Ad hoc wireless routing with density based probabilistic algorithm for mobile wireless networks with non-uniform node distribution
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Date
2010
Authors
Hean Loong, Ong
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Abstract
Ad hoc wireless networks can operate even when there is limited or no network
infrastructure. It is the dynamic and volatile nature of these networks that sets it apart from
existing wireless networks. Current wireless networks could only support communications
one hop away from the infrastructure range. The research presented in this thesis examines
large multiple-hop ad hoc wireless networks that have varying node densities. Such
environments can be can be found in areas struck by disasters to urban city environments.
Mobile nodes would not distribute evenly in such environments but would likely
concentrate around specific landmarks or areas such as public squares with a high number
of pedestrians, \vhile connecting roads and highways have low density of mobile nodes
This thesis introduced three custom mobility scenanos based on the different
density configurations that mimic urban areas, highways or disaster area. The mobility
scenarios were separated into three topologies HD, VD and SD. The node distribution in
the HD topology were concentrated a smaller area. The VD topology has a mixture of
different node distribution across a medium sized area. The node distribution in SD
topology were scattered across a large area.
The mam contribution in this thesis was the integration of a density based
probabilistic scheme on AODV to reduce incurred routing overheads and improve packet
delivery without impacting significantly the throughput and end to end delays. The
proposed AODV-P (Ad Hoc On Demand Distance Vector - Probabilistic) protocol was
compared against the AODV-UU and OLSR-UM (Optimized Link State Routing) protocol
via simulation using NS-2 The evaluation was based on 3 different environments namely
HD, VD, SD for several parameters such as delivery ratio, throughput, normalized routing
overheads, average delays and link lifetime.
The study showed that in varying density environments, the AODV-P has higher
data throughput than AODV -UU in low to medium speeds by 10%. The reduction of
routing overheads for AODV-P is around 60% compared to AODV-UU for varying density
environments. Other parameters for AODV-P also show the performance was fairly close
in terms of average delay (less than 1 second) and average hop counts (around 1 hop). The
link lifetime metric showed AODV-P was able to sustain links better than AODY-UU by
an average of 15 seconds. The overall results showed that AODV-P performed better than
AODY-UU and OLSR in sub-optimal network environments due to the improved link
lifetimes and lower routing overheads.
Therefore a more ubiquitous approach to wireless networking is to be desired,
especially during times when there is a scarcity of infrastructural support. One of the
earliest forms of such ubiquitous networks tested by DARPA was the "packet radio
network". This form of network then began to evolve into what we know today as the
wireless ad hoc networks. The wireless ad hoc networks was built on the same layer two
frame of 802.11 but its very different in terms of routing and network administration. More
significantly is the reduced amount of infrastructure needed to run a local area network and
gives it the advantage in terms of mobility and availability. Ad Hoc Networks could also
communicate over multiple hops based on the routing protocols used. The current wireless
ad hoc networks are categorized into different setups which includes Wireless Mesh
Networks, Wireless Sensor Networks and Mobile Ad hoc Networks. These networks are
different in terms of usage purposes, protocols and functionalities.