The “Smart World” envisioned by technology will be achieved by the penetration of intelligence into ubiquitous things, including physical objects, cyber-entities, social-elements or individuals, and human thinking. The development of Smart World is enabled by diverse applications of wireless sensor networks (WSNs) into those components identified as things. Such a smart-world will have features controlled significantly by the location information. Control and Policy information of Smart World services, often addressed as location-based services (LBSs), are governed by location data. Localization thus becomes the key enabling technology for Smart World facilities. It is generally classified as active and passive techniques in nature. Active localization is a widely adopted localization scheme where the target is detected and tracked carries a tag or attached device. The other category, Passive methods, defines targets to be localized as free of carrying a tag or device, hence also referred to as device-free localization (DFL) or sensor-less localization. The passive approach is a well suited for the development of diverse smart world applications with ubiquitous localization. DFL schemes fall into a wide range of application scenarios within the Smart World ecosystem. A few notable examples are occupancy detection, identity definition, positioning, gesture detection, activity monitoring, pedestrian and vehicle-traffic flow surveillance, security safeguarding, ambient intelligence-based systems, emergency rescue operations, smart work-spaces and patient or elderly monitoring. In this paper, the revolution of DFL technologies have been reviewed and classified comprehensively. Further, the emergence of the Smart World paradigm is analyzed in the context of DFL principles. Moreover, the inherent challenges within the application domains have been extensively discussed and improvement strategies for multi-target localization and counting approach are discussed. Finally, current trends and future research directions have been presented.

中文翻译：

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无处不在的本地化 (UbiLoc)：智能世界无设备本地化的调查和分类

技术所设想的“智能世界”将通过智能渗透到无处不在的事物来实现，包括物理对象、网络实体、社会元素或个人以及人类思维。智能世界的发展是通过将无线传感器网络 (WSN) 应用到那些被识别为事物的组件中来实现的。这样的智能世界将具有由位置信息显着控制的功能。Smart World 服务的控制和策略信息通常被称为基于位置的服务 (LBS)，由位置数据管理。因此，本地化成为智能世界设施的关键支持技术。它在本质上通常分为主动技术和被动技术。主动定位是一种广泛采用的定位方案，其中检测和跟踪的目标带有标签或附加设备。另一类被动方法将要定位的目标定义为不携带标签或设备，因此也称为无设备定位 (DFL) 或无传感器定位。被动方法非常适合开发具有无处不在的本地化的各种智能世界应用程序。DFL 方案属于 Smart World 生态系统中广泛的应用场景。一些值得注意的例子是占用检测、身份定义、定位、手势检测、活动监控、行人和车辆流量监控、安全保障、基于环境智能的系统、紧急救援行动、智能工作空间和病人或老人监控。本文对 DFL 技术的革命进行了全面的回顾和归类。此外，智能世界范式的出现在 DFL 原则的背景下进行了分析。此外，还广泛讨论了应用领域内的固有挑战，并讨论了多目标定位和计数方法的改进策略。最后，介绍了当前的趋势和未来的研究方向。