Wednesday, July 8, 2009

Modern communication services

Society is becoming more informationally and visually oriented. Personal computing facilitates easy access, manipulation, storage, and exchange of information, and these processes require reliable data transmission. The means or media for communicating data are becoming more diverse. Communicating documents by images and the use of high-resolution graphics terminals provide a more natural and informative mode of human interaction than do voice and data alone. Video teleconferencing enhances group interaction at a distance. High-definition entertainment video improves the quality of pictures, but requires much higher transmission rates.

These new data transmission requirements may require new transmission means other than the present overcrowded radio spectrum [3][4]. A modern telecommunications network (such as the broadband network) must provide all these different services (multi-services) to the user.


A few examples will be used to contrast point-to-point communications with multi-point communications. Traditional voice calls are predominantly two party calls, requiring a point-to-point connection using only the voice medium. To access pictorial information in a remote database would require a point-to-point connection that sends low bit-rate queries to the database and high bit-rate video from the database. Entertainment video applications are largely point-to-multi-point connections, requiring one-way communication of full motion video and audio from the program source to the viewers. Video teleconferencing involves connections among many parties, communicating voice, video, as well as data. Offering future services thus requires flexible management of the connection and media requests of a multi-point, multi-media communication call


A multi-rate service network is one which flexibly allocates transmission capacity to connections. A multi-media network has to support a broad range of bit-rates demanded by connections, not only because there are many communication media, but also because a communication medium may be encoded by algorithms with different bit-rates. For example, audio signals can be encoded with bit-rates ranging from less than 1 kbit/s to hundreds of kbit/s, using different encoding algorithms with a wide range of complexity and quality of audio reproduction. Similarly, full motion video signals may be encoded with bit-rates ranging from less than 1 Mbit/s to hundreds of Mbit/s. Thus a network transporting both video and audio signals may have to integrate traffic with a very broad range of bit-rates

A single network for multiple services

Traditional networks
Traditionally, the various services mentioned above were carried via separate networks: voice on the telephone network, data on computer networks or local area networks (LANs), video teleconferencing on private corporate networks, and television on broadcast radio or cable networks.
These networks are largely engineered for a specific application and are not suited to other applications. For example, the traditional telephone network is too noisy and inefficient for bursty data communication. On the other hand, data networks which store and forward messages using computers have very limited connectivity, usually do not have sufficient bandwidth for digitised voice and video signals, and suffer from unacceptable delays for the real-time signals. Television networks using the radio or the cable medium are largely broadcast networks with minimum switching facilities

Benefits of a single network for multiple services

It is desirable to have a single network for providing all these communication services in order to achieve the economy of sharing. This economy motivates the general idea of an integrated services network. Integration avoids the need for many overlaying networks, which complicates network management and reduces flexibility in the introduction and evolution of services. This integration is made possible with advances in broadband technologies and high speed information processing [2][3].
Fibre optics for:

broadband networks and MSO

While there are multiple network structures capable of supporting broadband services, an ever increasing percentage of broadband and MSO providers are opting for fibre optic network structures to support both present and future bandwidth requirements.
CATV (cable television), HDTV (high definition television), VoIP (voice over internet protocol), and broadband internet are some of the most common applications now being supported by fibre optic networks, in some cases directly to the home (FTTh – Fibre To The Home). These types of fibre optic networks incorporate a wide variety of products to support and distribute the signal from the central office to an optic node, and ultimately to the subscriber