Video on demand

Video on demand (VoD) is an interactive TV technology that allows subscribers to view programming in real time or download programs and view them later. A VoD system at the consumer level can consist of a standard TV receiver along with a set-top box. Alternatively, the service can be delivered over the Internet to home computers, portable computers, high-end cellular telephone sets and advanced digital media devices.

VoD has historically suffered from a lack of available network bandwidth, resulting in bottlenecks and long download times. VoD can work well over a wide geographic region or on a satellite-based network as long as the demand for programming is modest. However, when large numbers of consumers demand multiple programs on a continuous basis, the total amount of data involved (in terms of megabytes) can overwhelm network resources.

 One way to mitigate this problem is to store programs on geographically distributed servers and provide programs to local users on request, a technology called store and forward. This approach increases the availability of the programming and the overall reliability of the system compared with the use of a single gigantic repository. Store and forward also allows local providers to maintain their systems and set up billing structures independently. Asynchronous transfer mode (ATM) switching technology lends itself especially well to this application.

The VoD concept is not new. The first commercial VoD service was launched in Hong Kong in the early 1990s. In the United States, Oceanic Cable of Hawaii was the first to offer it beginning in 2000, immediately after the passing of the Y2K scare. Today, VoD is offered by numerous providers, particularly those who also offer triple play services. VoD is used in educational institutions and can enhance presentations in videoconference environments. VoD is also offered in most high-end hotels. VoD will likely become more common as fiber to the home (FTTH) services become widespread.