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CCI 제거기와 복소필터뱅크를 이용한 주파수 공유 복합시스템의 성능 개선
강희조 東新大學校 2002 論文集 Vol.12 No.-
In this paper proposes a new techniques for the frequence sharing of DS-CDMA(Direct 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. The results show that there is a substantial enhancement in performance by employing the adaptive notch filtering and/or CCI canceller.
조음과 청취에 근거한 수업을 통한 한국인 대학생의 영어모음 발음 변화
강희조 대한언어학회 2022 언어학 Vol.30 No.4
This study tested whether the pronunciation of English vowels could improve through the explicit instruction based on the articulatory and auditory characteristics of English vowels, even during the pandemic, when oral practice was restricted. 30 university students who took an English pronunciation course participated in the study as the experimental group and they were taught English vowels with articulatory and auditory training. The 21 students in the control group listened to target sentences recorded by a native English speaker in an English listening and speaking course. At the beginning and at the end of the semester, the participants in both groups recorded 18 English sentences, four of which ([i], [ɪ], [ɛ], and [æ]) were acoustically analyzed. As Korean learners of English are known to have difficulties distinguishing those front vowels ([i] vs. [ɪ] and [ɛ] vs. [æ]), the F1 differences in each of those vowel pairs were statistically analyzed. The results showed that only female students belonging to the experimental group marked a marginally meaningful improvement in the vowel pair of [ɛ] and [æ]. The author concludes that it is possible to partially enhance the English vowel pronunciations of Korean students through implicit listening and explicit articulatory training. Teaching methods to improve students’ pronunciation are suggested.
간섭과 페이딩환경에서 스펙트럼 확산(SS) 통신 신호의 다이버시티 수신 특성에 관한 연구
강희조,이권현,조성준 한국통신학회 1994 韓國通信學會論文誌 Vol.19 No.5
직접 스펙트럼 확산(DS)방식과 주파수 도약 확산(FH)방식을 혼합시킨 하이브리드 DS/SFH-SSMA 시스템에 대해서 m-분포 페이딩 체널에서의 비동기 MDPSK 신호의 오율특성을 구하고, 다이버시티 기법과 부호화 기법을 함께 도입하였을때의 오율특성도 구했다. 얻은 결과로부터 페이딩의 심도 m에 따른 오율성능의 열화 정도를 알 수 있었는데 레일리 페이딩 환경(m=1)에서는 도약 주파수를 증가시키면 hit될 확률이 감소하므로 다중접속에 의한 간섭의 영향이 감소하고, 호핑수(q)가 사용자수(K)보다 무척 크고, 비트 에너지 대 잡음 전력비(E/N)가 높을때는 다중접속에 의한 간섭은 무시되어 다중경로에 의한 영향이 지배적이 된다는 것과, 비트 에너지 대 잡음 전력비가 낮을때는 가우스 잡음의 영향이 지배적이 되어 호핑수(q)에 관계없이 오율성능이 일정해진다는 것을 알았다. The error performance of M-ary differential phase shift keying (MDPSK) through m-distribution fading channel in hybrid direct sequence/slow frequency hopped spread spectrum multiple access (DS/SFH-SSMA) systems has been evaluated, and also the error probability has been evaluate when adopting diversity technique and coding technique. From the results, we know that the error performance more deteriorates as depth of fading becomes deeper. In Rayleigh fading environment (m=1), increasing of the number of frequency hopping (q) reduces the effect of multiple access interference, because it decreases the probability a hit. When q is much larger than the number of user (K), the probability of error in high E/N region is dominated by the multipath interference while the multiple access interference is negligible. In lower E/N region, the probability of error is independent of q because the effect of gaussian noise becomes dominat.
이동체 통신에 있어서 멀티슬롯 할당을 이용한 적응변조방식에 관한 성능해석
강희조 東新大學校 1998 論文集 Vol.10 No.-
This paper proposes an adaptive multislot allocation algorithm in order to achieve larger system capacity and higher throughput data transmissions. The proposed system is the combination of the slow adaptive modulation system, in which the base station dynamically assigns optimum modulation parameters measuring the C/N (carri-to-noise power ratio) of each transmission terminal, and the multislot allocation scheme, in which the base station flexibly allocates an appropriate number of TDMA data slots according to the instantaneous load conditions. Computer simulations confirm that the proposed system can tremendously improve average message delay characteristics in comparison with the conventional fixed slot allocation method.
Nakagami 페이딩 채널에서 MRC 다이버시티와 채널 부호화 기법을 사용한 DS/CDMA BPSK 시스템의 블록 오율 성능 개선
강희조,노재성,조성준 한국통신학회 2000 韓國通信學會論文誌 Vol.25 No.3
In this paper, MRC(Maximum Ratio Combine) diversity, (23, 12) Golay code, (7, 5) Reed-Solomon code, and (3, 1) majority selection code are employed to improve the performance of DS/CDMA BRSK in Nakagami fading channel. and MRC diversity combined with other coding techniques is suggested, with which, the performance of DS/CDMA BRSK is compared and analyzed. Also, system required Eb/N0 to meet BER=10-5 for multi user data communication is obtained according to each techniques. From the results, when each techniques is employed to DS/CDMA BRSK system. coding employed system shows better performance than diversity employed system. Especially, Golay code shows better performance than oter codes. also MRC diversity is employed, the number of multiple access user to meet data communication requirement of BER=10-5 can accomodate up to 8 users. and when each code is employed, Golay code, majority selection code, and Reed-Solomon code shows the capacity of 14, 12, and 10 user respectively. But MRC diversity combined with coding techniques can reduce restriction of multiple access user. However, it is desirable these combined technique are employed according to service types and requirements provided.
m-분포 페이딩 환경하에서의 DS/QPSK 신호의 오율특성
강희조,김상범,조성준 한국통신학회 1991 韓國通信學會論文誌 Vol.16 No.12
톤간섭과 잡음 환경하에서 m-분포 페이딩 채널을 통해 수신되는 DS/QPSK 신호의 오율식을 유도한 후 이를 수치계산하여 그림으로 나타내어 검토했다. 오율식의 유도는 두 가지 경우에 대하여 행했다. 즉, 하나는 신호만 페이딩의 영향을 받는 경우이고 다른 하나는 신호와 간섭이 동시에 페이딩의 영향을 받는 경우이다. 수치 계산하여 얻어진 결과로부터 신호만 페이딩의 영향을 받는 경우보다 신호와 간섭이 동시에 페이딩의 영향을 받는 경웨 오율특성이 더 열화되는데 직접확산을 이용하면 큰 오율개선이 이루어진다는 것을 알수 있었다. 그러나 그 오율의 개선폭은 간섭과 페이딩의 영향이 약해지면 약해질수록 작아진다는 것을 확인할수 있었다. The error rate equation of QPSK signal received through m-distribution fading channel in tone interference and Gaussian noise environments has been derived and evaluated numerically to be shown in figures. The derivation has been done for two cases. The one case is that only the signal is under the influence of fading and the another case is that signal and interference are under the influence of fading simultaneously. The evaluated results show that the error that performance when fading influences signal and interference simultaneously is worse than that when fading influence signal only. Also the results show that a late amount of improvement can be gained by direct sequence spread spectrum system and the amount of improvement becomes small as the influence of interference and fading becomes small.