Chul-Gyu Kang

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.

Designing of Dynamic Sensor Networks based on Meter-range Swarming Flight Type Air Nodes

Dynamic sensor network(DSN) technology which is based on swarming flight type air node offers analyzed and acquired information on target data gathered by air nodes in rotation flight or 3 dimension array flight. Efficient operation of dynamic sensor network based on air node is possible when problems of processing time, data transmission reliability, power consumption and intermittent connectivity are solved. Delay tolerant network (DTN) can be a desirable alternative to solve those problems. DTN using storeand-forward message switching technology is a solution to intermittent network connectivity, long and variable delay time, asymmetric data rates, and high error rates. However, all processes are performed at the bundle layer, so high power consumption, long processing time, and repeated reliability technique occur. DSN based on swarming flight type air node need to adopt store-andforward message switching technique of DTN, the cancelation scheme of repeated reliability technique, fast processing time with simplified layer composition.

Location Estimation of Satellite Radio Interferer Using Cross Ambiguity Function Map for Protection of Satellite Resources

In this paper, a scheme using Cross Ambiguity Function (CAF) map is proposed to estimate the location of an unknown interferer which emits harmful radio signal in the satellite communication network. In conventional CAF based TDOA, FDOA location, TDOA and FDOA are determined by location the peak in the CAF plane and then the peak’s information is fed into a least squares like location tool to determine the emitter’s location. However, this proposed scheme omits the step in which the location is determined with the post processed CAF peak information and instead maps the CAF surface directly to the earth surface. In simulation results, the distance error of about 800 m is occurred at Eb/N0 = 4–10 dB and the distance error of about 1.3 km is occurred at −20 dB of Eb/N0.

Joint BLAST-STTC for MIMO-OFDM System

This study focuses on improving MIMOOFDM systems by combining a wireless communication architecture known as vertical BLAST(bell laboratories layered space-time) or V-BLAST and STTC(space time trellis coding). In this paper, the combination is done by introducing STTC in each V-BLAST layer. Moreover, this architecture uses multiple antennas that are grouped into small number of antennas which makes it less complex to decode by decoding every group. Whereas, in traditional VBLAST, all the antennas form one group and they are decoded together at the receiver, therefore, this increases the complexity as the number of antennas is getting high. We compare the bit error rate performance of this system with MIMO-OFDM that uses convolutional coding instead of STTC. Under the same spectral efficiency, the simulation results prove that joining V-BLAST with STTC improves MIMO-OFDM systems performance.

Reliability and capacity enhancement algorithms for wireless personal area network using an intelligent coordination scheme

In this paper, we propose reliability and capacity enhancement algorithms for high data rate wireless personal area network (HDR-WPAN) system using an intelligent coordination scheme. Conventional system (i.e., IEEE802.15.3, HDR-WPAN) supports maximum 55Mbps transmission rate at 15MHz bandwidth. Proposed intelligent coordination scheme is a modification of HDR-WPAN specification to enhance the reliability and transmission rate using an adaptive modulation and bandwidth expansion method. The proposed system is analyzed through a computer simulation in respect of reliability, transmission rate, and power spectrum density (PSD). From the results, the proposed system has maximum 110Mbps data rate and reliability of 10−−5 at E0/N0 = 21dB in indoor radio channel when we employ a TCM-128QAM at 25MHz bandwidth.