Voice over long-term evolution or Voice-over LTE (VoLTE) are the standards in all-IP networks for voice communication as well as data communication over 4G LTE networks.
VoLTE offers services like creating, provisioning and managing high-speed voice, data, multimedia and messaging services on a 4G wireless network for mobile and portable devices. It uses the IP multimedia subsystem (IMS) to deliver the services.
It transmits everything through only packets and thus supports only packet switching. So, all data from any circuit-switched networks like GSM need to be converted to packets before they are transmitted by VoLTE. The communication is depicted in the following diagram −