478 research outputs found
Throughput Maximization for UAV-Aided Backscatter Communication Networks
This paper investigates unmanned aerial vehicle (UAV)-aided backscatter communication (BackCom) networks, where the UAV is leveraged to help the backscatter device (BD) forward signals to the receiver. Based on the presence or absence of a direct link between BD and receiver, two protocols, namely transmit-backscatter (TB) protocol and transmit-backscatter-relay (TBR) protocol, are proposed to utilize the UAV to assist the BD. In particular, we formulate the system throughput maximization problems for the two protocols by jointly optimizing the time allocation, reflection coefficient and UAV trajectory. Different static/dynamic circuit power consumption models for the two protocols are analyzed. The resulting optimization problems are shown to be non-convex, which are challenging to solve. We first consider the dynamic circuit power consumption model, and decompose the original problems into three sub-problems, namely time allocation optimization with fixed UAV trajectory and reflection coefficient, reflection coefficient optimization with fixed UAV trajectory and time allocation, and UAV trajectory optimization with fixed reflection coefficient and time allocation. Then, an efficient iterative algorithm is proposed for both protocols by leveraging the block coordinate descent method and successive convex approximation (SCA) techniques. In addition, for the static circuit power consumption model, we obtain the optimal time allocation with a given reflection coefficient and UAV trajectory and the optimal reflection coefficient with low computational complexity by using the Lagrangian dual method. Simulation results show that the proposed protocols are able to achieve significant throughput gains over the compared benchmarks
Efficiency Maximization for UAV-Enabled Mobile Relaying Systems with Laser Charging
This work studies the joint problem of power and trajectory optimization in
an unmanned aerial vehicle (UAV)-enabled mobile relaying system. In the
considered system, in order to provide convenient and sustainable energy supply
to the UAV relay, we consider the deployment of a power beacon (PB) which can
wirelessly charge the UAV and it is realized by a properly designed laser
charging system. To this end, we propose an efficiency (the weighted sum of the
energy efficiency during information transmission and wireless power
transmission efficiency) maximization problem by optimizing the source/UAV/PB
transmit powers along with the UAV's trajectory. This optimization problem is
also subject to practical mobility constraints, as well as the
information-causality constraint and energy-causality constraint at the UAV.
Different from the commonly used alternating optimization (AO) algorithm, two
joint design algorithms, namely: the concave-convex procedure (CCCP) and
penalty dual decomposition (PDD)-based algorithms, are presented to address the
resulting non-convex problem, which features complex objective function with
multiple-ratio terms and coupling constraints. These two very different
algorithms are both able to achieve a stationary solution of the original
efficiency maximization problem. Simulation results validate the effectiveness
of the proposed algorithms.Comment: 33 pages, 8 figures, accepted for publication in IEEE Transactions on
Wireless Communication
Securing UAV Communications Via Trajectory Optimization
Unmanned aerial vehicle (UAV) communications has drawn significant interest
recently due to many advantages such as low cost, high mobility, and on-demand
deployment. This paper addresses the issue of physical-layer security in a UAV
communication system, where a UAV sends confidential information to a
legitimate receiver in the presence of a potential eavesdropper which are both
on the ground. We aim to maximize the secrecy rate of the system by jointly
optimizing the UAV's trajectory and transmit power over a finite horizon. In
contrast to the existing literature on wireless security with static nodes, we
exploit the mobility of the UAV in this paper to enhance the secrecy rate via a
new trajectory design. Although the formulated problem is non-convex and
challenging to solve, we propose an iterative algorithm to solve the problem
efficiently, based on the block coordinate descent and successive convex
optimization methods. Specifically, the UAV's transmit power and trajectory are
each optimized with the other fixed in an alternating manner until convergence.
Numerical results show that the proposed algorithm significantly improves the
secrecy rate of the UAV communication system, as compared to benchmark schemes
without transmit power control or trajectory optimization.Comment: Accepted by IEEE GLOBECOM 201
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