A New DFT-Based Channel Estimation Approach for OFDM with Virtual Subcarriers by Leakage Estimation

Equidistance in pilot spacing is an essential condition for discrete Fourier transform (DFT)-based channel estimation in OFDM systems. However, virtual subcarriers break this condition, degrade the estimation performance, and cause the interference (called ´´leakage´) because the orthogonality of Fourier matrix is broken. To solve this problem, we first analyze the leakage using the DFT-inverse DFT process. The pilot subcarriers inside virtual subcarriers area are estimated by the inverse of the estimated leakage. Thus, the equidistance condition is satisfied. The proposed estimator operates well in realistic environment such as IEEE 802.16, and it is robust to an increase of virtual subcarriers.