Subspace-based blind and semiblind channel estimation in OFDM systems with virtual carriers using few received symbols

In this paper, we study subspace-based (SS) methods for blind and semiblind channel estimation in OFDM systems with virtual carriers (VC) using few received received symbols. The methods work in both zero-padded (ZP) and cyclic-prefixed (CP) guard interval types, based on viewing the employment of VCs as precoding of the data matrix using a rank-deficient precoder whose columns represent polynomials that have a common divisor with a degree equal to the number of VCs. The proposed method is the first subspace method to work in CP-OFDM systems with VCs using a less-than-block-size number of received symbols. Simulation results demonstrated the effectiveness of the proposed methods.