1,720,998 research outputs found
The role of ground-to-air handovers in B5G UAV-aided mobile networks
No full textIn this paper, we study the potential advantages of integrating Unmanned Aerial Vehicles (UAVs) equipped with Base Stations, with a terrestrial mobile network infrastructure. In particular, our main focus here lays on handover and its role in B5G (Beyond 5G) networks. We consider a scenario where multiple UAVs and terrestrial bases jointly provide service to mobile ground users. By combining the UAV dynamic trajectory and radio access procedures, we investigate the impact and network performance of ground-to-air handovers. With respect to previous papers, we discuss how to optimise the UAV segment of the network. Final results show that the UAV needs to adjust its speed, height and antenna radiation angle to improve network performance
Modeling UAV-Based IoT Clustered Networks for Reduced Capability UEs
Full text linkIn recent years, the use of unmanned aerial vehicles (UAVs) for wireless communications has been shown promising in a plethora of different applications. Their flexible deployment and mobility make them key enablers for the next generation of networks, provided that system design is properly addressed. In this article, we analyze a beyond-5G network where a UAV, acting as an unmanned aerial base station (UAB), is employed to collect data from reduced capability user equipments (UEs), deployed in an urban area. Specifically, we study a cluster-based scenario, where UEs are deployed following a Thomas cluster process, and the UAB flies over cluster centers according to the traveling salesman problem solution. Through the use of a stochastic approach, we mathematically devise the system performance accounting for uplink transmission protocol constraints, random access procedure, finite number of radio resources available, and coverage issues during the UAB flight. The mathematical model, validated via comparison with simulations, allows to optimize some system parameters, like the UAB speed, the number of UEs per cluster, and the number of radio resources to be used for the access and for data transmissions
On The Modelling of UAV-Aided Networks Using NarrowBand-IoT
No full textIn this paper, we consider a NarrowBand-Internet of Things (NB-IoT) network where an Unmanned Aerial Vehicle (UAV), acting as Unmanned Aerial Base Station (UAB), is employed to collect data from IoT nodes deployed in a service area. Due to the UAB inherent mobility and NB-IoT protocol constraints, the design of proper parameters setting is not an easy task. To try and solve this problem, we analyse the scenario through stochastic tools, allowing to introduce an appropriate relation between protocol and UAB flight parameters, together with application requirements. Specifically, we study a cluster-based scenario, where IoT nodes are assumed to be deployed according to a Thomas cluster process, and we apply a Traveling Salesman Problem to design the UAB trajectory over the area. Notably, our model considers the protocol constraints, in terms of resource units available in the NB-IoT NPUSCH channel, the random access procedure implemented in the NPRACH channel and the data rate that can be provided to IoT nodes. Results allow to quickly deduce optimal design parameters for achieving the maximum network throughput
Metaheuristic Algorithms for UAV Trajectory Optimization in Mobile Networks
No full textWe consider a mobile network in which traditional static terrestrial base stations are not capable of completely serving the existing user demand, due to the huge number of connected devices. In this setting, an equipped Unmanned Aerial Vehicle (UAV) can be employed to provide network connection where needed in a flexible way, thereby acting as an unmanned aerial base station. The goal is to determine the best UAV trajectory in order to serve as many users as possible. The UAV can move at different speeds and can serve users within its communication range, although the data rate depends on the positions of UAV and users. In addition, each user has a demand (e.g., the number of bits the user wants to download/upload from/to the network) and a time window during which requires the service. We propose a Biased Random-Key Genetic Algorithm (BRKGA) and a Simulated Annealing Algorithm (SAA), and compare them on realistic instances with more than 500 users in different settings
Reinforcement Learning-Based Trajectory Planning For UAV-aided Vehicular Communications
No full textIt is widely expected that 6G networks will rely on Unmanned Aerial Vehicles (UAVs) acting as flying Base Stations (BSs) to provide a wide range of services that current networks cannot handle. One of the major trends deals with Vehicle-To-Everything (V2X) communications, where vehicles must be connected to the network to offer applications such as advanced driving and extended sensing. In this context, vehicles could deeply count on flying BS to increase the throughput or reduce the experienced latency, thus satisfying such services constraints. Consequently, path planning must be designed so that UAVs can keep stable links with moving vehicles. In this sense, Reinforcement Learning (RL) techniques are becoming the main enabler for solving such problem, since they offer the possibility to learn how to act in an environment with little prior information, given that full knowledge of the scenario is usually not available. In this paper, we present a RL-based approach to solve the path planning problem in a vehicular scenario, where UAVs, exploiting beamforming, are required to follow as long as possible moving cars. Different RL architectures, as well as a benchmark solution not using RL, are compared to select the best strategy maximising the sum throughput
On the performance of a uav-aided wireless network based on nb-iot
Full text linkIn recent years, interest in Unmanned Aerial Vehicles (UAVs) as a means to provide wireless connectivity has substantially increased thanks to their easy, fast and flexible deployment. Among the several possible applications of UAV networks explored by the current literature, they can be efficiently employed to collect Internet-of-Things (IoT) data because the non-stringent latency and small-size traffic type is particularly suited for UAVs’ inherent characteristics. However, the implications coming from the implementation of existing technology in such kinds of nodes are not straightforward. In this article, we consider a Narrow Band IoT (NB-IoT) network served by a UAV base station. Because of the many configurations possible within the NB-IoT standard, such as the access structure and numerology, we thoroughly review the technical aspects that have to be implemented and may be affected by the proposed UAV-aided IoT network. For proper remarks, we investigate the network performance jointly in terms of the number of successful transmissions, access rate, latency, throughput and energy consumption. Then, we compare the obtained results on different and known trajectories in the research community and study the impact of varying UAV parameters such as speed and height. Moreover, the numerical assessment allows us to extend the discussion to the potential implications of this model in different scenarios. Thus, this article summarizes all the main aspects that must be considered in planning NB-IoT networks with UAVs
Aqua Virgo: first characterization of mortars and plasters from the inner duct
No full textAqua Virgo is the ancient Roman aqueduct, inaugurated in 19 BC, that today still carries water to Fontana di Trevi. It is the only aqueduct built by ancient Romans for their capital that never stopped working, even when all the other aqueducts have been damaged during barbarian invasions (Pace, 2010). Two sectors of the inner underground duct of the aqueduct have been explored in this research: one still functioning area located under Pincian Hill, from San Sebastianello reservoir to the spiral staircase of Villa Medici, and one segment (now in disuse) between Via del Nazareno, Via dei Due Macelli and Via del Tritone. A total of 17 mortars and plasters samples have been collected from different parts of the inner duct (vault, lateral walls, inner part of walls, covering plasters) and 3 samples also from the cocciopesto of a duct that intersect Aqua Virgo just before Via del Nazareno, named “Y” (Baumgartner, 2017). A multi-analytical approach has been applied for the archaeometric characterization of the materials constituting the binder and the aggregate, and the reactions occurred between them: optical microscopy in thin section (OM), X-ray powder diffraction (XRPD), scanning electron microscopy (SEM-EDS), and thermogravimetric analysis on the binder fraction (TGA). As Aqua Virgo has a millenary working history, the aim of this work is to characterize what are supposed to be original materials from the Roman period and compare them with subsequent restorations; also, to compare the samples from aqueduct “Y”, whom attribution is still unknown (but it is supposed to be antecedent), with the ones of Aqua Virgo.
REFERENCES
Baumgartner M. (2017) - Roma rinascente: la città antica tra Quirinale e Pincio. De Luca editori d'arte, 295 pp.
Pace P. (2010) - Acquedotti di Roma e il De aquaeductu di Frontino. Consiglio Nazionale delle Ricerche (CNR), 326 pp
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