Optimum Placement of UAV as Relays

IEEE Commun. Surv. Tutorials

et al. 2018

Self Cite

714

346

Unmanned aerial vehicles (UAVs) have gained great interest for rapid deployment in both civil and military applications. UAV communication has its own distinctive channel characteristics compared with widely used cellular and satellite systems. Thus, accurate channel characterization is crucial for the performance optimization and design of efficient UAV communication systems. However, several challenges exist in UAV channel modeling. For example, propagation characteristics of UAV channels are still less explored for spatial and temporal variations in non-stationary channels. Also, airframe shadowing has not yet been investigated for small size rotary UAVs. This paper provides an extensive survey on the measurement campaigns launched for UAV channel modeling using low altitude platforms and discusses various channel characterization efforts. We also review the contemporary perspective of UAV channel modeling approaches and outline some future research challenges in this domain.

Section: A Deterministicmentioning

confidence: 97%

“…• Effective optimization for coverage [11]- [12], reliability [84], [91] and capacity performance in UAV communications…”

Section: Vmentioning

confidence: 99%

A Survey of Channel Modeling for UAV Communications

Khuwaja

Chen

IEEE Commun. Surv. Tutorials

et al. 2018

Self Cite

714

346

2019 IEEE 20th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC)

“…There is a significant interest in using UAVs as relays in recent literature. In [6], the authors considered the optimal placement of a UAV relay that minimizes the outage probability. Other works have addressed the problem of finding the optimal trajectory and transmit power of a mobile relay [7], [8].…”

Section: Introductionmentioning

confidence: 99%

UAV Swarms as Amplify-and-Forward MIMO Relays

Hanna

Krijestorac

Han

et al. 2019

Unmanned aerial vehicles provide new opportunities for performance improvements in future wireless communications systems. For example, they can act as relays that extend the range of a communication link and improve the capacity. Unlike conventional relays that are deployed at fixed locations, UAVs can change their positions to optimize the capacity or range on demand. In this paper, we consider using a swarm of UAVs as amplify-and-forward MIMO relays to provide connectivity between an obstructed multi-antenna equipped source and destination. We start by optimizing UAV placement for the single antenna case, and analyze its dependence on the noise introduced by the relay, its gain, and transmit power constraint. We extend our analysis for an arbitrary UAV swarm and show how the MIMO link capacity can be optimized by changing the distance of the swarm to the source and the destination. Then, we consider the effect of optimizing the positions of the UAVs within the swarm and derive an upper bound for the capacity at any given placement of the swarm. We also propose a simple near optimal approach to find the positions that optimize the capacity for the end-to-end link given that the source and the destination have uniform rectangular arrays.Index Terms-Unmanned aerial vehicle (UAV), amplify and forward relay, MIMO capacity.

“…Non-convex constraints are generally difficult to handle, e.g., (10b), (12b), (13), (14), (15), (16b), (16d) and (17b) etc. Among them, constraints (10b) and (13) are more difficult since the logarithm and exponential functions are involved.…”

Section: B Algorithm Designmentioning

confidence: 99%

“…Firstly, let us focus on constraints (10b) and (13). Since the log 2 (·) function is concave, (10b) can be readily viewed as a DC function.…”

Section: B Algorithm Designmentioning

confidence: 99%

Efficiency Maximization for UAV-Enabled Mobile Relaying Systems With Laser Charging

Shi

IEEE Trans. Wireless Commun.

2020

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 energycausality 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. Index TermsMobile relaying, trajectory and power optimization, UAV communication, wireless power transfer.