  This paper addresses the mobility problem with the assistance of fluid
antenna (FA) on the user equipment (UE) side. We propose a matrix pencil-based
moving port (MPMP) prediction method, which may transform the time-varying
channel to a static channel by timely sliding the liquid. Different from the
existing channel prediction method, we design a moving port selection method,
which is the first attempt to transform the channel prediction to the port
prediction by exploiting the movability of FA. Theoretical analysis shows that
for the line-ofsight (LoS) channel, the prediction error of our proposed MPMP
method may converge to zero, as the number of BS antennas and the port density
of the FA are large enough. For a multi-path channel, we also derive the upper
and lower bounds of the prediction error when the number of paths is large
enough. When the UEs move at a speed of 60 or 120 km/h, simulation results show
that, with the assistance of FA, our proposed MPMP method performs better than
the existing channel prediction method.
