Abstract: This paper mainly aims in the improvement of the congestion control mechanism over mobile WiMAX .Here, TCP sender side mechanisms are used to handle higher load, random loss of packets and retransmission timeouts in high delay networks in such a way as to keep the maximum size of congestion window, while keeping the control over congestion and retransmissions at a minimal level. The TCP proposed mechanisms are assessed against TCP Reno, TCP SACK and TCP FACK to see how they fair against congestion and higher offered load. Ns2 simulator has been selected as the simulation tool because of the ease of use of the graphical interface provided, extensive support of TCP and the free license availability

Keywords: WiMax, TCP Reno, TCP SACK, TCP FACK, NS2 Simulator