Dear all,
Glad to meet you here, though I've met a big trouble, and I really
need your help.

I have a project right now, which is required to develop an app above
WM PDA. The app can transmit/receive formatted packets over GSM CSD
channel (9.6kbps, perhaps) from PDA to a remote PC which has a USB GSM
Modem. The project is to satisfy the data-commu requirement of our
client between remote PDA and PC at a large distance.
To achieve this goal, I decide to develop the app over WM5 based PDA,
maybe PPC Phone Edition WM5.

But I don't know some confusing critial issues :

question1. Is there any PPC Phone Edition PDA which has the similar
function of GSM Modem ?
As I know, lots of WM5 PDA can make GSM phone call and send or recieve
SMS, but I'm not sure whether the PPC PDA can send or receive data
packet over GSM CSD channel while the GSM Modem can.

question2. If question1 is ok, will the development of my app be
possible ?
I know we can control GSM modem through TAPI invoking or serial port
AT writing and reading, but most is about desktop PC.  I'm not sure
whether there is some other existing software developing interface on
the WM5, and I'm also not sure whether the TAPI of the WM5 includes
the GSM modem function.

question3. If TAPI invoking can implement the similar function of GSM
MODEM, can I use TAPI on every PPC Phone edition WM5 based PDA and
develop app without regarding the exact PDA model ?
I want to know whether there is any issues related to specific
hardware in the field of TAPI invoking.

question4. If question2 is ok,  can I write the app in C#  within .NET
CF with the support of TAPI ?

Before further working, I need to make the above four questions clear.
My knowledge on these things is still very poor so I apologize if
there are some stupid questions... and I sincerely appreciate your
answers.

PS: If you have better ideas or some thoughts or other suggestion,
please also tell me. Thanks.

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Best wishes,
skovano