Using direction and elapsed-time information to reduce the wireless cost of locating mobile units in cellular networks

This paper proposes the use of easily-obtainable information to reduce the "wireless" cost of locating mobile units in cellular communication networks. This comprises the direct cost of searching for them in different cells upon arrival of calls, as well as that of occasional position-updates issued by the units to reduce the number of cells that need to be searched. The direction of motion at the time of last update is used to construct an asymmetric distance-based reporting boundary and, in conjunction with the elapsed time since the latest position-update, to optimize the search order. For a Markovian motion model along a straight line and known motion parameters, optimal algorithms are provided. The results suggest that substantial savings may be attained in common demanding situations such as commuter traffic in congested corridors.