Chang-Heon Oh

NLOS Signal Effect Cancellation Algorithm for TDOA Localization in Wireless Sensor Network

In this paper, the iteration localization algorithm that NLOS signal is iteratively removed to get the exact location in the wireless sensor network is proposed. To evaluate the performance of the proposed algorithm, TDOA location estimation method is used, and readers are located on every 150m intervals with rectangular shape in 300m x 300m searching field. In that searching field, the error distance is analyzed according to increasing the number of iteration, sub-blink and the estimated sensor node locations which are located in the iteration range. From simulation results, the error distance is diminished according to increasing the number of the sub-blink and iteration with the proposed location estimation algorithm in NLOS environment. Therefore, to get more accurate location information in wireless sensor network in NLOS environments, the proposed location estimation algorithm removing NLOS signal effects through iteration scheme is suitable.

Interference Analysis of Geostationary Satellite Networks in the Presence of Moving Non-Geostationary Satellites

In this paper, interference effect given from nongeostationary orbit link into geostationary orbit link is analyzed by BER performance. To analyze the interference effect with the angle between satellites, the angular separation is changed from 1° to 8°, and the number of the satellite is also changed from 1 to 4 for analyzing it. From the results, the interference effect into the geostationary orbit service from non-geostationary orbit link is more increased according to the angular separation that is decreased. Especially, the small angle gives more interference effects to the geostationary orbit link. Furthermore, more number of interfering satellites gives more interference effect to the geostationary orbit link. However, the angle between the interference orbit and geostationary orbit gives more effect to the system performance then the number of the interference orbit.

Location Estimation Using Space-Time Signal Processing in RFID Wireless Sensor Networks

We consider real-time locating systems (RTLS) consisting of radio frequency identification (RFID) tags and multiantenna readers to propose a novel location estimation algorithm based on the concept of space-time signature matching for multipath environments. In contrast to previous fingerprint-based approaches that rely on received signal strength (RSS) information only, the proposed algorithm uses angle, delay, and RSS information from the received signal to form a signature, which in turn is utilized for location estimation. We evaluate the performance of the proposed algorithm in terms of the average error probability. Simulations and analytic results confirm the effectiveness of the proposed algorithm for location estimation even in non-line-of-sight (NLOS) environments.

Location Estimation Enhancement Using Space-time Signal Processing in Wireless Sensor Networks: Non-coherent Detection

In this paper, we proposed a novel location estimation algorithm based on the concept of space-time signature matching in a moving target environment. In contrast to previous fingerprint-based approaches that rely on received signal strength (RSS) information only, the proposed algorithm uses angle, delay, and RSS information from the received signal to form a signature, which in turn is utilized for location estimation. We evaluated the performance of the proposed algorithm in terms of the average probability of error and the average error distance as a function of target movement. Simulation results confirmed the effectiveness of the proposed algorithm for location estimation even in moving target environment.

Analysis of the Effect of Coherence Bandwidth on Leakage Suppression Methods for OFDM Channel Estimation

In this paper, we analyze the effect of the coherence bandwidth of wireless channels on leakage suppression methods for discrete Fourier transform (DFT)-based channel estimation in orthogonal frequency division multiplexing (OFDM) systems. Virtual carriers in an OFDM symbol cause orthogonality loss in DFT-based channel estimation, which is referred to as the leakage problem. In order to solve the leakage problem, optimal and suboptimal methods have already been proposed. However, according to our analysis, the performance of these methods highly depends on the coherence bandwidth of wireless channels. If some of the estimated channel frequency responses are placed outside the coherence bandwidth, a channel estimation error occurs and the entire performance worsens in spite of a high signal-to-noise ratio.

SVM-Based Dynamic Reconfiguration CPS for Manufacturing System in Industry 4.0

CPS is potential application in various fields, such as medical, healthcare, energy, transportation, and defense, as well as Industry 4.0 in Germany. Although studies on the equipment aging and prediction of problem have been done by combining CPS with Industry 4.0, such studies were based on small numbers and majority of the papers focused primarily on CPS methodology. Therefore, it is necessary to study active self-protection to enable self-management functions, such as self-healing by applying CPS in shop-floor. In this paper, we have proposed modeling of shop-floor and a dynamic reconfigurable CPS scheme that can predict the occurrence of anomalies and self-protection in the model. For this purpose, SVM was used as a machine learning technology and it was possible to restrain overloading in manufacturing process. In addition, we design CPS framework based on machine learning for Industry 4.0, simulate it, and perform. Simulation results show the simulation model autonomously detects the abnormal situation and it is dynamically reconfigured through self-healing.

Network System Based on M2M for Efficient Visual Information Service

Current visual information is, as an information delivery mediator of information society, playing a very important role and its applied fields are growing exponentially. However, existing network system collecting and providing visual information requires human to act in awareness and transmission of data and causes data delay. In this paper, proposes network system replacing part processed by human awareness through combining M2M technology on the network system that collects visual information in order to solve the problem. The proposed system compares information from mobile devices captured on visual device and data for visual information requested by each server and sets the route visual information is transferred. As a result of test in environment to fit M2M major component with development of M2M devices using AVR, we could learn that only visual information matching content saved on M2M application server database built using transferred data from several servers among visual data collected continuously is transmitted to the server requesting information.

Performance analysis of location estimation algorithm using an intelligent coordination scheme in RTLS

In this paper, we proposed a high precision location estimation algorithm using an intelligent coordination scheme in 2.45GHz RTLS and analyzed an average estimation error distance at 2D coordinates searching-area (300m×300m and 250m×250m). An average error distance was reduced as the number of available reader and received sub-blink increased. Proposed location estimation algorithm satisfied the RTLS specification requirements, 3m radius accuracy when the number of available reader is greater than 3 and the received sub-blink number exceeds 2 times in 250m×250m. Also, an average error distance was saturated within 0.5m~2.5m in case of 250m×250m when the number of available reader is greater than 4 regardless of the number of sub-blink. Also we confirmed that the 3m radius accuracy is 78 percent, and the 2.348m radius accuracy is 72 percent in 300m×300m searching-area when the number of available reader and received sub-blink was 8 and 4 times, respectively. In that case, we confirmed that 3m radius accuracy is 99 percent, and the 2.348m radius accuracy is 97 percent in 250m×250m searching-area.

Packet Error Probability of Multi-carrier CDMA System in Fast/Slow Correlated Fading Plus Interference Channel

The probability of packet error for Multi-Carrier CDMA system with maximum ratio combining diversity is evaluated and compared in the slow and fast correlated Nakagami fading plus multiple access interference channel. From the results, the probability of packet error in fast fading is higher than that in slow fading, and the difference of packet error probability between the fast fading and slow fading diminishes with Nakagami fading parameter approaching infinity. When the error correction coding technique is used, it is observed that coding technique for Multi-Carrier CDMA system is more effective in the fast fading case than that in the slow fading case.

A Study on the Educational Effectiveness of the Industry Professional Practice (IPP) Program

The objective of this chapter is to examine the effects of Industry Professional Practice (IPP), a long-term on-site training program. To achieve this, two groups of students answered multiple questions that pertained to four categories: “major”, “career”, “personal relationships”, and “problem-solving”. The first group consisted of 36 students currently enrolled at a university in Cheonan, Korea, and who participated in the IPP program (and have since returned to university). The other group consisted of 60 regular students at the same university who had never participated in the IPP program.