Adaptive Space-Frequency Equalization for SC-FDE Systems With Interference

In this paper, we propose a new space-frequency adaptive equalization (SFAE) method for single carrier frequency domain equalization (SC-FDE) systems that can deal with multipath interference from the highly delay-dispersive channel as well as the multiuser interference. Based on the minimum mean square error (MMSE) criterion, we derive the adaptive weights by combining the received multi-antenna signals in the frequency domain. The main computation burdens of the proposed SFAE and the conventional space-time adaptive equalization (STAE) lie in the calculation of the autocorrelation matrix R and its inversion. The autocorrelation matrix in the SFAE is exactly a block Toeplitz matrix whose calculation can be efficiently implemented by the fast Fourier transformation (FFT) and its inversion also has fast algorithms. Compared with the conventional STAE method, the proposed SFAE method has comparable interference suppression performance, but with a lower order computational complexity. Hence, the proposed SFAE should be more attractive from a practical point of view. The numerical results are provided to corroborate the proposed studies.