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Energy/Throughput Efficient Signalings for Optical CDMA Systems

Ghaffari, Babak | 2010

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 40321 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Salehi, Javad
  7. Abstract:
  8. A major breakthorugh in all-optical wireless and wired communication networks is taking place in the last mile such as access networks. In this case، study-ing various multiple-access techniques in all-optical domain، especially optical code-division multiple-access (OCDMA) technique is of utmost importance. In this thesis we study several key signalings and modulation techniques in the con-text of their performance، energy and throughput efficiency for OCDMA systems. In particular we introduce novel multilevel signaling techniques for OOC-based fiber-optic CDMA systems and present their corresponding all-optical receiver structures using advanced optical devices such as optical-logic-gate elements and optical analog-to-digital converters. In the proposed system، users of the netwrok are categorized into several classes. Users of the same class transmit at the same power level but different from the other classes’ users. By employing power control، the system performance is improved as compared to an ordinary one-level system by means of increasing the throughput as well as decreasing the multiple-access interference (MAI). In OCDMA systems، MAI limits the capacity of network even at high signal-to-noise ratios. The proposed multilevel signal-ing increases the system’s capacity beyond the limits of one-level systems by a factor that is proportional to the number of levels of optical signals used in such networks. Optical wireless local area netwroks (LAN) have recieved special attention where security is of concern، and where obtaining radio frequency band would not be economical. Furthermore optical wireless LANs are of immense interest in places where electromagnetic interference is of utmost concern. In the final sec-tions of this thesis we analyze a typical wireless OCDMA LAN and study its sub-systems from a digital design and implementation point of view. We introduce a novel analytical approach in order to obtain the performance and throughput ef-ficiency of such systems. Furthermore we study an iterative multi-user detection scheme and study its functionality in OOC-based wireless OCDMA networks
  9. Keywords:
  10. Optical Communication ; Optical Code Division Multiple Access (OCDMA) ; Optical Orthogonal Code (OOC) ; Analog to Digital Converter ; Multilevel Optical Signal ; Multiclass Optical Signal ; Optical Logic Gates

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