Low-cost and Simple Configuration Device-free Indoor Localization: A Review

This paper focuses on the review of the recent advancement and development of indoor localization focusing on device-free indoor localization (DFIL). DFIL offers more flexibility for the user or object point-of-view. The basic idea is to free the object from the device attached for localization process. The most popular technologies for DFIL are based on wireless technology. However, if we discuss the low-cost system, we have to discuss the fusion or hybrid of many sensors output data to increase accuracy. Some of the accessible technology used for these low-cost systems are wireless-based, i.e., Wi-Fi, ZigBee, radio frequency identification (RFID) and an optical-based, visible light communication (VLC). Wireless-based probably the most used in the low-cost and simple configuration of an indoor localization since the parameter used can be directly obtained from its device. The most used parameter in the wireless-based system is received signal strength indicator (RSSI), which merely the derivation of power by the distance. By this parameter, the technique such as trilateration, min-max, and RSSI database can be used as the location. In the DFIL, RSSI can be applied as the Wi-Fi -based radio map from two or more links and applying an algorithm such as the Bayes Inference, resulting in the accuracy of object tracking up to 86%. On the other hand, ZigBee applies to mesh network and need more nodes to gather more information for higher accuracy results. The RFID has advantages in no-contact, and a good accuracy even in non-line-of-sight (LoS) condition. Optical-based VLC can provide high accuracy but dependent on the light noise and shadow effect in the object. From these benefits and disadvantages of some low-cost systems, we can make the best of them by fusing the sensor or developing the hybrid system.

I. Introduction

A simple, low-cost, and accurate indoor localization system has been widely applied to obtain a device or user location in an indoor setting [1]. In recent years, indoor device localization has been extensively investigated, especially for Internet of Thing (IoT) applications and swarm robotics [2]–[4]. The massive usage of smart devices, including smartphones and smartwatches, opens opportunities in the development of location-based services (LBS). Especially for commercial use of indoor localization, medical service, emergency events, and other purposes, which cover the utilization of small spaces, in which, Global Positioning System (GPS) performs poorly. Generally, standard indoor localization technology is a device (smartphone-based or tag-based) attached to the entity (target or object); it usually called device-based indoor localization [5]. This system is not suitable in some critical applications such as theft prevention and intrusion detection. Therefore, due to the limited applications, practicality, and flexibility of device-based indoor localization, a device-free system is preferable [6], [7].