• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.10A
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• pp.968-975
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• 2006

Research about the mode of MIMO that can get a coding benefit at the same time with a diversity benefit using a multiple antenna at the fading channel for a high-speed data transmission have been processed actively But the analysis about the interference of UWB system comes not to consist yet. So this paper analyzed the performance of the interference of UWB system to SFBC-OFDM and SFTC-OFDM system that applied a space block code which has a space diversity characteristic to OFDM system at MIMO channel. We shelved the performance that SFTC-OFDM system is robuster than SFBC-OFDM system under MB-OFDM UWB Interference.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.4 s.95
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• pp.351-358
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• 2005

In this paper, STBC(Space Time Block Code) is applied to the UWB system and frequency repeated diversity is used to get the 4-th order space time diversity gain. The performance of UWB STBC-OFDM system is analyzed by computer simulation. As a result of analysis, proposed UWB system can reduce the complexity that is introduced by increaing number of radiator and show the same performance of 4 antennas with that only using 2 radiator. This system at the $10^{-4}$ also shows the enhancement of $7.1\;\cal{dB}$ to the general UWB OFDM and $1.9\;\cal{dB}$ to UWB STBC-OFDM.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.11A
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• pp.1096-1105
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• 2007

In this paper, we propose a solution on interference problem of MB-OFDM UWB system using cognitive radio. We use interference temperature model of cognitive radio that has proposed by FCC for estimating interference signal. Calculating channel capacity of MB-OFDM UWB system with interference temperature, we suggest how to solve interference problem. We have used genetic algorithm in cognitive engine's calculation process. The proposed MB-OFDM UWB System with cognitive radio shows very efficient in solving interference problem.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.9
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• pp.1000-1009
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• 2008

The purpose of this paper is to analyze the performance of MB-OFDM UWB system when the interference signal that can be WIMAX signal or 4 G system signal is received by detection limit of -80 dBm/MHz proposed in Korea for DAA(Detect And Avoid) to permit UWB in $3.1{\sim}4.8$ GHz. MB-OFDM UWB system supports two transmission modes; one is TFI(Time frequency Interleaving) mode that transmits OFDM symbols using different carrier frequency from symbol to symbol according to Time Frequency(TF) codes, the other is FFI(Fixed Frequency Interleaving) mode that transmits OFDM symbols using a specific carrier frequency. In this paper, we considered the TX average power and the synchronization structure to reflect the effect of frequency hopping according to TFC. Interference analysis results show that the WiMAX system is fenced thoroughly from UWB interference in domestic DAA regulation, but the performance of MB-OFDM UWB system is degraded seriously by an interference signal with the DAA detection limit even in frequency Hopping mode that can get frequency diversity effect.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.23-26
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• 2003

본 논문은 UWB (Ultra Wide Band) 통신시스템에 대한 이해와 더불어 OFDM (Orthogonal Frequency Division Multiplexing/Modulation) 기반의 UWB 통신 시스템에 대해 가정된 매개변수를 이용하여 시스템을 설계하고, 설계된 시스템에 대한 모의실험을 통한 분석에 대해 기술한다. 본 논문에서는 IEEE 802.15.TG3a 표준화 위원회에서 UWB의 표준화를 위해 제시한 수정된 S-V (Saleh-Velenzuela) 모형을 기반으로 한 채널모형에 대한 설명과 기존에 연구된 OFDM 전송 기술에 대한 개요 및 장단점을 소개하고 이를 바탕으로 UWB 통신 시스템에 OFDM 전송 기술을 적용하기위한 적절한 매개변수를 도출한다. 그리고 도출된 매개변수를 바탕으로 OFDM 전송 기술의 모의실험을 수행하고, 모의 실험 결과를 통해 OFDM을 적용한 UWB 통신 시스템의 성능을 분석하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.3A
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• pp.232-239
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• 2006

In this paper, we analyze the preamble model for Wireless PAN(WPAN) in proposed Ultra WideBand(UWB) Multi-Band OFDM(MB-OFDM) system of IEEE 802.15.3a standard. Besides, we propose effective Carrier Frequency Offset and Symbol Timing Offset Estimation algorithm which offers enhanced performance, and analyze its performance using Detection Probability, False Alarm Probability, Missing Probability, Mean Acquisition Time and MSE(Mean Square Error) through simulation in AWGN and UWB channel environments.

• Proceedings of the Korea Contents Association Conference
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• 2004.05a
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• pp.423-428
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• 2004

In this paper, STBC (Space Time Block Code) is applied to the WB system and frequency repeated diversity is used to get the 4-th order space time diversity gain. The performance of が STDB-OFDM system is analyzed by computer simulation. As a result of simulation, proposed W system can reduce the complexity that is introduced by increasing number of transmit antenna and show the same performance of 4 antennas with only using 2. Proposed system shows the enhancement of 7.1 dB compared to the general UWB OFDM and 1.9 dB compared to UWB STBC-OFDM.

• Journal of Communications and Networks
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• v.8 no.2
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• pp.151-157
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• 2006

In a continuously expanding wireless world, the number of radio systems increases every day and efficient spectrum usage becomes a more significant requirement. Ultra-wideband (UWB) and cognitive radio are two exciting technologies that offer new approaches to the spectrum usage. The main objective of this paper is to shed the first light on the marriage of these two important approaches. The strength of orthogonal frequency division multiplexing (OFDM) based UWB in co-existing with licensed systems is investigated. The opportunity concept is defined, and the requirements of the opportunistic spectrum usage are explained. It is proposed to take the UWB-OFDM from the current underlay implementation, and evolve it to a combined underlay and opportunistic spectrum usage technology, leading to cognitive UWB-OFDM. This way, we aim at making UWB more competitive in the wireless market with extended range, higher capacity, better performance, and a wide variety of applications.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.293-296
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• 2004

This paper proposes an architecture of channel estimation for multi-band OFDM UWB systems presented to IEEE 802.15.3a by Multi-band OFDM alliance(MBOA). The multi-band OFDM (MB-OFDM) systems should have channel estimation for compensation of signal distortion by multi-band channel. The moving-averaging estimation algorithm and multi-band equalization architecture for MB-OFDM UWB systems proposed in this paper was verified by the simulation. Simulation results show that MB-OFDM system with the proposed architecture have the performance improved by about 3.4 dB compared to system with no channel estimation in 0.1$\pi$ phase-rotated channel.

• The KIPS Transactions:PartC
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• v.13C no.6 s.109
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• pp.677-684
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• 2006

This paper investigates the link margin of MB-OFDM UWB system quantitatively. Various simulations are performed considering the implementation loss by imperfect synchronization unit and the effect of multi-path fading channels. MB-OFDM UWB system uses ZP(Zero Padding) instead of CP(Cyclic Prefix) and supports two transmission modes; one is TFI(Time Frequency Interleaving) mode that transmits OFDM symbols using different carrier frequency from symbol to symbol according to Time Frequency(TF) codes, the other is FFI(Fixed Frequency Interleaving) mode that transmits OFDM symbols using a specific carrier frequency. The advantage of if and TFI is to be able to increase the transmitting power effectively compared to the existed OFDM systems that transmit the signal continuously at the same average transmitting power. From the analysis results of Ink margin, to guarantee the service range of 4m in 200Mbps mode, TFI mode must necessarily be implemented and the service range of 480Mbps mode is estimated about 1-2m in the line-of-sight multi-path channel (CMI).