Generic adaptive moving object tracking algorithms

Moving Object Databases (MODs), the core component of location server to support location-related applications, keep track of the locations of moving objects which submit location update reports to the centralized server. In resource-limited wireless environments, the frequency and conditions for generating location update messages exert a strong impact on system performance in terms of update message cost and object location accuracy, hence the query result precision. Conceptually, moving objects are the sources of the location data while the MOD caches recently reported object locations for query processing. Owing to the inherent imprecision of the cached values, we impose a bounded level of inconsistency for the cached values, realized in the form of a "safe range" for a moving object. The cached value needs not be invalidated so long as the deviation of the object's current location from its reported location is within the safe range. A smaller safe range results in a higher accuracy of the cached value and hence more accurate query result at the expense of higher update cost, and vice versa. Since the size of the safe range is the key to system performance, we derive a system cost model to determine its appropriate value. Furthermore, to cater for highly dynamic environments in which object movement, query access pattern and system workload always change, we propose two adaptive safe range adjustment algorithms. Through extensive simulation experiments, the benefits brought about by our algorithms are evidenced.