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3rd International Conference on Mobile Systems, Applications, and Services — Abstract
Pp. 135–148 of the Proceedings
An Overlay MAC Layer for 802.11 Networks
Ananth Rao and Ion Stoica, University of California, Berkeley
Abstract
The widespread availability of 802.11-based hardware
has made it the premier choice of both researchers
and practitioners for developing new wireless networks
and applications. However, the ever increasing set of
demands posed by these applications is stretching the
802.11 MAC protocol beyond its intended capabilities.
For example, 802.11 provides no control over allocation
of resources, and the default allocation policy is ill-suited
for heterogeneous environments and multi-hop networks.
Fairness problems are further exacerbated in multi-hop
networks due to link asymmetry and hidden terminals. In
this paper, we take a rst step towards addressing these
problems without replacing the MAC layer by presenting
the design and the implementation of an Overlay MAC
Layer (OML), that works on top of the 802.11 MAC
layer. OML uses loosely-synchronized clocks to divide
the time in to equal size slots, and employs a distributed
algorithm to allocate these slots among competing nodes.
We have implemented OML in both a simulator and on
a wireless testbed using the Click modular router. Our
evaluation shows that OML can not only provide better
exibility but also improve the fairness, throughput and
predictability of 802.11 networks.
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