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

摘要

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.

主权项

1. A method, at a user equipment (‘UE’), comprising;
establishing connection to a first network, wherein transmission of a Routing Area Update (‘RAU’) message initiates a transfer of the connection from the first network to a second network; sending a request to the first network for Circuit Switched Fallback (‘CSFB’); receiving, responsive to the request, redirection information to the second network; acquiring the second network based on the redirection information; initiating establishment of Circuit Switched (‘CS’) voice radio bearers with the second network; determining that the UE has no active Packet Switched(‘PS’) connection; if there is no active PS connection, waiting for a predetermined event to occur following the initiating and before transmitting the RAU message; and after the predetermined event has occurred, establishing the connection with the second network by transmitting the RAU message.