Assured Forwarding in Multi-hop Wireless Networks

The Assured Forwarding (AF) service in a differentiated services network offers different levels of forwarding assurance for IP packets. Several studies have proposed to manipulate the contention window size to provide service differentiation in wireless networks. However, since network congestion in multi-hop wireless networks causes packet losses at the link layer the contention window size based differentiation scheme is not sufficient to provide the AF service. In this paper we propose a rate control scheme to control load on the shared channel by adjusting sending rate according to the estimated channel state and the amount of AF traffic. We further propose a RTS retry limit adaptation scheme to compensate the rate control scheme when the accurate estimation of the channel state is not easy. Throughout extensive simulations, we show that proposed schemes are effective to differentiate forwarding assurance in multi-hop wireless networks.