Position-Based Compressed Channel Estimation and Pilot Design for High-Mobility OFDM Systems

With the development of high-speed trains (HSTs) in many countries, providing broadband wireless services in HSTs is crucial. Orthogonal frequency-division multiplexing (OFDM)
has been widely adopted for broadband wireless communications
due to its high spectral efficiency. However, OFDM is sensitive
to the time selectivity caused by high-mobility channels, which
costs much spectrum or time resources to obtain the accurate
channel state information (CSI). Therefore, the channel estima-tion in high-mobility OFDM systems has been a long-standing challenge. In this paper, we first propose a new position-based
high-mobility channel model, in which the HST’s position infor-mation and Doppler shift are utilized to determine the positions
of the dominant channel coefficients. Then, we propose a joint
pilot placement and pilot symbol design algorithm for compressed
channel estimation. It aims to reduce the coherence between the
pilot signal and the proposed channel model and, hence, can improve channel estimation accuracy. Simulation results demon strate that the proposed method performs better than existing
channel estimation methods over high-mobility channels. Further-more, we give an example of the designed pilot codebook to show
the practical applicability of the proposed scheme.

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