Video Conferencing over ISDN and the Migration to IP
While the technology has been around for decades, the challenge has been the transmission of the significant amount of data required for a video session. Video consumes incredible amounts of bandwidth. For one picture of 352 X 288 pixels with 2Bytes per pixel there is a need for a 1.6Mbps connection to support a video call. Even for a ten frame per second call, the total bandwidth would be 16Mbps.
Up until the late 1980’s there was practically no network that could carry this amount of data to end-users. In order to enable video telephony, the video bandwidth needed to be reduced by means of compression. Telephony operators realized this in the early 1970’s and a new network, ISDN, was designed, defined and implemented gradually by the telephony operators.
Advanced mathematical research generated algorithms for reducing the bandwidth without much loss in the quality of the picture to enable ISDN to carry compressed voice and data (note: data in this case includes video signals).
As a result, video communication started to find its way into enterprise networks in the late 1980’s due to four main factors; ISDN was operational and the manufacturer only needed to develop the endpoints, compression algorithms were developed that reduced the amount of video data to be transmitted, it was possible to implement these algorithms in silicon, thereby enabling video conferencing systems, ISDN was available almost all over the world enabling communication between enterprises throughout the world.
Unfortunately, ISDN was an imperfect network technology for video communications. To achieve high quality video signals there was a need for multiple channels of ISDN to support the high bandwidth needed, even after advanced compression algorithms were applied. There were also issues with stability (line drops, different delays between channels), the high cost of a call, and the requirement of installing new individual ISDN lines into every location where video communication was desired.
Even with these technology and cost barriers, the ISDN standard, called H.320, was a success. Vendors developed endpoints that could communicate with each other worldwide. Companies like CLI and PictureTel and later Polycom and Tanberg became the leaders in video communication with huge meeting room endpoints that connected directly to an ISDN line provided by a service provider.
Meeting room conferencing was a natural fit to ISDN. The number of rooms equipped with video conferencing equipment and with ISDN lines was small. It was therefore an acceptable expense for the relatively expensive equipment and the cost of the communication lines. However, all attempts to roll out ISDN to the desktop failed.
Other Video Telephony ITU Standards for different Networks such as ATM (H.321 and H.310) and PSTN (H.324) were attempted but did not succeed. The PSTN’s inherent low quality was not sufficient for video communication. ATM, which held huge promise for a new packet-based voice and data network (including compressed video), fell victim to IP. Just as ATM was maturing to the point of taking off, IP became the dominant protocol on any data network due to the success of the Internet.
Therefore, with ATM failing for data communications, there was no compelling reason to sustain it just to support video communications.
However, with the rise of IP in the LAN and WAN, packet-based communications solutions began to find their way into the enterprise. In 1995 the ITU began to define the Standard for Multimedia communication over Packet (IP) Networks, the H.323 Standard. SIP, MGCP and MEGACO are additional protocols that have recently come out to carry rich media over IP.
The rise of IP for video not only enabled more cost effective room-based solutions but also enabled the delivery of video communication to the enterprise desktop. In the continuing evolution of network protocols, IP has become the right network in the right time.
There are compelling reasons why more and more businesses are now in the process of migrating their communication networks from ISDN to IP.
IP has delivered a huge amount of benefit to the end user and, now that network technologies and bandwidth availability issues are taken care of, there is a huge momentum to adopt IP-based communications platforms.
By switching from an ISDN network to IP businesses can reduce operating costs, improve communication capabilities and provide simpler, more productive integrated communications platforms.
The majority of video conferencing systems available today support operations on both ISDN (H.320 protocol) and IP (H.323 protocol) networks.
Changing needs in the telecommunications market call for scalable and interoperable solutions that support packet networks. The growing number of optimised packet platforms, which are replacing circuit-switched platforms, is a clear indication that IP networks are a significant factor in the telephony carrier market.
Currently, most telephony processing and switching equipment is based on TDM. However, TDM’s inherent properties hinder it from meeting the dynamic and evolving demands of modern data networks.
Although the synchronous transmission of TDM telephony is well suited for reliable voice synchronization with no lag, this synchronous model also imposes restrictions that limit flexibility, expansion and growth.
The fundamental paradigm of packet networks is asynchronous transmission. This is a flexible model that lends itself to fast and cost effective expansion, growth and resulting scalability.
That is why IP is so appealing. Media-rich IP for voice and visual communications enable Service Providers and Telcos to offer a variety of features and services with rapid time-to-market and at lower costs. As media-rich IP becomes the preferred way of delivering voice and video, the IP devices needed, such as switches, gateways, bridges and routers, are being developed in increasing numbers.
Benefits of IP-centric visual communications
IP-only visual communications systems are typically less expensive than ISDN based systems. There is no need for ISDN-interface circuitry and software. When PCs are used as the basic processing engine for IP conferencing, the only cost is a simple camera.
Lower Usage Fees
Users of IP networks do not have to pay per minute usage fees. Most video calls originating and terminating on the corporate IP network will be absolutely free of charge.
Using the IP network allows users to avoid the fragile bonding of multiple ISDN data channels necessary for an ISDN video call. This results in significantly higher reliability.
High costs of purchasing and installing ISDN based video systems has limited the number of deployments in large conference rooms. As IP-centric systems are less expensive to purchase and IP network lines are easier and cheaper to deploy, more video system installations in offices, even homes, are possible.
Enhanced Audio and Video Quality
The quality of a video conference depends heavily upon the bandwidth (data rate) of the connection. Because ISDN based video utilizes a combination of data channels each offering 64 kbps of bandwidth, a standard business quality video call requires the use of 6 ISDN B channels, to provide the necessary 384kbps bandwidth. On the other hand, IP networks typically offer at least10 Mbps (or almost 27 times more) bandwidth to each video system. Therefore, a standard IP video call might be placed at speeds of bf 512 kbps or even higher, resulting in an enhanced level of audio and video quality.
A major advantage of deploying IP based video conferencing is the ability to leverage the primary data network for video conferencing, resulting in cost savings and increased efficiency.
IP-centric networks mean no more dedicated data lines. Using packet-switched IP networks means that many data and video systems can share dynamically allocated bandwidth. This means that if the required bandwidth momentarily drops, other systems can pick up the slack and utilize it.
IP based video systems are always connected to the packet-switched network, which allows these systems to be remotely controlled and managed.
Improved Call Permission and Automatic Billing
Most large scale video conferencing deployments enjoy the benefits of an IP-based software product called a gatekeeper, to control and track usage of the system. By properly configuring these gatekeepers, organizations determine which calls to permit, at which speeds, to and from which users and systems, and across which networks. Savvy managers can manipulate this information into a form useful for internal billing and cost allocation.
IP based video systems, specifically PC based camera only solutions, are less expensive to deploy. This has paved the way for nearly unlimited deployment of video conferencing capability throughout the enterprise as it grows.
The Importance of High-Bandwidth Networks and Advanced Digital Signal Processing (DSP) Technologies
The availability of high- bandwidth networks is continuously expanding to reach all corners of the globe. This is what makes IP-based rich media collaborative communication applications possible. With the promise of evermore affordable bandwidth, the IP protocol lends itself to cost effective data collaboration, voice telephony and multipoint visual communications.
Advanced DSP technologies are what make it possible to deploy real-time video conferencing capabilities in popular common consumer devices such as, cellular phones, televisions, PDAs and PCs.
Thanks to DSP technology, the days of dedicated conference rooms, equipped to the hilt with cumbersome and costly servers and video conferencing cameras are long gone.
The ability to use packet-based IP broadband networks for real-time communications is fuelling renewed interest in converged communications, meaning future growth. IP overcomes the physical limitations of transferring huge amounts of data required to share video images. Advanced gateways make integration with legacy ISDN and other networks a simple procedure as well.
In addition, demand is fuelling technological development, as video and video-based applications become more and more popular. As the technology advances, video conferencing is now reaching the 3G mobile arena and applications to include scheduling, streaming, Web conferencing, instant messaging and much more.
To communicate visually today, all you may need is a low cost Web cam. Office orientated applications, such as Microsoft Office, have embedded features that enable users to create and schedule ad-hoc conferencing and collaboration sessions right from the desktop. Interactive video-enabled cellular phones, PDAs, PCs and televisions, in every size, shape and form, are becoming more and more available at reasonable prices.