A smart antenna with pre- and post-FFT hybrid domain beamforming for broadband OFDM system

This paper proposes a smart antenna with pre-FFT beamforming based on eigenanalysis and post-FFT subcarrier diversity for broadband OFDM systems. This method can achieve signal-to-noise ratio (SNR) enhancement due to two independent eigenbeams in the pre-FFT domain and maximum ratio combining in individual subcarriers in the post-FFT domain. Two pre-FFT eigenbeams focus on the efficient combining of desired signal energy as diversity branches while they achieve lower computational load compared with the optimum post-FFT diversity which consists of the same number of FFT circuits as antennas. Computer simulation results show the complexity is reduced by 50% while keeping the similar bit error rate (BER) performance to the optimum diversity in typical cases of multipath environments.