Legacy Technology: Channelized TDM Transmission Systems

Legacy Technologies: Channelized TDM Transmission Systems

From about 1960 to 2000, the telecom network was constructed of high-capacity transmission systems shared amongst users by employing Channelized Time-Division Multiplexing (TDM), also known as Synchronous Time-Division Multiplexing.


These systems are now referred to as legacy systems, meaning left over from a previous era... but that does not mean they have disappeared. Telephone companies tend to keep existing systems running for as long as possible.


In this module, you'll learn the channelized DS0-DS1-DS3 digital hierarchy, and technologies like T1 and SONET that implement it.


We'll review how traffic from many different circuits is organized to be communicated together 8,000 times per second in transmission frames.


The module is completed with an overview of the now-almost-completely-obsolete ISDN services.


Telecom Module 17

Detailed Outline

17 Legacy Technology: Channelized TDM Transmission Systems

17.1 The Digital Hierarchy: Legacy Channelized Transmission Speeds

...... 17.1.1 Kilo, Mega, Giga, Tera

...... 17.1.2 DS0

...... 17.1.3 DS1 and E1

...... 17.1.4 DS2

...... 17.1.5 DS3

...... 17.1.6 STM and SDH

17.2 Digital Carrier Systems: Legacy Transmission Technologies

...... 17.2.1 Technologies

...... 17.2.2 Carrier Systems

...... 17.2.3 T1

...... 17.2.4 T3 and Bit-Interleaved Multiplexing

...... 17.2.5 SONET and Byte-Interleaved Multiplexing

...... 17.2.6 SDH

...... 17.2.7 Line Speed vs. Technology

17.3 Framing

...... 17.3.1 Synchronous Time-Division Multiplexing

...... 17.3.2 Framing and Transmission Frames

...... 17.3.3 DS1 Frame

...... 17.3.4 STS-1 (DS3) Frames

...... 17.3.5 SONET Optical Carrier Frames

...... 17.3.6 Advantages and Disadvantages of Channels

17.4 ISDN

...... 17.4.1 Basic Rate Interface (BRI)

...... 17.4.2 Obsolescence of BRI

...... 17.4.3 Primary Rate Interface (PRI)

...... 17.4.4 PRI Physical Connection

...... 17.4.5 T1 vs. PRI