Fast blind decision feedback equalizer for mobile links with short blocks

An adaptive algorithm for a blind decision feedback equalizer (DFE) is presented. It is derived from a linear algorithm for blind equalization, the super-exponential algorithm (Supex) introduced by Shalvi and Weinstein (1993) which uses a FIR-filter to approximate the MMSE (minimum mean square error) solution. However there are severe problems for a linear equalizer if zeros of the channel impulse response are on or close to the unit circle as it is likely in mobile radio channels. Then the MMSE solution becomes singular, respectively a large number of filter coefficients are necessary. A nonlinear filter structure like the DFE can handle this problem. We compare also the convergence properties of the Supex and the blind DFE.