Evaluation of adaptive rate control scheme for ad-hoc networks in fading environments

In this research, we investigate the adaptive rate control scheme in the IEEE 802.11 ad-hoc network, and evaluate the performance with ad-hoc on-demand distance vector (AODV) and optimized link state routing (OLSR) in fading environments. The proactive routing protocol such as OLSR constructs all routes between nodes, and changes the route in response to link status. In the fading environment, the link status will change frequently. As a result, poor end-to-end connectivity deteriorates in end-to-end throughput performance. Especially, transmission control protocol (TCP) is a special protocol that is sensitive to segment losses. Therefore, TCP suffers from this poor end-to-end connectivity. The adaptive rate control is one of the methods to improve end-to-end connectivity. However, almost all researchers consider the lower layer performance, not the upper layer performance. Moreover, the criteria for selecting an adequate transmission rate are unclear. In this research, our adaptive rate control scheme intends to improve TCP performance in fading channels over ad-hoc networks. Therefore, our scheme takes TCP performance into account to select the adequate transmission rate for each link. In the numerical results, we evaluate our scheme with AODV and OLSR protocols by using the network simulator QualNet. Finally, we show that our scheme can improve TCP performance greatly.