1,720,993 research outputs found
Design methodologies and algorithms for survivable C-RAN
No full textIn centralized/cloud radio access networks (C-RANs), baseband units (BBUs) are decoupled from remote radio units (RRUs) and placed in BBU hotels. In this way baseband processing resources can be shared among RRUs, providing opportunities for radio coordination and cost/energy savings. However, the failure of a BBU hotel can affect a large number of RRUs creating severe outages in the radio segment. For this reason, the design of a resilient C-RAN is imperative. In this paper, an extension of the facility location problem (FLP) is proposed to find the placement of BBU hotels that guarantees survivability against single hotel failure while the delay is minimized. Different strategies are proposed based on heuristic and integer linear programming (ILP) to solve the survivable BBU location problem and optimizing the sharing of backup resources. The results compare the proposed methodologies in terms of the costs of the BBU placement by referring to different network topologies. The heuristic algorithm is shown to find solutions close to those obtained by the ILP, although evidencing different contributions that are suitably discussed
Centralized vs. distributed algorithms for resilient 5G access networks
No full textCloud radio access networks (C-RANs), relying on network function virtualization and software-defined networking (SDN), require a proper placement of baseband functionalities (BBUs) to reach full coverage of served areas and service continuity. In this context, network resources can be shared and orchestrated to meet the flexibility required by a dynamically evolving environment. Different methodologies, based on analytical formulation or heuristic algorithms, can be applied to achieve suitable trade-offs among cost components. This paper considers both centralized and distributed algorithms to obtain BBU hotel placement in C-RAN and compares their performance, scalability and adaptability to evolving scenarios. As expected, the results obtained with the distributed approach are sub-optimal, but very close, in most cases, to the optimal solutions obtained with a centralized algorithm based on integer linear programming. In addition to off-loading the SDN orchestrator, the distributed approach, differently from the centralized one, is shown to be able to cope with the evolution of the C-RAN topology with limited incremental changes in the original placement. The limits of the centralized approach in terms of scalability that the distributed approach is able to overcome are also evidenced
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Benefits of joint planning of small cells and fiber backhaul in 5G dense cellular networks
No full textBase station (BS) densification is increasingly adopted by mobile operators in order to support increasing traffic demand. However, a large number of BSs requires many backhaul connections, which may be very expensive. For this reason, provisioning high speed backhaul connections to BSs in a cost-effective way is challenging, and it is important to efficiently utilize an existing fixed network infrastructure if possible. This paper proposes two optimized infrastructure-aware planning strategies for small cells and fiber backhaul. The first strategy is referred to as joint design (JD) and is based on the joint cost minimization of small cells and fiber backhaul. The JD strategy is compared to a traditional design (TD) solution based on a two-step optimization approach. In the latter a cost-optimal small cells placement is identified first, then the corresponding minimum cost fiber backhaul deployment is determined accordingly. A comparison between these two approaches in dense 5G urban scenarios shows that the relative performance of JD and TD largely depends on the expected traffic demand and on the existing infrastructure. In dense urban areas with the average traffic levels expected for the year 2020 and beyond, JD returns up to 50% lower deployment cost in a greenfield scenario, and up to 70% lower deployment cost in a brownfield scenario. Only in areas with extremely high traffic demand (e.g., open-air festivals and stadiums) JD returns deployment costs very similar to TD
Performance and Cost of Dynamic Reliability: A 6G Industrial Environment Perspective
Full text linkThe use of robots in modern manufacturing facilities, where also human workers operate, offers substantial advantages, but also introduces safety hazards that need to be mitigated with all possible means. Ultra-reliable communication services offered by 5G mobile networks allow for automated remote control of the machines, thus enabling a new generation of network applications that can enforce safety procedures in a hyper-connected industrial environment. However, in the context of Human-Robot Collaboration scenarios very strict safety requirements must be satisfied, determining communication reliability levels to be guaranteed that go beyond the up to 10-5 capabilities of 5G ultra-reliable deployments. Moreover, in 5G the reliability is imposed as fixed requirement to be achieved at all times, which may lead to resource overprovisioning. Resource efficiency can be improved by dynamically adapting the target network reliability level based on the actual needs of the connected devices, still guaranteeing safe human-robot interactions. The idea of dynamic reliability applied to 6G industrial environments, introduced in our previous work, is further investigated in this paper by evaluating performance and costs of the approach, and by exploring how to leverage the knowledge of the specific nature of the task performed by robots cooperating with humans. The results of our study allow to quantify the resource gain that can be achieved with dynamic reliability compared to the solution currently offered by 5G systems, as well as the cost that must be factored in in terms of network signalling overhead
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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