Search results for "TELECOMMUNICATIONS"
showing 10 items of 1639 documents
Survey: Intrusion Detection Systems in Encrypted Traffic
2016
Intrusion detection system, IDS, traditionally inspects the payload information of packets. This approach is not valid in encrypted traffic as the payload information is not available. There are two approaches, with different detection capabilities, to overcome the challenges of encryption: traffic decryption or traffic analysis. This paper presents a comprehensive survey of the research related to the IDSs in encrypted traffic. The focus is on traffic analysis, which does not need traffic decryption. One of the major limitations of the surveyed researches is that most of them are concentrating in detecting the same limited type of attacks, such as brute force or scanning attacks. Both the …
Special Section on ITS Services to Smart City Context [Guest Editorial]
2018
The seven articles in this special section focus on new trends and developments in the intelligent transportation markets. Since the earliest of times, transportation has changed and revolutionized society and industry. Many of technology advances were focused on transportation and their means (road, rail, air, water, etc.) even, today there exist several areas of the knowledge that are focused on it. As time goes by, new terms have been established where technology is present as well, for instance, Intelligent Transportation Systems (ITS), Smart Cities, Smart Territory, Blockchain, Internet of Things, virtualization, Cloud computing, Intelligent Vehicles, embedded computing, Deep learning,…
Collaborative development of a CPS-based production system
2019
Abstract The paper describes the collaborative processes and technologies used to develop a prototype for a Cyber-Physical Production System of USB sticks. The development of this system follows the model-based approach where co-simulations of different components, detailed at different level of abstractions, serve as a basis for structured dialogue between specialised teams and agreement on shared interactions. The focus is primarily on the co-simulation technology, allowing a gradual increase of fidelity and independent testing and validation of the composing subsystems. This technology may be equally complemented with group decision-making tools to better support the collaboration during…
Exploiting EDCA for Feedback Channels in Hybrid VLC/WiFi Architectures
2021
In this paper, we consider integrating VLC and WiFi technologies in a scenario in which Light-Emitting-Diodes (LEDs), acting as network access points (APs) for ultra-dense Internet of Things applications, are deployed into an indoor lighting infrastructure. In such a scenario, RF-links can be exploited for complementing VLC-links in dealing with mobility and bidirectional communications, which can be problematic due to the limited coverage areas and self-generated interference of VLC APs. In particular, we consider the possibility of supporting a technology-based duplexing scheme, in which downlink and uplink transmissions are performed by means, respectively, of VLC and WiFi interfaces int…
Combined effect of turbulence and aerosol on free-space optical links
2017
[EN] Despite the benefits of free-space optical (FSO) communications, their full utilization is limited by the influence of atmospheric weather conditions, such as fog, turbulence, smoke, snow, etc. In urban environments, additional environmental factors such as smog and dust particles due to air pollution caused by industry and motor vehicles may affect FSO link performance, which has not been investigated in detail yet. Both smog and dust particles cause absorption and scattering of the propagating optical signal, thus resulting in high attenuation. This work investigates the joint impact of atmospheric turbulence and dust particle-imposed scattering on FSO link performance as part of the…
Thermally Tunable Surface Acoustic Wave Cavities
2020
We experimentally demonstrate the dynamical tuning of the acoustic field in a surface acoustic wave (SAW) cavity defined by a periodic arrangement of metal stripes on LiNbO3 substrate. Applying a dc voltage to the ends of the metal grid results in a temperature rise due to resistive heating that changes the frequency response of the device up to 0.3%, which can be used to control the acoustic transmission through the structure. The timescale of the switching is demonstrated to be of about 200 ms. In addition, we have also performed finite-element simulations of the transmission spectrum of a model system, which exhibits a temperature dependence consistent with the experimental data. The adv…
Design of Measurement-Based Stochastic Wideband MIMO Channel Simulators
2009
In this paper, we propose a method for designing measurement-based stochastic models for simulating wideband multiple-input multiple-output (MIMO) wireless channels. The proposed method allows synthesizing channel transfer functions with the spatial-temporal-frequency correlation properties approximating those of real-world radio channels. The parameters of a channel simulator are determined by fitting the space-timefrequency cross-correlation matrix of the simulation model to the estimated space-time-frequency cross-correlation matrix of a physical channel. For this purpose, an iterative parameter computation algorithm has been developed. The proposed design method is verified by creating …
UWB Channel Measurements for Hand-Portable Devices: A Comparative Study
2007
On-body UWB signal propagation is analyzed using two different types of UWB antennas. For the study, measurements of the frequency response by means of a VNA (vector network analyzer) are performed at 2001 discrete frequency points in the 3 to 6 GHz range. Separated measures are taken for four different transmitter positions on the head and six receiver positions on the body. Channel estimation parameters, such as mean excess delay, delay spread and path loss are obtained. Results are similar for both types of antennas regarding path loss exponent and average power delay profiles.
UWB Channel Measurements for Measures for Hand-Portable and Wearable Devices
2007
On-body UWB signal propagation is analyzed for propagation channels surrounding the body in an usual office environment for an application requiring the transmission of signals recorded from the head to a device such as a mobile phone or a PDA carried by the subject or also from the transmitter on the head to other devices located along the body. For the study, measurements of the frequency response by means of a VNA (Vector Network Analyzer) are performed at 2001 discrete frequency points in the 3 to 6 GHz range. Channel estimation parameters, such as mean excess delay, delay spread and path loss are obtained. Results show that for the transmitter located on top of the head best average pe…
Design and Characterization of a New MV PLC Coupler for Smart Electric Energy Systems
2018
This paper deals with the design, modeling and characterization of a new coupling system for medium voltage (MV) narrow band power line communications (NB-PLC). It exploits the capacitive divider of voltage detecting systems (VDSs) normally used to reveal the mains voltage presence, thus avoiding the use of dedicated MV couplers. The proposed coupling system was patented by the authors. In this paper, the modeling of the VDS capacitive divider is presented, using a proper characterization method. Moreover, the interface card design is described, based on simulation of the whole PLC transmission channel. Laboratory tests are also presented and discussed. More in detail, a frequency response …