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The performance of pilot-symbol-assisted channel estimation widely used for OFDM systems is degraded due to the small number of pilot symbols used for higher transmission efficiency. In this paper, we propose a pilot symbol based channel estimation using cross-correlation to improve the estimation performance of the OFDM system with small number of pilot symbols. The proposed technique detects a data symbol using the channel estimated by the pilot symbol and estimates the channel using the estimated data symbol and the pilot symbol. It is shown by computer simulations that the proposed technique outperforms the conventional pilot symbol assisted estimation technique.

In this paper, we propose an efficient estimation technique for time-varying multipath channels by exploiting two dimensional delay-time nature in pilot inserted orthogonal frequency division multiplexing (OFDM) systems. The proposed technique consists of multipath snapshot estimation at periodic channel observation instances over an OFDM block and the linear interpolation of two consecutive multipath snapshots. Two decision-directed data utilizing schemes, data removed and data added correlation schemes, are proposed to enhance the performance of the multipath snapshot estimation.

In this paper, we investigate the conventional windowed DFT-based channel estimation for OFDM systems with guard bands. The conventional method suffers from the edge effect and the pilot position mismatch. In order to solve the problems, we propose an enhanced DFT-based channel estimation using virtual interpolation with guard bands prediction, where linear minimum mean square error (LMMSE) smoothing/prediction and circular frequency shifting are employed. This technique can efficiently mitigate the edge effect caused by the DFT of the truncated channel impulse response and compensate the pilot position mismatch that pilot symbols are not allocated at the first and the last subcarriers in a useful band. Simulation results show that the proposed method has about 5 dB SNR gain at BER=10?3 compared to the conventional method and is as good as the frequency-domain LMMSE method.

This paper proposes an improved discrete Fourier transform-based and pilot-symbol-aided channel estimation (DFT-based PSA CE) for coherent orthogonal frequency division multiplexing (OFDM) systems. Conventional DFT-based PSA CE suffers from the dispersive distortion of an estimated channel impulse response (CIR) caused by virtual carriers. The proposed method estimates an equal-spaced channel frequency response (CFR) in a virtual carrier region by using forward and backward linear prediction (FBLP). Simulation results show that the proposed method outperforms the conventional one with slightly increased complexity and provides a performance similar to the frequency domain linear minimum mean square error (LMMSE) channel estimation with significantly reduced complexity.

A time-varying multipath channel causes co-channel interference (CCI) as well as inter-carrier interference (ICI) in a space-time block coded orthogonal frequency-division multiplexing (STBC-OFDM) system using two transmit antennas and an conventional simplified decoding scheme (SDS). In this paper, we derive the power of the CCI as a function of normalized channel variation rate. Also, we propose a successive interference cancellation (SIC) technique to improve the performance of the STBC-OFDM by considering the CCI mechanism. The proposed SIC technique can compensate the CCI to some extend with slightly increased complexity compared to the SDS.