  This paper investigates the feasibility of Dynamic Horizontal Opportunistic
Positioning (D-HOP) use in Drone Small Cells (DSCs), with a central analysis on
the impact of antenna equipment efficiency onto the optimal DSC altitude that
has been chosen in favor of maximizing coverage. We extend the common urban
propagation model of an isotropic antenna to account for a directional antenna,
making it dependent on the antenna's ability to fit the ideal propagation
pattern. This leads us to define a closed-form expression for calculating the
Rate improvement of D-HOP implementations that maintain constant coverage
through antenna tilting. Assuming full knowledge of the uniformly distributed
active users' locations, three D-HOP techniques were tested: in the center of
the Smallest Bounding Circle (SBC); the point of Maximum Aggregated Rate (MAR);
and the Center-Most Point (CMP) out of the two aforementioned. Through analytic
study and simulation we infer that DSC D-HOP implementations are feasible when
using electrically small and tiltable antennas. Nonetheless, it is possible to
achieve average per user average rate increases of up to 20-35% in low user
density scenarios, or 3-5% in user-dense scenarios, even when using efficient
antennas in a DSC that has been designed for standalone coverage.
