  We study the information rates of non-coherent, stationary, Gaussian,
multiple-input multiple-output (MIMO) flat-fading channels that are achievable
with nearest neighbor decoding and pilot-aided channel estimation. In
particular, we investigate the behavior of these achievable rates in the limit
as the signal- to-noise ratio (SNR) tends to infinity by analyzing the capacity
pre-log, which is defined as the limiting ratio of the capacity to the
logarithm of the SNR as the SNR tends to infinity. We demonstrate that a scheme
estimating the channel using pilot symbols and detecting the message using
nearest neighbor decoding (while assuming that the channel estimation is
perfect) essentially achieves the capacity pre-log of non-coherent
multiple-input single-output flat-fading channels, and it essentially achieves
the best so far known lower bound on the capacity pre-log of non-coherent MIMO
flat-fading channels. We then extend our analysis to the multiple-access
channel.
