BEM-Based Reconstruction of Time-Varying Sparse Channel in OFDM Systems

In this paper, we propose a pilot-aided channel estimation scheme for Orthogonal Frequency-Division Multiplexing (OFDM) systems where channels are assumed to be both time-varying and sparse. Basis Expansion Models (BEM) are often used to model and reconstruct time-varying channel taps. In this paper, the framework of BEM is applied to OFDM systems with time-varying sparse channels. A new method to detect the positions of significant taps is proposed based on the use of Constant Amplitude Zero Auto Correlation (CAZAC) sequence. Based on the results of detection, BEM based estimation is implemented to estimate the detected taps. The numerical simulations illustrate that the proposed two-step estimation scheme for significant channel taps outperforms direct estimation methods for all the channel taps and also this method can reduce the required pilots and thus reduce the computational load and improve the spectral efficiency.