Local Home Network Identifier

Description

The Local Home Network Identifier (LHN ID) is a network identifier used within the 3GPP Radio Access Network (RAN) architecture, particularly in the context of small cells deployed in homes or enterprises (HeNBs, HNGs). It serves as a unique label for a specific Local Home Network, which is a logical grouping of one or more Home eNodeBs (HeNBs) or Home gNBs that belong to the same administrative domain, such as a particular enterprise campus, a residential subscriber's network, or a neutral host infrastructure.

Technically, the LHN ID is configured in the Home eNodeB/gNB and is communicated to the core network (MME/AMF) and neighboring macro cells during network interface establishment and handover procedures. It is carried in RAN Application Part (RANAP) and X2 Application Protocol (X2AP) messages. The primary function of the LHN ID is to enable the RAN and core network to identify the 'home' network of a UE when it is connected via a small cell. This identification is crucial for several operational procedures.

For mobility management, the LHN ID allows the network to optimize handovers. For example, a handover between two HeNBs sharing the same LHN ID can be treated as an 'intra-LHN' handover, potentially using simplified procedures compared to a handover to a cell in a different LHN or the macro network. For access control and policy, the core network can use the LHN ID to verify if a UE is authorized to access that specific local network. Furthermore, it enables the application of network-specific policies, such as dedicated charging rules or allowed services, based on the local network context. In scenarios like Closed Subscriber Group (CSG) cells or hybrid access cells, the LHN ID helps manage the hybrid membership and resource partitioning between home network subscribers and visiting macro users.

Purpose & Motivation

The LHN ID was introduced to solve the management and operational complexities arising from the large-scale deployment of consumer and enterprise small cells (femtocells). Early femtocell deployments lacked a standardized way for the macro network to logically group and identify clusters of these cells belonging to the same owner or location. This made efficient mobility management, coordinated radio resource management, and application of localized policies difficult.

Its creation was motivated by the need for enhanced RAN support for Local IP Access (LIPA) and Selected IP Traffic Offload (SIPTO) at the local network. To efficiently route traffic and manage mobility for UEs accessing local services, the network required a clear identifier for the local domain. The LHN ID provided this, enabling features like SIPTO continuity during mobility within the same local network. It addressed the limitation of treating every HeNB as an isolated entity, allowing operators to manage groups of small cells as a cohesive local network for operational and service delivery purposes, improving both network efficiency and the user experience for localized services.