Improving TCP Performance in Wireless Networks by Detection and Avoidance of Spurious Retransmission Timeouts

Transmission Control Protocol (TCP) is a connection oriented, reliable delivery, transport layer protocol. The performance of TCP is degraded when it is used in wireless networks. This is mainly because of the basic assumption of TCP that any packet loss is an indication of congestion, which is not true in wireless links. The TCP performance in wireless network can be improved by differentiating the wireless losses from the congestion losses. Various Loss Differentiation Algorithms (LDAs) are used to identify whether the packet losses are due to congestion or due to wireless links. The accuracy of wireless loss discrimination and the accuracy of congestion loss discrimination have a trade-off relationship based on their own threshold. The detection information of LDA alone is not sufficient to improve the performance of TCP due to presence of Spurious Retransmission Timeouts (SRTO). In this paper, a novel cross-layer approach, TCP-DDA (TCPDetection, Differentiation and Avoidance) is proposed, wherein the packet losses are differentiated using cross-layer based LDA, SRTO is detected and steps are taken to avoid the SRTO. A new TCP mechanism that is capable of detecting and differentiating the loss of retransmitted packets is also proposed, thereby enhancing the performance of TCP over wireless networks. The work is evaluated using simulation, and the performance improvement is observed by comparing with the existing TCP NewReno.