Equalization of nonlinear time-varying channels using type-2 fuzzy adaptive filters

  • Authors:
  • Qilian Liang;J. M. Mendel

  • Affiliations:
  • Dept. of Electr. Eng. Syst., Univ. of Southern California, Los Angeles, CA;-

  • Venue:
  • IEEE Transactions on Fuzzy Systems
  • Year:
  • 2000

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Abstract

Presents a kind of adaptive filter: type-2 fuzzy adaptive filter (FAF); one that is realized using an unnormalized type-2 Takagi-Sugeno-Kang (TSK) fuzzy logic system (FLS). We apply this filter to equalization of a nonlinear time-varying channel and demonstrate that it can implement the Bayesian equalizer for such a channel, has a simple structure, and provides fast inference. A clustering method is used to adaptively design the parameters of the FAF. Two structures are used for the equalizer: transversal equalizer (TE) and decision feedback equalizer (DFE). A decision tree structure is used to implement the decision feedback equalizer, in which each leaf of the tree is a type-2 FAF. This DFE vastly reduces computational complexity as compared to a TE. Simulation results show that equalizers based on type-2 FAFs perform much better than nearest neighbor classifiers (NNC) or equalizers based on type-1 FAFs