Change in osmo-bts[master]: ta_control: Allow switching TA quicker

[pespin]

Hello osmith, Jenkins Builder, laforge, dexter, 

I'd like you to reexamine a change. Please visit

    https://gerrit.osmocom.org/c/osmo-bts/+/25434

to look at the new patch set (#2).

Change subject: ta_control: Allow switching TA quicker
......................................................................

ta_control: Allow switching TA quicker

>From TS 45.010 5.6.1 (delay tracking for circuit switched channels):
"""
Restricting the change in timing advance to 1 symbol period at a time
gives the simplest implementation of the BTS.  However the BTS may use
a larger change than this but great care must then be used in the BTS design.
"""

In general 1 TA at a time (every 480ms of SACCH block) should be enough,
since section 5.6.3 states:
"""
The control loop for the timing advance shall be implemented in such a way that it will cope with MSs moving at a
speed up to 500 km/h
"""
Which is ~140 m/s, and 1 TA step around 500m, so most of the time we
should be save and no steps of more than 1 TA should be required.
However, unlikely changes from reflected to direct signal or vice versa
could produce higher increments, so let's increase the maximum step size
allowed to 2 in order to give more room.

Change-Id: I9e48faabf3090588233e274b2b39065cf85fbec7
---
M src/common/ta_control.c
M tests/ta_control/ta_control_test.ok
2 files changed, 232 insertions(+), 232 deletions(-)


  git pull ssh://gerrit.osmocom.org:29418/osmo-bts refs/changes/34/25434/2
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Gerrit-Project: osmo-bts
Gerrit-Branch: master
Gerrit-Change-Id: I9e48faabf3090588233e274b2b39065cf85fbec7
Gerrit-Change-Number: 25434
Gerrit-PatchSet: 2
Gerrit-Owner: pespin <pespin at sysmocom.de>
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: dexter <pmaier at sysmocom.de>
Gerrit-Reviewer: laforge <laforge at osmocom.org>
Gerrit-Reviewer: osmith <osmith at sysmocom.de>
Gerrit-MessageType: newpatchset
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