  This paper focuses on providing an analytical framework for the
quantification and evaluation of the pointing error at high-frequency
millimeter wave (mmWave) and terahertz (THz) communication links. For this aim,
we first characterize the channel of a point-to-point communication link
between to unstable transmitter (Tx) and receiver (Rx) and then, we derive the
probability density function (PDF) and cumulative distribution functions (CDF)
of the pointing error in the presence of an unstable Tx and Rx as a function of
the antennas' pattern. Specifically, for the standard array antenna, a
closed-form expression is provided for PDF of the pointing error, which is a
function of the number of antenna elements. Moreover, a more tractable
approximate model is provided for the CDF and PDF of pointing error. In
addition, using $\alpha-\mu$ distribution, which is a common model for
small-scale fading of THz links, the end-to-end PDF of the considered channel
is derived and used to calculate the outage probability of the considered
system. Finally, by employing Monte-Carlo simulations, the accuracy of the
analytical expressions is verified and the performance of the system is
studied.
