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Near-Far Effects in CDMA Systems

Shafinia, Mohammad Hossein | 2014

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 46232 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Marvasti, Farokh
  7. Abstract:
  8. On one hand Code Devision Multiple Access (CDMA) as an efficient spread spectrum multiple access solution was under consideration in recent years. On the other hand one of the main challenges in cellular networks was near-far effect and fading effect which cause different received powers from different users.
    In this thesis we are going to investigate near-far effects in overloaded CDMA systems from different aspects. Firstly we will investigate on the robust systems over near-far effect, propose near-far resistance codes and a very low complexity ML decoder for a subclass of these codes. Secondly we deal evaluation of the sum capacity of finite dimensional CDMA systems. These systems supposed to have binary of finite nonbinary inputs and signature matrices. The main conclusion of this chapter is that with the information of received powers, near-far effects can increase the sum capacity.
    Finally, bounds are proposed for asymptotic average capacity of a CDMA system in the presence of near-far effect when the channel state information is unavailable. The average is taken over all possible signature matrices. The evaluation of the bounds are based on the assumption that the input alphabet is finite but the signature matrix elements can be finite, infinite, real or complex
  9. Keywords:
  10. Code Devision Multiple Access (CDMA) ; Optimum Codes ; Near-Far ; Sum Capacity

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