LTE was designed from the ground up as a pure packet-switched network with no circuit-switched domain. This all-IP architecture delivers outstanding data performance, but it created a fundamental challenge for voice services. Traditional mobile voice relied on dedicated circuit-switched channels inherited from 2G and 3G networks. Without that circuit infrastructure, LTE needed an entirely new framework to manage call signaling, codec negotiation, session control, and quality of service enforcement for real-time voice communication.