IEEE Transactions on Mobile Computing
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In this paper, we develop a new adaptive scheme inwhich an optimal distance-based update threshold isselected not only as a function of the call-to-mobilityratio, but also as a transitional directivity index w; a newparameter introduced to give some measures of themobile's traveling patterns. It is assumed that when w 1, the mobile has a greater tendency of roaming"outwards" and hence a higher probability of transitionto the next ring during each movement. As a result, thedefined threshold will be reached sooner incurring moreupdate costs. A corresponding sectional paging scheme istherefore proposed to predict mobile's likelihood ofresidency utilizing the information given by the estimatedw . Provided that the prediction of location probability isreliable, a movement pattern with increasing directivitywill justify having increased update thresholds withoutincurring additional paging costs. As far as the mobilitycharacteristics are concerned, the introduction of thedirectivity index has successfully demonstrated its abilityto make optimum decisions on a distance-based updatethreshold. Its advantage becomes even more significantwhen the theoretically determined "ideal" optimalthreshold is not obtainable due to certain restrictionsimposed by the network during times of high systemloading. Simulation results reveal that the additionalinformation made available about a roaming mobile'stransitional directivity could be critical to ensure that thebest available sub-optimal threshold is realizable.