Compressed channel estimation for high-mobility OFDM systems: Pilot symbol and pilot pattern design

Orthogonal frequency-division multiplexing (OFDM) has been widely adopted for broadband wireless communications due to its high spectral efficiency. However, it is sensitive to the time selectivity caused by the high-mobility, which largely degrades the accurate of estimating the channel state information (CSI). Therefore, the channel estimation in high-mobility OFDM systems has been a long-standing challenge. Recently, numerous experimental studies have shown that high-mobility broadband wireless channels tend to have some inherent sparsity. In this paper, we introduce the compressed sensing (CS) to utilize the inherent channel sparsity and estimate the high-mobility channel. Based on the CS minimization criterion, we propose two off-line pilot design algorithms to improve the estimation performance. One is to design the pilot symbol only and the other is to jointly design the pilot symbol and the pilot pattern. Simulation results show that the proposed methods achieve better estimation performances than conventional linear methods in high-mobility environments.