Multi-element antenna with close spacing for highly mobile OFDM systems

In this paper, we consider employing a multi-element antenna (MEA) with close spacing to tackle the challenging channel estimation (CE) in highly mobile OFDM systems. Instead of large spacing for diversity, we propose to place the adjacent elements with one symbol distance in the moving direction to observe the quasi-duplicated channels in temporal difference of one symbol period. In exploiting the quasi-duplicated channels, we developed a novel CE-symbol detection (SD) iteration that cooperates with the standardized comb-type pilots to track fast varying channels. From simulation results, we show the proposed system outperforms the conventional receiver of two antennas with spatial diversity in highly mobile channels as long as the mutual coupling effects with the close-spaced elements are restricted.