  Contemporary wireless communication systems rely on Multi-User Multiple-Input
Multiple-Output (MU-MIMO) techniques. In such systems, each Access Point (AP)
is equipped with multiple antenna elements and serves multiple devices
simultaneously. Notably, traditional systems utilize fixed antennas, i.e.,
antennas without any movement capabilities, while the idea of movable antennas
has recently gained traction among the research community. By moving in a
confined region, movable antennas are able to exploit the wireless channel
variation in the continuous domain. This additional degree of freedom may
enhance the quality of the wireless links, and consequently the communication
performance. However, movable antennas for MU-MIMO proposed in the literature
are complex, bulky, expensive and present a high power consumption. In this
paper, we propose an alternative to such systems that has lower complexity and
lower cost. More specifically, we propose the incorporation of rotation
capabilities to APs equipped with Uniform Linear Arrays (ULAs) of antennas. We
consider the uplink of an indoor scenario where the AP serves multiple devices
simultaneously. The optimal rotation of the ULA is computed based on estimates
of the positions of the active devices and aiming at maximizing the per-user
mean achievable Spectral Efficiency (SE). Adopting a spatially correlated
Rician channel model, our numerical results show that the rotation capabilities
of the AP can bring substantial improvements in the SE in scenarios where the
line-of-sight component of the channel vectors is strong. Moreover, our
proposed system is robust against imperfect positioning estimates.
