This document provides an overview of Voice over LTE (VoLTE) including its history, requirements, architecture, and advantages. It discusses how VoLTE allows voice calls to be carried over the LTE network rather than traditional circuit-switched networks. Key points covered include VoLTE's improved voice quality and capacity compared to 2G and 3G, its use of quality of service mechanisms to prioritize real-time voice, and fallback options when LTE coverage is unavailable like Circuit Switched Fallback. The document also reviews the end-to-end network architecture and call handling process to enable VoLTE.