GSM - Architecture, Protocols and Services, Third Edition

Chapter 7. Services

In this section we summarize and describe the most important services provided in GSM systems.

Classical GSM services

Teleservices

Voice

Voice services had to be implemented by each operator in the start-up phase (E1) by 1991. In this category, two teleservices were distinguished: regular telephone service (TS11) and emergency service (TS12). For the transmission of the digitally coded speech signals, both services use a bidirectional, symmetric, full-duplex, point-to-point connection, which is set up on user demand. The sole difference between TS11 and TS12 teleservices is that regular service requires an international IWF, whereas the emergency service stays within the boundaries of a national network.

Fax transmission

As a teleservice for the second implementation phase (E2), the implementation of a transparent fax service (TS61) for Group 3 fax was planned. The fax service is called transparent because it uses a transparent bearer service for the transmission of fax data. The coding and transmission of the facsimile data uses the fax protocol according to the ITU-T recommendation T30. The network operator also has the option to implement TS61 on a nontransparent bearer service in order to improve the transmission quality. TS61 is transmitted over a traffic channel that is alternately used for voice or fax. Another optional alternative is designated as a fax transfer with automatic call acceptance (TS61). This service can be offered by a network operator when multinumbering ...