Joint Trajectory and Resource Optimization for UAV-Enabled Relaying Systems

Qinbo Chen

doi:10.1109/access.2020.2970439

Abstract

Unmanned aerial vehicles (UAVs) have attracted attentions due to their mobility and high possibility of the line of sight (LoS) channel. We can fully use these two properties by carefully optimizing the UAVs' trajectories and cooperating with some facilities. A UAV working as a mobile relay now attracts many interests due to its low cost and reliable performance. In this paper, we study a relaying system, where a UAV works as an aerial mobile relay to help some ground base stations send information to ground users periodically by using time division multiple access (TDMA). We aim to maximize the minimum average user rate through solving a non-convex and information causality constraints involved problem by jointly optimizing the UAV trajectory, nodes scheduling, and power allocation to ensure the fairness among all users. Finally, we propose an efficient iterative algorithm to solve a derived mixed-integer non-convex optimization problem to achieve this target by using block coordinate descent (BCD) and successive convex approximation (SCA) methods and prove the convergence of our algorithm. Simulations show the effectiveness of our proposed algorithm, some useful trade-offs and insights about the structure of our optimized trajectory, and the influence of two widely used trajectory initialization methods.

Highlights

Unmanned aerial vehicles (UAVs) have been widely applied both in military surveillance and in civilian applications such as the security and rescue due to the development of modern electronics and software technologies [1]
In wireless cellular communication systems, applications about UAV communications can be categorized into two typical cases: 1) Cellular-enabled UAV communication, where UAVs can be seen as legal users served by ground base stations (GBSs), they can be used in the package delivery and reconnaissance
Low-latency, and higher data rate service [3]; 2) UAV-assisted cellular communication, where UAVs can be applied as base stations or relays to enhance the communication system performance efficiently

Summary

INTRODUCTION

Unmanned aerial vehicles (UAVs) have been widely applied both in military surveillance and in civilian applications such as the security and rescue due to the development of modern electronics and software technologies [1]. Reference [23] uses an AF UAV relay to deliver data among multiple user pairs It maximizes the minimum paired user rate by jointly optimizing the UAV’s trajectory and all available resources. We formulate the problem, which maximizes the minimum average user rate by optimizing the power allocation, UAV trajectory, and nodes scheduling, subject to the constraints on the mobility of a UAV, limited resources, and the information causality. This problem is highly non-convex due to coupled variables, and information causality constraints caused by backhaul links with uneven loads. The Euclidean norm of a vector a is denoted by ||a||

SYSTEM MODEL

1: Trajectory and Power Allocation Initialization

CONVERGENCE ANALYSIS

TRAJECTORY INITIALIZATION

CONCLUSION