Kira Kastell

Improvments in Railway Communication via GSM-R

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

Performance advantage and use of a location based handover algorithm

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.

Implementation of fast handovers and additional authentication in GSM/UMTS for high-speed users

We analyze how to speed-up handover in GSM and UMTS. There are several reasons to speed up handovers. 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. 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 saved 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

Fast Handover with Integrated Authentication for Hybrid Networks

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.

A Location-Based Handover for Use in Secure Hybrid Networks

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. Locationbased 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 network that still do not incorporate any localization method. Index Terms – handover, authentication, security, hybrid network, location-based

Potential of software-defined radios to enhance the quality of hybrid networks

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 todays network designs to see if and how software-defined radios can help to overcome them.

Overview of implementation constraints for flexible and intelligent hybrid networks

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.

Improved Fast Location-Based Handover with Integrated Security Features

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 becomemore andmore 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. Index Terms – handover, authentication, security, hybrid network, location-based

Characterizing the Mobile Radio Channel by a Conservative Dynamical System

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 signals 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