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Multiuser Interference Mitigation for Performance Enhancement in OCDMA and OFDMA Systems

Nezamalhosseini, Alireza | 2013

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 45378 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Marvasti, Farokh
  7. Abstract:
  8. Due to the extremely fast growth in high speed data rate demand in the recent years, it is necessary to make use of the optical technologies in telecommunication access networks. Passive optical networks (PONs) has got much attention compared to other optical access architectures due to some advantages such as low installation and maintenance expenses, and providing more reliable network transmission.
    In this thesis, we will study two multiple access techniques, namely optical code division multiple access (OCDMA) and optical orthogonal frequency division multiple access (OOFDMA). Since the system performance of these techniques are mainly limited by multiple access interference, we have paid a particular attention in proposing a novel methods which suppresses or reduces the multiple access interference and also enhances the network performance.
    In this thesis, firstly a novel multiuser detection method based on an iterative technique in OCDMA systems is proposed. The maximum achievable data rate in optical networks is limited by the poor electro-optical efficiency. In order to solve this issue and achieve higher data rates, an all-optical implementation of the proposed method using optical logic gates is presented.
    Secondly, a new multiuser detection method in OOC-based OCDMA systems by exploiting AND logic gates is introduced. Then, we will propose an overloaded synchronous OCDMA system based on UWC codes. Using UWC properties we propose a simple receiver that completely removes the multiple access interference. Moreover, we propose an iterative multiuser receiver that outperforms the performance of the first receiver at the expense of more computational complexity.
    Finally, we introduce and experimentally demonstrate a novel receiver structure for direct detection OOFDMA systems in order to mitigate the interference signal effectively. In addition to its simple structure, the bandwidth efficiency is improved by using the proposed structure.
  9. Keywords:
  10. Multiuser Interference ; Optical Code Division Multiple Access (OCDMA) ; Optical Orthogonal Frequency Division Multiplexing (OFDM) ; Passive Optical Access Networks

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