Dolors Royo

A communication infrastructure to ease the development of mobile collaborative applications

Mobile workers doing loosely coupled activities typically perform on demand collaboration in the physical workplace. Communication services available in such work scenarios are uncertain, therefore mobile collaborative applications supporting those activities must provide ad hoc communication mechanisms in order to use each cooperation opportunity. Typically, the complexity of implementing such mobile ad hoc communication mechanisms becomes a challenge that jeopardizes the development of mobile collaborative solutions. This article presents a communication infrastructure named HLMP API dealing with that challenge. HLMP API intends to ease the development of such applications through the reuse of communication services. The infrastructure is an application programming interface that implements the HLMP routing protocol and also some awareness mechanisms that are required for mobile loosely coupled work. Developers using this infrastructure do not have to perform low-level programming.

Decentralized vs. centralized economic coordination of resource allocation in grids

Application layer networks are software architectures that allow the provisioning of services requiring a huge amount of resources by connecting large numbers of individual computers, like in Grid or Peer-to-Peer computing. Controlling the resource allocation in those networks is nearly impossible using a centralized arbitrator. The network simulation project CATNET will evaluate a decentralized mechanism for resource allocation, which is based on the economic paradigm of the Catallaxy, against a centralized mechanism using an arbitrator object. In both versions, software agents buy and sell network services and resources to and from each other. The economic model is based on self-interested maximization of utility and self-interested cooperation between agents. This article describes the setup of money and message flows both for centralized and decentralized coordination in comparison.

Building real-world ad-hoc networks to support mobile collaborative applications: lessons learned

Mobile collaboration is required in several work scenarios, i.e. education, healthcare, business and disaster relief. The features and capabilities of the communication infrastructure used by mobile collaborative applications will influence the type of coordination and collaboration that can be supported in real work scenarios. Developers of these applications are typically unaware of the constraints the communication infrastructure imposes on the collaborative system. Therefore, this paper presents an experimental study of how ad-hoc networks can effectively support mobile collaborative work. The article analyzes several networking issues and it determines how they influence the collaborative work. The paper also presents the lessons learned and it provides recommendations to deal with the networking issues intrinsic to adhoc networks.

ULabGrid, an Infrastructure to Develop Distant Laboratories for Undergrad Students over a Grid

There has been a lot of discussion and study in the recent past about how distance learning could be improved using emerging technologies. Collaborative tools based on the web/internet infrastructure such as e-mail, discussion groups, video/audio conferencing and virtual campuses have been proposed and implemented in many areas of distance learning. We had proposed [3] ULabGrid as a new architecture that enables educators to design collaborative, distant laboratories for undergraduate students using the Grid infrastructure. We describe here some of the changes we have made to the proposed architecture and the prototype that is being developed and present the results of our efforts to date.

Sharing hardware resources in heterogeneous computer-supported collaboration scenarios

There currently are many mobile computing devices with various properties and capabilities. These devices may need to collaborate among them to allow nomad workers to perform a common activity. Unfortunately software developers in charge of creating infrastructures or applications allowing these devices to cooperate among them, do not count with clear guidelines to design such software components; particularly when these components must work in a scenario involving heterogeneous devices. This paper presents a study that tries to understand how to address collaboration among heterogeneous mobile devices, by exploring several variables affecting the process. In particular, this study explores various strategies to borrow CPU slots from peer mobile computing devices and return the favor back later on. The study outcomes indicate there is a short list of computing and network variables affecting the collaboration capability of the mobile devices. These findings have been verified using data mining techniques. Based on these findings and the lessons learned, the article presents a simulation method of computing scenarios that can help developers to determine which computing configuration would be suitable to be used in each particular work scenario. Software designers can take advantage of this simulation method and the design guidelines reported in this paper in order to develop applications able to work appropriately in heterogeneous computing scenarios.

HLMP API: A software library to support the development of mobile collaborative applications

Mobile collaborative applications are usually deployed in work scenarios where the existence of fixed communication infrastructure is hard to predict. For that reason, these applications use Mobile Ad hoc Networks (MANETs) to support communication between mobile users. The complexity involved in such communication infrastructures make that developers avoid developing software for mobile work scenarios. However, it is possible to provide a reusable abstraction of such communication mechanisms, in order to avoid that developers have to deal with low-level programming. This article presents HLMP API, which is an application programming interface that provides access to a HLMP implementation. This API is organized as a fully distributed mobile communication infrastructure, able to run on MANETs. This infrastructure provides an important set of services, which are required to support mobile collaboration. The reuse of these services allows developers to reduce the complexity, times and cost of these development projects.

Group Prediction in Collaborative Learning

We propose an approach for predicting group formations, to address the problem of automating the incorporation of group awareness into CSCL applications. Contextual information can enable the construction of applications that effectively assist the group members to automatically communicate in synchronous and collocated collaborative learning activities. We used data traces collected from the study of students’ behavior to train and test an intelligent system. Results have shown that context-information can be effectively used as a basis for a middleware for a dynamic group management. Inferring group membership is technically viable and can be used in real world settings.

OLSRp: Predicting Control Information to Achieve Scalability in OLSR Ad Hoc Networks

Scalability is a key design challenge that routing protocols for ad hoc networks must properly address to maintain the network performance when the number of nodes increases. We focus on this issue by reducing the amount of control information messages that a link state proactive routing algorithm introduces to the network. Our proposal is based on the observation that a high percentage of those messages is always the same. Therefore, we introduce a new mechanism that can predict the control messages that nodes need for building an accurate map of the network topology so they can avoid resending the same messages. This prediction mechanism, applied to OLSR protocol, could be used to reduce the number of messages transmitted through the network and to save computational processing and energy consumption. Our proposal is independent of the OLSR configuration parameters and it can dynamically self-adapt to network changes.

Implementing the one-sided Jacobi method on a 2D/3D mesh multicomputer

Abstract The paper discusses the implementation of a parallel algorithm to compute the eigenvalues and eigenvectors of a real symmetric matrix on a mesh multicomputer. The algorithm uses the one-sided Jacobi method and a two-dimensional organization of the nodes. It is aimed at reducing the communication cost incurred by one-dimensional algorithms found in the literature. The performance of the proposed algorithm on a squared 2D/3D mesh multicomputer is assessed through simple analytical models of execution time. The models show that the performance improvement over one-dimensional algorithms can be very noticeable, specially for a large number of nodes.

Low Communication Overhead Jacobi Algorithms for Eigenvalues Computation on Hypercubes

This paper presents some novel algorithms to implement the Jacobi method in hypercube multicomputers. The algorithms are based on the one-sided Jacobi method and use new Jacobi orderings, which are one of the contributions of this paper. The second contribution of this paper is the use of a systematic algorithm transformation, which is referred to as communication pipelining, and is aimed at reducing the communication overhead by exploiting parallelism in the communication operations. The proposed schemes are evaluated by means of analytical models and compared with previous proposals. The results show a significant reduction in the communication overhead, which in some cases can be by a factor almost as great as the number of dimensions of the hypercube.