Improvement of Coherent Ultrashort Light Pulse CDMA Communication Systems with Distinct 4-Level m-Sequences(<Special Section>Wide Band Systems)

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概要

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• Optical fiber communications require multiple-access schemes to access a shared channel among multiple users. The coherent ultrashort light pulse code-division multiple-access (CDMA) system is one such scheme, and it also offers asynchronous-access communication. This system usually employs 2-level, i.e., binary, m-sequences as signature codes because of their low correlation. If the number of active users is greater than the length of the m-sequence, i.e., code length, distinct m-sequences are used. However, the distinct 2-level m-sequences do not exhibit low correlation, resulting in performance degradation. We therefore propose a coherent ultrashort light pulse CDMA communication system with distinct 4-level, i.e., quaternary, m-sequences to improve system performance when the number of users is greater than the code length. We created the 4-level m-sequences from 2-level m-sequences, and assess the correlation of the 4-level m-sequences. We also theoretically derive the bit error rate (BER) of the proposed system taking into account multiple-access interference (MAI), beat noise, amplified spontaneous emission (ASE), shot noise, and thermal noise. The numerical results show that BER for distinct 4-level m-sequences is more than an order of magnitude smaller than that for distinct 2-level m-sequences. BER is limited by MAI and beat noise when the power of the received signal is high, otherwise BER is limited by ASE, shot noise, and thermal noise.

• 社団法人電子情報通信学会の論文
• 2006-11-01

著者

• Yashima Hiroyuki

  Department Of Management Science Tokyo University Of Science

• IGARASHI Yasutaka

  Department of Information and Computer Sciences, Saitama University

• Igarashi Yasutaka

  Department Of Electrical Engineering Tokyo University Of Science

• OKAJIMA Ippei

  Pioneer Corporation

• Yashima Hiroyuki

  Department Of Information And Computer Sciences Saitama University

関連論文

• Analysis of Optical PPM/CDMA System with M-Ary Convolutional Coding
• Performance Analysis of MDSS Code Acquisition Using SLS for Optical CDMA Systems(Fiber-Optic Transmission for Communications)
• Performance Analysis of Coherent Ultrashort Light Pulse CDMA Communication Systems with Nonlinear Optical Thresholder(Fiber-Optic Transmission for Communications)
• Dispersion Compensation for Ultrashort Light Pulse CDMA Communication Systems (Regular section)
• Improvement of Coherent Ultrashort Light Pulse CDMA Communication Systems with Distinct 4-Level m-Sequences(Wide Band Systems)
• On the Code Synchronization of PPM/OPPM Fiber-Optic CDMA Systems(Wide Band Systems)

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