1,721,004 research outputs found
A Study on Secret Key Rate in Wideband Rice Channel
Full text linkStandard cryptography is expected to poorly fit IoT applications and services, as IoT devices can hardly cope with the computational complexity often required to run encryption algorithms. In this framework, physical layer security is often claimed as an effective solution to enforce secrecy in IoT systems. It relies on wireless channel characteristics to provide a mechanism for secure communications, with or even without cryptography. Among the different possibilities, an interesting solution aims at exploiting the random-like nature of the wireless channel to let the legitimate users agree on a secret key, simultaneously limiting the eavesdropping threat thanks to the spatial decorrelation properties of the wireless channel. The actual reliability of the channel-based key generation process depends on several parameters, as the actual correlation between the channel samples gathered by the users and the noise always affecting the wireless communications. The sensitivity of the key generation process can be expressed by the secrecy key rate, which represents the maximum number of secret bits that can be achieved from each channel observation. In this work, the secrecy key rate value is computed by means of simulations carried out under different working conditions in order to investigate the impact of major channel parameters on the SKR values. In contrast to previous works, the secrecy key rate is computed under a line-of-sight wireless channel and considering different correlation levels between the legitimate users and the eavesdropper
Frequency Diverse Array for Signal Geofencing in Wireless Communications: Does It Work ?
Full text linkFrequency Diverse Array is an advanced antenna technology for clustering received power spatial distribution in specific areas, which has shown significant potential in many applications, including radar or wireless power transfer. In wireless communications, signal geofencing might be beneficial in increasing communication secrecy or reduce interference issues, but system communications through frequency diverse arrays require careful consideration about several design parameters. In this paper, a detailed analysis of the sensitivity of the geofencing effectiveness to the main array parameters is carried out. The analysis covers many aspects of the design, including the selection of the geometrical layout and the number of elements of the array, the frequency increase policy and the frequency offset across the elements and their spacing. The study also discusses the trade-offs between different design choices and provides insights into the performance in terms of focus efficiency and size of the focus area. Results show that bidimensional layouts, e.g. circular or planar, often represent effective solutions, whereas the linear arrangement can be a viable option only in case the frequencies are spread across the elements in a random-like fashion. Frequencies are usually increased according to either a logarithmic or a linear policy. The linear solution in general yields lower performance, but also lower complexity. Frequency offset, number of elements and their spacing represent further project parameters. Finally, a preliminary assessment of the multipath effect on the focus task shows that the performance of frequency diverse arrays can be affected by complex propagation conditions and deserve further investigations
A Simple Empirical Expression for Line-of-Sight Probability in Industrial Environment
No full textThis letter presents a new formula for the line-of-sight probability in the industrial environment. In addition to link distance, the evaluation also considers the relative height of the access point and user equipment concerning the industrial clutter level. The method accuracy is checked against raw data collected through ray tracing simulations. Comparison with existing models shows satisfactory overall performance
Guidelines for RIS Planning in IIoT Scenarios
No full textIndustrial IoT (IIoT) scenarios are known to be challenging in terms of propagation conditions and easily subjected to lack of coverage. For this reason, reconfigurable intelligent surfaces (RIS) can be a smart solution to provide a satisfactory service for future artificial intelligence (AI)-based 6G networks. Nevertheless, RIS is a highly complex technology that requires a proper planning, ad-hoc management, and configuration to gain most benefits. Therefore, this paper aims to provide general guidelines to perform RIS planning in various IIoT scenarios. The planning is aimed at satisfying the stringent IIoT requirements in terms of data rate, reliability, and latency while minimizing the path loss. The results demonstrated the efficacy of RIS implementation in IIoT settings to enhance performance, with a mean path loss improvement of over 30 dB
Multi-Band Outdoor-to-Indoor Propagation Measurements Using a Drone
No full textOutdoor-to-indoor propagation path-loss measurements have been carried out at 27 and 38 GHz, two of the frequencies allocated for 5G networks, for two different buildings: an office glass, steel and concrete building and a brick-wall residential house. The outdoor station has been mounted on a drone in order to have more placement flexibility and reach the desired height above ground without the use of a crane truck. Overall outdoor-to-indoor loss seems to depend primarily on the window surface and on the construction material. While loss is higher at 38GHz with respect to 27 GHz for the office building, brick-walls of the residential house appear to be less frequency selective
A Study on Propagation of Frequency Diverse Array in Multipath Environments
No full textFrequency Diverse Arrays are gaining interest for radar and wireless power transfer applications. Their capabilities to focus the field in a desired area is an interesting property in order to mitigate interference or enhance communications privacy. However, their current applications rely mostly on ideal free space propagation conditions, without considering the effect of multipath propagation in a real environment. In this work, Frequency Diverse Array characteristics and focus capability in real scenarios are primarily investigated through Ray Tracing simulations. Surprisingly, results show an overall fair resistance against multipath thanks to a sort of spatial diversity of the array elements, even though the field distribution undergoes clear spatial fluctuations triggered by multipath interference
A Ray Tracing Tool for Propagation Modelling in Layered Media: a Case Study at the Chip Scale
Full text linkNowadays, many wireless applications require the exchange of electromagnetic waves
through propagation environments that look like to stratified media to some extent. This may concern
both natural scenarios, e.g., air/vegetation/ground, and artificial structures, like meta-materials, photonic
devices, solar cells or systems-on-chip. The characterization of the layered propagation channel is therefore
important for the design and deployment of effective devices and systems. To this aim, the Dyadic Green
Function method has been often leveraged, although its use is usually limited to simple sources, like
short dipoles or current elements. Furthermore, it seems unsuited to assess the dispersive properties of
the channel, which are known to become important when high data-rate must be conveyed. In this paper,
a ray-based approach to propagation inside layers is proposed. As the layered environment can be quite
reverberating, a great number of rays may be needed, to the extent that the corresponding computational
burden might be hardly afforded by general purpose ray tracing tools. Therefore, the ray tracing engine
here presented is specifically conceived for the layered case, and mostly relies on analytical formulation.
The accuracy of the model is checked against measurement carried out at chip scale at optical frequency,
as a reference study case
An all-in-one dual band blade antenna for ads-b and 5g communications in uav assisted wireless networks
Full text linkThis paper is aimed at the characterization and manufacturing of an SMA coaxial fed com-pact blade antenna with dual frequency characteristics for broadband applications on board of Unmanned Air Vehicles (UAVs). This antenna is linearly polarized, and it combines the benefits of Automatic Dependent Surveillance-Broadcast (ADS-B) and 5th Generation (5G) communications in one single element, covering both the 1.030–1.090 GHz and the 3.4–3.8 GHz bands thanks to a bent side and a ‘C’ shaped slot within the radiation element. Starting from the simulation outcomes on an ideal ground plane, the results are here extended to a bent ground plane and on two UAV com-mercial CAD models. Details of manufacturing of the antenna in both aluminium and FR-4 substrate materials are presented. The comparison between measurements and simulations is discussed in terms of return loss, bandwidth, gain, and radiation pattern. Results show an antenna with a low profile and a simple structure that can be employed in various wideband communication systems, suiting future UAV assisted 5G networks while being perfectly compliant with forthcoming ADS-B based Detect-And-Avoid (DAA) technologies in Unmanned Aerial Traffic Management (UTM)
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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