Indoor Localization Systems - Tracking objects and personnel with sensors, wireless networks and RFID

摘要

An information system is always expected to provide answers to four types of questions: Who, What, When and Where. Information such as ID, time and incident descriptions can be useless if it is not associated with a physical location. With the growing requirements in mobility of the end devices, a Real-Time Locating System/Service (RTLS) has become an integrant part of many information systems. The most well known localization service is the Global Positioning System (GPS) using a network of 24 beacon satellites to cover the majority of the earth's surface. It is widely used to track and navigate only moving objects outdoors, because its accuracy cannot satisfy most indoor applications and the satellite signal itself is usually unreachable in indoor environment. Thus dedicated systems have to be used for on-site localization. Compared to outdoor applications, the indoor environment is more complex, irregular, unpredictable and inconsistent. Because of this it is very hard for a system to achieve satisfied performance in all the aspects including accuracy, range, power consumption, implementation, cost and maintenance. Most designs have to looking for balance between these parameters. Many new technologies have emerged in the past decade to achieve accurate and reliable tracking of objects within buildings, the performance of indoor localization has improved significantly. Different systems have been designed for various applications. The application scale varies from tracking thousands of objects and personnel in industry and public applications to navigating a single vacuum cleaner in home automation system. The current research in indoor localization technology can be classified in three categories: Non-RF technology, Active-RF technology and Passive-RF technology. The Passive-RF technologies can be further divided into "Mobile tag" and "Mobile reader" systems. For the remaining of this paper we will introduce and discuss the primary technologies based on this classification.