Robust pilot detection techniques for channel estimation and symbol detection in OFDM systems

Orthogonal frequency-division multiplexing (OFDM) has been widely used for many communication technologies nowadays due to its high spectral efficiency, robustness against inter-symbol-interference and multipath fading, simplicity for implementation, and so on. In this paper, we propose the frequency-domain pilot multiplexing techniques (FDPMTs) for the channel estimation and equalization in OFDM systems. A robust and effective pilot insertion and detection scheme is devised thereby. The information signal sequence resulting from the constellation mapper is spread over all subcarriers by a precoder and certain subcarriers can be nulled for the insertion of training pilots. These pilot positions are optimally selected to minimize the distortion of the transmitted time-domain signal (OFDM modulated signal) caused by the aforementioned subcarrier-removal at the corresponding pilot positions. The associated new receiver structure is also presented, where three different blind pilot-detection techniques are designed without any a priori knowledge of the pilot positions (based on sample variance, subspace decomposition, and Jarqur-Bera (JB) statistics, respectively), and the distorted data symbols can thus be iteratively reconstructed. Besides, rigorous theoretical analysis and Monte Carlo simulation results both demonstrate that our proposed new OFDM system using dynamical pilot positions is more robust than the conventional OFDM system using the fixed pilot positions over multipath fading channels.