• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(1)
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• pp.185-188
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• 2000

In this paper, performance of a PN code acquisition scheme is analyzed and simulated for a DS/CDMA overlay system where a CDMA user and a narrowband user coexist in the same frequency band. To suppress the NBI, an interference suppression filter is employed at the receiver front-end. From the simulation results, it is shown that the interference suppression filter is very effective for suppression of the NBI and rapid PN code acquisition in a DS/CDMA overlay environment. It is also shown that the one-sided tap number of 5 fur interference suppression filter is sufficient to suppress the NBI.

• 한국위성정보통신학회논문지
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• 제12권1호
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• pp.120-124
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• 2017

본 본문에서는 Code division multiple access (CDMA) 사용자와 협대역 사용자가 동일 주파수 대역에 존재하는 곳에서 direct sequence/CDMA (DS/CDMA) 오버레이 시스템에 대해 pseudorandom noise (PN) 코드 획득 성능 상의 안테나 다이버시티의 효과가 분석되고 시뮬레이션 되었다. 시뮬레이션 결과는 안테나 다이버시티가 PN 획득 성능에 매우 효과적임을 보인다. 이 논문의 결과는 DS/CDMA 오버레이 환경에서 동기 구조의 설계에 적용될 수 있다.

• 한국통신학회논문지
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• 제28권7A호
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• pp.440-450
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• 2003

The reverse link of a spectrally overlaid macrocell/microcell cellular CDMA system supporting multimedia traffic is characterized in terms of the required signal power, interference, and capacity. Several narrowband subsystems are overlaid with a wideband subsystem in macrocells, while a single wideband subsystem is operated in a microcell with the same spectrum as the macrocell wideband subsystem. Using a typical propagation model the reverse link signal power and interference are characterized as the relative user signal power and the cross-tier interference factors between the macrocell and the microcell. The reverse link capacity of the overlay system is then analyzed. Analytical results show that the dominant parameters affecting the system performance are the spectral overlay ratio and the distance between the microcell and macrocell base stations. In particular, when the distance equals a half of macrocell radius, optimum performance can be achieved by minimizing the cross-tier interference factors. These results can be applied to CDMA multimedia network planning in heavily populated traffic areas.

• 한국멀티미디어학회논문지
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• 제16권7호
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• pp.862-869
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• 2013

In order to support a cell-independent traffic asymmetry, the conventional TDD system cannot avoid crossed time slot (CTS) interference. Moreover, the TDD/FDD hierarchical overlay cellular systems is taken into account as a generally accepted cell model in a heterogeneous radio environment. In this paper, we propose an interference resolving radio resource allocation technique in a TDD-OFDMA cellular system that overlays a FDD-CDMA cell. In our proposed scheme, we exploit under-used FDD-CDMA uplink resource by TDD mobile abiding by a region based time slot(TS) allocation which in turn mitigates CTS interference considerably. It is demonstrated that combined with under-used resource utilization scheme based on mobile's location, the proposed technique can reduce CTS interference considerably and support the asymmetric traffic in TDD system.

• 한국통신학회:학술대회논문집
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• 한국통신학회 1995년도 추계종합학술발표회 논문집
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• pp.73-78
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• 1995

• 한국통신학회:학술대회논문집
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• 한국통신학회 1995년도 하계종합학술발표회 논문집
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• pp.147-150
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• 1995

• 한국통신학회논문지
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• 제22권4호
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• pp.737-747
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• 1997

스펙트럼 효율을 높이기 위해 기존의 마이크로파 협대역 시스템 위에 동일한 대역을 사용하는 셀룰라 CDMA 시스템을 오버레이시킨 환경에서, CDMA 시스템의 성능을 분석하였다. 협대역 시스템으로부터의 간섭을 제거하기 위해 최소 평균 자승 알고리즘을 적용한 선형 추정 필터를 사용하였다. 다중 경로 리시안 페이딩 채널로 특징 지워지는 개인 휴대 통신 채널에서의 성능을 분석함에 있어서, 원근단 문제를 해결하기 위한 전력 제어 기법 및 통화 인계, 다중, 경로 다이버시티 등을 고려하였다. 또한 인터리빙과 채널 부호화 기법을 사용하여 CDMA 시스템의 오율 성능을 분석하였다.

• 한국통신학회논문지
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• 제19권7호
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• pp.1374-1389
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• 1994

본 논문에서는 개인휴대 통신 시스템을 위해 시간도약부호와 2진직교시퀸스를 사용하는 새로운 M진직교 부호분할 다원접속방식을 제안한다. 제안된 방식의 변조기 출력신호는 넓은 대역폭 점유와 낮은 스펙트럼밀도의 특성을 갖고 있어, 현대의 무선 주파수채널을 점유하고 있는 협대역 전송방식과의 주파수 중첩사용에 매우 유용하다. 본 논문은 변조기 출력신호의 전력스펙트럼에 대한 분석을 통하여 시스템의 특성을 조사하고 스펙트럼 중첩에의 응용 가능성을 입증한다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(1)
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• pp.49-52
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• 2000

The Multi-Code CDMA systems that are proposed as an effective transmission methodology in the IMT-2000 systems allow higher rate services under the IS-95 CDMA infrastructure. The Multi-Code CDMA systems convert the higher rate data into the lower rate by serial to parallel operation and spread the converted data streams by the multiple walsh codes, and its mobile receiver needs multiple walsh generators and data correlators to demodulate simultaneously multiple walsh code channels. Therefore, the number of data correlators is increased as the number of traffic channels increases. In this paper, we proposed the new structure of the data correlators using walsh overlay coding, the shared accumulator, and FWHT(Fast Walsh Hadamard Transform) algorithm for reducing the bottle-neck effect resulting the increase of the number of data correlators.

• 한국통신학회논문지
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• 제21권4호
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• pp.961-971
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• 1996

The effect of inband TDMA narrow band jammers to DS-CDMA system performance and the suppression techniques are investigated using Monte Carlo simulations. TIA stantard North American Digital Cellular wea used as jammer. Levinson Dubin and conventional recursive least square algorithm were emphasized since these techniques can be implemented with a few DSPs for CDMA application. Two filter structures, i.e., complex suppression filter and real suppression filter in each inphase and quadrature channels, are investigated and their performances are compared. Complex suppression filter with Levinson Durbin algorithm of 20msec updata rate is the most promising with respect to implementation and performance poit of view. Implementation feasibility is discussed and the channel capacity lost by suppression is computed.