Trong-Hop Do

An in-Depth Survey of Visible Light Communication Based Positioning Systems

While visible light communication (VLC) has become the candidate for the wireless technology of the 21st century due to its inherent advantages, VLC based positioning also has a great chance of becoming the standard approach to positioning. Within the last few years, many studies on VLC based positioning have been published, but there are not many survey works in this field. In this paper, an in-depth survey of VLC based positioning systems is provided. More than 100 papers ranging from pioneering papers to the state-of-the-art in the field were collected and classified based on the positioning algorithms, the types of receivers, and the multiplexing techniques. In addition, current issues and research trends in VLC based positioning are discussed.

TDOA-based indoor positioning using visible light

In this paper, we propose an indoor positioning system in which the visible light radiated from LEDs is used to locate the position of receiver. Compared to current indoor positioning systems using LED light, our system has the advantages of simple implementation, low cost, and high accuracy. In our system, a single photo diode receives pilot signals from LED panels on the ceiling. Then, the time differences of arrival of these pilot signals are used to estimate the position of the receiver. The system can be employed easily because it does not require embedding any ID to the pilot signal. In the paper, the estimation accuracy of the proposed system is analyzed through the simulation. The causes of estimation error are analyzed, and the estimation accuracy of the system in various conditions is shown by simulations.

TDoA based indoor visible light positioning systems

In this paper, we propose an indoor positioning system in which the visible light radiated from LEDs is used to locate the position of receiver. Compared to current indoor positioning systems using LED light, our system has the advantages of simple implementation, low cost and high accuracy. In our system, a single photo diode (PD) receives pilot signals from LED panels on the ceiling. Then the time differences of arrival (TDOA) of these pilot signals are used to estimate the position of the receiver. Our proposed sytem is simulated in the room measuring 5×5×3m3 with considering effect of noises such as shot noise, thermal noise, and noise caused by the reflected light from the walls. The simulation result shows that our system can achieve a high estimation accuracy of 3.6cm in average.

Performance Analysis of Visible Light Communication Using CMOS Sensors.

This paper elucidates the fundamentals of visible light communication systems that use the rolling shutter mechanism of CMOS sensors. All related information involving different subjects, such as photometry, camera operation, photography and image processing, are studied in tandem to explain the system. Then, the system performance is analyzed with respect to signal quality and data rate. To this end, a measure of signal quality, the signal to interference plus noise ratio (SINR), is formulated. Finally, a simulation is conducted to verify the analysis.

A Probability-Based Algorithm Using Image Sensors to Track the LED in a Vehicle Visible Light Communication System

This paper proposes a probability-based algorithm to track the LED in vehicle visible light communication systems using a camera. In this system, the transmitters are the vehicles’ front and rear LED lights. The receivers are high speed cameras that take a series of images of the LEDs. The data embedded in the light is extracted by first detecting the position of the LEDs in these images. Traditionally, LEDs are detected according to pixel intensity. However, when the vehicle is moving, motion blur occurs in the LED images, making it difficult to detect the LEDs. Particularly at high speeds, some frames are blurred at a high degree, which makes it impossible to detect the LED as well as extract the information embedded in these frames. The proposed algorithm relies not only on the pixel intensity, but also on the optical flow of the LEDs and on statistical information obtained from previous frames. Based on this information, the conditional probability that a pixel belongs to a LED is calculated. Then, the position of LED is determined based on this probability. To verify the suitability of the proposed algorithm, simulations are conducted by considering the incidents that can happen in a real-world situation, including a change in the position of the LEDs at each frame, as well as motion blur due to the vehicle speed.

Analysis of the effects of LED direction on the performance of visible light communication system

Visible light communication (VLC) is expected to be the next generation of indoor wireless communication. A VLC system uses many LED chips, and its performance is greatly affected by the direction of light-emitting diodes (LEDs). Normally, the LEDs are directed vertically downward to the floor. In this paper, we introduce an LED layout scheme in which the LEDs tilt toward the room corners. The effects of changing LED direction on system performance, including illuminance, received power, and SNR, are analyzed. The analysis is then verified by the simulations.

Performance analysis on MAC protocol based on beacon-enabled visible personal area networks

Visible light communication moves to the advanced research period for developing application services, but most of applications are limited only to PtP service model. However, PtMP communication environment for VLC is required to accommodate more various applications. In this paper, we analyze an effect of key parameters on network performance in the star topology based visible personal area network system. We implement a simulator with considering attributes of PHY and MAC layer which are defined by IEEE 802.15.7 standard documents, and analyze the VLC performance.

Optimization for link quality and power consumption of visible light communication system

Due to the complexity as well as trade-offs between objectives of the system, it is difficult to design a visible light communication (VLC) system with optimal link quality and power consumption. In this paper, the VLC system design problem is solved by using a multi-objective optimization method. Based on the results of the optimization process, we can determine the parameters to get a VLC system with optimal performance in respect of maximum link quality and minimum power consumption while illumination and other constraints are all satisfied.

Received power and SNR optimization for visible light communication system

The performance of a visible light communication system is greatly affected by LED layout setting. Received power and SNR can be increased or decreased by changing LED placement. However, there is trade-off between received power and SNR. This makes it impossible to design a VLC system that maximizes both received power and SNR simultaneously. In this paper, we find the Pareto-optimal LED layout settings, as well as the performances according to these setting using the SPEA2 multi-objective optimization algorithm. Based on the result of the multi-objective optimization process, one can design a VLC system with optimized performance.

Potentialities and challenges of VLC based outdoor positioning

While visible light communication (VLC) with inherent advantages is believed to be the next generation of wireless technology, positioning using visible light also has the potential of becoming a standard approach for positioning in the future. Although many indoor positioning systems based VLC have been proposed recently, there is very few paper related outdoor positioning using visible light. In this paper, firstly we point out difficulties when using visible light for outdoor positioning. Then we survey existing indoor positioning techniques using visible light and evaluate the potentialities and challenges of applying them to outdoor positioning.