PLMN identity: 04.08 vs. RANAP

Neels Hofmeyr nhofmeyr at sysmocom.de
Wed Apr 6 15:46:49 UTC 2016


On Wed, Apr 06, 2016 at 05:18:54PM +0200, Daniel Willmann wrote:
> > In 3GPP TS 25.413 in 9.2.3.55 PLMN Identity, I see a very similar definition
> > for BCD coding, but it omits the detail to put the last MNC digit into the
> > second byte. So, by omittance, it defines a different coding from 04.08:
> >   21 f3 54 (same)
> > but
> >   21 43 65
> > respectively.
> 
> This is what the hnb does. A PLMNID of 901123 results in
> 09 11 32 being transmitted in HNBAP.
> PLMNID of 90123 corresponds to 09 f1 32
> 
> The RANAP fields for LAI and SAI are encoded the same.
[...]
> Since the coding differs I wouldn't try to merge the implementations.
> I'd think that it would obscure more than it helps.

Excellent, thanks for testing it!! Quite curious result though.
I agree to not use gsm48_mcc_mnc_from_bcd() directly, but maybe
ranap_parse_lai() can reuse some more general bcd code...

~Neels

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