Previous | Table of Contents | Next |
As the communications and transmission systems evolved, the manner in which intelligent information was communicated (encoded) advanced also. From a series of grunts to a meaningful staccato beat on a tree trunk, written messages, a set of dashes and dots, electronic reproduction of the human voice, and binary ones and zeroes, state-of-the-art information encoding techniques have kept pace with the communications and transmission systems evolution. Drums gave way to Morse code, Morse code gave way to the telephone, and now we have high-speed communications systems that can transport digital data representing intelligent information at rates of gigabits per second around the globe.
Modern society has come to depend upon communications and transmission technology for a wide range of business, personal, and governmental services. Low-speed and high-speed data communications, audio, video, wireless, personal communications, and Plain Old Telephone Service (POTS) are some of the communications services that are important to the daily conduct of human affairs. Additional teleservices such as virtual cinema, virtual theater, video conferencing, videotelephony, video library, home education, full service multimedia (audio, text, video, images), and high-definition TV (HDTV) will be economically available to every business, home, and apartment in the near future.
A quick survey of some recent developments in communications reveals that usage of communications systems is limited only by the communications networks themselves, and not our ability to envision more productive uses of the networks.
Figure 1-3. A communications-hungry society
Currently, medical personnel in remote locations in Australia use electronic sensors to capture the condition of ill patients. Such practices are extremely common and normally would not elicit any passing comment. However, the patient data garnered, including detailed video images of patients external and internal ailments, are transmitted via high-speed data communication networks to centralized medical facilities where specialists are available around the clock to evaluate and recommend treatment. For difficult operations, health care professionals can even participate directly in the specific treatment. For budget stricken, small health care facilities, regardless of location, such usage of the existing communication networks provides a much higher quality health care service than could otherwise be economically achieved. Imagine a doctor in a studio operating on a patient thousands of miles away by manipulating robot arms using virtual reality technology.
High-tech movies today consist of many live action shots intermingled with computer-simulated characters and scenes. Several high-tech companies located around the country are the creative technical energy behind many of the recent blockbuster hits. These companies generate digital data by the bucket full (I am referring to a big bucket). Using expensive supercomputers, they simulate all manner of things. Connected to dedicated Integrated Services Digital Network (ISDN) telephone lines, they ship digital data back and forth between their offices and the movie studios. Imagine participating in a movie as one of the cast while remaining in your home.
Due to the unique requirements of different communication services, multiple information coding and transmission techniques were developed to deal effectively with the various needs of a communications- hungry populace. The Public Switched Telephone Network (PSTN), Community Antenna Television (CATV), Direct Broadcast Satellite (DBS), and private local area networks (LANs) are some of the incompatible communication systems utilized to transfer service-specific information from one location to another. These various communication networks were not designed to transport information in realms other than the specific service they were designed for. While one can modify a specific communication system to adapt and transport information derived from another system, such adaptation of the information and system is expensive and slows the transfer rate. Multiple service-specific communication systems, layered one upon the other, are expensive to build and maintain.
As our desire to communicate across service-specific barriers grew, driven largely by a desire for new revenue streams by telecommunications companies and our individual desire to have access to more and more information, a standardized system of coding and transporting information transparently and economically from source to destination at data rates sufficient for all types of service in demand, including unforeseen future needs, had become a global objective of various communication governing bodies. ATM was chosen as the most viable method to standardize end-to-end information transport into a single, reliable entity that can accommodate all the needs of the various communication technologies.
Figure 1-4. Varied communications
ATM: Automatic Teller Machine? Another Technological Melon? Another Telecom Mess? How about: Another Telecom Method? The last choice is close.
Actually, it is an acronym for Asynchronous Transmission Mode. ATM is a switching and transmission technology that can process and transmit any type of information including data, text, audio, and video at high bit rates with a high degree of accuracy. ATM is the culmination of all the developments in switching and transmission technology in the last 20 years. This includes frame relay and packet switching and the change from coaxial to optical fiber transmission mediums.
Many types of information services and information transport are present in the various communication networks around the world. Information services are becoming woven in the very fabric of our existence. Witness the explosive growth of the Internet. Local area networks (LANs) and wide area networks (WANs) are expanding into metropolitan area networks (MANs) and global area networks (GANs). Video related services such as broadcast, CATV, DBS, videotelephony, and video conferencing are commonly available for business and consumer use. On the horizon we can see multimedia, video-on-demand (VOD), cyber-cinema, virtual theater, and other interesting and useful remote data and video related services. What all of these uses have in common is the need to transport information, or data, transparently through the common-carrier telephone company transmission systems at speeds faster than can presently be achieved economically. Transparency refers to the passage of data with little or no processing through all switching and transmission equipment from source to destination. Source to destination is frequently referred to as end-to-end.
Figure 1-5. ATM and ADSL public switched network
Previous | Table of Contents | Next |