WiFi Calling (also known as Voice over WiFi). Like VoLTE, this is compliant with
3GPP standards and enabled by an IMS.
Mobile operators can use this to ‘fill the gaps’ in VoLTE, while for non-cellular providers, it provides a way to offer wireless voice services without the need for an MVNO agreement.
WiFi Calling is an extension of the 3GPP’s evolved packet core (EPC) architecture which allows any WiFi network to access the EPC via a gateway at the border between the public internet and the operator domain. The gateway is the evolved packet data gateway (ePDG) which is part of the 3GPP I-WLAN platform. The ePDG creates a secure IPsec tunnel from the EPC all the way to the device and anchors traffic in the packet gateway (PGW), which means WiFi can be treated in the same way as a cellular RAN by the mobile core.
Figure: Architecture for Voice over WiFi. Source oracle.
WiFi Calling can be an effective answer to many of the voice challenges .
-Mobile operators can harness WiFi Calling supplementing their own coverage and
capacity with a lower cost complementary network. This enables them to build out
LTE at the pace to fit the primary data-driven business model, rather than be forced to achieve universal coverage in order to support voice, which is often a loss leader.
-Non-cellular operators can greatly reduce – or even eliminate – the fees they pay to
MNOs for access to mobile networks, and add their own wireless voice services to
their multiplay bundles. WiFi-first and WiFi-only services are being launched by many MSOs round the world, especially in the US (Cablevision offers WiFi-only, including voice, for instance).
- WiFi, often at very high quality, is far more heavily installed inside buildings than cellular small cells, and provides a readymade source of voice coverage.
The main reasons to opt for WiFi Calling:
a) Security and privacy
The ePDG is frequently provided by a company with expertise in this area. Security is the most prominent concern among operators adopting IP-based LTE in general and WiFi Calling in particular .An ePDG which is dedicated to securing the border can significantly improve the operator’s defences against the rising tide of malware and hacking of IP systems and therefore mitigate the key risk to the business case. An ePDG protects users’ communications while optimizing the ability of the mobile core to resist overloads and attacks. When securing the border between wireless access and packet data networks, many carriers believe hacks and overloads are best addressed before they get anywhere near the PGW itself, and by a purpose-built that has been designed specifically to perform encryption at ultra-fast speeds and to offer deep layers of protection.
b) Differentiation of services
WiFi Calling, to fulfil its business purpose, needs to be clearly superior to the over-the-top experience in terms of consistent experience with the mobile network, dropped call rates, and so on. Some of this differentiation is achieved through IMS value-adds, but others rely on the network itself – particularly, high levels of coverage, same native dialer, same mobile identity, instant sign-in and authentication, and QoS levels related to policy. The ePDG is optimized to enable many of these differentiators and can be linked to a policy server to add intelligence when allocating connections. In addition, a dedicated system can offer higher levels of functionality and performance when managing authentication, connection choice or handover.
Many operators are handling millions of subscribers, making billions of calls a month, and so their gateway and core platforms need to be able to scale up to huge levels of usage. Dedicated ePDGs are designed specifically to handle and secure subscribers at the border and so they have optimized performance levels and ability to scale.
IPsec is highly process-intensive and so can have an impact on the user experience and the core performance if carried out by a general purpose platform. Any ePDG must combine support for high density service interfaces with low power consumption. In addition, encryption and decryption should have minimal impact on latency.
Mobile IP services are in their infancy and the needs of the operator and the subscriber are changing quickly. Part of an operator’s competitive edge comes from its ability to respond to changes rapidly and cost-effectively, in order to keep its user experience strong and updated, without having to make a major network change each time. A purpose-built gateway often has better ability to address emerging new requirements flexibly because it can perform changes at the edge, without having to impact on the entire packet gateway on each occasion. The dedicated ePDG has the horsepower to deliver a range of added value functions such as secure video delivery and calls and to support a wide, and growing, set of services in an agile manner. It can leverage embedded service and application intelligence to allow the operator to deploy new services quickly and flexibly.
e) Best of breed
Many mobile operators are increasingly concerned about vendor lock-in, and procuring all their RAN and core systems from just one or two suppliers. Adopting a best-of-breed approach, with integration assured by standards and interfaces, can increase competition in an MNO’s ecosystem and improve their ability to demand the best performance and pricing.