Due to the inherent nature of their heterogeneity, resource scarcity and dynamism, the provision of middleware for future networked embedded environments is a challenging task. In this paper we present a middleware approach that addresses these key challenges; we also discuss its application in a realistic networked embedded environment. Our application scenario involves fire management in a road tunnel that is instrumented with networked sensor and actuator devices. These devices are able to reconfigure their behaviour and their information dissemination strategies as they become damaged under emergency conditions, and firefighters are able to coordinate their operations and manage sensors and actuators through dynamic reprogramming. Our supporting middleware is based on a two-level architecture: the foundation is a language-independent, component-based programming model that is sufficiently minimal to run on any of the devices typically found in networked embedded environments. Above this is a layer of software components that offer the necessary middleware functionality. Rather than providing a monolithic middleware 'layer', we separate orthogonal areas of middleware functionality into self-contained components that can be selectively and individually deployed according to current resource constraints and application needs. Crucially, the set of such components can be updated at runtime to provide the basis of a highly dynamic and reconfigurable system
Abstract The innate dynamicity and complexity of mobile ad-hoc networks (MANETs) has resulted in numerous ad-hoc routing protocols being proposed. Furthermore, numerous variants and hybrids continue to be reported in the literature. This diversity appears to be inherent to the field—it seems unlikely that there will ever be a ‘one-size-fits-all’ solution to the ad-hoc routing problem. However, typical deployment environments for ad-hoc routing protocols still force the choice of a single fixed protocol; and the resultant compromise can easily lead to sub-optimal performance, depending on current operating conditions. In this paper, we address this problem by exploring a framework approach to the construction and deployment of ad-hoc routing protocols. Our framework supports the simultaneous deployment of multiple protocols so that MANET nodes can switch protocols to optimise to current operating conditions. The framework also supports finer-grained dynamic reconfiguration in terms of protocol variation and hybridisation. We evaluate our framework by using it to construct and (simultaneously) deploy two popular ad-hoc routing protocols (DYMO and OLSR), and also to derive fine-grained variants of these. We measure the performance and resource overhead of these implementations compared to monolithic ones, and find the comparison to be favourable to our approach.
This chapter contains sections titled: Introduction and Motivation Early Developments Current Architectures Applying the Technologies Meeting Future Challenges Conclusion
Neil Williams, Gordon S. Blair, Geoff Coulson,Nigel Davies and Tom RoddenComputing Department,Lancaster University,Bailrigg, Lancaster,LA1 4YR,UK.Tel. +524 593054email [nw,gordon,geoff,nigel,tam]@comp.lancs.ac.ukABSTRACTRecent advances in distributed multimedia technologies are likely to have asignificant impact on the co-operative work practices of organisations.However, at present there is little practical experience with distributedmultimedia systems. This paper examines the potential for multimedia systemswithin a particular end user organisation. A pilot multimedia informationsystem is described which has been designed to support a specific co-operativeworking scenario identified within the organisation. The paper concludes thatmultimedia can have a significant impact on co-operative working. However,considerable attention must be given to the required system support for suchapplications. The development of integrated multimedia information systems isseen as particularly important. Without this, the full potential of multimedia andco-operative working cannot be fully realised.1. INTRODUCTIONCo-operative working involves a number of people working together to achieve acommon goal. The distribution of organisations, however, often requires that personnel areforced to work with colleagues who are situated remotely. The geographic distancebetween personnel constrains the degree to which they can collaborate. Communicationstechnologies are important in helping to overcome these constraints and achieve the desiredlevel of remote co-operation. Until recently, however, communications technologies havefailed to provide the required level of support for remote user interaction. For example,technology constraints have restricted computer support for co-operative working (CSCW)to a limited set of media types. The majority of applications have been restricted to text andgraphics communication, but have not been able to exploit media types such as audio andvideo. Those systems developed to provide co-operative working in conjunction with audioand video have been forced to use non-digital networks for these more demanding forms ofmedia. Such systems present the user with a non-integrated information system.However, advances in networking technology and the availability of multimediaworkstations have led to the emergence of distributed multimedia systems. Such systemsare able to support a full range of media including text, graphics, image, audio and video in
There is an increasing tendency in sensor networks (and related networked embedded systems) to push more complexity and 'intelligence' into end-nodes. This in turn leads to a growing need to support isolation between the software modules in a node. In conventional systems, isolation is achieved using standard memory management hardware; but this is not a cost-effective or energy-efficient solution for small, cheap embedded nodes. We therefore propose a software-based solution that promises isolation in a significantly lighter-weight manner than existing software-based mechanisms. This is achieved by frontloading effort into offline compilation phases and leaving only a small amount of work to be done at load time and run time.
Though distributed object computing has developed very rapidly over the past few years, the area is still lacking in terms of support for distributed multimedia applications which are fast becoming a very important part of the computing environment. This paper discusses the design and implementation of a multimediacapable distributed object platform, using a low-level platform GOPI (General Object Platform Infrastructure). It involves the design of a minimal Interface Definition Language (IDL) compiler for the support of simple operations, using the specifications of the Object Management Group’s (OMG) IDL. Based on the computational model of the Reference Model for Open Distributed Processing (RM-ODP), the IDL is then extended to support stream interfaces along with quality of service (QoS). Running Title : A Multimedia-capable Distributed Object Platform Keywords : Multimedia; GOPI; IDL; CORBA; Quality of Service; Middleware; Distributed Systems.
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