ABSTRACT
CONTENTS 10.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276 10.2 Theoretical Fundamentals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277
10.2.1 Range Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277 10.2.2 Trilateration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280 10.2.3 Triangulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280 10.2.4 Theory of Network Localization: Localizability
and Rigidity Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281 10.3 Range-Based Localization Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283
10.3.1 Single Hop to Anchors Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283 10.3.2 Multiple Hops to Anchors Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284
10.3.2.1 Iterative and Collaborative Multilateration . . . . . . . . . . . . . . . . . . . 285 10.3.2.2 Sweeping Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285 10.3.2.3 Multidimensional Scaling (MDS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 286
10.3.3 Mobile Anchors Employed Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287 10.3.4 Methods without Anchor Nodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287
10.4 Range-Free Localization Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288 10.4.1 Hop-Count-Based Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288
10.4.1.1 Distance-Vector-Based Localization . . . . . . . . . . . . . . . . . . . . . . . . . . 288 10.4.1.2 Other Improvements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290
10.4.2 Area-Based Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290 10.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
Localization is a fundamental problem in designing wireless sensor networks. Location information can be used in many wireless sensor network applications, such as event detecting, target tracking, environmental monitoring, and network deployment. On the other hand, location information can also be used in different networking protocols to enhance the performance of sensor networks, such as routing packets using positionbased routing, controlling the network topology and coverage using geometric methods, or achieving better load balancing in routing. Manual configuration of locations or providing each sensor with a global positioning system (GPS) is expensive and not feasible for large-scale sensor networks. Therefore, it is important to develop localization methods in which sensor nodes can compute their positions by exchanging information with some nodes∗ that have known locations. This chapter gives an overview of localization methods designed for wireless sensor networks. Both theoretical basics and research challenges for localization will be introduced. Recent solutions from range-based methods to range-free methods will be discussed and compared.With specific hardware, range-based schemes typically achieve higher accuracy based on either node-to-node distance measurements or angle measurements. On the other hand, range-free mechanisms support the coarse-positioning accuracy with less expense. At the end of the chapter, the reader will understand the principal design and new research trends of localization techniques in wireless sensor networks.
