Browsing by Subject "Location management"

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Open Access
Adaptive schemes for location update generation in execution location-dependent continuous queries
(Elsevier Inc., 2006-04) Lam, Kam-Yiu; Ulusoy, Özgür
An important feature that is expected to be owned by today's mobile computing systems is the ability of processing location-dependent continuous queries on moving objects. The result of a location-dependent query depends on the current location of the mobile client which has generated the query as well as the locations of the moving objects on which the query has been issued. When a location-dependent query is specified to be continuous, the result of the query can continuously change. In order to provide accurate and timely query results to a client, the location of the client as well as the locations of moving objects in the system has to be closely monitored. Most of the location generation methods proposed in the literature aim to optimize utilization of the limited wireless bandwidth. The issues of correctness and timeliness of query results reported to clients have been largely ignored. In this paper, we propose an adaptive monitoring method (AMM) and a deadline-driven method (DDM) for managing the locations of moving objects. The aim of our methods is to generate location updates with the consideration of maintaining the correctness of query evaluation results without increasing location update workload. Extensive simulation experiments have been conducted to investigate the performance of the proposed methods as compared to a well-known location update generation method, the plain dead-reckoning (pdr). © 2005 Elsevier Inc. All rights reserved.
Open Access
An efficient method for generating updates in processing location dependent continuous queries
(2001-09) Yoncacı, İlker
Recent advances in wireless communication networks and portable computers have greatly increased the functionality of mobile information services and mobile computing applications. Most of those applications are expected to support location-dependent continuous queries (LDCQs) in the near future. A LDCQ is evaluated continuously in the system for a period of time and the changing results can be transmitted to the requesting client. The result of a LDCQ depends on both the locations of mobile objects on which the query has been issued and the location of the mobile client which has submitted the query. The result of a LDCQ can be provided to the requesting client as a set of tuples < S, begin, end > indicating that object S satisfies the query from time begin to time end. The correctness and timeliness of query results of LDCQs have been studied by employing an adaptive monitoring method (AMM) that manages the locations of moving objects. In this thesis, we propose a Categorized Adaptive Monitoring Method (CAMM) which allows to specify various criticality levels for LDCQs. The aim of CAMM is to provide higher levels of correctness for query results as the criticality of the query increases, without significantly increasing the wireless bandwidth requirements. We provide a simulation model with multiple criticality levels and evaluate the performance of the mobile system and the proposed method with extensive simulation experiments.