3G networks provide access to network mobile users at multiple data rates. The lack of mobility support for mobile nodes, by the standard protocols originally developed to meet the requirements of stationary nodes in wired networks, implies that these standard protocols cannot be efficiently implemented in wireless networks. Transmission Control Protocol (TCP) considers packet losses during Vertical Handover transition period as congestion and activates congestion control algorithm as a result thereby degrading throughput. This throughput degradation can be enhanced through improved TCP congestion window adjustment architecture. A proactive approach is presented in this paper wherein congestion window is adjusted according to the new network while handover process is being completed, avoiding slow starts during this process to eliminate the delay in window adjustment for enhanced throughput. Simulation of proposed scheme was carried out in NS-2. Throughput was calculated for proposed scheme during upward vertical handover and downward vertical handover scenarios. The results of proposed scheme were also compared with a split connection and an end-to-end connection approach. The comparative analysis of the results indicate a throughput enhancement of 22% and 17% as compared to split connection and end-to-end connection approach for upward vertical handover whereas throughput enhancement of 37% and 21% as compared to split connection approach and end-to-end connection approach for downward vertical handover is achieved.
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