Hi. I've recently purchased a Cingular SIM card that I'm trying to use
to make a GPRS connection from Linux.

I've inserted the SIM into a Sierra Wireless AirCard 750 [1]. It's not
working.

Before I go into detail, I should mention that the config files I'm
using work perfectly with an AT&T SIM card when plugged into the same
AirCard, using the same version of the AirCard firmware (there are
different versions for different providers, though the same version of
the firmware should work for both AT&T and Cingular SIMs).

Consequently I doubt there is anything fundamentally wrong with the way
I'm trying to use GPRS, and that it's more likely something that I
don't know about how to use a Cingular SIM with GPRS. The obvious
question is whether or not the SIM is enabled for GPRS, but it was
purchased from a Cingular shop last Thursday and was only setup with a
$40 per month data plan.

Is there anything else you need to do? Do I need to specify a username
and password for example? The manual configuration guide on the
Cingular site [2] implies that there isn't.

Anyway, on to my diganostics.

My chatscript looks like this:

ABORT ERROR
'' AT
OK AT+CSQ
OK AT+CGDCONT=1,"IP","\T"
OK ATD*99***1#
CONNECT ''

When I cut and paste the key lines from the chat script into a terminal
connected to the wireless modem I get the following output. It all
looks fine to me, right up until part way through the initial hand
shake from the remote PPP server, when it says "NO CARRIER" and the
connection drops.

---cut---
Welcome to minicom 2.1

OPTIONS: History Buffer, F-key Macros, Search History Buffer, I18n
Compiled on Aug 13 2004, 08:34:08.

Press CTRL-A Z for help on special keys

AT S7=45 S0=0 L1 V1 X4 &c1 E1 Q0
OK
AT+CSQ
+CSQ: 15,0

OK
AT+CGDCONT=1,"IP","isp.cingular"
OK
ATD*99***1#
CONNECT
~ÿ}#.!}!}!} }<}!}$}&@}#}$.#}%}&_..Ç}"}&} } } }
}'}"}(}"e9~~~~ÿ}#.!}!}"} }<}!}$}~
NO CARRIER
---cut---

Note that the AT+CSQ command is reporting the signal strength, a number
that can vary between 0 and 31; 15 is plenty.

What could cause the "NO CARRIER" message to appear even though data is
being transmitted? There is a 20 second pause between the last
character of the negotiation sent by the server and the "NO CARRIER"
message appearing.

I've also recorded the logs from an unsuccessful attempt to connect
with PPP and the chatscript. I uploaded them to pastebin:

http://pastebin.com/302278

This chatscript works every time with an AT&T SIM card.

Does anybody have any ideas? I'm getting really stuck for possibilities
to explore.

Thanks,

Graham.

[1] http://www.sierrawireless.com/Produc.../AC750_GSM.asp
[2]
http://support.cingular.wdsglobal.co...ail=%2BContent



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