  In terrestrial communication networks without fixed infrastructure, unmanned
aerial vehicle (UAV)-mounted mobile base stations (MBSs) provide an efficient
solution to achieve wireless connectivity. This letter aims to minimize the
number of MBSs needed to provide wireless coverage for a group of distributed
ground terminals (GTs), ensuring that each GT is within the communication range
of at least one MBS. We propose a polynomial-time algorithm with successive MBS
placement, where the MBSs are placed sequentially starting on the area
perimeter of the uncovered GTs along a spiral path towards the center, until
all GTs are covered. Each MBS is placed to cover as many uncovered GTs as
possible, with higher priority given to the GTs on the boundary to reduce the
occurrence of outlier GTs that each may require one dedicated MBS for its
coverage. Numerical results show that the proposed algorithm performs favorably
compared to other schemes in terms of the total number of required MBSs and/or
time complexity.
