement the "initial TA" where the TA of a MS is determined at time the TBF is established. If the MS moves more than 1 TA during a TBF being active, this leads to problems.

GPRS has the PTCCH for this, a special channel in the PDCH channel combination multiplex, using which we can instruct a sub-set of 16 MS (whether TBFs are active or not) to adjust their timing advance continuously. What needs to be done is
  • code to generate the PTCCH/D messages
  • code to parse the PTCCH/U messages
  • code to determine which 16 MS will be part of the current PTCCH subset
  • unit tests for the above

We also need to see how we can test this with actual hardware, in a way that TA exists (and changes) over time. Unfortuantely we don't have a MS-side GPRS implementation for OsmocomBB, because then we could simply artificially delay the transmit burst timing to make the network determine a higher TA.


Related issues

Related to OsmoPCU - Feature #1526: Acquire/update timing advance (TA)Stalled02/22/2016

Related to OsmoBTS - Bug #4102: osmo-bts-trx: incorrect PTCCH handlingNew07/12/2019

Blocked by OsmoBTS - Bug #1796: PTCCH activation breaks dyn TSClosed08/10/2016

History

#2 Updated by laforge over 3 years ago

  • Priority changed from Normal to Low

#3 Updated by laforge over 3 years ago

  • Assignee set to msuraev

#4 Updated by laforge about 3 years ago

  • Priority changed from Low to High

#5 Updated by msuraev about 3 years ago

  • Related to Feature #1526: Acquire/update timing advance (TA) added

#6 Updated by msuraev about 3 years ago

  • Related to Bug #1796: PTCCH activation breaks dyn TS added

#7 Updated by msuraev about 3 years ago

  • Related to deleted (Bug #1796: PTCCH activation breaks dyn TS)

#8 Updated by msuraev about 3 years ago

  • Blocked by Bug #1796: PTCCH activation breaks dyn TS added

#9 Updated by msuraev about 3 years ago

  • Status changed from New to Stalled

We need to figure out the way to activate PTCCH without breaking dyn TS - see #1796.

#10 Updated by msuraev almost 3 years ago

According to 3GPP TS 45.002 ยง 6.3.2.2.2 PTCCH/U is allocated on one of the TS where PDTCH are allocated to the MS. MS will send RACH in there. PTCCH/U have subchannels (0...15) assigned to different MS using TAI. PTCCH/D allocation is in Clause 7 Table 6 in the same spec. PTCCH/D frames are encoded using CS-1.

#11 Updated by laforge almost 3 years ago

  • Priority changed from High to Normal

#12 Updated by laforge over 1 year ago

  • Assignee changed from msuraev to sysmocom

#13 Updated by laforge 11 months ago

#14 Updated by laforge 10 months ago

  • Assignee changed from sysmocom to msuraev

#15 Updated by laforge 4 months ago

  • Assignee changed from msuraev to lynxis

#16 Updated by fixeria about 1 month ago

  • Related to Bug #4102: osmo-bts-trx: incorrect PTCCH handling added

#17 Updated by lynxis about 1 month ago

  • Spec Reference set to 44.006 7.8.17.9 | 44.018 3.5.3.1 | 45.010 6.5.2 | 45.002 7 Mapping Table 6

#18 Updated by lynxis about 1 month ago

  • Spec Reference changed from 44.006 7.8.17.9 | 44.018 3.5.3.1 | 45.010 6.5.2 | 45.002 7 Mapping Table 6 to 44.006 7.8 + 7.9 | 44.018 3.5.3.1 | 45.010 6.5.2 | 45.002 7 Mapping Table 6

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