Frequency estimation 27 Channel estimation 6 Estimation 4 Orthogonal frequency division multiplexing 4 Radiofrequencies 4 Algorithms 3 Channel state information 3 Least squares approximations 3 MIMO systems 3 Mean square error 3 Performance 3 Signal to noise ratio 3 Bandpass filters 2 Bit error rate 2 Communication channels (information theory) 2 Computational efficiency 2 Conformal mapping 2 Degrees of freedom (mechanics) 2 Dielectric properties 2 Direction of arrival 2 Extraction 2 Feature extraction 2 Feedback control 2 Frequency allocation 2 Frequency domain analysis 2 Frequency domains 2 History of engineering and technology 2 Inverse problems 2 Microwave measurement 2 Natural frequencies 2