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GNSS signal processing in GPU

Roule P., Jakubov O., Ková P., Kamaík P., Vejražka F.

Artificial Satellites : Journal of Planetary Geodesy

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2013

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Vol. 48, No. 2

51--61

EN

Signal processing of the global navigation satellite systems (GNSS) is a computationally demanding task due to the wide bandwidth of the signals and their complicated modulation schemes. The classical GNSS receivers therefore utilize tailored digital signal processors (DSP) not being flexible in nature. Fortunately, the up-to-date parallel processors or graphical processing units (GPUs) dispose sufficient computational power for processing of not only relatively narrow band GPS L1 C/A signal but also the modernized GPS, GLONASS, Galileo and COMPASS signals. The performance improvement of the modern processors is based on the constantly increasing number of cores. This trend is evident not only from the development of the central processing units (CPUs), but also from the development of GPUs that are nowadays equipped with up to several hundreds of cores optimized for video signals. GPUs include special vector instructions that support implementation of massive parallelism. The new GPUs, named as general-purpose computation on graphics processing units (GPGPU), are able to process both graphic and general data, thus making the GNSS signal processing possible. Application programming interfaces (APIs) supporting GPU parallel processing have been developed and standardized. The most general one, Open Computing Language (Open CL), is now supported by most of the GPU vendors. Next, Compute Unified Device Architecture (CUDA) language was developed for NVidia graphic cards. The CUDA language features optimized signal processing libraries including efficient implementation of the fast Fourier transform (FFT). In this paper, we study the applicability of the GPU approach in GNSS signal acquisition. Two common parallel DSP methods, parallel code space search (PCSS) and double-block zero padding (DBZP), have been investigated. Implementations in the C language for CPU and the CUDA language for GPU are discussed and compared with respect to the acquisition time. It is shown that the GPU implementation was approximately sixteen times faster than the CPU’s for signals with long ranging codes (with 10230 number of chips - Galileo E5, GPS L5 etc.).

2

Accuracy performance of e-Loran receivers under Cross-Rate Interference conditions

Šafář J., Williams P., Vejražka F.

Annual of Navigation

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2012

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No. 19, part 1

133--148

EN

According to a recent Business Case produced by the General Lighthouse Authorities of the United Kingdom and Ireland (GLAs), e-Loran is the only system that, when combined with GNSS, can achieve cost effective resilient Positioning, Navigation and Timing (PNT) by 2018 for maritime e-Navigation. The GLAs currently operate a trial e-Loran service from Harwich, UK and are working towards establishing e-Loran Initial Operational Capability (IOC) in the seven busiest UK ports and port approaches by mid-2013. A future extension of e-Loran coverage to the entire GLA service area will require the installation of additional transmitting stations. When planning the installation of e-Loran transmitters service providers will need a good understanding of the effects of the new signals on the system’s performance. Since all e-Loran stations share the same frequency band and the e-Loran signals propagate over vast distances, special attention needs to be paid to the issue of intra-system interference. This is also referred to as Cross-Rate Interference (CRI) and is inherent to the way e-Loran operates. In this paper we examine the impact of CRI on the position accuracy performance of e-Loran receivers. First, a signal processing model for a typical e-Loran receiver is developed. This could provide the e-Loran community with a unified framework for receiver performance evaluation. Numerical and, where possible, analytical results obtained from the model are then presented, describing the achievable accuracy performance under different interference conditions. The theoretical results are also compared to those obtained from measurements made on a commercially available receiver driven by a signal simulator. Our analysis shows that modern e-Loran signal processing algorithms can achieve a substantial reduction of the negative effects of CRI. However, there is still an appreciable residual effect, which should be taken into account when designing future e-Loran networks and determining their coverage and performance.

3

Local augmentation in GNSS

Seidl E., Kovař P., Puričer P., Vičan M., Vejražka F.

Zeszyty Naukowe. Transport / Politechnika Śląska

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2005

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z. 59

353-361

EN

GNSS usability and reliability in transport telematics applications can be improved by local augmentation systems. GSM/GPRS or other radio-data network can be utilised. Algorithms of augmentation and integration of current GPS and prepared European Galileo system are developed and tested using the Experimenta/ GNSS receiver based on the SDR principles and FPGA technology.

PL

Użyteczność i niezawodność GNSS w zastosowaniach telematyki transportu może ulec poprawie poprzez lokalne systemy wzmocnienia. Można wykorzystać GSM/GPRS oraz inne sieci danych radiowych. Algorytmy wzmocnienia i integracji bieżących GPS oraz przygotowywanego europejskiego systemu Galileo są opracowywane i testowane za pomocą eksperymentalnego odbiornika GNSS opartego na zasadach SDR i technologii FPGA

4

Radio Systems for Real Time GNSS - experimental GMSS Receiver

Vejražka F., Seidl L., Kovár P., Kačmařik P.

Reports on Geodesy

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2002

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z. 3/63

29-38

EN

This paper deals with the radio systems for real time satellite navigation and position determination GPS, GLONASS and GALILEO. The AGPS, DGPS and RTK modes of GPS including requirements for data channel are analyzed here. The CTU experiments with the RDS DGPS, LW DGPS, DGPS reference station and ExperimentalGNSS receiver are presented in this paper.