Adaptive Equalization for DS-CDMA Systems

  • Mohamed Ebrahim Jadah

Student thesis: Master's Thesis

Abstract

Mohamed Ebrahim Jadah. Adaptive Equalization for DS-CDJl1A Systems. M.Sc. by Research Thesis, Communication Engineering Department, Etisalat University College, Sharjah, United Arab Emirates, December 2005 The research investigates and compares the performance of using various non-quadratic adaptive algorithms in the adaptation of linear and non-linear receivers, for the detection of asynchronous Direct Sequence-Code Division Multiple Access (DS-CDMA) communication system over various channels (Gaussian, Impulsive, Rayleigh Multi-paths Gaussian and Rayleigh Multi-paths Impulsive channels). These algorithms are the lower order, Lp, (where the power of the cost function is lower than 2), the least-mean mixed norm, LMMN, (where a mixed-norm function is introduced, which combines the Least Mean Square (LMS) and the Least Mean Fourth (LMF) functions), and the least mean square-fourth switching, LMSF, (where this algorithm switches between LMS and LMF depending on the value of the error). The linear receiver includes the feed-forward filter (FFF) only, while the non-linear receiver comprises feed-forward filter (FFF), feedback filter (FBF), and an equalizer/second order digital phase locked loop (DPLL). The investigations study the effect of using the proposed algorithms on the performance of the linear and non-linear receivers in terms of mean-square error (MSE) and bit-error-rate (BER). Extensive computer simulation tests have been carried out to determine the optimum values of the step-size, the power of the cost function, and the adaptation parameter of the proposed algorithms. The performances of the proposed algorithms have been compared with the traditional Normalized Least Mean Squared (NLMS) algorithm. It is demonstrated that the linear and non-linear receivers adapted by the LMMN algorithm will have the fastest convergence rate and similar BER performance, in comparison with the NLMS algorithm. Finally, it is concluded that the non-quadratic adaptive algorithms can be used as an alternative to the NLMS algorithm in the adaptation process of the linear and non-linear receivers for the detection of DS-CDMA system. Indexing
Date of Award2005
Original languageAmerican English
SupervisorShihab Jimaa (Supervisor)

Keywords

  • Equalization
  • Digital Communications
  • DS-CDMA
  • Non-Quadratic cost functions

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