• ETRI Journal
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• 제28권1호
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• pp.95-98
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• 2006

In this letter, a novel M-ary code-selected direct sequence (DS) ultra-wideband (UWB) communication system is presented. Our purpose is to achieve a high data rate by an M-ary code-selected direct sequence bipolar pulse amplitude modulation (MCSDS-BPAM) scheme. In this system, a particular DS code sequence is selected by the $log_2M$/2 bits from the DS gold code set. This scheme can accomplish both a high data rate without increasing the system bandwidth or changing the pulse shape and improve the BER with an increase of modulation level M even at a lower signal-to-noise ratio (SNR). The receiver signal processing algorithm is given for an MCSDS-BPAM UWB system over an ideal AWGN channel and correlation receivers.

• Journal of Communications and Networks
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• 제10권1호
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• pp.63-70
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• 2008

Narrow-band interference (NBI) from the coexisting narrow-band services affects the performance of ultra wideband (UWB) systems considerably due to the high power of these narrow-band signals with respect to the UWB signals. Specifically, IEEE 802.11a systems which operate around 5 GHz and overlap the band of UWB signals may interfere with UWB systems significantly. In this paper, we suggest a novel NBI suppression technique based on singular value decomposition (SVD) algorithm in time hopping UWB (TH-UWB) systems. SVD is used to approximate the interference which then is subtracted from the received signals. The algorithm precision and closed-form bit error rate (BER) expression are derived in the wireless multipath channel. Comparing with the conventional suppression methods such as a notch filter and a RAKE receiver, the proposed method is simple and robust and especially suitable for UWB systems.

• Journal of Astronomy and Space Sciences
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• 제17권2호
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• pp.221-232
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• 2000

밀리미터파 우주잔파 수신기의 국부 발진기로 사용될 수 있는 도파관형 건 발진기를 제작하였다. 제작한 건 발진기는 60 GHz에서 70 GHz까지 발진하는 광대역 특성을 보였다. 건 발진기는 공진 디스크와 포스트의 직경 변화와 다이오드 특성에 따라 발진 주파수의 특성이 달라진다. 본 논문에 우리는 광대역 발진 특성을 가지는 건 발진기의 설계 방법과 측정결과를 보였으며, 제작한 발진기는 대덕천파천문대의 100/150 GHz대 이중채널 수신기로 활용되고 있다.

• ETRI Journal
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• 제32권3호
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• pp.460-463
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• 2010

This letter proposes an energy-detection-based non-data-aided weighted non-coherent receiver (NDA-WNCR) scheme for impulse radio ultra-wideband (IR-UWB) pulse-position modulated signals. Compared to the conventional WNCR, the optimal weights of the proposed NDA-WNCR are tremendously simplified as the maximum eigenvector of the IR-UWB signal energy sample autocorrelation matrix. The NDA-WNCR serves to blindly obtain the optimal weights and entirely circumvent the transmission of training symbols or channel estimation in practice. Analysis and simulation results verify that the bit error rate (BER) performance of the NDA-WNCR closely approaches the ideal BER of the conventional WNCRs.

• Journal of information and communication convergence engineering
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• 제10권3호
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• pp.215-219
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• 2012

This paper applies transmit antenna selection algorithms to spatial-temporal combining-based spatial multiplexing (SM) ultra-wideband (UWB) systems. The employed criterion is based on the largest minimum output signal-to-noise ratio of the multiplexed streams. It is shown via simulations that the bit error rate (BER) performance of the SM UWB systems based on the two-dimensional Rake receiver is significantly improved by antenna diversity through transmit antenna selection on a log-normal multipath fading channel. When the transmit antenna diversity through antenna selection is exploited in the SM UWB systems, the BER performance of the spatial-temporal combining-based zero-forcing (ZF) receiver is also compared with that of the ZF detector followed by the Rake receiver.

• 한국항해항만학회지
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• 제31권2호
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• pp.159-163
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• 2007

In this paper, we mainly analyze the performance of two ultra wideband communication systems, the classical Time Hopping Binary Pulse Position Modulation (TH-BPPM) UWB system and the Time Hopping Bipolar Pulse Amplitude Modulation (TH-BPAM) UWB system. The performance of TH-BPPM and TH-BPAM is analyzed in detail under an ideal AWGN channel and a correlation receiver. We use the power spectral density function to get the expression of BER of these two UWB systems. It yields simple and exact formulas relating the performance to the system parameters. The analysis shows that TH-BPPM suffers performance degradation with respect to TH-BPAM. Furthermore, we give the computer simulation of both data and image transmission and our simulation results also prove our theoretical analysis.

• Journal of Positioning, Navigation, and Timing
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• 제11권1호
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• pp.45-49
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• 2022

In this paper, we propose a method for estimating the error of the Ultra-Wideband (UWB) distance measurement using the channel impulse response (CIR) of the UWB signal based on machine learning. Due to the recent demand for indoor location-based services, wireless signal-based localization technologies are being studied, such as UWB, Wi-Fi, and Bluetooth. The constructive obstacles constituting the indoor environment make the distance measurement of UWB inaccurate, which lowers the indoor localization accuracy. Therefore, we apply machine learning to learn the characteristics of UWB signals and estimate the error of UWB distance measurements. In addition, the performance of the proposed algorithm is analyzed through experiments in an indoor environment composed of various walls.

• 한국인터넷방송통신학회논문지
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• 제10권3호
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• pp.1-10
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• 2010

IR (impulse radio)를 사용하는 IR-UWB 방식은 짧은 펄스를 전송하기 때문에 송수신기를 간단히 구현할 수 있고, 저 전력으로 구현 가능하며, 다중 경로 지연과 같은 외부 환경에 강한 특성을 가진다. 더불어, 짧은 펄스를 사용하므로 데이터 수신시 채널의 특징을 파악하기 위해 정확한 채널 추정 방법이 요구 된다. 채널 추정한 후 추정된 채널 이득과 지연 값은 레이크 수신기의 경로 선택에 이용되고, 데이터 수신시 파라메타를 정확히 찾는 정도에 따라서 성능이 좌우된다. 본 문서에서는 수신된 프리엠블 등의 신호를 이용하여 채널의 특성을 파악하여 관련 파라메터를 추출하는 채널 추정 알고리즘 및 다양한 관련 기술에 대하여 소개한다.

• 전기전자학회논문지
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• 제23권1호
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• pp.91-98
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• 2019

3GPP LTE의 비면허대역 솔루션인 Licensed Assisted Access (LAA) 기술은 Listen-Before-Talk (LBT)을 수행한다. 이는 Wi-Fi와의 공존을 위해 Wi-Fi의 백오프 기법과 매우 유사하게 설계되었다. 하지만, Wi-Fi의 백오프 기법은 기존 장치와의 호환 및 공존을 위해 오래된 설계에 기반하고 있어, LAA의 LBT 또한 스펙트럼 이용에 있어 비효율성을 보인다. 만약 근처에 Wi-Fi 시스템이 없는 환경이라면 LAA는 보다 효율적인 LBT를 수행할 수 있다. 이 논문은 협대역 전송을 위한 Narrowband Clear Channel Assessment (NCCA)를 제안한다. NCCA에서 LAA 기지국은 광대역 또는 각 협대역 밴드에서 LBT를 수행한다. 이를 통해, 복수의 LAA 노드가 서로 다른 협대역에서 동시에 전송할 수 있게 한다. NCCA 구현을 위해 네 가지의 설계안을 제시하고, 성능 예측을 위한 수학 모델을 제시한다. 기존 광대역 시스템과 공존하는 시나리오에서 시뮬레이션을 통해 NCCA의 공존 성능과 제시한 성능 모델의 정확성을 보인다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 제14회 신호처리 합동 학술대회 논문집
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• pp.959-962
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• 2001

Turbo codes of long block sizes have been known to show very good performance in an AWGN channel and the turbo code has been strongly recommended as error correction code for IMT-2000 in 3GPP(3rd Generation Partnership Project). Recently, turbo codes of short block sizes suitable for real time communication systems have attracted a lot of attention. Thus, in this paper we consider the turbo code of 1/3 code rate and short frame size of 192 bits in ITU-R channel model. We analyzed the performance of W-CDMA systems of 10MHz bandwidths employing RAKE receiver with not only MRC diversity but also turbo code.