optional use of video calling and front and rear-facing cameras. In the future, Verizon's VoLTE is expected to also permit video sharing, chat functionality, and file transfers. See also IP Multimedia Subsystem (IMS), a set of specifications from 3GPP for delivering VoIP and other IP multimedia to cellular users Voice over LTE Fixed mobile convergence Mobile communications over IP Voice over IP VoWLAN — VoIP over a Wi-Fi network VoLGA Forum — Voice over LTE via Generic Access List of SIP software Comparison of VoIP software List of VoIP companies References Voice over IP