  We consider channel/subspace tracking systems for temporally correlated
millimeter wave (e.g., E-band) multiple-input multiple-output (MIMO) channels.
Our focus is given to the tracking algorithm in the non-line-of-sight (NLoS)
environment, where the transmitter and the receiver are equipped with hybrid
analog/digital precoder and combiner, respectively. In the absence of
straightforward time-correlated channel model in the millimeter wave MIMO
literature, we present a temporal MIMO channel evolution model for NLoS
millimeter wave scenarios. Considering that conventional MIMO channel tracking
algorithms in microwave bands are not directly applicable, we propose a new
channel tracking technique based on sequentially updating the precoder and
combiner. Numerical results demonstrate the superior channel tracking ability
of the proposed technique over independent sounding approach in the presented
channel model and the spatial channel model (SCM) adopted in 3GPP
specification.
