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.
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