ViLTE, an acronym for Video over LTE, is a conversational (i.e. person to person) video service based on the IP Multimedia Subsystem (IMS) core network. It has specific profiles for the control and media planes of the video service and uses LTE as the radio access medium. The service as a whole is governed by the GSM Association in PRD IR.94.
Mechanism
ViLTE uses the same control plane protocol as Voice over LTE (VoLTE), namely the Session Initiation Protocol (SIP). The IMS core network along with the applicable Application Server (AS) performs the call control. ViLTE uses the H.264 codec to encode and decode the video stream. The H.264 codec delivers superior quality as compared to the low bit rate 3G-324M codec that is used in 3G conversational video calls.
It is vital that ViLTE video calls are allocated appropriate quality of service (QoS) to differentiate and prioritize this delay and jitter sensitive conversational traffic from other streaming video traffic that is not as delay or jitter sensitive. The mechanism used is called QoS Class Identifier (QCI). The ViLTE bearer traffic is typically allocated QCI=2, and the SIP-based IMS signalling QCI=5.