GSM Tech

Torsten Schlabach tschlabach at
Sat Dec 15 11:30:18 CET 2007

Hi all!

Thanks everyone for the great pointers. I think there's lots of stuff to 
digest and research.

 > but FIC may not appreciate the discussion on
 > their mailing list either.

Well, as Neo's don't come with a SIM lock, there's hardly a point here.

Besides that, I can see nothing wrong with trying to implement the 
officialy published SIM Access Profile. And I think we need to know now 
what to look for.

The question one could debate is to that extend this is a GSM technology 
mailing list or not, especially if we'd go further down the road of:

 > Henryk Plötz wrote:
 > IIRC you'd need dual radios for [... using two SIMs at a time]
 > anyways.

I understand that GSM is based on time slots. So theoretically, I should 
be able to make the same radio talk to network A in one timeslot and 
network B in another. But that might be too simplicistic for whatever 
reasons. Also there is still the use case that I had two SIMs (just with 
different numbers and maybe different accounts == phone bills) but still 
on the same phyiscal GSM network. At least that should be doable with 
one radio, shouldn't it?

Well, I think this is getting OT for this list, isn't it?


Steve schrieb:
> Joe Pfeiffer wrote:
>>(just a couple of additional comments to what Steve says)
>>Steve writes:
>>>The GSM Modem as a black box:
>>>>From my understanding of the NEO 1973, the GSM modem is roughly
>>>analogous to a computer modem from the past.  (Not the cheap "winmodems"
>>>that are so abundant these days.)  It is connected via a serial
>>>connection to the portion that runs open software and communicates over
>>>the GSM network.  TI has provided a set of "AT" commands to preform a
>>>limited subset of the functionality that the modem is capable of.  If
>>>you want to use more advanced or unintended functionality, you'll have
>>>to figure out how to do that on your own.
>>The AT commands are actually part of the GSM standard (I don't know if
>>TI has agumented, nor if they've implemented all of them).  My
>>understanding is that getting any additional functionality out of it
>>starts with prying the cover off the chip and goes downhill from
>>there :) 
> I'd agree with the statement about the AT commands, but I do think its
> probably possible to get unintended functionality out of the GSM modem
> without resorting to decapping the chip.  After all that is exactly what
> the unlockers are doing.
> The unlockers are probably a major reason why TI is so paranoid about
> the workings of their chipset since that is where the SIM and provider
> locks are usually implemented.  I wish I could give you more information
> about the techniques they use, but I don't know what they are.  It would
> be interesting to find out, but FIC may not appreciate the discussion on
> their mailing list either.
> -Steve

More information about the device-owners mailing list