Abstract. Conventional TCP in wireless environment has a lack of ability to differentiate the packet losses caused by network congestion from those caused by wireless link error. When the packet losses are due to wireless link error, TCP performance degradation occurs because of its congestion control mechanism. This paper propose a sender-side TCP scheme for discriminating the cause of packet losses. Simulation results show that it outperforms existing TCP congestion mechanisms such as WestwoodNR, TCP New Jersey, and TCP Reno in terms of goodput performance in wireless links.