Wi-Fi calling enables mobile calls over Wi-Fi instead of cellular networks, improving coverage in weak signal areas. It reduces costs, enhances call quality, and allows smooth transitions between networks.
By Brad Nakase, Attorney
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WiFi calling, also known as VoWiFi, is the term for data and voice calls made from mobile phones over IP (Internet Protocol) networks using Wi-Fi rather than the cell towers that cellular networks provide. With the help of this function, compatible phones can route standard cellular calls via a wireless local area network (Wi-Fi) that has broadband Internet, switching between the two with ease when needed. The GAN (Generic Access Network) protocol, commonly referred to as UMA (Unlicensed Mobile Access), is utilized in this function.
Using a wireless broadband network in accordance with IEEE 802.11 norms for voice communication is known as VoWLAN (voice-over wireless LAN), or VoWiFi (voice-over Wi-Fi). It is essentially VoIP (voice-over IP) on a wireless network.
GAN/UMA basically enables cell phone transmissions to be transmitted to the network access point via the internet instead of over the air via UMTS, GSM/GPRS, or other similar protocols. As though it were emanating from a tower antenna, this data is fed into the cellphone network by a different device called a “GAN Controller” after being received from the Internet.
The handset can make and receive calls just like it were connected to the GANC’s location of presence over the air, rendering the call undetectable to the entire network. In areas with inadequate cell service when there is another way to access the internet, this can be helpful, particularly at home or at work. Because of the system’s smooth handoff, users can move between cell and WiFi calling networks and back afterward with the same level of obscurity that the cellular network provides when switching between towers.
Anywhere there is internet connectivity, a UMA-capable phone can link to its internet service provider because the GAN system operates online. Travelers can utilize this to make calls to their home service region from any part of the world by connecting to their provider’s GANC. This is dependent on the internet connection’s strength, though, and might not function properly on long-latency or bandwidth-constrained connections.
A properly configured wireless connection that optimizes UMA packets is another tool that some carriers offer to enhance the quality of service, or QoS, in your house or office. Another advantage of WiFi calling is that communications may be placed from a mobile device over the internet using the exact same native call client; it relies on the mobile cell operator rather than third-party VoIP (Voice over IP) closed services like Skype or WhatsApp.
IMS/SIP-based mobile telephony, data, and multimedia apps are extended across IP networks by the GAN protocol. Numerous phone makers, such as Samsung and Apple, have dubbed the newest generation technology VoWiFi. Operators like T-Mobile US & Vodafone are also following suit. In order to function, the service requires IMS, IPsec, ePDG, and IWLAN.
A 2G (A/Gb) link between the GANC and the MSC/GSN (mobile core network) was encouraged by the initial Release 6 GAN standard. Today all GAN capable handsets are dual-mode 2G/Wi-Fi, and all commercialized GAN dual-mode mobile deployments are predicated on a 2G connection. Support for multiple modes of handset operation was, nevertheless, specified in the standard. The standard therefore supports 3G/2G/Wi-Fi phones. In 2008, the second half saw the announcement of the initial 3G/UMA devices.
Typically, a UMA/GAN phone can function in four different ways:
The phone always looks for GSM cells whenever it first switches on in order to pinpoint its location. As a result, the carrier can adhere to current roaming agreements, create the appropriate rate plan, and route the communication to the closest GANC.
The GAN standard was improved at the conclusion of 2007 to accommodate 3G (Iu) interfaces between the MSC/GSN and the GANC. This native 3G connection can be utilized for 3G femtocell delivery and dual-mode devices. These additional features are explained in the GAN version 8 documentation.
A voice-telephony-capable Wi-Fi network needs to be carefully planned to optimize performance and accommodate the necessary call density. A voice network consists of Wi-Fi access points and call gateways. Call handling between wireless IP phone systems and connections to conventional phone systems are provided by the gateways. More robust signal coverage is required for speech applications on the WiFi calling network than for the majority of data-only apps. The wireless network must also enable smooth roaming across access points.
Carriers
Subscribers
Upgrades to Wi-Fi/UMA-enabled phones are required for subscribers to utilize the service.
Due to the device moving out of or inside Wi-Fi’s range, calls could be more likely to terminate while switching from Wi-Fi to regular wireless connectivity and vice versa. The severity of this issue may differ depending on the phone being used.
The UMA might employ an alternative frequency which is more vulnerable to certain kinds of interference.
Before any benefits are felt, some preparation can be needed to supply connection points (such as login information). Subscribers may need to wait for this to happen, and more assistance may be needed. Support charges could go beyond the phone (wireless) provider. Network administrators might be required to assist a user in navigating a phone’s settings, something they may not be very familiar with.
Because more circuitry and components are needed for manufacturing, phones that handle multiple signals—both UMA/Wi-Fi and the signal type utilized by the provider’s towers—may be more costly.
The assets of the network that provide the Wi-Fi signal are used in this way, as well as any indirect networks that are used while the primary network is used. The bandwidth is depleted. A decision to support certain forms of network traffic (such as DNS & IPsec-encrypted traffic) may impose one or more requirements on the security of the network (firewall) policies.
The WiFi module on a mobile device should be activated to use GAN/UMA. Comparing this to turning off GAN/UMA (and consequently WiFi), the battery drains more quickly and the talk and standby times are shortened.
Enabling the WiFi module is necessary when using GAN/UMA via a mobile device. As a result, the battery drains more quickly and the talk and standby times are less than when GAN/UMA (and consequently WiFi) is disabled.
With cellular-based E911s that employ GPS/Assisted GPS, UMA is incompatible. Typically, the subscriber registers a permanent primary address to the carrier through mobile settings, an app, or a website offered by the carrier.
No assurances of QoS. Because the Internet (and consequently the majority of home networks) use a best-effort delivery approach, call quality may be impacted by congestion on the network. P2P file sharing, gaming, and HD video all battle for available bandwidth, which is typically an issue with a subscriber’s residential network. While certain network equipment can address this by turning on QoS for VoIP standards, this is made more difficult by the fact that the majority of UMA operates using IPsec over UDP, rendering its foundational protocols (IMS/SIP) invisible from a network standpoint.
In order to counteract this, handsets might internally prioritize IPsec traffic to a separate WMM class (like AC_VO). The ability of the subscriber’s remaining network to accept and prioritize this data over additional bulk or latency-sensitive traffic is also necessary, assuming it isn’t fully integrated like most household WiFi routers and access points.
BT launched its first service, BT Fusion, in the fall of 2005. The service is predicated on GAN standard technologies prior to 3GPP. At first, Motorola phones were connected to BT Fusion via UMA over Bluetooth. Beginning in January 2007, it was marketed as a “Wi-Fi mobile service” and utilized UMA through 802.11 with phones made by Samsung, Motorola, and Nokia. The service has subsequently been withdrawn by BT.
TeliaSonera launched “Home Free,” an 802.11-centered UMA service, first on 28th August 2006. The service, which began in Denmark, is no longer available.
Known in the United Kingdom as Signal Boost, Orange’s “Unik service” was introduced on 25th September 2006. New clients in the UK are no longer able to use this service. In the UK, France, Poland, Spain, and the Netherlands, approximately 60 million Orange mobile subscribers are covered by the announcement, which is the biggest to date.
The United States’ first UMA deployment was announced by Cincinnati Bell. Users of the service, which was formerly known as CB Home Run, can easily switch between the Cincinnati Bell mobile network and a home WiFi network or Cincinnati Bell’s HotSpots. Fusion WiFi is the new name for it.
On 27th June 2007, T-Mobile US quickly followed. In the United States, T-Mobile’s service, which was formerly known as “Hotspot Calling” before being renamed “WiFi Calling”, enables users to switch between the T-Mobile mobile network and an 802.11x wireless connection or T-Mobile HotSpot with ease.
UMA plans were introduced by Fido & Rogers Wireless in Canada on 6th May 2008, respectively, under the brands UNO & Rogers Home Calling Zone (which was subsequently renamed Talkspot, and then once more as WiFi Calling).
Telstra, Vodafone, and Optus have all adopted GAN in Australia.
WiFi calling was first made available to EE users in the UK on the Nokia Lumia 640 & Samsung Galaxy S6 & S6 Edge smartphones on 10th April 2015.
Vodafone Netherlands introduced WiFi Calling functionality in March 2016 in addition to VoLTE.
Since the fall of 2016, Telenor Denmark users have had access to WiFi calling and voice-over WiFi, which includes the capability of changeover from and to the 4G (VoLTE) service. This works with a number of Samsung and Apple smartphones.
Organization within the industry UMA monitors all operator activity and the advancement of handsets today.
The mobile phone network Cell C in South Africa introduced WiFi calling in September 2015.
Voo, a cellular network in Belgium, introduced WiFi calling in November 2024.
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