  This paper introduces an identification method that determines whether a
millimeter-wave wireless transmission using directional antennas is being
established over a line-of-sight (LOS) or a non-line-of-sight (NLOS) cluster
for indoor localization applications. The proposed technique utilizes the
channel power angular spectrum that is readily available from a beam training
process. In particular, the behavior of five different channel metrics, namely
the spatial-domain, time-domain, and frequency-domain channel kurtosis, the
mean excess delay, and the RMS delay spread, is analyzed using maximum
likelihood ratio and artificial neural network. A noticeable difference between
LOS and NLOS clusters is observed and assessed for identification. Hypothesis
testing shows errors as low as 0.01-0.02 in simulation and 0.04-0.07 in
measurements at 60 GHz.
