Exploring the impact of doubly selective fading channels for communication systems

Abstract

This dissertation investigates the performance of orthogonal frequency division multiplexing (OFDM) systems under doubly selective fading channels. Standardized and custom multipath fading models were simulated to reflect realistic high-mobility environments. Several pilot-aided channel estimation and equalization methods—Least Squares (LS), Minimum Mean Square Error (MMSE), as well as Linear MMSE (LMMSE) with singular value decomposition (SVD) truncation—were evaluated under both block-type and comb-type pilot schemes. Simulation results demonstrate that combining LMMSE estimation with interleaved comb-type pilot insertion yields reliable performance while reducing complexity. Additionally, an interleaved comb-type pilot structure was proposed and shown to enhance robustness against severe multipath and fast fading conditions.