TCP cross layer adaptive policy: Throughput optimization over wireless links

Abstract

TCP is the most common transport layer protocol used in Internet. It was designed primarily for wired networks, assuming reliability at lower layers and packet losses are considered as an indication of congestion. The characteristic of wireless links is very different from wired links, particularly in terms of loss behavior. In wireless networks, most packet losses are due to poor link quality and intermittent connectivity, which TCP may falsely assume as congestion. These wrongly trigger the congestion control mechanism of TCP, resulting into end-to-end throughput degradation. The problem is further compounded by the large propagation delay common in such environments. TCP-ACC proposed earlier attempts to combat this problem by adopting a dynamic value of congestion window for the slow start. In this paper, we extend TCP-ACC with the help of a cross layer solution to differentiate between a loss due to congestion and a loss due to noise in the wireless link based on the number of attempts of MAC layer retransmissions.