Accurate and Efficient Path Delay Estimation in OMP Based Sparse Channel Estimation for OFDM With Equispaced Pilots

The orthogonal matching pursuit (OMP) algorithm has been widely adopted in sparse channel estimation, both in radio and underwater acoustic communications. Traditionally, the accuracy of path delay estimation in an OMP based channel estimator depends on the adopted delay grid. The finer the delay grid, the higher the estimation accuracy, but meanwhile the higher the computational complexity. In this letter, we propose a modified OMP based channel estimation scheme for orthogonal frequency division multiplexing with equispaced pilots, which utilizes the characteristic of the Hermitian inner product between the pilot-compensated frequency observation vector and the columns of the dictionary matrix to provide a closed-form estimate for the path delays. In addition, a two-step scheme facilitated by Goertzel's algorithm is proposed to search the samples in the closed-form estimation to further reduce the computational complexity. Simulation results and complexity analysis demonstrate the advantages of the proposed scheme in both estimation accuracy and computational complexity.