According to GSA, there are over 70 mobile operators currently trialling or deploying VoLTE worldwide. This is a significant jump from the 11 live VoLTE deployments today. So why is this happening and why is it happening now?
There are of course technical benefits to VoLTE, as it is a step up in quality in the way voice services are provided. An independent study, carried out by Signals Research Group, outlines that it outperforms existing mobile and over the top voice services. However, this does not tell the whole story. Upon inspection of the VoLTE deployments worldwide, there is evidence that market pressure is a key factor in determining when VoLTE gets deployed. The figure below illustrates the correlation of VoLTE systems by market – The bars start at the launch of LTE and finish at the launch of VoLTE, with bars colour coded by market. As can be seen, multiple operators in the same market tend to launch it closely together. There are elements of one-upmanship at play here, as well as a realisation that the earlier your competition launches VoLTE, the earlier they move their subscribers onto that system and the earlier they get the benefits of a single network core (reduced OpEx and reusable spectrum).
One of the key elements in building a network that can handle VoLTE is to have a large degree of control plane scalability. While additional guaranteed bit-rate bandwidth is necessary to actually carry the voice traffic, this is small change when compared to services like streaming video and will not have a meaningful overall impact. However, the amount of signalling on the control plane will increase to new levels. Each time a phone connects to the network, additional signalling is required on top of the signalling required to set up a data connection. Whenever a phone call is made, or modified (e.g. by putting somebody on hold), significant signalling must take place to ensure that the subscriber gets the correct bandwidth and quality of service. The PCRF is a central control plane node in providing VOLTE (and other IMS) services and therefore must be capable of scaling in tandem with the uptake of voice.
VoLTE control plane nodes, such as the PCRF, must start small as the service is first rolled out and then grow as VoLTE takes over all voice traffic. This makes them an ideal choice to utilise the principles of virtualisation and NFV. If used effectively, virtualisation can simplify the scaling of control plane functions as the spinning up of such functions is made cost effective and in real-time reaction to demand. Thus, virtualisation and NFV provide a compelling environment for VoLTE, the new wave in voice.
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