Cellular WLAN Integration Architecture Explained

This page describes the architecture for integrating cellular and WLAN (Wireless Local Area Network, often referred to as WiFi) networks and highlights its benefits. It also outlines the key elements of such a network.

Introduction

Cellular technologies (2G, 3G (UMTS), 4G, and 5G NR) are rapidly evolving due to the widespread adoption of mobile phones globally. Simultaneously, WiFi has gained popularity for sharing a single broadband connection among multiple users in homes and offices.

WiFi adheres to WLAN specifications as defined in the IEEE 802.11 series of standards, which cover the PHY (Physical) and MAC (Media Access Control) layers.

Cellular technologies are primarily designed to provide broad coverage and accommodate high user density at varying data rates. In contrast, WiFi is engineered to deliver very high data rates in spatially constrained environments, mainly indoors and over limited outdoor distances.

WiFi supports low mobility, while cellular technologies support high mobility. These technologies are complementary. To capitalize on the advantages of both, operators are exploring integrated solution architectures that incorporate both WiFi and cellular.

From a data services perspective, operators aim to facilitate seamless roaming between WLAN and cellular networks (and vice versa) to encourage the use of dual-mode handsets.

While no single architecture perfectly meets all requirements, various approaches have been explored, including:

• Tightly Coupled Integration Architecture (TCIA)
• Loosely Coupled Integration Architecture (LCIA)
• A combination of TCIA and LCIA
• Internet roaming global architecture

Below, we’ll illustrate a global architecture used to integrate both cellular and WLAN (i.e., WiFi) networks.

Figure-1: UMTS architecture

Cellular WLAN Integration Architecture

One option involves connecting the WLAN at the BSS/RNC (Base Station Subsystem/Radio Network Controller), which requires significant changes to complex radio procedures due to the fundamentally different radio interfaces.

Another option emulates WLAN as BSS/RNC by connecting through the Gb interface at the SGSN (Serving GPRS Support Node). This approach can create network bottlenecks due to the large amount of cellular traffic offloaded to the WLAN.

A further alternative is to connect the WLAN at the GGSN (Gateway GPRS Support Node), simplifying handover from cellular to WLAN but slowing down WLAN-to-cellular handover.

The most favored solution is to interface the WLAN to a separate IP-based network, which then connects to the cellular UMTS network via the Gi interface, as shown in Figure 1.

Figure-2: Cellular WLAN (WiFi) integration architecture

The figure illustrates a global integration architecture of UMTS (as a cellular technology) with WLAN. A dedicated server, known as a Certificate Authority Server (CA Server), is deployed to verify the authenticity of fixed nodes and networks based on requests. WLAN roaming relies on an AAA (Authentication, Authorization, and Accounting) broker with a RADIUS (Remote Authentication Dial-In User Service) proxy server. RADIUS is a widely used protocol for integrating hotspot services into AAA-based cellular networks.

Benefits of Cellular WiFi Integration Architecture

The cellular WiFi integration architecture offers several key benefits:

• Cellular operators can offload data traffic to WiFi hotspots during peak hours.
• WiFi service providers can expand their subscriber base by forming partnerships with cellular network operators.
• End users benefit from improved performance due to wider coverage, higher data rates, and lower costs.
• It facilitates more efficient use of radio spectrum.
• It enables cost-effective business applications, including integrated voice services, seamless wireless data services, common billing, secure communication, and wireless multimedia.
• It allows for flexible integration of new access networks at the IP level.
• It supports seamless handoff and roaming between WiFi and cellular networks.
• Mobile cellular devices with WLAN capability can take advantage of free WiFi internet services at locations like airports, cafes, and bookstores.

Conclusion

The proposed cellular WLAN (i.e., WiFi) integration architecture benefits all stakeholders: cellular mobile operators, WiFi data service providers, and end users of both cellular and WiFi networks.