Normal mode of operation

Description

The Normal mode of operation is a concept defined in 3GPP specifications 21.905 and 22.022, primarily related to the personalisation of Mobile Equipment (ME). Personalisation refers to the process of configuring a mobile device to operate only with specific SIM cards, networks, or services, often imposed by the manufacturer, network operator, or service provider. The Normal mode of operation is the state the ME would enter if no such personalisation checks were present or if all personalisation checks were successfully passed. In essence, it is the device's default operational state, where it can fully access all its intended functionalities without restrictions.

In the context of 3GPP TS 22.022, which specifies personalisation requirements, the ME undergoes a series of checks during startup or when a SIM is inserted. These checks determine whether the device is allowed to operate with the inserted SIM or within a particular network. If the ME is personalised, it may restrict operation to a specific SIM, network, or service group. The Normal mode of operation is the hypothetical mode the ME would assume if these checks were not present. This concept is crucial for defining the expected behavior of the ME when personalisation is not a factor, providing a baseline for testing and compliance.

The Normal mode of operation is not a physical mode but a logical state. It encompasses all the standard functions of the ME, such as registering with the network, establishing calls, and using data services, without any additional restrictions imposed by personalisation. When personalisation checks are present, the ME may enter a restricted mode if the checks fail, limiting its capabilities. The Normal mode is thus the reference state for the ME's full functionality.

From an implementation perspective, the ME's software includes personalisation checks that are executed at specific triggers, such as power-on or SIM insertion. These checks compare the SIM's identity and other parameters against the personalisation settings stored in the ME. If the checks pass, the ME proceeds to the Normal mode of operation. If they fail, the ME may enter a limited service state or display an error. The Normal mode is therefore the target state when personalisation is either absent or satisfied.

The concept has been stable across 3GPP releases from Rel-4 to Rel-19, indicating its fundamental nature in the personalisation framework. It is referenced in specifications related to personalisation (22.022) and vocabulary (21.905). Understanding the Normal mode of operation is essential for engineers working on device personalisation, as it defines the expected behavior and provides a benchmark for testing personalisation features.

Purpose & Motivation

The Normal mode of operation exists to provide a clear reference point for the behavior of a Mobile Equipment (ME) when personalisation constraints are not applied. Personalisation was introduced to allow manufacturers and operators to subsidize devices or enforce service agreements by locking devices to specific SIMs or networks. However, to define the device's behavior in the absence of such restrictions, the concept of Normal mode was created. It solves the problem of ambiguity in specifying how an ME should behave when no personalisation checks are present or when they are all satisfied. Without this concept, it would be difficult to distinguish between the device's inherent capabilities and those restricted by personalisation.

Historically, as mobile devices became more widespread and subsidized by operators, personalisation became a common practice. 3GPP needed to standardize the personalisation process to ensure interoperability and consistent user experience. The Normal mode of operation was defined to establish the baseline behavior, ensuring that devices from different manufacturers behave similarly when unrestricted. It also aids in testing and certification, as test cases can verify that a device enters Normal mode when appropriate.

The concept addresses the limitation of previous approaches where the behavior of unrestricted devices was not formally defined, leading to potential inconsistencies. By specifying the Normal mode, 3GPP ensures that all compliant devices have a well-defined default state, which is essential for network operations and user expectations.