  In conventional multiple-input multiple-output (MIMO) communication systems,
the positions of antennas are fixed. To take full advantage of spatial degrees
of freedom, a new technology called fluid antenna (FA) is proposed to obtain
higher achievable rate and diversity gain. Most existing works on FA exploit
instantaneous channel state information (CSI). However, in FA-assisted systems,
it is difficult to obtain instantaneous CSI since changes in the antenna
position will lead to channel variation. In this letter, we investigate a
FA-assisted MIMO system using relatively slow-varying statistical CSI.
Specifically, in the criterion of rate maximization, we propose an algorithmic
framework for transmit precoding and transmit/receive FAs position designs with
statistical CSI. Simulation results show that our proposed algorithm in
FA-assisted systems significantly outperforms baselines in terms of rate
performance.
