Broadband
In telecommunications, broadband or high speed is the wide-bandwidth data transmission that uses signals at a wide spread of frequencies or several different simultaneous frequencies. It is used in fast Internet access where the transmission medium can be coaxial cable, optical fiber, wireless Internet, twisted pair cable, or satellite.
Originally used to mean "using a wide-spread frequency" and for services that were analog at the lowest level, in the context of Internet access, "broadband" is now often used to mean any high-speed Internet access that is seemingly always "on" and is faster than dial-up access over traditional analog or ISDN PSTN services.
The ideal telecommunication network has the following characteristics: broadband, multi-media, multi-point, multi-rate and economical implementation for a diversity of services. The Broadband Integrated Services Digital Network was planned to provide these characteristics. Asynchronous Transfer Mode was promoted as a target technology for meeting these requirements.
Overview
Different criteria for "broad" have been applied in different contexts and at different times. Its origin is in physics, acoustics, and radio systems engineering, where it had been used with a meaning similar to "wideband", or in the context of audio noise reduction systems, where it indicated a single-band rather than a multiple-audio-band system design of the compander. Later, with the advent of digital telecommunications, the term was mainly used for transmission over multiple channels. Whereas a passband signal is also modulated so that it occupies higher frequencies, it is still occupying a single channel. The key difference is that what is typically considered a broadband signal in this sense is a signal that occupies multiple passbands, thus allowing for much higher throughput over a single medium but with additional complexity in the transmitter/receiver circuitry.The term became popularized through the 1990s as a marketing term for Internet access that was faster than dial-up access. This meaning is only distantly related to its original technical meaning.
Since 1999, broadband Internet access has been a factor in public policy. In that year, at the World Trade Organization Biannual Conference called "Financial Solutions to Digital Divide" in Seattle, the term "Meaningful Broadband" was introduced to the world leaders, leading to the activation of a movement to close the digital divide. Fundamental aspects of this movement are to suggest that the equitable distribution of broadband is a fundamental human right.
Personal computing facilitated easy access, manipulation, storage, and exchange of information, and required reliable data transmission. Communicating documents by images and the use of high-resolution graphics terminals provided 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. A modern telecommunications network must provide all these different services to the user.
Differences from old telephony
Conventional telephony communication used:- the voice medium only,
- connected only two telephones per telephone call, and
- used circuits of fixed bit-rates.
- multimedia,
- multi-point, and
- multirate.
Multimedia
A multimedia call may communicate audio, data, still images, or full-motion video, or any combination of these media. Each medium has different demands for communication quality, such as:- bandwidth requirement,
- signal latency within the network, and
- signal fidelity upon delivery by the network.
Multipoint
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 multipoint, multimedia communication call.Multirate
A multirate service network is one which flexibly allocates transmission capacity to connections. A multimedia 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
Traditionally, different telecommunications services were carried via separate networks: voice on the telephone network, data on computer networks such as local area networks, video teleconferencing on private corporate networks, and television on broadcast radio or cable networks.These networks were 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 had limited connectivity, usually did not have sufficient bandwidth for digitised voice and video signals, and suffer from unacceptable delays for the real-time signals. Television networks using radio or cables were largely broadcast networks with minimum switching facilities.
It was desirable to have a single network for providing all these communication services 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 was made possible with advances in broadband technologies and high-speed information processing of the 1990s.
While multiple network structures were capable of supporting broadband services, an ever-increasing percentage of broadband and multiple-system operator providers opted for fibre-optic network structures to support both present and future bandwidth requirements.
CATV, HDTV, VoIP, and broadband internet are some of the most common applications now being supported by fibre optic networks, in some cases directly 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.
Broadband technologies
Telecommunications
In telecommunications, a broadband signalling method is one that handles a wide band of frequencies. "Broadband" is a relative term, understood according to its context. The wider the bandwidth of a channel, the greater the data-carrying capacity, given the same channel quality.In radio, for example, a very narrow band will carry Morse code, a broader band will carry speech, and a still broader band will carry music without losing the high audio frequencies required for realistic sound reproduction. This broad band is often divided into channels or frequency bins using passband techniques to allow frequency-division multiplexing instead of sending a higher-quality signal.
In data communications, a 56k modem will transmit a data rate of 56 kilobits per second over a 4-kilohertz-wide telephone line. In the late 1980s, the Broadband Integrated Services Digital Network used the term to refer to a broad range of bit rates, independent of physical modulation details. The various forms of digital subscriber line services are broadband in the sense that digital information is sent over multiple channels. Each channel is at a higher frequency than the baseband voice channel, so it can support plain old telephone service on a single pair of wires at the same time. However, when that same line is converted to a non-loaded twisted-pair wire, it becomes hundreds of kilohertz wide and can carry up to 100 megabits per second using very high-bit rate digital subscriber line techniques.
Modern networks have to carry integrated traffic consisting of voice, video and data. The Broadband Integrated Services Digital Network was designed for these needs. The types of traffic supported by a broadband network can be classified according to three characteristics:
- Bandwidth is the amount of network capacity required to support a connection.
- Latency is the amount of delay associated with a connection. Requesting low latency in the quality of service profile means that the cells need to travel quickly from one point in the network to another.
- Cell-delay variation is the range of delays experienced by each group of associated cells. Low cell-delay variation means a group of cells must travel through the network without getting too far apart from one another.