Abstract:
Ad Hoc Network is a decentralized type of network where wireless devices are allowed
to discover each other and communicate in peer to peer fashion without involving central
access points. In most ad hoc networks, nodes compete for access to shared wireless
medium, often resulting in collision (interference). IEEE 802.11, a well-known standard
uses medium access control (MAC) protocol to support delivery of radio data packets
for both ad hoc networks and infrastructure based network. But Designing a Medium
Access Control (MAC) protocol for ad hoc wireless networks is challenging, particularly
when the protocol needs to achieve optimal performance both in terms of throughput
and end to end delay to deliver a packet. Error prone channel has a significant impact
on unsuccessful transmission probability which is often ignored by previous researches.
Standard DCF (Distributed Coordination Function) operation of IEEE 802.11 enacted
by binary exponential back-off cannot differentiate collision from corruption and increases
back-off time through larger contention window (CW) upon a failure. This leads to
increased delay in error prone network when nodes are not contending at all. Since
packet corruption depends on bit error rate (BER) and length of packets, packet size can
have significant impact on the throughput in error-prone environment. In this paper,
we analyze effect of packet size in determining optimal CW to improve throughput and
efficiency for error prone networks. We propose a dynamic learning based scheme to
adaptively select CW confined within a range for different packet distribution. To validate
our scheme extensive simulations have been done and simulation results show significant
improvement in E2E delay performance.
