Suggestions required to implement Calypso BTS with GPRS (minimal)

Altaf altaf329 at gmail.com
Mon May 27 07:24:15 UTC 2013


I have been successful in running the calypso BTS and registering phones to
it. I have also examined the source code implemented.

I am currently doing an Internship in Berlin and the company wants to
demonstrate to it customers that 2G services are not secure. Basically we
are designing a securtiy demonstrator. We want to do man-in-the-middle
attacks with the existing open source s/w. So we thought a B100 USrp would
be the need of the hour. But I am really interested working with the calypso
phones because I am comfortable with the source code and have already worked
on it.

I want to try (do) implementing the GPRS functionality to this calypso BTS.
Since the work is mostly involved at Layer1 or lets say transceiver. 

I tried running OpenBTS-gprs version and resulted with some info. The
mframe_sched in the trx doesnt contain info about the how to handle packet
channels or the multiframes do not have the Packet channels. So when the BTS
assigns (on CCCH) a dedicated channel and the calypso phone fails to receive
uplink or doesnt provide a way for the phone to access the BTS. I understand
the working of trx and want to add this GPRS functionality to trx. I am
aiming to implement minimal GPRS functionality. I have also seen how
OpenBTS-gprs has triggers this packet channel or the way multiframes handle
PDCH, PTCH.. By observing them I can get some idea.

In this regard I request from you few suggestions such as where I have to
work more and what are the challenges I will face. your suggestions are
valuable to me.



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