In brief, what is ViLTE all about?

can some explain in brief what ViLTE is all about? What are the major RF parameters in VoLTE optimization and drive test? What is VMOS ? Thanks.

ViLTE refers to Video over LTE,
Video calling service based on the IP Multimedia Subsystem (IMS) or MMTEL or MMTEL As core network.
It has specific profiles QCI 2 for the control and media planes of the video service and uses LTE as the radio access medium.
there are other bifurcation depends on HD Video services based on bandwidth and GBR assign as per eNBs and constaraint