Fast call set-up for multi-mode communication

摘要

Fast call set-up for a call to a multi-mode communication unit ( 102 ) is facilitated by a method and apparatus for registering and re-registering priorities with a SIP registrar ( 111 ). A list of contacts with first priorities associated with a mode of operation in a first enterprise network ( 106 ) is established and used. A switch to second priorities is made when a probability of a switch from the first mode of operation to a second mode of operation in a second cellular network ( 108 ) satisfies a threshold. The list of contacts includes a contact having an expiration time for the first mode of operation. A quality factor is determined and the list of contacts is re-registered and the expiration time changed if the quality factor does not satisfy a threshold.