Location, Localization, and Localizability

With the popularity of wireless networks, location-based service (LBS) has quickly entered people’s daily life. In practice, LBS has a large range of applications and often manifests in various forms in different types of networks. For example, E-911 in the USA, or corresponding E-112 in Europe, offers timely and accurate assis- tance to the emergency callers by locating them through mobile communication networks or global positioning system (GPS). Location information also plays a major role in modern asset management. Some companies, in particular hospitals, have deployed the WiFi-based solutions for real-time equipment locating and tracking, in order to increase equipment utilization and reduce overpurchasing costs. In addition, sensor network, a typical type of wireless ad hoc networks, has shown its great prospects of environmental monitoring, industrial sensing and diagnosis, battlefield surveillance, context-aware computing, and more. Autono- mous localization of sensor nodes is essential since location makes the sensory data geographically meaningful. In all, many applications and services of wireless net- works directly or indirectly rely on location information. This book aims to provide a comprehensive and in-depth view of location- awareness technology in today’s popular wireless networks. However, the obvious diversity of networks, from short-range bluetooth to long-range telecommunication network, makes it very challenging to organize materials. Although general prin- ciples exist, the implementation differs from network to network and application to application. When composing the text, we have been thinking a lot what materials to include and how to organize them. Our thoughts come to the following two decisions. First, from the perspective of application, the book focuses on wireless ad hoc and sensor networks, in which the overwhelming majority of localization techniques are involved. Indeed, the techniques discussed in the book are quite versatile. Other types of networks, such as WLAN and 3G mobile network, are also mentioned. Second, to make it better understood, the book is basically organized around three step-by-step themes: location, localization, and localizability. Location-based applications are close to daily life and accordingly presented at the beginning. Afterward, as the major part of the book, localization approaches are discussed in-depth. Other advanced topics, such as localizability and location privacy, are studied at last.