Nearly 40 percent of voice calls on T-Mobile's (NYSE:TMUS) network are transmitted via Voice over LTE (VoLTE), illustrating how aggressively the carrier is pursuing the technology. Just last month, T-Mobile said roughly 33 percent of voice traffic was routed through VoLTE.

T-Mobile became the first major U.S. carrier to launch VoLTE in May 2014, when it offered only three supporting handsets. In a blog post citing its 2015 network milestones, CTO Neville Ray said increasing VoLTE penetration and a growing portfolio of compatible devices have helped drive usage.

"And we've built on our investments in nationwide VoLTE to bring the age-old text message and voice call into the mobile Internet era," Ray wrote. "Earlier this year, we were first to launch RCS-based Advanced Messaging… then we added native Video Calling, which our customers can enjoy on their compatible phones right out of the box."

Rather than using traditional circuit-switched networks, VoLTE sends voice calls over IP-based LTE networks that are primarily used for data transmissions. While the caller is likely unaware which technology is being used, VoLTE provides improved audio clarity thanks to HD Voice technology. VoLTE technology can also be used for video calling and voice-over-Wi-Fi calling.

AT&T (NYSE: T) and Verizon (NYSE: VZ) have also pursued VoLTE aggressively; Sprint (NYSE: S) has yet to reveal any plans to deploy VoLTE, apparently preferring to pursue Voice over Wi-Fi.

"Although VoLTE is still at a nascent stage and has its own inherent set of limitations, the adoption rate of VoLTE is rapidly increasing, such that it is not far away from emerging as the industry standard," Zacks Equity Research observed last week. "With competition in the saturated U.S. telecom market heating up, the telecom operators will now look to attract customers through the VoLTE service. However, we are also curious about Sprint's plans to combat the VoLTE thing with Vo-WiFi and offer a challenge to its peers."

Ray also cited T-Mobile's rollout of Extended Range LTE, which has enabled the company to activate LTE-Advanced technology and leverage "carrier aggregation." The strategy provides a large band of spectrum through multiple smaller bands, which can increase network speeds dramatically.

"Customers get rock-solid low band reliability combined with great mid-band performance and faster data speeds all around," wrote Ray. The result is "a network experience that's greater than the sum of its parts."

T-Mobile offers 18 devices that support carrier aggregation, he noted. Verizon, AT&T and Sprint are all in various stages of deploying carrier aggregation as well.

For more:

See this T-Mobile blog post

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