Joint 3-D Positioning and Power Allocation for UAV Relay Aided by
Geographic Information
Abstract
In this paper, we study to employ geographic information to address the
blockage problem of air-to-ground links between UAV and terrestrial
nodes. In particular, a UAV relay is deployed to establish communication
links from a ground base station to multiple ground users. To improve
communication capacity, we fifirst model the blockage effect caused by
buildings according to the three-dimensional (3-D) geographic
information. Then, an optimization problem is formulated to maximize the
minimum capacity among users by jointly optimizing the 3-D position and
power allocation of the UAV relay, under the constraints of link
capacity, maximum transmit power, and blockage. To solve this complex
non-convex problem, a two-loop optimization framework is developed based
on Lagrangian relaxation. The outer-loop aims to obtain proper
Lagrangian multipliers to ensure the solution of the Lagrangian problem
converge to the tightest upper bound on the original problem. The
inner-loop solves the Lagrangian problem by applying the block
coordinate descent (BCD) and successive convex approximation (SCA)
techniques, where UAV 3-D positioning and power allocation are
alternately optimized in each iteration. Simulation results confifirm
that the proposed solution signifificantly outperforms two benchmark
schemes and achieves a performance close to the upper bound on the UAV
relay system.