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Voice Over LTE: More Pitfalls Than Promise for Now
Cellular operators worldwide are building, trialing, or planning Long Term Evolution (LTE) networks at an ever-increasing pace. Initially they will use the emerging high-speed wireless technology to provide data services mobile Internet access. But the recent development of a technical foundation for delivering voice calls over IP Multimedia Subsystem (IMS) network infrastructure in the form of the voice over LTE (VoLTE) spec finally provided a standardized way to deliver voice calls in addition to broadband data services over LTE networks. Thus it would seem that there is little to keep VoLTE services from spreading worldwide, as well.

But IMS and LTE networks will not always be available in the same places at the same times. And even where they are, operators often will not want or be able to use them together to deliver voice services. As a result, alternative approaches will be necessary or preferable in many situations. There are several possible alternatives. One is to use existing circuit-switched infrastructure to deliver voice, using LTE only to provide mobile data service. A second is to insert additional equipment in the network that makes it possible to send VoLTE wireless links without IMS infrastructure. A third option is to deliver VoIP over the LTE network as a separate all-IP service. Each of the alternatives has disadvantages for operators, and at least one also represents a potential threat.

Though LTE is quickly becoming the predominant choice in the mobile broadband data race, its role in voice services is less clear. There is little doubt that ultimately the method of choice for most mobile operators will be to provide voice services running over IMS and LTE and based on the VoLTE spec. What is far from clear is when this will happen on a broad scale. It will require a global IMS rollout matching the global LTE rollout, with the former taking more time than the latter. Thus widespread implementation may take five or more years, and some operators may keep using their 3G networks for voice services for another decade or two.

This unpredictability and long time horizon will cause many operators to take alternative approaches. The most convenient of these, and the one most likely to see widespread use, is circuit-switched fallback (CSFB). But CSFB has significant disadvantages, which provides an opportunity for the growth of at least two other alternatives: VoLTE via generic access (VoLGA) and over-the-top VoIP (OTT VoIP).

Voice Over LTE: More Pitfalls Than Promise for Now describes the disconnect between IMS and LTE rollout processes. It examines the options LTE operators will have for delivering voice services, and it explores the dynamics that will shape LTE operators' moves toward delivering voice services. Further, the report surveys key vendors' LTE product offerings, customer wins, and evaluations of how IMS and LTE will roll out in the future.

Sample research data from the report is shown in the excerpts below:
Table of Contents (4gltei1010_toc.pdf)
While delivering voice services over IMS infrastructure will ultimately be the default approach for LTE operators, in many cases it may not be possible or practical for some time. In the interim, carriers will have several alternatives from which to choose. However, none of them will be ideal. The advantages and disadvantages of each are summarized in the following excerpt.
[click on the image above for the full excerpt]
Companies profiled in this report include: Alcatel-Lucent (NYSE: ALU); Ericsson AB (Nasdaq: ERIC); Huawei Technologies Co. Ltd.; Kineto Wireless Inc.; Motorola Inc. (NYSE: MOT); and Nokia Siemens Networks, a joint venture of Nokia Corp. (NYSE: NOK) and Siemens AG (NYSE: SI; Frankfurt: SIE).
Total pages: 16
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