• Annual Conference of KIPS
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• 2005.11a
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• pp.1247-1250
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• 2005

이 논문은 multicarrier CDMA 이동 통신 시스템에서 직-병렬 혼합 pseudo-noise (PN) 코드 동기 획득 기술을 제안 했으며 다중경로 페이딩 채널에서 multiple access interference (MAI) 의 영향을 분석하였다. 직-병렬 혼합 동기 획득 방식은 입력되는 코드 위상의 불확정 영역 전체를 직렬 획득 방식과 병렬 획득 방식을 조합하여 탐색하는 방식이다. 이러한 방식은 완전 병렬획득보다 MAI의 환경에서 mean acquisition time (MAT)이 조금 늦어지지만 하드웨어의 구조를 훨씬 단순화 할 수 있다. 검파 및 오경보 확률을 closed-form 표현으로 mean acquisition time (MAT)를 유도하였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.05a
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• pp.509-513
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• 2002

This paper presents a semi-blind Minimum Mean Square Error (MMSE) beamforming adaptive algorithm used far OFDM/CDMA combined system. The proposed algorithm exploits the transmitting pilot signal in the initial period of the transmission to update the weight vector. Then it applies the blind adaptive period to update the weight vector, in which the pilot signal is no longer used. The derivation of the algorithm based on the Mean Square Error (MSE) criterion is also presented. Computer simulation is carried out to verify the performance of the proposed approach.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.11a
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• pp.66-66
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• 2004

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.11a
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• pp.345-345
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• 2004

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.07a
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• pp.377-377
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• 2004

• Journal of information and communication convergence engineering
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• v.2 no.2
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• pp.71-75
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• 2004

In non-selective frequency environment, it is difficult to take the advantage of path diversity. In the literature, some methods have been proposed to solve the issue. This paper presents a new method to obtain the resolvable path in Indoor Multi-carrier Code Division Multiple Access (MC-CDMA) system by using downlink beam forming. With the aid of downlink beamforming, the most reliable path is found and chosen for the communication link. The new approach is evaluated in term of bit error rate (BER) and power consumption. The simulation results show that the new approach can get better BER performance. However, the cost of BER improvement is a small degradation in power reservation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.6
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• pp.1056-1061
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• 2001

In this paper we have evaluated the degree of performance improvement in Multi-Carrier CDMA system adopting CCI canceller against MUI under mobile channel coexisting MU which is a major interference degrading the performance of Multi-carrier CDMA system. As a result of analysis, BER performance was improved by adopting CCI canceller and it was found that the amount of performance improvement was largely increased as Eb/No became higher. As an example, in case that data service BER = 10$^{-5}$ must be achieved with $E_{b/}$ $N_{o}$ = 12 ㏈, 4 users could be supported without CCI canceller while 30 users could be supported with CCI canceller, Also, we found that performance improving effect of 5$\times$10$^{-3}$ in a point of view BER could be achieved by adopting CCI canceller with fixed $E_{b/}$ $N_{o}$. o/. o/.

• Proceedings of the Korea Association of Information Systems Conference
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• 2001.12a
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• pp.166-178
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• 2001

Lately the National Technology Standard of IMT-2000 service in Korea was decided for both technology standards (cdma-2000, W-CDMA), and consequently the comprehensive countermeasures against the Technology Standards are all the more emphasized. Especially to private enterprises which were selected as service carriers for IMT-2000 service in Korea, making corresponding strategies in relation to both technology standards must be settled without delay. The Government also should serve the development of the I&T Industry through the various processes of adopting the policies and working out strategies In relation to Technology Standards of IMT-2000. Therefore in this paper, 1 would like to survey the features of both Technology Standards(cdma-2000, W-CDMA) and to propose the hereafter corresponding strategies in relation to IMT-2000 services.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.8
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• pp.697-703
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• 2013

We propose an efficient frequency-time domain resource allocation scheme in multi-carrier (MC) direct-sequence code-division multiple-access (DS/CDMA) communications. We consider, as a power allocation strategy in the frequency domain, transmitting each user's DS waveforms over the user's sub-band with the largest channel gain. We then consider rate adaptation in the time domain, where the data rate is adapted such that a desired transmission quality is maintained. We analyze the achievable average data rate of the proposed scheme with fixed average transmission power, and compare the performance to single carrier DS/CDMA systems with power and rate adaptations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.11A
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• pp.1620-1629
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• 2000

본 논문에서는 켑춰를 갖는 슬랏 ALOHA 방식을 이용한 패킷 무선망의 성능을 분석하였다. 접속을 획득하기 위해서 켑춰효과를 이용하고 트래픽은 포아슨 랜덤프로세서로 가정하였을며 공간트래픽밀도는 실제적인 이동통신환경을 나타내는 puncturing 종형분포로 가정하였다. 패킷은 접속을 획득하는 헤더부분과 데이터 정보가 들어있는 데이터 부분으로 나눈다헤더부분은 공통확산부호를 갖는 DS에 의해 확산되고 데이터부분은 간섭전력과재밍에 강하고 고속의 데이터 전송시 성능향상을 기대할 수 있는 MC DS/FH에 의해 확산된다. 이동통신채널은 도심 전파의 다중경로 채널에 대한 다양한 헤이딩 환경을 제공해 주는 나카가미 페이딩 채널을 가정하였다. 동일한 지연시간에 반송주파수수를 증가시킴에 따라 높은 co널 처리 용량을 얻었으며 FH를 MC/DS/CDMA에 사용함으로서 간섭전력의 변화가 심한 환경에서 시스템의 성능을 일정하게 유지시켰다. 또한 Hard-limiting 상관수신기를 사용함으로써 페이딩이 심한 환경에서 패킷 무선망의 성능을 개선시켰다.