摘要：The integration of heterogeneous wireless access technologies has numerous issues for multimedia applications, such as to smoothly continue over new connections without any service disruption during vertical handovers. We propose State-Aware Feedback extension to Datagram Congestion Control Protocol (DCCP) that meets QoS requirements of multimedia applications throughout the handover process. We consider movement of mobile subscribers among heterogeneous access technologies from highly unstable to more stable environment and model their mobility patterns as Uniform, Pareto, and Exponentially distributed. We present detailed analysis on the performance of proposed mechanism in terms of resuming transmissions during the handover process. In particular, we propose Markov model of TFRC capturing TCP timeouts, loss rates, and no-feedback timer expirations. We validate the proposed analytical model through simulations and show that it accurately predicts various congestion events that may happen during the handover process. We then evaluate the performance of S-TFRC via both simulations and analytical model and observe the sender rates and throughputs achieved. We also consider transmission delays and transmission rates as performance metrics and compare performance of S-TFRC with the standard TFRC. Our results show that S-TFRC is capable of providing better QoS to multimedia applications than standard TFRC by significantly reducing transmission delays and provides better throughput to multimedia applications.
