  In this paper, we present a novel mobile user tracking (UT) scheme for
codebook-based intelligent reflecting surface (IRS) aided millimeter wave
(mmWave) systems. The proposed UT scheme exploits the temporal correlation of
the direction from the IRS to the mobile user for selecting IRS phase shifts
that provide reflection towards the user. To this end, the user's direction is
periodically estimated based on a generalized likelihood ratio test (GLRT) and
the user's movement trajectory is extrapolated from several past direction
estimates. The efficiency of the proposed UT scheme is evaluated in terms of
the average effective rate, which accounts for both the required signaling
overhead and the achieved signal to noise ratio (SNR). Our results show that
for medium to high SNR, the proposed codebook based UT scheme achieves a higher
effective rate than two reference approaches based on full codebook search and
optimization of the individual IRS unit cells, respectively.
