Multi-iDentity

Description

Multi-iDentity (MID) is a 3GPP concept that enables a single piece of user equipment (UE), identified by a single International Mobile Equipment Identity (IMEI), to host multiple distinct subscriber identities. Each identity is typically represented by a unique International Mobile Subscriber Identity (IMSI) and associated subscription profile stored on a UICC (Universal Integrated Circuit Card) or in the network. The UE and network use the MID capability to manage these separate identities, allowing the user to register, obtain services, and be billed independently for each identity. Architecturally, MID is supported in both the UE and core network elements like the Home Subscriber Server (HSS) in EPS or the Unified Data Management (UDM) in 5GS, which store the subscription data for each identity.

How it works involves the UE indicating its multi-identity capability during registration procedures, such as Attach or Registration Request. The network authenticates each identity separately using its respective credentials. The UE can then activate different 'personas' or service profiles associated with each identity. For example, one identity might be for personal use with a standard data plan, while another could be a corporate identity with access to a private network slice and specific QoS policies. The network treats traffic from each identity independently for policy enforcement, charging, and lawful interception purposes. The UE's operating system or modem software manages the context switching between these identities, which may be presented to the user as separate phone numbers or service profiles.

Its role in the network is to provide flexibility and efficiency for both users and operators. It allows for the consolidation of devices (e.g., carrying one phone for both personal and work life) while maintaining strict separation of services, security policies, and billing. MID is foundational for features like multiple MSISDNs (phone numbers) on a single SIM (MSISDN-less MO SMS), and it interacts with mechanisms for steering different identities to different network slices in 5G. It is a key enabler for machine-to-machine (M2M) scenarios where a single IoT device might need separate identities for different applications or tenants, all hosted on the same hardware.

Purpose & Motivation

MID was introduced to solve the growing need for a single mobile device to support multiple, logically separate subscriber profiles. Before its standardization, users who wanted distinct personal and business lines typically had to carry two separate phones or use a single device with a dual-SIM tray (a hardware solution). The purpose of MID is to provide a standardized, network-centric software mechanism to achieve this separation, offering greater flexibility for device design, subscription management, and service innovation. It addresses the limitations of hardware-based solutions by allowing dynamic management of identities through the network.

The creation of MID was motivated by several use cases: business users requiring separate billing and policies for corporate and personal use, IoT devices serving multiple applications or customers from one module, and the desire for service providers to offer 'family' or 'secondary' numbers on a primary subscription. It also supports regulatory requirements for distinct identities. By standardizing MID, 3GPP enabled operators to offer sophisticated multi-persona services, manage resources more efficiently, and pave the way for future concepts like network slicing, where different identities on the same device could be mapped to different slices with tailored characteristics.