Adaptive beamforming schemes for interference cancellation in OFDM communication systems

We propose adaptive beamforming schemes for OFDM-based communication systems. After applying the DFT operation to the output of each antenna, one estimates the signal plus interference spatial correlation matrix by selecting the samples at "nonzero-valued" subcarriers, and the interference-alone spatial correlation matrix by choosing those samples at "zero-valued" subcarriers (also known as virtual carriers). It is shown that the beamforming weight vector yielding the optimum signal to interference plus noise ratio is the "largest" generalized eigenvector of the resulting matrix pencil, wherein the solution is computed in a batch fashion. The adaptive solution for calculating the beamforming weight vector is also derived. The simulations presented here employ the OFDM signal model to illustrate the efficacy of the proposed algorithms.