SECURING HIGH-QUALITY COMMUNICATION SERVICES OVER IP NETWORKSAs mobile-broadband networks continue to expand, VoLTE leverages telecomcharacteristics such as QoS and global reach to offer innovative communicationservices including evolved HD voice, music sharing within a call and videocommunication over IP networks.ericsson White paperUen 284 23-3160 Rev B | November 2014Voice and videocalling over LTEVOICE AND VIDEO CALLING OVER LTE • VOICE SERVICES IN MOBILE-BROADBAND NETWORKS 2Voice services inmobile-broadbandnetworksMobile broadband has created a world of opportunities and opened up new revenue streamsfor operators. Opportunities are often coupled with challenges, and mobile broadband tests theposition of communication services, such as voice, which today account for around 60 percentof operators’ annual revenue – about USD 600 billion in 2014 – globally. The crucial question ishow to take advantage of mobile-broadband opportunities, while at the same time maintainingand increasing revenues from communication services for consumers as well as for businessusers.LTE networks can deliver mobile broadband with greater data capacity and lower latency.However, as there is no circuit-switched voice domain in LTE, the mobile industry has adopteda globally interoperable IP-based voice and video calling solution for LTE, known as VoLTE, whichalso enables development of new innovative communication services.Over-the-top (OTT) communication solutions, such as Skype and FaceTime, have driven useradoption of more advanced service behavior based on VoIP, video-calling and messaging servicesin combination. However, a fully satisfactory user experience cannot be provided by OTT solutions,as there are no QoS measures in place, no handover mechanism to the circuit-switched network,no widespread interoperability of services between different OTT services and devices, and noguaranteed emergency support or security measures. Consequently, the adoption of OTT clientsis directly dependent on mobile-broadband coverage and the willingness of subscribers to usea service that lacks quality, security and flexibility.Operators have started to launch nationwide commercial VoLTE services for voice and videocalling over LTE, including seamless service continuity with circuit-switched networks. In addition,continuity with Wi-Fi networks for residential use is also starting to be available on the market.With native support in smartphones and networks, a seamless high-quality experience is a givenwith VoLTE, and the service reach can also be extended outside LTE coverage and to additionaldevice types.Mobile-broadband networks will evolve into their fifth generation (5G) starting around 2020.VoLTE technology is a natural fit within 5G; VoLTE will therefore also serve as the foundation fortelecom-grade voice and video calling services in future 5G networks.VOICE AND VIDEO CALLING OVER LTE • A GLOBALLY INTEROPERABLE SOLUTION 3
A globally
interoperable
solution
LTE and Evolved Packet Core (EPC) architectures do not include support for circuit-switched
voice and video calls. Two complementary tracks have emerged in the telecom industry to provide
interoperable voice services in LTE smartphones: circuit-switched fallback (CSFB) (see Appendix,
fact box 1) and VoLTE. Typically, CSFB is suitable for use in areas with spotty LTE coverage (in
the early phases of LTE deployment or in rural areas), while VoLTE is introduced in areas of
continuous LTE coverage (in metropolitan areas or in mature LTE markets).
BENEFITS OF IMS-BASED VOLTE
The term VoLTE comes from the GSMA profile for voice and SMS in LTE [1], which has its origins
in the 3GPP IMS-based multimedia telephony (MMTel) solution. With VoLTE, operators can make
use of the wider capabilities of IP-based networks to deliver high-capacity mobile-broadband
services and launch interoperable communication services. VoLTE is a foundation for a modern
user experience including services like HD voice, video calling, HD conferencing, IP messaging
and contact management (as specified in GSMA’s Rich Communication Services program [2]),
as well as new innovative services – all available anywhere, on any device.
VoLTE was first launched in South Korea in August 2012. Since then, a wide ecosystem of
VoLTE-capable devices has developed, and operators around the world have planned for the
next wave of launches. During 2014, a wider number of other operators in Asia and North America
launched nationwide VoLTE services, and a large number of operators across the globe are
planning to deploy them in 2014-2015.
With IMS/MMTel as the base for VoLTE, operators can evolve their voice services and add
video calling – described in the GSMA specification for IMS conversational video [3]. VoLTE can
leverage the world’s largest mobile user community (the Mobile Subscriber Integrated Services
Digital Network - MSISDN), as well as traditional telecommunication principles such as guara
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