Adaptive Antenna Element Activation for Multiuser Uniform Spherical Arrays

Uniform spherical arrays provide full-space coverage. However, owing to directional element patterns, full-array transmission activates many elements that contribute little to a given user, resulting in increased system overhead and inefficient power allocation. To address this issue, this letter proposes an adaptive element activation strategy for multiuser uniform spherical arrays that reduces the number of physically active elements while satisfying individual user rate requirements. The proposed strategy constructs a user-specific candidate sequence according to the angle between each element boresight and the user direction. At each iteration, it selects, among the unsatisfied users, the user-element connection that provides the largest improvement in the aggregate rate deficit. Simulation results show that fewer than half of the elements are sufficient for a single user to achieve 80% of its full-array rate, while fewer than 70% are sufficient to achieve the full-array rates of all users in multiuser scenarios. Moreover, the proposed strategy consistently requires a lower active-element ratio than the baseline methods across all tested configurations.