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Broadband Services

Broadband services is defined by ITU-T (formerly the CCITT) as “a service requiring transmission channels capable of supporting rates greater than 1.5 Mbps or primary rate in ISDN, T1, or DS-1 in digital technology.” Bandwidth is related to data rates. The higher the data rate, the more bandwidth that is needed.

Analog voice traffic, the historical (legacy) method of communicating over telephone network systems, gave way to digital data traffic with the advent of computers. With the proliferation of the home personal computer, the demand for high-speed data services has become a roar. In addition, the demand for multimedia and video services adds to the cacophony of calls for faster data rates. To support the demand for the high-speed data services, bandwidth must be increased. ATM provides for an increased bandwidth compatible with all types of service. Additionally, ADSL provides the ability to use the increased bandwidth over the readily available copper wires present in the vast majority of homes and businesses.

ISDN has long been considered the medium for transmitting high-speed digital data. With a current transmission rate of 64 Kbps or 128 Kbps, ISDN can hardly be considered broadband, or high speed. Since ATM provides the encoding method to expand ISDN bandwidth, two types of ISDN must now be distinguished. N-ISDN refers to the Narrowband Integrated Services Digital Network of 64/128 Kbps transmission speeds, and B-ISDN refers to the Broadband Integrated Services Digital Network of 1.5 Mbps transmission speed or greater.

Terms and Definitions

One must learn the language of the trade if one hopes to have any chance of understanding what goes on. When the number of terms in any particular field is small, many people can understand the terms and therefore understand the field. However, when a particular field has many terms, few people, relatively speaking, will learn and understand the language, therefore impeding their ability to grasp all the technicalities of the field. Modern communications is full of terms, old and new. A presentation of the full communications vocabulary is outside the scope of this book. There are several good communications/telecom dictionaries available.

When a field, such as telecommunications, uses terms that are used by other fields, some confusion is sure to creep into the picture. Terms used in this book are defined in context of their usage in the field of communications, particularly as they apply to ATM and ADSL.

Data and information are used interchangeably throughout the text just as they are used interchangeably in the industry. Service provider is also known as a carrier and long-haul carrier. The service providers backbone refers to the service providers network which is available for users to connect into, usually for a fee.

Communications, networks, and systems are terms that are used loosely to describe seemingly innumerable, and usually unrelated, ideas and objects. Communications may describe any one of various methods for the transport of information from source to destination. There is RF communications which encompasses the field of radio wave propagation, telecommunications which encompasses the field of communications via the Public Switched Telephone Network (PSTN), data communications which encompasses the art of transporting information using computer (originally) technology, and optical communications which concerns the usage of light wave technology for the purpose of transporting information. There are other communications technologies that are used today and there will most likely be more in the future.

Networks refers to the connection of equipment, usually computers, to allow the users to exchange information. There can be a network of computers, a network of communication switches, or a combination of switches and computers. Network really refers to any loose association of multiple quantities of anything electronic.

Fields overlap, terms are born and die continuously, and the industry water can get real muddy. But this book uses all terms in a straightforward manner that is understandable in the context used.

And the Winner Is

Our communication systems evolved over the years as a function of the technology available at the time. We designed and built switching and transport systems capable of meeting the immediate needs of a growing populace. Yet, throughout all the networks and transmission systems and interconnected mediums, there was not a single standard governing all types of communications. The result is a hodgepodge of incompatible technologies including management, encoding, switching, and transmission technologies that are targeted for very specific communication services. Figure 1-8 details the evolution of primary information systems from early childhood to adulthood. Notice that all information systems, in their dotage, converge on ATM and ADSL. ATM is the technology that will combine all the various systems into a seamless network of high-speed data communications that truly removes the speed limit from the information superhighway. And ADSL is the transport technology to get the information superhighway to your home or business.

The telecommunications industry is quickly converging now on ATM. Five major U.S. telecom companies have ATM networks in place that can provide some degree of access from virtually any location in the continental United States. Additionally, service providers in other countries have ATM networks already providing limited service to Canada, Europe, and Asia.

ADSL technology is not as advanced as ATM. By way of comparison, you could say both technologies are still in their infancy. ATM is just beginning to take tentative steps in the progression from crawling to walking and is by no means potty trained, while ADSL is just a newborn, still in the hospital nursery, waiting to come home to loving (we hope) parents.

Summary

Communication is necessary for us to survive in an inhospitable world. Without communication, the evolution of humankind might have stopped near the same branch of the family tree occupied by chimpanzees. Because we developed more complex communication methods, we rose higher on the family tree.

Communication requires a transmission system, such as a drum, to get the intelligent information from one place to another (source to destination). Communication also requires the encoding, such as a specific pattern of drumbeats, of information by the source for transmission to the destination. And the destination must reliably decode the information received.

Any new communication technology that dramatically leaps ahead of all the previous technologies and is accepted for general use by the populace always results in interesting and dramatic changes to the way we live, play, and conduct business. Examples are the advent of the telegraph and, of course, the ever-so-humble telephone set. The telegraphs nearest competitor when it was invented was the printing press and the nearest competitor to the telephone was the telegraph. Each succeeding communication technology resulted in dramatic and fundamental changes to how we live and to us. Now, ATM and ADSL will offer unprecedented access to virtually all the worlds information and to virtually all the worlds inhabitants. ATM and ADSL enable global unification of the human tribe. Imagine the world tomorrow.


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