| Summary: | 碩士 === 國立清華大學 === 通訊工程研究所 === 95 === For orthogonal frequency division multiplexing (OFDM) systems in wireless mo-bile applications, time-variant and multipath fading channels lead to the orthogonality between subcarriers destroyed and introduces intercarrier interference (ICI), resulting in an error floor. We show that severer ICI resulted from doubly selective channels, since signal-to-interference ratio (SIR) of main components of the power of each re-ceived signal in time-variant channels decreases exponentially with the length of de-lay spread increasing. In this study, we propose a novel MLSE scheme to fully exploit the frequency selectivity and temporal diversity to suppress ICI. With further decision feedback and residual ICI cancellation mechanism, performance of our proposed method is very close to the matched-filter (MF) bound. Simulation results indicate that our method is robust to doubly selective channels. We also derive an LMMSE channel estimation method to couple with the MLSE scheme on per state, which op-erates without latency and shows a better performance and more efficient channel bandwidth efficiency than other pilot-based ICI mitigation method from simulations.
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