Enhanced Dialled Services

Description

Enhanced Dialled Services (EDS) is a standardized set of capabilities defined within the 3GPP Core Network, specifically in the Circuit-Switched (CS) domain. It operates as an enhancement to the traditional dialing and call control mechanisms, governed by protocols in the Core Network. Architecturally, EDS functionalities are implemented within network entities like the Mobile Switching Center (MSC) and the Home Location Register (HLR), interacting with the User Equipment (UE) through signaling protocols. The service logic for EDS is defined in the CAMEL (Customised Applications for Mobile network Enhanced Logic) framework or as native MSC/HLR features, allowing for the execution of complex service scripts triggered by specific dialing patterns or subscriber profiles.

How EDS works involves the interception and analysis of a dialed number or service code by the network. When a user initiates a call or a supplementary service activation, the MSC examines the dialed digits against a set of predefined rules and subscriber data from the HLR. If a match is found for an EDS feature, the MSC invokes the corresponding service logic. This logic can modify the call handling procedure—for instance, by redirecting the call to a different number based on time-of-day, applying specific charging rates, or presenting enhanced calling line identity information to the called party. The execution is transparent to the end-user, who simply experiences the enhanced service outcome.

The key components enabling EDS include the service control logic, the subscriber database (HLR), and the call session control function within the MSC. The specifications, primarily 3GPP TS 23.078 and TS 29.078, detail the signaling flows and information elements required between these network nodes to support EDS. Its role is to enrich the basic telephony service palette, providing a standardized way for operators to deploy consistent, advanced call features across their networks, thereby moving beyond simple voice connectivity to intelligent call management.

Purpose & Motivation

EDS was created to address the growing market demand for more intelligent and flexible telephony services beyond plain voice calls. Prior to its standardization, supplementary services were often basic, proprietary, or limited in scope, leading to interoperability issues and a slow pace of innovation. The limitations of previous approaches included a lack of network-based intelligence for conditional call handling and an inability to easily create customized services for different subscriber segments.

The historical context lies in the evolution from 2G GSM networks to 3G UMTS, where operators sought to increase Average Revenue Per User (ARPU) by introducing value-added services. EDS, introduced in Release 6, provided a framework within the core network to implement these services in a standardized manner. It solved the problem of service silos by defining a common set of enhanced dialing procedures and service logic execution, enabling features like multi-leg calling, advanced call barring, and personalized call routing based on complex criteria.

Ultimately, EDS motivated the creation of a more service-aware core network, allowing operators to compete on service differentiation rather than just coverage or price. It laid groundwork for the convergence of telephony with intelligent network (IN) concepts, ensuring that mobile networks could offer a service richness comparable to or exceeding that of fixed-line networks at the time.

Key Features

• Conditional call forwarding based on subscriber-defined rules
• Enhanced Calling Line Identification Presentation (CLIP) and Restriction (CLIR)
• Network-based call screening and barring with multiple criteria
• Support for specialized dialing codes and service triggers
• Integration with CAMEL for customized application logic
• Standardized signaling between MSC, HLR, and other core nodes for service execution

Evolution Across Releases

Defining Specifications