The multimedia future of PBXs - private branch exchanges - Technology Information

As the data communications world experiments with a variety of transports and protocols for integration with the voice network, it is caught up in a rapid-fire sequence of upgrades perpetually in need of more bandwidth.

Bandwidth congestion has increased exponentially since the adoption of the Web and graphic-rich communications on personal computers. This situation is not likely to improve with the popularization of IP-based communications freeware, such as Microsoft's Net Meeting.

PBXs will continue to add value to enterprise communications as manufacturers actively pursue new markets beyond voice-only -- and their installed base is listening. For example, Lucent Technologies' Intuity Audix customers now have the opportunity to expand their Audix functionality to include voice mail and e-mail management. Some PBX providers are climbing on multimedia and video bandwagon to leverage their existing switched network and infrastructure (both human and physical).

"I have personally designed and supervised the installation of some of the largest baseband data networks in the world, and using the internal telephone wiring to deliver full-duplex video, stereo audio, and high-speed data technology makes LAN-based video networks using H.323 seem archaic," says Seth Hoerth, vice president of VIVID Resources, a value-added reseller of video solutions.

There are compelling reasons for PBX manufacturers to take a leadership role in the integration of real-time-video-to-the-desktop. The first reason has to do with the quality of the video session itself. When users place a call with a video-ready apparatus, be it a computer or a dial pad associated with a "black box," they don't want to see the quality of service degrade during the call. Dedicated services cannot be guaranteed in a data networking environment optimized for transactional data (for example, Ethernet or token ring running Internet protocols).

Quality video communications require a switched connection like the one already provided by the telecommunications infrastructure.

Another advantage of the PBX over any data network service for video communications concerns management of the call environment (dialing plans, billing and other supplementary services, messaging, etc.). These technologies and applications are extremely well understood and designed for voice services.

There are several architectural approaches to building a high-quality video network. One is simply to pull coaxial cable to each desktop and conference room. The video is connected through a centrally located switch.

Separate cables are needed for full-duplex transmission and for the left and right audio channels each way. This approach is obviously cumbersome, and is often unfeasible because of the sheer mass of cabling.

Twisted pair is not effective, by itself, for the transmission of broadband signals. It is possible to transmit video this way using equalizers (or filters) to overcome frequency dispersion and then amplifying to overcome high loss. It is not possible to run other signals concurrently on the same cable because equalized-video occupies the same spectrum as the LAN or telephony signals. Separate twisted pairs are also required for transmitting and receiving video.

Another way to supply combined voice and video is through a physically integrated video branch exchange that runs video over the same twisted pair as the house phone.

A video branch exchange is a broadband switch that performs functions analogous to, and in combination with, a PBX to provide a variety of video communications. The user can initiate and receive videoconferences from the desktop PC, television, or large screen display.

Depending on the caller's destination, the switch negotiates the call in the enterprise or over a wide area integrated digital service or ATM network. The user can use the same system to retrieve or create stored video files, access a private or public television network broadcast, participate in a multipoint live meeting, or collaborate on a document.

Hoerth puts it well: "Communications and networking people have said for years that in a perfect world we would have one management platform, one communications platform, one cabling system, one budget and one group of people running it -- and if it ran like a phone switch, wouldn't that be great?"

Hoerth has made it work: "In a network situation, on a PC workstation you can have four windows of uncompressed video while doing a data transfer that will rival an Ethernet transfer while listening to four voice conversations, So you have voice, video, and data running at the same time, and since it's running on copper -- the same two wire that my phone runs on and my phone can still ring -- that's a lot like magic."

Using the inherent strengths of the PBX, it is possible to step up to an integrated branch exchange, which will soon give both users and administrators the functionality, quality, and reliability of the telephone network combined with the affordability of integration.

Finally, PBX manufacturers will lead the charge for high-quality video communications using existing wiring to every room or desktop in a cost-effective route.

COPYRIGHT 1998 Nelson Publishing
COPYRIGHT 2000 Gale Group