  In frequency-selective channels linear receivers enjoy significantly-reduced
complexity compared with maximum likelihood receivers at the cost of
performance degradation which can be in the form of a loss of the inherent
frequency diversity order or reduced coding gain. This paper demonstrates that
the minimum mean-square error symbol-by-symbol linear equalizer incurs no
diversity loss compared to the maximum likelihood receivers. In particular, for
a channel with memory $\nu$, it achieves the full diversity order of ($\nu+1$)
while the zero-forcing symbol-by-symbol linear equalizer always achieves a
diversity order of one.
