Orthogonal Frequency Division Multiplexing for Wireless Communications

Orthogonal frequency division multiplexing (OFDM) is a promising technique for high-data-rate wireless communications because it can combat inter-symbol interference (ISI) caused by the dispersive fading of wireless channels. The proposed research focuses on techniques that improve the performance of OFDM based wireless communications and its commercial and military applications. In particular, we address the following aspects of OFDM: inter-carrier interference (ICI) suppression, co-channel interference suppression for clustered OFDM, clustered OFDM based anti-jamming modulation, channel estimation for MIMO-OFDM, and precoding for MIMO-OFDM with channel feedback. For inter-carrier interference suppression, a frequency domain partial response coding (PRC) scheme is proposed to mitigate ICI. We derive the near-optimal weights for PRC that are independent of the channel power spectrum. The error floor resulting from ICI can be reduced significantly using a two-tap or a three-tap PRC. Clustered OFDM is a new technique that has many advantages over traditional OFDM. In clustered OFDM systems, adaptive antenna arrays can be used for interference suppression. To calculate weights for interference suppression, we propose a polynomial-based parameter estimator to mitigate the severe leakage of the discrete Fourier transform (DFT)-based estimator due to the small size of each cluster. An approximately optimal window size for the polynomial-based estimator is obtained and an adaptive algorithm is developed to obtain the optimal window size. With the adaptive algorithm, the polynomial-based estimator has no leakage and does not require channel statistics.