Abstract
The primary goal of this letter is to provide comparative assessments to the two cases where different criteria are used in joint over antenna minimum mean squared error (JA-MMSE) spatial filtering for space-time coded systems in the presence of unknown interference. It is shown that additional constraints to preserve the space-time coded signal structure in JA-MMSE spatial filtering place floor in bit error rate (BER) performance, while imposing no additional constraint places no error floor.