Compensation of the clustering in post-FFT OFDM beamforming using pilot relocation

Beamforming methods using antenna arrays have been used to suppress co-channel interferences in OFDM systems. These methods are grouped into two general classes of pre-FFT and post-FFT schemes. Post-FFT schemes normally exhibit better performance than their pre-FFT counterparts. However, in pilot-assisted OFDM systems the performance of post-FFT schemes drastically degrades due to subcarrier clustering. In this article we show that if the location of the pilots in an OFDM block change periodically the performance of the post-FFT scheme is greatly improved. The performance of this method can even outperform the combined pre/post-FFT schemes.