Solidor research



A modular system environment for wireless networks



Françoise André, Frédéric Le Mouël , Erwan Saint Pol, Maria-Teresa Segarra


Recent technology advances on wireless networks and mobile computers have led to the rapid expansion of mobile computing. More and more users use their laptop or palmtop computer while on the move. The characteristics of these mobile environments are very different from those of traditional ones. Indeed, due to radio propagation characteristics, wireless links are significantly error prone and suffer from poor bandwidth compared to wired ones. Moreover, bandwidth can greatly vary from network to network or even within the same network while the computer moves. On the other hand, mobile devices are very different from desktop computers. First of all, weigth limitations required to ease devices portability lead to a resources limitation that does not exist on desktop computers. Second, mobile computers use a limited energy supply which consumption depends on the applications utilization of available resources. Finally, resources can be dynamically added or removed using PCMCIA cards.

Traditional distributed applications have been designed assuming a wired execution environment. They need more and more resources and a disconnection from one part of the system is usually considered as an error. This prevents them from executing locally on portable devices. Also, resources utilization is not optimized to minimize battery consumption. Consequently, users perceive a poor quality of service when executing existing applications on a wireless context if no static and dynamic adaptation of their behavior is performed.


We think that the construction of a generic yet customizable system that can dynamically adapt to changing execution conditions would ease the adaptation of existing applications and the construction of new ones. Moreover, this system should be built as a middleware layer between the standard operating system and the applications so as to achieve a good degree of portability.


We have designed and implemented a system called MolèNE that is made up of a set of functionnalities which generic nature guides the architecture of the whole. Application-independent functionalities, called tools, are provided by a toolkit and are implemented as concrete classes. Already available tools include a network traffic manager and a set of resources monitors. Application-dependent functionalities referred to as services, are the core of an object-oriented framework that should be customized by developers in order to obtain an instance of MolèNE well-suited to their application needs. The prefetching of data and the consistency management are examples of already available services. A data and process distribution service is currently being designed in the context of the AeDEn project.

Implementing the frameworks' abstract classes allows developers to statically adapt applications to the wireless environment. Dynamic adaptation is achieved by designing a service as a set of adaptable components that encapsulate dynamic adaptation decisions concerning its own behavior. The adaptation strategy for a component is managed in MolèNE as an automaton which transitions represent adaptation actions.

Application domains and experiments

In order to validate our system, we have considered its utilization by two different types of applications: file systems in a Unix environment and transactional data bases. Practical experimentations are carried out in two environments: 

  • Local wireless networks: A waveLAN wireless local area network with two access points has been acquired to validate theoretical results concerning both types of applications. We have already perform the adaptation of the NFS file system. Operations on NFS objects are performed locally on the mobile computer then integrated to the NFS server through a proxy. The main activities of this proxy concern object transfers to the mobile computer and conflict detection and resolution. 
    Local wireless networks are also used by transactional applications such as as hospital information systems. We have also worked in this domain by adapting a transactional hospital application to a local wireless environment in the context of the Charcot project.
  • Wide area wireless networks: A laptop computer with GSM access is used to validate results concerning transactional applications on the Internet. An electronic commerce application on the Internet has been adapted to mobility in the context of the Metis project.

Perspectives and PhD Proposal

At present MolèNE allows each of its components to adapt to the variations of the mobile environment but without considering its relations with other components. Therefore, the functioning of the system as a whole can be disrupted when a component adapts and the related components are not informed. Considering such a problem, that we call the consistency problem, requires being able to describe relationships between components and to specify adaptation contracts that should be maintained when changing behavior. We envisage to extend our research work in order to define a coordination service according to the design principles of MolèNE. This service would ensure consistency of adaptations in different, related MolèNE components. This work could be proposed as a PhD subject.


MolèNE Platform

  • F. André, M.T. Segarra.
    MolèNE : un système générique pour la construction d'applications mobiles.
    Calculateurs Parallèles. Numéro spécial "Evolution des plates-formes orientées objets répartis", volume 12, number 1/2000, 2000.
    abstract (HTML).

  • M.T. Segarra, F. André.
    A Framework for Dynamic Adaptation in Wireless Environments.
    Proc. of TOOLS Europe 2000, June 2000, Mont St. Michel, St. Malo, France.
    abstract (HTML).

  • F. André, M.T. Segarra.
    A Generic Approach to Satisfy Adaptability Needs in Mobile Environments.
    Proc. of the 33rd Annual Hawaii International Conference on System Sciences (HICSS33), January 2000, Maui, Hawaii, USA.
    abstract (HTML), full paper (gzip'ed Postscript, 52K).

  • F. André, M.T. Segarra.
    A Generic Approach to Build Mobile Applications.
    INRIA Research Report No. 3723, June 1999.
    report (gzip'ed Postscript, 267K).

MolèNE File System

  • M.T. Segarra, F. André.
    MFS: A Mobile File System Using Generic System Services.
    Proc. of ACM Symposium on Applied Computing (SAC99), February 1999, San Antonio, Texas, USA.
    abstract (HTML), full paper (gzip'ed Postscript, 26K). 

  • F. André, M.T. Segarra.
    On Building a File System for Mobile Environments Using Generic Services.
    Proc. of the 12th International Conference on Parallel and Distributed computing Systems (PDCS99), August 1999, Fort Lauderdale, Florida, USA.
    abstract (HTML), full paper (gzip'ed Postscript, 59K).

Metis Middleware

  • F. André, E. Saint Pol.
    A middleware for transactional Internet applications on mobile networks.
    Proc. of the 1998 International Conference on Parallel and Distributed Processing Techniques and Application (PDPTA'98), July 1998, Las Vegas Hilton, Las Vegas, USA.
    abstract (HTML).

Charcot Project

  • F. André, E. Saint Pol.
    A middleware for transactional hospital applications on local wireless networks.
    Proc. of the 2000 International Conference on Parallel and Distributed Processing Techniques and Application (PDPTA'2000), June 2000, Monte Carlo Resort Casino, Las Vegas, USA.
    abstract (HTML).

  • F. André, E. Saint Pol.
    Un middleware pour les applications transactionnelles hospitalières mobiles.
    INRIA Research Report No. 3863 January 2000.
    report (gzip'ed Postscript, 76K). 

AeDEn System

  • F. Le Mouël, F. André.
    AeDEn : un cadre général pour une distribution adaptative et dynamique des applications en environnements mobile
    Revue Electronique sur les Réseaux et l'Informatique Répartie (RERIR), No. 11, mars 2001.
    abstract (HTML).

  • F. Le Mouël, M.T. Segarra, F. André.
    Improving Mobile Computing Performance by Using an Adaptive Distribution Framework.
    Proc. of the 7th International Conference on High Performance Computing (HiPC'2000), December 2000, Bangalore, India.
    abstract (HTML)

  • F. Le Mouël, F. André.
    AeDEn : un cadre général pour une distribution adaptative et dynamique des applications en environnements mobile.
    Proc. of the 3ème Colloque International sur les NOuvelles TEchnologies de la REpartition (NOTERE'2000), Novembre 2000, Paris, France,
    abstract (HTML).

  • F. André, A.M. Kermarrec, F. Le Mouël.
    Improvement of the QoS via an Adaptive and Dynamic Distribution of Applications in a Mobile Environment.
    Proc. of the 19th International IEEE Symposium on Reliable Distributed Systems (SRDS'2000), October 2000, Nürnberg, Germany.
    abstract (HTML)

  • F. Le Mouël, F. André.
    Distribution over Mobile Environments.
    Proc. of the 2000 ACM Symposium on Applied Computing (SAC'2000), March 2000, Villa Olmo, Como, Italy.
    full paper (gzip'ed Postscript, 25K).

  • F. Le Mouël.
    Amélioration du niveau de service par la distribution adaptative d'applications dans un environnement mobile.
    Day of Young System Researchers (JCS'99), Proc. of the 1st French Conference on Operating Systems (CFSE'1), June 1999, pp.229-232, Rennes'99, France.
    full paper (gzip'ed Postscript, 44K).

dernière mise à jour : 24 10 2000

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