IMEI numbers, signal strength

mad mad at
Sun Jul 24 15:36:47 UTC 2011

Hi Ben!

> Anyone?
> On Fri, Jul 22, 2011 at 9:41 AM,  <miprom68 at> wrote:
> > Can someone help with these?
> > 1) With the GSM debugger phone, how difficult is it to get only IMEI
> numbers
> > of received packets?

First of all, it's unclear what exactly you mean by "the GSM debugger phone" as osmocom-bb is primary an implementation of a gsm stack like it's found in any standard cell phone. There is a debug output via gsmtap to e.g. wireshark where you see all received and send frames to/from your osmocom-bb.
Inherent to its hardware and open source approach it's possible to get it to dump frames received, independent of normal gsm operation. To do that at the moment it's necessary to do some work of your own, based on existing branches. 
I will try to answer your questions based on what's theoretically possible.

The IMEI is not send very often in conversations between phone and network, in fact the operator configures when (and if) it's requested from the phone. Practically some operators  request it when doing an authentication request, others only when a location update using an IMSI happened. And I've never seen it transmitted in the clear, only after encryption started. So answering your question: Very difficult, exept you know the key, e.g. on your own phone and receive at the right moment.

> > 2) Can the debugger phone report the signal strength of received packets?
> If
> > not, is it possible?

Yes, the gsmtap output contains the signal strength on every frame.

> > 3) Is there any way with mods to get I/Q out of the DSP?

I'm not sure, I think Sylvain knows more about that.

> > 4) Is there any work going on to make a CDMA debugger phone?

As osmocom-bb is (yet) an explicit GSM stack, no. And I've not heard of approaches to do so

> > 5) Are there any GSM phones that have an option to force calls to be made
> > only on 3G/4G?

GSM phones are not capable to use 3G/4G networks. Certainly you mean 3G/4G phones and disallowing 2G/GSM fallback. I've not seen that in featurephones yet (but some may allow that) but I heard it's possible on jailbreaked iphones. You should find something by searching about that.


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