Andriy Konovaltsev

Development of Robust Safety-of-Life Navigation Receivers

This paper summarizes the development of safety-of-life receivers for global navigation satellite systems. Two receiver systems have been successfully fabricated, integrated, and tested by means of field experiments. Implementation issues of these two systems are described in this paper. The third generation of this receiving system is based on a dual-band approach with antennas that are able to separate two frequency bands using two outputs. Measured results show that high isolation between the two bands can be achieved.

Antenna and RF front end calibration in a GNSS array receiver

The use of spatial-domain signal processing for mitigation of interference signals in receivers of global navigation satellite systems (GNSS) allows for improvement of the overall system performance. To fully benefit from the use of adaptive antenna arrays, the individual signal processing paths in such a multi-antenna system should be thoroughly calibrated. The focus of this paper is on the specifics of such calibration in receivers for satellite navigation systems (e.g. GPS and coming Galileo). The design goals of the antenna and RF front end for GNSS receivers are reviewed. The architecture of a GNSS array receiver for safety-of-life applications with high robustness against radio interference is presented. The practical solutions for the antenna array and RF front-end calibration along with the field test results demonstrating their performance are outlined.

Simulation of Multi-Element Antenna Systems for Navigation Applications

The application of user terminals with multiple antenna inputs for use with the global navigation satellite systems like Global Positioning System (GPS) and Galileo has attracted more and more attention in the past years. Multiple antennas may be spread over the user platform and provide signals required for the platform attitude estimation or may be arranged in an antenna array to be used together with array processing algorithms for improving signal reception, e.g., for multi-path and interference mitigation. In order to generate signals for testing of receivers with multiple antenna inputs and corresponding receiver algorithms in a laboratory environment, a unique hardware signal simulation tool for wavefront simulation has been developed. The signals for a number of antenna elements are first generated in a flexible user defined geometry as digital signals in baseband and then mixed up to individual RF-outputs. This paper describes the principle functionality of the system and addresses some calibration issues. Measurement setups and results of data processing with simulated signals for different applications are shown and discussed.

Non-Gaussian Error Modeling for GBAS Integrity Assessment

Four basic error sources exist for residual pseudo-range errors in a single frequency differential GPS system for ground based augmentation (GBAS): signal multipath, increased receiver noise (carrier-to-noise density ratios (C/N0)) due to interference, residual differential troposphere error, and the error induced by ionosphere gradients. Without restricting ourselves to classical Gaussian overbounding, we combine their probability density functions (pdfs) to a total pseudo-range error distribution. This distribution is propagated through the GBAS Hatch filter and then mapped into the position domain using a worst case (selected by maximum vertical dilution of precision (VDOP)) of a full 31 satellite constellation with the two most critical satellites failed observed at Braunschweig Airport, Germany. Our calculations yield a significant reduction amounting to 46% of the position domain error at the 1.5 × 10-7 integrity risk level when compared with the classical Gaussian overbounding approach.

Concepts, Development, and Validation of Multiantenna GNSS Receivers for Resilient Navigation

Array processing proved itself in the last decades as a powerful approach to suppress harmful radio frequency interference. However, the interference mitigation in the spatial domain can also lead to the attenuation and loss of the desired Global Navigation Satellite System (GNSS) signals that are not sufficiently separated by their directions of arrival from the interfering signals. In order to overcome this effect, this paper proposes an approach to combine array processing and vector tracking in a single receiver. Formerly, the vector tracking loops have been shown to deliver superior performance in scenarios with blocked line-of-sight signals due to aiding of the affected signals during the outage. Since vector tracking loops are susceptible to faked GNSS signals, the proposed receiver architecture also includes a spoofing detection based on the direction-of-arrival estimation. The paper presents the technical concept and details about the realization of the array-based receiver that was developed at the German Aerospace Center (DLR). The techniques used to mitigate brute-force radio frequency interference and to detect spoofing signals are described. Experimental results obtained with these techniques in field are discussed.

Development of robust safety-of-life navigation receivers at the german aerospace center (DLR)

This paper summarizes the development of safety-of-life receivers for global navigation satellite systems (GNSS) that has been being conducted at the Institute of Communications and Navigation of the German Aerospace Center (DLR). Two receiver systems have already been successfully fabricated, integrated and tested by means of field experiments. Implementation issues of these two systems are described in this contribution. Details about the third generation of DLRs receiving system, which is currently under development, are also briefly discussed.

Comparison of SAGE and classical multi-antenna algorithms for multipath mitigation in real-world environment

The performance of the Space Alternating Generalized Expectation Maximisation (SAGE) algorithm for multipath mitigation is assessed in this paper. Numerical simulations have already proven the potential of SAGE in navigation context, but practical aspects of the implementation of such a technique in a GNSS receiver are the topic for further investigation. In this paper, we will present the first results of SAGE implementation in a real world environment.

Navigating in the Galileo test environment with the first GPS/Galileo multi-antenna-receiver

Array processing is a very promising technology for mitigation and detection of radio interference in receivers of satellite navigation systems. This paper presents early results of a multi-antenna receiver measurement campaign in Berchtesgaden GATE.

Jamming and Spoofing in GPS/GNSS Based Applications and Services – Threats and Countermeasures

GPS positioning and time synchronization have become crucial for a large variety of services and applications. Especially for safety-critical applications and infrastructure networks a reliable and robust service of GPS is essential. However, the availability of cheap jamming devices has recently demonstrated the threat for GPS applications. GPS jamming is no longer only a hypothetical threat, it is already present and will become increasingly dangerous for GPS users. For this reason the German Aerospace Center (DLR) developed strategies to cope with these threats and to retain a valid position solution even in harsh interference environments.