gsm muxing and GPRS: am i missing something?

Michael 'Mickey' Lauer mickey at
Fri Sep 5 23:39:07 CEST 2008

Am Sunday 31 August 2008 10:38:47 schrieb Tom Yates:
> i can make a GPRS connection.  when it's up, i can place a call, and the
> outgoing GPRS connection temporarily suspends.  when it's up, incoming
> calls go straight to voicemail; the phone doesn't even give me the choice
> of accepting the call.

Yep, that's expected. See earlier discussions on this list.

> my understanding from the wiki was that "GSM multiplexing allows both a
> GPRS connection and a phone call to be handled at the same time".  so i'd
> sort of assumed that i could still take an incoming call, even if that
> would temporarily suspend the GPRS connection.

Yes, that's the theory. In practice this does hardly work and it's likely not 
a fault of the GSM chipset.

> so: have i misunderstood completely?  is the MUXing simply about sharing
> access to the modem, rather than the "line" (ie, connection between modem
> and network) as well?

>  or should i be able to take an incoming call while
> the GPRS is up?

Only, if the connection is kind of idle at this point, i.e. it might work 
while you are pinging a host, it might not work when you are wget'ting loads 
of data.

>  and if so, should the GPRS suspend while i do, or should
> i be able to run them both simultaneously?

GPRS will nicely suspend once you were lucky enough to accept the call. It 
will automagically resume.

> before i start trying to find out *how* to configure pppd to do what i
> want, i'd like to know if the phone is capable of it!  i'd very much
> appreciate any ideas or insights anyone has on this.

As it stands, there's no pppd configuration which will improve things. The 
problem is the network.


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