Blackberry Corporation

Christopher Edward Prest

Ximing Zeng

Michael Elizarov

Jerod David Klink

A system, method and mobile device for initiating a voice call from the mobile device is provided. An expiration time is determined based on a time reference synchronized with a mobile call server. The mobile device transmits to the mobile call server a session initiation protocol (SIP) call initiation request including a destination number and the expiration time. A second call initiation request to a secondary contact number is initiated to establish the voice call to the destination number, when a response to the SIP call initiation request is not received from the mobile call server prior to the expiration time enabling reliable establishment of the voice call when the first attempt is unsuccessful. The mobile device does not have to wait on the mobile call server to determine a call failure and ensure that subsequent call initiation by the mobile device does not result in a call establishment collision with the mobile call server.

System, apparatus and method for establishing a call from a mobile device

A method, system and apparatus for managing call handoff are provided. A mobile device engaged in a first media session over a first transport determines a second transport is available. A reflected media session is established via an echo server over the second transport. Quality of the reflected media session is evaluated by determining a call metric based on call transport data received at the mobile device from the mobile device (itself) in the reflected media session. Call handover is requested from the first media session to a second media session over the second transport when the call metric indicates that the quality of the reflected media session meets a threshold.

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Waterloo, Canada

Christopher Edward Prest