지하 무선 CDMA 망의 전파 측정 및 Micro BTS의 성능 분석

안호중,노재성,조성언,조성준 한국항공대학교 1998 論文集 Vol.36 No.-

지하 무선망에서 CDMA(Code Division Multiple Access)시스템의 용량과 품질은 다중 사용자 간섭과 임펄스성 간섭의 영향을 받는다. 그러므로 CDMA 시스템에서는 간섭을 최소화하려는 연구가 필요하다. 최근에는 서비스 영역을 확대하기 위한 방법으로 지하 공간 또는 음영 지역에서 LCX(Leakage Coaxial Cable)가 이용되고 있다. 본 논문에서는 지하 무선 CDMA 망의 전파의 세기를 측정하였다. 그리고 측정된 결과를 이용하여 이론적인 Micro BTS의 성능을 분석하였다. 이론적인 BER 해석을 위하여 지하 무선 CDMA 망의 임펄스성 간섭 모델을 제안하고, 측정된 파라미터 값을 이용하여 Micro BTS의 BER 성능을 구하였다. 측정 결과, 지하철이 없을 경우보다 지하철이 운행함에 따라서 임펄스성 간섭이 중대됨을 알 수 있었으며, 단방향 운행보다 양방향 운행에서 임펄스성 간섭이 더욱 증가하였다. 수치 계산을 통하여 임펄스성 간섭의 발생 시간율과 다중 사용자 수에 따라 Micro BTS의 BER 성능이 주로 열화됨을 알 수 있었다. The capacity and quality of CDMA(Code Division Multiple Access) system are affected by multi user interference and impulsive interference in the underground wireless network. Therefore, it is essential to minimize the interference in CDMA system. Recently, LCX (Leaxial Cable) is used to expand service area in the underground area or shadow region. In this paper, the propagation of underground wireless CDMA network is measured. And then, using the measured data the theoretical performance of Micro BTS(Base Transmitter Station) is analyzed. For theoretical BER analysis, the impulsive interference model in the underground wireless CDMA network is proposed and the BER performance of Micro BTS is obtained by using the measured data. From the measurement results, it is found that the impulsive interference increases in the presence of passing train than the absence of passing train. Also, it is known that more interference appears in the presence of crossing two way train than in the presence of passing one way directional train. From the numerical results, the BER performance of Micro BTS is to be mainly degraded by the occurrence rate of impulsive interference and the number of multiple users.

오스템퍼 처리한 구상흑연주철의 드릴가공 특성과 공구수명에 관한 연구

조규재,이승수,전언찬,박흥식 동아대학교 공과대학부설 생산기술연구소 1996 生産技術硏究所硏究論文集 Vol.1 No.2

Drilling tests were carried out austempered ductile cast iron(ADI) to clarify the factors influencing the drilling chracteristics of ADI material. The machinability of material was evaluated using high speed steel drill and cobalt contained drill of 6mm diameter. The spherodal graphite cast iron materials were austenized at 900℃ for in hour and then wear was kept at 375℃ for 2 hours. Austempered ductile cast iron contains a great deal of retained austenite which contributes to an improvement of impact strength. In this paper, machinability of ADI was investigated by drilling experimentation. The results obtained are as follows: a) Flank wear increases logarithmically with the increases of cutting time. b) Relation of flank wear and cutting force can be applied to FZ = 925VB + 820 for the cutting suggested condition. c) Drilling hole number of about 2 times can be reduced more step feed than ordinary feed due to the high hardness of ADI material and hardness increasing ascribed to the martensite of retained austenite.

연접 부호화 기법에 의한 무선 ATM의 성능 개선

조성언,박기식,홍희식 順天大學校 1999 論文集 Vol.18 No.1

In this paper, we have analyzed and simulated the BER and CLP of Wireless ATM(WATM) cells adopting the concatenated FEC technique in Rician fading channel. Also, in Rician fading channel, we have contrived the performance improvement by introducing the fading compensation technique of inserting pilot symbols into the concatenated FEC. From the results, in Rician fading channel, it is known that since the superior BER performance in low ?? results in the divergence when the Viterbi decoder is conducted first, the performance difference of about 2 [dB] occurs between the theory analysis and the simulation. Besides, from the only simulation results, it is known that the system performance adopting the concatenated FEC technique by inserting pilot symbols is improved about 1 [dB] better in terms of ?? than the system performance adopting the only concatenated FEC technique.

Drill가공에 있어서 ADI재료의 절삭성에 관한 연구

조상순,조규재,전언찬,장성규 東亞大學校 大學院 1995 大學院論文集 Vol.20 No.-

The drilling tests were performed on austempered ductile cast irons(ADI) with 2∼3% silicon to clarify the factors influencing the driling characteristics of ADI material. The machinability of each material was evaluated using high speed steel drills of 4mm diameter. The ductile cast iron materials were austenized at 900℃ for 1 hour and then held at 375℃ for 2 hours. Austempered ductile cast iron containsa great deal of retained austenite which contributes to an improvement of impact strength. The machinability of ADI depends on Si components and machinability of workpice has been proved better 3% Si material with high Si components than 2% and 2.5% Si material. It was found that the tool life was a great affected by the feed rate and as feed rate increses, tool life gradually decreased.

3-상태 전파 채널에서 DS/CDMA-BPSK 신호의 성능 해석

조성언,조경룡 順天大學校 1999 論文集 Vol.18 No.1

To model and analyze the realistic terrestrial mobile satellite channel, this paper suggests the 3-state propagation model in which the channel occupation probability of Rayleigh fading, Rician fading, and Shadow Rician fading is varied. Also to verify its reliability, the BER performance of DS/CDMA-BPSK signal altered by the suggested 3-state channel model is shown using as parameters channel occupation probability ??, processing gain (PG), the number of simultaneous users, and Rician fading depth ??. From the results, the BER performance is much more affected with the Heavy Shadow Rician fading than the Light and the Average Shadow Rician fading, which accordingly shows that coding or diversity technique must be used to improve the system performance in the Heavy Shadow Rician channel. Also in the case of BER performance with respect to the variation of channel occupation probability, when the probability of Rayleigh fading is fixed, the increment of the probability of Rician fading and the decrement of the probability of Light Shadow Rician fading shows the improvement of BER performance. Especially it is known that, with the variation of channel occupation probability, Rayleigh fading and Light Shadow Rician fading affects the radio channel much more than others. With the analysis of the BER performance of DS/CDMA-BPSK signal according to the PG and the number of users, BER is not affected significantly by the PG when the number of users are small. However, when the number of users are large, BER is seriously affected by PG. So, to design the system more efficiently, it is needed to make PG as small as possible in the case of small user.

주파수 선택성 레일리 페이딩 감쇄 통신로에서 OFDM 시스템의 성능 해석

조성언 순천대학교 1999 순천대학교 자연과학논문집 Vol.18 No.2

This paper analyzed the BER performance of OFDM/DPSK system versus the partial band interference ratio(α), the normalized channel delay time(τ/T_s) the bit energy to noise spectral density ratio(E_b/N_0), and the desired signal power to delayed undesired signal power ratio(D/U) in the DAB broadcasting or indoor wireless LAN channel with which the frequency selective Rayleigh fading exists, and also analyzed the performance improvement obtained by adopting the convolutional coding technique. From the results, the voice service requirement (BER=10^(-3)) was not achieved in the partial band interference of 20[%] without coding technique. In DIR of 15㏈ and partial hand interference of 20[%], the E_b/N_0 of at least 22㏈ was needed to meet the data service requirement by adopting the convolutional coding technique. In the E_b/N_0 of 20㏈, the data serve requirement (BER=10^(-5)) was accomplished in the partial band interference of 5[%], and in the E_b/N_0 of 30㏈ and 40㏈, the data service requirement (BER=10^(-5)) was accomplished in the partial band interference of even 35[%]. In the BER performance versus DUR, with the presence of the partial band interference, even the voice service requirement was not met in the (E_b/N_0) of 20㏈ and 30㏈, which means the technique of performance improvement has to be used. So when the convolutional coding was adopted as a performance improvement technique, in the E_b/N_0 of 30㏈, the data service requirement was achieved in DUR of 7㏈, moreover in partial band interference of 50[%], the voice service requirement was achieved in the E_b/N_0 of 20㏈ by adopting the convolutional coding.

Rician 페이딩 채널에서 WATM 셀의 성능 개선에 관한 연구

조성언,박정현,백승선 順天大學校 1998 論文集 Vol.17 No.1

This study has analyzed theoretically the effect of fading to design effective wireless ATM system. The CNR, CLR, and CER of wireless ATM system adopting FEC coding and diversity reception techniques have been derived in fading environment. From the results, CLR in the HFEC which puts more importance on coding gain than coding rate, it show(62, 32, 5)FEC coding having higher coding gain is more adequate. And also, it has to consider CER and MaxU data together in the PFEC performance, because emphasizing the error correction ability to lessen CER cause inefficient use of channel by the added redundancy bit. (438, 384, 6) FEC coding is more appropriate in the CER and MaxU. it is showing the CER and MaxU value when dividing (438, 384, 6) FEC. The more division is the less CER value in the CER, but in the MaxU, when a wires ATM cell is divide by more then two WATM cell, it leads to increase of overhead due to more header transmission, and finally to relatively poor MaxU value in the case of going over the certain bound of CNR value. (240, 192, 6) FEC code is proper than (438, 386, 6) code when considering CER and MaxU data in the payload division. Using diversity technique to wireless ATM cell header improves MRC to about 1.7 dB of Eb/No than SC under the Rayleigh fading environment, and to 2 dB of Eb/No under Rician fading (K=5). Also using the diversity technique to wireless ATM cell Payload under Rician fading environment improves MRC to 3dB of Eb/No than SC in both case of K=5 and K=10.

이동위성통신시스템에서 GMSK 신호와 MSK 신호의 오율성능 해석

조성언,조성준 한국항공대학교 1994 論文集 Vol.32 No.-

본 논문에서는 이동위성시스템에서 발생하는 라이스 (Rician) 페이딩과 돌일채널간섭의 영향을 GMSK와 MSK 신호를 대상으로 하여 반송파 대 잡음 전력비 (CNR), 반송파 대 간섭파 전력비 (CIR), 직접파 대 반사파 전력비 (K) 등을 함수로 하여 수치계산한 결과를 그래프로 나타내어 신호의 특성을 알아보았다. 얻어진 결과로부터 직접파 대 반사파 전력비 (K)가 ∞인 잡음만의 환경과 K가 10인 라이스 (Rician) 페이딩 화경하에서 오율 10?을 기준으로 할 때 GMSK 신호만을 비교한 경우에 반송파 대 잡음 전력비 (CNR)의 차이는 약 2.1dB이며, 같은 환경하에서 MSK 신호만을 비교한 경우에 반송파 대 잡음 전력비 (CNR)의 차이는 2.4dB임을 알 수 있었다. 직접파 대 반사파 전력비 (K)가 10인 라이스 (Rician) 페이딩 환경하에서 오율 10?을 기준으로 비교 할 때 MSK 신호가 GMSK 신호보다 약 1.2dB 개선됨을 알 수 있었다. 또한 직접파 대반사파 전력비 (K)가 6인 라이스 페이딩의 환경하에서 반송파 대 잡음 전력비 (CNR)가 15dB이고 반송파 대 간섭파 전력비 (CIR)가 15dB일때 MSK 신호는 GMSK 신호의 오율보다 약 1.0×10? 정도 오율성능의 개선이 있음을 알 수 있었다. 직접파 대 반사파 전력비 (K)가 10이고, 반송파 대 간섭파 전력비 (CIR)가 25dB 일때 오율 10?을 기준으로 한 경우에 MSK 신호가 GMSK 신호보다 약 1.1dB정도 우수함을 알 수 있었다. 따라서 반송파 대 간섭파 전력비 (CIR)를 증가시킴에 따라 신호의 오율은 개선되며 반송파 대 간섭파 전력비 (CIR)의 값이 커짐에 따라 점차 간섭성분의 영향은 작아져서 페이딩만이 영향을 주는 통신로 환경으로 변화됨을 알 수 있었다. 또한 K값이 클수록 즉, 직접파 성분이 반사파 성분에 비해 지배적일 때 오율 성능이 개선됨을 알 수 있었다. In this paper, the effect of fading and cochannel interference on GMSK and MSK signals in mobile satellite communications has been investigated. For this objective the error rate equation of GMSK and MSK signals has been derived in the environment of interference and Rician fading which includes Rayleigh fading as special cae. And then using the derived equation, error rate performance of GMSK and MSK signals has been evaluated and represented in figures as a function of carrier-to-noise ratio (CNR), carrier-to-interference (CIR), and direct-to-indirect singal ratio (K). As the results, it is known that the differenceof CNR between two cases of Caussian noise only (K=∞) and Rician fading (K=10) at the eror rate of 10? is about 2.1dB in GMSK signal and is about 2.4dB in MSK signal, respectively. In the Rician fading environment, ehen the direct-to-indirect signal ratio (K) is 10 and error rate is 10?, MSK signal is superior to GMSK signal by about 1.2dB in terms of CNR. When direct-to-indirect signal ratio K=6, CNR=15dB and CIR=15dB, the MSK signal is superior to GMSK signal by about 1.2×10? in terms of error rate. When the direct-to-indirect signal ratio (K) is 10 and carrier-to-interference ratio (CIR) is 25dB at the error rate of 10?, the MSK signal is superior to GMSK signal by about 1.1dB in terms of CNR.

페이딩과 간섭 환경에서 최적부호화된 QPSK시스템의 성능해석

조경룡,조성언 순천대학교 공업기술연구소 1997 工業技術硏究所論文集 Vol.11 No.-

In a previous paper, most performance evaluations of TCM are done via simulations in the fading channel. However, in this paper we theorically derived the error rate equations and evaluated the performance of TCM-QPSK signal in Rician fading and cochannel interference channel environment(CCI). These combined channel modelling for the TCM application had not been treated previously in the literature. When Rician fading and CCI are present together, analysis becomes much more difficult than that fading is only exist. But we have derived a computationally efficient solution for this case.

보육교사의 현직교육 및 보육시설 내 장학에 대한 현황과 보육시설장의 인식

조성현,강재희 이화여자대학교 교과교육연구소 2007 교과교육학연구 Vol.11 No.2

본 연구에서는 보육교사의 현직교육 및 보육시설 내 장학에 대한 현황과 시설장의 인식을 알아봄으로써 보육현장의 현황 및 요구에 적합한 보육시설 내 장학 프로그램을 계획하는데 기초자료를 제공하고자하였다. 연구의 목적을 위하여 보육시설의 시설장 115명을 대상으로 설문지 조사를 실시하였다. 연구결과 보육시설의 현직교육은 매우 제한적으로 나타났으며 교육을 받을 시간이 부족한 것으로 나타났다. 보육시설 내 장학을 실시하는 시설은 절반 정도로 나타났으며 주로 장학의 방법에 대한 지식부족 때문에 실시하지 않는 것으로 나타났다. 주로 실시하고 있는 장학의 방법은 외부교육에 참여한 교사의 전달교육이었으며 장학을 실시할 때는 시설장과 교사가 협의하는 것으로 나타났다. 장학의 활성화를 위해서는 수업 및 잡무의 부담을 줄이고 새로운 정보와 지식을 습득할 수 있는 내용이 필요함을 지적하였다. 이러한 연구결과를 바탕으로 보육시설 내 장학의 활성화를 위한 제안을 하였다.