• 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 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.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.11 s.353
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• pp.90-97
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• 2006

In this paper, we present a cost-effective architecture of high-speed soft-decision Viterbi decoder for Multi-band OFDM(MB-OFDM) systems. In the design of modem for MB-OFDM systems, a parallel processing architecture is general]y used for the reliable hardware implementation, because the systems should support a very high-speed data rate of at most 480Mbps. A Viterbi decoder also should be designed by using a parallel processing structure and support a very high-speed data rate. Therefore, we present a optimized hardware architecture for 4-way parallel processing Viterbi decoder in this paper. In order to optimize the hardware of Viterbi decoder, we compare and analyze various ACS architectures and find the optimal one among them with respect to hardware complexity and operating frequency The Viterbi decoder with a optimal hardware architecture is designed and verified by using Verilog HDL, and synthesized into gate-level circuits with TSMC 0.13um library. In the synthesis results, we find that the Viterbi decoder contains about 280K gates and works properly at the speed required in MB-OFDM systems.

• IEMEK Journal of Embedded Systems and Applications
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• v.1 no.1
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• pp.20-23
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• 2006

본 논문은 MB-OFDM UWB(Multi Band-Orthogonal Frequency Division Multiplexing Ultra Wide Band) 시스템을 위한 변형된 가변 파라미터를 이용한 큐빅 인터폴레이터를 제안한다. MB-OFDM UWB 시스템은 고속의 동작속도가 필요하기 때문에, 기존 가변 파라미터를 이용한 큐빅 인터폴레이터에 병렬 처리 기술과 파이프라인 기법을 동시에 적용한다. 실험 결과, Stratix II 2S60F101020C3 디바이스를 타켓으로 최대지연경로 속도와 최대지연경로 주기가 각각 최대 88.79MHz와 11.262ns가 되었고, 동작속도는 최대 대략 200% 이상 향상되었음을 알 수 있다.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2006.07a
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• pp.415-415
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• 2006

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.10C
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• pp.965-975
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• 2005

In this paper, we propose and evaluate joint carrier and sampling frequency offset estimation schemes based on the channel estimation sequences in PLCP (Physical Layer Convergence Procedure) preamble for the proper and effcient synchronization of the MB-OFDM WB (Multi-Band Orthogonal Frequency Division Multiplexing Ultra Wide Band) systems which have recently drawn explosive attention for future W-PAN (Wireless Personal Area Network) applications. In the joint estimation schemes, we first estimate the sampling frequency offset, and then estimate the carrier frequency offset using the estimated sampling frequency offset. Moreover, to improve the reliability of the estimated offset values, each process uses a combination scheme based on weighting factors. Simulation results using IEEE 802.15 Task Group 3a UWB channel models reveal that the estimation scheme using the simple weighting factors based on easily-measurable received signal power of each sub-channel shows favorably comparable performance to the ideal scheme using the weighting factors based on the perfectly-estimated frequency response of the channel.

• Journal of Advanced Navigation Technology
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• v.8 no.1
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• pp.73-80
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• 2004

In the case of Non-Line-of-Sight (NLOS), common telecommunication systems typically have Rayleigh distributed amplitude characteristics. However measurement result of Ultra Wideband (UWB) Multi-Band Orthogonal Frequency Division Multiplexing (MB-OFDM) system which is proposed as one of candidate standard in IEEE 802. 15. 3a for Wireless Personal Area Network (WPAN) shows that it has independent log normal fading in each cluster as well as in each ray within the cluster. Based on this clustering phenomenon observed, MB-OFDM channel model derived from Saleh-Valenzuela model with a couple of slight modifications. In this paper, channel remodeling for RF frequency hopping in MB-OFDM system is achieved, and performances of MB-OFDM system for each channel mode and data rate are verified using modified channel model.

• 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).

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.693-696
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• 2008

The systems for mobile communication services of fourth generation use OFDM (Orthogonal Frequency Division Multiplexing) scheme that ran transmit large amounts of data to support the multimedia services, and consist of several types of cell, such as Macro Cell, Pico Cell, Femto Cell to improve the qualify of service. According to subdivision of communication region, superposition of cells in co-channel different from conventional single cell is used, but it cause inter band interference between systems. In particular, an OFDM signal consists of a number of independently modulated subcarriers, and superposition of these subcarriers causes a problem that ran give a large PAPR. Increased PAPR induces signal distortion passing through components such as power amplifier so that inter band interference is caused by out-of-band spectrum radiation. In order to minimize the inter band interference, this paper applies PAPR reduction scheme and analyzes the out-of-band spectrum radiation when the signal passes through nonlinear components such an power amplifier.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.11
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• pp.1149-1155
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• 2003

OFDM/SFH(orthogonal frequency division multiplexing/slow frequency hopping) system is the combination of OFDM communication system with frequency hopping(FH) method and OFDM/DS(orthogonal frequency division multiplexing/direct sequence) system combines the OFDM communication system with direct sequence(DS) method in terms of PN(pseudo noise) sequence. These two systems are also can be used for anti-jamming. In this study we analyze performances of OFDM/SFH system and OFDM/DS system with the equal information rate in partial band jamming and tone jamming channel. We find BER(bit error rate) in the variation of JFR(jamming fractional ratio) and JSR(jamming to signal power ratio) of the partial band jamming. Also, BER is found in the several JSR of the single tone or multi tone jamming. OFDM/DS system shows better performance than OFDM/SFH system in partial band jamming environment. OFDM/DS system has about 2.5 ㏈ SNR(signal to noise power ratio) gains than OFDM/SFH system when JFR=4/16 and JSR=0 ㏈ to meet BER=10$\^$-3/. However, OFDM/SFH system has about 3 ㏈ SNR gains than OFDM/DS system at single tone jamming of JSR=5 ㏈. In multi tone jamming, performance of OFDM/SFH system is considerably degraded than OFDM/DS system.