3,258 research outputs found
A Message Passing Strategy for Decentralized Connectivity Maintenance in Agent Removal
In a multi-agent system, agents coordinate to achieve global tasks through
local communications. Coordination usually requires sufficient information
flow, which is usually depicted by the connectivity of the communication
network. In a networked system, removal of some agents may cause a
disconnection. In order to maintain connectivity in agent removal, one can
design a robust network topology that tolerates a finite number of agent
losses, and/or develop a control strategy that recovers connectivity. This
paper proposes a decentralized control scheme based on a sequence of
replacements, each of which occurs between an agent and one of its immediate
neighbors. The replacements always end with an agent, whose relocation does not
cause a disconnection. We show that such an agent can be reached by a local
rule utilizing only some local information available in agents' immediate
neighborhoods. As such, the proposed message passing strategy guarantees the
connectivity maintenance in arbitrary agent removal. Furthermore, we
significantly improve the optimality of the proposed scheme by incorporating
-criticality (i.e. the criticality of an agent in its
-neighborhood).Comment: 9 pages, 9 figure
A contrasting look at self-organization in the Internet and next-generation communication networks
This article examines contrasting notions of self-organization in the Internet and next-generation communication networks, by reviewing in some detail recent evidence regarding several of the more popular attempts to explain prominent features of Internet structure and behavior as "emergent phenomena." In these examples, what might appear to the nonexpert as "emergent self-organization" in the Internet actually results from well conceived (albeit perhaps ad hoc) design, with explanations that are mathematically rigorous, in agreement with engineering reality, and fully consistent with network measurements. These examples serve as concrete starting points from which networking researchers can assess whether or not explanations involving self-organization are relevant or appropriate in the context of next-generation communication networks, while also highlighting the main differences between approaches to self-organization that are rooted in engineering design vs. those inspired by statistical physics
The Project Scheduling Problem with Non-Deterministic Activities Duration: A Literature Review
Purpose: The goal of this article is to provide an extensive literature review of the models and solution procedures proposed by many researchers interested on the Project Scheduling Problem with nondeterministic activities duration. Design/methodology/approach: This paper presents an exhaustive literature review, identifying the existing models where the activities duration were taken as uncertain or random parameters. In order to get published articles since 1996, was employed the Scopus database. The articles were selected on the basis of reviews of abstracts, methodologies, and conclusions. The results were classified according to following characteristics: year of publication, mathematical representation of the activities duration, solution techniques applied, and type of problem solved. Findings: Genetic Algorithms (GA) was pointed out as the main solution technique employed by researchers, and the Resource-Constrained Project Scheduling Problem (RCPSP) as the most studied type of problem. On the other hand, the application of new solution techniques, and the possibility of incorporating traditional methods into new PSP variants was presented as research trends. Originality/value: This literature review contents not only a descriptive analysis of the published articles but also a statistical information section in order to examine the state of the research activity carried out in relation to the Project Scheduling Problem with non-deterministic activities duration.Peer Reviewe
Effectiveness of Reconfigurable Intelligent Surfaces to Enhance Connectivity in UAV Networks
Reconfigurable intelligent surfaces (RISs) are expected to make future 6G
networks more connected and resilient against node failures, due to their
ability to introduce controllable phase-shifts onto impinging electromagnetic
waves and impose link redundancy. Meanwhile, unmanned aerial vehicles (UAVs)
are prone to failure due to limited energy, random failures, or targeted
failures, which causes network disintegration that results in information
delivery loss. In this paper, we show that the integration between UAVs and
RISs for improving network connectivity is crucial. We utilize RISs to provide
path diversity and alternative connectivity options for information flow from
user equipments (UEs) to less critical UAVs by adding more links to the
network, thereby making the network more resilient and connected. To that end,
we first define the criticality of UAV nodes, which reflects the importance of
some nodes over other nodes. We then employ the algebraic connectivity metric,
which is adjusted by the reflected links of the RISs and their criticality
weights, to formulate the problem of maximizing the network connectivity. Such
problem is a computationally expensive combinatorial optimization. To tackle
this problem, we propose a relaxation method such that the discrete scheduling
constraint of the problem is relaxed and becomes continuous. Leveraging this,
we propose two efficient solutions, namely semi-definite programming (SDP)
optimization and perturbation heuristic, which both solve the problem in
polynomial time. For the perturbation heuristic, we derive the lower and upper
bounds of the algebraic connectivity obtained by adding new links to the
network. Finally, we corroborate the effectiveness of the proposed solutions
through extensive simulation experiments.Comment: 14 pages, 8 figures, journal paper. arXiv admin note: text overlap
with arXiv:2308.0467
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Combined Banzhaf & Diversity Index (CBDI) for critical node detection
Critical node discovery plays a vital role in assessing the vulnerability of a computer network to malicious attacks and failures and provides a useful tool with which one can greatly improve network security and reliability. In this paper, we propose a new metric to characterize the criticality of a node in an arbitrary computer network which we refer to as the Combined Banzhaf & Diversity Index (CBDI). The metric utilizes a diversity index which is based on the variability of a node׳s attributes relative to its neighbours and the Banzhaf power index which characterizes the degree of participation of a node in forming shortest paths. The Banzhaf power index is inspired from the theory of voting games in game theory. The proposed metric is evaluated using analysis and simulations. The criticality of nodes in a network is assessed based on the degradation in network performance achieved when these nodes are removed. We use several performance metrics to evaluate network performance including the algebraic connectivity which is a spectral metric characterizing the connectivity robustness of the network. Extensive simulations in a number of network topologies indicate that the proposed CBDI index chooses more critical nodes which, when removed, degrade network performance to a greater extent than if critical nodes based on other criticality metrics were removed
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