Improving end-to-end delay for real-time multimedia traffic in mobile ad-hoc networks
Boshoff, Jacobus Nicolaas
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Mobile Ad-hoc Networks (MANETs) are infrastructure-less, self-organizing wireless networks. Nodes in these networks are able to communicate in the absence of access points, via single-hop or multi-hop paths on a peer-to-peer basis. Efficient routing in MANETs remains a big challenge due to the dynamic and uncertain nature of these networks, as well as the limited and continuously altering energy resources and bandwidth of mobile nodes. MANET routing protocols have to be lightweight due to the limited processing power and memory resources of mobile nodes, and have to be able to adapt quickly to dynamic changes in network topology. A large number of proposed protocols use the number of hops between a transmitting source node and a receiving destination node as metric to select a suitable route. The route with the least hops is thus used. For real-time traffic, and especially in a congested network, the route with the least number of hops can not be assumed to provide the best Quality of Service (QoS), since queuing time at one node may be orders higher than at another. Furthermore, since depending on the Medium Access Control protocol, the physical environment and the distance between communicating nodes, amongst others, the available bandwidth provided by a specific link can hardly ever be guaranteed. In this research a QoS extension of the Ad hoc On-demand Distance Vector (AODV) routing protocol is proposed, implemented and tested in OPNET Modeler. First, the metric for selecting routes is changed to end-to-end delay, and secondly, the protocol is extended to a multi-path protocol. Both extensions realize much lower end-to-end delay for application packets than AODV, and especially the multi-path extension with which all end-to-end delay are lowered to less than the maximum allowed delay for real-time traffic as recommended by the ITU-T. In most scenarios, the average packet delay variation, packet delivery fraction and routing overhead are improved by the final version of the AODV extension, and the overall protocol performance is also better than that of DSR, OLSR and DYMO.
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