arXiv:2610.41469v1 Announce Type: new Abstract: Some commercial Wi-Fi access points used in homes and offices have antennas whose orientations can be adjusted manually. However, selecting suitable orientations is difficult for non-expert users, particularly in indoor multipath environments where reflections and polarization effects complicate the relationship between antenna orientation and link quality. We investigate automatic mechanical antenna orientation control for uplink Wi-Fi communication when the set of active stations changes over time. Building on our previously developed antenna-control system, we propose a model-sharing Bayesian optimization (BO) framework that learns the log-capacity of each link using a separate Gaussian process regression (GPR) model. The framework reuses these models across active-station (STA) combinations and optimizes proportional fairness, equivalently maximizing the geometric mean of the active links' capacities. Exploiting the linearity of this objective in log-capacity, we also derive a upper confidence bound (UCB) acquisition function and its gradient. We evaluate the framework through simulations driven by measured channel capacities and experiments with a mechanical Wi-Fi antenna prototype. The results demonstrate that the proposed model-sharing BO achieves better optimization performance than independent state-specific optimization by reusing the models trained on previously observed links.