When MetroPCS rolled out the country’s first smartphone to route voice calls over an LTE network in August, its primary objective wasn't finding a new way to compete with the big guys.

Instead, its top priority was making the most efficient use of its scarce spectrum resources.

"The initial value proposition … is really about our spectrum constraints and wanting to accelerate the move to LTE. First and foremost, that's our primary objective," MetroPCS network chief Ed Chao said in an interview with Wireless Week.

By moving customers to voice over LTE (VoLTE), MetroPCS will begin to free up spectrum currently used to support voice calls on its 3G network. Once enough subscribers are on VoLTE, MetroPCS will be able to re-farm the spectrum currently used in its CDMA network for LTE, delivering an improved experience to its customers.

In and of itself, VoLTE may not be a huge draw for customers, and for good reason: They probably won't be able to tell a VoLTE call apart from a 3G voice call. The discussion with Chao was conducted over VoLTE and was indistinguishable from a regular phone call.

Chao said VoLTE "provides a foundation for further differentiation" as MetroPCS prepares to launch next-generation Rich Communications Suite (RCS) messaging services this fall. The new messaging products will leverage the capabilities of the company’s IMS infrastructure, a necessary component of its VoLTE service.

Up to seven MetroPCS smartphones currently on the market will be compatible with RCS through the installation of an app set to become available in the coming months. Chao did not specifically state the smartphones would all be Android but said the app would be available through Google Play, which sells applications for Android devices.

Madan Jagernauth, vice president of marketing and strategy for MetroPCS VoLTE vendor Mavenir, agreed with Chao.

"The voice experience is going to be about the same as you had before VoLTE," he said in an interview. "It's really about establishing a basis for the next generation of services, making sure you're as on par with VoLTE as you are with 3G."

Mavenir has a previous relationship with MetroPCS for converged messaging; the operator is using the vendor’s mOne convergence platform to support its VoLTE deployment.

Consumers won't notice much of a change until operators roll out high-definition LTE calls, he said.

"I think when operators introduce HD voice, you'll see a difference," he said.

MetroPCS has HD voice in the works, and it's not the only one. Sprint plans to launch HD voice by the end of this year.

VoLTE paves the way for operators to roll out RCS, technology touted as a way for operators to compete with over-the-top providers. RCS will provide subscribers with a single instant messaging client that works across their phone contacts so they won't have to sign in separately to multiple services like Google Talk, Windows Messaging and Skype.