Calling subscriber

Description

The term "Calling subscriber" has evolved in meaning across 3GPP releases. In Release 4, it was defined in TS 22.067, 22.068, and 22.069 as the "Service subscriber or dispatcher which originates the VGCS call." This definition was specific to Voice Group Call Service (VGCS), identifying the entity that initiates a group call. However, starting with Release 5, the definition was changed to "Service subscriber which invokes the eMLPP service." This shift reflects a broader application of the term to the enhanced Multi-Level Precedence and Pre-emption (eMLPP) service, which provides priority handling for calls.

In the context of eMLPP, the calling subscriber is the user who initiates a call with a specific priority level. The eMLPP service allows subscribers to be assigned priority levels (e.g., A, B, 0-4) that determine the precedence of their calls and whether they can pre-empt lower-priority calls. The calling subscriber invokes the eMLPP service by dialing a specific prefix or by having a default priority level assigned in their subscription. The network then uses this priority information to handle the call appropriately, potentially pre-empting other calls or queuing the call if resources are unavailable.

The calling subscriber role is crucial for the operation of eMLPP. When a calling subscriber initiates a call, the network checks their priority level and the priority level of the called party. If the calling subscriber has a higher priority, the call may be given precedence over other calls, and if necessary, pre-emption of lower-priority calls may occur. The calling subscriber may also be subject to pre-emption if a higher-priority call is made to them, as described in the called-party pre-emption feature.

The term is used in specifications related to eMLPP and VGCS. In VGCS, the calling subscriber is the originator of the group call, while in eMLPP, it is the originator of a priority call. The change in definition from Release 4 to Release 5 indicates a shift from a VGCS-specific term to a more general eMLPP term. This reflects the growing importance of priority services in 3GPP networks and the need for a common terminology.

The calling subscriber concept is implemented in network entities such as the MSC, VLR, and HLR, which store subscription data including priority levels. The Mobile Station (MS) also plays a role by sending the appropriate priority information when initiating a call. The term has remained unchanged from Release 5 through Release 19, indicating stability in the eMLPP service definition.

Purpose & Motivation

The term "Calling subscriber" was originally introduced in Release 4 to identify the originator of a VGCS call, distinguishing them from other participants. However, as priority services like eMLPP became more prominent, the definition was revised in Release 5 to focus on the eMLPP service. This change reflects the need for a term that describes the user who invokes priority handling, which is essential for ensuring that high-priority communications can be established and maintained during network congestion or emergencies.

The purpose of defining the calling subscriber in the context of eMLPP is to provide a clear identification of the entity that requests priority treatment. This is important for authorization, charging, and call control. The network must know who the calling subscriber is to apply the correct priority level and to enforce pre-emption policies. The term also helps in describing the interactions between the calling subscriber, the network, and the called party.

Historically, the term evolved from a VGCS-specific definition to a broader eMLPP definition, reflecting the increasing importance of priority services in 3GPP networks. The change in Release 5 was a wording change that aligned the term with the eMLPP service, which had been introduced earlier but was gaining more attention. This evolution shows how 3GPP terminology adapts to the changing focus of network services.