T-Mobile will soon require all phones on its network to support 4G Voice over LTE (VoLTE) in an effort to free up spectrum.

Some US carriers still support older protocols, such as 3G, despite how ubiquitous 4G has become. Supporting those older protocols, however, ties up valuable spectrum that can be used to enhance 4G coverage, as well as help with 5G rollouts.

In an effort to free up some of that spectrum, T-Mobile plans on requiring all new phones activated on its network to support VoLTE by August 4. A document Android Police obtained also indicates that older devices will no longer work on the magenta carrier by January 2021.

While T-Mobile did not confirm the dates listed in the document, they did give the following statement to Android Police:

”We’re making great progress building a truly transformative nationwide 5G network. As part of that, we will be phasing out some older technologies over time to free up even more capacity for LTE and 5G. In preparation for that and to give customers the best experience, those activating new lines at T-Mobile will need a VoLTE capable device, which is all we’ve offered for years now and represents the overwhelming majority of devices on the network.”

Verizon and AT&T are both taking similar measures to retire their older networks. In the race to 5G, spectrum is the most valuable commodity, and retiring older technologies will help the carriers and their customers move forward.