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Presented By:
Samarth H. Shah, Kai Chen, Klara Nahrstedt Department of Computer Science University of

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I. INTRODUCTION
Available bandwidth estimation is a vital component of admis¬sion control for quality-of-service (QoS) in both wireline as well as wireless networks. In wireless networks, the available bandwidth undergoes fast time-scale variations due to channel fading and error from physical obstacles. These effects are not present in wireline networks, and make estimation of available bandwidth in wireless networks a challenging task. Furthermore, the wireless channel is also a shared-access medium, and the available bandwidth also varies with the number of hosts contending for the channel.
Wireless last-hop networks employing the IEEE 802.11 protocol in Distributed Co-ordination Function (DCF) mode are becoming increasingly popular. In DCF mode, the 802.11 protocol [1] does not require any centralized entity to co-ordinate users' transmis¬sions. The MAC layer uses a CSMA/CA algorithm for shared use of the medium. In this extended abstract, we present an available bandwidth estimation scheme for IEEE 802.11-based wireless networks. Our scheme does not modify the CSMA/CA MAC protocol in any manner, but gauges the effect ofphenomena such as medium contention, channel fading and interference, which influence the available bandwidth, on it. Based on the effect of the phenomena on the working of the medium-access scheme, we estimate the available bandwidth of a wireless host to each of its neighbors .

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