Throughput Improvement for Multi-Hop UAV Relaying

Abstract

Unmanned aerial vehicle (UAV) relaying is one of the main technologies for UAV communications. It uses UAVs as relays in the sky to provide reliable wireless connection between remote users. In this paper, we consider a multi-hop UAV relaying system. To improve the spectrum efficiency of the system, we maximize the average end-to-end throughput from the source to the destination by jointly optimizing the bandwidth allocated to each hop, the transmit power for the source and relays, and the trajectories of the UAVs, subject to constraints on the total spectrum bandwidth, the average and peak transmit power, the UAV mobility and collision avoidance, and the information-causality of multi-hop relaying. The formulated optimization is non-convex. We propose an efficient algorithm to approximate and solve it, using the alternating optimization and successive convex optimization methods. Numerical results show that the proposed optimization significantly outperforms other benchmark schemes, verifying the effectiveness of our scheme. INDEX TERMS Bandwidth allocation, multi-hop relaying, power allocation, trajectory optimization, UAV communication. I. INTRODUCTION Due to the advantages of high flexibility, low cost, and ease of use, unmanned aerial vehicles (UAVs) have been widely used in cargo delivery, traffic monitoring, precision agriculture, and so on. Recently, research has shown that integrating UAVs into communication systems is an effective way to improve wireless performance and it has the following advantages [1], [2]. First, on-demand UAV wireless communication system can be swiftly deployed with low cost for temporary and emergent coverage. Second, lineof-sight (LoS) links can be established between UAVs and ground nodes or between different UAVs with high probability, which can improve the link quality of the system. Third, the communication performance of a UAV wireless communication system can be improved by adaptive resource allocation along with UAV trajectory design. On the other The associate editor coordinating the review of this manuscript and approving it for publication was Shravana Musunuri.

Softwarization of UAV Networks: A Survey of Applications and Future Trends

“…The energy constraint of UAVs also causes UAV failures, which could disrupt the overall network [117]. Both maintenance of the connectivity and reducing energy consumption allow providing a certain degree of reliability and a predefined threshold of QoS [118]. To design a fully cooperative UAV network, a set of rules is required to define how data should be exchanged between UAVs and ground BSs [119].…”

Joint Trajectory and Resource Optimization for UAV-Enabled Relaying Systems

“…We define η sch (A r+1 , Q r , P r ), η tra (A r+1 , Q r+1 , P r ), and η pow (A r+1 , Q r+1 , P r+1 ) as the (k + 1)-th objective value of problems (14), (15), and (19) based on the k-th iteration result (A r , Q r , and P r ), respectively. Moreover, η lb,r tra (A r+1 , Q r+1 , P r ) is the objective value of problem (18) with the help of SCA, and η(A r , Q r , P r ) is the objective value of problem (13) based on the k-th iteration result.…”

“…In this paper, we focus on a UAV-aided mobile relaying system. Firstly, in this system, a UAV is typically applied as a mobile relay with the limited mobility to provide wireless connectivity among users when direct links are not reliable [9]- [15]. In [9], a UAV works as a mobile relay to deliver data between a transmitter and a receiver to maximize the receiver rate.…”

“…It maximizes the security rate by optimizing the UAV's trajectory and nodes' powers. Reference [15] studies a multi-hop UAV relaying system through optimizing the available resources among nodes and UAVs' trajectories to maximize the end-to-end throughput.…”

“…Moreover, references about trajectory optimization problems have been classified into two cases, according to UAVs' scopes of activities (mobility) in this paper. On one hand, the study on trajectory optimization problems with a limited mobility UAV, in end-to-end communication systems [9]- [15], is now classical in the literature. However, as far as multiple users are involved and the UAV aims to gain better mobility to enhance the system performance, the trajectory optimization problem will still be challenging.…”