Carrier frequency offset (CFO), which often occurs due to the mismatch between the local oscillators in transmitter and receiver, limits the performance of multiple-input multiple-output (MIMO) wireless communication systems. To recover the CFO, the first step is coarse CFO estimation. This paper presents a neural network (NN) based coarse CFO estimator which has higher compatibility with a variety of MIMO systems, comparing with traditional CFO estimators. Instead of performing closed form calculation as some traditional estimators do, the proposed estimator transforms the estimation problem to a classification problem: classify the optimal coarse CFO estimate from a pool of coarse CFO candidates. Taking the advantage of neural networks, the proposed NN estimator can perform coarse CFO estimations for MIMO systems with different numbers of antennas and a variety of channel models. Meanwhile, the testing results show that the proposed NN estimator has promising performance and wide CFO acquisition range. INDEX TERMS Coarse CFO estimation, MIMO, neural network, higher compatibility. XINMING HUANG (M'01-SM'09) received the Ph.D. degree in electrical engineering from Virginia Tech, in 2001. He was a Member of Technical Staffs with the Wireless Advanced Technology Laboratory, Bell Labs of Lucent Technologies. Since 2006, he has been a Faculty Member with the Department of Electrical and Computer Engineering, Worcester Polytechnic Institute (WPI), where he is currently a Full Professor. His main research interests include the areas of circuits and systems, with an emphasis on reconfigurable computing, wireless communications, information security, computer vision, and machine learning. ZHE FENG received the B.S. degree from Beijing Jiaotong University and the M.S. degree from the University of Michigan at Ann Arbor. He is currently pursuing the Ph.D. degree with the University of Colorado Boulder. His current research interests include wireless communications and software-defined radio. YOUJIAN LIU (S'98-M'01) received the Ph.D. degree in electrical engineering from The Ohio State University, in 2001. He joined the Department of Electrical and Computer Engineering,