United States carrier AT&T said yesterday that some of its customers in select areas can now make Voice-over-LTE (VoLTE) calls to users on other carrier networks. Cross-network VoLTE calls are currently supported for just one unnamed carrier, but AT&T will eventually implement support for multiple carriers.
Unlike traditional calls that use a carrier's voice network (which is separate from a 3G/4G data network), VoLTE calls use a 4G Long-Term Evolution (LTE) network, resulting in crisp sound quality and optimized bandwidth use.