GSMA VoLTE, not RCS, will drive IMS

The IP Multimedia Subsystem (IMS) has often struggled to prove its worth to network operators. Despite suppliers’ efforts to extol the technology over the last ten years or so, IMS remains niche.

Sure, an IMS architecture offers the prospect of launching new services more quickly and cost-effectively than is possible with softswitches and TDM kit, but the technology’s business case merits – historically at least – have been far from convincing. Many network operators have generally taken the view it would be too risky to invest in a new architecture to enable additional services that may or may not be commercially successful.

And where IMS has been deployed, it’s the fixed-line players that have done most of the running. Standalone mobile operators, on the whole, have steered clear.

This looks set to change. To plug a gaping gap in the original LTE specification – the lack of a CS (circuit-switched) domain – GSMA recommends an IMS-based approach to VoLTE.

Of course, mobile operators don’t have to follow GSMA recommendations. They may well pursue other VoLTE routes, perhaps by SIP-enabling MSCs through software upgrades, which would avoid IMS core investment. And if they have already invested in CSFB (circuit-switched fallback), mobile operators may well resist digging deeper to stump up for IMS. Both approaches look unsatisfactory.

Don’t get me wrong. I have no brief for any IMS supplier, but the argument for a standardised IMS-based approach to VoLTE looks a strong one.

If operators want to offer voice and SMS services that have – as a minimum – basic feature sets provided by circuit-switched 2G and 3G networks (call waiting and call forwarding, for example) and can meet regulatory requirements (lawful intercept and emergency calling), then IMS seems to fit the bill. What’s more, with standardised IMS, interoperability with domestic and international networks should be assured.

The case for investing in IMS, purely to deliver RCS-based services, looks less convincing. RCS will no doubt be a factor in scaling up IMS core capacity, but it’s unlikely to be a primary driver for IMS deployment. Some major operators that have already installed an IMS core for fixed-line services, for example, are choosing to offer 3G-based rich messaging services using the same IMS core. Among the operators that have launched joyn-branded services in Europe, I believe Telefonica Germany and Orange France have done exactly that.

Moreover, 3G operators choosing to offer IMS-based RCS will probably already have plans in place for GSMA VoLTE. Meanwhile, the business case surrounding IMS-based RCS is far from clear. Mobile operators with no immediate VoLTE plans – but wishing to test the market for rich messaging services – may well then opt for ‘IMS Lite’ or non-IMS solutions rather than invest in a full-blown IMS core.

One supplier tells me that operators are holding back on IMS investment for RCS because they are finding it difficult to develop a business case to compete against OTT services, which, for the most part, are free or thereabouts. Historically, though, the business case for new technology has usually revolved around incremental revenue per user. But if the RCS business case can only be built on subscriber retention, operators are confronted with a very different financial planning exercise from what they are used to. Suppliers, then, are getting frustrated that many operators have yet to work out business cases for new technology investment based on subscriber retention.

GSMA VoLTE looks much more fertile ground for IMS suppliers. After all, it would surely be a big mistake for operators to offer a worse voice experience over 4G than they do over older technologies.

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