Expertin

Prof. Dr.-Ing. Kira Kastell

Publikationen von Kira Kastell

Bücher und Buchkapitel

K. Kastell, “Sichere, schnelle, ortsbasierte Handover in hybriden Netzen,” Darmstädter Dissertation, Shaker-Verlag, Aachen, Germany, June 2007.

O. Strobel (Editor), “Communication in Transportation Systems,” 2 Kapitel: “Communication Networks to Connect Moving Vehicles to Transportation Systems to Infrastructure” und “Seamless Communication to Mobile Devices in Vehicular Wireless Networks”, IGI Global Book, Hershey, PA, USA, February 2013.

O. Strobel, “Optical Communications and Related Microwave Techniques,” Mitarbeit an Kapitel “Optical Data-Bus and Microwave Systems for Automotive Application in Vehicles and Airplanes and Vessels”, John Wiley & Sons, Inc., to be published in 2015.

Konferenzen/Workshops/Zeitschriften mit peer review

K. Kastell, U. Meyer, R. Jakoby, “Secure Handover Procedures,” 8th International Conference on Cellular Intelligent Communications (CIC), Seoul, South Korea, October, 2003.

Abstract — This paper presents some security issues of handover procedures with an emphasis on hybrid and high velocity networks. It describes functional as well as informational security problems that occur during handover procedures and presents how predicting the next cell during a handover procedure can help to solve these problems. 

A cell prediction is especially possible in track bounded wireless networks and in hybrid settings between a wide area and a local area network. If the cells of the local area network are much smaller than the cells of the overlaying wide area network, the next cell for a handover from the local area to the wide area network is even uniquely determined and a priori known.

K. Kastell, A. Fernandez-Pello, D. Fernandez, U. Meyer, R. Jakoby, “Performance Advantage and Use of a Location Based Handover Algorithm,” IEEE-Vehicular Technology Conference (VTC) Fall 2004, Los Angeles, California, USA, September 2004.

Abstract— In this paper we evaluate the performance of all types of handover procedures within UMTS, GSM and between the two of them. We estimate the time needed for measurements to determine the next cell during the handover preparation as well as the overall handover delay. To reduce the preparation time we suggest using the built in localization mechanisms of GSM and UMTS instead of measuring the reception level of surrounding cells. We discuss the suitability of the different localization mechanisms for the determination of the next cell. An acceleration of the handover procedures in GSM and UMTS is desirable in order to enhance the quality of calls. In particular time-savings are critical in scenarios where the duration of stay for a user within one cell is small, as it is the case e.g. for users moving with high speed. Moreover time-savings in the handover procedures can be used to help integrating an additional authentication during handovers between GSM and UMTS.

K. Kastell, R. Jakoby, “Implementation of fast handovers and additional authentication in GSM / UMTS for high-speed users,” 16th IEEE Symposium on Personal Indoor and Mobile Radio Communications (PIMRC), Berlin, Germany, September 2005.

Abstract—In this paper we analyze how to speed-up handover in GSM and UMTS. There are two main reasons to speed up handovers in existing wireless networks. On one hand these systems face problems with high-speed users, e.g. those moving in a high-speed train. This is important because the European railway organization decided to use GSM as their communication system for signaling and train control. As GSM was designed for speed up to 250 km/h there are problems with handovers and cell camping for higher speed, especially with Group Call and Group Receive Mode. As the passengers in the train are going to communicate via UMTS the handovers of UMTS have also to be speed up. On the other hand it is known that there are security problems in GSM authentication that also weaken UMTS when having handovers between both systems. Therefore it is proposed to have an additional authentication just before the handover from UMTS to GSM. We analyzed how and how much time can be save and show that we can also make use of the network topology to integrate additional authentication to secure the communication for example between the dispatcher and the train.

K. Kastell, S. Bug, A. Nazarov, R. Jakoby, “Improvements in Railway Communication via GSM-R,” IEEE-Vehicular Technology Conference (VTC) Spring 2006, Melbourne, Australia, May 2006.

Abstract — In this paper we identify several shortcomings in GSM-R use for high-speed trains. Especially cell reselection and handover last too long. If they are combined with Group Receive Mode this causes additional problems. One single solution can help to cope with them. If handover and cell reselection are aided by location information they can be accelerated. Three strategies how to derive location information in railway environment are briefly explained. The location information is taken to determine the next serving cell. This shortens preparation time for cell reselection significantly. Railway environment makes it easy to estimate the location. In the outlook we show how to transform the results given here to new applications for area-wide mobile communication systems.

S. Bug, A. Nazarov, K. Kastell, R. Jakoby “Characterizing the Mobile Radio Channel as a Conservative Dynamical System,” IEEE-Vehicular Technology Conference (VTC) Spring 2006, Melbourne, Australia, May 2006.

Abstract - Traditionally mobile radio channels are modeled as linear stochastic systems. It can be shown that stochastic modeling approaches have some physical limits, in particular if the bandwidth is very high. With this paper we want to introduce a new and alternative understanding of the physical effects the mobile radio channel is based on. Instead of analyzing time- and frequency domain by conventional methods from the field of stochastic signal processing we use algorithms which are focused on the signal's phase space. We learned that a colored Poincare-plot is a very powerful tool to characterize the mobile radio channel in that phase space. The results of characterizing the channel as a conservative dynamical system show that there are interesting mechanisms, which have not been considered in mobile radio channel modeling until now. Because this paper is too short to give a satisfactory introduction to the nonlinear dynamics of conservative systems, we focused on examples and the most important terms.

K. Kastell, R. Jakoby, “Fast Handover with Integrated Authentication for Hybrid Networks,” IEEE-Vehicular Technology Conference (VTC) Fall 2006, Montreal, Canada, September 2006.

Abstract — We analyze how to speed-up handover in and between GSM (Global System for Communications) and UMTS (Universal Mobile Telecommunications System). On one hand these systems face problems with high-speed users, e.g. those moving in a high-speed train. On the other hand it is known that there are security problems in GSM authentication, which also weaken UMTS when having handovers between both systems. Therefore additional authentication is integrated into the handover process. We show how and how much time can be saved in the handover process to allow additional authentication. Several approaches are compared and one implementation that can be done without changes of the hardware components or specifications in UMTS and GSM is shown.

K. Kastell, R. Jakoby, „Sichere ortsbasierte vertikale Handover,“ Mobilfunk - Technologien und Anwendungen - ITG-Fachbericht Band 202,  ITG (Hrsg.), Frankfurt, Germany, May 2007.

Kurzfassung - Die Mobilkommunikation der Zukunft wird aus einem Nebeneinander vielfältiger Kommunikationsnetze mit unter-schiedlichen Luftschnittstellen, Reichweiten, Datenraten, Sicherheitsstandards bestehen. Diese verschiedenartigen Netze werden als ein hybrides Netz aufgefasst, innerhalb dessen Gesamtreichweite der Nutzer sich bei bestehender Verbindung uneingeschränkt bewegen kann. Um dies zu gewährleisten, werden sog. vertikale Handover, also Handover zwischen Netzen unterschiedlicher Zugangstechnologien (und ggf. Betreiber) notwendig. Diese vertikalen Handover stellen erhöhte Anforderungen sowohl an die funktionale Sicherheit als auch an die Sicherheit der zu übertragenden Daten und der Signalisierung. In diesem Artikel wird ein ortsbasiertes Handover-Protokoll entwickelt, das beiden Sicherheitsbelangen Rechnung trägt. Dieses Protokoll wird am Beispiel eines hybriden Netzes aus GSM, UMTS und WLAN 802.11 vorgestellt. Die erreichten Verbesserungen gegenüber herkömmlichen Handover-Protokollen werden dabei nicht nur im hybriden Netz sichtbar. Das Protokoll ist vielmehr geeignet auch in jedem einzelnen Netz die Informationssicherheit zu verbessern und die Gesamtdauer des Handovers signifikant zu verkürzen.

A. Klein, A. Gershman, R. Jakoby, P. Meissner, R. Steinmetz, A. Zoubir, L. Cirillo, K. Kastell, T. Unger, „Kommunikationstechnik - Wachstumsmotor der Zukunft,“ thema Forschung 2/2007: Spannung pur, TU Darmstadt, Darmstadt, Germany, May 2007.

Kurzfassung - Kommunikationstechnik und besonders mobile Kommunikation spielen eine immer größere Rolle in unserem täglichen Leben, was sie zu einem Wachstumsmotor der Industrie macht. Die Forschung an der TU Darmstadt umfasst in diesem Bereich so unterschiedliche Themen wie agile und flexible Ressourcennutzung, Raum als neue Dimension, Signalverarbeitung, dynamische und adaptive Netze und optische Kommunikation. Das Zusammenwirken der verschiedenen Fachgebiete bildet dabei die Grundlage erfolgreicher Forschung.

K. Kastell, R. Jakoby, „A Location-Based Handover for Use in Secure Hybrid Networks," Frequenz: Journal of RF-Engineering and Telecommunications, vol. 61, 7-8/2007.

Abstract – Mobile communication systems of the future will be implemented as a hybrid network consisting of several former stand-alone and new networks. Therefore handovers and especially vertical handovers between different networks gain more and more importance. All kind of handovers has special requirements about latency and security but there are additional problems if the handovers should be performed between different networks. Those problems even get stronger if the networks belong to different providers. Location-based handovers are seen as a promising tool to provide an effective instrument for the choice of an appropriate network in a hybrid communication scenario. In this paper four typical network topologies and four classes of mobility behavior of the mobile terminals are investigated by simulation. From those simulations values for the duration and needed accuracy of the localization are derived. Also a simple workaround based on field strength measurements is provided for those networks that still do not incorporate any localization method.

K. Kastell, “Improved Fast Location-Based Handover with Integrated Security Features,” Frequenz: Journal of RF-Engineering and Telecommunications, vol. 63, 1-2/2009.

Abstract – Mobile communication systems of the future will be implemented as a hybrid network consisting of several former stand-alone and new networks. Therefore vertical handovers between different networks become more and more important. The existing handover procedures do not cope with the special needs of inter-network handovers in terms of latency and security issues. Location-based handovers are seen as a promising tool to provide an effective instrument for the choice of an appropriate network in a hybrid communication scenario, allowing low latency and integrated authentication. In this paper an improved location-based handover is shown. Therefore localization in hybrid networks is shortly analyzed. After that it is shown, how to integrate authentication into a handover procedure and that integrated authentication even can be realized, if the duration of the authentication takes more time than can be saved with the location-based handover preparation. This new approach leads to an increased number of successful handovers even compared with first versions of location-based handover algorithms.

K. Kastell, “A Fast and Secure Location-Based Handover Approach for Hybrid Networks,” World Multiconference on Systemics, Cybernetics and Informatics (WMSCI), Orlando, FL, USA, July 2009.

Abstract - In this paper the multiple challenges for handovers in hybrid networks are discussed. Based on that a location-based handover for hybrid networks is evaluated. The handover takes into consideration the increased handover preparation time in hybrid networks, coming from the use of different air interfaces and the interoperation of different network providers. Also the security of the connection is a problem as the different networks included in the hybrid network have different security mechanisms. The location-based handover introduced here can speed up the handover process in general and also enables integrated authentication. This is an important task to fulfil, because providers usually only give authenticated users access to their network. In standard handovers authentication is not included because of a lack of time. The handover is evaluated by simulation and the scenarios and results for the correct choice of the target cell are given.

K. Kastell, “A Location-Based Approach for Fast and Safe Handovers in Hybrid Networks,” World Congress in Computer Science, Computer Engineering, and Applied Computing, International Conference on Wireless Networks (ICWN), Las Vegas, NV, USA, July 2009.

Abstract - In this paper a location-based handover for hybrid networks is evaluated. The handover deals with the challenges of hybrid networks: In these networks the mobile terminal has to use different air interfaces. This makes handover preparation a time consuming task. Also the security of the connection is a problem as the different networks included in the hybrid network have different security mechanisms. The location-based handover introduced here can speed up the handover process in general and also enables integrated authentication. This is important as authentication not included in standard handovers because a lack of time. The handover is evaluated by simulation and the scenarios and results for the correct choice of the target cell are given.

K. Kastell, “Technical Innovation to overcome Regulation – Use Case: Terminating Fees in Mobile Communication,” 5th International Conference on Management of Innovation and Technology (ICMIT), Singapore, June 2010.

Abstract – Regulation is an issue controversial discussed among economists themselves and the companies affected by regulatory policies. But regulation and technical innovation, even if it is temporarily causing a dominant market position, do not have to be oppositional things. This paper aims to show incentives how companies could be pushed to implement technical innovation as a means to overcome regulatory restrictions. This is shown using the example of regulated terminating fees in mobile communication and how inter-provider Handover can lead to contestable markets.

T. Böhme, S. Harrer, M. Hirschfeld, K. Kastell, I. Kröger, S. K. Nagel, R. Pratt, J. P. Schemmel, C. Stillings, A. Wechsler, „Technologieaußenpolitik – Strategie und Technologie für globale Herausforderungen“, Policy Brief 4/10, stiftung neue verantwortung, Berlin, Germany, September 2010.

Neue außenpolitische Probleme und die Verschärfung des globalen Wettstreits um Wohlstand bei gleichzeitig wachsenden technologischen Potenzialen erfordern ein neues Politikfeld: Technologieaußenpolitik. In ihr arbeiten Vertreter von Verwaltung, Wirtschaft und Wissenschaft gemeinsam daran, die Wirkkraft deutscher Technologie- und Außenpolitik durch die Bündelung und strategische Ausrichtung unterschiedlicher Initiativen zu stärken. Sie gestalten Technologiepfade auf internationaler Ebene aktiv mit, vertiefen faire Technologiekooperationen mit anderen Ländern zum beiderseitigen Nutzen und positionieren Deutschland im globalen Standortwettbewerb.

K. Kastell, “Challenges for Handovers in Hybrid Networks,” International Workshop on Telecommunications (IWT), Rio de Janeiro, Brazil, May 2011.

Abstract—Hybrid networks are networks that consist of different access networks. These networks are only loosely coupled and in contrast to heterogeneous networks there is no additional interworking entity to be included in the hybrid network. Handovers in such networks are difficult because not only the handover protocols differ but also the authentication protocols and credentials and moreover the air interfaces. We propose a hybrid handover protocol that does not need major changes of existing standards. This protocol copes with the different protocols and includes mandatory authentication in the handover procedure. This is a prerequisite for hybrid handovers especially if more than one provider is involved. The hybrid handover protocol has been evaluated by simulations. The simulation scenarios and results of handovers between GSM, UMTS, and WiFi are given. It can be shown that the proposed protocol has a handover success rate of more than 90% in GSM and UMTS and up to 85% in WiFi. Additional measures to further improve these rates are provided. The success rate only decreased slightly compared to the conventional handover without authentication. If authentication is included in conventional intra GSM or intra UMTS handovers their success rate is only about on third of the one for the hybrid handovers presented here.

K. Kastell, “Challenges and Improvements in Communication with Vehicles and Devices Moving with High-Speed,” 13th International Conference on Transparent Optical Networks (ICTON), Stockholm, Sweden, June 2011.

Abstract - In this paper several shortcomings in communication with high-speed users in different communication scenarios are identified. This includes conventional communication systems as well these especially designed for use with railways systems, e.g. GSM-R. In the high-speed scenario there are several challenges including Doppler Effect, short duration of stay in a cell, and rapidly changing propagation delay. This causes a lot of control messages, resulting especially in too long lasting cell reselection and handover.

The improvements discussed cover network planning, coach design, inter coach network implementation and handover procedures. For the evaluation a special network topology concept and a suited mobility model have been designed. They are used in simulations carried out with MatLab and ns-2 to prove that the solutions proposed really improve the quality of the connection. It can be shown that the problems with handovers in real systems can mostly be solved by using suited handovers and can completely be solved adding integrated network planning. Anyway the solution always has to be an integrated approach comprising planning, hardware, protocols and interaction of different networks to provide the best service. This is the only way to cope with shortcomings in the standards for high-speed scenarios.

K. Kastell, “Enhancing Modern Mobile Communication Systems Using Tunable Components Made of Material Utilized in New Fields of Application,”, 19th International Conference on Composites/Nano Engineering (ICCE-19), Shanghai, China, July 2011 in special issue of World Journal of Engineering, September 2011.

Short paper – no abstract

K. Kastell, “Challenges for Handovers in Hybrid Networks,” (extended version) Revista Telecomunicações - INATEL on IWT 2011, 2011. Invited paper

Abstract—Hybrid networks are built from different loosely coupled access networks. In contrast to heterogeneous networks there is no additional interworking entity. In hybrid networks not only the handover protocols and air interfaces differ but also the authentication and credentials. We propose a hybrid handover protocol that, without the need of major changes of existing standards, copes with the different protocols and includes mandatory authentication. This is a prerequisite for hybrid handovers especially if more than one provider is involved. The protocol has been evaluated by simulations implementing GSM, UMTS, and Wi-Fi. Results show a handover success rate of more than 90% in GSM and UMTS and up to 85% in Wi-Fi. The success rate only decreased slightly compared to conventional handover without authentication. If authentication is included in conventional GSM or UMTS handovers their success rate is only about one third of the one for the hybrid handovers presented here.

K. Kastell, T.A. Daskalou, E. González-Rodríguez, R. Jakoby, “Potential of Software-defined Radios to Enhance the Quality of Hybrid Networks,” 3rd International IEEE Conference on Microwaves, Communications, Antennas and Electronic Systems, Tel Aviv, Israel, November 2011.

Abstract — Software-defined radios have received much attention recently, but only little work has targeted the identification of those components that have the highest impact on the quality of the signal transmission and reception. In this paper we therefore have a closer look at the reception path in wireless communication systems. We provide a general overview of those transmit/receive components which play a role in every communication system and give an analysis of the most prominent problems in today’s network designs to see if and how software-defined radios can help to overcome them.

K. Kastell, T.A. Daskalou, E. González-Rodríguez, R. Jakoby, “Overview of Implementation Constraints for Flexible and Intelligent Hybrid Networks”, IEEE Jordan Conference on Applied Electrical Engineering and Computing Technologies, Amman, Jordan, December 2011.

Abstract—Modern communication relies on a variety of networks. A hybrid network for simultaneous use of different access and backbone technologies is favorable to minimize installation costs and to maximize throughput, availability and user experience. In further developing strategies and implementations for hybrid networks, future requirements – not only of pure communication - should be taken into account as well as communication for control reasons and market balancing as in smart grids. There is no sense in installing even more different communication infrastructure in parallel if we can fulfill the requirements with a flexible implementation of hybrid networks. In this paper we try to highlight several issues in hybrid networks as reliability, latency, security, and interworking and show possible methods of solutions and their interaction.

K. Kastell, “Tunable Components with Novel Material Utilization to Enhance Modern Mobile Communication Systems,” World Journal of Engineering, vol. 8, 2012.

Abstract - Modern mobile communication systems face several challenges; some of the most provoking of them result from customer expectations. These challenges only can be coped with by an integrated approach modifying network planning as well as protocols as well as enhancing hardware components. Because mobile communication systems will further be developed in the future, facing yet undiscovered challenges, flexible hardware structures would be preferable, especially because the exchange of mobile devices owned by the users is nearly not possible without causing enormous costs. This approach is commonly known as software-defined radio (SDR). In this paper all aspects mentioned above are discussed focusing on novel hardware approaches in close coordination with network planning.

K. Kastell, “Challenges and Incentives for the Convergence of Backbone and Last Mile of Mobile and Fixed Line Communication Networks,” 6th International Conference on Management of Innovation and Technology (ICMIT), Bali, Indonesia, June 2012.

Abstract –The convergence of backbone networks is widely discussed under the name of next generation networks (NGNs). But the local loops such as the air interface of mobile networks and the last mile of fixed networks are still owned by single operators. Therefore they show an oligopolistic market structure which may prevent market-driven allocation and lead to high end-user prices. In this paper incentives are given for the convergence of communication networks. These arise from new engineering solutions. Their impact on the communication market is shown. Then technical solutions are exemplified and their benefits and drawbacks discussed.

K. Kastell, “Novel mobility models and localization techniques to enhance location-based services in transportation systems,” 14th International Conference on Transparent Optical Networks (ICTON), Coventry, Great Britain, June 2012.

Abstract - To evaluate and further develop communication protocols for transportation systems, new mobility models are required. Especially models covering the needs and specialities of trains and other track-bounded mass transportation systems are not easily available. These models play a critical role in the evaluation of hybrid and other overlay networks in which routing and handover depend on the preferences and QoS requirements of the mobile device. Here velocity and mobility play an important role, e.g. fast moving devices should not be handed over to very small cells, if possible. In this paper we present a mobility model for high-speed trains. This model is used in combination with other mobility models for cars and pedestrians to evaluate the accuracy and usefulness of different localization methods. Thereafter a special localization method for high-speed trains is proposed. This is used to evaluate the quality of a location-based hybrid handover protocol.

K. Kastell, “Impact of User Preferences on the Quality of Vertical Handovers,” IEEE International Conference on Wireless Information Technology and Systems (ICWITS), Wilea, HI, USA, November 2012.

Introduction - Fourth generation (4G) wireless networks are characterized by the convergence of hybrid wireless access technologies. Therefore, in 4G networks seamless and efficient handovers between the different access technologies (vertical handovers) are a core issue. A crucial part of vertical handovers is the handover decision phase. In this phase the decision about the target network is made. In hybrid networks there often is not a single best target network. The coexistence of the different access technologies with largely different characteristics creates a decision problem. In the decision phase, multiple aspects play a role. On the one hand, the decision is based on parameters such as received signal strength (RSS), network load and available capacity that need to pass a certain threshold. On the other hand it should take into account different parameters describing user preferences. The latter ones may be in conflict with the first ones.

At present, it is unclear to what extent user preferences affect success rates of vertical handovers and the quality of the connection in realistic settings. Therefore, in this paper, we focus on user preferences and investigate their impact on the target network decision. The impact of the different user preferences is compared. But we will demonstrate that also operator preferences and other constraints such as user velocity play a role. Next steps towards a dynamic handover decision function based on user and provider preferences are given.

K. Kastell, “Analysis of planning constraints and application scenarios for communication in transportation systems,” 15th International Conference on Transparent Optical Networks (ICTON), Cartagena, Spain, June 2013.

Abstract - This paper presents different use cases and scenarios for communication in transportation systems. Thereby, it highlights their differences in terms of planning constraints. Some existing networks and their parameters are introduced. Based on that, strategies for hybrid use of the same communication network infrastructures for different purposes are analyzed. Finally, protocols for interworking of existing networks are described to include hybrid use in the different network specifications. This shows the possibilities for hybrid networks already existing and gives an outlook on what to include in future network design to further allow hybrid use in combination with existing infrastructure.

K. Kastell, “Network planning for Intelligent Transportation Systems Based on Existing Wireless Networks,” 5th International Congress on Ultra Modern Telecommunications and Control Systems (ICUMT), Astana, Kazachstan, September 2013.

Abstract— Intelligent transportation systems (ITS) include a broad variety of means of transportation and a broad variety of usage scenarios and user preferences and interests. To avoid a waste of spectrum and to keep deployment cost low, a combination of existing networks and infrastructure components especially dedicated to the ITS will built an ITS. As existing networks and new usage scenarios need to be matched, network planning plays an important role. In this paper network planning constraints for interworking with existing networks are developed taking into account user preferences and usage scenarios as well as features of existing networks.

K. Kastell, “Security Requirements in Communication Networks for Transportation Systems,” 15th International Conference on Transparent Optical Networks (ICTON), Graz, Austria, July 2014.

Abstract - Security in communication systems is manifold. It can be classified in two categories: functional security and information or data security. In this paper, the different aspects of security are explained. Then different scenarios of communication networks in transportation systems are analyzed with respect to their inherent the security threats. After the introduction of some existing communication networks, these networks are compared with regard to their suitability for the security scenarios. Open issues and possible workarounds are detailed.

K. Kastell, “Communication to and in trains,” 16th International Conference on Transparent Optical Networks (ICTON), Budapest, Hungary, July 2015.

Abstract - In this paper, communication with and inside trains is analysed. Existing communication links to trains are exemplified. A semi-automated planning tool for basic calculations of the positions of base stations is shown. It is detailed, how this tool may simplify the planning process for different usage scenarios. In addition, the distribution of signals inside and between the train’s coaches is described. Both together can be used for cost calculations for operators intending to offer a certain service to train passengers. An outlook towards future use of communication inside trains is given at the end.