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Forschungsarbeit

An UMTS Jammer Triggering User-Equipment Inter-RAT Cell Reselection: Research report of Diploma thesis

By Markus Gardill (04.02.2011)

It is known from experience that about 80% of the victims buried under a heap of ruins of a collapsed building have a mobile phone on their person. A recent search project in cooperation with the German Federal Agency for Technical Relief (1) utilizes this fact for minimizing the time necessary to rescue buried people by localizing their mobile phones. This approach is based on a low-level global system for mobile communications (GSM) base station which traps all mobile phones operating in GSM mode within its coverage area. In this way the mobile phones are kept under control by the low-level base station. The mobile terminals then can be prompted to transmit several RF bursts and are localized by using time-difference-of-arrival (TDOA) measurements as well as spatial electromagnetic field analysis methods on those bursts.

It is known from experience that about 80% of the victims buried under a heap of ruins of a collapsed building have a mobile phone on their person.[Bildunterschrift / Subline]: It is known from experience that about 80% of the victims buried under a heap of ruins of a collapsed building have a mobile phone on their person.

In order to be trapped by the low-level base station the target mobile devices have to operate in GSM mode. However, especially in suburban and urban areas a modern cell phone will most likely not be camped on GSM, but on the modern UMTS infrastructure. Hence the GSM based localization technique will remain useless in those regions.

One solution to tackle that problem is to force all desired target mobile devices to leave the UMTS frequency bands and to camp on available GSM cells. We focus on triggering this inter radio access technology (RAT) cell reselection by using a transmitter radiating a sophisticated RF signal. All mobile devices within the effective range of this UMTS jammer are forced to leave the UMTS cells they are camped on and to reselect GSM cells, where they can be trapped by the low-level GSM base station.

In this figure we see how the localization using low-level GSM base works after a natural disaster.[Bildunterschrift / Subline]: In this figure we see how the localization using low-level GSM base should work after a natural disaster.

A particular challenge for the design of the UMTS jammer is the robustness of the UMTS air-interface wideband code division multiple access (WCDMA) against interference. As the jamming system should use as less RF power as possible, only very sophisticated jamming signals are suitable for triggering the inter RAT cell reselection. In the thesis we propose and examine four different strategies for minimizing the jammer RF power and hence maximizing the effective range of the jamming system. Some of those jamming strategies make use of inherent characteristics of the WCDMA air-interface and the cell reselection procedure as defined in the UMTS standards, while others are focused on delivering corrupted information to higher-layers residing in the mobile devices protocol stack.

Besides the theoretical approaches for the jamming signal design a fully-functional hardware system was developed in the scope of the thesis. This hardware system is based on a PC controlled FPGA capable of generating a digital representation of some of the proposed jamming signals. With an RF frontend the digital signal is converted to its analog RF counterpart and finally transmitted on the UMTS downlink frequency bands. Using the hardware system the efficiency of the proposed jamming strategies was evaluated on a practical basis and the impact of the jammer on mobile devices could be proven under realistic conditions.

This figure shows us which hardware system is theoretical necesary.[Bildunterschrift / Subline]: This figure shows us which hardware system is theoretical necessary.

References:

[1] Forschungsverbund I-LOV. Intelligentes, sicherndes Lokalisierungssystem für die Rettung und Bergung von Verschütteten. [Online] 2010. http://www.i-lov.org.


Markus Gardill
*1985, Bamberg
Stationen
  • since 10/2010
  • Research Assistant at the Institute for Electronics Engineering, University of Erlangen-Nuremberg, Field of Research: ultra-wideband antenna arrays, direction-of-arrival estimation for UWB FMCW radar
  • 2008-2010
  • Elite study program Systems of Information and Multimedia Technology, Friedrich-Alexander-University of Erlangen-Nuremberg, Concentrations: signal processing, communications and RF engineering, Grade 1,2 (graduated with honors)

Auslandsaufenthalte und berufliche Erfahrungen
  • 06/2010 - 8/2010
  • Internship Rohde & Schwarz Communication GmbH, Munich, Development of satellite surveillance systems

Awards and Honors
  • EADS Argus Award 2010
  • Science Award High-Frequency and Information Technology

Veröffentlichungen
  • A. Sehr, M. Gardill, and W. Kellermann, "ADAPTING HMMS OF DISTANT-TALKING ASR SYSTEMS USING FEATURE DOMAIN REVERBERATION MODELS", European Signal Processing Conference 2009, Glasgow, August 2009
  • M. Gardill, S. Zorn, R.Weigel, A. Kölpin, “Triggering User-Equipment Inter-RAT Cell Reselection Using Noise Jammers”, German Microwave Conference 2011, Darmstadt, March 2011