Design and analysis of an efficient communication strategy for hierarchical and highly changing ad-hoc mobile networks

• Authors: Ioannis Chatzigiannakis;Sotiris Nikoletseas
• Venue: Mobile Networks and Applications
• Year: 2004

In this work we introduce two practical and interesting modelsof ad-hoc mobile networks: (a) hierarchical ad-hoc networks,comprised of dense subnetworks of mobile users interconnected by avery fast yet limited backbone infrastructure, (b) highly changingad-hoc networks, where the deployment area changes in a highlydynamic way and is unknown to the protocol. In such networks, westudy the problem of basic communication, i.e., sending messagesfrom a sender node to a receiver node. For highly changingnetworks, we investigate an efficient communication protocolexploiting the coordinated motion of a small part of an ad-hocmobile network (the "runners support") to achieve fastcommunication. This protocol instead of using a fixed sized supportfor the whole duration of the protocol, employs a support of someinitial (small) size which adapts (given some time which can bemade fast enough) to the actual levels of traffic and the (unknownand possibly rapidly changing) network area, by changing its sizein order to converge to an optimal size, thus satisfying certainQuality of Service criteria. Using random walks theory, we showthat such an adaptive approach is, for this class of ad-hoc mobilenetworks, significantly more efficient than a simple non-adaptiveimplementation of the basic "runners support" idea, introduced in[9,10]. For hierarchical ad-hoc networks, we establishcommunication by using a "runners" support in each lower level ofthe hierarchy (i.e., in each dense subnetwork), while the fastbackbone provides interconnections at the upper level (i.e.,between the various subnetworks). We analyze the time efficiency ofthis hierarchical approach. This analysis indicates that thehierarchical implementation of the support approach significantlyoutperforms a simple implementation of it in hierarchical ad-hocnetworks. Finally, we discuss a possible combination of the twoapproaches above (the hierarchical and the adaptive ones) that canbe useful in ad-hoc networks that are both hierarchical and highlychanging. Indeed, in such cases the hierarchical nature of thesenetworks further supports the possibility of adaptation.