• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1994.06a
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• pp.159-162
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• 1994

• The Magazine of the IEIE
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• v.21 no.7
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• pp.27-36
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• 1994

• JOURNAL OF ELECTRICAL WORLD
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• s.257
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• pp.83-89
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• 1998

공공업무용(국가, 전력, 가스, 상하수도, 소방$\cdot$구급, 철도 등) 이동통신시스템의 디지털화가 (일본) 전기통신기술심의로부터의 답신(1993년 4월)을 받아 우정자령(동년 11월)으로 고시되었다. 이에 따라 미쓰비시전기에서는 시분할다원접속(Time Division Multiple Access : TDMA)방식의 공공업무용 디지털이동통신시스템을 개발하였다. 여기에 이 시스템의 개요와 서브시스템의 내용을 상세하게 소개하기로 한다. 제어국$\cdot$기지국은 표준규격보다 우수한 기능을 실현하였고, 차량탑재이동국은 소형경량화를 도모하였으며, 계속해서 주파수분할 다원접속(Frequency Division Multiple Access : FDMA) 방식의 시스템에 대한 개발도 시행하여 최적의 시스템을 구축할 수 있도록 하고 있다. 또한 다른 주파수대를 포함한 공공업무용 디지털통신시스템의 법 정비가 순차적으로 진전될 전망이어서, 공공기관을 중심으로 급속히 이 시스템의 보급이 도모될 것으로 생각된다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.10A
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• pp.816-829
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• 2003

In this paper, we evaluate the performance of PN (Pseudo Noise) code based time hopping sequences for M-ary UWB (Ultra Wide Band) multiple access systems using the equicorrelated signal sets. In particular, we consider two different types of M-ary UWB systems in UWB indoor wireless multipath channels: The first type of the systems (System #1) has identical symbol transmission rate regardless of the number of symbols M since the length of signal pulse train is fixed while M increases, and the second type of the systems (System #2) has the same bit transmission rate regardless of M since the length of signal pulse train is extended according to the increase of M. We compare the proposed systems with those using the ideal random time hopping sequence in terms of the symbol error rate performance. Simulation results show that the PN code based time hopping sequence achieves quite good performance which is favorably comparable to that of the ideal random sequence. Moreover, as M increases, we observe that System #2 shows better robustness against multiple access interference than System # 1.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.686-690
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• 2003

직접 확산 부호 분할 다원 접속 (Direct Sequence Code Division Multiple Access : DS-CDMA) 시스템과 시분할 다원 접속 (Time Division Multiple Access : TDMA) 시스템을 동일 주파수 대역에서 중첩되어 전송할 때 DS-CDMA 신호에서의 TDMA 신호의 협대역 간섭이 문제된다. 본 논문에서는 DS-CDMA 신호의 협대역 간섭(narrowband interference : NI)를 제거하는 방법으로서 노치필터를 이용해서 협대역 간섭파 제거법을 제안하고, 간섭제거기(CCI canceller)를 이용해서 다중접속간섭을 제거하여 DS-CDMA 신호의 성능을 개선한다. 본 논문은 잡음, 다중접속 간섭 및 협대역 간섭환경에서 DS-CDMA 신호와 TDMA 신호의 주파수 공용 시스템에 적용할 때의 성능을 분석하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.7
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• pp.1118-1130
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• 1999

In this paper, error performance of DS/FH CDMA system has been analyzed in a radio channel which is characterized by near-far problem and multi-path fading. The DS/FH CDMA system adopts Maximum Ratio Combining(MRC) diversity and BCH(Bose-Chau dhuri-Hocquenghem) coding techniques to enhance system performance. Using the derived error probability equation, the error performance of DS/FH CDMA system has been evaluated and shown in figures to discuss as a function of PN code length(N), hopping rate(q), number of diversity branch(M), coding rate($\gamma$) and bit energy per noise power ratio ${E_b/N_o}$. The results show that DS/FH system is more effective to restrain the affection of near-far problem and multi-path fading than DS system. And there is a substantial enhancement in performance by employing an MRC diversity or BCH coding techniques. Consequently, we expected that proposed system structure is reliable to the voice communication system in near-far problem and multi-path fading channel.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.27-30
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• 1998

본 논문에서의 기존의 2선식 댁내 망을 이용하여 ISDN PRI(2.048MHz)급의 전송을 위해 DS-CDMA방식을 적용하는 방법을 제안한다. TE 와 NT 의 신호의 검출을 위해 자기의 확산코드와 정합된 단일 사용자 검출기를 사용할 수 있으나, 검출하려는 신호와 다른 사용자 신호간의 다원접속간섭(Multiple Access Interference)에 의해 시스템의 성능이 저하된다. 본 논문에서는 다원접속간섭을 효과적으로 제거할 수 있는 최소평균제곱오차 (Minimum Mean Squared Error) 다중사용자 간섭제거기를 사용하고 컴퓨터 모의실험을 통하여 성능을 분석한다.

• Information and Communications Magazine
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• v.20 no.2
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• pp.86-98
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• 2003

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.7
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• pp.1659-1666
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• 1998

The multicode CDMA systems that are widely studied as an effective transmission methodology in the IMT-2000 systems, employ orthogonal codes to transform high rate data into parallel, low rate data for simultaneous transmission. In this paper, we propose a new multicode CDMA system which achieves the same data rate and processing gain of the conventional systems, while significantly improves bit error rate performance by exploiting a convolutional code with code rate r=1/2 and a bi-orthogonal code. The simulation results for synchronous systems using maximal ratio combining Rake receivers under additive white Gaussian noise and multi-path fading channels, show significant improviements by the proposed system.

• 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.