VoLTE Emerges as Mission-Critical Technology for Operators in 2017

The article below is from the December 2016 issue of SAMENA Trends (page 67) and is published here with permission.

VoLTE, or Voice over Long Term Evolution, is rapidly revolutionizing voice service for mobile communications. Most voice calls still use 3G networks, but in the next few years operators are expected to make a massive transition to VoLTE. This will eliminate the need to have voice and data on separate networks and open a new era of integration for next-generation voice services.

But making the transition to this new standard involves new equipment, new roaming partnership agreements, and new services and pricing, among a host of other major changes. In particular, it will be imperative for operators to keep pace with their competitors’ implementation of VoLTE while at the same time maintaining their current quality of voice service that users expect.

At Syniverse, we’ve been right in the middle of helping operators navigate this transition, and over the past year, we’ve held a series of special VoLTE webinars focusing on aspects such as roaming, interconnect, and clearing and charging. In addition to the sessions themselves, the questions and answers we’ve addressed following each webinar particularly have shed light on important lessons learned and best practices that we think can help guide many operators in their VoLTE transition. In this article, I’ve compiled some of the most important of these below.

The insights offer useful guidance for a technology rapidly gaining ground. As of October, over 150 operators in 72 countries had invested in VoLTE, according to a report by the Global Mobile Suppliers Association, including over 90 operators that had commercially launched VoLTE services in 52 countries. Moreover, the number of VoLTE subscriptions is expected to exceed 200 million by 2017, and then hit over 3 billion by 2022, according to the latest Ericsson Mobility Report. It’s critical that operators prepare for this major transition thoroughly.

Selected Questions and Answers from Syniverse’s 2016 VoLTE Webinars

Are there any operators doing VoLTE interconnect trials, and are there any commercial deployments?
Over the past few years, we’ve been fully immersed with VoLTE trials, and they’ve primarily been roaming trials. As operators have deployed their IMS cores, they have really been focused on getting the service to work in their home market first. Once they have done that, their next priority has been ensuring that their subscribers have the same quality of experience when they roam outside their home network. As a result, a lot of the trials that we’ve been involved with so far have pertained to roaming. However, we’re currently involved with a number of interconnect trials in North America as well as other regions, and this number is starting to accelerate as operators are increasingly making it a priority to provide IMS services like VoLTE, ViLTE and RCS. Many of them want to deploy these services this year and get their trials underway. So, although we’ve had a number of commercial launches for VoLTE roaming, I expect to see a launch for VoLTE interconnect here in the near future.

A challenge for VoLTE interconnect is number portability management. How is this handled?
The GSMA is considering some options for number portability resolution and working on an industrywide solution for this now. I think where we’re heading is that we’ll see independent IPX providers implement a variety of number portability resolution methods. For instance, we could rely on local number portability data local within a network or home country to provide number portability resolution. Or we could rely on third-party number portability sources on a per transaction basis. These options aren’t fully defined yet from an industry perspective, but at Syniverse we have developed our own views internally and our own solutions for addressing this problem.

What impact does VoWiFi have for IMS?
This is an extremely timely question because we’ve been seeing a lot of movement with VoWiFi. It’s a technology that’s been around for a long time. There was an effort to standardize it about a decade ago in an initiative called UMA, which was adopted by some operators but not widely. But the big game-changer was a combination of the 3GPP introducing a component called an EPDG and the large OEMs integrating this functionality into their devices. What an EPDG does is allow untrusted Internet access – that is, Wi-Fi – into an operator’s IMS core. So, this enables a single IMS framework for VoLTE, ViLTE, RCS, etc., and it also enables a bridge to VoWiFi. Another benefit is that things like single radio voice call continuity or handover from one network to another are possible. And one more benefit is that HD-quality calls can be enabled between VoWiFi subscribers to VoLTE subscribers.

What is the impact of local breakout on charging?
From a wholesale billing perspective, the MSESS and MSG TAP records introduced in TAP3.12 will be used for wholesale billing of voice and SMS-supported via local breakout. IMS accounting records can be generated from both the visited P-CSCF and home S-CSCF. The VPMN may create call detail records (CDRs) from either the S-Gateway or the P-Gateway. These CDRs, however, do not contain all of the information that is needed to create a TAP3.12 call session record, so another CDR must also be sent to the offline charging system from the P-CSCF.

Single Radio Voice Call Continuity (SRVCC) is needed to support circuit-switched (CS) calls for VoLTE handoff, and this is not available with S8 home routing (S8HR). Could you explain?
SRVCC is available with S8HR, but it is challenging. A change request has to be submitted to IR.65 to clarify SRVCC for S8HR. It requires that an IMS interconnection be in place between the roaming partners. If an IMS interconnection is not in place and ISUP interconnect is in place between roaming partners, then Codec renegotiation for network Release 10 and above is needed, if media are anchored in the ATGW and the ATCF enhancement is used. MSS/MGCF configuration based on the STN-SR information coming on the international ISUP NNI is required for network Release 10 and above, if media is not anchored in the ATGW.

Nour Al Atassi is a former Regional Vice President and Managing Director of the Middle East and Africa at Syniverse.




  1. Ishita Guha

    Thank you for sharing. Looking forward for article on roaming call flow & tapout//tapin generation in VOLTE

    • Nour Al Atassi

      Thank you for your comment. VoLTE is a major area of focus for us at Syniverse this year, and we look forward to sharing further insights on this rapidly growing area of mobile. Please stay tuned here to Synergy for more of my perspectives on VoLTE and LTE this year.


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