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1.
Tzanakaki Anna Varvarigos Emmanouel Muñoz Raul Nejabati Reza Yoshikane Noboru Anastasopoulos Markos 《Photonic Network Communications》2020,40(3):123-125
Photonic Network Communications - 相似文献
2.
Van Caenegem R. Colle D. Pickavet M. Demeester P. Christodoulopoulos K. Vlachos K. Varvarigos E. Stampoulidis L. Roccato D. Vilar R. 《Communications Magazine, IEEE》2007,45(11):52-61
Recent advances in the all-optical signal processing domain report high-speed and nontrivial functionality directly implemented in the optical layer. These developments mean that the all- optical processing of packet headers has a future. In this article we address various important control plane issues that must be resolved when designing networks based on all-optical packet-switched nodes. 相似文献
3.
Kalochristianakis M.N. Paraskevas M. Varvarigos E.A. Xypolitos N. 《Education, IEEE Transactions on》2007,50(4):321-330
The Greek school network (GSN) is a closed nationwide educational network that offers advanced telematic and networking services to all primary/secondary education schools and administration offices in Greece. The primary objective of GSN is the provisioning of a network infrastructure for the interconnection of school PC laboratories so that modern educational methods and pedagogical models can be applied to the school community. GSN has scaled in size, has reached maturity, and is currently delivering a wide range of network and telematic services to its users. The emerging power of open-source software provides a sound technological basis for building cutting-edge services, capable of meeting internal administrative and monitoring needs, and modern pedagogical requirements for tools and services. The current paper presents an overview of GSN and an evaluation of its services based on the opinions of its users, and on service utilization and traffic measurement statistics. The paper reaches the conclusion that open-source solutions provide a sound technological platform that can cover, to a great extent, the needs for advanced educational services of the school community. 相似文献
4.
We propose a new multiwavelength almost all-optical switch architecture called the λ-scheduler that uses wavelength division multiplexing (WDM) internally to fold the switch architecture in both the space and time domains to reduce the hardware complexity and to improve the signal characteristics through the switch. The λ-scheduler preserves the packet order for a given input-output pair, is consistent with virtual circuit switching, and when combined with appropriate connection and flow control protocols, provides lossless communication for bursty (or nonconstant rate) traffic, provided the traffic satisfies certain smoothness properties. The λ-scheduler uses novel scheduling and wavelength assignment algorithms, in conjunction with a series of feed-forward delay blocks, to avoid packet collisions within the switch or at the switch outputs. We present two implementations of the λ-scheduler when the number of internal wavelengths k equal the number of inputs (and outputs) N to the switch. In the compressed λ-scheduler, the N internal wavelengths are used to fold the architecture in the time domain, which reduces the total number of delay blocks for the switch by 2N log N. In the collapsed λ-scheduler, the N internal wavelengths are used to fold the architecture in the space domain, which reduces the number of delay blocks and total fiber length used for delays by a factor of N. We examine the insertion loss for both λ-scheduler implementations and discuss the trade-offs between the reduction in overall component count and the improvement in the signal characteristics 相似文献
5.
Michael N. Kalochristianakis Fotis Georgatos Vasilis Gkamas Giannis Kouretis Emmanouel Varvarigos 《Journal of Grid Computing》2012,10(2):237-248
A determinant factor for the introduction of grid technologies in production domains of scale can be the design of easy, fast
and, from an operational point of view, realizable deployment procedures. Remote system management technologies, typically
used to monitor and manage IT environments, are designed to offer remote software installation functionality that exhibits
the aforementioned characteristics; however, previous work has shown that even valuable systems can fail to perform in heterogeneous,
geographically distributed environments, especially if they are maintained by organizations affiliated to the public sector.
The deployment of grid technologies throughout the Greek School Network can be achieved by combining OpenRSM, a novel open
source solution capable to support usable, configurable, infrastructure management use cases in heterogeneous environments
and LiveWN, a grid scavenging solution that integrates live technologies with gLite grids. 相似文献
6.
We analyze circuit switching in a multiprocessor network, where connection requests (or sessions) arrive at each node of the network according to a Poisson process with rate λ. Each session joins the appropriate input-queue at its source node, and, upon advancing to the head of the queue, transmits a setup packet to establish a connection. If the setup packet is successful, it reserves the links on the path for the duration of the session, and the session is served without interruptions. Otherwise, the connection request remains queued at the source, and subsequent attempts are made to establish the circuit. We analyze the queue of connection requests at the input-buffer of a network link, and obtain analytic expressions for the stability region, the average queuing delay, the average connection time, the average waiting time, and the average total delay, which show how these parameters depend on system variables, such as network dimension and session arrival rate. The queuing analysis focuses on the input-queue of a particular link, and accounts for the interactions with queues of other links through the retrial attempts and the associated probability of success. The queuing analysis is independent of the particular network topology under consideration, as long as the probability that a session arriving at a random time successfully establishes a connection can be calculated for that network. Simulations demonstrate the close agreement between the observed network behavior and that predicted by the analysis 相似文献
7.
Karavas E Ktistis G Xenakis A Georgarakis E 《Drug development and industrial pharmacy》2005,31(6):473-489
In the present study, solid dispersion systems of felodipine (FEL) with polyvinylpyrrolidone (PVP) were developed, in order to enhance solid state stability and release kinetics. The prepared systems were characterized by using Differential Scanning Calorimetry, X-Ray Diffraction, and Scanning Electron Microscopy techniques, while the interactions which take place were identified by using Fourier Transformation-Infrared Spectroscopy. Due to the formation of hydrogen bonds between the carbonyl group of PVP and the amino groups of FEL, transition of FEL from crystalline to amorphous state was achieved. The dispersion of FEL was found to be in nano-scale particle sizes and dependent on the FEL/PVP ratio. This modification leads to partial miscibility of the two components, as it was verified by DSC and optimal glass dispersion of FEL into the polymer matrix since no crystalline structure was detected with XRD. The above deformation has a significant effect on the dissolution enhancement and the release kinetics of FEL, as it causes the pattern to change from linear to logarithmic. An impressive optimization of the dissolution profile is observed corresponding to a rapid release of FEL in the system containing 10% w/w of FEL, releasing 100% in approximately 20 min. The particle size of dispersed FEL into PVP matrix could be classified as the main parameter affecting dissolution optimization. The mechanism of such enhancement consists of the lower energy required for the dissolution due to the amorphous transition and the fine dispersion, which leads to an optimal contact surface of the drug substance with the dissolution media. The prepared systems are stable during storage at 40 ± 1°C and relative humidity of 75 ± 5%. Addition of sodium docusate as surfactant does not affect the release kinetics, but only the initial burst due to its effect on the surface tension and wettability of the systems. 相似文献
8.
The slow start power controlled MAC protocol for mobile ad hoc networks and its performance analysis
We propose and evaluate the performance of a new MAC-layer protocol for mobile ad hoc networks, called the Slow Start Power Controlled (abbreviated SSPC) protocol. SSPC improves on IEEE 802.11 by using power control for the RTS/CTS and DATA frame transmissions, so as to reduce energy consumption and increase network throughput and lifetime. In our scheme the transmission power used for the RTS frames is not constant, but follows a slow start principle. The CTS frames, which are sent at maximum transmission power, prevent the neighbouring nodes from transmitting their DATA frames at power levels higher than a computed threshold, while allowing them to transmit at power levels less than that threshold. Reduced energy consumption is achieved by adjusting the node transmission power to the minimum required value for reliable reception at the receiving node, while increase in network throughput is achieved by allowing more transmissions to take place simultaneously. The slow start principle used for calculating the appropriate DATA frames transmission power and the possibility of more simultaneous collision-free transmissions differentiate the SSPC protocol from the other MAC solutions proposed for IEEE 802.11. Simulation results indicate that the SSPC protocol achieves a significant reduction in power consumption, average packet delay and frequency of RTS frame collisions, and a significant increase in network throughput and received-to-sent packets ratio compared to IEEE 802.11 protocol. 相似文献
9.
10.
Constantine Kyriakopoulos Petros Nicopolitidis Georgios Papadimitriou Emmanouel Varvarigos 《International Journal of Communication Systems》2020,33(14)
Elastic optical networks emerge as a reliable backbone platform covering the next‐generation connectivity requirements. It consists of advanced enabling components that provide the ability for extensive configuration leading to performance improvement in many areas of interest. Higher layer analytics like data from IP traffic prediction can assist in the process of allocating resources at the optical layer. This way, light connections are established more efficiently while targeting specific performance goals. For that purpose, an algorithm is designed and evaluated that exploits traffic prediction of data transfers between nodes of an optical metro or backbone network. Next, it utilizes adaptive functionality based on particle swarm optimization to find paths with available spectrum resources. These resources can facilitate more efficiently the future traffic demand, since traffic prediction data are considered when finding the related paths. The innovative resource allocation method is evaluated using small and very large real topologies. It scales (in execution time and resource usage) according to node increase, executes in feasible time frames, and reduces transponder utilization resulting to increased energy efficiency. 相似文献