Joon-Goo Park

Adaptive Filtering for Indoor Localization using ZIGBEE RSSI and LQI Measurement

The term “filter” is often used to describe a device in the form of a piece of physical hardware or computer software that is applied to a set of noisy data in order to extract information about a prescribed quantity of interest [25], [26]. Filter has been designed to take noisy data as input to reduce the effects of noise as much as possible. A Wireless Sensor Network (WSN) is a network that consists of numerous small devices that are in fact tiny computers. These so-called nodes are composed of a power supply, a processor, different kinds of memory and a radio transceiver for communication. WSNs are generally used to observe or sense the environment in a non-intrusive way. In order to perform this task, nodes are often extended with sensors, like infrared, ultrasonic or temperature sensors, hence the names sensor nodes and sensor networks. The domain of WSNs is still very young. During the last few years, new developments in the area of communication, computing and sensing have enabled and stimulated the miniaturization and optimization of computer hardware. These evolutions have led to the emergence of WSNs. Despite the increasing capabilities of hardware in general, sensor nodes are still very restricted devices. They have a limited amount of processing power, memory capacity and most importantly energy. This makes WSNs a challenging research topic. Despite current restrictions, several applications for WSNs have already been designed. WSNs are currently found in very different domains [3]. The large literature can be classified by relying on several criteria. One of these is the physical means used for localization, e.g., through the RF attenuation in the Electro-Magnetic (EM) waves [4], [11], [13] (Received Signal Strength Indicator RSSI based techniques) or the time required to cover the distance between transmitter and receiver (Ultra Wide Band); if using ultrasonic pulses, one could also use the time of arrival or time-difference of arrival of the waves [10]. This can even be extended to Audible-frequency sounds [9]. Another classification is based on the ranging feature, where distinguish between Range-free and Range-based localization techniques [11]. Moreover, it can be classified according to the Single-hop [11] and Multihop [14] localization scheme. Finally, it can differentiate between centralized [14] and distributed [9] localization systems. A common consensus among localization researchers is that indoor localization requires room-level accuracy. Indoor localization uses many different sensors such as infrared, RFID, Ultrasound, Ultra-Wide Band, Bluetooth, and WLAN. Different sensors provide different

Adaptive Parameter Estimation Method for Wireless Localization Using RSSI Measurements

In location-based service (LBS), it is important to determine the location of a mobile user more, exactly and efficiently. In case of a wireless network, such as IEEE 802.11, a method using a received signal strength indicator (RSSI) for each access point is advantageous because it does not require additional infrastructure and it is suitable for the simplification. However, this technique of localization is required to investigate the propagation environment to determine the location of mobile user in advance. We propose a method in which the parameters of the propagation environment are determined using only RSSI measurements obtained during localization.

On-Line Ranging for Mobile Objects Using ZIGBEE RSSI Measurement

Ubiquitous sensor networks have become one of the most popular areas for indoor location systems. This paper addresses the problem of tracking a moving object on-line, where location sensors provide position information about a moving object. All of these applications require the position of a device moving at human speeds to be tracked. This scheme presents a cheap and enhanced ranging technique using RSSI, which is achieved by considering the speed variance of the moving object. This proposed scheme applied the method of a sliding window which was used to track a mobile object on-line. The aim of the proposed system is to provide a low cost, simple technique based on RSSIs, provided by ZigBee modules. This paper considers the issues of user privacy, security, and accurate and robust indoor RF location. The analytical results of experimental data demonstrate the efficiency of the proposed RF-based indoor positioning.

A RFID Reader Configuration with an Enhanced Recognition Property for Indoor Positioning

Recently, LBS(Location Based Service) is a very important issue in wireless communication network. Stable location determination can be more important issue for seamless services. GPS covers outdoor location perception but has a serious problem for indoor applications like in-building,tunnel, etc. For indoor positioning, many new positioning systems are developed and considered. RFID positioning system is one of strong candidate methods in indoor positioning since it provides simple indoor location detection and diverse compatibility with other existing positioning systems. In this paper, we propose an optimal reader configuration for performance enhancement without additional use of readers and signal strength amplification in RFID indoor positioning. And we prove RFID reader configuration is very important through many experimental results. A good configuration can give an enhanced recognition property. According to several kinds of selected reader configuration, we compare with performances and explain necessity of optimum reader configuration method.

Design Optimization of Waveguide Filters Using Continuum Design Sensitivity Analysis

This paper presents a new methodology for design optimization of dielectric waveguide filters based on the continuum design sensitivity analysis in conjunction with standard electromagnetic analysis codes. To achieve this, first, an analytical sensitivity formula in the frequency domain is systematically derived by exploiting the augmented Lagrangian method, material derivative concept and adjoint variable method. Then unified program architecture integrating several engineering software packages into a design tool is proposed for optimum design of high-frequency devices. A 3-D dielectric resonator used in waveguide filters has been tested to prove the validity of the proposed method.

RFID System for Medical Charts Management and Its Enhancement of Recognition Property

Many hospitals adopt hand-in-out system for patient management and patient¿s disease history report. It causes medical report sheets in-out to complicate in a hospital¿s related department and it is a heavy burden to worker. Sometimes, it can give rise to exchange medical report sheets between their patients by mistakes. That can result in a serious medical accident, especially for complete cure or emergency cure. Therefore, we propose to use RFID system for medical chart management. RFID system can recognize a lot of tags during short time simultaneously. It has a wide range for possible frequencies and it is strong material about security. Because of this reason, lots of business systems adopt RFID. There are two issues which should be considered when adopting RFID medical chart management system. First one is how to identify more tags simultaneously and correctly. For this we will propose optimized reader allocation methods. Second one is to reduce read time. For this we suggest new double tag elimination method.

A Novel Cubic-Phase Linear Chirp for DS-UWB Ranging

Since the UWB (ultra-wideband) communications system occupies very large bandwidth, it performs high- precision ranging. In this paper a novel chirp signal is proposed for DS (direct-sequence)-UWB ranging. The cubic-phase linear (CPL) chirp exhibits enhanced correlation function in the aspect of mainlobe-1st sidelobe ratio. And this enables the better pilot signal detection than the existing quadratic-phase chirp. Simulation results in AWGN channel confirmed the improved ranging accuracy.

Sidelobe Suppression Methods of Cubic-Phase Linear Chirp in Two-Ray Multipath Model for UWB Ranging

The UWB communication system occupies a very large bandwidth, 7.5 GHz. This enables high precision ranging that provides correct position information. In this paper, we will present a method to reduce side-lobes in receiver. Reducing side-lobes can enhance the accuracy of ranging system. Ranging system with high ratio of main-lobe to 1st side-lobe produces lower calculation error in ranging. Proposed cubic-phase chirp signal method can reduce the power of 1st side-lobe, that is, realize higher accurate ranging.

Enhancing physical-layer security in MISO wiretap channel with pilot-assisted channel estimation: Beamforming design for pilot jamming

In this paper, we tackle the physical-layer security issue in MISO wiretap channel considering the pilot-assisted channel estimation at the receiver side. Unlike the conventional schemes, we introduce the cooperative jamming scheme that transmits artificial noise (AN) only on downlink pilot transmission phase. In order to disrupt the channel estimation at the eavesdropper (Eve) effectively, an optimal beamforming at the cooperative jammer (CJ) was obtained by means of difference-of-convex (DC) algorithm and rank relaxation. In addition, with focus on the energy budget limitation issue at the CJ, energy efficiency at the CJ is verified based on the circuit power consumption model. Numerical results provide a performance comparison with a conventional scheme, which transmits AN only in data transmission phase.

A New Unified Scheme Computing the Quadrature Weights, Integration and Differentiation Matrix for the Spectral Method

A unified numerical method for computing the quadrature weights, integration matrix, and differentiation matrix is newly developed in this study. For this purpose, a spline-like interpolation using piecewise continuous polynomials is converted into a global spline interpolation formula, with which the quadrature formulas can be derived from integration and differentiation of the transformed function in an exact manner. To prove the usefulness of the suggested approach, both the Lagrange and tension spline interpolations are represented in exactly the same form as global spline interpolation. The applicability of the proposed method on arbitrary nodes is illustrated using two different sets of nodes. A series of validations using three test functions is conducted to show the flexibility in selecting computational nodes with the present method.