• The Journal of the Acoustical Society of Korea
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• v.16 no.5
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• pp.5-11
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• 1997

In this paper, we investigate the performance of the direct sequence/spread spectrum multiple access (DS/SSMA) system using the Trellis coded modulation (TCM) technique in both multipath fading and multi-user channel environments. For this, an expression that represents the pairwise bit error probability of the system is derived. Unlike the existing results that were performed in a more restrictive condition considering only the multi-user effect, the effects of the multipath fading as well as the multi-user environments are compositely taken into account. In order to check the validity of our analysis, although not direct, computer simulations are carried out, and they show that our expression matches exactly with the previous work for which the TCM and the multipath effects were disregarded. Moreover, it is observed that the performance of the Trellis coded DS/SSMA system can be improved dramatically comparing to the uncoded QPSK system in the multipath fading and multi-user channel environments.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.15 no.1
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• pp.20-26
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• 2015

It is very difficult to design an underwater communication system because of multipath, Doppler effects, noise, and attenuation. These factors lead to errors in the communication performance and maximum propagation distance. In this study, we calculate the distance that can be realized using the direct-sequence code division multiple access (DS-CDMA) technique with direct-sequence spread spectrum (DSSS) in an underwater communication system considering only the attenuation and noise. We also compare the estimated and calculated propagation distances obtained for several different scenarios.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.6
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• pp.906-911
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• 2001

In this paper, LPI(low probability of intercept) and AJ(anti jamming) performance of the chirped BPSK system are analyzed. In the chirp method the cyclostationary of the signal is eliminated, since the instantaneous frequency is varied randomly within the whole spread bandwidth. Therefore, chirp method is considered for good LPI system against DAM(delay-and-multiplier) or SC (squaring circuit) interceptor which detects the chip rate or carrier frequency. Longer chirp duration makes the LPI performance better. From the simulation results, the chirp method has better AJ performance than DS(direct sequence) system in the PBNJ(partial band noise jammer) channel. At the same JSR(jammer to signal power ratio) level, chirped BPSK system has more robust AJ performance against MTJ(multi-tone jammer) than PBNJ.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.8C
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• pp.697-708
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• 2010

In this paper, we compare the timing synchronization performance of the adaptive filter to that of the correlator in direct sequence spread spectrum (DS/SS) systems. The test variables used in the code synchronization are statistically analyzed for both schemes, and then the obtained results are used in calculating the detection and false alarm probabilities. Based on the derived probabilities, the synchronization performance is compared and the simulation is followed. Analysis and simulation results show that the correlator outperforms the adaptive filter under most synchronization environments.

• Journal of Communications and Networks
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• v.5 no.4
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• pp.290-302
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• 2003

Ultra wide band (UWB) radio has recently attracted increased attention due to its expected unlicensed operation, and potential to provide very high data rates at relatively short ranges. In this article we briefly describe some main candidate multiple access and modulation schemes for UWB communications, followed with their power spectral density calculation and properties. We also present some illustrative capacity results, and provide a discussion of the impact of network topology on multiple access capacity.

• Proceedings of the Acoustical Society of Korea Conference
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• 1993.06a
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• pp.276-279
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• 1993

이 논문에서는 페이딩이 있는 채널에서 충격성 잡음이 있을 때 부호 상관 수신기를 쓰는 DS/SSMA 시스템의 성능을 분석하였다. 좀 더 자세히 말하면, 확산 수열이 짧을 때에는 직접 계산으로, 확산 수열이 길 때에는 근사식으로 부호 상관 수신기를 쓰는 DS/SSMA 시스템의 비트 오류 발생 확률을 얻었다. 이를 통해 사용자가 한 사람일때에는 이 시스템의 성능이 신호대 잡음비의 변화에 크게 영향을 받지 않는다는 것을 보였다.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.8
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• pp.867-873
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• 1988

The degradation due to channel distortion in a quadrature modulation system from the ideal constant values over the bandwidth of a direct sequence spread spectrum signal are considered. Through using series expansion for the channel gain and phase response, the degradation in the correlator output at the receiver is found as a function of the parameters involved , including phase error, delay error, linear gin variation, quadratic gain variation, and quadratic phase variation.

• The Magazine of the IEIE
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• v.21 no.7
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• pp.43-51
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• 1994

본 논문에서는 최근 주목을 받고 있는 대역확산 통신방식을 이용한 무선LAN 시스템의 하드웨어 구현에 관해 논한다. 내용으로는 직접확산 (Direct Sequence Spread Spectrum (DS/SS)) 통신방식을 이용한 무선 LAN 전송부 구조, 디지탈 정합필터를 이용한 역확산 및 비동기 DS/SS 수신기 구조, DBPSK 및 DQPSK 변복조 방식, Timing 및 Clock 복원, 그리고 Carrier Sensing 방식등이 포함된다. 또한 실제 시스템 구현을 위해 필요한 몇가지 변수들에 대해서도 논한다.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.493-496
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• 2003

This paper studied the method to improve the reliability with the simple structure and the decreased calculation of Micro-Controller(uC) in Power Line Modem. We have implementation the program which correct the 1-bit error of the $\mu$C within the control system and the DS/SS(Direct sequence/spread spectrum) by adding the simple circuit between a single chip powerline transceiver IC and a uC.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.642-645
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• 2001

본 논문에서는 전력전달 매체인 전력선을 이용하여 신뢰성 있는 통신환경을 구축하기 위해 필요한 전력선 통신 시스템에서의 임피던스, 잡음, 특성 등을 고찰했다. 이를 바탕으로 기존 네트워크에 사용 되어온 DS-SS(Direct sequence-Spread Spectrum) 기법을 전력선 통신에 적용하여 전력선통신 시스템을 구성하고 다중 액세스 기법인 CSMA를 적용하여 시스템 효율에 대한 성능 평가를 하였다.