The Technology

While the Access Grid involves creating state of the art collaboration technology, whenever possible it leverages existing standards based hardware and software.

All video and audio handling is done with commodity hardware and software. On the video side, any video camera and video capture card that works under Windows or Linux will work. Video streams are handled using the Vic application. The WPI node uses four Sony PTZ cameras and four standard BT878 video cards. The display is accomplished by three large rear projection displays operating at 1024x768 driven by multiple video cards in a dedicated computer.

Audio is provided to a standard Soundblaster sound card by a pair of Gentner XAP800 audio conferencing units and a TH2 telephony bridge module. The Rat application handls playing and transmitting the streams. In addition, all audio and video is routed through an AV switcher, providing enourmous flexibility, including the ability to route external signals, such as projectors, laptops, and the campus TV studio in and out of the room.

On the network side, the Access Grid relies heavily on multicast networking. Multicast enables a stream to be sent to a specified set of remote sites without having to duplicate each packet for each destination. Instead, the network at each intermediate step will create multiple copies of the stream if and only if it is actually required. This keeps the bandwidth requirements of a given session from increasing at an exponential rate as more participants are added, and allows many sites to particpate at the same time.

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Last modified: Jul 24, 2003, 16:21 EDT