UAV Relay-Assisted Emergency Communications in IoT Networks: Resource Allocation and Trajectory Optimization

in IEEE Transactions on Wireless Communications (2022), 21(3), 1621-1637

Unmanned aerial vehicle (UAV) communication hasemerged as a prominent technology for emergency communi-cations (e.g., natural disaster) in the Internet of Things (IoT)networks to enhance the ability of ... [more ▼]

Unmanned aerial vehicle (UAV) communication hasemerged as a prominent technology for emergency communi-cations (e.g., natural disaster) in the Internet of Things (IoT)networks to enhance the ability of disaster prediction, damageassessment, and rescue operations promptly. A UAV can bedeployed as a flying base station (BS) to collect data from time-constrained IoT devices and then transfer it to a ground gateway(GW). In general, the latency constraint at IoT devices and UAV’slimited storage capacity highly hinder practical applicationsof UAV-assisted IoT networks. In this paper, full-duplex (FD)radio is adopted at the UAV to overcome these challenges. Inaddition, half-duplex (HD) scheme for UAV-based relaying isalso considered to provide a comparative study between twomodes (viz., FD and HD). Herein, a device is considered tobe successfully served iff its data is collected by the UAV andconveyed to GW timely during flight time. In this context,we aim to maximize the number of served IoT devices byjointly optimizing bandwidth, power allocation, and the UAVtrajectory while satisfying each device’s requirement and theUAV’s limited storage capacity. The formulated optimizationproblem is troublesome to solve due to its non-convexity andcombinatorial nature. Towards appealing applications, we firstrelax binary variables into continuous ones and transform theoriginal problem into a more computationally tractable form.By leveraging inner approximation framework, we derive newlyapproximated functions for non-convex parts and then develop asimple yet efficient iterative algorithm for its solutions. Next,we attempt to maximize the total throughput subject to thenumber of served IoT devices. Finally, numerical results showthat the proposed algorithms significantly outperform benchmarkapproaches in terms of the number of served IoT devices andsystem throughput. [less ▲]

Physical Layer Security Analysis of SWIPT-Enabled Cooperative Wireless IoT Networks in the Presence of Friendly Jammer and Eavesdropper

in IEEE Internet of Things Journal (2022), 9(21),

—Physical layer security (PLS) and simultane ous wireless information and power transfer (SWIPT) in cooperative relaying have gained great interest as technolo gies for security and energy enhancement in ... [more ▼]

—Physical layer security (PLS) and simultane ous wireless information and power transfer (SWIPT) in cooperative relaying have gained great interest as technolo gies for security and energy enhancement in Internet-of Things (IoT) networks. In this work, we investigate PLS for a SWIPT- and AF-enabled cooperative wireless IoT system, consisting of one source, multiple energy harvesting (EH) relays, and one destination, in the presence of an eaves dropper that tries to overhear the confidential information. Furthermore, an EH-friendly jammer is deployed to trans mit jamming signals aimed at the eavesdropper to improve the security system. In this context, a low complexity, sub optimal, but efficient relay selection method is proposed. More specifically, the relay is selected to convey informa tion such that it has the best channel to the source. Based on the proposed system model, the performance analysis of intercept probability (IP), asymptotic IP, and non-zero secrecy probability (NZSP) is analyzed by considering the time switching (TS)-based relaying strategy. Particularly, Tan N. Nguyen is with the Wireless Communications Re search Group, Faculty of Electrical and Electronics Engineering, Ton Duc Thang University, Ho Chi Minh City, Vietnam. (e mail:nguyennhattan@tdtu.edu.vn). Dinh-Hieu Tran, Symeon Chatzinotas, and Bjorn Ottersten are with ¨ the Interdisciplinary Centre for Security, Reliability and Trust (SnT), the University of Luxembourg, Luxembourg. (e-mail: {hieu.tran-dinh, symeon.chatzinotas, bjorn.ottersten} @uni.lu). Miroslav Voznak is with VSB - Technical University of Ostrava, 17. listopadu 15/2172, 708 33 Ostrava - Poruba, Czech Republic. (e-mail:miroslav.voznak@vsb.cz). H. V. Poor is with the Department of Electrical and Computer Engineering, Princeton University, Princeton, NJ 08544 USA. (email: poor@princeton.edu). Byung-Seo Kim is with the Department of Software and Com munications Engineering, Hongik University, Sejong 30016, South Korea (e-mail: jsnbs@hongik.ac.kr). Corresponding author: Van-Duc Phan is at Faculty of Automobile Technology, Van Lang University, Ho Chi Minh City, Vietnam. (email: duc.pv@vlu.edu.vn). This research was supported by the Ministry of Education, Youth and Sports of the Czech Republic under the grant SP2021/25 and e-INFRA CZ (ID:90140). the exact closed-form expression of IP is achieved applying modified Bessel function expansion. Finally, Monte-Carlo simulations are employed to corroborate the correctness and the efficiency of our mathematical analysis. [less ▲]

Throughput Maximization for Backscatter- and Cache-Assisted Wireless Powered UAV Technology

in IEEE Transactions on Vehicular Technology (2022), 71(5), 5187-5202

This paper investigates a wireless powered unmanned aerial vehicle (UAV) communication network with backscatter and caching technologies. Specifically, we assume a self-energized UAV with a cache memory ... [more ▼]

This paper investigates a wireless powered unmanned aerial vehicle (UAV) communication network with backscatter and caching technologies. Specifically, we assume a self-energized UAV with a cache memory is deployed as a flying backscatter device (BD), term the UAV-enabled BD (UB), to relay the source’s signals to the destination. Whereas the source S can act as a wireless charging station or a base station to supply power or transmit information to the UB using the dynamic time splitting (DTS) method. The UAV utilizes its harvested energy for backscattering (i.e., passive communication) and transmit information (i.e., active communication) to the destination. In this context, we aim to maximize the total throughput by jointly optimizing the DTS ratio and the UB’s trajectory with caching capability at the UB. The formulation is troublesome to solve since it is a non-convex problem. To find solutions, we decompose the original problem into two sub-problems, whereas we first optimize the DTS ratio for a given UB’s trajectory and the UB’s trajectory optimization for a given DTS ratio. By using the KKT conditions, a closed-form expression for the optimal value of the DTS ratio is obtained, greatly reducing the computation time. Moreover, the solution of the second sub-problem can be acquired by adopting the successive convex approximation (SCA) technique. Consequently, an efficient alternating algorithm is proposed by leveraging the block coordinate descent (BCD) method. To show the advantages of the proposed BCD-based algorithm, we also provide the solution of the original problem applying the inner approximation (IA) method. Finally, the intensive numerical results demonstrate that our proposed schemes achieve significant throughput gain in comparison to the benchmark schemes. [less ▲]

5G AND BEYOND NETWORKS WITH UAV: TRAJECTORY DESIGN AND RESOURCE ALLOCATION

Doctoral thesis (2021)

Over the past few years, unmanned aerial vehicle (UAV)-enabled wireless communications have attracted considerable attention from both academia and industry due to their high mobility, low cost, strong ... [more ▼]

Over the past few years, unmanned aerial vehicle (UAV)-enabled wireless communications have attracted considerable attention from both academia and industry due to their high mobility, low cost, strong light-of-sight communication links, and ease of deployment. Specifically, UAVs can be deployed to serve as aerial base stations (BSs), relays, power sources, etc., to support ground users (GUs) in various scenarios such as surveillance missions, search and rescue, crop monitoring, delivery of goods, data collection, emergency communications, secrecy communications, space-air-ground communications, etc. Despite many advantages, UAV-enabled communications are not without limitations. The limitations of UAVs have imposed technical restrictions on weight, size, and energy capability, thereby affecting the durability and performance of UAVs. The key goal of this dissertation is to propose and develop new frameworks and efficient optimization algorithms to solve novel challenging problems, facilitate the design and deployment of UAV-enabled communications. Consequently, these proposed algorithms can become one of the foundations for deploying UAVs in future wireless systems. Specifically, this dissertation investigates different UAV communication systems by addressing several important research problems through four emerging scenarios: 1) Design UAV trajectory based on traveling salesman problem with time window (TSPTW); 2) Full-duplex (FD) UAV relay-assisted emergency communications in Internet of Things (IoT) networks; 3) Backscatter- and cache-assisted UAV communications; and 4) Satellite- and cache-assisted UAV communications in 6G aerial networks. In the first scenario, we provide the coarse trajectory for the UAV based on TSPTW, which has not been investigated in UAV communications yet. Concretely, we propose two trajectory design algorithms based on TSPTW, namely heuristic algorithm and dynamic programming (DP)-based algorithm, and they are compared with exhaustive search and traveling salesman problem (TSP)-based methods. Based on the feasible path obtained from proposed algorithms, we minimize the total UAV’s energy consumption for each given path via a joint optimization of the UAV velocities in all hops. Simulation results show that the energy consumption value of DP is very close to that of the exhaustive algorithm with greatly reduced complexity. Based on this work, an efficient TSPTW-based algorithm can be used as an initialized trajectory for designing a joint problem of UAV trajectory and other communications factors (e.g., communication scheduling, transmit power allocation, time allocation), which are challenges. We then study the case of a FD UAV relaying system in IoT networks. Specifically, a UAV can be deployed as a flying base station (BS) to collect data from time-constrained IoT devices and then transfer it to a ground gateway (GW). Especially, the impact of latency constraint for the uplink (UL) and downlink (DL) transmission utilizing FD or half-duplex (HD) mode is investigated. Using the proposed system model, we aim to maximize the total number of served IoT devices subject to the maximum speed constraint of the UAV, total traveling time constant, UAV trajectory, maximum transmit power at the devices/UAV, limited cache size of the UAV, and latency constraints for both UL and DL. Next, we attempt to maximize the total throughput subject to the number of served IoT devices. The outcome of this work will motivate a new framework for UAV-aided communications in disaster or emergency communications. Next, a novel system model that considers SWIPT, backscatter and caching in UAV wireless networks is developed. Based on this model, we aim to maximize the system throughput by jointly optimizing the dynamic time splitting (DTS) ratio and the UAV’s trajectory with caching capability at the UAV. This is the first work that jointly considers wireless power transfer (WPT), caching, and BackCom in UAV communications, which provides a potential solution for a battery-free drone system that can fly for a long period in the sky to support the terrestrial communication systems. Finally, a novel system model for effective use of LEO satellite- and cache-assisted UAV communication is proposed and studied. Specifically, caching is provided by the UAV to reduce backhaul congestion, and the LEO satellite assists the UAV’s backhaul link. In this context, we aim to maximize the minimum achievable throughput per ground user (GU) by jointly optimizing cache placement, the UAV’s transmit power, bandwidth allocation, and trajectory with a limited cache capacity and operation time. The outcomes of this work can provide a new design framework for Satellite-UAV-terrestrial communications that includes two tiers, i.e., the backhaul link from satellite to UAV and the access link from UAV to ground users, which imposes new challenges and was not investigated before. [less ▲]

Performance Enhancement for Full-Duplex Relaying with Time-Switching-Based SWIPT in Wireless Sensors Networks

in Sensors (2021), 21(11), 3847

Full-duplex (FD) with simultaneous wireless information and power transfer (SWIPT) in wireless ad hoc networks has received increased attention as a technology for improving spectrum and energy efficiency ... [more ▼]

Full-duplex (FD) with simultaneous wireless information and power transfer (SWIPT) in wireless ad hoc networks has received increased attention as a technology for improving spectrum and energy efficiency. This paper studies the outage performance for a SWIPT-based decode-and-forward (DF) FD relaying network consisting of a single-antenna source S, a two-antenna relay R, and a multi-antenna destination D. Specifically, we propose four protocols, namely static time-switching factor with selection combining (STSF-SC), static time-switching factor with maximal ratio combining (STSF-MRC), optimal dynamic time-switching factor with selection combining (ODTSF-SC), and optimal dynamic time-switching factor with maximal ratio combining (ODTSF-MRC) to fully investigate the outage performance of the proposed system. In particular, the optimal time-switching factor from the ODTSF-SC and ODTSF-MRC methods is designed to maximize the total received data at the destination. In this context, we derive exact closed-formed expressions for all schemes in terms of the outage probability (OP). Finally, the Monte Carlo simulations are conducted to corroborate the theoretical analysis’s correctness and the proposed schemes’ effectiveness. [less ▲]

Performance Enhancement for Full-Duplex Relaying with Time-Switching-Based SWIPT in Wireless Sensors Networks

in Ad Hoc Networks (2021)

Full-duplex (FD) with simultaneous wireless information and power transfer (SWIPT) in wireless ad hoc networks has received increased attention as a technology for improving spectrum and energy efficiency ... [more ▼]

Full-duplex (FD) with simultaneous wireless information and power transfer (SWIPT) in wireless ad hoc networks has received increased attention as a technology for improving spectrum and energy efficiency. This paper studies the outage performance for a SWIPT-based decode-andforward (DF) FD relaying network consisting of a single-antenna source S, a two-antenna relay R, and a multi-antenna destination D. Specifically, we propose four protocols, namely static timeswitching factor with selection combining (STSF-SC), static time-switching factor with maximal ratio combining (STSF-MRC), optimal dynamic time-switching factor with selection combining (ODTSFSC), and optimal dynamic time-switching factor with maximal ratio combining (ODTSF-MRC) to fully investigate the outage performance of the proposed system. In particular, the optimal timeswitching factor from the ODTSF-SC and ODTSF-MRC methods is designed to maximize the total received data at the destination. In this context, we derive exact closed-formed expressions for all schemes in terms of the outage probability (OP). Finally, the Monte Carlo simulations are conducted to corroborate the theoretical analysis’s correctness and the proposed schemes’ effectiveness. [less ▲]

UAV Relay-Assisted Emergency Communications in IoT Networks: Resource Allocation and Trajectory Optimization

E-print/Working paper (2020)

Unmanned aerial vehicle (UAV) communication has emerged as a prominent technology for emergency communications (e.g., natural disaster) in Internet of Things (IoT) networks to enhance the ability of ... [more ▼]

Unmanned aerial vehicle (UAV) communication has emerged as a prominent technology for emergency communications (e.g., natural disaster) in Internet of Things (IoT) networks to enhance the ability of disaster prediction, damage assessment, and rescue operations promptly. In this paper, a UAV is deployed as a flying base station (BS) to collect data from time-constrained IoT devices and then transfer the data to a ground gateway (GW). In general, the latency constraint at IoT users and the limited storage capacity of UAV highly hinder practical applications of UAV-assisted IoT networks. In this paper, full-duplex (FD) technique is adopted at the UAV to overcome these challenges. In addition, half-duplex (HD) scheme for UAV-based relaying is also considered to provide a comparative study between two modes (viz., FD and HD). Herein, a device is successfully served iff its data is collected by UAV and conveyed to GW within the flight time. In this context, we aim at maximizing the number of served IoT devices by jointly optimizing bandwidth and power allocation, as well as the UAV trajectory, while satisfying the requested timeout (RT) requirement of each device and the UAV’s limited storage capacity. The formulated optimization problem is troublesome to solve due to its non-convexity and combinatorial nature. Toward appealing applications, we first relax binary variables into continuous values and transform the original problem into a more computationally tractable form. By leveraging inner approximation framework, we derive newly approximated functions for non-convex parts and then develop a simple yet efficient iterative algorithm for its solutions. Next, we attempt to maximize the total throughput subject to the number of served IoT devices. Finally, numerical results show that the proposed algorithms significantly outperform benchmark approaches in terms of the number of served IoT devices and the amount of collected data. [less ▲]

Energy-efficient Trajectory Design for UAV-enabled Wireless Communications with Latency Constraints

Scientific Conference (2019, November 03)

This paper studies a new energy-efficient unmanned aerial vehicle (UAV)-enabled wireless communications, where the UAV acts as a flying base station (BS) to serve the ground users (GUs) within some ... [more ▼]

This paper studies a new energy-efficient unmanned aerial vehicle (UAV)-enabled wireless communications, where the UAV acts as a flying base station (BS) to serve the ground users (GUs) within some predetermined latency limitations, e.g., requested timeout (RT). Our goal is to design the UAV trajectory to minimize the total energy consumption while satisfying the RT requirement from every GU, which is accomplished via two consecutive subproblems: traveling time minimization and energy minimization problems. Firstly, we propose two exhaustive search and heuristic algorithms based on the traveling salesman problem with time window (TSPTW) in order to minimize the UAV’s traveling time without violating the GUs’ RT requirements. While the exhaustive algorithm achieves the best performance at a high computation cost, the heuristic algorithm achieves a trade-off between the performance and complexity. Secondly, we minimize the total energy consumption, for a given trajectory, via a joint optimization of the UAV’s velocity along subsequent hops. Finally, numerical results are presented to demonstrate the effectiveness of our proposed algorithms. In particular, it is shown that the proposed solutions outperform the reference in terms of both energy consumption and outage performance. [less ▲]