Abstract: This paper presents an architecture for QoS-aware middleware platforms. We present a general framework for control, and specialise this framework for QoS provisioning in the middleware context. We identify different alternatives for control, and we elaborate the technical issues related to controlling the internal characteristics of object middleware. We illustrate our QoS control approach by means of a scenario based on CORBA.

Abstract: In this paper, we propose a new paradigm for local communication between devices in Ubiquitous Computing environments, assuming a multitude of computerized everyday appliances communicating with each other to solve tasks. This paradigm is based on the concept that the location of devices is central for the communication in such a scenario. Devices define their communication scope by spatial criteria. In our paradigm no explicit addressing or identification of communication partners is used. In comparison to traditional communication methods the approach eases routing and discovery problems and can be deployed in a highly dynamic environment without centralized services. We use the term local communication as inter-device communication in a physically restricted local area. This is well distinguish from the terms telecommunication as communication over distance where location information is explicitly hidden. The communication model (RAUM) introduced is based on the observation that humans structure their environment primarily spatially. We show that spatially aware communication, is an efficient method communication in ubiquitous computing environments. We relate the communication architecture of the OSI/ISO reference architecture. An exemplary implementation that realizes a context information system is described. Based on this system several applications (Smart Doorplate, Communication with peripheral devices) have been implemented and evaluated.

Abstract: In this paper, we describe an architecture for a scalable distributed server management system which is capable of managing media assets stored on large-scale media server networks. In addition to the functionality for a decentralized management of the whole server network, the server management system allows to make bandwidth reservations even in advance for streaming in real-time and transmitting media assets. This increases the QoS for end-users since bandwidth reservations for streaming applications can be planned and established a long time before the actual streaming process takes place. Moreover, this approach allows a tight estimation of the duration required for copying media assets among different servers of the network. In order to minimize the required amount of network bandwidth for copying media assets and to reduce the total number of copying processes, the management software provides the functionality to place media assets on the servers of the network in a way that assets of particular interest for a certain client are located on the client's local server. In this paper, the architecture of the server management system itself is presented together with the approach used to provide QoS guarantees for end-users. The overall system is using the differentiated service model. Besides the technical concept we also present results of the integration of the system into the corporate network of a german company.

Abstract: The CORBA Event Service specification lacks important features in terms of quality of service (QoS) characteristics required by multimedia information. The main objective of the work described in this paper is to augment the standard CORBA Event Service specification with a set of extensions, to turn it into an adaptable QoS middleware multimedia framework. To meet this, some extensions to the CORBA Event Service already developed with the aim of providing multicasting and reliability features have been enhanced in order to allow the close interaction with multicast transport protocols and with QoS monitoring mechanisms. The result was a QoS-aware middleware platform that actively adapts the quality of service required by the applications to the one that is provided by the underlying communication channel. The main quality of service features addressed by the platform - and discussed in the paper - are the support of sessions with different reliability levels, the provision of congestion control mechanisms and the capability to suppress jitter.

Abstract: This paper presents a framework for monitoring component interactions. It is part of a larger component framework built on top of the CORBA distributed processing environment that supports development and testing of distributed software applications. The proposed framework considers an OMG IDL specification as a contract for distributed interactions and allows precise monitoring of interaction activities between application components. The developer is not burdened with monitoring issues because all the necessary code instrumentation is done automatically. The tester is given the opportunity to use monitoring facilities for observing interactions between distributed component applications. This paper explains the monitoring framework and reasons about its expressive power, accuracy and applicability. The approach is validated in a platform for design, development and deployment of on-line services.

Abstract: In this paper, we describe an approach for transparent collaboration with java applets. The main idea behind our system is that user events occurring through the interactions with the application can be caught, distributed, and reconstructed, hence allowing Java applications to be shared transparently. Our approach differs from other collaborative systems in the fact that we make use of already existing applets and applications in a collaborative way, with no modifications to their source-code. We also prove the feasibility of our architecture presented in this paper with the implementation of the JASMINE prototype.

Abstract: This paper presents novel solutions to some of the QoS problems associated with delay sensitive multimedia applications in next generation mobile environments. Based upon a set of requirements drawn from mobile multimedia applications, we speculate that the emerging field of active networking can help address these QoS issues. We introduce a set of active software components which, when executed on active network routers, are capable of significantly reducing network handoff times for mobile devices. This paper also documents the innovative component-based active network architecture used to support and develop the QoS enhancing components described above. Finally, we demonstrate the flexible and extensible properties of the active router design through a detailed description of the workings of the components described above.

Abstract: The requirements for the QoS of distributed applications are traditionally expressed in terms of network oriented or systems oriented parameters. In general, the users of these services are not interested or capable of specifying the QoS of their services in such technical terms. In this paper, we propose modeling and engineering concepts for the mapping of end user QoS onto system and network QoS. We introduce QoS agents in structured object middleware that relate end-user QoS specifications to multimedia stream bindings. In fact, the middleware layer supports QoS classes, i.e., a set of QoS characteristics. The end user QoS requirements, generally a set of non-orthogonal specifications, must be supported using the available middleware QoS classes. We also describe the experimental environment that will be used to refine the QoS mapping mechanisms.

Abstract: The usage of multimedia applications on the Internet has seen phenomenal growth in recent years. Transport protocols that provide partially reliable service have been suggested as one approach to better handle the requirements of these applications. A partially reliable service provides applications with the possibility of a flexible tradeoff between reliability and delay/throughput. Appropriately designed coders are, however, required to fully utilize a partially reliable service. In this paper we present a JPEG image coder tailored to suit the behavior of a partially reliable byte stream service. With regular JPEG, data loss typically results in severely distorted images. The robust recoder employs three major modifications to standard JPEG in order to adapt to the partially reliable transport: (1) extended resynchronization markers in order to be able to resynchronize effectively, (2) block interleaving in order to spread out the loss of a packet across the image and (3) error concealment in order to minimize the perceived quality loss. The modifications incorporate both new inventions, such as random window interleaving, as well as variations of previously known techniques.

Abstract: Multimedia authoring does not consist solely of the specification of the temporal and spatial layout of a document. Application specific concepts (e.g. for computer based training) or animation effects (e.g. moving media items) are often required by authors. Existing multimedia authoring tools support only one specific concept for the temporal specification, spatial specification and interaction. This paper presents research results for an extensible multimedia system called MAVA (MultimediA document Versatile Architecture). It allows to integrate new and alternative concepts for multimedia documents. MAVA uses an operator based approach as meta document model, what means that all extensions will define concrete operators that will be used by authors.

Abstract: In this paper we propose a light-weight, provable secure smart card integration for the OpenPGP secure message format. The basic idea is that the secret keys are stored on a smart card and never leave it. We have integrated this new security approach into an enhanced whiteboard, the digital lecture board (dlb). Existing whiteboards neglect security mechanisms almost completely, even though these mechanisms are extremely important to allow confidential private sessions and billing. The primary application field of our concept are small and closed groups, whereas the smart card serves to testify group membership. Our first implementation supports the JAVA i-Button which provides an additional hardware security.

Abstract: Natural scientists increasingly rely on web-based information resources. The speed with which these data will be brought to the scientist's desktop in the near future, however, makes only too clear that automated support for efficient and effective use is in its infancy. In fact, most data are still processed by a combination of manual work and ad hoc programming. We propose to alleviate some of the problems by means of a research environment: a web site with highly graphical user interface that allows transparent access to resources and performs a certain degree of fusion of the information found.

Abstract: As technological advances continue to be made, the demand for more efficient distributed multimedia systems is also affirmed. Current support for end-to-end QoS is still limited; consequently mechanisms are required to provide flexibility in resource loading. One such mechanism, caching, may be introduced both in the end-system and network to facilitate intelligent load balancing and resource management. This paper introduces new work at Lancaster University investigating the use of transparent network caches for MPEG-2. A novel architecture is proposed, based on router-based caching and the employment of large scale dynamic RAM as the sole caching medium. Finally, the architecture also proposes the use of the ISO/IEC standardised DSM-CC protocol as a basic control infrastructure and the caching of pre-built transport packets (UDP/IP) in the data plane. The work presented in this paper is in its infancy and consequently focuses upon the design and implementation of the caching architecture rather than an investigation into performance gains, which we intend to report in future publications.

Abstract: When it comes to digital video, users expect more than simple VCR functionality. This paper presents a system that provides both direct manipulation and conversational interaction for digital video. The paper shows the seamless integration of different annotation techniques (synchronous and asynchronous) combined with different presentation and interaction metaphors. Direct manipulation technique is implemented with graphical and acoustical video hyperlinks. These hyperlink techniques are discussed in detail with the focus on their temporal nature driven by the duration of the accessibility of objects within a digital video. An avatar system is used to give the user an additional conversational access to information that is related to the video. This access is independent of the playback time of the video content. These techniques are implemented. Several system components like video server, video presentation and video authoring are shown. The user interaction capabilities based on the techniques mentioned above are presented.

Abstract: The term "Ubiquitous Computing" was minted by Marc Weiser from Xerox PARC for an environment where computers are available everywhere without being recognized as such. It requires small and portable, even wearable, terminal devices, and wireless network access over multiple communication channels. The UbiCampus project is visioned by IRB and VTT to study and develop the post 3G ubiquitous networking environment for intelligent applications The UbiCampus Project aims at building and using a local ubiquitous computing environment on (a part of) the campus of the University of Hannover. The project includes transmission technology, middleware and application aspects. This paper gives a short introduction into Ubiquitous Computing, introduces the basic idea of the UbiCampus project and discusses its objectives in terms of infrastructure, applications and Jini-based service architectures.

Abstract: Future multimedia applications will evolve to content-rich, interactive presentations consisting of an ensemble of concurrent, related to the presentation scenario, flows. Recent research highlights the importance of co-ordinating adaptation decisions among participating flows in order to share common congestion control state. We exploit models that quantify the effects of the dynamics of hierarchically encoded multimedia content on perceived quality and present a mechanism to apportion the session's aggregate bandwidth among its streams that improves the total session quality. Dynamic bandwidth utility curves are introduced to express the variability of multimedia content and represent the level of quality (or satisfaction) an application/user receives under given bandwidth allocations. The relative importance of the participating flows, determined either by the user or the application scenario, is also considered. We discuss our approach and analyse simulation results obtained based on trace-driven simulation.

Abstract: This paper deals with the problem of multimedia synchronisation in fully meshed multipoint videoconferencing applications. This work relies on previous work dealing with multimedia synchronisation in point to point videoconferencing: Up to now, the two main approaches are based on (1) timeline or on (2) temporal intervals composition. But, the first approach is not suited for multimedia data, and the second not suited for multipoint synchronisation. This paper then proposes a hybrid synchronisation solution taking advantage of the two preceding approaches. A multipoint videoconferencing tool based on this hybrid solution, called Confort, has been designed, developed, implemented and evaluated. This paper then deals with implementation details, as well as evaluation measurements.

Abstract: In recent years, middleware has emerged as an important architectural element in modern computer systems. For the purposes of this paper, we define middleware to be a layer of software residing on every machine and sitting between the underlying (heterogeneous) operating system platforms and distributed applications/ services, offering a platform-independent programming model to programmers, and masking out the problems relating to distribution. Examples of middleware platforms include CORBA, DCOM, Java RMI and Jini. One notable problem however with such middleware technologies is the complete lack of support for multimedia programming. A number of extensions have been proposed to such platforms, but they are often rather flawed in that they tend to treat multimedia as a service, rather than as a fundamental aspect of the underlying middleware infrastructure.

Abstract: Real-time audio over the best effort Internet often suffers from packet loss. So far, Forward Error Correction (FEC) seems to be an efficient way to attenuate the impact of loss. Nevertheless to ensure efficiency of FEC, the source rate must be continuously controlled to avoid congestion. In this paper, we describe a realisation of adaptive FEC subdued to a TCP-friendly rate control.

Abstract: The Internet explosion is driving the need for distributed multimedia presentations (DMPs), which provide multiple users with QoS-controlled multimedia services such as media distribution and virtual classroom. The provision of DMPs is usually based on the multicast communication. However, the jitter phenomenon over the best-effort Internet always disturbs the orchestration of multimedia presentations. Furthermore, the characteristics of multiple media streams combining the multicast delivery complicate the network and system deployment. In this paper, we describe the major considerations and techniques of designing multiple-stream multimedia presentations in a multicast communication environment. Based on the proposed control schemes, we develop a communication engine named Mcast. Mcast (i) provides the flexible authoring tool to allow users to author a multiple-stream multi-media presentation in a multicast environment and (ii) achieves smooth multimedia presentations with the well-designed temporal control mechanism.

Abstract: IP Telephony recently finds a lot of attention and will be used in IP based networks and in combination with the existing conventional telephone system. There is a multitude of competing signaling protocol standards, interfaces and implementation approaches. A number of basic functions can be found throughout all of those, though. This includes the addressing of participants using symbolic names, the negotiation of connections and their parameters as well as the enforcement of a dedicated handling of data streams by means of QoS signaling activities. Thus, a generic abstraction hiding underlying protocol specifics is very desirable and useful. The Delivery Multimedia Integration Framework DMIF - as part of the MPEG approach towards distributed multimedia systems - forms a general and comprehensive framework that is applicable to a wide variety of multimedia scenarios. In this paper we describe a more generalized and abstract view to basic IP Telephony signaling functions and show how these can be hidden below a common DMIF interface. This will allow for the implementation of inter-operable applications and a concentration on communication functionality rather than protocol details. We expect that this will also allow for better exchangeability, interoperability and deployability of emerging signaling extensions.

Abstract: In this paper we examine the possibility of applying Java in the field of telecommunications. We present a method based on formal descriptions we worked out for implementation of communication protocols in Java. We demonstrate how SDL descriptions can be mapped to Java code. We bring out the code of some SDL/PR constructions common for every implementation and parts of SDL descriptions that are implementation specific and apply predefined code patterns. We touch on the problem of mapping abstract data types. This conception is presented by the example of sample telecom protocol INRES and possible connections to the environment are introduced. Then we raise and discuss the matter of automatic compilation and present an SDL/PR to Java compiler. We appraise efficiency of this compilation method and the performance of the realized system. Finally we talk over the advantages and drawbacks of applying Java and give some possible fields of applications.

Abstract: The trend in wireless terminals has been to shrink a general-purpose desktop PC into a package that can be conveniently carried. Even PDAs have not ventured far from the general-purpose model, neither architectural nor in terms of usage model. Both the notebook and the personal computer generally use the same standard PC operating system such as Windows (CE) or Unix, same applications, use the same communication protocols and use the same hardware architecture. The only difference is that portable computers are smaller, have a battery, a wireless interface, and often use low power components [2]. Even though battery technology is improving continuously and processors and displays are rapidly improving in terms of power consumption; battery life and battery weight are issues that will have a marked influence on how hand-held computers can be used. Energy consumption is becoming the limiting factor in the amount of functionality that can be placed in these devices. More extensive and continuous use of network services will only aggravate this problem since communication consumes relatively much energy.

Abstract: Network appliances are specialized computing units attached to one or more communication networks. They encompass a wide range of devices, including pagers, cellular telephones, and personal digital assistants, as well as cameras, refrigerators, and other devices with network interfaces. These appliances have limited display and control capabilities, and they exchange information using fixed transport protocols and data encodings/formats. Therefore, to be accessible from various network appliances, multimedia applications must be able to send and receive data through a variety of transport protocols and be able to handle several data encodings/formats. This paper describes an architecture that allows multimedia applications to be built from collections of media servers. It also shows how these applications can exchange data with various network appliances by "mixing and matching" appropriate media servers.

Abstract: The trend in wireless terminals has been to shrink a general-purpose desktop PC into a package that can be conveniently carried. Even PDAs have not ventured far from the general-purpose model, neither architectural nor in terms of usage model. Both the notebook and the personal computer generally use the same standard PC operating system such as Windows (CE) or Unix, same applications, use the same communication protocols and use the same hardware architecture. The only difference is that portable computers are smaller, have a battery, a wireless interface, and often use low power components [2].

Abstract: This paper presents a novel approach for interaction control in large, synchronous and loosely coupled but chairperson-controlled conferences. Based on the IP-Multicast protocol which is extended by mechanisms allowing resource reservation for prioritized flows, the proposed architecture supports interaction control among conference members as well as focus control of each conference participant. Interaction control is performed by using a scalable signaling protocol: a conference may be recursively split into sub-sessions each of which provides an identical functionality independently of the others and establishes a singular session. A session is controlled by a chairperson who manually grants, revokes or rejects an interaction request of a registered session member. The granted interaction is announced to the session participants such that all participants may have their focus automatically set to the audio and video streams providing session participant. The such provided focus control enables conference participants to individually manage their own audio and video stream perception, i.e. a participant either decides individually to whom the personal attention should be granted or follows strictly the session's focus granted by the chairperson. The proposed conference control architecture provides the network-management platform to large virtual classrooms for university-like lectures over high-speed Internet-connections. While focusing the application of the conference control architecture to universitylike lectures, it remains generally applicable for any audio- and videosupported chairperson-controlled conference over the Internet.

Abstract: In this paper, we propose static and dynamic server selection techniques for multicast receivers who receive multiple streams from replicated servers. In the proposed static server selection technique, if (a) the location of servers and receivers and shortest paths between them on a network and (b) each receiver's preference value for each content are given, the optimal server for each content that each receiver receives is decided so that the total sum of the preference values of the receivers is maximized. We use the integer linear programming (ILP) technique to make a decision. When we apply the static server selection technique for each new join/leave request to a multicast group issued by a receiver, it may cause server switchings at existing receivers and may take much time. In such a case, it is desirable to reduce both the number of server switchings and calculation time. Therefore, in the proposed dynamic server selection technique, the optimal server for each content that each receiver receives is also decided so that the total sum of the preference values is maximized, reducing the number of server switchings, by limiting both the number of receivers who may switch servers and the number of their alternative servers. Such restrictions also contribute fast calculation in ILP problems. Through simulations, we have confirmed that our dynamic server selection technique achieves less than 10 % in calculation time, more than 90 % in the total sum of preference values, and less than 5 % in the number of switchings on large-scale hierarchical networks (100 nodes), compared with the static server selection.