Prof. Dr. Karl Jonas
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Quantifying the spectrum occupancy in an outdoor 5 GHz WiFi network with directional antennas
(2018)
WiFi-based Long Distance networks are seen as a promising alternative for bringing broadband connectivity to rural areas. A key factor for the profitability of these networks is using license free bands. This work quantifies the current spectrum occupancy in our testbed, which covers rural and urban areas alike. The data mining is conducted on the same WiFi card and in parallel with an operational network. The presented evaluations reveal tendencies for various aspects: occupancy compared to population density, occupancy fluctuations, (joint)-vacant channels, the mean channel vacant duration, different approaches to model/forecast occupancy, and correlations among related interfaces.
More and more low-power wide-area networks (LPWANs) are being deployed and planning the gateway locations plays a significant role for the network range, performance and profitability. We choose LoRa as one LPWAN technology and evaluated the accuracy of the Received Signal Strength Indication (RSSI) of different chipsets in a laboratory environment. The results show the chipsets report significantly different RSSI. To estimate the range of a LPWAN beforehand, path loss models have been proposed. Compared to previous work, we evaluated the Longley-Rice Irregular Terrain Model which makes use of real-world elevation data to predict the path loss. To verify the results of that prediction, an extensive measurements campaign in a semi-urban area in Germany has been conducted. The results show that terrain data can increase the prediction accuracy.
This paper describes the security mechanisms of several wireless building automation technologies, namely ZigBee, EnOcean, ZWave, KNX, FS20, and Home-Matic. It is shown that none of the technologies provides the necessary measure ofsecurity that should be expected in building automation systems. One of the conclusions drawn is that software embedded in systems that are build for a lifetime of twenty years or more needs to be updatable.
The combination of Software-Defined Networking (SDN) and Wireless Mesh Network (WMN) is challenging due to the different natures of both concepts. SDN describes networks with homogeneous, static and centralized controlled topologies. In contrast, a WMN is characterized by a dynamic and distributed network control, and adds new challenges with respect to time-critical operation. However, SDN and WMN are both associated with decreasing the operational costs for communication networks which is especially beneficial for internet provisioning in rural areas. This work surveys the current status for Software-Defined Wireless Mesh Networking. Besides a general overview in the domain of wireless SDN, this work focuses especially on different identified aspects: representing and controlling wireless interfaces, control-plane connection and topology discovery, modulation and coding, routing and load-balancing and client handling. A complete overview of surveyed solutions, open issues and new research directions is provided with regard to each aspect.
WiFi-based Long Distance (WiLD) networks have emerged as a promising alternative approach for Internet in rural areas. The main hardware components of these networks are commercial off-the-shelf WiFi radios and directional antennas. During our experiences with real-world WiLD networks, we encountered that interference among long-distance links is a major issue even with high gain directional antennas. In this work, we are providing an in-depth analysis of these interference effects by conducting simulations in ns-3. To closely match the real-world interference effects, we implemented a module to load radiation pattern of commonly used antennas. We analyze two different interference scenarios typically present as a part of larger networks. The results show that side-lobes of directional antennas significantly influence the throughput of long-distance WiFi links depending on the orientation. This work emphasizes that the usage of simple directional antenna models needs to be considered carefully.
Real-World Performance of current Mesh Protocols in a small-scale Dual-Radio Multi-Link Environment
(2017)
Two key questions motivated the work in this paper: What is the impact of different usage schemes for multiple channels in a dual-radio Wireless Mesh Network (WMN), and what is the impact of some popular WMN routing protocols on its performance. These two questions were evaluated in a small and simple real-world scenario. A major concern was reproducibility of the results. We show that it is beneficial to use both radios on different frequencies in a fully meshed environment with four routers. The routing protocols Babel, B.A.T.M.A.N. V, BMX7 and OLSRv2 recognize a saturated channel and prefer the other one. We show that in our scenario all of the protocols perform equally well since the protocol overhead is comparably low not influencing the overall performance of the network.
Die Erfindung betrifft ein System (1) zum Ausrichten einer Richtfunkantenne (a1) auf eine weitere Richtfunkantenne (a2). Das System weist ein Positioniermittel (P) auf, welches an einem vom Ort der auszurichtenden Richtfunkantenne (a1) und vom Ort der weiteren Richtfunkantenne (a2) verschiedenen Ort positioniert ist, wobei der Ort des Positioniermittels (P) vom Ort der auszurichtenden Richtfunkantenne (a1) aus einsehbar ist. Erfindungsgemäß umfasst das System (1) ferner ein Berechnungsmittel (L), das ausgebildet ist, einen Ausrichtungsfehler (α) der auszurichtenden Richtfunkantenne (a1) zu bestimmen, wobei der Ausrichtungsfehler (α) einen Winkel angibt, der zwischen einer ersten virtuellen Geraden (g1), welche den Ort der auszurichtenden Antenne (a1) und den Ort der weiteren Richtfunkantenne (a2) beinhaltet, und einer zweiten virtuellen Geraden (g2), welche den Ort der auszurichtenden Antenne (a1) und den Ort des Positioniermittels (P) beinhaltet, liegt.
SDN and WMN evolved to be sophisticated technologies used in a variety of applications. However, a combined approach called wmSDN has not been widely addressed in the research community. Our idea in this field consists of WiFi-based point-to-point links managed by the OpenFlow protocol. We investigate two different issues regarding this idea. First, which WiFi operational mode is suitable in an OpenFlow managed broadcast domain? Second, does the performance decrease compared with other routing or switching principles? Therefore, we set up a real-world testbed and a suitable simulation environment. Unlike previous work, we show that it is possible to use WiFi links without conducting MAC address rewriting at each hop by utilizing the 4-address-mode.
WiFi-based Long Distance (WiLD) networks have emerged as a promising alternative approach for Internet in rural areas. However, the MAC layer, which is based on the IEEE802.11 standard, comprises contiguous stations in a cell and is spatially restricted to a few hundred meters at most. In this work, we summarize efforts by different researchers to use IEEE802.11 over long-distances. In addition, we introduce WiLDToken, our solution to optimizing the throughput and fairness and reducing the delay on WiLD links. Compared to previous alternative MAC layers protocols for WiLD, our focus is on optimizing a single link in a multi-radio multi-channel mesh. We implement our protocol in the ns-3 network simulator and show thatWiLDToken is superior to an adapted version of the Distributed Coordination Function (DCF) for different link distances. We find that the throughput on a single link is close to the physical data-rate without a major decrease over longer distances.
WiFi-based Long Distance (WiLD) networks have emerged as a promising alternative technology approach for providing Internet in rural areas. An important factor in network planning of these wireless networks is estimating the path loss. In this work, we present various propagation models we found suitable for point-to-point (P2P) operation in the WiFi frequency bands. We conducted outdoor experiments with commercial offthe- shelf (COTS) hardware in our testbed made of 7 different long-distance links ranging from 450 m to 10.3 km and a mobile measurement station. We found that for short links with omni-directional antennas ground-reflection is a measurable phenomenon. For longer links, we show that either FSPL or the Longley-Rice model provides accurate results for certain links. We conclude that a good site survey is needed to exclude influences not included in the propagation models.
An Empirical Evaluation of the Received Signal Strength Indicator for fixed outdoor 802.11 links
(2015)
For the evaluation of the received signal strength indication (RSSI) a different methodology compared to previous publications is introduced in this paper by exploiting a spectral scan feature of recent Qualcomm Atheros WiFi NICs. This method is compared to driver reports and to an industrial grade spectrum analyzer. During the conducted outdoor experiments a decreased scattering of the RSSI compared to previous publications is observed. By applying well-known mathematical tests for normality it is possible to show that the RSSI does not follow a normal distribution in a line-of-sight outdoor environment. The evaluated spectral scan features offers additional possibilities to develop interference classifiers which is an important step for frequency allocation in long-distance 802.11 networks.
TV white spaces (TVWS), are seen as a key technology to enable the efficient use of scarce sub-GHz spectrum allowing for applications that may have a huge impact on internet penetration in rural parts of Africa. We first give an overview on TVWS, its use cases and highlight possible challenges against its uptake. Then we describe our carrier-grade wireless back-hauling solution (WiBACK) and discuss its capability for working with a geolocation database ensuring zero interference with licensed users.
The lack of affordable broadband Internet connectivity in rural areas, especially in emerging regions, is seen as a major barrier for access to knowledge, education or government services. In order to reduce the costs of back-hauling in rural regions, often without access to a stable power grid, alternative solutions are required to provide high-bandwidth back-hauling at minimal power consumption to allow solar-powered operation. In this paper, we show that cost-effective low-power IEEE802.11n (MIMO) hardware together with a single cross-polarized antenna can be a viable solution to the problem. Our study shows that up to 200 Mbps of actual throughput can be achieved over distances larger than 10 km while the power consumption of a typical forwarding node is well below 10 Watts (http://wiback.org/repeater) - suitable for a cost-effective solar-powered operation. Through theoretical analysis and extensive measurements we show that such a low-cost setup can be used to establish reliable long-distance links providing high-bandwidth connectivity at low latencies and consequently providing the capacity demanded by today’s services - everywhere. Exploiting these findings we are in the process of extending existing fiber-based infrastructures in rural Africa with our Wireless Back-Haul (WiBACK) architecture.
This work describes extensions to the well-known Distributed Coordination Function (DCF) model to account for IEEE802.11n point-to-point links. The developed extensions cover adaptions to the throughput and delay estimation for this type of link as well peculiarities of hardware and implementations within the Linux Kernel. Instead of using simulations, the approach was extensively verified on real-world deployments at various link distances. Additionally, trials were conducted to optimize the CWmin values and the number of retries to maximize throughput and minimize delay. The results of this work can be used to estimate the properties of long-distance 802.11 links beforehand, allowing the network to be planned more accurately.
This book constitutes the thoroughly refereed post-conference proceedings of the 4th International ICST Conference on e-Infrastructure and e-Services for Developing Countries, AFRICOMM 2012, held in Yaounde, Cameroon, in November 2012. The 24 revised full papers presented were carefully reviewed and selected from numerous submissions. The papers cover a wide range of topics in the field of information and communication infrastructures and are grouped in topical sections on: e-Infrastructure, e-Services, e-Society, e-Health, and e-Security.
Rural areas all over the world often lacking affordable broadband Internet connectivity. High CAPEX and especially OPEX due to vast and sparsely populated areas often present an uneconomical environment for deploying traditional wireless carrier equipment. Particularly in emerging and developing countries the lack of well-trained personnel requires inherent self-managed networks. To address these issues, we have developed a carrier-grade heterogeneous Back-haul architecture which may be deployed to extend, complement or even replace traditional operator equipment. Our Wireless Back-Haul (WiBACK) network technology extends the Back-haul coverage by building on cost-effective equipment and provides highly automated self-management features still allowing for effective QoS-provisioning. Due to the limited capacity of Wireless Networks compared to cable or fiber networks, it is important to optimally utilize the wireless links and, hence, to configure them properly to match the characteristics of the wireless channel. This link calibration includes selecting the best-suited Modulation and Coding Scheme (MCS), Transmission (TX)-power and other MAC parameters such as the acknowledgment timeout. In this paper, we present our WiBACK architecture and its suitability for deployments in rural regions. Moreover, we propose a link calibration algorithm for IEEE 802.11 links and its crucial architectural role.
This book constitutes the thoroughly refereed post-conference proceedings of the Third International ICST Conference on e-Infrastructure and e-Services for Developing Countries, AFRICOMM 2011, held in Zanzibar, Tansania, in November 2011. The 24 revised full papers presented together with 2 poster papers were carefully reviewed and selected from numerous submissions. The papers cover a wide range of topics in the field of information and communication infrastructures. They are organized in two tracks: communication infrastructures for developing countries and electronic services, ICT policy, and regulatory issues for developing countries.
Rural areas all over the world often lack affordable broadband Internet connectivity. This is particularly, but not solely, true for developing and emerging countries. Also rural areas in western countries share similar problems of high capital expenditure (CAPEX) and especially operational expenditure (OPEX) due to vast and sparsely populated areas, which often present an uneconomical environment for deploying traditional wireless carrier equipment. To address these issues, we have developed a carrier-grade heterogeneous multi-radio back-haul architecture which may be deployed to extend, complement or even replace traditional operator equipment. Our Wireless Back-Haul (WiBACK) technology extends the back-haul coverage by building on cost-effective and low-power equipment while still allowing for effective Quality of Service (QoS)-provisioning. In this paper we first present a pilot scenario in Hennef-Theishohn, Germany, where the residents of a remote farm are provided with broadband Internet connectivity using a long-distance, multi-hop WiBACK network. We evaluate the QoS-related performance of this network and show that we can meet QoS demands one expects from a carrier-grade network even under heavy load conditions.
Providing Mobile Phone Access in Rural Areas via Heterogeneous Meshed Wireless Back-Haul Networks
(2011)
Wireless Mesh Networks (WMNs) are often seen as an affordable solution to bring Internet connectivity into rural and previously unconnected regions. To date, the main focus has been to provide access to classical services such as the WWW or email which requires the users to use a personal computer or a recent smart phone. In many developing regions, however, the prevailing end user device is a mobile phone. In order to connect mobile phones to an IP-based wireless back-haul networks, the network access points must provide a mobile phone air interface, compatible with GSM or UMTS specifications. Avoiding dependence on a costly mobile operator infrastructure, we propose to deploy GSM or 3GPP nano cells in order to terminate the mobile phone protocols immediately at the local network access points. Therefore, voice or data traffic can be carried over wireless back-haul networks using open protocols such as SIP and RTP. In this paper we present a meshed wireless back-haul network architecture whose access points have been equipped with GSM nano-cells. The voice packets generated by mobile phones are carried across the back-haul network in parallel to typical web or video traffic. We evaluate the QoS handling received by the voice calls across our multi-hop wireless testbed and show that our architecture can provide the resource isolation required to offer uninterrupted VoIP services in parallel to regular Internet traffic.
Meshed wireless back-haul networks are seen as an affordable technology to bring Internet connectivity into rural and previously unconnected regions. To date, the main focus is to provide access to classical services such as theWWWor email. Access to such services requires the users to use a personal computer or a recent smart phone. Especially in developing regions, the prevailing end user device is a mobile phone. In order to connect mobile phones to an IP-based back-haul network, the network access points must provide a mobile phone air interface which is usually based on GSM or UMTS. In order to avoid dependence on a costly 3GPP infrastructure, we propose to deploy GSM or 3GPP nano cells in order to terminate the mobile phone protocols immediately at the mesh access points. Hence, the voice or data traffic can be carried over IP-based networks using open protocols such as SIP and RTP.
Zukünftige Netze sollen in der Lage sein, eine Vielzahl verschiedener Dienste zu unterstützen. Dabei wird angenommen, dass sie oft keine statische Netzwerkstruktur haben und sich daher selbsttätig konfigurieren und automatisch an wechselnde Anforderungen sowie Netzwerksituationen und -änderungen anpassen sollen. Es ist wünschenswert, dass die benötigte Dienstqualität (QoS), im Besonderen für zeitkritische Anwendungen wie VoIP, automatisch gewährleistet werden kann. Das Netz soll zukünftigen Anforderungen gerecht werden, auch wenn diese zum Zeitpunkt der Erstellung noch nicht relevant oder bekannt sind. In diesem Dokument wird ein möglicher Ansatz des noch jungen Forschungsprojekts Self-NET für die Erfüllung der genannten Anforderungen skizziert und zur Diskussion gestellt.
Mobile Datenkommunikation basiert üblicherweise auf der drahtlosen Anbindung eines Endgerätes an eine Basisstation, die ihrerseits an eine feste Infrastruktur angebunden ist. In vielen Szenarien sind diese Voraussetzungen jedoch nicht gegeben. Beispiele hierfür sind Katastrophen wie Hochwasser, Erdbeben oder Flugzeugabstürze in dünn besiedelten Regionen. Einen Lösungsansatz für sich daraus ergebende Anforderungen bieten dynamisch aufgebaute Ad-Hoc Netze mit einer satellitengestützten Anbindung an eine Festnetz-Infrastruktur. In solchen Netzen stellen die mobilen Terminals die benötigte lokale Infrastruktur selbst dynamisch her. Ziel der hier vorgestellten Arbeiten ist es, die Zuverlässigkeit und Dienstqualität der verwendeten Technologien zu untersuchen und durch geeignete Mechanismen so anzupassen, dass die Anforderungen typischer Applikationen möglichst erfüllt werden. Zur Demonstration wurde ein Prototyp aufgebaut, der unter anderem die Anwendungen "Voice over IP" (VoIP), "Datenbankzugriff im Intranet" und "Internetzugang" (WWW) untersucht.
Policy based resource management for QoS aware applications in heterogeneous network environments
(2007)
Dynamic configuration and adaptation of resources for QoS-aware applications in heterogeneous access network environment (UMTS, WIMAX, WLAN DVB-T, DVB-H) using automated tools is a challenge today. The focus of this paper is a toolkit for intelligent management of resource allocation in heterogeneous network infrastructures based on policies of different actors (network operator, service providers and users). Policy based management of resources for QoS-aware applications (Video-on-Demand, Mobile TV) dependent on network capabilities, context learning and preferences of the policy actors is proposed, which enhances the current state-of-the-art and IETF standardisation. The policy management toolkit includes components for policy specification, adaptation and enforcement, which are interacting using policy repository. The design allows the automated resource adaptation for QoS based applications based on context information and hierarchical dependencies of policy actors. A learning component is integrated in order to discover the context considering measurement and monitoring data. The policy management tookit is discussed, emphasising on ontology driven policy repository design, context learning and flexible scenario-oriented management interfaces for policy specifications.
Mechanisms and protocol interactions for seamless handover of mobile multicast/broadcast services using unidirectional access networks in heterogeneous Mobile IP infrastructures are discussed and proposed. QoS based applications, such as content delivery, mobile TV, carousel and reliable downloads, requiring interaction channel, are considered, as well as recent standardization efforts for converged broadcast and mobile IP infrastructures. The proposed mechanisms are aimed to support handover of interactive mobile services using unidirectional broadcast media (DVB-H) combined with bidirectional mobile access technologies (UMTS, WLAN,WIMAX) in heterogeneous Mobile IPv6 environments. In particular, the focus is:- Enhancement and interactions of link layer tunnelling mechanisms (IETF RFC 3077) for provisioning of bidirectional connectivity in heterogeneous Mobile IP environment;- Access network selection and intelligent handover mechanisms based on IEEE 802.21 for services using unidirectional networks;- Proactive resource management for interactive services using unidirectional access networks.
Typical for the content on-demand applications, such as video-on-demand, IPTV, on-demand advertising, music on-demand, on-line gaming, is the requirement for large bandwidth and QoS guarantees. In order to provide efficiently content delivery on-demand within fixed/mobile broadband infrastructures, QoS management interfaces and tools are proposed, which are aimed at bandwidth planning and resource reservation in advance considering dynamic QoS/SLA agreements. This paper discusses strategies and tools for automated bandwidth planning of on-demand content delivery. Based on policies for handling of on-demand services with advance reservation, the Telecom providers can improve the usage of Internet resources and enhance the QoS provision
Reliable multicast transport services for content delivery in heterogeneous mobile environment
(2007)
For efficient deployment of new reliable multicast applications in heterogeneous mobile Internet environments, appropriate retransmission strategies are proposed. The focus is the minimization of the protocol overhead for reliable transport taking into account behaviour in mobile networks (oss and handover behaviour) and application requirements (such as carousel file transfer, one-to-many download and media streaming combined with recording). The proposed techniques are designed as building blocks for localized multicast error control supported by access routers. Considering IETF RMT standardization work, the discussed retransmission approaches can be used for flexible configuration of tree-based reliable multicast protocols in converged wired and wireless Internet environment. The implementation developed for the European project DAIDALOS [1] is based on Linux IPv6 environment. Simulations in ns2 focusing on the benefits of the proposed multicast retransmission schemes for particular application scenarios are presented.
On-demand multicast is used on efficient delivery to multiple receivers requiring the same content or media asynchronously. This paper discusses cost efficient reliable on-demand multicast strategy involving access router support, which is designed to be used for mobile users in converged Internet infrastructures. State-of-the-art of on-demand multicast techniques and metrics for evaluation of the efficiency of multicast transport are overviewed. Design and implementation of a new reliable on-demand multicast strategy is presented and its retransmission costs are evaluated for different mobile multicast scenarios.
With the rapid advances in multimedia content delivery technologies, there is an increasing challenge for efficient Quality of Service (QoS) based multicast transport in mobile Internet environment. This paper discusses architectural approach for provision of multicast services in heterogeneous mobile IPv6 environment using context transfer. Following issues of QoS based mobile multicast transport are addressed: - Application of context transfer between access routers for seamless handover of active multicast services; - Adaptation of multicast group management and routing designed for wired IPv6 infrastructures to heterogeneous mobile environment; - Candidate access router discovery and context aware user interfaces for optimised handover; - Reliable mobile multicast for content delivery supported by context transfer at access routers; - Distributed QoS management of multicast services in heterogeneous mobile environment. The work is part of the mobile architecture developed in the EU IST project DAIDALOS.
Zuverlässige Ad-Hoc Kommunikation mobiler Endgeräte mit satellitengestützter Internet-Anbindung
(2005)
Mobile Datenkommunikation basiert üblicherweise auf der drahtlosen Anbindung eines Endgerätes an eine Basisstation, die ihrerseits an eine feste Infrastruktur angebunden ist. In vielen Szenarien sind diese Voraussetzungen jedoch nicht gegeben. Beispiele hierfür sind Hochwasser, Erdbeben oder Flugzeugabstürze in dünn besiedelten Regionen. Einen Lösungsansatz für sich daraus ergebende Anforderungen bieten dynamisch aufgebaute Ad-Hoc Netze mit einer satellitengestützten Anbindung an eine Festnetz-Infrastruktur. In solchen Netzen stellen die mobilen Terminals die benötigte lokale Infrastruktur selbst dynamisch her. Ziel der hier vorgestellten Arbeiten ist es, die Zuverlässigkeit und Dienstqualität der verwendeten Technologien zu untersuchen und durch geeignete Mechanismen so anzupassen, dass die Anforderungen typischer Applikationen möglichst erfüllt werden. Zur Demonstration wurde ein Prototyp aufgebaut, der unter anderem die Anwendungen "Voice over IP" (VoIP), "Datenbankzugriff im Intranet" und Internetzugang (WWW) untersucht.
The MoMoSat service will enable mobile end-users to view, manage, annotate, and communicate mapbased information in the field. The handled information exists of a huge volume of raster (satellite or aerial images) and vector data (i.e. street networks, cadastral maps or points of interest), as well as text-specific geo-referenced textual notes (the so-called 'GeoNotes') and real-time voice.
3rd Generation networks as proposed by 3GPP claim to follow the path towards fixed-mobile convergence and full support of Internet services. Although the providers have obviously recognised the dynamics of the Internet, their attempt to provide IP-services over the system has led to a circuit switched architecture. This forthcoming infrastructure will be a sophisticated, complicated, and quite expensive network, with some IP-equipment in the middle (core-network). From an IETF-biased engineers view, some parts of this network and protocols could be dropped, except that they are probably needed for backward compatibility. But since backward compatibility and saving of investment is a major concern of the standardising bodies, the evolving architectures carry a big burden.
This paper presents the current stage of an IP-based architecture for heterogeneous environments, covering UMTS-like W-CDMA wireless access technology, wireless and wired LANs, that is being developed under the aegis of the IST Moby Dick project. This architecture treats all transmission capabilities as basic physical and data-link layers, and attempts to replace all higher-level tasks by IP-based strategies.
Bei der Datenübertragung im Internet ist es wünschenswert, daß unterschiedliche Datenpackete unterschiedlich behandelt werden können, damit für die zeitkritischen Anwendungen wie Internet-Telefonie die größere Priorität gewährleisten könnte. Erst dann kann ein Netzbetreiber seinen Kunden verschiedene Dienstqualitäten anbieten. Zwei grundsätzliche Mechanismen existieren, um dem Netzwerk solche Anforderungen mitzuteilen: explizit, indem vor der eigentlichen Datenübertragung Kotrollnachrichten ausgetauscht werden; implizit, indem jedes Datenpacket eine Kennzeichnung erhält. Der zweite, Differentiated Services(DS), Ansatz ist Thema dieses Referates. Bei DS wird jedem Packet den sogenannten DS-Codepoint (DSCP) im IP-Header zugewiesen, und dementsprechend erfährt ein Datenpaket eine bestimmte Behandlung durch einen DS-fähigen Router. Drei unterschiedliche Dienstklassen wurde bisher spezifiziert: Best-Effort entspricht dem derzeit im Internet verwendeten Mechanismus; Premium-Service entspricht einer virtuellen Mietleitung und soll eine rasche Weiterleitung von Paketen gewährleisten; Datenpakete mit Assured Forwarding Service (AFS) sollen besser behandelt werden als Best-Effort. Bei AFS wurden insgesamt drei Verlustklassen und vier Weiterleitungsklassen definiert. Es wird auch verschiedene Typ von DS-Router vorgestellt und diskutiert. Der praktische Einsatz erfolgte bisher immer in Laborumgebung (Uni Bern, Uni Karlsruhe, EPFL, Forschungszentrum NEC Research), größere Feldversuche stehen noch aus.
The paper describes the concept and the implementation of differentiated services over ATM. ATM components are being used in order to implement DiffServ traffic conditioning components such as shaping and policing. The implementation architecture based on a Linux router platform and some initial performance measurement results are presented
The Internet Engineering Task Force (IETF) is currently working on the development of Differentiated Services (DiffServ). DiffServ seems to be a promising technology for next-generation IP networks supporting Quality-of-Services (QoS). Emerging applications such as IP telephony and time-critical business applications can benefit significantly from the DiffServ approach since the current Internet often can not provide the required QoS. This paper describes an implementation of Differentiated Services for Linux routers and end systems. The implementation is based on the Linux traffic control package and is, therefore, very flexible. It can be used in different network environments as first-hop, boundary or interior router for Differentiated Services. In addition to the implementation architecture, the paper describes performance results demonstrating the usefulness of the DiffServ concept in general and the implementation in particular.
Recent developments in the standardization of the future Internet (driven by the IETF) and next generation telecom networks (driven by 3GPP) show a convergence towards each other. While it is currently unknown if and to what extend this development leads to a unified technical approach (in terms of signaling, routing, mobility management, charging and security) for both real-time (voice / video) and non-real-time (data) networks, the vision of an All-IP-based communication environment for all classes of traffic is one relevant option to look at.
To provide seamless handoffs is an important task of cellular systems. A user of a real-time conversation on a mobile terminal should not notice when moving from one base station to another one. In this paper we address handoff procedures in a scenario where the radio access network is assumed to be IP-based, i.e., IP is used up to the base stations, and the mobile terminal runs a Mobile IP client. First we will motivate the need for differentiation of fast handoffs and seamless handoffs. Then we will survey some previously proposed micro-mobility extensions; thereby we will address the question of what degree of micro-mobility support is needed in the typical structure of a radio access network. The main part of this paper then discusses network-initiated/assisted handoffs in combination with Mobile IP. Here, we aim to bring together ideas of 2G/3G systems and of IP-based approaches.
Multipoint data-communications is among the hot topics of communication research and development. A lot of studies and ideas have been presented, the vast majority focusing on a homogenous environment in terms of physical network, communication protocol stacks, coding schemes and/or service qualities. First straight-forward implementations –Steve Deering‘s IP multipoint on the MBone being the most popular one– already give an idea of the capabilities of a multipoint environment.
UTRAN Internet Access
(1999)
Get a KISS - communication infrastructure for streaming services in a heterogeneous environment
(1998)
An increasing number of applications include real-time audio streaming over a communication network. Well-known examples are teleconferencing, tele-presentation, Internet Radio live streams and on-demand services. In cooperation with various broadcasters, GMD provides live and on-demand audio services over the Internet. Applications are based on commercial products as well as on own software developments. This paper describes some approaches to provide a real-time audio service over the Internet, discusses problems and experiences and presents an outlook for a streaming service in the future.
ATM virtual studio services
(1996)
The term "virtual studio" refers to real-time 3D graphics systems used to render a virtual set in sync with live camera motion. As the camera pans and zooms, the virtual set is redrawn from the correct perspective. Using blue room techniques, actors in front of the real camera are then “placed in” the virtual set. Current virtual studio systems are centralized – the blue room, cameras, renderers etc. are located at a single site. However distributed configurations offer significant economies such as the sharing of expensive rendering equipment among many sites. This paper describes early expe- riences of the DVP1 project in the realization of a distributed virtual studio. In particular we de- scribe the first video production using a distributed virtual studio over ATM and make observations concerning network QOS requirements.
An Information on Demand (IoD) Teleservice developed at the German National Research Center for Information Technology (GMD) provides remote access to multimedia information consisting of audio, video, and text. It uses a bidirectional narrowband message link between the end user and the service provider, and a unidirectional broadband data link from the service provider to the end user.
News on demand
(1996)
This paper describes a solution for an interactive video service in the World Wide Web. It looks at creating an information retrieval system based on television and German video text. The service aims at presentation in the World Wide Web. The paper handles all components of this service beginning with content collection and ending with the presentation at the enduser. It starts with a look at the service as it appears to the client. It next deals with obtaining traditional media and processing them into a format for later usage in a teleservice. Then follow reflections on possible client concepts, especially methods to integrate real time video into Webpages. Video transmission also provides the main issues for the server and communication between client and server. After an explanation of our implementation the paper ends with some conclusions about experiences and future work.
This paper discusses the future trends on teleteaching applications. These include remote access to distributed virtual reality resources, information on demand teleservices and multimedia telecommunication environments across high speed multicast networks for teleteaching scenarios. A teleteaching session held by a lecturer in Berlin is multicasted across the regional metropolitan area network. The lecturer has on-line access to some virtual studio and a CM5 supercomputer in Bonn. He can interactively create virtual environments in real-time and the results are multicasted during the lecture. The students may interact with the lecturer via some Multimedia Collaboration Teleservice. They have access to Information on Demand Teleservice (IoD) which provides them with additional background material. The session is broadcasted via satellite link giving more than hundred million people the opportunity to listen and to view lectures.
Three emerging technologies are combined in a setup that has been installed and tested at GMD - the German National Research Center for Information Technology: 1. Multimedia Telecooperation Applications; 2. ATM-based high-speed networks; 3. Satellite links. The results are promising: After some initial problems, the complete scenario is up and running, allowing the interconnection of local high-speed infrastructures in rural areas to a core network via satellite. This paper describes the R&D background and state- of-the-art that led us to this approach. It then describes the communication infrastructure and the application infra- structure of the setup, the problems we had and the solu- tions we found. Finally, our experiences are summarized, and an outlook is made for future implementations.
Filling the Pipe
(1995)
An Information on Demand teleservice that was developed at the German National Research Center for Information Technology (GMD) provides remote access to multimedia information consisting of audio, video, and text [jonas et al. 94]. It uses a bidirectional narrowband message link between the end user and the service provider, and a unidirectional broadband data link from the service provider to the end user. Since the IoD teleservice is used across a satellite connection (among others), it turned out to be necessary to implement an access protocol that is optimized for the access of real-time multimedia data across a long-delay high-bandwidth link, a long fat pipe [jacobsen et al. 92]. This paper introduces the MediaService Protocol (MSP) and describes a prototype implementation (version 0.6).
The Information Footprint
(1995)
From the authors' point of view on the current state of R & D on distributed multimedia in Germany there is a significant effort of some key players preparing mltimedia solutions for different applications and markets. Many of them take use of the current workstation/PC technologies. They include new hardware building blocks and new standards in the area of services, coding, compression and networking. Limitations arise from the current computer architectures and the different layers involved.ATM is considered as a key technology for the future WANs as well as for the LANs. For the development of the European market, technologies and applications the authors hope that the Fourth Framework of scientific research and development (1994-1998) of the European Union and its ACTS program will significantly contribute to the nervous system of the economy, and more generally, to tomorrow's society.
In 1993 the interconnection of three local ATM-based networks in Berlin was initiated by DeTeBerkom, the Gesellschaft fur Mathematik und Datenverarbeitung (GMD) and the Technical University of Berlin (TUB). This paper describes the goals of this Berlin ATM LAN Interconnection (BALI) and presents first results. It introduces the infrastructure of the BALI network in its current and its accomplished state, and summarizes the technical goals of BALI. These goals include work that will be performed within the German Research Network (DFN) ATM-trial. It also describes the test-configurations for the performance evaluations of the ATM-network, and presents the first results of the evaluations. A summary is included of the work that will be performed in the near future.
Influence of priorities on the performance of a fast packet switch in the case of bursty traffic
(1992)
Existing communication networks will be replaced by integrated networks which are able to handle various types of traffic and satisfying the needs of a large number of applications. In order to offer different service classes according to different service needs, priorities have been suggested to distinguish loss sensitive data from other traffic. This is necessary when - as in packet switched networks - physical connections are not dedicated to just one application, but data packets of a number of virual circuits are multiplexed across a physical link influencing each other in terms of delay and packet loss. This paper describes the needs of some communication services, priority schemes that were suggested to offer more than one service class and simulations that were made to get a feeling for the influence of highly bursty traffic on the performance of a fast packet switch. It will show how priorities influence traffic characteristics for bursty traffic.
