Application Layer Signaling for Proactive Handoff Management in All-IP Wireless Networks

Recently, all-IP wireless systems have been standardized under the IP multimedia subsystem (IMS) framework to support next generation value added mobile services. In all-IP networks, multiple base stations connect to IMS policy servers through IP-based access gateways. As users move from one access gateway area into another, the corresponding access gateways initiate signaling flows for QoS authorization toward the IMS policy server. Depending on the service, the policy function may contact one or more application servers resulting in variable and prolonged signaling delays upon each handoff. Such delays can be of the order of seconds, depending on the specific system design and whether the user is roaming, which maybe critical to the quality of real time services. In this paper, we propose a novel proactive signaling method in the application layer that conveys authorization delay constraints from the IMS to the radio layer and thus mitigates the effects of variable signaling delay. Our method is practically relevant as it uses the already established mechanisms of authentication and authorization signaling via standardized interfaces and protocols. Using the OPNET simulator, we demonstrate that our scheme is also scalable, as its corresponding signaling overhead is upper bounded to approximately double the handoff rate.