Freshness and Accuracy are the two key measures of quality-of-service (QoS) in the location-based, mobile Continual Query (CQ) systems. The CQ server must receive and process the frequent position updates from the mobile nodes to achieve the accuracy. Also CQ server must perform frequent query re-evaluations to achieve the freshness.
But it is very difficult to get the fresh and accurate CQ results simultaneously, due to the reasons given below:
1. Fast-changing Load conditions due to the continuous mobile node movement.
2. Less resources in computing and communication.
Main objective of the mobile CQ system is to achieve the highest possible quality of the CQ results, in both freshness and accuracy, with currently available resources.
In this paper, we defined this problem as a load shedding one and to perform both query load shedding and update load shedding we developed MobiQual-a QoS-aware approach.
1) Differentiated load shedding: We applied various amounts of query load shedding and updated the load shedding to different groups of mobile nodes and queries respectively.
2) Per-query QoS specification: By using individualized QoS specifications, we can increase the overall freshness and accuracy of the query results.
3) Low-cost adaptation: to change the load conditions and available resources, MobiQual dynamically adapted a minimal overhead.
– are the main important features of MobiQual design.