location update problem

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Harald Welte laforge at gnumonks.org
Wed Jun 24 04:58:49 UTC 2009


On Tue, Jun 23, 2009 at 08:29:33PM +0200, Andreas.Eversberg wrote:
> harald,
> 
> i checked the msg_4 array. i found the power info in the description,
> but i cannot see where the values are in the array. 

The SI is highly bit-packed information, you will need to read the specs in
order to understand and parse it.  I don't have any more convenient
information, I have to do the same whenever I want to change something.

We could certainly need some code to pack/unpack the information from a more
conveninet C structure into the actual on-air format.

> also i don't really know the maximum power value for BS11 (GSM 900). is 0db
> maximum? is it relative to the BS power class?

The "MS Power" IE is independent of the BS power or BS power class.  It is an
absolute value in dBm as specificed in GSM05.05 and the definition/mapping
between power IE values and dBm is specified in tables of GSM 05.05.

I have committed some unused code for this translation to dBm in http://bs11-abis.gnumonks.org/trac/changeset/fcd2445d05e24c20310790ef0041c8cbe6e6546d - search for
ms_pwr_ctl_lvl() which you can call with the desired dbm level (i.e. 50 which is higher than any phone can transmit) and it will return with the highest possible
value for the BS power IE.  If the phone then supports less than that, it will
in turn use the maximum it has.

For the BS11 in GSM900, the maximum seems to encode to '0'.

> anyway, i found the bug about holding the location update process. i
> fixed it, but before i supply a patch, i will check if this really works
> when the link fails during location update again.

good news!

-- 
- Harald Welte <laforge at gnumonks.org>           http://laforge.gnumonks.org/
============================================================================
"Privacy in residential applications is a desirable marketing option."
                                                  (ETSI EN 300 175-7 Ch. A6)




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