ETSI TS 123 011 describes the general aspects on how supplementary services in the 3GPP system are realised from a technical point of view.

Description of technical realisation for specific supplementary services can be found in 3GPP TS 23.072, 230.8x and 230.9x-series technical specifications.

All supplementary services may require signalling on the radio path. Signalling procedures and messages used are defined in the 3GPP TS 24.072, 24.08x and 24.09x-series of technical specifications.

For some supplementary services information needs to be transferred between the Home Location Register (HLR), the Visitor Location Register (VLR), the Mobile services Switching Centre (MSC) and the Serving GPRS Support Node (SGSN). Signalling procedures for such information transfer are defined in 3GPP TS 29.002.

Definitions and descriptions of supplementary services are given in the 3GPP TS 22.072, 22.08x and 22.09x-series of technical specifications.

Definitions are given in 3GPP TS 22.004.

NOTE: The technical specifications on the technical realisation of supplementary services do not distinguish between subscriber, user and customer, since all three do not fully cover the textual needs. Generally the term "subscriber" is used, even if this person is not having the subscription.