• Title/Summary/Keyword: DS-SS

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Acquisition of PN sequence by neural netowrks in direct-sequence spread-spectrum systems (신경망을 이용한 DS/SS 시스템의 PN 코드의 초기 동기)

  • 이상목;유철우;강창언;홍대식
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.33A no.7
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    • pp.44-54
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    • 1996
  • In DS/SS systems it is necessary to synchronize the locally generated despreading signal with the received spreading signal to demodulate the received signal. The synch process between the two signals is usually accomplished in two steps : first acquisition then tracking. In this paper, an acquisition system aided by the neural network is proposed for the rapid and exact acquisition in DS/SS. the neural netowrk is composed o fthree-layered perpecptrons and trained by the backpropagation algorithm. The performance of the proposed system is analyzed and compared with ones of conventional systems using the sequential estimation technique under an additive while gaussian noisy channel. In all of th econsidered simulations, the proposed system outperforms conventional systems.

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A fast code acquisition using integrated search and verification (ISV) scheme in the DS-SS system (DS-SS시스템에서 탐색과정과 확인과정을 통합하는 (ISV) 고속부호 포착 시스템)

  • 오성근;임종혁;성상헌;최태영
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.33A no.5
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    • pp.24-30
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    • 1996
  • In this paper, we propose a fast code acquisition method that can reduce drastically the mean acquisition time of the direct sequence spread spectrum (DS-SS) system by using and integrated search and verification (ISV) scheme. The proposed method performs simultaneously the search and verification processes at every search cell, through storing sufficiently long signal samples enough to perform the verification process form the previously received samples. We analyze and acquisition performance in the case of Gaussian channel to evaluate theacquisition perfomrance of the proposed method. From the simple numericl analysis result, we have shown that the acquisition performance of the proposed method is better than that of the conventional serial search method, and the performance improvement becomes more prominent as the channel environment becomes degraded.

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A study on the development of high-speed wireless modem using DS/SS DQPSK modulation (직접확산 DQPSK 변조방식을 이용한 고속 무선모뎀의 개발에 관한 연구)

  • 오정훈;김진욱;김기두;장수영
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.33A no.11
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    • pp.19-31
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    • 1996
  • Spread spectrum method gurantees good performance in digital communication system under multi-path interference and jamming signals. The purpose of this paper is to develop the wireless modem using DS/SS techinque. The transceiver consists of a spread spectrum DQPSK transmitter and a mtching receiver. The system operates with the chipping rate set to 4 Mcps and the number of chips/symbol at 64, making the data rate 62.5 Kbps using QPSK modilation. The receiver section uses a digital matched filter for fast acquisition of burst signals and uses the comparing the BER of proposed system iwth that of narrow bnd system under various additive white gaussian noises. It is showen that the proposed sysem has better performance than narrow band system. When jamming signals is added to the suggested DS/SS system, we also show that the experimental performance (BER) of the suggested wireless modem is almost same as theroretical performance.

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Infectious RNA Viruses in the Edible Mushroom Pleurotus spp.

  • Park, Jeonga-Soo;Kim, Young-Ho
    • Journal of Microbiology
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    • v.34 no.1
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    • pp.61-67
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    • 1996
  • Double-stranded RNA (dsRNA) viruses and single-stranded RNA(ssRNA) viruses were detected in a strain of Pleurotus mushroom cultivated in a farm. Those fungal virsus were purified in the pH 6.0 or pH 7.2 using CsCI or Cs$_{2}$SO$_{4}$ buoyant density centrifugation. Each viral particles were not completely separated at any trials. However, mushroom bacili-form virus contains a single major nucleic acid with 0.7 Kb ssRNA, which might code for 20 Kd viral capsid protein. The dsRNAs are encapsidatred into spherical-form viruses, whereas ssRNA viral genomes are encapsidated into two different sizes of bacili-form particles. A healthy-looking mushroom also contained some spherical-form viruses with dsRNAs. Laboratory strains of Pleurotus ostreatus and a cultivated strain of P. sajor-caju did not show any viral particles. Mushrooms with specific disease symptoms. however, contained at least four different sizes of spherical-form viruses. Thus, we concluded that a bacilli-form virus case a severe disease symptoms of adnormal on mushroom development.

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NBI Rejection Techniques using Improved Decision Feedback for DS/SS Systems (DS/SS 시스템을 위한 개선된 결정궤환 구조를 가지는 협대역 간섭신호 제거)

  • 유창현;시광규
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.21 no.10
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    • pp.2679-2686
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    • 1996
  • In this paper, we propsoed the two methods to improve the conventional decision feedback interference canceller in DS/SS communication systems. The data bit is obtained by correlating the PN sequence with the received signals to the present time k, and thus the errors in the reference signal can be reduced by newly deciding all the reference signals with the resultant data bit. Additionally the cancelled signals are computed with less weight for initial reference signals of low processing gain, and highly weighted as the processing gain goes up. the resulting interference canceller outperforms the existing ones. By simulation, we found the proposed algorithm has "2-3 dB" performance gain at BER 10$^{-3}$ compared to the conventional descision feedback algorithm.algorithm.

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A Study on Power Line Communication System using FEC Methods (콘벌루션 코딩 및 DS-SS 방식을 이용한 전력선 통신 시스템에 관한 연구)

  • Kim, Gi-Jung;Park, Chong-Yeun
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.48 no.4
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    • pp.467-473
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    • 1999
  • We have realized the two kinds of power line communication systems by the FSK MODEM. The first approach is the DS-SS (Direct suquence-spread spectrum) technique using 8 bits pseudo noise, the other is Convolutional coding method by the new algorithm. Their characteristics are comparied with each other by experimenting their Bit Error Rates (BER) in high level of Noise. The results have showed that two systems are useful to the application of HA (Home Automation) systems.

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Interference Signal Control using Neural Network in Digital Mobile Communication (이동 무선 통신에서 신경망을 이용한 간섭 신호 제어)

  • 나상동;배철수
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.2 no.1
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    • pp.109-116
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    • 1998
  • In this paper, a back propagation neural network teaming algorithm based on the complex multilyer perceptron is represented for suppressing narrowband interference of the received signals in DS-SS mobile communication system. We proposed neural network adaptive correlator(NNAC) which has fast convergence rate and good performance with combining back propagation neural network and the receiver of DS-SS. We analyzed and proved that NNAC has lower bit error probability than that of traditional RAKE receiver through results of computer simulation in the presence of the tone and narrow-band interference and the co-channel interference.

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Sustainable Urban Development and Residential Space Demand in the Untact Era: The Case of South Korea

  • KIM, Sun Ju
    • The Journal of Asian Finance, Economics and Business
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    • v.8 no.3
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    • pp.675-682
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    • 2021
  • The study analyzes the demand for residential space in the Untact Era. Residential space comprises six categories: the most necessary dedicated space (DS), most preferred south-facing space (SFS), largest space (LS), most necessary shared space (SS), most necessary infra-space (IS), and others. Results indicated the following: 1) All respondents had the highest preference for relaxing spaces except DS. 2) Differences were found between DS, SFS, and LS by age and SS; IS by residential area; and DS, SS, and IS by household size. 3) People aged 60+ preferred a living room while people aged 40-59 preferred a larger kitchen. Seoul citizens preferred gardens or parks in the complex or neighboring forests whereas local citizens preferred shared offices and medical centers. Households of three or more persons preferred a park/forest and two-person households preferred a honbap restaurant. The implications for housing policy are as follows. 1) Nature-friendly spaces are needed to alleviate a sense of isolation. 2) Changing demand for residential space should be reflected in housing policies. 3) The government's housing supply policy with the same residential space and structure must be changed to provide various residential spaces according to age, residential area, and household size.

A Tracking Scheme using Correlation Value at Advanced Offset Range in Galileo BOC(1,1) Signal (Galileo BOC(1,1)에서 이른 상관시간 옵셋 영역의 상관 값을 이용한 추적기법)

  • Yoo, Seung-Soo;Kim, Sang-Hun;Yoon, Seok-Ho;Song, Iick-Ho;Kim, Jun-Tae;Kim, Sun-Yong
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.1C
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    • pp.86-93
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    • 2008
  • The Galileo system, a global navigation satellite system(GNSS) developed by E.U., uses the direct sequence/spread spectrum(DS/SS) modulation. A DS/SS-based system performs a fine synchronization between the received and locally generated spreading signals, via attacking process. In the absence of multipath signals, using the symmetric characteristic of the correlation function, the delay lock loop with the early minus late discriminator(EL-DLL) offers the best performance in tracking. However, in the presence of multipath signals, the symmetry of the correlation function could be lost, causing a tracking bias. In this paper, we observe that the correlation values in the advanced offset range remain almost unchanged, due to the multipath signals being received later than a line-of-sight signal. Based on this observation, we propose a novel tracking scheme for a Galileo BOC(1,1) system.

Noncoherent adaptive code acquisition scheme using a differential detection technique in DS/SS systems (DS/SS 시스템에서의 차등 검파 기법을 이용한 비동기식 적응형 코드 위상 검출 방법)

  • 류탁기;권종형;전형구;홍대식;강창언
    • Proceedings of the IEEK Conference
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    • 2000.11a
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    • pp.77-80
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    • 2000
  • Adaptive filter based code acquisition scheme offers a fast acquisition with a low error probability. However, it has been studied only under a coherent environment. In this paper, the noncoherent adaptive code acquisition scheme employing a differential detection technique is proposed. For the proposed scheme, system probabilities and the mean acquisition time are analyzed numerically. Simulation results show that the proposed system outperforms over the conventional matched filter by 2-4 ㏈ under AWGN channel for 16 taps.

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