In traditional digital broadcasting, all contents are broadcasted to TV channels, regardless of whether or not the viewer is watching the TV. This basically wastes all the bandwidth that could otherwise be used for other services, such as high speed Internet and voice over IP. The new emerging technology uses complicated software to recognizes a viewer’ s request to watch a particular TV program and then sends that program to the viewer. This action takes place transparently without viewer’s knowledge.
In a cable network, groups of homes are connected on a common branch of coax cable. That is, groups of subscribers share access to the same downstream frequencies, and race for access to shared upstream frequencies. Where as, the traditional wireline networks are considered point to point, from a central office directly to a subscriber. Therefore, with sufficient switching capacity placed at the central office, infinite amount of content can be delivered to a single household. Switched Digital Video (SDV) is a new cable technology that attempts to answer this challenge. It was designed as a cost-effective method to expand program availability Best IPTV Service.
With SDV, as with IPTV, and unlike traditional digital broadcasting, programming terminates at the hub and does not go through the network unless requested. Instead, a receiver, such as set-top-box, signals upstream to request programming, and a hub-based controller receives the request and enables the stream into the network by means of a pool of allocated frequencies. In another word SDV allows operators to switch, rather than broadcast, some channels to individual service groups. A service group is typically made up of 250 or more subscribers (viewers) that use set-top-boxes to watch a TV program. Channels selected for a “switched tier” are delivered via a multicast stream only when a customer in a service group selects them for viewing.
The advantage of using SDV is that cable companies have more bandwidth available to convert into Internet channels during periods of high customer demand. The cable companies can also determine which channels are in more demand and develop localized advertising mechanism for those customers.