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Sum Capacity and Optimum Codes of CDMA Systems under Different Conditions

Pad, Pedram | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42118 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Marvasti, Farokh
  7. Abstract:
  8. CDMA is one of the main multiple access techniques. In this thesis, we study the channel capacity and the optimum codes for CDMA systems under different conditions. The optimality has different meaning for each studied scenario. The discussed scenarios differ from the aspects of the alphabet of the system, the ability of getting active or inactive for users, and the random fluctuation of the user powers. The first scenario is the systems with real input alphabet. In this case, by optimum codes, we mean a code that maximizes the sum channel capacity of the system. The second scenario is the systems with binary input alphabets and binary signatures. In this section, optimum codes are the codes that guarantee errorless communication in ideal channel. The other case is a binary system in which the users can get active or inactive and the optimum codes are again the errorless codes for ideal channel. In all of these three cases, we suppose that we have a perfect power control in the system and thus the received powers equal to the predefined values. The last discussed scenario is a binary system in which the power control is not perfect and hence the Near-Far effect appears. Also, in this system the optimality of the codes means the capability of errorless communications in noiseless channel.

  9. Keywords:
  10. Code Devision Multiple Access (CDMA) ; Multiple Access ; Sum Channel Capacity ; Optimum Codes

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