[Tetra] current status / scrambling

Harald Welte laforge at gnumonks.org
Fri Jan 7 11:36:42 UTC 2011


Hi all,

in TETRA, the only part of the signal that is transmitted with a well-known
scrambling code is the BSCH in the SB1 (first half of the downlink SYNC block).
We can finally decode that since yesterday and get proper MCC/MNC and TDMA time
information.

The colour code + MNC + MCC is used as the scrambling sequence for all other
messages of the cell, specifically also the BNCH containing the SYSINFO
messages.

I've recently added code to indicate when a BNCH block is to follow, but the
de-scrambled type-2 bits do not look plausible at all.

So there's most likely still some problem with the de-scrambling.  The
de-interleaving, de-puncturing and viterbi decoder are the same code (even
with different parameters), so I don't think that there are likely problems
caused by them.

Regards,
	Harald
-- 
- Harald Welte <laforge at gnumonks.org>           http://laforge.gnumonks.org/
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