osmo-trx[master]: WIP:sigProcLib: Reduce burst detection window for NB.

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Alexander Chemeris gerrit-no-reply at lists.osmocom.org
Tue May 30 21:12:48 UTC 2017


Patch Set 1:

> > Tom, could you explain why did you set search window to -/+6
 > > symbols? My experiments showed that at least `tail` should be set
 > > to 3 in order for `max_toa` to actually represent maximum TOA.
 > And
 > > same for `head` - from my experiments I think it should be 3.
 > 
 > Previous pre-search or 'head' settings on normal have come from
 > experimentation.
 > 
 > In number of symbols:
 > 
 > 5 - Original OpenBTS / Range Networks
 > 4 - Reduced during filter & SSE rewrite
 > 6 - Expanded in e90c24c8 to account for timestamp jitter in certain
 > configurations
 > 
 > With 3 symbols, have you checked TSC timing stability in the 4/1
 > sps mode where jitter is/was most severe?

That's an interesting point. I so far has tested in a receive only application where there is no Rx/Tx difference issues - we always do blind detection.

Btw, if I understand correctly what you're talking about - it's not "jitter", i.e. it doesn't change in time, there is an error which is static after PLL has been locked.

I think we should deal with it by setting max_toa accordingly instead of changing these fundamental values.

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Gerrit-MessageType: comment
Gerrit-Change-Id: If3cb40d2311504a13c03e1fbccad663ac201d9a4
Gerrit-PatchSet: 1
Gerrit-Project: osmo-trx
Gerrit-Branch: master
Gerrit-Owner: Alexander Chemeris <Alexander.Chemeris at gmail.com>
Gerrit-Reviewer: Alexander Chemeris <Alexander.Chemeris at gmail.com>
Gerrit-Reviewer: Harald Welte <laforge at gnumonks.org>
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: Tom Tsou <tom at tsou.cc>
Gerrit-HasComments: No



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