• 한국멀티미디어학회논문지
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• 제12권6호
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• pp.824-832
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• 2009

Multi-radio multi-channel Wireless Mesh Network requires an effective management policy to control the assignment of channels to each radio. We concentrated our investigation on modeling method and solution to find a dynamic channel assignment scheme that is adapted to change of network traffic. Multi-path routing scheme was chosen to overwhelm the unreliability of wireless link. For a particular traffic state, our optimization model found a specific traffic distribution over multi-path and a channel assignment scheme that maximizes the overall network throughput. We developed a simple heuristic method for channel assignment by gradually removing clique load to obtain higher throughput. We also presented numerical examples and discussion of our models in comparison with existing research.

• 한국정보통신학회논문지
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• 제14권7호
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• pp.1723-1728
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• 2010

본 논문에서는 뮤직 콘텐츠의 무분별한 사용의 피해를 줄이고 대형 매장과 임의의 공간과 공간사이 다른 콘텐츠를 서비스 할 수 있는 Multi-Channel Internet Radio Platform 에 대해 설계 방안을 제공하고 구현 연구를 진행한다. 본 플랫폼은 Multi-Channel Connection을 위한 Application 설계방법과 그에 따른 Multi Stream을 위한 Hardware Path를 구현하는 방법 제안 및 구현 결과를 제공한다.

• 한국통신학회논문지
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• 제21권4호
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• pp.1027-1037
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• 1996

This paper presents an impulse response of the multi-path channel using KS-GCR(Korean Standard Ghost Cancel Reference) signal. Using the property of the KS-GCRsignal, we can get the impulse response of the multi-path channel from circular cross correlation of the received DS-GCR signal and the orginal KS-GCR ternary sequence. Therefore impulse response of the multi-path channel can be used to design the the ghost cancellation filter if it is designed to have inverse characteristics of multi-path channel. This paper shows that the ghost occurred from the multi-path channel can be cancelled by using the impulse response and preceding ghost cancellation algorithm.

• 한국디지털정책학회:학술대회논문집
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• 한국디지털정책학회 2005년도 춘계학술대회
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• pp.277-283
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• 2005

In this paper, the performance of high data rate-wirelesss personal area network(HDR-WPAN) system is analyzed under multi-path indoor channel. In the analysis, Saleh and Valenzuel channel model is used for the multi-path indoor channel. From the results, HDR-WPAN system has reliability of 10-5 at Eb/No = 18.5dB in multi-path indoor channel. It is a suitable performance for high data rate personal area network applications.

• 한국항행학회논문지
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• 제7권1호
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• pp.51-58
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• 2003

일반적으로 다중경로는 무선통신에서 불필요한 특징을 나타낸다. 따라서 이러한 영향을 극복하기 위하여 다이버시티 수신이나 적응 어레이 기법이 제안되었다. 최근에는 스펙트럼 효율과 링크 신뢰도를 증가시키기 위해 MIMO 기법이 산란 무선 채널에서 다중경로를 이용하기 위해 고안되었다. 본 논문에서는 경로 상관 페이딩 채널에서 MIMO Multi-Carrier CDMA 시스템의 채널 용량을 평가한다. 그리고 MIMO 시스템의 채널 용량을 SISO 시스템의 채널 용량과 비교한다. 결과로부터 경로 상관을 갖는 MIMO Multi-Carrier CDMA 시스템은 SISO 시스템의 채널 용량에 비하여 우수함을 알 수 있다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권4호
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• pp.1063-1075
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• 2012

To locate an object accurately in the wireless sensor networks, the distance measure based on time-delay plays an important role. In this paper, we propose a maximum likelihood (ML) time-delay estimation algorithm in multi-path wireless propagation channel. We get the joint probability density function after sampling the frequency domain response of the multi-path channel, which could be obtained by the vector network analyzer. Based on the ML criterion, the time-delay values of different paths are estimated. Considering the ML function is non-linear with respect to the multi-path time-delays, we first obtain the coarse values of different paths using the subspace fitting algorithm, then take them as an initial point, and finally get the ML time-delay estimation values with the pattern searching optimization method. The simulation results show that although the ML estimation variance could not reach the Cramer-Rao lower bounds (CRLB), its performance is superior to that of subspace fitting algorithm, and could be seen as a fine algorithm.

• 한국통신학회논문지
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• 제24권8A호
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• pp.1099-1106
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• 1999

본 논문에서는 다중사용자/다중경로 환경에서 다중반송파 CDMA 시스템의 오류확률을 해석적으로, 구하고, 다중 사용자, 다중반송파, 다중경로에 의한 간섭의 영향을 분석하였다. 또한 다중반송파 시스템에 대한 역상관 검출기(decorrelating detector)를 결합한 다중반송파/다중사용자/다중경로 결합 검출 방식을 제시하고 성능 및 역상관 과정에 의한 백색가우시안 잡음(AWGN)의 증가를 분석하였다. 제안한 결합 검출 방식의 오류 확률은 하나의 상용자만이 있는 경우의 이상적인 성능에 근접하였다.

• International Journal of Computer Science & Network Security
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• 제23권7호
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• pp.1-8
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• 2023

An Orthogonal Frequency Division Multiplexing (OFDM) based wireless communication system has drawn wide attention for its high transmission rate and high spectrum efficiency in not only radio but also Underwater Acoustic (UWA) applications. Because of the narrow sub-carrier spacing of OFDM, orthogonality between sub-carriers is easily affected by Doppler effect caused by the movement of transmitter or receiver. Previously, Doppler compensation signal processing algorithm for Desired propagation path was proposed. However, other Doppler shifts caused by delayed Undesired signal arriving from different directions cannot be perfectly compensated. Then Receiver Bit Error Rate (BER) is degraded by Inter-Carrier-Interference (ICI) caused in the case of Multi-path Doppler channel. To mitigate the ICI effect, a modified Delay and Doppler Profiler (mDDP), which estimates not only attenuation, relative delay and Doppler shift but also sampling clock shift of each multi-path component, is proposed. Based on the outputs of mDDP, an ICI canceling multi-tap equalizer is also proposed. Computer simulated performances of one-tap equalizer with the conventional Time domain linear interpolated Channel Transfer Function (CTF) estimator, multi-tap equalizer based on mDDP are compared. According to the simulation results, BER improvement has been observed. Especially, in the condition of 16QAM modulation, transmitting vessel speed of 6m/s, two-path multipath channel with direct path and ocean surface reflection path; more than one order of magnitude BER reduction has been observed at CNR=30dB.

• 한국통신학회논문지
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• 제28권8B호
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• pp.674-682
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• 2003

This paper presents the studies on wireless channel modeling and reverse link synchronization of CATV. This paper analyzes multi-path fading channel to the cause of signal distortion in the wireless communication environment. We represent the microwave link characteristics according to the channel model. Multi-path channel can affect fading.

• 한국위성정보통신학회논문지
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• 제5권1호
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• pp.54-57
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• 2010

위성 기반 측위 시스템은 위치 기반 기술의 핵심 기술로서, CDMA 시스템을 사용한다. CDMA 시스템에서 원활한 위치 측위를 하기 위해서는 확산 부호의 정확한 동기가 이루어져야 한다. 본 논문은 확산 부호의 동기 기법 가운데 부호 추적 기법에 초점을 맞춘다. 특히 다중 경로 환경에서 기존의 부호 추적 기법인 DLL 방법은 적합하지 않다. 본 논문은 수신 신호에서 다중 경로 신호를 축출하여 이를 부호 추적 기법에 사용하는 방법을 제안한다. Spirent simulator를 이용하여 제안 기법을 검증하고 성능 평가를 보인다.