Search results for "Computer network"
showing 10 items of 1634 documents
A Multi-Objective Approach to Optimize a Periodic Maintenance Policy
2012
The present paper proposes a multi-objective approach to find out an optimal periodic maintenance policy for a repairable and stochastically deteriorating multi-component system over a finite time horizon. The tackled problem concerns the determination of the system elements to replace at each scheduled and periodical system inspection by ensuring the simultaneous minimization of both the expected total maintenance cost and the expected global system unavailability time. It is assumed that in the case of system elements failure they are instantaneously detected and repaired by means of minimal repair actions in order to rapidly restore the system. A nonlinear integer mathematical programmi…
Capacity Upper Bound of Channel Assembling in Cognitive Radio Networks with Quasistationary Primary User Activities
2013
In cognitive radio networks (CRNs) with multiple channels, various channel-assembling (ChA) strategies may be applied to secondary users (SUs), resulting in different achieved capacity. However, there is no previous work on determining the capacity upper bound (UB) of ChA for SUs under given system configurations. In this paper, we derive the maximum capacity for CRNs with ChA through Markov chain modeling, considering that primary user (PU) activities are relatively static, compared with SU services. We first deduce a closed-form expression for the maximum capacity in a dynamic ChA strategy and then demonstrate that no other ChA strategy can provide higher capacity than that achieved by th…
A cooperative lifetime extension MAC protocol in duty cycle enabled wireless sensor networks
2011
To reduce energy consumption in wireless sensor networks, the concept of duty cycle is used in many MAC protocols. Although these protocols provide efficient energy-conservation solutions, they cannot resolve the energy hole problem in a multi-hop network, where a few nodes near the sink must relay the packets from the rest of the network, and consequently exhaust their batteries earlier. The previously proposed REACT forwarding protocol triggers the cooperation of several nodes to extend transmission range and hop over the highly burdened node, thereby allowing it to save its energy and extend the lifetime of the network. However, the previous work lacked a MAC protocol with a duty cycle. …
Fiber - Optic Loop Network With Active Nodes For An Electrical Power Plant
1990
This paper presents a fiber optic loop network for a measurement and control system of an electric power plant. The network consists of the central computer terminal, the set of specially distributed digital FO links and local station installed at the important power facilities. The well-known FO link advantages contribUte to high reliability and safety of work of the system. The operation of the loop network, treated as an autonomous one, is controlled by a microcomputer system. Transmission protocols and the cooperation with the local station are also described. The proposed loop network model is illustrated with an example of the laboratory - scale system.
Feasibility issues in static output-feedback controller design with application to structural vibration control
2014
Recent results in output-feedback controller design make possible an efficient computation of static output-feedback controllers by solving a single-step LMI optimization problem. This new design strategy is based on a simple transformation of variables, and it has been applied in the field of vibration control of large structures with positive results. There are, however, some feasibility problems that can compromise the effectiveness and applicability of the new approach. In this paper, we present some relevant properties of the variable transformations that allow devising an effective procedure to deal with these feasibility issues. The proposed procedure is applied in designing a static…
QUALITY SYSTEM FOR PRODUCTION SOFTWARE (QSPS): AN INNOVATIVE APPROACH TO IMPROVE THE QUALITY OF PRODUCTION SOFTWARE
2013
A quality system for production software should be part of the quality management system of an organization and can be expressed as objectives in the form of processes, procedures, tools and responsibilities, designed and developed to fulfil the quality requirements. These usually are addressing the customers (external or internal), compliance with standards (effectiveness) waste reduction and better use of resources (efficiency) for continual improvement. Such systems are designed according to the requirements of the standards for quality management, software engineering and information security. Quality systems themselves could not provide all necessary means for driving the organization…
Optimizing the MAC Protocol in Localization Systems Based on IEEE 802.15.4 Networks
2017
Radio frequency signals are commonly used in the development of indoor localization systems. The infrastructure of these systems includes some beacons placed at known positions that exchange radio packets with users to be located. When the system is implemented using wireless sensor networks, the wireless transceivers integrated in the network motes are usually based on the IEEE 802.15.4 standard. But, the CSMA-CA, which is the basis for the medium access protocols in this category of communication systems, is not suitable when several users want to exchange bursts of radio packets with the same beacon to acquire the radio signal strength indicator (RSSI) values needed in the location proce…
A procedure to calculate the five-parameter model of crystalline silicon photovoltaic modules on the basis of the tabular performance data
2013
Abstract Only few manufactures provide the wide set of graphical data that are necessary to use high performance predictive tools for PV systems. On the other hand, reliable graphical data require accurate laboratory measurements that increase manufacturing costs. For this reason PV system designers have to choose between the use of cheap PV modules, lacking in technical data, and the reliable energy predictions that are possible only if the current–voltage characteristics are provided by the PV module manufacturers. This paper describes the procedure to evaluate the parameters of a one-diode equivalent circuit able to accurately represent the electrical behaviour of a PV panel by means of …
Overgrid: A Fully Distributed Demand Response Architecture Based on Overlay Networks
2017
In this paper, we present Overgrid, a fully distributed peer-to-peer (P2P) architecture designed to automatically control and implement distributed demand response (DR) schemes in a community of smart buildings with energy generation and storage capabilities. As overlay networks in communications establish logical links between peers regardless of the physical topology of the network, the Overgrid is able to apply some power balance criteria to its system of buildings, as they belong to a virtual microgrid, regardless of their physical location. We exploit an innovative distributed algorithm, called flow updating, for monitoring the power consumption of the buildings and the number of nodes…
Capacity Analysis in Downlink WCDMA Systems Using Soft Handover Techniques With SIR-Based Power Control and Site Selection Diversity Transmission
2006
This work analyzes the downlink performance of a WCDMA system with site selection diversity transmission power control (SSDT) during soft handover mode. Signal to interference ratio (SIR) power control techniques are modeled and used in the simulations of this analysis. The study is focused on finding the optimum soft handover margin in terms of maximum system capacity under energy-per-bit to noise spectral density ratio (Eb/N0) quality requirements. The results of this analysis show an increase in user capacity of about 15 -20 % for optimum soft handover margins of 5 – 5.5 dB. Nevertheless, the resources required (number of scrambling codes) by base station increase faster than the number …