## Abstract

Given a set of m mobile objects in a sensor network, we consider the problem of finding the nearest object among them from any node in the network at any time. These mobile objects are tracked by nearby sensors called proxy nodes. This problem requires an object tracking mechanism which typically relies on two basic operations: query and update. A query is invoked by a node each time when there is a need to find the closest object from it in the network. Updates of an object's location are initiated when the object moves from one location (proxy node) to another. We present a scalable distributed algorithm for tracking these mobile objects such that both the query cost and the update cost is minimized. The main idea is that given a set of mobile objects our algorithm maintains a virtual tree of downward paths pointing to the objects. Our algorithm guarantees an O (1) approximation for query cost and an O (min { log n, log D }) approximation for update cost in the constant-doubling graph model, where n and D, respectively, are the number of nodes and the diameter of the network. We also give polylogarithmic approximations for both query and update cost in the general graph model. Our bounds are deterministic and hold in the worst-case. Moreover, our algorithm requires only polylogarithmic bits of memory per node. To our best knowledge, this is the first algorithm that is asymptotically optimal in handling nearest neighbor queries with low update cost.

Original language | English (US) |
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Title of host publication | Algorithms for Sensor Systems - 9th International Symposium on Algorithms and Experiments for Sensor Systems, Wireless Networks and Distributed Robotics, ALGOSENSORS 2013, Revised Selected Papers |

Publisher | Springer Verlag |

Pages | 260-277 |

Number of pages | 18 |

ISBN (Print) | 9783642453458 |

DOIs | |

State | Published - 2013 |

Externally published | Yes |

Event | 9th International Symposium on Algorithms and Experiments for Sensor Systems, Wireless Networks and Distributed Robotics, ALGOSENSORS 2013 - Sophia Antipolis, France Duration: Sep 5 2013 → Sep 6 2013 |

### Publication series

Name | Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) |
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Volume | 8243 LNCS |

ISSN (Print) | 0302-9743 |

ISSN (Electronic) | 1611-3349 |

### Conference

Conference | 9th International Symposium on Algorithms and Experiments for Sensor Systems, Wireless Networks and Distributed Robotics, ALGOSENSORS 2013 |
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Country/Territory | France |

City | Sophia Antipolis |

Period | 9/5/13 → 9/6/13 |

## ASJC Scopus subject areas

- Theoretical Computer Science
- General Computer Science