Andreas Kassler

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.

An end-to-end quality of service management architecture for wireless ATM networks

Wireless ATM networks will bridge the gap between mobility and broadband networking. The major challenge to this end consists of guaranteeing adequate end-to-end quality of service (QoS) in spite of the unreliable radio channel. In response to this we propose an integrated end-to-end QoS management architecture built around scalable error tolerant codecs, network filters and error modules to compensate for transmission errors and local QoS degradation. A broker concept combines local and distributed resource management and negotiation of QoS at different levels. By introducing QoS intervals both at application and transport level we cope with short term channel fluctuations on a wireless link. User definable degradation paths determine the behavior of the system in case the network QoS changes for a longer period of time. Mapping functions are provided to transform a QoS description from the user perspective to QoS parameters and negotiation at the network level. Incorporating media filters into the overall broker architecture allows different media codecs to be used between the source and the sinks depending on the channel conditions and link utilization while obeying user defined end-to-end QoS strategies. We draft several protocols for the sender and receiver driven multicast scenario and show, how automatic filter propagation can be achieved under given end-to-end QoS constraints.

High Quality Mobile Communication

Future communication environments have to support mobility at various levels ranging from device and personal to session and service mobility. Much effort is currently beeing spent in the areas of cellular access technology, wireless LAN technology and mobility support in IP (Mobile IP). There is a clear trend that the IP protocol is becoming the dominant networking protocol. Since standard IP networks do not provide any guarantees for the transmission quality parameters, there is a clear demand for a comprehensive QoS mechanism, which allows for adaptation in a mobile environment using heterogeneous devices with heterogeneous access networks.

Classification and evaluation of filters for wavelet coded videostreams

In this paper, we classify and evaluate filter algorithms developed for a wavelet based video coder. Filter operations convert one representation of a video stream into a different one in which the client is more interested in. Based on our previous work, we have improved the frame rate filter and the dynamic rate shaping filter with preferences (DRS-P) which allows to trade off bandwidth consumption versus visual quality using given user constraints. The user may specify a target bandwidth and his/her preferences and the DRS-P tunes its internal filter operations to match the bandwidth contract and the user preferences based on bandwidth estimates and packet statistics gathered during filter operation. We evaluate different filter settings and combinations with respect to bandwidth and processing time and show that filters can be used to efficiently support real time conferencing scenarios including mobile and low power receivers.

Self learning video filters for wavelet coded video streams

Mobile multimedia systems have to provide mechanisms to cope with the heterogeneity caused by different access network and end system capabilities inherent to wireless communication. Adapting video streams on the fly can be used to match receivers processing and hardware capabilities and the QoS characteristics of wired and wireless links. Within this paper we present a whole suit of filter services that can be applied in order to match frame rate, frame size, visual quality and bandwidth constraints. The filter operate on wavelet coded video streams and adapts them in real-time. A special self learning video filter estimates the source bandwidth of the stream, and times its internal filter operations based on users preferences in order to match a given target bandwidth. We also derive algorithms that map between the filter parameters (i.e. what operations the filters perform) and the resulting bandwidth of the stream.

Adaptive Wavelet Video Filtering

In this paper we propose a flexible adaptive media streaming mechanism based on wavelet encoded video streams. By using a combination of sender rate adaptation and filtering inside the transmission path, an appropriate tradeoff between flexibility, efficiency and security can be achieved. The media adaptation mechanisms are one part of the MASA Quality-of-Service framework, which provides end-to-end QoS enhanced multimedia communication and includes local resource management. We provide examples for syntactial and semantical filter algorithms, show the interaction of media adaptation and QoS management and present experimental measurement results.

Extending the QoS paradigm of wireless ATM to mobile broadband applications and to the user

ATM enforces traffic contracts-applications agree to send not more data then negotiated and the network tries to provide predictable service. Thus ATM based applications should be easy to develop. For wireless ATM the situation remains not the same. Hand-off to new a access point may result in invalidating the old contract and dropping connections. Applications have to cope with the new situation by e.g. adapting their bandwidth needs. In the context of this paper, we propose to shift the burden of adaptation from the application to a middleware layer, which also acts as a central co-ordinator for requesting and reserving local resources. Media adaptation is performed by using media filters which are controlled by the QoS-providing middleware. A distributed resource negotiation protocol negotiates end-to-end application QoS parameters and uses QoS mappers to derive the necessary filter settings.

Multimedia transport system for wireless ATM networks: architecture and performance

Wireless ATM networks will bring broadband applications like video conferencing to the mobile user. Due to the inherently unreliable nature of the wireless link cell loss is likely to occur, which may result in a violation of the Quality of Service contracts. Within this paper we will present our solution in terms of a generic Quality of Service (QoS) aware Audio/Video Transport Subsystem for wireless ATM. By using an object oriented approach our system can use different video coding methods for different partners, simultaneously. A QoS controller maps user defined quality parameters down to network and system QoS parameters. Our system works together with network filters and error control modules to help recovering from data loss at the wireless or wired part of the ATM-network. We will evaluate the performance of our sub-system based on simulations for the Magic WAND (Wireless ATM Network Demonstrator) system, which provides wireless access to a fixed ATM network in the 5.2 GHz band. For evaluating the impact of errors at the physical layer, we simulated the transmission of several MPEG-2 transport streams (TS) under different channel conditions resulting in different bit error rates. We analyze the suitability of different packing schemes for encapsulating the MPEG-2 TS packets into AAL5 frames based on the WAND radio model with respect to error resilience. Keywords: Quality of Service, Wireless ATM, Video Compression, Video Transmission, MPEG-2 Transport Streams

Medizinische Multimedia-Applikationen und Telemedizin basierend auf drahtlosem ATM

Drahtloses ATM bietet eine hohe Uberaagungsbandbreite, Zuverlassigkeit Bowie garantierte Dienstegute und ermoghlicht deshalb innovative Multimedia-Applikationen. Dieser Beitrag stellt das interdisziplinare Projekt „Magic WAND“(Wireless ATM Network Demonstrator) der Europaischen Union vor, das die Vorteile der drahtlosen ATM-Netzwerke einer breiten Anwenderbasis zur Verfugung stellen soll In einer internationalen Kooperation mehrerer Hochschulen und Unternehmen werden zukunftsweisende Einsatzmoglichkeiten der Inforrnatik im medizinischen Umfeld demonstriert Im Rahmen des Projektes werden die Bedurfnisse des arztlichen Personals hinsichtlich der germeinsamen Zugriffe auf Patientendaten und auf multimediale Informationen untersucht Insbesondere sollen Mobilitat zwischenmenschliche Komrnunikation und kooperatives Arbeiten nut vertrauten Anwendungsprogramn:len unterstutzt werden. Ein drahtloses ATM-Netzwerk in Verbindung mit einem heterogenen Application-Sharing- und Telekonferenzsystem karuz die Qualitat und Effizienz medizinischer Behandlungen erhebhch steigem. Arzte konnen am Krankenbett Spezialisten konsultieren und Informationen nut ihren Kollegen austauschen. Gemeinsames Bearbeiten von Dokumenten wird auf these Weise sogar auf verschiedenen Rechnerplattformen moglich. Ein besonderes Augenmerk mus aber auf potentielle Risiken der drahtlosen Kommunikation geworfen werden. Die Sicherheit der Daten, Schutz vor unberechtigten Zugriffen und mogliche elektrornagnetische Interferenzen mit medizinischen Geraten stehen dabei im Vordergrund.