• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.11A
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• pp.1087-1094
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• 2008

In this paper, we propose the acquisition method of the Cyclic-Prefix CDMA using Good-Autocorrelation-Sequence (GAS-CP-CDMA) system. The sequences for GAS-CP-CDMA are m-sequence and constant amplitude zero autocorrelation code (CAZAC) with good autocorrelation property. The GAS-CP-CDMA system is proposed for interference cancellation in multi-user and -path environment in co-cell. However, the reliable initial acquisition in multi-path fading channel and multi-user system environment is crucial. In this paper, non-coherent power detector and threshold value are used for discriminating signal acquisition. The sequence used for computer simulation is CAZAC. The simulation results show proper threshold value depends on the number of users. Through the computer simulation, we draw setting up method of the optimum threshold value for the GAS-CP-CDMA system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.9
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• pp.1730-1738
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• 1994

Broadband code division multiple access(B-CDMA)previously proposed for personal communication services(PCS) is not suitable for high-speed data services with large variations in speed, because it is designed only for low-speed voice calls with small variations in speed. Meanwhile, hybrid intra-cell TDMA/inter-cell CDMA(Hybrid TDMA/CDMA) recently proposed could accomodate high-speed services easily because of its internal use of the TDMA scheme, but there would be much inefficiency in treating variable bit rate services due to the intrinsic properties of TDMA transmission scheme, In this paper, a media access control(MAC) protocol, called Resevation TDMA/CDMA, which uses a reservation scheme similar to the one in the packet reservation multiple access(PRMA) protocol to compensate for these shortcomings is proposed. In addition, the performance of this protocol is analyzed and compared with conventional protocols by computer simulation. According to the simulation results, it has been shown that the proposed Reservation TDMA/CDMA scheme could support various transmission rates of user data traffics easily, and it could utilize the variations of the treansmission rates in each active call more efficiently.

• Proceedings of the Optical Society of Korea Conference
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• 2002.07a
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• pp.152-153
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• 2002

1980년대 CDMA의 기술을 광통신에 도입된 이후 최근까지 광 CDMA에 대한 연구는 실험실 수준에서 이루어져 왔다. 최근 인터넷 사용의 급격한 증가로 가입자까지 광신호를 보내려는 노력이 많이 이루어지고 있으며, 그 방안으로 많은 광 가입자를 수용할 수 있는 광 CDMA 기술이 각광 받으면서 광CDMA 시스템을 생산하는 회사가 생기기 시작하고 있다. 광 CDMA 기술에는 시간지연을 이용한 방법, 광 스위치를 이용한 방법[1], FBG/AWG를 이용한 방법, 공간필터를 이용한 방법 등이 연구되어 지고 있으며, 이중에서 광 스위치를 이용한 광 CDMA 방식은 encoder/decoder의 채널을 변경하기 쉬운 장점을 지니고 있다. (중략)

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.5
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• pp.11-16
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• 1998

DS/CDMA systems for the high speed communication require high code rats. In discrete time CDMA receivers, the performance degradation, caused by the phase difference between transmission code and reference code, increase the sampling frquency of the receiver. This increment of the sampling frequency makes hard to implement high speed CDMA systems. This paper analyzes the SIR(signal to interference Ratio) performance of the discrete time DS/CDMA system, based on the code phase difference. The results of this paper may be useful to study a low-sampling CDMA receiver.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.6A
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• pp.767-774
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• 1999

In this paper, we compare the performance of asynchronous W-CDMA system with different bandwidth. We take into consideration of wideband multipath channel environment which consists of discrete multipath components whose strength is Rayleigh distributed. Each CDMA system different bandwidth experience different effects of multipath because there are different number of multipath within one chip duration according to the spreading bandwidth. We derive the average error probability versus the capacity, and compare the capacity of W-CDMA systems using the RAKE receiver with EGC diversity.

• Proceedings of the KIEE Conference
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• 2004.07d
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• pp.2655-2657
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• 2004

기존의 DS-CDMA 방식은 잡음이 많거나 채널 왜곡이 심한 환경에서는 성능이 급속히 저하하는 현상이 나타난다. 이러한 문제점 해결을 위한 다양한 연구들이 현재 진행되고 있으며, 본 논문에서도 이에 대한 해결방안을 제시한다. Chirp 방식은 레이더와 같은 변복조 방식에 다양하게 사용되고 있으며, 원하는 주파수 대역으로 쉽게 이동할 수 있고. 구현이 용이하다는 장점이 있다. 본 논문에서는 다중 접속이 가능한 DS-CDMA 기술과 chirp 변복조 기술을 결합한 Binary Chirp DS-CDMA(BCDS-CDMA) 방식을 제안한다. 제안한 DS-CDMA 시스템 성능을 평가하기 위하여, 가우시안 환경에서 기존의 DS-CDMA 방식과 비교 실험을 하였으며, 실험 결과 chirp을 이용한 방식이 DS-CDMA 보다 개선된 성능을 지니고 있음을 알 수 있었다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.6B
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• pp.593-600
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• 2002

The reverse link signal power required for multimedia traffic in multipath faded single-code (SC-) and multi-code CDMA (MC-CDMA) systems is investigated. The effect of orthogonality loss among multiple spreading code channels is herein characterized by the orthogonality factor. The required signal power in both the CDMA systems is then analyzed in terms of the relative required signal power ratio of data to voice traffic. The effect of varying system parameters including spreading bandwidth, the of orthogonality factor, and the number of spreading codes are examined. Analytical results show that MC-CDMA users transmitting only a single traffic type require significantly more power than SC-CDMA users with only a single traffic type. On the other hand, MC-CDMA users transmitting multimedia traffic require power levels approximately identical to SC-CDMA users with multimedia traffic. The results can be used in the design of radio resource management (e.g., power allocation) scheme for wireless multimedia services.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.6B
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• pp.569-578
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• 2002

This paper proposes a new multicarrier code division multiple access (CDMA) system. The proposed multicarrier CDMA system provides the advantages that the transmission bandwidth is more efficiently utilized by using divided spreading sequence, time and frequency diversity is achieved in frequency selective nultipath (acting channel, and inter-carrier interference (ICI) can be minimized by using specific data and code pattern. In this system, transmitted data bits are serial-to-parallel converted to some parallel branches. On each branch each bit is direct-sequence spread-spectrum modulated by divided spreading sequences and transmitted using orthogonal carriers. The receiver providers a Rake for each carrier, and the outputs of Rakes are combined to get time and frequency diversity. This multicarrier CDMA system allows additional flexibility in the choice of system parameters. Upon varying system parameters, bit error rate (BER) performance is examined for the proposed multicarrier CDMA system. Simulation results show that the proposed multicarrier CDMA scheme can achieve better performance than the other types of conventional multicarrier CDMA systems.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.4
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• pp.116-124
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• 2011

For Binary CDMA network, communication can be accomplished only within a Pico-net on the boundary of management by the master station because it manages network resources of each entity. In this research, we try to overcome these limits and extend the application for Binary CDMA system to broad-band network. We suggest a new Binary CDMA router such that network is devised by cell unit and multiple Pico-net and a unique address is assigned to each Pico-cell to relaying data between Pico-cells.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.4
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• pp.639-644
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• 2001

Sequence Code Division Multiple Access) and TDMA(Time Division Multiple Access) system. In this system, the narrowband TDMA signals can cause intolerant interferences to CDMA signals. In this paper, DS-CDMA/TDMA frequency sharing system have been analyzed in AWGN(Additive white Gaussian Noise), MAI (Multi Access Interference) and NI(Narrowband Interference) environment. Also, performance improvement has been obtained by adopting an adaptive notch filtering scheme using complex filter bank and CCI canceller.