BlackBerry Limited
Method and apparatus for setup of a circuit switched call during circuit switched fallback

Abstract:

A method, at a user equipment (`UE`), the method: sending a request to a first network for Circuit Switched Fallback (`CSFB`); receiving, responsive to the request, redirection information; acquiring a second network based on the redirection information; initiating establishment of Circuit Switched (`CS`) voice radio bearers with the second network; waiting for a predetermined event to occur; after the predetermined event has occurred, establishing a Packet Switched (`PS`) connection with the second network. Further, a method, at a network element, the method receiving a request for Circuit Switched Fallback (`CSFB`) from a user equipment (`UE`); sending, to the UE, redirection information; receiving a Routing Area Update (`RAU`) message from the UE; waiting for a predetermined event to occur; upon the predetermined event occurring, responding to the RAU message.