WiMAX Network Discovery and Selection

Description

WiMAX Network Discovery and Selection (WNDS) is a functionality specified in 3GPP TS 24.312 that provides User Equipment (UE) with the information required to discover and connect to WiMAX networks, which are standardized as a type of trusted non-3GPP access network. The mechanism operates by delivering WiMAX-specific network discovery information (NDI) and network selection policies to the UE from the 3GPP Evolved Packet Core (EPC). This information is typically provisioned in the UE via the Access Network Discovery and Selection Function (ANDSF), which is part of the EPC's network architecture for managing inter-system mobility and access network selection.

The WNDS information includes technical parameters necessary for the UE to identify and authenticate with a WiMAX network. Key data elements may include Network Access Identifier (NAI) realms, WiMAX network identifiers (e.g., NAP-ID, NSP-ID), roaming consortium identifiers, and the associated trusted non-3GPP access gateway (e.g., ePDG or TWAG) information for establishing an IPsec tunnel or direct connectivity. The UE uses this information to scan for available WiMAX networks, match the discovered networks against the provisioned profiles, and determine the preferred network for connection based on operator-defined policies (e.g., 'connect to WiMAX if available and home network').

Architecturally, WNDS relies on the ANDSF, which communicates with the UE over an S14 reference point (for LTE) or via IP-based communication when the UE is connected via any IP access. The ANDSF can provide management objects (MOs) containing discovery information and intersystem mobility policies (ISMP) or intersystem routing policies (ISRP). For WiMAX, specific WiMAX management objects are defined within the ANDSF framework. The role of WNDS was particularly important during the early phases of LTE deployment when WiMAX was considered a viable complementary broadband wireless access technology for data offloading or service continuity, especially in markets where WiMAX networks were deployed. It enabled a unified policy framework for multi-access network selection within the 3GPP EPC architecture.

Purpose & Motivation

WNDS was created to address the specific need for integrating Worldwide Interoperability for Microwave Access (WiMAX) networks—based on IEEE 802.16 standards—into the 3GPP Evolved Packet Core (EPC) architecture defined around Release 8. At that time, WiMAX was a competing 4G technology deployed in several regions, and there was industry interest in enabling dual-mode LTE/WiMAX devices and seamless service continuity between these heterogeneous radio access technologies. The problem was that UEs needed a standardized method to efficiently discover available WiMAX networks and understand operator policies for when to select them, without relying solely on manual configuration or non-standard mechanisms.

The motivation stemmed from 3GPP's broader work on access network agnosticism in the SAE/EPC, which aimed to support trusted and untrusted non-3GPP accesses. While general mechanisms for non-3GPP access (like ePDG) were defined, WiMAX had specific network identifiers and authentication procedures that differed from, for example, generic WLAN. WNDS provided the missing piece: a standardized container within the ANDSF framework to deliver WiMAX-specific discovery parameters and selection rules to the UE. This solved the problem of how an LTE-capable UE could autonomously find and connect to a WiMAX network as per the operator's policy, enabling scenarios like offloading data traffic to WiMAX or using WiMAX for coverage extension, thereby facilitating the convergence of 3GPP and non-3GPP networks under a common core and policy framework.

Key Features

• Delivers WiMAX network discovery information (NDI) to the UE via ANDSF
• Includes WiMAX-specific identifiers: NAP-ID, NSP-ID, roaming consortium IDs
• Provides operator policies for WiMAX network selection and prioritization
• Uses standardized ANDSF management objects (MOs) over S14 or IP-based interfaces
• Enables automated discovery and attachment to trusted WiMAX access networks
• Supports intersystem mobility between 3GPP LTE and WiMAX networks

Evolution Across Releases

Defining Specifications