Energy-Effective Offloading Scheme in UAV-Assisted C-RAN System

In this article, we aim to minimize the total power of all the Internet of Things Devices (IoTDs) by jointly optimizing user association, computational capacity, transmit power, and the location of unmanned aerial vehicles (UAVs) in an UAV-assisted cloud radio access network (C-RAN). In order to solve this nonconvex problem, we propose an effective algorithm by solving four subproblems iteratively. For the user association and the computational capacity subproblems, the nonconvex constraints are relaxed and the optimal solutions are obtained. For the transmit power control and the location planning subproblems, the successive convex approximation (SCA) technique is used to transform the nonconvex constraints into convex ones. Moreover, to obtain the suboptimal solutions, slack variables are also introduced to deal with the feasibility-check problems. The simulation results demonstrate that the proposed algorithm can greatly reduce the total power consumption of IoTDs.

I. Introduction

Nowadays, the explosive growth of data services has posed an increasingly high burden on the existing communication systems. The connection of mobile devices is estimated up to 29.3 billion by the year of 2023 [1]. It is urgent to introduce new techniques to couple the technical challenge by such boosting. Unmanned aerial vehicles (UAVs) assisted communications is one of the promising candidates that have attracted extensive research attention [2]. Compared to the traditional ground wireless communication systems, UAV-assisted networks can provide higher mobility and probability of Line-of-Sight (LoS) networks links between the UAVs and the Internet of Things Devices (IoTDs) [3]–[6]. Hence, UAVs can be utilized as flying base station (FBS) [7], [8], relaying [4], [9] and wireless power transfer station [10], [11], etc. Besides, thanks to the flexibility of UAV, it can handle special situations, such as providing emergency communication in a disaster-stricken region [12] and enhancing communication safety [13].