Methods for Long-Term GNSS Clock Offset Prediction

Pihlajasalo, Jaakko; Leppäkoski, Helena; Kuismanen, Saara; Ali-Löytty, Simo; Piché, Robert

doi:10.1109/icl-gnss.2019.8752725

Cited by 4 publications

(2 citation statements)

References 13 publications

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“…The quality of GNSS performance depends heavily on satellite clocks [ 3 , 4 ]. In recent years, there have been a number of publications containing clock stability analyses, but the majority of them cover only one or two GNSS systems [ 5 , 6 , 7 , 8 ]. Wang et al [ 9 ] analyzed BDS clocks with the use of Allan deviation, and similar research was conducted by Steigenberger [ 10 ], but using Galileo clocks.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of Onefold Clocks of GPS, Galileo, BeiDou and GLONASS Systems

Maciuk

Lewińska

et al. 2021

Sensors

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This research is focused on searching for frequency and noise characteristics for available GNSS (Global Navigation Satellite Systems). The authors illustrated frequency stability and noise characteristics for a selected set of data from four different GNSS systems. For this purpose, 30-s-interval clock corrections were used for the GPS weeks 1982–2034 (the entirety of 2018). Firstly, phase data (raw clock corrections) were preprocessed for shifts and removal of outliers; GLONASS and GPS satellites characterize a smaller number of outliers than BeiDou and Galileo clock products. Secondly, frequency and Hadamard deviation were calculated. This study concludes that the stability of GPS and Galileo is better than that of BDS (BeiDou Navigation Satellite System) and GLONASS. Regarding noise, the GPS, Galileo, and BDS clocks are affected by the random walk modulation noise (RWFM), flashing frequency modulation noise (FFM), and white frequency modulation noise (WFM), whereas the GLONASS clocks are mainly affected only by WFM.

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Section: Introductionmentioning

confidence: 99%

Characteristics of Onefold Clocks of GPS, Galileo, BeiDou and GLONASS Systems

Maciuk

Lewińska

et al. 2021

Sensors

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“…As such, the GPS week number is modulo 1024, and at the end of the week 1023, the week counter will reset and rollover to zero; herein lies the problem. GPS time is based on modular arithmetic and is restricted to integers with a finite value that is defined; for example, in the 24-h time system, if it is currently 1800, then 8 h later, we say it is 0200, not 2600 [ 5 ].…”

Section: Introductionmentioning

confidence: 99%

GPS Week Number Rollover Timestamp Complement

Qabalin

Naser

Hawajreh³

et al. 2021

Sensors

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Global Positioning System (GPS) is a global navigation satellite system and the most common satellite system used in navigation and tracking devices. The phenomenon of week number rollover happened recently—a year ago—due to a design limitation in the week number variable that counting weeks which causes vast losses. As many fleet management systems depend on GPS raw data, such systems stopped working due to inaccurate data provided by GPS receivers. In this paper, we propose a technical and mathematical analysis for the GPS week number rollover phenomenon and suggest a solution to avoid the resulting damage to other subsystems that depend on the GPS device’s raw data. In addition, this paper seeks to provide precautionary measures to deal with the problem proactively. The Open Systems Interconnection model (OSI) and transport layer level solution that has been suggested depends on a TCP packet reforming tool that re-formats the value of the week number according to a mathematical model based on a timestamp complement. At the level of the database, a solution is also suggested which uses triggers. A hardware-level solution is suggested by applying a timestamp complement over the GPS internal controller. Complete testing is applied for all suggested solutions using actual data provided by Traklink—a leading company in navigation and fleet management solutions. After testing, it is evident that the transport layer level solution was the most effective in terms of speed, efficiency, accuracy, cost, and complexity. Applying a transport layer level complement mathematical model can fix the consequences of GPS week number rollover and provide stability to all subsystems that used GPS data from infected devices.

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