36 research outputs found
An Experimental mmWave Channel Model for UAV-to-UAV Communications
Unmanned Aerial Vehicle (UAV) networks can provide a resilient communication
infrastructure to enhance terrestrial networks in case of traffic spikes or
disaster scenarios. However, to be able to do so, they need to be based on
high-bandwidth wireless technologies for both radio access and backhaul. With
this respect, the millimeter wave (mmWave) spectrum represents an enticing
solution, since it provides large chunks of untapped spectrum that can enable
ultra-high data-rates for aerial platforms. Aerial mmWave channels, however,
experience characteristics that are significantly different from terrestrial
deployments in the same frequency bands. As of today, mmWave aerial channels
have not been extensively studied and modeled. Specifically, the combination of
UAV micro-mobility (because of imprecisions in the control loop, and external
factors including wind) and the highly directional mmWave transmissions require
ad hoc models to accurately capture the performance of UAV deployments. To fill
this gap, we propose an empirical propagation loss model for UAV-to-UAV
communications at 60 GHz, based on an extensive aerial measurement campaign
conducted with the Facebook Terragraph channel sounders. We compare it with
3GPP channel models and make the measurement dataset publicly available.Comment: 7 pages, 7 figures, 3 tables. Please cite it as M. Polese, L.
Bertizzolo, L. Bonati, A. Gosain, T. Melodia, An Experimental mmWave Channel
Model for UAV-to-UAV Communications, in Proc. of ACM Workshop on
Millimeter-Wave Networks and Sensing Systems (mmNets), London, UK, Sept. 202
Sl-EDGE: Network Slicing at the Edge
Network slicing of multi-access edge computing (MEC) resources is expected to
be a pivotal technology to the success of 5G networks and beyond. The key
challenge that sets MEC slicing apart from traditional resource allocation
problems is that edge nodes depend on tightly-intertwined and
strictly-constrained networking, computation and storage resources. Therefore,
instantiating MEC slices without incurring in resource over-provisioning is
hardly addressable with existing slicing algorithms. The main innovation of
this paper is Sl-EDGE, a unified MEC slicing framework that allows network
operators to instantiate heterogeneous slice services (e.g., video streaming,
caching, 5G network access) on edge devices. We first describe the architecture
and operations of Sl-EDGE, and then show that the problem of optimally
instantiating joint network-MEC slices is NP-hard. Thus, we propose
near-optimal algorithms that leverage key similarities among edge nodes and
resource virtualization to instantiate heterogeneous slices 7.5x faster and
within 0.25 of the optimum. We first assess the performance of our algorithms
through extensive numerical analysis, and show that Sl-EDGE instantiates slices
6x more efficiently then state-of-the-art MEC slicing algorithms. Furthermore,
experimental results on a 24-radio testbed with 9 smartphones demonstrate that
Sl-EDGE provides at once highly-efficient slicing of joint LTE connectivity,
video streaming over WiFi, and ffmpeg video transcoding
The new TAE - Alfvén Wave Active Excitation System at JET
After many years of successful operation, the JET saddle coil system will be dismantled during the 2004-2005 shutdown. A new antenna system has been designed and is being constructed to replace it and excite magneto-hydrodynamics modes in the Alfvén frequency range (10500kHz), keeping similar operational capabilities (IANT~30A, VANT~1kV, maximum power ~5kW). In addition to the constraints imposed by halo current and disruption-induced voltages and currents, the design must comply with the requirements of a remote handling installation. The physics basis, design principles and constraints will be presented along with the results of the coupling and engineering analysis, and a discussion of the possible extrapolation of such a system to ITER
Status of EU\u27s contribution to the ITER EC system
The electron cyclotron (EC) system of ITER for the initial configuration is designed to provide 20MW of RF power into the plasma during 3600s and a duty cycle of up to 25% for heating and (co and counter) non-inductive current drive, also used to control the MHD plasma instabilities. The EC system is being procured by 5 domestic agencies plus the ITER Organization (IO). F4E has the largest fraction of the EC procurements, which includes 8 high voltage power supplies (HVPS), 6 gyrotrons, the ex-vessel waveguides (includes isolation valves and diamond windows) for all launchers, 4 upper launchers and the main control system. F4E is working with IO to improve the overall design of the EC system by integrating consolidated technological advances, simplifying the interfaces, and doing global engineering analysis and assessments of EC heating and current drive physics and technology capabilities. Examples are the optimization of the HVPS and gyrotron requirements and performance relative to power modulation for MHD control, common qualification programs for diamond window procurements, assessment of the EC grounding system, and the optimization of the launcher steering angles for improved EC access. Here we provide an update on the status of Europe’s contribution to the ITER EC system, and a summary of the global activities underway by F4E in collaboration with IO for the optimization of the subsystems