Dialogic Blog

Dean Bubley Guest Post: Can WebRTC give new life to IMS?

by Chad Hart

Dec 4, 2014 11:57:54 AM


Standard telephony is considered a commodity. To grow beyond this, innovative developers and service providers have made attempts at Value Added Services (VAS) for decades. These VAS have manifested in many forms over the years, including Color Ring Back Tones, voice portals, and other creative Interactive Voice Response (IVR) services. More than a decade ago IP Multimedia Subsystems (IMS) was created to usher in a new era of telecom VAS by making new services easier to create and deliver at scale.

Today consumers and enterprises get the vast majority of their apps and services from the Web and mobile ecosystems – not from telecom service providers and IMS. Does this mean IMS-based services are a lost cause? Will WebRTC technology help or hinder service providers in these efforts?

Dean Bubley of Disruptive Analysis has been exploring these concepts as an independent analyst for nearly a decade. We asked him to share his thoughts on the intersection of WebRTC & IMS, and how the telecom service provider ecosystem should consider this opportunity.


WebRTC & IMS Extension

A recurring theme in discussions of telco-domain WebRTC is using the technology to extend core services (PSTN, IMS-VoIP, SMS, USSD etc) to the web and/or mobile applications. In particular, there is interest in extending the new deployments of fixed and mobile IMS-based VoIP/video more broadly and more rapidly than “organic” uptake would suggest.


While there are also other suggested use-cases blending WebRTC and IMS, they are currently slow to emerge. Conversely, telco/IMS extensions pre-date the arrival of WebRTC, so there is a proven – albeit historically small – opportunity and demand.

What are IMS extensions & why are they important?

The basic “extension” concept is a simple one and has been around for some time: offer access to the telco’s main commodity-type standard services, on public or other carriers’ access connections and/or devices which don’t have a native “on-net” capability. Generally, these extension services use the same number and identity as mainstream services, interconnect with other networks, and support similar extra functions such as voicemail and call-blocking. They may also add extra features, such as video-calling, or allow different engagement models (eg “guests” and “users” rather than “subscribers”).

 The most widespread use-cases for VoIP/video extensions are:

  • Multi-device support (call or SMS from PC or tablet using the same number)
  • Coverage improvement by using WiFi where cellular signals are poor
  • Roaming avoidance (e.g. for outbound travellers on operators with limited negotiation power for good wholesale termination rates)
  • Ability to pick up calls to fixed PSTN numbers from a mobile device

Such models have been fairly widespread, but used only patchily by consumers in the past, because of high development costs, poor UIs, limited promotion and awareness, competition from Skype, limited utility, or regulatory restrictions. In some operators there also remains considerable scepticism over using unmanaged (and so-called “untrusted”) WiFi access. In some cases the extensions have been based on central IMS-based services, while in others they have been IP add-ons to traditional circuit core networks.

More recently, IMS extension approaches have been seen as particularly useful for devices which do not have full 3GPP-style frameworks installed natively. Typically, the extended communications usually occur over WiFi or another network that is not directly controlled or QoS-managed by the host operator.

 VoLTE extensions

In general, Disruptive Analysis expects VoLTE adoption to increase over the next few years. However, it will be patchy and fairly gradual in most operators’ networks, except in markets where it is “strategic” such as the US, South Korea and Japan. In five years, around 30% of overall LTE subscribers should be using VoLTE at least some of the time, although the bulk will remain using conventional circuit telephony. 

Video-over-LTE (IR.94) smartphone users will be a fraction of that number, but the same applications may also be extended via WebRTC onto other video-optimised devices and contexts, such as domestic TVs.

In other words, operators will need more downloadable apps (or in-browser services) to drive scale for expensive and complex VoLTE deployments. Otherwise, the costs diminish the justification for the upgrade in the first place, as they are spread across a small number of users and end-points

For IMS/telephony extensions, the adoption of WebRTC will be driven by a set of main use-cases:

Extension of a mobile IMS VoLTE/ViLTE service either onto a phone or secondary devices such as PC or tablet, typically “OTT” via unmanaged WiFi, but also in some cases via cellular connection or managed WiFi.

  • Re-use of VoLTE application servers for other endpoint types, such as living-room TVs, or a range of possible IoT/M2M use-cases.
  • Integration of WebRTC-capable enterprise endpoints with an IMS core, eg in hosted UC or contact-centre scenarios.
  • Addition of video enhancements such as recording or voicemail, although this may require enhanced network MRF (media resource function) capability.
  • Re-use of IMS core network capabilities (eg identity, QoS) for “non-calling” applications, eg new formats of voice and video beyond the confines of VoLTE. In this case, APIs may be exposed internally within the telco to an application-development team, or externally to third parties.
  • Interactions between IMS and web services eg social networks or e-commerce, with click-to-call/hosted chat anchored in a VoIP/video server – or the other way around, with guest/temporary-user access enabled through web-based authentication and identity.

However, there is a large elephant in the IMS/WebRTC room – there are no really popular IMS services to extend besides VoIP, in either consumer or hosted-UC business variants. Some operators may try to combine VoLTE with RCS messaging - although Disruptive Analysis remains deeply sceptical that RCS has any utility in its own right and will garner few active users. Conferencing is one possible additional area for extension.

Fixed-VoIP extension onto mobile is an interesting niche, but rarely deployed today, but has significant potential. It could also incorporate video, either onto PCs, mobile devices or even living-room TVs.

 WebRTC vs. alternative mechanisms for IMS extension

WebRTC is not the only platform for telco VoIP extension. Other options include both softphones and embedded 3GPP-based VoIP-over-WiFi capability.

Indeed, some forms of telephony-over-WiFi have historically been enabled via a combination of SIP-softphone and UMA/GAN type Telco-OTT services, since around 2005-2006. BT, Orange, NTT DoCoMo, T-Mobile US, Rogers and others have provided this type of capability – with T-Mo US probably the most visible in recent years. Overall volumes of users have been comparatively low, however – probably fewer than 20m globally and far lower than the use of non-telco communications apps such as Skype and FaceTime. (T-Mobile US claimed 5m monthly active users as of mid-2014).

More recently, a number of handset vendors – notably including Apple – have implemented IMS-based WiFi calling capabilities natively on devices, which should lead to a considerable uplift in usage. This has been paralleled by increasing support among operators, although it still remains far from universal.


But while Internet-capable softphones have been around for some time, WebRTC should make telco VoIP (& video-calling) extensions easier to create and cheaper/faster to develop. There is significant interest and activity in extending VoLTE services into browsers or native apps, where they are not natively supported “out of the box” in hardware. Older circuit-switched calling can be linked to the Web via WebRTC as well.

Numerous vendors already offer telcos gateways or “controllers” for this purpose, even prior to 3GPP standards being finalised. Some gateways also come with API platforms based around IMS-enabled capabilities (see below).

An important question is whether WebRTC is primarily going to be used to deliver an existing service onto a new device (or over a new network such as WiFi), or if it is used as the basis of an enhanced service that goes beyond the native capabilities of the “dialler” or normal embedded communications application. The more complex scenarios show the limitations of IMS WiFi-calling, compared to the web/context-integrated capabilities of WebRTC.

In addition, 3GPP WiFi-calling is a technology which is unlikely to be implemented on most non-cellular devices such as PCs and tablets. In such cases, browsers are much more likely to be capable endpoints. The jury is also still out about how fast VoLTE capability will migrate down to the lower tiers of handsets – which are already starting to move to WebRTC-enabled browsers and application web-views.


There is currently an up-swing in growth of IMS-based services, notably VoLTE in mobile networks. However, as voice-telephony is a peaking (or even declining) market, it is necessary to “sweat the IMS assets” to add user volumes more rapidly, improve functional utility or new use-cases, and hopefully increment revenue – or at least, limit declines and churn.

 WebRTC extensions and enhancements enable those possibilities, especially for use-cases where additional functionality and context-awareness is required. There will also be additional opportunities for standalone WebRTC extensions, for devices that will have browsers, but will likely never support native IMS implementations.

Disruptive Analysis is a leading analyst firm covering advanced communications applications and technologies. It has recently published its updated 2014 strategy and forecasts report on WebRTC – see www.disruptive-analysis.com for more.

Interested in how to power WebRTC and IMS-based services with a media developer platform and Media Resource Function (MRF)? Check out PowerMedia XMS.