A cross-layer support for TCP enhancement in QoS-aware mobile ad hoc networks

In Mobile Ad-hoc Networks (MANETs), the majority of protocols developed to date provide QoS mechanisms by assigning high priority to delay-sensitive applications. While today's Internet traffic is still dominated by TCP based applications, the negative effects of the IEEE 802.11e service differentiation scheme on TCP performance in the presence of high priority traffic have not been widely reported in the literature. This paper presents the results of simulation based experiments designed to investigate these issues and how they can be addressed. In this paper we first evaluate the performance of TCP in 802.11e MANETs when competing with high priority VoIP traffic. We then propose a novel TCP-friendly scheme, called IEDCA, to improve IEEE 802.11e EDCA mechanism by assigning the highest priority to TCP acknowledgement packets. Our results show that the proposed scheme improves TCP performance significantly while having very negligible effects on voice traffic.