Patent ID: 10492243

Abstract:
A user equipment (UE) and an Internet Protocol (IP) Multimedia Subsystem (IMS) node may exchange fallback indicators in SIP signaling for purposes of controlling fallback procedures implemented by the UE. By sending fallback indicators to an IMS node in a SIP request, a UE is able to inform the IMS node of its capabilities in regards to particular fallback radio access technologies (RATs) that are supported by the UE. The IMS node may respond to the UE with a SIP response that includes information indicating which of the supported Fallback RATs the UE is authorized to use (if any), and which of the supported Fallback RATs the UE is not authorized to use (if any). In this way, the IMS node can control a fallback procedure at the UE by indicating which Fallback RATs are usable by the UE to reattempt communication sessions that cannot be established on an existing RAT.