Fractionally spaced blind equalization: loss of channel disparity

Under certain conditions on the equalizer length and on the channel dynamics, temporal or spatial diversity allows one to achieve blind equalization perfectly by means of second-order statistics only. Loss of channel disparity causes perfect equalization to no longer be achievable. The achievable channel-equalizes combination then depends only on the part of the multichannel transfer function lacking disparity. We show that the fractionally spaced equalizer adapted by the constant modulus algorithm (FSE-CMA) still achieves “reasonable” equalization. Its performance equals that of the non-fractional CMA, with a slightly shorter baud-length equalizer than the FSE, applied to the part of the channel lacking disparity