Following the introduction of Voice-over-LTE technology with the iPhone 6 and 6 Plus, which increases call quality by routing calls through an LTE network opposed to last generation 3G networks, US carriers have experienced a big increase in VoLTE calls. That’s according to a new report from Newfield Wireless that highlights a decrease for calls over 3G by about one-fifth compared to previous generation iPhones and other LTE-capable devices:

The majority of voice calls made on other 4G-enabled devices are currently routed through legacy 2G and 3G networks, due to the fact that not all networks and devices are optimised to deliver next-generation voice services. iPhone 6 devices are VoLTE-compatible and as a result, U.S. networks have experienced a surge in VoLTE calls since the September launch.

The report also shared some other data points from its research noting a few stats for iPhone 6 and 6 Plus uptake compared to previous generations:

On average, iPhone 6 and 6 Plus users are already consuming more 4G data than users on all iPhone 5 devices.

The number of iPhone 6 handsets active on mobile networks is 5x the number of iPhone 6 Plus devices.

The majority of iPhone 6 handsets that have appeared on mobile networks have been direct replacements of iPhone 5 devices.

Carriers in the US have already begun rolling out support for VoLTE, and Verizon and AT&T this week announced their plans to introduce interoperability between their customers. Before Verizon and AT&T’s rollout of VoLTE interoperability, the feature only works when making a call to a VoLTE capable device on the same network.

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