Data over normal GSM call

Andy Green andy at
Wed Apr 9 00:11:57 CEST 2008

Hash: SHA1

Somebody in the thread at some point said:
| Diego Fdez. Durán writes:
|> On Tue, April 8, 2008 18:02, Joe Pfeiffer wrote:
|>> Andy Green writes:
|>>> Hash: SHA1
|>>> Somebody in the thread at some point said:
|>>> | On ti, 2008-04-08 at 16:02 +0100, Andy Green wrote:
|>>> |> I think you're right, but just a thought if you could issue
|>>> ready-coded
|>>> |> GSM codec frames, you can put the data direct in there for
|>>>> 1KBytes/sec
|>>> |
|>>> | Yeah, but you can't.
|>>> "can't" is pretty strong... isn't "not without seriously hacking
|>>> something around" better?
|>> If I understand the limitation correctly, in this case, I think
|>> "hacking something around" involves hacking at least firmware and
|>> quite possibly hardware inside the gsm modem.  That's close enough to
|>> "can't" that the difference really doesn't matter.
|> Can't you initiate a voice call between to FreeRunners and then use the
|> mic and mixer devs to modulate the data as sound?
| Yes -- but that's the technique with the claimed limitation of roughly
| 1Kbps.  It isn't inserting the raw gsm codec frames.

Right... but there is a guy in Openmoko .tw who recompiles our firmware,
subject to whatever license agreement we have, he does actually change
it.  The "can't" reduces to the architecture of the data pump in the
chips and the licence agreement in this case.  Just saying that "can't"
makes some assumptions about, eg, who is trying.  (I seriously doubt we
consider for one second to target this case, just making a philosophical
point about the absolute dangers of absolutism ;-) )

- -Andy
Version: GnuPG v1.4.9 (GNU/Linux)
Comment: Using GnuPG with Fedora -


More information about the community mailing list