Implementation of explicit wireless loss notification using MAC-layer information

Abstract

TCP is a reliable transport protocol tuned to perform well in traditional wired networks, where most packet losses are due to congestion. In wireless networks, however, packet losses result from wireless link loss in addition to congestion loss. Thus, TCP suffers a significant degradation in performance over wireless networks because it does not distinguish wireless link loss from congestion loss. To overcome this problem, the explicit wireless loss notification (EWLN) scheme is proposed to explicitly inform wireless link loss to the TCP sender. Previous work to deploy EWLN often lacked explicit specification of the interplay between EWLN and link-layer protocols, including error recovery mechanisms. In addition, many systems, or being based on computation demanding functionality of agents at a base station, were designed for the scenario where information is accessed from a mobile station through a wireless-to-wired connection. In this paper, we present an EWLN scheme that deploys the information from the MAC layer and takes into account the interplay with the error recovery mechanism at the link layer. The scheme does not require different implementations for mobile terminals and base stations and hence can support efficient TCP-based data transmission over wired-to-wireless and wireless-to-wired connections as well as ad-hoc networks. We also present EWLN-enabled TCP implementations which, showed significant improvements over the standard TCP-Reno and TCP-SACK protocols, as evidenced by simulation studies over ns-2 network simulator.