An Internet Protocol (IP) multimedia subsystem (IMS) network node receives a first collaborative session control signaling from a first wireless transmit/receive unit (WTRU) for an existing IMS collaborative session between at least the first WTRU and a second WTRU. The first WTRU is the initial controller of the session. The IMS network node detects that the first collaborative session control signaling from the first WTRU is degraded, and responsively initiates transfer of control of the session to the second WTRU at least in part by: transmitting an IMS-network-node-initiated collaborative session control transfer request to the second WTRU, receiving an acceptance from the second WTRU, and receiving a second collaborative session control signaling for the session from the second WTRU. The session is maintained, at least in part, through the IMS network node both before and after the second WTRU becomes the new controller.
