Carlos García-Rubio

PDP and GSDL: a new service discovery middleware to support spontaneous interactions in pervasive systems

In pervasive computing environments, mobile devices communicate via wireless links without requiring any fixed infrastructure. These devices must be able to discover and share services dynamically. In this paper, we propose a new service discovery middleware specifically designed for this kind of environments. This middleware is composed of a service discovery protocol, Pervasive Discovery Protocol (PDP), and a service description language, Generic Service Description Language (GSDL). PDP is a fully distributed protocol that merges characteristics of both pull and push solutions; it reduces power consumption of the most limited devices. GSDL is an XML based markup language that uses a hierarchical service description designed taking into account the specific requirements of pervasive environments.

PDP: a lightweight discovery protocol for local-scope interactions in wireless ad hoc networks

In ad hoc networks, mobile devices communicate via wireless links without any fixed infrastructure. These devices must be able to discover and share services dynamically. In this paper, we propose a new service discovery protocol specifically designed for this kind of networks, the pervasive discovery protocol. PDP is a fully distributed protocol that merges characteristics of both pull and push solutions. Devices maintain a list of services previously announced by others, that is partly included in the queries, and is also used for third party answers. PDP reduces power consumption of the most limited devices by prioritising the replies of the less limited ones, allowing the others to abort their answers. Simulation results are presented, showing the performance of PDP and comparing it with other service discovery protocols.

Building service-oriented Smart Infrastructures over Wireless Ad Hoc Sensor Networks: A middleware perspective

The increase in physical resources for the next-generation of embedded computing devices, as well as in the efforts carried out by the scientific and research communities, is paving the way for Smart Infrastructures based on Wireless Sensor Networks. In such manner, not only open and formally defined Service-Oriented Frameworks are required, but also efficient middleware technologies that ease the development of new sensor-based services. From the cornerstone analysis of pervasive computing principles applied to Smart Spaces creation, this article presents the @mSMS (micro Subscription Management System) middleware. This approach specifies and develops the notion of virtual sensor services created for Smart Environments over sensor networks from tiny in-network services based on agent technology. In the framework of the @mSWN European Research Project, this architecture has been validated in a Smart Hospital real-world scenario using a healthcare virtual sensor service. Considering such purpose, medical status monitoring, location tracking and perimeter surveillance agent-based services have been developed. This study is concluded by a comparative analysis of the system considering memory overhead, packet delivery ratio, average end-to-end delay and battery lifetime as evaluation metrics. The results show a lightweight middleware implementation with good overall system and network performance.

Performance Evaluation of LZ-Based Location Prediction Algorithms in Cellular Networks

In mobile phones, it is useful to know the most probable next location to make decisions about future actions. In this letter we compare three LZ based prediction algorithms. The originality of our work is that we make it in a cellular network, we separate the algorithms into two independent phases (tree updating and probability calculation), we have included Active LeZi in the study, and we evaluate hit rate and resource consumption, including processing time.

A Trust-based Middleware for Providing Security to Ad-Hoc Peer-to-Peer Applications

Trust has emerged as an important facet of inter-domain relationships. Trust management in fixed networks is not functional in ad hoc P2P networks, because these require an autonomous, user-centric and non-static trust management. The trust model is the basis of any security infrastructure. In this paper, we propose a trust-based middleware for secure digital content sharing between pervasive devices. Such middleware allows to enhance security support of pervasive devices. Likewise, we propose a suitable and efficient secure file exchange protocol, WSFEP, for content sharing. Both middleware and file sharing application have been successfuly integrated and tested on PDAs.

Decoupling path failure detection from congestion control to improve SCTP failovers

SCTP handover is too slow to be useful as a mobility solution for most applications. With quicker handovers, SCTP will be an interesting solution to mobility. SCTP uses retransmissions as probes for path failure detection. Congestion control forces slow paced retransmissions but quick failovers need fast paced probes. Our solution is to stop using retransmissions as probes. Instead, we propose active path monitoring using unreliable heartbeats. Applications can tune this algorithm to meet their own requirements. We show data from a simple experiment in a real environment.

A Bandwidth-Efficient Service for Local Information Dissemination in Sparse to Dense Roadways

Thanks to the research on Vehicular Ad Hoc Networks (VANETs), we will be able to deploy applications on roadways that will contribute to energy efficiency through a better planning of long trips. With this goal in mind, we have designed a gas/charging station advertising system, which takes advantage of the broadcast nature of the network. We have found that reducing the number of total sent packets is important, as it allows for a better use of the available bandwidth. We have designed improvements for a distance-based flooding scheme, so that it can support the advertising application with good results in sparse to dense roadway scenarios.

Impact of location history collection schemes on observed human mobility features

Human mobility knowledge is key for urban planning or mobility models design. Therefore, estimating reliable mobility parameters is crucial to lay an unbiased foundation. However, most works estimating such features rely on datasets made up of the history of mobile network cells where the user is located when she makes active use of the network, known as Call Data Records (CDRs), or every time the her device connects to a new cell, without taking into account cell changes not caused by movement. Could we accurately characterize human mobility with such datasets? In this work we consider three approaches to collect network-based mobility data, propose three filtering techniques to delete cell changes not caused by movement and compare mobility features extracted from the traces collected with each approach. The analysis unveils the need for a filtering step to avoid important biases, and the negative impact that using CDRs may have in estimating mobility parameters.

Bandwidth efficient broadcasting in VANETs

Wireless communications amongst vehicles bring the opportunity for a wide range of applications, from safety aid to passenger entertainment. The necessity to broadcast information to several-hop neighbors is common to most of the potential application protocols. Broadcast protocols for VANETs based on diverse techniques have already been proposed. In this article, we compare basic broadcast schemes that are not dependent on neighbor knowledge using ns-2 - simple flooding, probabilistic, counter-based, distance-based and traffic-based broadcast. The objective is to obtain general directions for the design of a bandwidth efficient broadcast. Based on this comparison, we have selected distance-based flooding and proposed a scheme that is easy to adjust to the applications necessities.

MOFETA: a network architecture based on MObile FEmtocells to enhance cellular connectivity on trains

Nowadays the quality of the indoor coverage on trains is not enough to offer broadband services, mainly due to two factors: the high penetration losses caused by Faraday cage characteristics of the railcars and the high speeds reached. In this paper we aim to enhance the 3G indoor coverage on trains by setting up femtocells inside the railcars and establishing several wireless interfaces along the roof of the train. We design an architecture to connect the train to the fixed network in a transparent manner, so that the end users do not experience service disruptions during the journey. Finally, we deploy a testbed to evaluate the performance of the mobility management system based on test results.