Adaptive location management strategy combining distance-based update and sectional paging techniques

In this paper, we develop a new adaptive scheme in which an optimal distance-based update threshold is selected not only as a function of the call-to-mobility ratio, but also as a transitional directivity index ω; a new parameter introduced to give some measures of the mobile\´s travelling patterns. It is assumed that when ω > 1, the mobile has a greater tendency of roaming "outwards" and hence a higher probability of transition to the next ring during each movement. As a result, the defined threshold will be reached sooner incurring more update costs. A corresponding sectional paging scheme is therefore proposed to predict mobile\´s likelihood of residency utilizing the information given by the estimated ω. Provided that the prediction of location probability is reliable, a movement pattern with increasing directivity will justify having increased update thresholds without incurring additional paging costs. As far as the mobility characteristics are concerned, the introduction of the directivity index has successfully demonstrated its ability to make optimum decisions on a distance-based update threshold. Its advantage becomes even more significant when the theoretically determined "ideal" optimal threshold is not obtainable due to certain restrictions imposed by the network during times of high system loading. Simulation results reveal that the additional information made available about a roaming mobile\´s transitional directivity could be critical to ensure that the best available sub-optimal threshold is realizable.