Carriers are aiming to introduce a network upgrade called voice over LTE as early as next year.

These handsets will be enabled with voice over LTE VoLTEfeature.

In June 2014, KT showcased the world's first cross-border roaming services based on Voice over LTE.

The internet-calling function is tentatively named VoLTE, for Voice Over LTE.

Figure 4: VoLGA: Voice over LTE via Generic Access .

Voice over LTE (VoLTE)

Until last year, carriers were mostly using older networks and technologies to carry voice calls, but now everything's moving to voice over LTE, or VoLTE.

As such, for long-distance calls even features such as Voice over LTE and HD Voice may not improve things.

Some audio-quality enhancing features, such as Voice over LTE and HD Voice, have appeared and are often available on newer smartphones.

The company is also a member of the GSMA's RCS and VoLTE (Voice over LTE) initiative.

The S III was the first smartphone to support Voice Over LTE with the introduction of HD Voice service in South Korea.

It is unknown when Sprint will implement Voice over LTE on its Spark network although CEO Marcelo Claure has committed to a VoLTE launch in the future.

Kineto provides software and services to major wireless infrastructure and device vendors to enable the development of products compliant with the leading 3GPP Fixed-Mobile Convergence and Voice over LTE standards.

The GSMA's VoLTE initiative, which is focused on developing a single common solution for providing voice over LTE, now has more than 80 participants from the world's mobile operator and vendor community.

Single Radio Voice Call Continuity (SRVCC) provides an interim solution for handing over VoLTE (Voice over LTE) to 2G/3G networks.

In addition to allowing people to make calls and use applications at the same time, Verizon says the service, called voice over LTE, or VoLTE, also features better sound quality than traditional landline and cellphone calls.

In September 2014, it began offering "Advanced Calling 1.0" service (also called "HD Voice" in the industry) via voice over LTE within its own footprint, and regular calling via roaming on other carriers.

The lack of software support in initial LTE devices as well as core network devices however led to a number of carriers promoting VoLGA (Voice over LTE Generic Access) as an interim solution.