History of Asynchronous Transfer Mode ATM
INTRODUCTION
History of ATM
Asynchronous Transfer Mode or ATM came about through the evolution of the Integrated Services Digital Network (ISDN) in the 1980's and the demand for high-speed packet communications. This extended further into the higher speed solution of Broadband ISDN with the intention to provide integrated broadband services such as high-speed telephone, data and video communications.
In 1988, the International Telecommunications Union (ITU) defined ATM as the vehicle for B-ISDN with a view to it becoming the universal network transport. It is the ability to serve different service types, together with fast transmission rates and low overheads, which is leading to the widespread use of B-ISDN today. More information may be obtained from [Ref. 6]
Efficiency Issues of a Transmission System
In the transfer of data, whether it be voice, video or computer data it is common to use some form of compression technique in order to use the transmission medium efficiently. These data compression techniques commonly include some form of Run Length Encoding (RLE) to remove redundancy within a signal and thus reduce the bandwidth consumed by the transmission. Although, data compression is performed at a much higher level, ATM achieves its efficiency by making use of small, compact packets with a small header field, maximising the user information to system overhead ratio leading to higher data rates than other transmission mechanisms.
Image and Video Compression
Again in the late eighties, the MPEG standard for video compression was born and defined as a compression standard mainly for CD-ROM applications. This standard was closely followed by the MPEG-2 standard widely used today in the compression of pre-recorded video. Unlike M-JPEG compression, MPEG-2 works by predicting the movement of objects within a picture, producing a series of related frames each of which depends on a single start image. The relationships between frames can become very complex unlike those in M-JPEG compression, which may function independently or in a video stream. As MPEG compression is beyond the scope of this project more information on the mechanisms involved may be found in [Ref. 4, 5, 6].
Applications for ATM
ATM has enough flexibility to provide transport for a wide range of services including audio, video and raw data. Not only may it accommodate any one of these, but also it may successfully accommodate a mixture of data types. Each type however has its own optimum transmission characteristics. Transfers such...