GSM offers a wide range of services, including telephony, emergency calling, data up to 14.4 Kb/s, fax up to 9.6 Kb/s, SMS, and others. In addition, it also offers a rich set of supplementary services. According to ITU specifications, the telecommunication services are categorized into three different types, i.e., bearer services, teleservices, and supplementary services.
Bearer services are telecommunication services providing the capability of transmission medium between access points. These services are characterized by a set of low layer attributes.
Teleservices are telecommunication services providing complete capability, including terminal equipment functions. Teleservices are characterized by a set of low layer attributes, a set of high layer attributes, and operational and commercial attributes.
A supplementary service modifies or supplements a basic telecommunication service. It is offered together with or in association with a basic telecommunication service.
The following sections list the bearer services, teleservices, and supplementary services offered by GSM.
Bearer service
■ Asynchronous data
■ Synchronous data
■ Asynchronous PAD (packet switched, packet assembler/disassembler)
■ HSCSD—asymmetric
■ HSCSD—symmetric
Teleservices
■ Telephony (speech)
■ Emergency calls (speech)
■ Short message services
■ Alternate speech and Group 3 fax
■ Automatic Group 3 fax
Supplementary services
■ Call forwarding
■ Call barring
■ Calling/connected line identity presentation (CLIP)
■ Calling/connected line identity restriction (CLIR)
■ Call waiting (CW)
■ Call hold (CH)
■ Multiparty communication—closed user group (CUG)
■ Advice of charge (AoC)
■ Unstructured supplementary service data (USSD)
■ Operator-determined barring (ODB)
