Teleservice

Description

A teleservice is defined by 3GPP as a type of telecommunication service that provides the complete capability, including terminal equipment functions, for communication between users according to protocols established by agreement between Administrations. This definition, based on ITU-T Recommendation I.112, distinguishes teleservices from bearer services by emphasizing the complete user-to-user communication capability, which encompasses not only the transport of information but also the terminal functions and protocols necessary for the service.

Teleservices are one of the two broad families of telecommunication services, the other being bearer services. While bearer services provide the transmission capacity and technical means for information transfer, teleservices build upon bearer services to offer a complete communication service. Examples of teleservices include telephony, facsimile, and short message service (SMS). In each case, the teleservice defines the terminal equipment functions, such as voice encoding and decoding for telephony, and the protocols for call setup, maintenance, and release.

Architecturally, teleservices are implemented through a combination of network functions and terminal capabilities. In a PLMN, the core network provides the switching and control functions, while the radio access network provides the wireless connectivity. The terminal equipment, such as a mobile phone, implements the teleservice-specific functions. The protocols used for teleservices are standardized to ensure interoperability between different terminals and networks. For example, the protocols for telephony include the call control procedures and the speech codec specifications.

Teleservices are closely tied to Quality of Service (QoS) requirements. Since they provide complete communication capabilities, they must meet specific performance criteria such as end-to-end delay, speech quality, and reliability. These requirements are mapped to bearer service attributes, which the network uses to allocate resources. The 3GPP specifications define various teleservices and their associated QoS parameters, ensuring that users experience consistent service quality.

The definition of teleservice has remained largely stable across releases, with some wording variations. In Rel-4, the definition mentioned 'standardised protocols and transmission capabilities established by agreement between operators,' while in Rel-5 it was changed to 'protocols established by agreement between Administrations' with a reference to 3GPP TR 21.905 and ITU-T I.112. This change aligned the terminology with ITU-T definitions. In subsequent releases, the wording alternated between these two forms, but the core concept remained unchanged. This stability reflects the fundamental nature of teleservices in telecommunications.

Purpose & Motivation

The concept of a teleservice exists to provide a clear distinction between the transport of information and the complete communication service that users actually experience. It solves the problem of defining services that require specific terminal functions and protocols, beyond mere data transmission. By separating teleservices from bearer services, network designers can independently develop and optimize the transport layer and the service layer, leading to more flexible and efficient networks.

Historically, the term was inherited from the fixed-line telecommunication world, where ITU-T defined teleservices as services that provide complete capability for communication between users. When mobile networks were developed, 3GPP adopted this definition to describe services like telephony and SMS. This allowed for a consistent framework across fixed and mobile networks, facilitating interconnection and roaming. The definition also helped in standardizing terminal equipment, as teleservices specify the functions that terminals must support.

The purpose of teleservices is to ensure that users can communicate effectively regardless of the underlying network technology. They provide a common language for describing services, which is essential for interoperability and for meeting regulatory requirements. For operators, teleservices represent the services they offer to customers, and they must ensure that these services meet the expected quality. The concept continues to be relevant in the era of 5G, where new teleservices such as mission-critical push-to-talk and enhanced voice services are being defined.