Search results for "Computer network"

Applying Real-Time Dynamic Scaffolding Techniques during Tutoring Sessions Using Intelligent Tutoring Systems

2022

An intelligent tutoring system (ITS) is a computer system or software application that is built to replicate human tutors by supporting the theory of “learning by doing.” Even though ITSs have been proven to be successful in academic studies, they still have not found large adoption by the industry due to the complexities of building such systems due to the high technical expertise and domain knowledge requirements. Attempts have been made to build authoring tools that can provide assistance in building tutoring systems; however, most of these tools are targeted toward authors that have considerable programming experience. This research proposes an authoring tool for ITS, which is targeted …

Performance Study of Non-beaconed and Beacon-Enabled Modes in IEEE 802.15.4 under Bluetooth Interference

2008

The IEEE 802.15.4 protocol is a flexible technology with great potential for wireless sensor networks applications. The standard distinguishes two network modes; beacon-enabled and nonbeacon-enabled. In this paper, the performance study of beaconed and non-beaconed modes of IEEE 802.15.4 is evaluated using on site PER measurements. The tests are carryout in an urban outdoor environment with commercial available equipment. Likewise, the impact of Bluetooth interference over IEEE 802.15.4 modes is evaluated. The results show that Bluetooth interference and the mode selected have effects over the PER. Furthermore, for distances between 3 to 10 meters the PER doesn't show significance distance …

An Experimental Testbed and Methodology for Characterizing IEEE 802.11 Network Cards

2006

It has been observed that IEEE 802.11 commercial cards produced by different vendors show a different behavior in terms of perceived throughput or access delay. Performance differences are evident both when the cards contend alone to the channel, and when heterogeneous cards contend together. Since the performance misalignment does not disappear by averaging the environmental factors (such as propagation conditions, laptop models, traffic generators, etc), it is evident that the well known throughput-fairness property of the DCF protocol is not guaranteed in actual networks. In this paper we propose a methodological approach devised to experimentally characterize the IEEE 802.11 commercial …

Touchless gestural interfaces for networked public displays

2015

In the near future, we can easily imagine a significant increment in diffusion of networked public displays, as well as novel interaction modalities used in their applications. In the following, we present two of the main challenges related to networked displays we are dealing with, with a particular focus on touchless gestural interfaces: overcoming interaction blindness (i.e. enable users to immediately guess the interactivity of the display, and the gestural nature of it) and performing evaluations in-the-wild (i.e. outside any controlled environment).

A Newcomer's Guide to EICS, the Engineering Interactive Computing Systems Community

2019

[EN] Welcome to EICS, the Engineering Interactive Computing Systems community, PACMHCI/EICS journal, and annual conference! In this short article, we introduce newcomers to the field and to our community with an overview of what EICS is and how it positions with respect to other venues in Human-Computer Interaction, such as CHI, UIST, and IUI, highlighting its legacy and paying homage to past scientific events from which EICS emerged. We also take this opportunity to enumerate and exemplify scientific contributions to the field of Engineering Interactive Computing Systems, which we hope to guide researchers and practitioners towards making their future PACMHCI/EICS submissions successful an…

2020

The growth of cloud-based services is mainly supported by the core networking infrastructures of large-scale data centers, while the scalability of these services is influenced by the performance and dependability characteristics of data centers. Hence, the data center network must be agile and reconfigurable in order to respond quickly to the ever-changing application demands and service requirements. The network must also be able to interconnect the big number of nodes, and provide an efficient and fault-tolerant routing service to upper-layer applications. In response to these challenges, the research community began exploring novel interconnect topologies, namely: Flecube, DCell, Ficonn…

Cost-Effective Congestion Management for Interconnection Networks Using Distributed Deterministic Routing

2010

The Interconnection networks are essential elements in current computing systems. For this reason, achieving the best network performance, even in congestion situations, has been a primary goal in recent years. In that sense, there exist several techniques focused on eliminating the main negative effect of congestion: the Head of Line (HOL) blocking. One of the most successful HOL blocking elimination techniques is RECN, which can be applied in source routing networks. FBICM follows the same approach as RECN, but it has been developed for distributed deterministic routing networks. Although FBICM effectively eliminates HOL blocking, it requires too much resources to be implemented. In this …

Efficient Switches with QoS Support for Clusters

2007

Current interconnect standards providing hardware support for quality of service (QoS) consider up to 16 virtual channels (VCs) for this purpose. However, most implementations do not offer so many VCs because they increase the complexity of the switch and the scheduling delays. We have shown that this number of VCs can be significantly reduced, because it is enough to use two VCs for QoS purposes at each switch port. In this paper, we cover the weaknesses of that proposal and, not only we reduce VCs, but we also improve performance due to the flexibility assigning buffer memory.

On the development of a communication-aware task mapping technique

2004

Clusters have become a very cost-effective platform for high-performance computing. In these systems, although currently existing networks actually provide enough bandwidth for the existing applications and workstations, the trend is towards the interconnection network becoming the system bottleneck. Therefore, in the future, scheduling strategies will have to take into account the communication requirements of the applications and the communication bandwidth that the network can offer. One of the key issues in these strategies is the task mapping technique used when the network becomes the system bottleneck.In this paper, we propose a communication-aware mapping technique that tries to mat…

Secondary users selection and sparse narrow-band interference mitigation in cognitive radio networks

2018

Spectrum scarcity is a critical problem that may reduce the effectiveness of wireless technologies and services. To address this problem, different spectrum management techniques have been proposed in the literature such as overlay cognitive radio (CR) where the unlicensed users can share the same spectrum with the licensed users. The main challenges in overlay CR networks are the identification and detection of the Primary User (PU) signals in a multi-source narrow-band interference (NBI) scenario. Therefore, in this paper, we investigate the performance of an orthogonal frequency division multiplexing (OFDM) overlay CR network with Secondary Users (SUs) and subcarriers selection schemes. …