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TCP performs at an acceptable efficiency over the traditional wired networks where packet losses are usually caused by network congestion. However, in networks with wireless links in addition to wired segments this assumption would be insufficient, as the high wireless bit error rate could become the dominant cause of packet loss and thus TCP performs sub-optimum under these new conditions. As the main reason of this poor performance for TCP we may raise the fact that TCP cannot distinguish between packet losses due to wireless errors from those due to congestion. Moreover, TCP sender cannot keep the size of its congestion window at optimum level and always has to retransmit packets after waiting for timeout, which significantly degrades end-to-end delay performance of TCP. We evaluate the delay and loss recovery performance of a new algorithm named explicit loss notification with acknowledgement. Experimental results show that the proposed scheme improves both throughput and delay performance of TCP in wireless environment significantly.

Due to common usage of the TCP/IP protocol stack in Internet applications that require reliable data transfer, it is important to keep the protocol stack (and also the network element structure) as unchanged as possible even when mobility features required in wireless Internet are added into the network. However, TCP performs poorly in wireless networks running at high bit error rates. In this paper, a new enhancement to TCP based on a previously proposed scheme is introduced. The method is based on the Snoop protocol and is similarly used for fixed host to mobile host direction. The proposed method has been compared with the Snoop protocol and other enhancement protocols proposed for the wireless TCP. It has been shown that the new explicit loss notification with acknowledgement has superior performance to Snoop and other protocols. The proposed method improves the end-to-end reliable transport performance in mobile environments.