Spanning a multimedia session across multiple devices

This paper describes an innovative solution that allows a multimedia session to be distributed over multiple devices that are in close proximity to a user. This would typically be useful when a user engaged in an audio/video conference enters a meeting room. Upon entering, all media session components are transferred from the personal digital assistant (PDA) to the projector, Hi-Fi set, and webcam present in the meeting room. When the user leaves the room, all media session components are transferred back to the PDA. Transferring parts of a multimedia session between different devices is defined as partial session mobility (PSM). Numerous methods exist for PSM. None of these methods is directly suitable for initiating PSM from a dedicated network node such as an IP Multimedia Subsystem (IMS) application server, but they do provide a starting point. Because of a number of advantages in the invite-based method, this method is taken as a basis for network-initiated PSM. This paper compares the existing methods, describes the proposed network-initiated method to support PSM, and investigates how to combine it with terminal-initiated PSM. It also describes how PSM could be supported in IMS.