EPS Fallback, is a mechanism used in early deployment stages of 5G network, when the 5G network is still not ready to handle voice and video calls of the UEs.

EPS Fallback allows the 5G network to move the UE to the 4G network, in case this UE needs to initiate or receive a voice or a video call.

When a 5G UE initiates or receives a call while connected to the 5G network, the 5G network will fallback this UE to the 4G network, in order to initiate or receive this call through the 4G network.