Search results for "Computer Networks"
showing 10 items of 860 documents
Feasibility of FPGA accelerated IPsec on cloud
2018
Abstract Hardware acceleration for famous VPN solution, IPsec, has been widely researched already. Still it is not fully covered and the increasing latency, throughput, and feature requirements need further evaluation. We propose an IPsec accelerator architecture in an FPGA and explain the details that need to be considered for a production ready design. This research considers the IPsec packet processing without IKE to be offloaded on an FPGA in an SDN network. Related work performance rates in 64 byte packet size for throughput is 1–2 Gbps with 0.2 ms latency in software, and 1–4 Gbps with unknown latencies for hardware solutions. Our proposed architecture is capable to host 1000 concurre…
On the role of symmetry in solving maximum lifetime problem in two-dimensional sensor networks
2016
We analyze a continuous and discrete symmetries of the maximum lifetime problem in two dimensional sensor networks. We show, how a symmetry of the network and invariance of the problem under a given transformation group $G$ can be utilized to simplify its solution. We prove, that for a $G$-invariant maximum lifetime problem there exists a $G$-invariant solution. Constrains which follow from the $G$-invariance allow to reduce the problem and its solution to a subset, an optimal fundamental region of the sensor network. We analyze in detail solutions of the maximum lifetime problem invariant under a group of isometry transformations of a two dimensional Euclidean plane.
Downlink channel access performance of NR-U: Impact of numerology and mini-slots on coexistence with Wi-Fi in the 5 GHz band
2020
Coexistence between cellular systems and Wi-Fi gained the attention of the research community when LTE License Assisted Access (LAA) entered the unlicensed band. The recent introduction of NR-U as part of 5G introduces new coexistence opportunities because it implements scalable numerology (flexible subcarrier spacing and OFDM symbol lengths), and non-slot based scheduling (mini-slots), which considerably impact channel access. This paper analyzes the impact of NR-U settings on its coexistence with Wi-Fi networks and compares it with LAA operation using simulations and experiments. First, we propose a downlink channel access simulation model, which addresses the problem of the dependency an…
Fractional differential calculus for 3D mechanically based non-local elasticity
2011
This paper aims to formulate the three-dimensional (3D) problem of non-local elasticity in terms of fractional differential operators. The non-local continuum is framed in the context of the mechanically based non-local elasticity established by the authors in a previous study; Non-local interactions are expressed in terms of central body forces depending on the relative displacement between non-adjacent volume elements as well as on the product of interacting volumes. The non-local, long-range interactions are assumed to be proportional to a power-law decaying function of the interaction distance. It is shown that, as far as an unbounded domain is considered, the elastic equilibrium proble…
Robust finite-time fuzzy H∞ control for uncertain time-delay systems with stochastic jumps
2014
Abstract This paper investigates the problem of robust finite-time H ∞ control for a class of uncertain discrete-time Markovian jump nonlinear systems with time-delays represented by Takagi–Sugeno (T–S) model. Initially, the concepts of stochastic finite-time boundedness and stochastic finite-time H ∞ stabilization are presented. Then, by using stochastic Lyapunov–Krasovskii functional approach, sufficient conditions are derived such that the resulting close-loop system is stochastically finite-time bounded and satisfies a prescribed H ∞ disturbance attenuation level in a given finite-time interval. Furthermore, sufficient criteria on stochastic finite-time H ∞ stabilization using a fuzzy s…
Metadata-based Personalization in Data Warehouses
2015
Lielā datu noliktavās uzkrāto datu un atskaišu apjoma dēļ, atskaišu izpilde un pārlūkošana var būt nogurdinoša un laikietilpīga. Turklāt, lietotājs ir visai ierobežots savu vēlmju izteikšanā kvalitatīvāku rezultātu iegūšanai (arī komerciālos datu noliktavu atskaišu rīkos). Taču, ir jēga veikt eksperimentus personalizācijas iespēju jomā, kuru mērķis būtu lietotāja vajadzībām atbilstošu datu sniegšana, jo datu noliktavu personalizācijas pētījumi šobrīd ir attīstības stadijā. Pēc veiktā esošo datu noliktavu personalizācijas pieeju salīdzinājuma, pētījums tika attīstīts atskaišu rekomendāciju jomā, kurš balstās uz tiešā vai netiešā veidā iegūtiem lietotāja iestatījumiem par datu noliktavas shēm…
Open government data portal usability: A user-centred usability analysis of 41 open government data portals
2021
Abstract Open government data, as a phenomena, may be considered an important and influential innovation that has the potential to drive the creation of public value via enabling the prevention of corruption, increase in accountability and transparency, and driving the co-creation of new and innovative services. However, in order for open government data to be fully taken advantage of, it must be found, understood, and used. Though many countries maintain open government data portals, the usability of said portals can vary greatly; this is important to understand as the usability of a portal likely impacts the eventual reuse of the data made available there. Acknowledging the importance of …
Transparency-by-design: What is the role of open data portals?
2021
Abstract Transparency in the public sector is one of the most important topics of the current debates on accountable, participatory, and responsive governance. An open government addresses these major topics and aims to encourage the relationships and flows of information between involved stakeholders. This article explores the role of open data portals in supporting these efforts and provides findings regarding the features in the design of these data infrastructures. On the basis of evidence from the concept of transparency-by-design, we argue that transparency is facilitated by open data portals and their features enabling to work with datasets. We therefore propose the list of the categ…
Toward Unified Control of Networks of Switches and Sensors Through a Network Operating System
2018
Wireless sensor networks (WSNs) are an integral part of an Internet of Things (IoT) ecosystem. In fact, a typical IoT service deployment considers an integrated network of switches and sensors (as well as actuators). In order to manage this heterogeneous network infrastructure, the use of software defined networking (SDN) technologies is anticipated. However, existing SDN-enabling technologies consider only isolated networks and there has been no concrete solution that treats the whole network in a unified way. In this paper, a network operating system is proposed as a way to address the above issue. Starting from the open network operating system, which currently supports only OpenFlow net…
Exploiting state information to support QoS in Software-Defined WSNs
2016
Software-Defined Networking (SDN) is a promising paradigm initially proposed for the wired networks which has the potential to change the way in which networks are designed and managed. Recently, its use has been extended to wireless infrastructure-less networks such as ad-hoc and wireless sensor networks. In this paper, we take inspiration from our previous work where a scheme that extends the SDN paradigm to WSNs - called SDN-WISE - was proposed. Differently from OpenFlow, SDN-WISE is stateful; accordingly in this paper we investigate how state can be used to support different levels of QoS in WSNs. In fact, state can be used to represent the level of congestion of a node and rules can be…