Efficient Valid Scope Computation for Location-Dependent Spatial Queries in Mobile and Wireless Envi...
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Ken C.K. Lee, Wang-Chien Lee, Hong Va Leong, Brandon Unger and Baihua Zheng, ICUIMC’09 Manu Shukla PowerPoint PPT Presentation


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Efficient Valid Scope Computation for Location-Dependent Spatial Queries in Mobile and Wireless Environments. Ken C.K. Lee, Wang-Chien Lee, Hong Va Leong, Brandon Unger and Baihua Zheng, ICUIMC’09 Manu Shukla August 2, 2009. Introduction.

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Ken C.K. Lee, Wang-Chien Lee, Hong Va Leong, Brandon Unger and Baihua Zheng, ICUIMC’09 Manu Shukla

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Ken c k lee wang chien lee hong va leong brandon unger and baihua zheng icuimc 09 manu shukla

Efficient Valid Scope Computation for Location-Dependent Spatial Queries in Mobile and Wireless Environments

Ken C.K. Lee, Wang-Chien Lee, Hong Va Leong, Brandon Unger and Baihua Zheng, ICUIMC’09

Manu Shukla

August 2, 2009


Introduction

Introduction

  • Mobile clients access information with respect to their location by submitting Location Dependent Spatial Queries (LDSQ) to Location-Based service servers

  • Due to limited mobile bandwidth and limited client battery life, frequent LSDQ submission must be avoided

  • Authors define the concept of valid-scope, a spatial area in which a set of LSDQs will retrieve exactly the same query results

  • Propose algorithms for valid scope computation for common LDSQs like range query and NN query


Valid scope

Valid Scope

  • Determine a small and representative subset of non-result objects called “complementary objects” together with result objects

  • Use R-tree and best first search


Valid scope for nn query

Valid Scope for NN Query

  • Objects that contribute the bisector as voronoi cell perimeter are added to complementary objects

  • Exploit the largest empty circle property


Nn query

NN Query

  • Two steps to determine the NN query result and the valid scope of the result and one index lookup

    • First retrieve the nearest object

    • Examine non-result objects to refine valid scope


Valid scope for knn query

Valid Scope for kNN Query


Valid scope for range query

Valid Scope for Range Query

  • Minkowski region is defined as

  • Valid Scope is computed as an area equal to the intersection of the Minkowski regions of all result objects


Range query

Range Query

  • Formula for valid scope can be defined as


Experiments

Experiments

  • Compared with time-parameterized query method by Zhang et.al

  • Three data sets, real and two synthetic based on Gaussian and Uniform distribution


Experiments1

Experiments

  • Overhead incurred by valid scope computations


Conclusions

Conclusions

  • Valid for spatial queries in mobile environment where bandwidth and battery power in mobile devices are limited

  • Most calculations done on server and hence scalable


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