Wi-Fi calling / VoWiFi upgrade for mobile networks

Adding Wi-Fi to an operator’s Evolved Packet Core as an additional voice and IMS channel option


Bolstering network coverage and improving user experience are two advancements making up the very top of every mobile network operator’s wish list. Wi-Fi calling is a technology that makes headway in both of these aspects and it comes without the need for a complete overhaul of existing network architecture. Since its introduction, Wi-Fi calling has been launched by carriers who recognize the fact that this technology quickly moves from early adoption to a feature generally expected by most subscribers.

WiFi Calling is advantageous for operators and subscribers alike.

Wi-Fi calling aka VoWiFi is one of these services proving themselves from the very beginning to be truly beneficial for customers and business, enabling operators to improve service quality, network performance and revenue at the same time. The speedy adaptation is made possible by an architecture which is designed by the 3GPP standardization body, striking the right balance between new functions and investment protection by utilizing existing elements. It permits a secure and efficient integration of non-3GPP wireless networks into the access technology strategies of all operators.

With decades of experience in Diameter for non-3GPP access and a 15-year background in AAA services for packet-switched network control over Radius and Diameter in 3GPP and Wi-Fi offload, Siemens Convergence Creators is ideally suited to offer a scalable ePDG authentication that fulfills all operator requirements.

Thanks to standardized interfaces, our authentication solution for Wi-Fi calling is compatible and interoperable with all Wi-Fi ePDG EPC vendors, HSS providers, and IMS ecosystems in accordance with the latest 3GPP specifications. However, flexible dictionaries and customizable handlers can be used to adapt the core and optional Diameter interfaces such as SWm, SWx, and S6b for mobility. Depending on partnering plans in Wi-Fi access, other interfaces are also available. Wi-Fi access authentication may be required in addition to tunnel authentication, or it may be deemed necessary in order to provide a secure and seamless user experience. In this context, Diameter SWa and SWd are useful and native support for legacy interfaces like Radius and GSM MAP (HLR) are very often indispensable. A 3GPPAAA should therefore be capable of supporting both native Diameter and Radius and have a proven success history in both worlds.

SIM and SIM-less devices

The opportunity to connect combined SIM and SIM-less devices using extra authentication tokens and modified ePDG interfaces (as part of future ePDG protocol extensions) will significantly improve subscriber convenience and offer a calling experience known thus far only in proprietary designs. Specific designs for iOS and Android devices (with Windows to follow soon) are already available today. The ability to use various other EAP methods (like TLS, PEAP or CHAP) and to deploy other authentication schemes allows operators to quickly offer individual services to existing and new subscribers in all access networks.

WiFi calling / VoWiFi solution architecture: scalable and reliable
WiFi calling / VoWiFi architecture

Operators can begin their involvement with Wi-Fi calling with a relatively small financial and technical commitment and then enhance their system, as subscriber figures grow, from perhaps 100,000 up to 50 million or more. The Siemens Convergence Creators VoWiFi/Wi-Fi calling solution runs on a highly scalable, Unix-based platform of front-end servers for authentication, authorization, and accounting and a redundant set of high-performance back-end servers for real-time session management and is available in a per-site- and an optional geo-redundant architecture.

Siemens Session Manager covers all AAA needs (not just VoWiFi) and Siemens Policy Manager (PCRF) controls the QoS (Quality of Service), both with the same user interface. Both offer a virtualized architecture for state-of-the-art NFV-orchestrated deployments. The offer is based on readily available telco-standard OSS and BSS requirements and practical deployment experience with systems serving more than 300 million subscribers worldwide.