Search results for "NETWORKING"
showing 10 items of 1776 documents
Impact of Spreading Factor Imperfect Orthogonality in LoRa Communications
2017
In this paper we study the impact of imperfect-orthogonality in LoRa spreading factors (SFs) in simulation and real-world experiments. First, we analyze LoRa modulation numerically and show that collisions between packets of different SFs can indeed cause packet loss if the interference power received is strong enough. Second, we validate such findings using commercial devices, confirming our numerical results. Third, we modified and extended LoRaSim, an open-source LoRa simulator, to measure the impact of inter-SF collisions and fading (which was not taken into account previously in the simulator). Our results show that non-orthogonality of the SFs can deteriorate significantly the perform…
SREP: An Energy Efficient Relay Protocol for Wireless Sensor Networks
2018
While wireless sensor networks continue to break new grounds in applications, favored by technological innovations, energy efficiency continues to stagnate. Duty cycling remains the most popular and effective technique used to improve energy efficiency and thus lifetime of the network. Nevertheless, duty cycling imposes temporary unavailability on the network leading to deterioration of quality of service. To take care of this rather contradicting reality, this paper proposes Sleep Relay Protocol (SREP). Network nodes are divided into sets according to their location and the sets sleep in relay within a duty cycle period. Two set formation algorithms are proposed at initiation of our propos…
Decentralized Subspace Projection for Asymmetric Sensor Networks
2020
A large number of applications in Wireless Sensor Networks include projecting a vector of noisy observations onto a subspace dictated by prior information about the field being monitored. In general, accomplishing such a task in a centralized fashion, entails a large power consumption, congestion at certain nodes and suffers from robustness issues against possible node failures. Computing such projections in a decentralized fashion is an alternative solution that solves these issues. Recent works have shown that this task can be done via the so-called graph filters where only local inter-node communication is performed in a distributed manner using a graph shift operator. Most of the existi…
Reducing False Node Failure Predictions in HPC
2019
Future HPC applications must be able to scale to thousands of compute nodes, while running for several days. The increased runtime and node count inconveniently raises the probability of hardware failures that may interrupt computations. Scientists must therefore protect their simulations against hardware failures. This is typically done using frequent checkpoint& restart, which may have significant overheads. Consequently, the frequency in which checkpoints are taken should be minimized. Predicting hardware failures ahead of time is a promising approach to address this problem, but has remaining issues like false alarms at large scales. In this paper, we introduce the probability of unnece…
Developing hand-worn input and haptic support for real-world target finding
2019
Locating places in cities is typically facilitated by handheld mobile devices, which draw the visual attention of the user on the screen of the device instead of the surroundings. In this research, we aim at strengthening the connection between people and their surroundings through enabling mid-air gestural interaction with real-world landmarks and delivering information through audio to retain users' visual attention on the scene. Recent research on gesture-based and haptic techniques for such purposes has mainly considered handheld devices that eventually direct users' attention back to the devices. We contribute a hand-worn, mid-air gestural interaction design with directional vibrotacti…
Error mitigation using RaptorQ codes in an experimental indoor free space optical link under the influence of turbulence
2015
In free space optical (FSO) communications, several factors can strongly affect the link quality. Among them, one of the most important impairments that can degrade the FSO link quality and its reliability even under the clear sky conditions consists of optical turbulence. In this work, the authors investigate the generation of both weak and moderate turbulence regimes in an indoor environment to assess the FSO link quality. In particular, they show that, due to the presence of the turbulence, the link experiences both erasure errors and packet losses during transmission, and also compare the experimental statistical distribution of samples with the predicted Gamma Gamma model. Furthermore,…
RF-Based Human Activity Recognition: A Non-stationary Channel Model Incorporating the Impact of Phase Distortions
2019
This paper proposes a non-stationary channel model that captures the impact of the time-variant (TV) phase distortion caused by hardware imperfections. The model allows for studying the spectrogram of in-home radio channels influenced by walking activities of the home user under realistic non-stationary propagation conditions. The resolution of the spectrogram is investigated for the von-Mises distribution of the phase distortion. It is shown that high-entropy distributions considerably mask fingerprints of the user activity on the spectrogram of the channel. For an orthogonal frequency-division multiplexing (OFDM) system, a computationally simple method for mitigating the undesired phase r…
Embedded Processing and Compression of 3D Sensor Data for Large Scale Industrial Environments
2019
This paper presents a scalable embedded solution for processing and transferring 3D point cloud data. Sensors based on the time-of-flight principle generate data which are processed on a local embedded computer and compressed using an octree-based scheme. The compressed data is transferred to a central node where the individual point clouds from several nodes are decompressed and filtered based on a novel method for generating intensity values for sensors which do not natively produce such a value. The paper presents experimental results from a relatively large industrial robot cell with an approximate size of 10 m ×
Development of a big data bank for PV monitoring data, analysis and simulation in COST Action 'PEARL PV'
2019
COST Action entitled PEARL PV aims at analyzing data of monitored PV systems installed all over Europe to quantitatively evaluate the long-term performance and reliability of these PV systems. For this purpose, a data bank is being implemented that can contain vast amounts of data, which will enable systematic performance analyses in combination with simulations. This paper presents the development process of this data bank.
Towards Diagrammatic Patterns
2008
This article presents the idea that the graphical representation (concrete syntax) of a visual language can be specified based on some pre-defined diagrammatic patterns. A diagram from the Specification and Description Language (SDL) is used as illustration.