Data over normal GSM call

Stefan Misch misel at
Fri Apr 11 19:48:48 CEST 2008


I just talked about this issue with a colleague who uses an HTC PDA with windows 
mobile. For the data connection he uses a dial-up connection as a modem. He 
doesn't have a data plan but a flat fee for voice calls into land lines.

He says he gets about up to 4K/s which is not much of course but it's still 
possible to view light websites or emails with it. (I would not want to use it 
with Google Maps for example which is one of the key features why I would want 
mobile internet access.)

So I don't think it's impossible. Maybe the hardware and the codecs are 
different on OpenMoko but I doubt that this is an obstacle that cannot be overcome.

All best,

ramsesoriginal wrote:
> By applying some sort of modulation (fm? am? psm?) it should be
> possible to transfere data over gsm, but on a much lower speed then
> through the data channel.
> On Thu, Apr 10, 2008 at 7:34 PM, Harald Welte <laforge at> wrote:
>> On Tue, Apr 08, 2008 at 10:22:10AM -0400, Dan Staley wrote:
>>  > Does anyone know if it is legal (in the standard TOS) with providers
>>  > (such as ATnT) to send data over a normal phone call?
>>  this is not possible, since regular voice calls for GSM are not
>>  bit-transparent, i.e. the voice signal is coded and potentially re-coded
>>  (transcoded) a number of time between the calling and receiving party.
>>  Data calls over GSM are done using CSD.  They also use quite a lot more
>>  error correction than voice calls.
>>  --
>>  - Harald Welte <laforge at>         
>>  ============================================================================
>>  Software for the world's first truly open Free Software mobile phone
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