AT&T quietly begins supporting voice-over-LTE calls to other carriers

Cross-network VoLTE calls are currently limited to "select areas," and only when connected to a single unspecified carrier, AT&T said in a brief announcement. Eventually the technology should roll out across the U.S., and cover multiple carriers.

VoLTE is significant to iPhone owners for two reasons, the first being that it enables HD Voice, providing clearer and more natural-sounding calls than those over AT&T's regular voice network.

The technology also improves the bandwidth available for simultaneous voice and app use, which is otherwise capped at 3G speeds.

AT&T is relatively late to cross-carrier support, since T-Mobile has been testing the feature for some time. It did note that some form of VoLTE is now available in 96 percent of its LTE coverage area, which spans large portions of the country.