An Optimal Rate Adjustment Algorithm for Medium Access Control Protocol in 802.11 Multi Hop Ad Hoc Networks

Problem statement: Medium Access Control (MAC) protocol plays an important role in providing a fair and efficient allocation of limited bandwidth in wireless LANs. In IEEE 802.11 standard protocol, data rate selection is not specified. Rate control is the process of switching data rates dynamically based on channel conditions, with the target of selecting the rate that will provide the maximum throughput feasible for a given channel condition. The two major components of the rate control process are Channel estimation and rate selection. Although rate control has been studied extensively for wired networks, these results cannot be directly applied to multihop wireless networks. Approach: In this study, we propose to develop an Optimal Rate Adjustment Algorithm (ORAA) which is based on the channel state conditions. We also follow a two level channel estimation one at the receiver end and another at each intermediate node along the path. Results: By simulation results we show that our proposed ORAA achieves high throughput and fairness, when compared with the standard IEEE 802.11 MAC protocol. Conclusion: In ad hoc networks, where the channel conditions are dynamic, our proposed ORAA provides the accurate data rate most suitable for the current changes in the network.