IMS stands for IP Multimedia Subsystem. It is a core network architecture that transitions traditional cellular services from circuit-switched domains to packet-switched IP networks. Engineers rely on this framework to route Voice over LTE, video calling, and rich communication services directly through the data network using SIP protocols.
The voice calls keep dropping to 3G because the device is failing to register with the IMS core.
Troubleshooting VoLTE and Wi-Fi calling failures almost always starts with checking the SIP signaling within the IMS core.
Related terms
Voice over IP
A technology that delivers voice communications and multimedia sessions over Internet Protocol networks.
PSTN
The global infrastructure of circuit-switched telephone networks operated by national and regional carriers.
Cellular
Relating to a network architecture that divides a geographic area into multiple radio coverage zones.