Blind adaptive beamforming for narrowband co-channel digital communications signals in a multipath environment

The problem addressed is that of narrowband digital cellular communications in the presence of multipath and co-channel interferers having the same symbol rate and same overall signal characteristics as the desired source. For a given signal source, an algorithm is presented for blindly estimating the weight vector yielding the optimum SINR at the beamformer output. The instrumental quantity, denoted S_xx(f), is the Fourier transform of the expected value of the zero-lag autocorrelation matrix for one symbol period. The proposed scheme employs the PRO-ESPRIT algorithm to exploit the relationship between the timing offset and optimum beamforming weight vector for each source and the principal generalized eigenvalues and eigenvectors of the matrix pencil {S_xx(1/T₀), S_xx(O)}, where 1/T₀ is the symbol rate. Simulations are presented showing the rapid convergence of the algorithm and an improvement of several dB over the subspace-constrained Phase-SCORE algorithm