Ki-Doo Kim

Localization of Wireless Sensor Network using artificial neural network

In Wireless Sensor Networks (WSN), location estimation is important for routing efficiency and location-aware services. Traditional received signal strength based localizations using propagation-loss model are often erroneous for the low-cost WSN devices. The reason is that the wireless channel is vulnerable to so many factors that deriving the appropriate propagation-loss model for the low cost WSN devices is not possible. Hence, we propose a flexible model based on neural network and grid sensor training phase for accurate localization of sensors. Simulation results show that the location accuracy can be increased by increasing the grid sensor density and the number of access points.

Performance improvement of indoor positioning using light-emitting diodes and an image sensor for light-emitting diode communication

Abstract. Light-emitting diodes (LEDs) are expected to replace existing lighting technologies in the near future because of the potential dual function of LED light (i.e., wireless communication and lighting) in the context of visible light communication (VLC). We propose a highly precise indoor positioning algorithm using lighting LEDs, an image sensor, and VLC. In the proposed algorithm, three LEDs transmit their three-dimensional coordinate information, which is received and demodulated by a single image sensor at an unknown position. The unknown position is then calculated from the geometrical relations of the LED images created on the image sensor plane. We describe the algorithm in detail. A simulation of the proposed algorithm is presented in this paper. We also compare the performance of this algorithm with that of our previously proposed algorithm. The comparison indicates significant improvement in positioning accuracy because of the simple algorithmic structure and low computational complexity. This technique does not require any angular measurement, which is needed in the contemporary positioning algorithms using LEDs and image sensor. The simulation results show that the proposed system can estimate the unknown position to an accuracy of 0.001 m inside the approximate positioning area when the pixel value is >3000.

Color-Space-Based Visual-MIMO for V2X Communication

In this paper, we analyze the applicability of color-space-based, color-independent visual-MIMO for V2X. We aim to achieve a visual-MIMO scheme that can maintain the original color and brightness while performing seamless communication. We consider two scenarios of GCM based visual-MIMO for V2X. One is a multipath transmission using visual-MIMO networking and the other is multi-node V2X communication. In the scenario of multipath transmission, we analyze the channel capacity numerically and we illustrate the significance of networking information such as distance, reference color (symbol), and multiplexing-diversity mode transitions. In addition, in the V2X scenario of multiple access, we may achieve the simultaneous multiple access communication without node interferences by dividing the communication area using image processing. Finally, through numerical simulation, we show the superior SER performance of the visual-MIMO scheme compared with LED-PD communication and show the numerical result of the GCM based visual-MIMO channel capacity versus distance.

Enhanced-xVSB system development for improving ATSC terrestrial DTV transmission standard

This paper describes advanced dual stream system for improving mobile/pedestrian reception performance to the ATSC DTV 8-VSB transmission standard. E-xVSB system can transmit a mixture of normal (8-VSB) stream and enhanced (robust) stream. The robust stream has a higher threshold of visibility (TOV) compared to the standard stream, and legacy receivers ignore the robust packets. Thus, Enhanced-xVSB system is fully backward compatible with a current ATSC standard. For more robust transmission support, E-xVSB system adopts a reduced constellation method as well as enhanced trellis-coded modulation scheme. E-xVSB system supports a variety of enhanced modulation schemes: Pseudo-2VSB, Enhanced-4VSB, modified Enhanced-8VSB and Hybrid-VSB. Proposed system has been tested in the Lab, and the testing results are shown in this paper.

LEA Detection and Tracking Method for Color-Independent Visual-MIMO

Communication performance in the color-independent visual-multiple input multiple output (visual-MIMO) technique is deteriorated by light emitting array (LEA) detection and tracking errors in the received image because the image sensor included in the camera must be used as the receiver in the visual-MIMO system. In this paper, in order to improve detection reliability, we first set up the color-space-based region of interest (ROI) in which an LEA is likely to be placed, and then use the Harris corner detection method. Next, we use Kalman filtering for robust tracking by predicting the most probable location of the LEA when the relative position between the camera and the LEA varies. In the last step of our proposed method, the perspective projection is used to correct the distorted image, which can improve the symbol decision accuracy. Finally, through numerical simulation, we show the possibility of robust detection and tracking of the LEA, which results in a symbol error rate (SER) performance improvement.

Efficient clustering algorithm for delay sensitive PON-based wireless sensor network

To maintain the latency and energy secured data transmission, super frame structure is important with MAC protocol. We propose a new clustering algorithm and PON-based structure to balance the network traffic and limit the network size. We also analyze effect of super frame size on network delay and energy consumption.

Performance Analysis of Color-Independent Visible Light Communication Using a Color-Space-Based Constellation Diagram and Modulation Scheme

In this paper, various aspects of a color-space-based visible-light communication (VLC) system design are explored, including feasible light color spaces, potential constellation diagrams, data-to-light intensity mapping, and light intensity-to-data demapping. After describing the proposed VLC system and parameters essential for a color-space-based VLC system design, numerous methods of constellation design for generating a target color in a light color space are presented. The proposed method also incorporates a technique to calculate light intensity from the constellation point. The performance of a proposed system is analyzed with an additive white Gaussian noise channel along with various color scenarios. We also investigate two cases to obtain the target color information at the receiver. Simulation results are presented in order to evaluate the performance of the proposed VLC system.

Color-independent OFDM-based visible light communication

In this paper, we propose an OFDM-based VLC system which can be color-independent by using the color space-based modulation. Along with all promising advantages of OFDM, the proposed system will be applicable for all colors in the visible range.

Applicability of color-independent visual-MIMO for V2X communication

In this paper, we analyze the applicability of color-space-based color-independent visual-MIMO for V2X. We aim to achieve a visual-MIMO scheme that can maintain the original color and brightness while performing seamless communication. The visual-MIMO system will switch between multiplexing and diversity modes depending on distance. Considering the scenario of a multipath transmission based on our visual-MIMO model, we analyze the channel capacity numerically and we illustrate the significance of networking information such as distance, reference color (symbol), and multiplexing-diversity mode transitions.

Implementation of indoor positioning using LED and dual PC cameras

We show the successful implementation of indoor positioning by using four single LEDs and dual PC cameras. Each LED having its position information is identified by the different color. The required unknown position is then calculated using the position information of the LEDs and the geometric relationship of the images on the two image sensors. And a vector estimation algorithm is also used to solve a set of four quadratic equations. To remove a fluctuating due to the quantization error of the pixel, we compute the center of an image in terms of decimal point pixel and it brings the accuracy improvement.