Thursday, May 2, 2024

WiFi offloading vs VoWiFi

In recent years we have encountered a lot of customers wanting to utilize their networks more efficiently, and provide premium service for their subscribers. WiFi offloading and VoWiFi are popular ways to to extend the mobile operator’s network coverage into wifi, free bandwidth from congested cellular networks and improve user experience with better connectivity. The technologies share many similarities and both use a 3GPP AAA server for SIM based authentication.

WiFi offloading offers some flexibility in the supported authentication backends and the SIM authentication can be done through various HSS and HLR interfaces depending on what the mobile operator has available. This is especially important in roaming scenarios where the WiFi provider has agreements with multiple MNOs to offload their subscribers.

WiFi calling is more strictly standardised to support high QoS for the voice call, and also the handover between VoWiFi and VoLTE. This allows users to move outside the range of the WiFi hotspot and seamlessly continue the call over VoLTE, and vice versa.

Let’s take a look at the key differences between the two related technologies:

Comparison WiFi offloading VoWiFi
Purpose Ease network congestion, Network CAPEX savings, Roaming cost savings, Secure authentication to private wireless networks: carrier, industrial, in-flight, underground, IoT Ease network congestion, Indoor coverage extension, Combat OTT apps, Roaming cost savings
Relationship between MNO and access network provider Agreement required between MNO and wifi provider No relationship between MNO and wifi provider
Access network Carrier or partner wifi Any public or private wifi
Traffic Data only Voice and video calls
SIM authentication protocol EAP-SIM, EAP-AKA, or EAP-AKA’ EAP-AKA
Supported HSS interfaces SWx, Wx, Cx, S6a SWx required
Supported HLR interfaces MAP, SIGTRAN Not supported
ePDG Not applicable ePDG mandatory
Security WPA Enterprise IPSec tunnel between UE and ePDG
IMSI Privacy Yes, supported by Radiator Yes, supported by Radiator

What is different?

The main difference between WiFi offloading and VoWiFi is the relationship between the mobile operator and the wifi provider: operator controlled data offloading always requires a prior agreement between the MNO and the WISP. WiFi offloading is often done in high traffic areas such as airports, sports stadiums and concert venues, since offloading users to WiFi is cheaper than adding microcells to boost the mobile signal. MNOs can invest in carrier wifi hotspots themselves, or make offloading agreements with wireless ISPs.

VoWiFi requires the mobile device to be connected to a wifi before attempting a VoWiFi call, but any type of wifi can be used for WiFi calling, including consumer home wifi. Therefore no relationship between the mobile operator and WiFi provider is required. However VoWiFi has specific technical requirements for the MNO: a HSS with SWx interface and ePDG are required.

Private network authentication

WiFi offloading technology is also applicable to private network offerings, such as industrial and IoT networks. SIM authentication provides a secure method to authenticate users into a private network using their SIM credentials and eliminates the human element of reusing and sharing passwords. In high security deployments the SIM authentication can be further combined with device IMEI check, to make sure that only authorised users and devices are able to access the private wifi network. VoWiFi is also possible in private networks, and can enable voice calls in challenging environments such as underground.

Interested in WiFi offloading or VoWiFi?

Radiator SIM Pack provides a fully featured 3GPP AAA server solution, with superb flexibility to connect with your environment. Please contact the Radiator team at sales (at) to get a quote.