Understanding voice over LTE

Beth Schultz
31 Jan 2011

Voice over LTE (VoLTE) is the ascendant method for delivering standardized voice and Short Message Service (SMS) text messages over next-generation 4G wireless broadband Long-Term Evolution (LTE) networks.

Voice over LTE began as the One Voice Initiative, established by a select group of mobile operators and suppliers that wanted to ensure interoperable LTE voice and messaging. The One Voice creators based their LTE voice work on IP Multimedia Subsystem (IMS) specifications developed by 3rd Generation Partnership Project (3GPP), a telecom body developing and ratifying LTE standards.

IMS is widely used to carry voice over IP (VoIP) in fixed-line networks. The One Voice VoLTE technical profile covers the device, the LTE access network, the Evolved Packet Core network and IMS.

Initially the One Voice Initiative was a collaboration among AT&T, Orange, Telefonica, TeliaSonera, Verizon Wireless, Vodafone, Alcatel-Lucent, Ericsson, Nokia.

Nokia Siemens Networks, Samsung and Sony Ericsson. Its purpose was to use current open standards to define the minimum mandatory functionalities for interoperable IMS-based voice and SMS over LTE.

In early 2010, the GSM Association, a global mobile industry association, endorsed the One Voice Initiative as the method it will pursue for carrying voice over LTE. It has expanded the initiative to incorporate end-to-end requirements for seamless voice over LTE transport. In particular, GSMA is developing roaming, interconnect and customer-to-network interfaces. Building to the VoLTE standard, mobile operators, network equipment vendors and handset makers should be able to ensure compatibility of LTE voice solutions.

Why you need to know about Voice over LTE

The GSMA is the mobile industry's kingpin, with at least 80% of mobile subscribers worldwide receiving service over member networks, said Stéphane Téral, a principal analyst with Infonetics Research. That makes the GSMA's backing of the IMS-based LTE voice standard no small thing. Mobile operators now have IMS as a technology directive for supporting voice and SMS over next-generation, IP networks and will need to begin plotting their voice to LTE evolutions. Likewise, network vendors and handset suppliers have early specifications to support.

What you need to know about Voice over LTE

While more than 20 mobile services providers plan to have LTE networks up and running by the end of this year, according to the Global mobile Suppliers Association (GSA), voice is not an initial concern for most, Téral said. Rather, their motivation for deploying LTE is to offload heavy data users and relieve congestion on 3G networks. For the next five years or so, most mobile services providers will continue carrying voice and SMS over traditional 2G circuit-switched networks, leaving 4G innovation mostly for data services, he said.

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