Search results for " Architecture"
showing 10 items of 2595 documents
Interference Estimation in IEEE 802.11 Networks
2010
This article describes a technique for distinguishing and quantifying medium access control (MAC) and physical layer (PHY) interference in error-prone 802.11 networks. This technique, is fully distributed, allowing each station to estimate interference individually. The estimator is based on an extended Kalman filter coupled to a mechanism for revealing abrupt changes in state. The network state is a vector of two components, representing PHY interference, expressed in terms of channel-error rate, and MAC interference. Two distinct state models are considered. When PHY interference can be assumed to be constant for all stations, network congestion is expressed by the number of competing ter…
An Integrated Framework for Meta Modeling
2006
Meta modeling is an essential means to systematize, formalize, standardize, integrate, analyze and compare models, techniques, methods and tools. Numerous fields, such as databases, software engineering, software architectures, semantic web, computer-aided tools and method engineering, have benefited from it. The importance of meta modeling is ever increasing along with the emergence of novel approaches, architectures, techniques and languages based on UML and MDA. This paper presents a framework to integrate and compare divergent conceptions of meta modeling in databases, software engineering, and information systems development. The framework is applied to analyze and compare conceptions …
An Empirical Set of Metrics for Embedded Systems Testing
2018
Editor’s note: Selecting the right platform for an embedded system is a challenging task, because there are no systematic methodologies for comprehensive evaluation and comparison of competing alternatives. This article partially addresses this problem by formulating a set of relevant metrics and an evaluation methodology. By applying their concepts to the evaluation of two alternative platforms, the Raspberry Pi3 and the Intel Edison boards, the authors demonstrate the utility of their approach and show under which objectives one is preferable over the other. —Axel Jantsch, TU Wien
A Novel Amplify-and-Forward Relay Channel Model for Mobile-to-Mobile Fading Channels under Line-of-Sight Conditions
2021
In this chapter, we have proposed a new flexible M2M amplify-and-forward relay fading channel model under LOS propagation conditions. The novelty in the model is that we have considered the LOS components in both transmission links, i.e., the direct link between the source mobile station and the destination mobile station as well as the link via the mobile relay. By analogy with multiple scattering radio propagation channels, we have developed the MLSS fading channel as a second-order scattering channel, where the received signal comprises the single and double scattered components. Furthermore, the flexibility of the MLSS fading channel model comes from the fact that it can be reduced to d…
An enhanced TCP congestion avoidance scheme and its performance evaluation in high speed satellite networks
2009
©2009 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE." Article also available from publisher: http://dx.doi.org/10.1109/ICICS.2009.5397691 High speed satellite communication networks are emerging as part of the future global wireless communication systems. However, existing transmission control protocols for satellite networks do not provide satisfactory performance over high speed satellite links due to their ine…
Cooperative Medium Access Control in Wireless Networks: The Two-Hop Case
2009
Cooperative communication has been recently proposed as a powerful means to improve network performance in wireless networks. However, most existing work focuses solely on one-hop source-destination cooperation. In this paper, we propose a novel cooperative MAC mechanism that is specially designed for two-hop cooperation communications where the source node and the destination node cannot hear each other directly. In this case, cooperative communication is operated in a two-hop manner and transmit-diversity is achieved by the reception of the same data packet forwarded through multiple relays towards a single destination. The proposed scheme employs an efficient relay selection algorithm to…
An optimal energy efficient cooperative retransmission MAC scheme in wireless networks
2011
While the benefits of cooperative diversity have been well studied in the literature, cooperative MAC protocol design has also attracted much attention recently. In the single-relay Cooperative Automatic Repeat reQuest (C-ARQ) protocol, the best relay node is selected in a distributed manner by relays using different backoff time before packet retransmission. However, this relay selection scheme does not work efficiently in a dense network scenario, due to possible high collision probability among different contending relays. In this paper, we propose an optimized relay selection scheme to maximize system energy efficiency by reducing collision probability. The energy efficiency performance…
On marrying ontological and metamodeling technical spaces
2007
In software engineering, the use of models and metamodeling approaches (e.g., MDA with MOF/UML) for purposes such as software design or software validation is an established practice. Ontologies constitute domain models formalized using expressive logic languages for class definitions and rules. Hence, when seen from an abstract point of view, the two paradigms and their various technological spaces seem closely related. However, in the state-of-the-art research and practice the two technologies are just beginning to converge and the relationship between the two is still under exploration. In this paper, we give an outline of current ontology technologies, such as the Semantic Web standards…
A study on the statistical properties of double hoyt fading channels
2009
This paper deals with a study on the statistical properties of narrowband amplify-and-forward relay fading channels for Hoyt multipath propagation environments. We consider the basic radio link topology, where only one fixed relay station is used for the amplification. In this case, the envelope of the signal received over the overall multipath channel is modeled by the so-called double Hoyt fading process. Considering this multipath propagation channel model, analytical expressions for the first and second order statistics are provided. Specifically, the mean value, variance, probability density function (PDF), level-crossing rate (LCR), and average duration of fades (ADF) of double Hoyt p…
Achieving agility and quality in product development -an empirical study of hardware startups
2020
Context: Startups aim at scaling their business, often by developing innovative products with limited human and financial resources. The development of software products in the startup context is known as opportunistic, agility-driven, and with high tolerance for technical debt. The special context of hardware startups calls for a better understanding of state-of-the-practice of hardware startups’ activities. Objective: This study aimed to identify whether and how startups can achieve product quality while maintaining focus on agility. Method: We conducted an exploratory study with 13 hardware startups, collecting data through semi-structured interviews and analysis of documentation. We pro…