A semantic end-to-end QoS model for dynamic service oriented environments

International audienceIn Service Oriented Computing (SOC), modeling the Quality of Service (QoS) is a cornerstone for providing services with quality guarantees. As the technological advances and wide adoption of handheld devices (e.g., PDA and smartphones) and wireless networks (e.g., UMTS, WiFi and Bluetooth) have made service environments more dynamic, QoS models must change accordingly. In this paper, we present a QoS model that provides the approporiate ground for QoS engineering in SOC. Our model focuses on emerging QoS features related to the dynamics of service environments such as user mobility and context awareness of application services. It also considers QoS on an end-to-end basis by covering QoS features of all the resources and actors involved in service provisioning (e.g., network, device, service, end-user). Our model represents QoS with rich semantic information and makes use of the Web Service Quality Model (WSQM) proposed by OASIS

Multi-Objective Service Composition in Ubiquitous Environments with Service Dependencies

International audienceService composition is a widely used method in ubiquitous computing that enables accomplishing complex tasks required by users based on elementary (hardware and software) services available in ubiquitous environments. To ensure that users experience the best Quality of Service (QoS) with respect to their quality needs, service composition has to be QoS-aware. Establishing QoS-aware service compositions entails efficient service selection taking into account the QoS requirements of users. A challenging issue towards this purpose is to consider service selection under global QoS requirements (i.e., requirements imposed by the user on the whole task), which is of high computational cost. This challenge is even more relevant when we consider the dynamics, limited computational resources and timeliness constraints of ubiquitous environments. To cope with the above challenge, we present QASSA, an efficient service selection algorithm that provides the appropriate ground for QoS-aware service composition in ubiquitous environments. QASSA formulates service selection under global QoS requirements as a set-based optimisation problem, and solves this problem by combining local and global selection techniques. In particular, it introduces a novel way of using clustering techniques to enable fine-grained management of trade-offs between QoS objectives. QASSA further considers: (i) dependencies between services, (ii) adaptation at run-time, and (iii) both centralised and distributed design fashions. Results of experimental studies performed using real QoS data are presented to illustrate the timeliness and optimality of QASSA

QoS-aware Service-Oriented Middleware for Pervasive Environments

Pervasive computing is an intuitive evolution of computing paradigms driven by the wide adoption of mobile devices and wireless networks. It introduces a novel way to support users in their everyday life based on open and dynamic environments populated with unobtrusive services able to perform user tasks on the fly. Nevertheless, supporting user tasks from a functional point of view is not enough to gain the user's satisfaction. Users instead require that their tasks meet a certain Quality of Service (QoS) level. QoS is indeed an inherent and primary requisite of users going along with their required tasks. In the context of pervasive environments, fulfilling user tasks while delivering satisfactory QoS brings about several challenges that are mainly due to the openness, dynamics, and limited underlying resources of these environments. These challenges are mainly about (i) the lack of common QoS understanding among users and service providers, (ii) determining and integra- ting, on the fly, the services available in the environment and able to fulfill the functional and QoS requirements of users, and (iii) adapting the provided services at run-time to cope with QoS fluctuations and ensure meeting user requirements. To cope with the aforementioned issues, we opt for a middleware-based solution. Middle- ware represents indeed the appropriate software system to deal with common concerns of user applications such as QoS. In particular, we opt for a specific kind of middleware, viz., Ser- vice Oriented Middleware (SOM). SOM can leverage middleware technologies and the Service Oriented Computing (SOC) paradigm to enable pervasive environments as dynamic service en- vironments. Particularly, SOM can provide middleware services that allow for supporting QoS of user applications offered by pervasive environments. This thesis presents a QoS-aware service-oriented middleware for pervasive environments. The main contributions of this middleware are : (1) a semantic end-to-end QoS model that enables shared understanding of QoS in pervasive environments, (2) an efficient QoS-aware service composition approach allowing to build service compositions able to fulfill the user functional and QoS requirements, and (3) a QoS-driven adaptation approach to cope with QoS fluctuations during the execution of service compositions. The proposed contributions are implemented within a middleware platform called QASOM and their efficiency is validated based on experimental results

EraRFID: Reliable RFID systems using erasure coding.

International audienceCurrent RFID systems are not utterly reliable as they may fail to read all the tags present in their RF field of view, particularly when dealing with bulk tag reading in messy situations. To enable reliable tag inventories, we put forward the concept of RFID tag grouping, i.e., logically coupling tags thus forming a consistent group. Tag grouping allows to identify missing tags by reading only a subset of the group, with no need to external information systems. In this paper, we introduce EraRFID, an erasure coding approach for RFID tag grouping. EraRFID models RFID tag inventorying as an erasure coding problem, and solves this problem using the well-known Reed Solomon (RS) codes. The efficiency of EraRFID in terms of timeliness and storage overhead is validated through experimental studies

Set-based Bi-level Optimisation for QoS-aware Service Composition in Ubiquitous Environments

International audienceService composition is a widely used method in ubiquitous computing that enables accomplishing complex tasks required by users based on elementary (hardware and software) services available in ubiquitous environments. To ensure that users experience the best Quality of Service (QoS) with respect to their quality needs, service composition has to be QoS-aware. Establishing QoS-aware service compositions entails efficient service selection taking into account the QoS requirements of users. A challenging issue towards this purpose is to consider service selection under global QoS requirements (i.e., requirements imposed by the user on the whole task), which is of high computational cost. This challenge is even more relevant when we consider the dynamics, limited computational resources and timeliness constraints of ubiquitous environments. To cope with the above challenge, in this paper we present QASSA, an efficient service selection algorithm that provides the appropriate ground for QoS-aware service composition in ubiquitous environments. The contribution of QASSA is threefold. First, it formulates service selection under global QoS requirements as a set-based optimisation problem, benefiting from recent proposals in the domain of multi-objective optimisation. Second, QASSA resolves this problem in an efficient way using clustering techniques, namely the K-Means algorithm. Third, QASSA is devised in two versions, viz., centralised and distributed versions, so that it can be executed on top of centralised and decentralised infrastructures in ubiquitous environments. Results of experimental studies are presented to illustrate the timeliness and optimality of QASSA

Diversity contribution of a versatile UHF RFID antenna system in portal applications

International audienceA versatile ultra high frequency radiofrequency identification (UHF RFID) antenna system is proposed. Spatial, polarization and radiation pattern diversity is demonstrated with a very reduced number of components. The diversity contribution of such an antenna is then characterized in terms of radio coverage in a RFID portal environment. Radio coverage in complex environment is greatly improved compared to the classical geometry