On the Need of Novel Medium Access Control Schemes for Network Coding enabled Wireless Mesh Networks

This paper advocates for a new Medium Access Control (MAC) strategy for wireless meshed networks by identifying
overload scenarios in order to provide additional channel
access priority to the relay. The key behind our MAC protocol is
that the relay will adjust its back off window size according
to the incoming and outgoing packet ratio. We describe the
new protocol as an extension to the CSMA/CA protocol and
implement the protocol on our own hardware platform. By means
of our own testbed, we investigate two basic network structures,
namely, the two-way relay and the cross topology. It is well known
that network coding will improve the throughput in such systems,
but our novel medium access scheme improves the performance
in the cross topology by another 66 % for network coding and
150 % for classical forwarding in theory. These gains translate
in a theoretical gain of 33 % of network coding over classical
forwarding when both systems implement the improved MAC.
However, our measurement results show an even larger gain for
network coding, namely, up to 65 % over forwarding, as it copes
better with channel losses under high load scenarios.