Intelligent Networks: Principles and Applications
This book explains how intelligence can be introduced into digital telephone networks.
TABLE OF CONTENTS Intelligent Networks: Principles and Applications
Chapter 3: Signalling Intelligence
The wireless music box has no imaginable commercial value. Who would pay for a message sent to nobody in particular?
David Sarnoff s associates, in response to his urgings for investment in the radio in the 1920s.
3.1 Introduction
Whilst this book is primarily about IN we have to remember that IN was introduced into the context of existing voice networks, which already exhibit a fair degree of intelligence , both in terms of embedded switch-based services and the common-channel signalling system and the associated call control procedures. Furthermore, without some of these intelligence features already installed in voice networks, the IN enhancements would actually not have been possible.
In order to underpin the discussion on the incremental intelligence features provided by IN we now review the common-channel signalling system and the traditional call processing procedures.
3.2 Common channel signalling the beginning
The introduction of common channel signalling, i.e. the CCITT Signalling System No.7 (SS7), was revolutionary. Until then signalling systems were mainly in-band and line-based, using make-and-breaks on the transmission path, or various combinations of tones on the speech path [15].
Implementations of SS7 started to appear in the early 1980s, along with SPC (stored program control) digital telephone exchanges [16, 17]. The new common channel signalling enabled the switch processors to communicate directly, sending call set-up information between each other using labelled messages. The advent of SS7 allowed the signalling to be removed completely from the speech path, to the enormous benefit of both. Speech circuits could be provided...
Copyright The Institution of Electrical Engineers 2002 under license agreement with Books24x7
