• Title/Summary/Keyword: Optical CDMA

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Single-Fiber Bidirectional Transmission System Using Base Station Without Light Sources (광원이 없는 Base Station을 이용한 단일 광섬유 양방향 전송 시스템)

  • 전금수;정용채;임명섭;반재경
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.28 no.5A
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    • pp.323-332
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    • 2003
  • We have proposed and implemented a novel cost-effective optical subcarrier mutiplexing transceiver for base station without light sources in which optical signal can be transmitted bidirectionally over a single optical fiber. Modulated optical signal is retransmitted from the base station to the central office using a ring-type base station which consists of a circulator and an Mach-Zehnder modulator, where the optical source is supplied from the central office. In order to investigate the feasibility of the proposed base station without light sources, we have measured adjacent channel power ratio and carrier to noise ratio by transmitting the IS-95 CDMA signal and 14 tones carrier signal bidirectionally through the system.

A novel OCDMA based on special chirped fiber Bragg gratings (OCDMA용 광섬유 첩 격자를 이용한 새로운 광 코드 분할 다중화 방식의 구현)

  • 구현덕;김상인;이상배;최상삼;송석호;김필수
    • Proceedings of the Optical Society of Korea Conference
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    • 2001.02a
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    • pp.172-173
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    • 2001
  • 다중 광접속 방법 중 CDMA는 많은 수의 주소(개별 사용자를 위한 채널)를 제공하고 광 패킷 전송 방법에 있어서는 패킷들의 충돌을 피하기 위한 복잡한 장치를 필요로 하지 않는다는 장점을 가지고 있다. LED와 같은 Incoherent 광원을 이용하는 광 CDMA를 위한 여러 가지 광 코드와 암호화 방식이 제안되어 왔으며, 파장/시간 이차원 광 코드를 이용하는 방식은 AWG mux/demux 또는 AWG 라우터를 이용하여 광 코드가 용이하게 구현될 수 있음이 보고된 바 있다. (중략)

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Performance Evaluations on Shared-Type Encoder/Decoder with Wavelength/Time 2-D Codes for Optical CDMA Networks (파장/시간의 2차원 코드를 사용한 광 부호 분할 다중 접속 부호기/복호기의 성능 분석)

  • Hwang, Hu-Mor;Chang, Chul-Ho;Song, Jin-Ho
    • Proceedings of the KIEE Conference
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    • 2006.07d
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    • pp.2013-2014
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    • 2006
  • For large capacity optical CDMA networks, we propose a shared-type encoder/decoder based on an tunable wavelength conveter (TWC) and an arrayed waveguide grating (AWG) router. Feasibility of the structure of the proposed encoder/decoder for dynamic code allocation is tested through simulations using three types of wavelength/time 2-D codes, which are the generalized multi-wavelength prime code(GMWPC), the generalized multi-wavelength Reed-Solomon code(GMWRSC) and the matrix code. Test results show that the proposed encoder/decoder can increase the channel efficiency not only by increasing the number of simultaneous users without any multiple-access interference but by using a relatively short length CDMA codes.

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Enhancement of ACPR and Noise level of Analog Optical Transmitter by Feedforward Compensation (피드포워드 보상회로를 적용한 아날로그 광 송신기의 ACPR과 잡음 레벨 개선)

  • Lee, Joon-Jae;Park, Sang-Hyun;Yun, Young-Seol;Choi, Young-Wan
    • 한국정보통신설비학회:학술대회논문집
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    • 2005.08a
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    • pp.149-153
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    • 2005
  • The optical fiber micro-cellular system requires the high linearity that determines the quality and capacity of system. Hence, there is a need for improving the linearity in mobile communication system. In order to compensate dispersion-induced signal distortion, we fabricated the optical feedforward transmitter. The compared 3rd-IMD was enhanced by 38 dB for two-tone case and the Adjacent Channel Power Ratio was enhanced by 20 dB for W-CDMA 1 carrier and by 16 dB for W-CDMA 3 carriers. Also, the induced noise level was reduced.

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Wavelength-Time Codes using Modified Time Mapped Prime Sequences for Optical CDMA (변형된 Time Mapped Prime Sequence를 이용한 Wavelength-Time Code for Optical CDMA)

  • Jhee, Yoon-Kyoo
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.47 no.10
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    • pp.29-33
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    • 2010
  • In this paper, a new family of wavelength-time codewords using modified time mapped prime sequences as a time spreading pattern is constructed. When $P_t$ = 3, we can construct $P_w^2$ wavelength-time codewords with low autocorrelation sidelobe and crosscorrelation of less than or equal to 1. When $P_t$ = 5 and $P_t$ = 7, the number of wavelength-time codewords of $P_w^2$ can be constructed with good crosscorrelation of 1 and autocorrelation of less than or equal to 2.

Compensation of Laser Diode Nonlinearity in the Optical SCM System for CDMA RF Signal Transmission (CDMA RF 신호 전송용 광 SCM 트래시버에서 레이저 다이오드의 비선형 왜곡 보상)

  • 최영우;유진태;이길성;박진우
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.25 no.12A
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    • pp.1766-1773
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    • 2000
  • 이동통신망에서 RF 신호를 송수신하는 기지국(base station)과 이동 통신 신호의 교환 전송을 담당하는 중앙국(central station)을 광섬유로 연결하여 구성하는 SCM (Subcarrier Multiplexing) 전송 시스템은 미래의 음성, 영상, 데이터 서비스 등의 이동통신 시스템에 적용할 수 있기 때문에 최근 관심사가 커지고 있다. 이동통신망을 위한 SCM 광전송 시스템의 유용성에도 불구하고, CDMA RF 신호를 전송하는 과정에서 많은 물리적인 제약이 있다. 특히, 많은 가입자의 CDMA RF 신호가 하나의 레이저 다이오드(LD: Laser Diode)를 구동시킬 때, RF 신호의 합이 레이저 다이오드의 선형영역을 벗어나면 클리핑(clipping)이나 비선형 왜곡이 발생하여 시스템의 성능을 저하시키게 된다. 본 논문에서는 CDMA RF 신호의 SCM 광전송 성능분석을 통해 레이저 다이오드에 의해 발생하는 비선형 왜곡의 영향을 분석하고, 분석 결과로부터 레이저 다이오드에 의한 비선형 효과를 최소화 할 수 있는 비선형 왜곡 보상구조를 제안하였다. 또한 제안된 레이저 다이오드 비선형 보상기의 성능을 시뮬레이션과 실험을 통해 얻어진 BER로부터 측정하였다.

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Detection of Fault ONUs in TDM-PON Using CDMA Modulation Scheme (CDMA 변조방식을 이용한 TDM-PON의 고장 ONU 검출)

  • Choi, Byung-Chul;Park, Jae-Uk;Chung, Jun-Hoi;Park, Young-Il
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.1A
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    • pp.1-6
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    • 2008
  • TDM-PON has a disadvantage that entire PON system gets into trouble when only one ONU is out of order and sends optical signal constantly. This paper suggests a scheme to find the fault location. TDMA is impossible when upstream traffic is interrupted by continuous wave signal from a troubled ONU. Therefore, CDMA coding is introduced in separating fault ONUs, and detection algorithm is verified.

Effect of Line-Width of Optical Sources on Performance of Spectral Amplitude Coding Optical CDMA Systems (광원 라인폭이 Spectral Amplitude Coding Optical CDMA시스템의 성능에 미치는 영향)

  • Jhee, Yoon Kyoo
    • Journal of the Institute of Electronics and Information Engineers
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    • v.52 no.2
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    • pp.119-124
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    • 2015
  • In this paper, we analyze the effect of line-width of optical sources on the performance of spectral amplitude coding (SAC) optical code division multiple-access (OCDMA) systems. For a performance analysis we use a symmetric balanced incomplete block design (BIBD) code as the code sequence because we can construct a series of code families by choosing different values of q and m. The ideal BIBD code (m=2) requires narrower line-width than the nonideal BIBD codes when the effective power is large ($P_{sr}=-10dBm$). But the nonideal BIBD codes (m>2) need narrower line-width than the ideal BIBD code when $P_{sr}=-25dBm$.

Delay-Throughput Analysis Based on Cross-Layer Concept for Optical CDMA Systems (Cross-layer 개념을 바탕으로 한 광 CDMA 시스템을 위한 Delay-Throughput 분석)

  • Kim, Yoon-Hyun;Kim, Seung-Jong;O, Yeong-Cheol;Lee, Seong-Chun;Kim, Jin-Young
    • 한국정보통신설비학회:학술대회논문집
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    • 2009.08a
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    • pp.314-319
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    • 2009
  • In this paper, the network performance of a turbo coded optical code division multiple access (COMA) system with cross-layer, which is between physical and network layers, concept is analyzed and simulated We consider physical and MAC layers in a cross-layer concept. An intensity-modulated/direct-detection (IM/DD) optical system employing pulse position modulation (PPM) is considered In order to increase the system performance, turbo codes composed of parallel concatenated convolutional codes (PCCCs) is utilized. The network performance is evaluated in terms of bit error probability (BEP). From the simulation results, it is demonstrated that turbo coding offers considerable coding gain with reasonable encoding and decoding complexity. Also, it is confirmed that the performance of such an optical COMA network can be substantially improved by increasing the interleaver length and the number of iterations in the decoding process. The results of this paper can be applied to implement the indoor optical wireless LANs.

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