Computationally Efficient Blind Estimation of Carrier Frequency Offset for MIMO-OFDM Systems

In this paper, we propose a new computationally efficient blind carrier frequency offset (CFO) estimator for multi-input multi-output orthogonal frequency division multiplexing systems. A cost function is carefully designed and can be exactly expressed as the superposition of very few harmonically related cosine waves even with the effect of the noise. Using this property, the minimization of the designed cost function can be solved in a quite computationally efficient manner without any exhaustive grid search procedure. It is seen that the proposed estimator can achieve comparable estimation performance as existing competitors with substantially reduced computational burden. Moreover, in order to improve the estimation performance, we further develop an enhanced CFO estimator by introducing an additional one-step adjustment. We find that the enhanced estimator can attain almost the same estimation performance as the existing maximum likelihood estimator but with a lower order of computational burden. We provide both numerical results and theoretical performance analysis to corroborate the proposed studies.

I. Introduction

As one of the key components for broadband wireless communications, multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) has drawn substantial research interests. MIMO can exploit spatial resources and provide high capacity, while OFDM is immune to frequency-selective fading. However, these advantages depend heavily on the precise estimation and compensation of the carrier frequency offset (CFO) between the transceivers [1].