Fast-Convergence SMI Adaptive Beamforming Based on Frequency-to-Time Pilot Transform for OFDM System

We propose an adaptive beamforming scheme for the combination of orthogonal frequency division multiplexing (OFDM) and adaptive antenna array. The proposed adaptive beamforming scheme is characterized by the sample matrix inverse (SMI) algorithm, frequency-to-time pilot transform and pre-FFT combination. For every OFDM block containing both data and pilot symbols, we transform the frequency-domain pilot symbols to the corresponding time-domain components. One of the obvious advantages of such transform is that the time interval of the antenna weight vector update can be reduced to only one OFDM sample interval, from one OFDM block interval of the conventional beamforming scheme in which the transform is not applied. This feature can greatly accelerate the convergence of SMI beamforming. The simulation results verify that the proposed beamforming scheme is capable of improving the convergence behavior significantly