Local Home Network Identifier

Description

The Local Home Network Identifier (LHN-ID) is a parameter defined within 3GPP core network protocols, specifically in the Non-Access Stratum (NAS) layer. It serves as a unique label for a local home network, which is typically a small-scale network such as a residential, enterprise, or campus deployment utilizing technologies like Home NodeBs (HNB) or Home eNodeBs (HeNB). The LHN-ID is carried within NAS signaling messages, such as those specified in TS 24.008 for GSM/UMTS and TS 24.301 for EPS, allowing the core network to identify the specific local network to which a User Equipment (UE) is attempting to connect or is currently registered.

Architecturally, the LHN-ID is associated with the concept of Closed Subscriber Groups (CSG) and hybrid access modes. When a HeNB/HNB broadcasts a CSG Identity, it may also be configured with an LHN-ID. This identifier is reported by the UE to the Mobility Management Entity (MME) in EPS or the Serving GPRS Support Node (SGSN) in UMTS/GPRS during attachment, tracking area update, or service request procedures. The core network node uses this identifier, in conjunction with subscriber data from the Home Subscriber Server (HSS), to enforce access control policies specific to that local network. For instance, it can determine if the UE is allowed to access that particular HeNB/HNB and what services or charging rules are applicable within that local domain.

Its role extends beyond simple identification; it enables network operators to offer localized services and differentiated charging. By recognizing the LHN-ID, the core network can apply specific APN configurations, QoS policies, or even route traffic to a local gateway (e.g., Local Gateway (L-GW) or HeNB Gateway) that provides direct internet breakout or access to local IP resources within the home/enterprise network. This mechanism is fundamental for the 3GPP architecture supporting femtocells and small cells, ensuring that devices can seamlessly access both wide-area macro network services and localized services while maintaining appropriate security and policy enforcement.

Purpose & Motivation

The LHN-ID was introduced to address the growing deployment of femtocells and small cells in 3GPP networks, particularly with the standardization of Home eNodeBs (HeNBs) in Release 9. Prior to its introduction, network identification for access control and service localization was primarily based on the Cell Global Identity (CGI) or Tracking Area Identity (TAI), which are tied to the radio cell's location but not necessarily to a logical, subscriber-specific local network domain. This was insufficient for residential or enterprise deployments where multiple small cells might belong to the same logical 'home' network, requiring a common identifier for consistent policy application.

The primary problem it solves is the need for a network operator to identify and manage a group of small cells as a single logical entity for a subscriber or a set of subscribers. For example, in a household with multiple HeNBs, the operator needs to treat them as part of the same 'home network' for services like unified billing, access to a shared local IP network (e.g., printers, NAS), and consistent access control. The LHN-ID provides this logical grouping identifier, decoupled from the physical cell identity. It enables the core network to apply subscriber-specific policies that are relevant to the local network context, such as allowing access only to members of a Closed Subscriber Group (CSG) associated with that LHN-ID or applying special charging rates for calls/data within the home network.

Historically, its creation was motivated by the 3GPP work on enhanced support for HeNBs in Release 12, focusing on mobility and service continuity between the macro network and HeNB subsystems. The LHN-ID became a key enabler for features like CSG mobility, where a UE moving between HeNBs belonging to the same local home network could experience seamless handovers and consistent service treatment without needing re-authentication or policy re-evaluation by the core network for each cell change. It filled a gap in the network's ability to understand the logical topology of small cell deployments, which is essential for efficient network management and enhanced user experience in heterogeneous networks.