1,720,965 research outputs found
Computer Networks In Tactical And Disaster Recovery Environments
No full textTactical and Disaster Recovery Operations (TDR) are often conducted in degraded environments and supported by ad hoc mobile communication mechanisms based on radio and satellite technologies. These networks are much less stable and reliable than what's commonly behind enterprise and commercial internet applications. These custom networks are required because TDR operations are conducted in remote and unforgiving locations and must continue regardless of meteorological conditions. Furthermore, TDR operations are very dynamic, with nodes entering and exiting radio ranges further complicating the communication environment. These aspects create a communication environment afflicted by high latencies, low bandwidth, and non-negligible packet loss that violates several assumptions behind message dissemination mechanisms commonly used in civilian applications. Even so, the critical nature of TDR operations requires fast, predictable, and reliable communication mechanisms capable of exchanging messages. This fact calls for a case-by-case evaluation of available solutions to reckon if they can operate effectively or if it's necessary to implement custom solutions tailored for this specific use case. Another problematic characteristic of Networks used in TDR operations is that they present variable and unpredictable performance. This characteristic calls for the development of network-aware solutions capable of continuously monitoring the network, evaluating its status, and reconfiguring parameters to adapt them to new conditions and improve the use of network resources.
This thesis presents research on three major topics. The first two analyze the evolution of communication protocols for unicast and group communication. In particular, this thesis presents research on these systems to evaluate their applicability to degraded environments. The chapter on group communication also presents the ANGLOVA scenario, a sophisticated emulated network environment created in collaboration with the NATO Science and Technology Organization which can be used to perform tests in a realistic environment. The two chapters also present several experiments in which many modern protocols developed for tactical and consumer applications are evaluated and compared. Finally, this thesis presents the Smart Estimation of Network StatE Information (SENSEI) framework, a distributed system for passive monitoring and adaptation capable of harvesting network information, inferring the network state, and adapting the behavior of other components to improve the use of network resources. SENSEI implements several algorithms to control the information aggregation and distribution processes to minimize network footprint and increase the value of what is transmitted.
The research presented in this thesis was carried out in collaboration with several international groups and research institutes such as the Florida Institute for Human and Machine Cognition (IHMC), FL, USA, the NATO Science and Technology Organization (STO) IST-124 Research Task Group on "Heterogeneous Tactical Networks - Improving Connectivity and Network Efficiency", and the United States Army Research Laboratory (ARL), Adelphi, MD, USA.abstracten
RoamML: Distributed Machine Learning at the Tactical Edge
No full textMachine learning is an effective methodology for enabling real-time data-driven decision-making in tactical scenarios, but its application in such scenarios raises many challenges due to data volume, unpredictable connectivity, and infrastructural challenges in edge environments. Furthermore, the need to perform training operations on remote powerful computing nodes might not be suited for tactical edge networks that often lack high bandwidth links, thus causing critical delays in assessing relevant information for decision-making. To overcome these challenges and enable machine learning at the tactical edge, this paper presents RoamML, a novel distributed continual learning approach tailored explicitly for the tactical edge. Built upon the foundational principle that “moving the model is usually much cheaper than transferring extensive datasets”, RoamML seamlessly performs training operations by traversing network nodes, according to the data gravity concept. As RoamML encounters new data at each node, it continually trains on the encountered data to ensure that RoamML maintains an up-to-date and accurate model without transferring data to a centralized entity. Experimental results comparing RoamML with a baseline centralized machine learning solution show the potential of the proposed approach, which is capable of closely matching the accuracy of the baseline method
Learning to Sail Dynamic Networks: The MARLIN Reinforcement Learning Framework for Congestion Control in Tactical Environments
No full textConventional Congestion Control (CC) algorithms, such as TCP Cubic, struggle in tactical environments as they misinterpret packet loss and fluctuating network performance as congestion symptoms. Recent efforts, including our own MARLIN, have explored the use of Reinforcement Learning (RL) for CC, but they often fall short of generalization, particularly in competitive, unstable, and unforeseen scenarios. To address these challenges, this paper proposes an RL framework that leverages an accurate and parallelizable emulation environment to reenact the conditions of a tactical network. We also introduce refined RL formulation and performance evaluation methods tailored for agents operating in such intricate scenarios. We evaluate our RL learning framework by training a MARLIN agent in conditions replicating a bottleneck link transition between a Satellite Communication (SATCOM) and an UHF Wide Band (UHF) radio link. Finally, we compared its performance in file transfer tasks against Transmission Control Protocol (TCP) Cubic and the default strategy implemented in the Mockets tactical communication middleware. The results demonstrate that the MARLIN RL agent outperforms both TCP and Mockets under different perspectives and highlight the effectiveness of specialized RL solutions in optimizing CC for tactical network environments
Adaptive Information Dissemination Over Tactical Edge Networks
No full textTactical edge networks are characterized by continuously changing link quality and topologies. Given the absence of pre-deployed infrastructure, MANET networks are often deployed at the tactical edge. Depending on factors such as location, mobility, terrain, and adversarial activity, the network may experience varying rates of churn as well as partitioning. Hence, it is typically difficult to pre-configure and optimize any network protocol to perform well across the spectrum of conditions that may occur during operations. Instead, protocols need to be able to observe the network conditions and adapt their behavior on a continuous basis to provide the best possible performance under varying circumstances. This paper focuses on Information Dissemination over tactical edge networks and in particular uses the Anglova scenario for experimental evaluation of an initial framework for network adaptation
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
DDAM: Dynamic network condition detection and communication adaptation in Tactical Edge Networks
No full textTactical Edge Networks provide one of the most challenging communication environments. In order to cope with node mobility, constrained resources, and link unreliability, communication solutions designed for Tactical Edge Networks typically present highly configurable interfaces to be adaptable for various networking conditions. However, the extreme dynamicity and heterogeneity of tactical scenarios call for network-aware, adaptive communication systems that continuously re-tune their configuration parameters to match the ever-changing network conditions. This paper presents the Dynamic Detect and Adapt Mechanism (DDAM) of the Agile Communication Middleware, a distributed solution to perform network monitoring and communication adaptation specifically designed for Tactical Edge Networks. The present work focuses on two components of the DDAM: NetSensor, which provides efficient monitoring of the network status, and NetSupervisor, which is responsible for characterizing the network technology used to connect a pair of nodes in the network. The presented results show that our solution can accurately identify the technology used to establish links between nodes
A secure group communication approach for tactical network environments
No full textGroup communication protocols that utilize multicast or local broadcast transmissions are more efficient than point-to-point protocols when disseminating the same information to multiple recipients. This is particularly true for Situation Awareness information at the tactical edge, which is transmitted from each sender to all receivers. However, group communications protocols do not address requirements for strong security mechanisms. This paper describes a novel approach that has been developed to provide secure group communications specifically to support dismounted warfighters at the tactical edge. The protocol has been incorporated into the Agile Computing Middleware's Proactive Dissemination Service (DSPro) and supports a variety of requirements such as dynamic authorization and de-authorization of clients as well as disruption-tolerant group communications
Variations on the Author
Get PDF“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
Get PDFWe 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
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