19-09-2012, 01:00 PM
INTRODUCTION TO ISDN, ATM AND BROADBAND TRANSMISSION
[attachment=34051]
Introduction
This Information Factory course "Introduction to ISDN, ATM and Broadband
Transmission" is a continuation of our earlier course "Introduction to Digital
Transmission." In the first course we described how the world's telephone
networks were moving from their analog transmission methods onto a completely
digital transmission network. In this training course we are going to describe how
the telephone networks are extending the digital interfaces into the customer's
homes and offices under a new service called "Integrated Services Digital
Network" or ISDN.
We will begin here in Section 1 by describing how the existing telephone network
has been changing from an analog network into an all digital network. It is
necessary to look first at the existing network and its changes in order to
understand how they form the basis for the future ISDN and eventually the
Broadband or B-ISDN network.
Telephone Systems and Networks
The modern ISDN networks are being built on the existing telephone networks
worldwide and as a result many of the views of the network and many of its
principles are based on the same ideas. As an example, when you picked up a
telephone and dialed a call, the call was connected through a series of relays or
"stepper switches" as shown in Figure 1.1 (below).
Notice that the process of making a telephone call involves more than just talking.
The caller takes the phone off-hook, dials the call, listens to the ringing and finally
talks when the far end phone is answered.
In the original mechanical telephone systems as shown in Figure 1.1 (above), all
of the work of setting up the call was handled by the same relays that transmitted
the voice. This meant when you picked up the phone and dialed a call, the
stepper switches were being tied up as each digit was entered.
Digital Transmission
The use of digital transmission systems began in the United States in about 1963
when the telephone companies installed a system called T1. The original use for
T1 had been to replace the old analog transmission systems that connected the
central offices.
As shown in Figure 1.6 the links between central offices had been based on an
analog carrier system called "L-Carrier." This system multiplexed several voice
channels using Frequency Division Multiplexing techniques.
Digital Switching
The next step for the telephone companies was to replace their analog switching
systems with all digital switching systems. This meant the voice could be carried
through the network in digital form eliminating the need for conversion at each
switching and transmission point.
In the mechanical switching systems, a relay or stepper switch was used to make
the physical connections through the network. In effect there was a wire path
from one telephone to another (refer back to Figure 1.1).
ISDN The Next Generation
The next step would be to convert the links into your home or office into digital
transmission. The telephone companies have been at work on this conversion to
digital under a set of standards called "Integrated Services Digital Network" or
"ISDN."
As the names implies, this is not just a telephone network but, a network of
"Integrated Services" that will provide access to a full range of digital
communication for voice, video, multimedia and data communications. In fact the
telephone company can be thought of as a "digital company."
What we will show in the balance of this course is how ISDN will provide a
connection that allows the customer to access the network digitally. Also the
ISDN network will extend a part of the telephone company signaling system into
the customer's premises to allow them a new level of control over incoming and
outgoing calls.
[attachment=34051]
Introduction
This Information Factory course "Introduction to ISDN, ATM and Broadband
Transmission" is a continuation of our earlier course "Introduction to Digital
Transmission." In the first course we described how the world's telephone
networks were moving from their analog transmission methods onto a completely
digital transmission network. In this training course we are going to describe how
the telephone networks are extending the digital interfaces into the customer's
homes and offices under a new service called "Integrated Services Digital
Network" or ISDN.
We will begin here in Section 1 by describing how the existing telephone network
has been changing from an analog network into an all digital network. It is
necessary to look first at the existing network and its changes in order to
understand how they form the basis for the future ISDN and eventually the
Broadband or B-ISDN network.
Telephone Systems and Networks
The modern ISDN networks are being built on the existing telephone networks
worldwide and as a result many of the views of the network and many of its
principles are based on the same ideas. As an example, when you picked up a
telephone and dialed a call, the call was connected through a series of relays or
"stepper switches" as shown in Figure 1.1 (below).
Notice that the process of making a telephone call involves more than just talking.
The caller takes the phone off-hook, dials the call, listens to the ringing and finally
talks when the far end phone is answered.
In the original mechanical telephone systems as shown in Figure 1.1 (above), all
of the work of setting up the call was handled by the same relays that transmitted
the voice. This meant when you picked up the phone and dialed a call, the
stepper switches were being tied up as each digit was entered.
Digital Transmission
The use of digital transmission systems began in the United States in about 1963
when the telephone companies installed a system called T1. The original use for
T1 had been to replace the old analog transmission systems that connected the
central offices.
As shown in Figure 1.6 the links between central offices had been based on an
analog carrier system called "L-Carrier." This system multiplexed several voice
channels using Frequency Division Multiplexing techniques.
Digital Switching
The next step for the telephone companies was to replace their analog switching
systems with all digital switching systems. This meant the voice could be carried
through the network in digital form eliminating the need for conversion at each
switching and transmission point.
In the mechanical switching systems, a relay or stepper switch was used to make
the physical connections through the network. In effect there was a wire path
from one telephone to another (refer back to Figure 1.1).
ISDN The Next Generation
The next step would be to convert the links into your home or office into digital
transmission. The telephone companies have been at work on this conversion to
digital under a set of standards called "Integrated Services Digital Network" or
"ISDN."
As the names implies, this is not just a telephone network but, a network of
"Integrated Services" that will provide access to a full range of digital
communication for voice, video, multimedia and data communications. In fact the
telephone company can be thought of as a "digital company."
What we will show in the balance of this course is how ISDN will provide a
connection that allows the customer to access the network digitally. Also the
ISDN network will extend a part of the telephone company signaling system into
the customer's premises to allow them a new level of control over incoming and
outgoing calls.