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GSM Networks: Protocols, Terminology, and Implementation

A word on coding of parameters and messages should be added here: Coding of message types and other essential parameters are always included. However, because this book has no intention of being a copy of the GSM Rec-ommendations, it deliberately refrains from providing a complete list of all parameters of all interfaces.

The yalue of protocol test eąuipment for error analysis and routine testing is indisputably high, but what help do programs for automatic analysis provide? Those ąuestions will be answered as well.

A large part of this book is taken up by a glossary, which provides descrip-tions of all abbreviations, terms, and processes that a reader may confront dur-ing work on GSM.

1.4 Signaling

The main focus of this book is on the signaling between the various network elements of GSM. The ąuestions arise of what signaling actually constitutes and what it is used for. Although we do not want to go back to the basics of telecommunications to answer those ąuestions, a number of basie explanations do seem necessary.

1.4.1    What is Signaling?

Signaling is the language of telecommunications that machines and computers use to communicate with each other. In particular, the signals that a user enters need to be converted to a format that is appropriate for machines and then transmitted to a remote entity. The signals (e.g., the identity of a called party) are not part of the communication as such, that is, they are not a payload or a revenue-earning entity.

Signaling is comparable to the pilots and the flight attendants on an airplane. The crew members are no “payload,” but they are necessary to carry the payload. Another, perhaps morę appropriate, illustration is to consider the now almost extinct telephone operator, whose function it was to carry out the signaling function and switching of a telecommunications system by connect-ing cables between the appropriate incoming and outgoing lines.

1.4.2    How is Signaling Performed?

When calls were set up manually, signaling consisted mostly of direct current impulses, which allowed a central office to determine the dialed digits. Some