# Optical Boundaries for LED-Based Indoor Positioning System
## 1 Introduction  
Indoor positioning forms an integral part in the development of future technologies and its importance in daily activities cannot be overemphasized. Application areas for indoor positioning systems range from smart monitoring of people and facilities in an indoor location to enhanced search and rescue operations during emergencies [1; 2]. As a result, indoor positioning has been the subject of increasing research interest over the past decade. The central idea behind the design of an indoor positioning system is to establish a 'transmitter-receiver communication' link and use a signal parameter to determine the location of the receiver [3]. Using radio frequency (RF) communication channels, ZigBee, Bluetooth, ultra-wideband, and WiFi have all been used to develop indoor positioning systems [4]. However, the possibility of multipath reflections and interference with other RF-based devices makes RF unsuitable for indoor positioning [5]. The use of magnetic or induction-based systems and ultrasound systems has been investigated for indoor positioning, but these systems come with high installation costs [6; 7]. In addition, magnetic systems can interfere with other sensitive electromagnetic signals (such as those in hospitals). Light emitting diodes (LEDs) have been receiving attention recently in the context of positioning due to their cost, lighting characteristics, and ability to communicate. LED-based positioning has beenextensively investigated with major techniques such as received signal strength (RSS) [8], proximity [9], fingerprinting [10], arrival techniques (which include angle of arrival (AoA) [11], time of arrival (ToA), time difference of arrival (TDoA), phase difference of arrival (PDoA), and image-based positioning [3]. The proximity technique has the simplest positioning algorithm and is the most inexpensive to implement, however the accuracy of such systems is usually low [12]. RSS, AoA, fingerprinting, and image based techniques are also popular forms of LED-based indoor positioning with a very high accuracy [13; 14]. Despite the high accuracy these techniques promise, LED-based indoor positioning and indoor positioning in general has been reported as a problem yet to be solved [5]. This is because these highly accurate positioning techniques have been approached with a view to increasing accuracy alone. However, in real life situations, the complexity of the receiver (or mobile unit), the size (weight and volume) of the deployed hardware, the wearability of the receiver, and the positioning time are equally important factors. Ignoring these factors leads to systems that have complex algorithms which are computationally intensive and very expensive to implement [5]. When implemented, the receiver requires hardware of a large size which requires high amounts of electrical power for their operation. Previous works on LED-based positioning which implement their algorithms are presented in Table 1. By the use of heavy and large receiver systems, it can be observed that the wearability of the receiver system has not been properly considered in various indoor positioning system (IPS) design techniques.