MobiQual: QoS-aware load shedding in mobile CQ systems

Abstract

Freshness and accuracy are two key measures of quality of service (QoS) in location-based, mobile continual queries (CQs), However, it is often difficult to provide both fresh and accurate CQ results due to (a) limited resources in computing and communication and (b) fast-changing load conditions caused by continuous mobile node movement, Thus a key challenge for a mobile CQ system is: How do we achieve the highest possible quality of the query results, in both freshness and accuracy, with currently available resources under changing load conditions? In this paper, we form-lale this problem as a load shedding one, and develop MobiQual - a QoS-aware framework for performing both update load shedding and query load shedding. The design of MobiQual highlights three important features. (1) Differentiated load shedding: Different amounts of query and update load shedding are applied to different groups of queries and mobile nodes, respectively. (2) Per-query QoS specifications: The overall freshness and accuracy of the query results are maximized with Individualized QoS specifications. (3) tow-cost adaptation: MobiQual dynamically adapts, with a minimal overhead, to changing load conditions and available resources. We show that, through a careful combination of update and query load shedding, the MobiQual approach leads to much higher freshness and accuracy in the query results in all cases, compared to existing approaches. © 2008 IEEE.