Tomás Robles

QoS support for an all IP system beyond 3G

Mobile radio systems beyond the third generation will evolve into all-IP systems, integrating Internet and mobile system advantages. The BRAIN project is developing a system architecture which combines local coverage broadband radio access systems based on HIPERLAN/2 with several wider-coverage mobile radio systems, enabling full coverage of seamless IP-based services for users in hot spot areas and on the move. End-to-end QoS provision is one of the major challenges in the design of such a system and must be supported by the application, network, and wireless access layers. This article proposes a QoS system architecture, including the terminal architecture, the IP-based access network, and the main characteristics of the enhancements to the air interface based on HIPERLAN/2 focusing on its wireless QoS support.

The BRAIN quality of service architecture for adaptable services with mobility support

Next generation IP networks and applications will have to address the increasingly important challenges of wireless access, mobility management, the provision of quality of service (QoS), and multimedia issues. These problems form the basis of the research within the EU financed BRAIN (Broadband Radio Access for IP based Networks) project. The project is developing a novel architecture that will be able to deal with the extreme QoS violations that are likely to occur during a running session that is exposed to the radio access environment. The core of this architecture supports different types of applications. It inherits and develops from the traditional Internet approach, but incorporates aspects of a modern flexible QoS middleware solution. The given problem is addressed in a comprehensive, modular, and open manner, by providing different APIs to different types of applications. It provides powerful functions to application programmers, but does not assume that lower level functionality must be hidden from the application programmer. It encompasses a variety of objects, APIs, end-system mechanisms and protocols to cope with the dynamic variation in mobility management and QoS. This solution will provide applications with more predictable services and allow applications to react in a pre-determined way to QoS violations.

ISABEL: A CSCW Application for the Distribution of Events

Introduction Many activities which in the past have required physical presence and direct interaction among participants can be performed in a distributed fashion with the help of advanced information technologies such as, CSCW [1,2] (Computer Supported Cooperative Work), interactive multimedia services and broadband communications. Technologies aiming at supporting the collaboration among individuals or groups are identified under the term groupware technologies. Asynchronous interactions which do not require physical presence of interacting persons have matured during the last years. Very successful examples of asynchronous groupware exist. LOTUS Notes [3] is considered probably the most successful commercial product in this area. The Internet and many of its application can be considered as groupware technologies to some extend. Technology can support today also synchronous interaction where real time contact among individuals is required. We mean by synchronous interaction the exchange of verbal, visual, ... messages or information, like the exchanges of information carried out typicaly in meetings, conversations or other activities where several participants collaborate in physical presence. Remote synchronous interaction is not new, the plain old telephone is a very good example of an old technology supporting a simple but very effective form of synchronous interaction. POTS is today by far the most demanded synchronous service. This service has evolved into N to N audioconference or videoconference facilities. Computers in general and the Internet have also had primitive types of character oriented synchronous interactive services for a long time, like TALK, IRC, ... Today low quality voice and video over the Internet is also common practice with applications like, CU-SeeMe, IVS, VAT, ... Audiovisual broadcasting is also a highly demanded type of remote synchronous interaction which has been done since many years. Although broadcasting has really no interaction because the flow of information is unidirectional, it is nevertheless being addressed in the experiments performed for creating new synchronous services. One of the most popular services on the multicast backbone of the Internet, also known as the MBONE, is the conference broadcasting for which a Session Directory (SD) exists where the list of broadcast conferences is displayed in real time. Sophisticated forms of remote synchronous interaction requiring good quality telepresence demand more bandwidth and more reliable communications to achieve a proper interaction. Therefore for setting up large sacle experiments like the RACE/ACTS Summer Schools [2,5,6,9] a complex collaboration among a large number of organizations has been needed. In addition, the availability of large …

Transformation of timing diagram specifications into VHDL code

Timing diagrams with data and timing annotations are introduced as a language for specifying interface circuits. In this paper we describe how to generate VHDL from timing diagrams in order to get a hardware implementation or simply to get VHDL code for stimuli to be used in a test bench. By giving timing diagrams a formal semantics in terms of T-LOTOS, we can apply optimizing correctness-preserving transformation steps. In order to produce good VHDL code on the way to a hardware implementation it is of great importance to introduce structures into the final description that are not automatically derivable from a given specification. The designer is rather asked to assist in introducing a structure by applying a bottom-up interactive synthesis procedure.

Heuristic-driven Techniques for Test Case Selection

Abstract We propose an approach to testing that combines formal methods with practical criteria, close to the testing engineers experience. It can be seen as a framework to evaluate and select test suites using formal methods, assisted by informal heuristics. We also introduce the formalism of enriched transition systems to store information obtained during the testing phase, and to adapt classical test generation techniques to take advantage of the possibilities of the new formalism.

Isabel distribution of the Madrid global IPv6 summit 2002 over an IPv6 transition network

This paper describes the main issues arising during the port of the Isabel CSCW application to IPv6. Isabel has been ported to IPv6 in the European IST-1999-20393 LONG project. The port was validated in the distribution of the Madrid Global IPv6 Summit in March 2002. The distribution of the Global IPv6 Summit was a large trial where access to the conference was given with ISABEL running over a network which includes native IPv6 parts, IPv6 over IPv4 tunnels as well as only IPv4 parts. The conclusions obtained are analyzed.

Transforming information in RDF to rewriting logic

RDF looks like the first step to build the Semantic Web vision. Our long-term goal is to have a sound way to verify and validate the semantic web interactions that applications and agents may develop in a distributed environment. The first step for reaching this goal is to provide a useful semantic support to RDF itself. Based on this formal support, properties may be analyzed, as well as transformations and verifications can be performed. In this paper we propose an intuitive and formal semantics for RDF by means of a translation of RDF documents into executable object-oriented modules in the formal language Maude. This translation provides a semantics for RDF documents and allows programs managing them to be expressed in the same formalism, since Maude specifications are executable. Moreover, due to the reflective features of Maude, this translation can be implemented in Maude itself. Finally, translated RDF documents are integrated in an agent application written in Mobile Maude, that is, the same framework is used for both translating RDF documents and expressing the programs that manipulate them.

Porting the session initiation protocol to IPv6

A modified Java-based SIP (session initiation protocol) implementation offers one approach to developing multimedia services that run on both IPv4 and IPv6 networks. This article describes our experiences in porting SIP to lPv6. To deploy a service in which IPv6 nodes communicate with IPv4 nodes, we selected an IPv4-IPv6 transition mechanism that combines an application-level gateway (ALG) with network address translation-protocol translation (NAT-PT) for application traffic. Our solution required us to make several modifications to the original JSIP library.

Using multimedia communication technologies in distance learning

This paper describes pilot experiences of distance learning using videoconference over the public Integrated Services Digital Network (ISDN). Graduate and postgraduate courses of the Technical University of Madrid (Telecommunication Engineers) form the educational scenario chosen for the experiences. Several phases were defined to carry out the experiments, each one centred around different students/subjects profiles. The first phase has been recently finished and it has been evaluated with interesting results from a pedagogical point of view. Organisational, technical and economical aspects has also been evaluated with the aim of extending these experiences to a larger scale.

IP QoS and mobility experimentations within the MIND trial workpackage

In addition to conceptual work, the IST MIND project aims to verify practically a set of concepts related to the use of broadband, multimedia services by mobile users in an IP network. This paper presents an overview of the trials, and focuses on a few particular topics that are dedicated to the experimentation of adaptive applications within a wireless IP access network, including advanced QoS and mobility protocols. The novelty of the experimentation is underlined, and first results are presented.