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Multiuser Detection in Spread Time CDMA Systems via Circular Multiple Access Codes

Baghali Khanian, Zahra | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 43937 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Mashhadi, Saeed; Khalaj, Babak
  7. Abstract:
  8. Multiuser detection provides the first comprehensive of the subject of multiuser digital communication, dealing with demodulation of mutually interfering digital information streams. Multiple access spread time codes which are more resistant to various channel impairments, is a motivation to design a multiple access system using spread time systems via circulant codes, to detect users bit stream without multiuser interference. So first of all we introduce multiple access systems and spread time codes. To have an overview of desired system we present a matrix representation of OFDM system. With allocating multiuser circulant coded to users in spread time system, in AWGN channel , users’ bit stream can be detected via only a DFT block in receiver without multiuser interference, this code play a role like CP in OFDM system. We will show that if there is any silent users, their code can be used to improve others’ performance. We generalize the system design in flat fading and frequency selective fading channels, in this channel our system can detect users’ bit stream without multiuser interference. In all above channels users’ performance is measured by their error probability and designed system is compared to CDMA and OFDMA
  9. Keywords:
  10. Multiuser Detection ; Optical Orthogonal Frequency Division Multiplexing (OFDM) ; Spread Time-Code Division Multiple Access (ST-CDMA) ; Circular Multiple Access Codes

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