There is some controversy regarding how to support Voice over LTE within the 3GPP group; clearly it is critical for LTE’s long-term success, but what are operators’ attitudes in terms of the urgency of Voice over LTE?

There are three main ways to enable voice calls over an LTE network. The first option is the Circuit Switched Fallback (CS Fallback), in which the LTE terminal drops back to 2G/3G for voice calls and SMS. The main drawback of this approach is the user experience, due to an extra delay before starting the call setup procedure. The user may not be able to maintain the LTE session while on the call. The second option is using Voice over LTE via Generic Access (VoLGA) technology, which will enable mobile subscribers to receive a set of voice, SMS and other circuit-switched services as they transition across GSM, UMTS and LTE access networks. The main concern with this approach is the timing; the goal is to introduce VoLGA in 3GPP Release 10. First LTE specifications are in 3GPP Release 8; however VoLGA has a great support from vendors. In time, it is expected that VoLGA specifications will be presented to the 3GPP for consideration as a recognized standard. The third option is IP Multimedia Subsystems (IMS)/Session Initiation Protocol (SIP), an architectural framework for delivering Internet Protocol multimedia services designed by the 3GPP group as part of its vision for evolving mobile networks beyond GSM. There are several concerns with this architecture, such as its lack of technological maturity, the minimal amount of investment that mobile operators have put into IMS, and other technical challenges that make IMS implementation complex.

CS Fallback is a good start option for early LTE deployments, and VoLGA is also a good “fast track” option that promises medium and long-term investment protection, has good support and is designed to deliver telephony services profitably. But IMS is the target mechanism for many operators for LTE support, and although operators have the option to migrate from one approach to another, the challenge lies between the lag between LTE deployment and IMS maturity.
Operators will be deploying LTE networks in mid-2010, but what is the timeline for adding voice services? Schedules will be determined by the operator strategies, selected equipment vendors, and the devices available to support Voice over LTE.

According to Herve Dubreil, from the Strategy and Development Division of Orange Group (France), Voice over LTE is not a priority in Orange’s network deployment roadmap, in an interview with Maravedis he confirmed that the company is “planning to tackle the voice aspect, but at the beginning our focus will be on data only. In the mid-term we will have handsets that will support both: voice and data. Voice will be the second step in our LTE deployment. Of course, there are many technical questions today on voice over LTE, so it is difficult to say today when it will be deployed, and we are considering that in the medium term we could offer voice over GSM and UMTS and data over LTE and HSPA, but in the long term we will need to add VoIP on the data networks. So it is clear we will have VoIP on LTE and HSPA+.”

Telstra (Australia) Executive Director Mike Wright expressed a similar viewpoint: “we believe that LTE will be used initially for data services and later on for VoIP, so we expect to see also some handsets that will support LTE, but our initial focus will be data services.” He continued, “I think the topic on the mechanisms to offer voice over LTE is not fully resolved by the 3GPP group. There are some operators that have a strong desire to offer VoIP in their LTE networks, since this is a low frequency deployment. So the big challenge lies on whether this is resolved or not.”

LTE operators seem to be in no rush to implement Voice over LTE. Interviews Maravedis conducted with multiple LTE-committed operators including Orange, Telstra, Telecom Italia KDDI (Japan), T-Mobile, CSL (Hong Kong), and others, revealed that 45% of them believed the need for Voice over LTE was “Moderately Urgent,” and that their initial focus will be on data services. Regardless, it is certain that eventually voice will be a “must-have” for all LTE networks. Consumers can subscribe to alternative voice services, but an LTE operator’s goal should be to offer their own voice service over their network.

Many solutions for voice in LTE are being proposed in parallel today. There is a tremendous pressure to roll out high quality services while quickly reducing operating expenses. Operators are facing a dilemma: they don’t want to move too quickly before they are ready, because they don’t want to sacrifice quality of service, increase CAPEX and OPEX, and risk the reliability and security of their networks. Nor do they want to move too slowly since progress depends on deployment. There are a number of things carriers should be doing while deploying to ensure quality and efficiency, and to keep costs down: select the best vendors and test LTE applications, since at the end of the day vendor choice will determine what can be rolled out and when.

For more information you can contact the author at cintia@maravedis-bwa.com

Copyright © 2009 by Maravedis Inc. All Rights Reserved.
No reproduction without consent.



>> Top