EE has announced it will trial voice calls and texts using Wi-Fi and 4G connections as it looks to greatly improve the quality and reliability of its network.
The VoLTE trials, taking place in rural Oxfordshire, form part of a £275m investment in voice capabilities by the operator as it looks to remove so-called 'whitespots', which receive poor or no coverage, and also improve the reliability and quality of calls in busy urban areas.
The Wi-Fi service will launch on compatible handsets in autumn 2014, with EE hoping to launch the 4G calling service in 2015 when it hopes its network will be able to reach 90% of the UK population (as it currently reaches 72%).
Both services will use the low-frequency 800Mhz spectrum acquired by EE in last year's auction for the first time, and follow months of research at the company's Borehamwood test centre.
The carrier grade service will allow people to make calls, with a higher quality and greater degree of reliability than unmanaged VoIP services, from their home, office, corporate or public Wi-Fi connection. Calls can be made through the phone's native dialler, with no need to rely on an app. Native SMS services are also available through the Wi-Fi capability.
Fotis Karonis, CTO at EE, said: "Our Wi-Fi calling capability will let customers make calls where they have access to Wi-Fi but not to the mobile network.
"The customer experience is seamless because it's the same as making a network call and uses the normal call interface of the handset. This is a major part of our strategy to invest in giving customers the ability to make a call wherever they are, and we're confident that this service can make a big difference to people in homes and large offices across the country, especially in the most rural areas, that don't have mobile coverage."
EE is also upgrading more than 6,000 2G sites as part of the investment, and will also be increasing the capacity of 2,000 3G sites around the UK. The company invested a similar amount last year as it looks to improve its network coverage and stability for the 900m calls made by its 26m UK customers every week.