The Effects of Fuzzy Logic on Carrier Frequency Offset Tracking Performance of Single and Multi Carrier Communication Systems

In this paper, carrier frequency offset (CFO) tracking performances of channel equalizers for single (SC) and multi carrier (MC) systems used in frequency selective Rayleigh fading channels are investigated. The performances of both systems for different values of CFO are compared. Since the desired performance cannot be achieved by CFO tracking ability of conventional LMS for SC and MC systems used in time varying channels, a fuzzy logic based LMS (F-LMS) algorithm is proposed. CFO tracking performance with the proposed F-LMS algorithm becomes very close to the performance of RLS algorithm with a small and negligible increment in computational complexity. Computer simulations using conventional LMS, normalized LMS, modified LMS, variable step size LMS-DFE, B-LMS-DFE and conventional RLS-DFE algorithms are performed in SC systems. The same algorithms are also used in MC (OFDM) systems in which the channel is estimated in time domain then used in frequency domain channel equalizer. For performance comparisons, the HIPERLAN/1 (SC) and HIPERLAN/2 (OFDM) standards are used as the working platforms during simulations. The obtained and compared results are given in Section 3