An in-Depth Survey of Visible Light Communication Based Positioning Systems <s> Proximity <s> In the future, traffic lights, traffic signal devices, and message display boards could all be replaced by Light Emitting Diodes (LED5). Therefore, in addition to their normal function of being an indication and illumination device, LEDs can be used as a communication device for the transmission and broadcasting of information and data. Hence, it becomes part of a wireless optical communication system. It is essentially a new kind of short-range beacon to support vehicle-to-roadside communications. This allows a dual use of traffic lights because it can broadcast local traffic information, vehicle location and navigation information, and simultaneously perform its normal function of being a traffic signaling device. The objective of this technical paper is to present the results from an experiment of using traffic lights as a location beacon, and the bit error rate measurements in an indoor environment. For the covering abstract see IRRD E102946. <s> BIB001 </s> An in-Depth Survey of Visible Light Communication Based Positioning Systems <s> Proximity <s> This paper is in the field of vehicle positioning technology for the intelligent transportation systems. The ideas of an innovative light-emitting diode (LED)-based location beacon system are developed and verified. The system developed is a combination of several latest technologies which include a CMOS vision sensor, high brightness LED, and digital image processing techniques. It belongs to a new kind of simplex communication link. A digital camera is used to capture images contained in the LED beacon signal. The captured digital images are processed by the algorithms developed and a location code is extracted. The location code can be used for calibration of a vehicle positioning system which may consist of a GPS, inertial navigation system (INS) and other sensors. The issues examined include the structure of the transmitter and the receiver, the signaling method, the transmission protocol of the LED panel, the relationship between the camera capturing rate and the LED pattern update rate, the digital camera exposure technology, and the efficiency of the image processing algorithms. Experiments using a prototype transmitter and a receiver were performed. The experimental results provide a good demonstration of the viability of the ideas and methodologies developed. <s> BIB002 </s> An in-Depth Survey of Visible Light Communication Based Positioning Systems <s> Proximity <s> This paper is on a novel use of lighting or signaling devices constructed by light-emitting diodes (LEDs) as a positioning beacon. The idea is that the surface of the LED lighting device is divided into regions and used to show different visual patterns that are not noticeable by the human eye due to the high-frequency switching of the LEDs. A digital camera is used as a receiver to capture a sequence of images of the LED positioning beacon transmitter. Image-processing algorithms are used to decode the location code that is encoded in the visual patterns transmitted by the LED device. This idea can be applied to any LED traffic lights or signaling devices on the road and turn them into parts of a positioning beacon system. Such a system made up of high-brightness visible LEDs can provide the function of open-space wireless broadcasting of the positioning signal. The LED signaling method, transmission protocol, camera frame rate, LED flash rate, together with an implemented system and the experimental results, are presented in this paper. <s> BIB003 </s> An in-Depth Survey of Visible Light Communication Based Positioning Systems <s> Proximity <s> After a public experiment of the indoor guidance system using FLC (fluorescent light communication), we found that FLC provides a promising medium for the installation of a guidance system for the visually impaired. However, precise self-positioning was not satisfactorily achieved. In this article, we propose a new self-positioning method, one that uses a combination of RFID (radio-frequency identification), Bluetooth and FLC. We analyzed the situation and developed a model that combined the three communication modes. Then we performed a series of experiments and get some results in the first step. <s> BIB004 </s> An in-Depth Survey of Visible Light Communication Based Positioning Systems <s> Proximity <s> Indoor positioning system based on visible light communication (VLC) identifier (ID) and 6-axes sensor (geomagnetic sensor and gravity acceleration sensor) has higher accuracy than simple VLC-ID based positioning system1. In this paper, we propose a switching estimated receiver position (SERP) scheme for the VLC-ID and 6-axes sensor based positioning system. The SERP improve the positioning accuracy by optimizing estimated error distance, which is varied in proportion to the receiver's tilt angle. We performed an experiment to confirm the improvement of SERP with three types of field of view (FOV) receivers. As a result, more than 30% improvement of accuracy is achieved comparing with the conventional position estimation scheme. <s> BIB005 </s> An in-Depth Survey of Visible Light Communication Based Positioning Systems <s> Proximity <s> The authors focus on the improvement of Visible Light Communication Identification (VLID) system that provides positioning information via LED light bulb, which is a part of Visible Light Communication (VLC) system. The conventional VLID system provides very low positioning estimation accuracy at room level. In our approach, neither additional infrastructure nor modification is required on the transmitter side. On the receiver side, 6-axis sensor is embedded to provide 3-axis of Azimuth and 3-axis of Tilt angulations information to perform positioning estimation. We verify the proposed system characteristics by making both empirical and numerical analysis, to confirm the effectiveness of proposed system. We define two words to justify the characteristic of the proposed system, which are Field-of-View (FOV: ψc) Limit and Sensitivity (RXS) Limit. Both FOV and Sensitivity Limits have crucial impact on positioning estimation accuracy. Intuitively, higher positioning accuracy can be achieved with smaller FOV configuration in any system that has FOV. Conversely, based on system characteristics of VLID, we propose a positioning estimation scheme, namely Switching Estimated Receiver Position (SwERP) yields high accuracy even with wide FOV configuration. Cumulative Distribution Function (CDF) of error distance and Root Mean Square of Error Distance (RMSED) between experimental positions and estimated receiver positions are used to indicate the system performance. We collected 440 samples from 3 receivers' FOV configurations altogether 1320 samples within the experimental area of 1200mm × 5000mm × 2050mm. The results show that with the proposed scheme, the achievable RMSEDs are in the range of 298 and 463mm under different FOV configurations, which attained the maximum accuracy improvement over 80% comparing to the one without positioning estimation scheme. The proposed system's achievable accuracy does not depend on transmitters' orientation; only one transmitter is required to perform positioning estimation. <s> BIB006 </s> An in-Depth Survey of Visible Light Communication Based Positioning Systems <s> Proximity <s> A simple, accurate, secure, long-lasting, and portable hybrid positioning system is proposed and designed in this paper. It ::: consists of a lighting LED that generates visible light data corresponding to position information of a target and a Zigbee ::: wireless network communication module with low power, security, and service area expansion characteristics. Under an ::: indoor environment where there is 23.62m distance between an observer and the target, the presented hybrid positioning ::: system is tested and is verified with the functions of Zigbee three hop wireless networking and visible light ::: communication (VLC) scheme. The test results are analyzed and discussed. <s> BIB007 </s> An in-Depth Survey of Visible Light Communication Based Positioning Systems <s> Proximity <s> Switching estimated receiver position (SwERP) scheme is proved to be a promising solution for indoor positioning system, owing to its high achievable accuracy and consistency. The high positioning accuracy is achieved from sensitivity ($R_xS$) limit, field-of-view (FOV) limit, and assisted azimuth and tilt information from 6-axis sensor. In this paper, we propose a physical simulation model that can predict the latter three factors. The conventional visible light communication (VLC) model uses only geometric optics (GO) to predict light propagation, which is not enough to define the FOV limit. Thus, we propose a novel method using rotation matrix with cone function and support vector machines (SVMs) to classify the boundary of FOV limit. Based on sensitivity and FOV limits, possible azimuth and tilt angulations are mathematically defined. Moreover, by including FOV limit into the simulation, transmitters and their mirrors that are outside FOV limit can be neglected, of which reduce at least 80 \% of computation during GO calculation. <s> BIB008 </s> An in-Depth Survey of Visible Light Communication Based Positioning Systems <s> Proximity <s> Two design techniques for more accurate and more convenient hybrid positioning system with visible light communication (VLC) and ad-hoc wireless network infrastructure are proposed, in order to overcome the problems of high estimation error, high cost, and limited service range of the conventional positioning techniques. First method is based on a non-carrier VLC based hybrid positioning technique for applications involving of low data rate optical sensing and narrow-range visible light reception from transmitter, and long-range positioning. The second method uses a 4 MHz carrier VLC-based hybrid positioning technique for a high data rate optical sensing and wide-range visible light receiving from transmitter, and midrange positioning applications. In indoor environments with obstacles where there are longrange 77.314m and mid-range 23.68m distances between an observer and a target respectively, the hybrid positioning systems developed with two design techniques are tested, and measured results are analyzed and presented in this paper. <s> BIB009 </s> An in-Depth Survey of Visible Light Communication Based Positioning Systems <s> Proximity <s> An indoor hybrid localization system is realized and experimented with, using a five-hop Zigbee wireless network and visible light communications in order to improve positioning accuracy and achieve a long-range localization. <s> BIB010 </s> An in-Depth Survey of Visible Light Communication Based Positioning Systems <s> Proximity <s> In this study, we propose an indoor navigation system that utilizes visible light communication technology, which employs LED lights and a geomagnetic correction method, aimed at supporting visually impaired people who travel indoors. To verify the effectiveness of this system, we conducted an experiment targeting visually impaired people. Although acquiring accurate positional information and detecting directions indoors is difficult, we confirmed that using this system, accurate positional information and travel direction can be obtained utilizing visible light communication technology, which employs LED lights, and correcting the values of the geomagnetic sensor integrated in a smartphone. <s> BIB011 </s> An in-Depth Survey of Visible Light Communication Based Positioning Systems <s> Proximity <s> This paper proposes a low cost and complexity indoor location and navigation system using visible light communications and a mobile device. LED lamps work as beacons transmitting an identifier code so a mobile device can know its location. Experimental designs for transmitter and receiver interfaces are presented and potential applications are discussed. <s> BIB012 </s> An in-Depth Survey of Visible Light Communication Based Positioning Systems <s> Proximity <s> In recent years visible light communication (VLC) has been matured as an emerging wireless optical technology. Main attraction of VLC is its dual functionality of providing illumination and data from the same light bulb. VLC has been considered for many application areas for its unique characteristics, where this work introduces VLC for novel indoor positioning and navigation architecture. To establish this novel architecture, VLC ID transmission method with digital mapping has been introduced. Proposed solution provides accurate and reliable positioning by using dual functionality light bulbs without installation of additional hardware infrastructure in the buildings. Additionally, this work shows a VLC augmented architecture with existing wireless radio frequency (RF) technologies for indoor tracking applications. <s> BIB013 </s> An in-Depth Survey of Visible Light Communication Based Positioning Systems <s> Proximity <s> In this study, we propose an indoor navigation system that utilizes visible light communication technology, which employs LED lights and a geomagnetic correction method, aimed at supporting visually impaired people who travel indoors. To verify the effectiveness of this system, we conducted an experiment targeting visually impaired people. Although acquiring accurate positional information and detecting directions indoors is difficult, we confirmed that using this system, accurate positional information and travel direction can be obtained utilizing visible light communication technology, which employs LED lights, and correcting the values of the geomagnetic sensor integrated in a smartphone. <s> BIB014 </s> An in-Depth Survey of Visible Light Communication Based Positioning Systems <s> Proximity <s> A system for indoor localization using partially collimated light from individual LEDs inside a luminary is proposed, simulated and tested experimentally. A simple biconvex lens provides angular diversity to the luminary and generates multiple spatially separated regions of overlapping light which can be resolved with a single detector receiver. This approach provides location information without relying on signal intensity measurements, time-of-flight data or complex imaging approaches. The multiple LEDs available in each luminary are exploited to create a large number of uniquely detectable regions, enabling both low positioning error and low complexity. Using a model based on experimental measurements, in a prototypical 5×5×3 m room the average positioning error is 26.0 cm using 4 luminaries and 12.9 cm with 9 luminaries. <s> BIB015 </s> An in-Depth Survey of Visible Light Communication Based Positioning Systems <s> Proximity <s> In wireless communication network, multi-channel communication technology is a promising solution for throughput performance enhancement and collision avoidance. Similarly with visible light communication, multi-channel approach will show more advances due to the limitation of color channel and co-channel interference at the photo detector. In this research, we proposed a new color channel allocation for visible light communication Cell ID based on IEEE 802.15.7 specification. The proposed scheme is based on feedback channel information, channel priority and cognitive technique. We hope that with the flexibility, efficiency, and reliable scheduling of cognitive issue, it proves to a promising technology for future wireless network generally and especially visible light communication. The numerical results and experimental implementation show the enhancement of signal-to-noise ratio, blocking probability, and CCA time. <s> BIB016
The simplest location sensing technique is proximity, which cannot give absolute or relative positions but only proximity location information. In this technique, the proximity location of the mobile device is determined based on the signal from a single LED base station. Each LED base station transmits its identification (ID) code which will be received by the mobile device. Each ID is associated with a specific location of LED base station and this association is stored in a database. When receiving the light from a LED base station with a certain ID, the mobile device will look up the location associated with this ID in the database. The position of the mobile device is then determined as the whole area covered by the light radiated from the found LED base station. Although being simple to implement, proximity has many useful applications. In  a system is presented for tracking the positions of assets like wheelchairs or portable medical devices in a hospital. After detecting the ID of the nearest LED base station, the mobile device sends this information, via ZigBee or WiFi, to the central computer on which is maintained a database of the IDs of the LEDs and their positions. Then, the location of the LED at which the mobile device is currently collocated, or even the map of the corresponding hall is send back to the mobile device. A proximity systems using VLID and Zigbee wireless network were tested in BIB009 BIB007 BIB010 . Firstly, the LED base stations transmitted their VLID to a PD-equipped mobile device. The mobile device transmitted the ID to the center node via a Zigbee wireless network. The center node received the ID and looked for the position corresponding to that ID. Then it transmitted the position information back to the mobile device, also via Zigbee, and thus the mobile device found its proximity. In BIB016 , the visible light Cell-ID was used for channel allocation. In [25] , several realistic VLID based navigation systems used in underground subway stations and in a super market were demonstrated. The report BIB001 , which is one of the first studies on VLC based positioning, proposed the idea of using an 'intelligent' traffic light to transmit signals for vehicle navigation. And BIB002 BIB003 realized this idea by demonstrating an LED location beacon system with which LED panel traffic lights transmit light patterns to the camera-based receiver on the vehicle. Upon receiving and matching the light patterns, the location codes can be obtained. A low cost indoor navigation system using LED lamps to transmit IDs to a PD attached on a smart phone was proposed in BIB012 . The ID then was translated to a location through a correspondence table between ID and location installed on the smart phone beforehand. The data was transmitted using OOK modulation. Manchester coding was employed to prevent flickering. Dimming was achieved through pulse width modulation. Experimental result showed that the position of the smart phone can be determined within a range of 4.5 m. In BIB013 , an architecture of localization using visible light ID and digital mapping is presented. A PD attached to a smart phone was used to receive the light ID. The paper showed that the proposed technique can be used to navigate the person to a desired location, as well as for indoor tracking. An indoor navigation systems for visually impaired people was proposed in BIB011 BIB014 . LEDs installed in the pathway ceiling were used to transmit visible light ID to a portable device worn by the user. After that, the ID was sent to an external server and positional information, for example, latitude and longitude were sent back to the user. The experiment results reported an accuracy of 1-2 m obtained by the system. Fluorescent light was used instead of LEDs in BIB004 , which also presented an indoor positioning system for visually impaired people. In this system, a photodiode was used to receive the position information transmitted from fluorescent lamps installed on the ceiling. Then a PDA would transmit this information to the user through its speaker. Usually, proximity only provides an approximate position of the mobile device, that is the area covered by the LED light. Depending on the system, this coverage area can be quite small as in case of the asset tracking system in the hospital in  , or much larger as in case of the vehicle positioning system in BIB002 BIB003 . In either case, the distance error might be at least a few meters, too far to be accepted for applications that require good positioning. However, with the help from additional devices the estimation accuracy provided by proximity can be substantially increased. In BIB005 BIB006 BIB008 a simple, yet effective method was proposed for using a 6-axis sensor to reduce the distance error of a VLID system down to the range of 300 to 600 mm. The system, as illustrated in Figure 2 , includes a mobile device equipped with a 6-axis sensor and a PD receiving ID signals from an LED base station installed in the ceiling. The 6-axis sensor is capable of measuring the pose of the mobile device in terms of azimuth and tilt angle. To estimate the position, one should directly point the mobile device toward the LED. Given a deliberately small field of view of the PD, the tilting angle of the mobile device, which is measured by the 6-axis sensor, is assumed to approximate the actual angle from the mobile device to the LED. If the height of mobile device H T is known, the horizontal distance D A between the LED and the mobile device can be determined. Figure 3 shows the improvement of the positioning accuracy when using 6-axis sensor. With only data from VLID, the estimated position will be the entire coverage area of the light source as shown in Figure 3a . When the azimuth angle β and the horizontal distance D A , which is determined through the known tilt angle α, are both known, the estimated position will be reduced to much smaller areas as shown in Figure 3b ,c. An advanced proximity system in which multiple LEDs were used to improve positioning accuracy was proposed in BIB015 . In this system, the output light was shaped by placing a converging lens in front of the array of LEDs. Then, several regions of overlapping light were created. Each region was distinguished by the presence or absence of light from specific LEDs. A single PD with wide field of view was used as receiver. The light from each LED was modulated into square waves at different frequencies between 4 kHz and 10 kHz for multiplexing. The experimental results showed that accuracy depended on the number of LEDs as well as the distance between the LEDs and the lens. When the number of LEDs increases, the number of uniquely defined regions also increases and so does the positioning accuracy. For 9 LEDs there were 655 regions within an area of 5 m × 5 m and the average error was 12.9 cm. Besides the high accuracy, this system has the advantage that it does not require the receiver to directly point toward the LED as in BIB005 BIB006 BIB008 . However, this system also has the disadvantage that it might create unwanted contrastive highlight and shadow regions in the floor. 