P. Kovar

Interoperable GPS, GLONASS and Galileo software receiver

The new and modernized GNSS navigation systems will provide various navigation services and signals for civil user. The system operators work on basic interoperability agreements which simplify multi-system navigation receiver architecture and reduce its cost. The most current GNSS signals of GPS, GLONASS and Galileo can be processed by one or several classical E-L correlators with a look up table PRN generator of a length of 10,230 chips. Most signals are processed optimally, but for some signals, like Galileo E1b and E1c or GPS L1C, this signal processor does not utilize all signal components and properties. The proposed E-L correlator was implemented to the FPGA of the experimental software GNSS receiver and was tested on the Galileo E1b, E1c, and E5a signals. The target multi-system GNSS receiver architecture based on an ExpressCard peripheral card for the standard PC computer or notebook is described herein. Up to one hundred universal correlators and signal snapshot capture unit for DSP acquisition are programmed to the receiver FPGA.

Multi system navigation receiver

High demands on mobile user positioning cannot be satisfied by single navigation system. The paper proposes multi system solution which utilizes navigation and communication systems and signals. The experimental software receiver is described as development tool of such combined system. The proposed receiver consist of three GNSS RF front ends of bandwidth of 24 MHz tunable to any navigation frequency from 1 to 2 GHz and one DVB-T(H) tuner. The programmable receiver hardware is based on FPGA and PC workstation which communicate each other via Gigabit Ethernet. In the second part of this paper we are presenting methods of estimation of time of arrival of OFDM (Orthogonal Frequency Division Multiplex) signal. Described estimation algorithm is used in the DVB-T(H) (Digital Video Broadcasting - Terrestrial) receiver which can be used for navigation or for support of satellite navigation receivers. The last part of this paper describes our results of experiments with DVB-T(H) navigation. They were obtained in various environments (urban, suburban, etc.) including indoor environment.

Low complex interoperable GNSS signal processor and its performance

The recent development of the GNSS systems and international cooperation resulted in important technical problems of the GNSS systems which are an interoperability and compatibility. In the interoperable receivers the most expensive parts - front ends - can be shared for signals reception of different systems. The unification of the signal processor is also possible with some small performance deterioration but the hardware complexity reduction is considerable. The paper analyses applicability of a classical E-L correlator for processing of various GNSS signals and compare its performance with optimal method. The low complex interoperable processor of software receiver based on a FPGA for the GPS, Galileo and GLONASS systems is proposed. The results of testing on the Galileo E1 and E5 signals are presented. The last part of the paper proposes architecture of a low cost multi system GNSS receiver based on mass market components.

GNSS Signals Characteristics

The paper deals with second order signals characteristics for satellite navigation systems. The main goal of the paper is to simplify and clarify signals analysis task by introducing a system of signals characteristics and their mutual relations. The conception of the system is based on the fact that the structure of navigation signals is partially given since the signals should ensure reliable pseudorange estimations. The proposed conception is then applied on the tiered code construction employed in Galileo system. Finally it is shown that the results of the tiered code analysis can be used in case of the power spectra estimation of BOC modulated signals.

GNSS receiver for GLONASS signal reception

This paper deals with the latest version of Experimental GNSS receiver built at the Czech Technical University and describes integration of GLONASS signal processing to the receiver. The new FPGA platform Virtex-D Pro by Xilinx is used and enables integration of whole digital signal processing of GNSS receiver into the single chip. The RE unit of the receiver is capable of processing all GLONASS frequency of the Li and L2 bands in two independent RE channels; each channel can process one band. The frequency selection of the appropriate satellite is accomplished in a digital correlator. The development flow of the GLONASS correlator is discussed herein. The complexity of the GLONASS correlator with complexity of GPS correlator is compared. The developed GLONASS correlator was tested in Simuelink tool during development. The next test was carried out using GLONASS simulator and real GLONASS satellite signal.

Technical Limitations of GNSS Receivers in Indoor Positioning

This paper presents an overview of aspects that have to be taken into account in use of GNSS receivers for positioning in the difficult environment, for example indoors. The performing position determination and navigation tasks in such environments come nowadays more and more in the focus of the GNSS community. The GNSS signal indoor reception is affected by strong attenuation and due to the nature of the environment by strong multipath. The paper discusses both of them and their possible impact to the navigation tasks. The effect of the user movement is discussed and the experimental measurements are presented. The measurements were realized with use of experimental GNSS software receiver, described in the paper as well.

GNSS Signal Monitoring Station

The construction of the GNSS monitoring station was planned in several phases. In the first phase the monitoring station provides monitoring all in view GPS, EGNOS, and Galileo satellites on LI frequency. The monitored data are stored in raw form. Data are also transformed to the standard format and analyzed. The PEGASUS software tool analyzes raw GNSS and SBAS data streams and giving the possibility of easy access to the data processing with graphical presentation of the results. The raw form of monitored data is stored in PC workstation to keep available all information for measurement analyses. Monitoring station provides data via internet as well. In the next phase the capability of monitoring of the Galileo E5, GPS L2 CA, and GPS L5 signals will be implemented. Since standard format supports only subset of the raw measurement information the project will continue in development of special software that directly processes raw data measurements.

Telemetry system for research stratospheric balloon

The paper presents telemetry system for stratospheric balloon mission based on the UHF transceivers designed for Internet of Things. The system operates in 869.5 MHz frequency band. The system uses very short packet without channel coding that can be successfully received and decoded under low signal to noise ratio. The modem sensitivity −124 dBm and the transmission power 25 dBm can ensure reliable communication for distances longer than 100 km with omnidirectional antennas and 200 km with 10 dBi ground station directional antenna. The telemetry system uses GFSK modulation of bit rate 1200 Bd and is designed for a transmission of the balloon position and status.

Experimental SDR receiver for monitoring and processing of solar radio bursts

The paper introduces a design of radio spectrography receiver that shall serve as equipment for reception, monitoring, and processing of solar radio bursts. These burst can affect operation of many radio communication and navigation services as is presented on example of GPS satellites signal degradation. The concept and design of the spectrography receiver is presented together with discussion of hardware requirements and proposed solution.

Empirical model of the ADS-B channel for airport area

The paper describes approach to processing of the ADS-B extended squitter signals and data provided by targets on the ground area of the airport. These signals are affected by radio channel environment which causes distortion and interference. The paper presents a method for estimation of the channel TDL model based on empirical data processing. This method is applied on measurement and processing campaign with the real signals from MLAT transmitters at the Prague Vaclav Havel airport. The results of channel model parameters are presented here as well.