Improving Channel Tracking Performance of Single and Multi Carrier Communications with an Outer Loop Controller Based on Fuzzy Logic

In this paper, the channel tracking performances of channel equalizers for Single (SC) and Multi Carrier (MC) systems in frequency selective Rayleigh fading channels are investigated. The performances of both systems for different values of Doppler frequency offset are compared. Since the desired performance cannot be achieved by channel tracking capacity of LMS-DFE in time varying channels for SC systems, a fuzzy logic based LMS (F-LMS) algorithm has been proposed. The proposed F-LMS algorithm causes a small and ignorable increase in computational complexity, however results in a better performance in channel tracking which is very close to the performance of RLS algorithm. Computer simulations using conventional LMS, Normalized LMS, Modified LMS, Variable Step Size LMS-DFE, B-LMS-DFE and conventional RLS-DFE algorithms in SC systems and also using frequency domain channel equalizer in MC (OFDM) systems are performed. The obtained and compared results are given in Section 5.