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A TCP-friendly additive increase and multiplicative decrease (AIMD) protocol is proposed to support time-sensitive applications in hybrid wired/wireless networks. By analyzing the performance of AIMD-controlled flows in hybrid networks, we propose a cross-layer procedure to select the AIMD protocol parameters with consideration of wireless link characteristics and application QoS requirements, in terms of delay, loss, and throughput. Since the cross-layer interaction only exchanges parameters among the application, the transport layer protocol, and the link layer protocol, our approach preserves the end-to-end semantics of the transport protocol and the layered structure of the Internet, and it is applicable to supporting various multimedia applications over heterogeneous wireless links. With appropriate parameters, AIMD-controlled flows can fairly share network resources with TCP flows, efficiently utilize wireless resources, and statistically guarantee end-to-end delay for time-sensitive applications. Extensive simulations are performed to validate the analytical results, evaluate the protocol performance, and demonstrate that the AIMD protocol can outperform the unresponsive UDP protocol when transporting multimedia traffic in hybrid networks. With satisfactory QoS, end systems have more incentives to voluntarily regulate multimedia traffic with an AIMD-based congestion controller, which is vital for network stability, integrity, and future proliferation.
Date of Conference: 13-17 March 2005