Cable television companies are in the midst of a transition from their traditional core business of entertainment video programming to a position as a full-service provider of video, voice and data telecommunications services. Among the elements that have made this transition possible are technologies such as the cable data modem. The cable platform is steadily evolving into a hybrid digital and analog transmission system. Cable television systems were originally designed to optimize the one-way, analog transmission of television programming to the home. The underlying coaxial cable however has enough bandwidth to support two-way transport of signals. Recent growth in demand for Internet access and other two-way services has dovetailed with the trend within the industry to enhance existing cable systems with fiber optic technology. Upgrades of cable plant are transforming cable systems into hybrid fiber-coaxial, or HFC networks. Replacement of a part of the distribution plant with fiber optics unleashed the inherent two-way capability of the coaxial plant, without the need to replace individual subscriber connections. Systems are currently being designed with fiber running out to “nodes” serving between 500 and 2,000 homes. Here in Ireland companies such as Chorus Communications and NTL are rolling out new fibre optic networks, with fibre to each house.
We will be looking at DOCSIS™ (Data Over Cable Service Interface Specification) technology which is now known as The CableLabs® Certified™ Cable Modems project. Also taken into account will be PacketCable, an initiave to develop an interoperable interface specifications for delivering advanced, real-time multimedia services over two-way cable.At the moment there are two basic ways of getting cable into the home, this can be either fibre direct into the home, or else using existing copper which is linked into a fibre backbone.
Problems exist mainly with the copper version, RF interference is a major problem, what is a flicker or a line on a TV screen seriously interrupts a DataStream. Also bandwidth is often shared in a neighbourhood, or a street, this is an issue we ill also look at, where one user can hog all the bandwidth. Fibre direct to the house doesn’t suffer as much from these problems. As with all Internet services, they are limited by how much bandwidth the cable company has to the Internet, we will look at this from an Irish point of view.