OpenBSC with 2.5G or 3G mobile devices support? / Tested Phones

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Dieter Spaar spaar at mirider.augusta.de
Sat Jul 4 11:41:52 UTC 2009


Hello Nordin,

On Fri, 03 Jul 2009 14:44:50 +0200, "Nordin" <bouchtaoui at gmail.com> wrote:
> 
> I hope this will at least try to do a LOCATION UPDATE REQUEST.
> But it suprises me that older mobilephones don't care about SI 1 (and 
> maybe more information on the BCCH) and just try to register whatever in 
> the BCCH is.

I have further investigated the problem. Besides the fact that
the channel allocation in SYSTEM INFORMATION 1 is not correct
for GSM 1800, this is probably not the reason for the problem.

Most certainly its just one wrong bit, the GPRS indicator in
the SYSTEM INFORMATION 3 rest octets.

The current setting is

   0x80, 0x00, 0x00, 0x2B

but it should be

   0x80, 0x00, 0x08, 0x2B

What might lead to some confusion is the meaning of "L" and "H" in
the specification of CSN.1. For the rest octets the bit value is
determined by a comparsion (XOR) to the padding byte 0x2B. So the
value 0x08 above actually means "L" for the GPRS indicator, which
means "No GPRS".

Its seem that some phones are really sensible to this setting, some
other GPRS capable phones just don't care and register to the
network even if there is no GPRS.

Best regards,
  Dieter
-- 
Dieter Spaar, Germany                           spaar at mirider.augusta.de




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