Wireless Ultra-Wideband (UWB) systems are characterized by an enormous bandwidth, ranging up to several GHz. It is therefore a promising candidate for high data rate indoor communications and, in parallel, for the precise localization of UWB signal-emitting objects. The reason is that the huge bandwidth results in very short pulses in the order of 100 picoseconds and below. These short pulses lead to a very high resolution of 10cm and even less.
Compared to an outdoor scenario the distance between objects is very short in an indoor scenario. Considering all reflections etc. this means that the number of significant paths at the receiver is considerably high. To be able to resolve these multipath components, the short pulses are beneficial requiring a bandwidth as high as 2.5GHz. To allocate such a high bandwidth UWB was designed as an underlay system, meaning that it is coexisting with other systems in the same frequency band. To avoid interference the signal power is limited to 0.5mW (note: GSM cellular phone up to 2W).
Therefore the challenges in the design of a UWB system are in the development of components covering such a huge bandwidth as well as in the detection of such hardly to discover signals.
A specific challenge in the context of locating systems arises when localizing a transmitter whose Line of Sight is blocked by other objects. This is called Non Line of Sight (NLoS) situation and exists for instance when the transmitter is behind a wall.
R & D Highlights
The focus of the RoboLoc project lies on the evaluation of a new localization algorithm named BeamLoc. It has been shown that this algorithm is capable of dealing with NLoS situations by taking advantage of highly directional antennas.
In the first step a simulation framework has been built up so that the BeamLoc as well as other localization approaches can be tested and compared with each other in a fully deterministic environment.
In the second step different testbeds have been built up to validate the basic principle of the algorithm. The measurements have been embedded into the simulation environment to be able to analyse and optimize the parameters.
One of the highlights of the project lies on the highly directional antennas as these are not realised by a mechanically steered single antenna but with a so called phased array. At this multiple antennas are excited at different delay times leading to an additive superposition in a single direction. By controlling these delay times the array can be steered electronically.
Potential Applications and Future Issues
Indoor localization leads to numerous of applications. Among these are not only classical navigation devices but also devices which allow for the localization of equipment in a hospital, positioning of autonomous vehicles in warehouses etc. Furthermore the development of ultrawideband electronically steered arrays is of potential interest in the area of automotive radar leading to a multiplicity of safety and driver assistance applications.
Holger Thye, Heyno Garbe, Sebastian Sczyslo, Gunnar Armbrecht, Sven Dortmund, and Michael Koch (2010): "Nutzung von GTEM-Zellen zur transienten Charakterisierung von UWB-Antennen" Internationale Fachmesse und Kongress für Elektromagnetische Verträglichkeit (EMV 2010), Düsseldorf, Germany, 9-11 Mar, 2010
Sebastian Sczyslo, Gunnar Armbrecht, Holger Thye, Sven Dortmund, and Thomas Kaiser (2010): "Comparison of the two-antenna method and the GTEM method to measure the impulse response of a cone antenna", 10th Management Committee Meeting COST 2100, Athens, Greece, 3-5 Feb, 2010
Holger Thye, Sebastian Sczyslo, Gunnar Armbrecht, Sven Dortmund, and Heyno Garbe (2009): "Transient UWB Antenna Characterization in GTEM Cells", IEEE EMC Society Symposium on Electromagnetic Compatibility, Austin, USA, 17-21 Aug, 2009
Sebastian Sczyslo, Christiane Senger, and Thomas Kaiser (2009): "A 2-Dimensional Filter for UWB-Localization in NLoS Scenarios using BeamLoc", 6th Workshop on Positioning, Navigation and Communication 2009 (WPNC 2009), Hannover, Germany, 19 Mar, 2009
Sebastian Sczyslo, Holger Thye, Gunnar Armbrecht, Sven Dortmund, and Thomas Kaiser (2009): "Determination of the Impulse Response of UWB Antennas Using GTEM Cells", 2009 IEEE International Conference on Ultra-Wideband (ICUWB 2009), Vancouver, Canada, 9-11 Sep, 2009
Q. Cai, Z. Zhao, S. Sczyslo, A. Wilzeck, C. Senger, T. Kaiser (2008): A Distributed Simulation System and its Application for 3GPP LTE Indoor Scenarios Proc. of the Third International Symposium on Wireless Pervasive Computing (ISWPC 2008), Santorini, Greece, May 2008
Grzegorz Adamiuk, Sebastian Sczyslo, Saeed Arafat, Werner Wiesbeck, Thomas Zwick, Thomas Kaiser, and Klaus Solbach (2009): "Infrastructure-Aided Localization with UWB Antenna Arrays" Frequenz, Journal of RF-Engineering and Telecommunications, vol. 63, pp. 210-213, Oct. 2009.
Sebastian Sczyslo, and Thomas Kaiser (2009): "Evaluation of Localization Measurements in LoS and NLoS Scenarios Using Antenna Arrays", 39th European Microwave Conference 2009 (EuMC 2009), Rome, Italy, 29 Sep - 1 Oct, 2009