1,720,991 research outputs found
Spatial and temporal traffic variation in core Networks: Impact on energy saving and devices lifetime
Full text linkWe assess the impact of traffic variations on energy consumption and devices lifetime in a core network. Specifically, we first define a model to control the spatial as well as the temporal variations of traffic. We generate different sets of traffic matrices by adopting our model, which are then used as input to an energy-aware algorithm, with the aim of finding the set of Line Cards (LCs) in Sleep Mode (SM) for each traffic matrix. Given this output, we are able to compute different evaluation metrics, including: the total energy consumption, the normalized lifetime as a consequence of activation/deactivation of network devices, and the total network profitability (i.e., the monetary gain/loss for the operator). Our results show that the temporal variation of traffic affects the LCs energy consumption, but has a limited impact on their lifetime. Moreover, the spatial variation of traffic is no obstacle for energy saving. Eventually, the frequency of the power cycles, introduced by the energy-aware algorithm, is particularly important for the lifetime of LCs. Finally, we show that positive total profitability is achieved in most of the considered cases
Impact of spatial traffic variation on energy savings and devices lifetime in core networks
No full textTraffic variation heavily impacts energy savings achieved by putting Line Cards (LCs) into Sleep Mode (SM) in core Internet Protocol (IP)-over-Wavelength Division Multiplexing (WDM) networks. We propose a simple traffic model covering temporal and spatial traffic variation and investigate the impact of (controlled) traffic variations on energy savings achieved with the Energy Watermark Algorithm (EWA) as well as on devices lifetime in realistic network scenarios. The results indicate that spatial variation of traffic is no obstacle in saving energy in the networks. We point out the need for consistent routing schemes between the reference network (designed with a sophisticated Mixed-Integer Linear Programming (MILP) formulation in our case) and the solutions computed dynamically during network operation (with the lifetime-unaware EWA in our case)
A power consumption sensitivity analysis of circuit-switched versus packet-switched backbone networks
Full text linkA survey on energy-aware design and operation of core networks
No full textA detailed survey of approaches reducing energy consumption of core networks is presented in this paper. We consider a multilayer architecture, in which the optical layer can be realized either with a Wavelength Division Multiplexing (WDM) network or an Elastic Optical Network (EON). We focus on the design and operation stages, i.e., deciding which devices to install in the network during the former step, and choosing which devices to put into sleep mode during the latter one. A taxonomy for classifying the surveyed approaches is provided in order to compare the works covering energy efficiency in core networks (in terms of both optimal formulations and heuristic solutions). Moreover, our work provides a global view of the traffic assumptions, the topologies, and the power consumption models in the literature. The need of further investigations in this field clearly emerges. We envision future works targeting: (1) more effective standardization efforts to practically realize sleep modes; (2) the evaluation of the impact of sleep mode on the device lifetime; (3) the extensive adoption of new paradigms like Software Defined Networking (SDN) and EON; and (4) a radical improvement in the testbed implementations
Is green networking beneficial in terms of device lifetime?
No full textThis article analyzes the impact that sleep mode (SM)-based green strategies have on the reliability performance of optical and cellular network elements. First, we consider a device in isolation (i. e., not plugged into a network in operation), showing how operational temperature and temperature variations, both introduced by SM, impact its lifetime. We then evaluate, from an operational cost perspective, the impact of these lifetime variations, showing that some devices are critical, that is, their achievable energy savings might not cover the potential additional reparation costs resulting from being put in SM too frequently. Moreover, we present a model for evaluating the impact of SM on the lifetime of a device plugged into an operational network. The analysis considers two case studies (one based on the optical backbone and one on cellular networks) showing that the lifetime of a device is influenced by both the hardware parameters, which depend on the specific design of the device, and the SM parameters, which instead depend on the energy-efficient algorithm used, the network topology, and the traffic variations over time. Our results show that (i) the changes in the operational temperature and the frequency of their variation are two crucial aspects to consider while designing a SM-based green strategy, and (ii) the impact of a certain SM-based strategy on the lifetime of network devices is not homogeneous (i. e., it can vary through the network)
Radio Resource Calendaring in Cloud-based Radio Access Networks
No full textBandwidth calendaring refers to the possibility of shifting some bulk data transfers, typically of large size with less stringent real-time constraint, to the moments when the network is less congested. In this paper, we exploit calendering in radio resource allocation in Cloud-based Radio Access Networks (C-RANs), where calendaring naturally fits the centralized C-RAN architecture. We formulate the optimal calendaring problem using Integer Linear Programming (ILP), taking into account specific constraints of users’ connections and the C-RAN operator. Given the complexity of the optimization problem, we devise effective heuristics producing close-to- optimum solutions in polynomial time. Extensive simulations, conducted in representative network scenarios, demonstrate the effectiveness of our proposed approach in improving the performance of C-RAN scheduling
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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
- …
