PHARscape

chmaruni · Joined: 14 Jun 2006 Posts: 2

Hello *,

we are currently working on a course for computer science students in which they are supposed to implement/setup a system for making multi-point video conferences between 3g mobile phones and PC clients.

Since it is obviously hard for us to get access to a real UMTS gateway (even though we collaborate with a telco provider) we think about simulating a "one link" gateway by a PC and a UMTS datacard. The gateway would then translate between H.323 on the IP side and 3G-324M for the mobile phones.

So here are a bunch of my questions:

Does anybody has experience whether or not it is possible to set up "normal" audio and video connections via a datacard?

For example, is it possible that I do not call the *9# number for making a data connection but to call any number of another cellphone?

And can I call my PC datacard which will then answer the phone?

If I make a connection (or call) with the datacard, how is the datastream set up programmatically? (i.e., is it a normal socket with basically a read and write method?)

I think that the basic idea should be valid, because I found a softphone that allows one to make a video call with another cellphone via a datacard (according to the webpage, I did not try it: http://www.dilithiumnetworks.com/products/VT_Phone.htm).

Thank you very much in advance for your help, I really appreciate any hint you can give me!
Christoph

(Note: it is intended that the students learn something about 3G technology. So using a mobile as a modem and simply using skype might solve the "problem" of video conferencing but it is not what we want to do)

jamiefiedler · Joined: 24 Mar 2006 Posts: 11 Location: Boston, MA

while there are a couple pc cards that are able to handle CSD calls like you are referring to, they only run at 9600bps. definitely not able to do video in any aspect.

the cards only simulate a ppp connection to make communication with host systems easier to manage and setup. there is no actual ppp connection made beyond the card itself - it's a completely different beast from the radio out.

that software you found simply uses the existing data connection as skype would - ip communication. there is no "direct dial" functionality between two cellular card users.

chmaruni · Joined: 14 Jun 2006 Posts: 2

Hi jamiefiedler,

thank you for your reply; this is exactly what I also found out during the last days of research. However, it feels good to get my unconfirmed and self-made thoughts confirmed by another person!

CU
chmaruni

andrewbird · Joined: 13 May 2006 Posts: 15 Location: Rugby

Hi both
This technology is certainly possible with the 3G/UMTS. The client from Dilithium Networks is rebadged by many of the major mobile networks. I have made Video calls between this client and 3G phones. It also does PC - PC calls using two clients. The technology makes use of a circuit switched guaranteed 64K synchronous channel. You should look at;

http://www.dilithiumnetworks.com/products/H324.htm
http://www.nmscommunications.com/DevPlatforms/OpenAccess/Technologies/3G324MandIPVideo/TechnologyOverview.htm

and the ITU specs H.324M, H.245 & H.223

I should say that this is proper mobile telecoms technology with published specifications and has no dependencies on the Internet or closed protocols.

The PC Cards required for this are the standard mobile datacards available from the major networks, eg Vodafone

Hope this helps

Andrew

kvangend · Joined: 12 May 2006 Posts: 31 Location: Eindhoven

I don't think this will work well.

UMTS is notorious for slow round trips, setting up an TCP connection will take 2 seconds.

So, as long are you are streaming video, you will be OK, but as soon as you need to reply on someone, either over voice or e.g. chatting, you'll hit at least a second delay.

But I could be wrong...
And I would be very interested to hear how to work around this...

andrewbird · Joined: 13 May 2006 Posts: 15 Location: Rugby

Hi
UMTS does have poor latency and if you were to implement some sort of IP(TCP even worse) based video telephony service over it, things would not work very well. The protocol in use for 3G video telephony is based on several logical channels(video,voice,control) multiplexed into a single stream. This is sent over a circuit switched guaranteed 64K synchronous channel. There is no IP involved.
I urge you to read the info linked to above, and download the ITU specs. These will answer your questions in far greater detail than I can. In essence, do you find the latency acceptable using a normal mobile phone? As the experience should be no worse using a 3G VT handset or PC application.

Andrew

Paul · Posted: Fri Jul 07, 2006 11:01 am Post subject:

For Video work you can use CSD and the Option 3G cards do support it. This is equivalent to the HSCSD that Nokia had for 2G connection. CSD is best for the latency issues you refer too and is designed for interactive multimedia.

It would be a dedicated connection purely for the video call. You would also need the relevant software at both ends and I bet the system will need to be configured to support it (for example incoming calls need to be setup using the CSD connection - just like in GSM where there a separate numbers for voice, data and fax connections).

PS video conferencing achieves reasonable performance in walled garden services where the operator can control the QoS and can offer better than "best efforts" on latency.

Paul

Robybob · Joined: 27 Dec 2006 Posts: 2

[quote="Paul"]For Video work you can use CSD and the Option 3G cards do support it. This is equivalent to the HSCSD that Nokia had for 2G connection. CSD is best for the latency issues you refer too and is designed for interactive multimedia.

It would be a dedicated connection purely for the video call. You would also need the relevant software at both ends and I bet the system will need to be configured to support it (for example incoming calls need to be setup using the CSD connection - just like in GSM where there a separate numbers for voice, data and fax connections).

PS video conferencing achieves reasonable performance in walled garden services where the operator can control the QoS and can offer better than "best efforts" on latency.

Paul[/quote]

Paul, if I have understood, I can do a Circuit Switch Call and a CSD UDI call with a GT (i.e.: Fusion+ HSDPA) card. Do I need specific driver or Nozomi 2.1 can handle it ?

Robybob