46,997 research outputs found
Analysis of Network Clustering Algorithms and Cluster Quality Metrics at Scale
Notions of community quality underlie network clustering. While studies
surrounding network clustering are increasingly common, a precise understanding
of the realtionship between different cluster quality metrics is unknown. In
this paper, we examine the relationship between stand-alone cluster quality
metrics and information recovery metrics through a rigorous analysis of four
widely-used network clustering algorithms -- Louvain, Infomap, label
propagation, and smart local moving. We consider the stand-alone quality
metrics of modularity, conductance, and coverage, and we consider the
information recovery metrics of adjusted Rand score, normalized mutual
information, and a variant of normalized mutual information used in previous
work. Our study includes both synthetic graphs and empirical data sets of sizes
varying from 1,000 to 1,000,000 nodes.
We find significant differences among the results of the different cluster
quality metrics. For example, clustering algorithms can return a value of 0.4
out of 1 on modularity but score 0 out of 1 on information recovery. We find
conductance, though imperfect, to be the stand-alone quality metric that best
indicates performance on information recovery metrics. Our study shows that the
variant of normalized mutual information used in previous work cannot be
assumed to differ only slightly from traditional normalized mutual information.
Smart local moving is the best performing algorithm in our study, but
discrepancies between cluster evaluation metrics prevent us from declaring it
absolutely superior. Louvain performed better than Infomap in nearly all the
tests in our study, contradicting the results of previous work in which Infomap
was superior to Louvain. We find that although label propagation performs
poorly when clusters are less clearly defined, it scales efficiently and
accurately to large graphs with well-defined clusters
Considerations about multistep community detection
The problem and implications of community detection in networks have raised a
huge attention, for its important applications in both natural and social
sciences. A number of algorithms has been developed to solve this problem,
addressing either speed optimization or the quality of the partitions
calculated. In this paper we propose a multi-step procedure bridging the
fastest, but less accurate algorithms (coarse clustering), with the slowest,
most effective ones (refinement). By adopting heuristic ranking of the nodes,
and classifying a fraction of them as `critical', a refinement step can be
restricted to this subset of the network, thus saving computational time.
Preliminary numerical results are discussed, showing improvement of the final
partition.Comment: 12 page
Machine Learning at the Edge: A Data-Driven Architecture with Applications to 5G Cellular Networks
The fifth generation of cellular networks (5G) will rely on edge cloud
deployments to satisfy the ultra-low latency demand of future applications. In
this paper, we argue that such deployments can also be used to enable advanced
data-driven and Machine Learning (ML) applications in mobile networks. We
propose an edge-controller-based architecture for cellular networks and
evaluate its performance with real data from hundreds of base stations of a
major U.S. operator. In this regard, we will provide insights on how to
dynamically cluster and associate base stations and controllers, according to
the global mobility patterns of the users. Then, we will describe how the
controllers can be used to run ML algorithms to predict the number of users in
each base station, and a use case in which these predictions are exploited by a
higher-layer application to route vehicular traffic according to network Key
Performance Indicators (KPIs). We show that the prediction accuracy improves
when based on machine learning algorithms that rely on the controllers' view
and, consequently, on the spatial correlation introduced by the user mobility,
with respect to when the prediction is based only on the local data of each
single base station.Comment: 15 pages, 10 figures, 5 tables. IEEE Transactions on Mobile Computin
Development of Computer Science Disciplines - A Social Network Analysis Approach
In contrast to many other scientific disciplines, computer science considers
conference publications. Conferences have the advantage of providing fast
publication of papers and of bringing researchers together to present and
discuss the paper with peers. Previous work on knowledge mapping focused on the
map of all sciences or a particular domain based on ISI published JCR (Journal
Citation Report). Although this data covers most of important journals, it
lacks computer science conference and workshop proceedings. That results in an
imprecise and incomplete analysis of the computer science knowledge. This paper
presents an analysis on the computer science knowledge network constructed from
all types of publications, aiming at providing a complete view of computer
science research. Based on the combination of two important digital libraries
(DBLP and CiteSeerX), we study the knowledge network created at
journal/conference level using citation linkage, to identify the development of
sub-disciplines. We investigate the collaborative and citation behavior of
journals/conferences by analyzing the properties of their co-authorship and
citation subgraphs. The paper draws several important conclusions. First,
conferences constitute social structures that shape the computer science
knowledge. Second, computer science is becoming more interdisciplinary. Third,
experts are the key success factor for sustainability of journals/conferences
Energy Efficiency and Quality of Services in Virtualized Cloud Radio Access Network
Cloud Radio Access Network (C-RAN) is being widely studied for soft and green fifth generation of Long Term Evolution - Advanced (LTE-A). The recent technology advancement in network virtualization function (NFV) and software defined radio (SDR) has enabled virtualization of Baseband Units (BBU) and sharing of underlying general purpose processing (GPP) infrastructure. Also, new innovations in optical transport network (OTN) such as Dark Fiber provides low latency and high bandwidth channels that can support C-RAN for more than forty-kilometer radius. All these advancements make C-RAN feasible and practical. Several virtualization strategies and architectures are proposed for C-RAN and it has been established that C-RAN offers higher energy efficiency and better resource utilization than the current decentralized radio access network (D-RAN). This project studies proposed resource utilization strategy and device a method to calculate power utilization. Then proposes and analyzes a new resource management and virtual BBU placement strategy for C-RAN based on demand prediction and inter-BBU communication load. The new approach is compared with existing state of art strategies with same input scenarios and load. The trade-offs between energy efficiency and quality of services is discussed. The project concludes with comparison between different strategies based on complexity of the system, performance in terms of service availability and optimization efficiency in different scenarios
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