For an industry which has built its fortunes firmly on voice services, it will seem bizarre to mobile historians that voice over LTE was such an afterthought. As an all-IP platform, LTE does not support conventional circuit-switched voice. In theory, that meant carriers could simply deliver VoIP, but with the competition from over-the-top services like Skype and Google Voice rising, they needed a more powerful weapon with which to differentiate themselves from the mass. VoLTE may be rather a late, blunt weapon, but it has been largely embraced as the way forward for voice services. It faces daunting challenges, but at its heart is the last hope for mobile carriers’ voice-based business – to integrate this into a broader, richer communications service that can be firmly differentiated from the web services and can form the basis of a developer ecosystem.
The challenges in its way are daunting however, for three main reasons – the technology itself; the power of the competition; and the decline of voice and messaging revenues overall.
The technology relies on having sufficient LTE coverage to minimize awkward fallback to 2G/3G; and on deploying an IMS (IP Multimedia Subsystem) core, such a significant undertaking that most mobile carriers are still holding off large-scale roll-outs. The need for 4G voice, and simplified routes to IMS, including hosted services, will spur adoption this year but there are other technical barriers too. VoLTE puts considerable strain on elements like Diameter signalling and roaming. Voice quality of service must be significantly higher than that of over-the-top services to encourage user uptake, but this entails investment in RAN functions to prioritise VoLTE packets over other classes of IP data and to schedule variable VoLTE packet sizes. One reason for operator delays in deploying the technology is to avoid delivering a service which is just ‘me-too’, or worse, is an inferior experience to that of 3G voice or Skype.
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