1,720,988 research outputs found
Delivering end-to-end statistical QoS guarantees for expedited forwarding"
No full textThis paper presents an admission control frame work for Expedited Forwarding (EF) traffic in a Differentiated Service Network. The aim is to overcome the limitation in terms of achievable efficiency which are proper of a deterministic “worst case” approach based on the zero-los assumption
Off-line configuration of an MPLS over WDM Network under time-varying offered traffic
No full textCoupling MPLS Traffic Engineering on top of a wavelength-routed WDM layer offersgreat flexibility to operatorsto allocate traffic demandsin their networks. In this paper we consider the problem of off-line joint configuration at both packet and optical layers. We consider time-variant offered traffic, and assume that the operator has knowledge of the traffic dynamicsasa set of traffic matricesat different instants. A novel Mixed Integer Linear Programming (MILP) formulation isprop osed, which takesin input this set of traffic matrices, and provide an optimal static configuration capable of accomodating the time-varying traffic. We provide a resolution strategy based on heuristics, and give numerical results for some sample cases. The proposed method iscompared with a simple alternative approach for obtaining a single static solution, to show that our method utilizes much less resources. The solution under the proposed formulation is also compared with the set of solutions obtained by running distinct optimization problems at different instants, showing that the increase of resource is minimal. Hence our approach can provide a static configuration with about the same resources of a fully adaptable dynamical configuration
Optimal routing for protection and restoration in an optical network
No full textIn this paper we provide a centralized method for optimally selecting the set of active and backup paths in an optical transport network in the case of shared-path restoration and 1:1 protection schemes
Embedded SW Design Issues for Distributed Applications on Mobile Terminals
No full textMobile terminals are embedded systems with growing elaboration capacity, even still limited, which are continuously connected to a worldwide communication network. Thus, the idea of embedding in mobile terminals remote computing services seems attractive and it is more and more exploited. This paper evaluates a middleware platform based on the Simple Object Access Protocol (SOAP) to develop distributed applications on mobile terminals
Understanding optimal data gathering in the energy and latency domains of a wireless sensor network
No full textThe problem of optimal data gathering in wireless sensor networks (WSNs) is addressed by means of optimization techniques. The goal of this work is to lay the foundations to develop algorithms and techniques that minimize the data gathering latency and at the same time balance the energy consumption among the nodes, so as to maximize the network lifetime. Following an incremental-complexity approach, several mathematical programming problems are proposed with focus on different network performance metrics. First, the static routing problem is formulated for large and dense WSNs. Optimal data-gathering trees are analyzed and the effects of several sensor capabilities and constraints are discussed, e.g., radio power constraints, energy consumption model, and data aggregation functionalities. Then, dynamic re-routing and scheduling are considered. An accurate network model is proposed that captures the tradeoff between the data gathering latency and the energy consumption, by modeling the interactions among the routing, medium access control and physical layers. For each problem, extensive simulation results are provided. The proposed models provide a deeper insight into the problem of timely and energy efficient data gathering. Useful guidelines for the design of efficient WSNs are derived and discussed. (c) 2006 Elsevier B.V. All rights reserved
Modeling and Simulation of Mobile Gateways Interacting with Wireless Sensor Networks
No full textSensor networks are emerging wireless technologies; their integration with the existing 2.5G, 3G mobile networks is a key issue to provide advanced services, e.g., health control. However this integration poses new challenges in the design and simulation domains since requires the cooperation of simulation tools that model hardware, software, and network aspects and their interactions. We present the modeling and simulation of a network scenario, core of a telecom provider's future portfolio, in which an ARM-based mobile handset is used as the gateway between a wireless sensor network (WSN) and remote users through a wide area network (WAN). Initially, the gateway and the WSN are modeled at system level with SystemC while the wide area network is modeled with NS-2. Then, HW/SW partitioning is performed on the gateway and an instruction set simulator of the ARM processor is used for the cycle-accurate execution of the RTOS and the application software
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Worst-Case Analysis for Deterministic Allocation in a Differentiated Services Network
No full textThe Differentiated Service architecture is proposed as a scalable a proach to QoS for IP networks. Therefore it is based on the aggregate (per class) scheduling of packets, but it aims at providing QoS to single flows. In particular the Expedited Forwarding (EF) Per Hop Behavior (FHB) and the related Premium Service have been defined in order to provide deterministic QoS guarantees to IP flows: zero loss and very low delay and jitter. Hence a possible approach to characterize and to dimension a network using the EF PHB is the worst case analysis. In this work we propose a worst case analysis which provides bounds to the queuing delay for a class of network topologies. Our results are compared with similar available results, which provide ”looser” bounds. The comparison with simulation results shows that. the bound is not enough ti ht to be of practical use. We justify the reason for this behaviour and indicate directions for further improvements
Optimal Data Delivery in Wireless Sensor Networks in the Energy and Latency Domains
No full textIn this paper we address the problem of optimal data gathering in wireless sensor networks (WSN). The goal of this work is to develop algorithms and techniques in order to minimize the data delivery latency and at the same time balance the energy consumption among the nodes, so as to maximize the network lifetime. Following an incremental-complexity approach, several mathematical programming problems are proposed with focus on different network aspects. First, the static routing problem is formulated for large and dense WSNs. Then, an accurate network model is proposed that captures the tradeoff between the data delivery latency and the network energy consumption by modeling the interactions among the routing, medium access control and physical layers. Finally, we consider dynamic rerouting and scheduling. For each problem we provide extensive simulations results for reference scenarios. The proposed models provide a deeper insight into the problem of timely and energy efficient data gathering. Along with the simulation results reported here they provide useful guidelines for the design of effective WSNs
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