CSAC Characterization and Its Impact on GNSS Clock Augmentation Performance

Chip Scale Atomic Clocks (CSAC) are recently-developed electronic instruments that, when used together with a Global Navigation Satellite Systems (GNSS) receiver, help improve the performance of GNSS navigation solutions in certain conditions (i.e., low satellite visibility). Current GNSS receivers...

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Main Authors: Enric Fernández, David Calero, M. Eulàlia Parés
Format: Article
Language:English
Published: MDPI AG 2017-02-01
Series:Sensors
Subjects:
Online Access:http://www.mdpi.com/1424-8220/17/2/370
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spelling doaj-0cbd4fdf88b1493fa8617293b3a9c2be2020-11-24T21:17:59ZengMDPI AGSensors1424-82202017-02-0117237010.3390/s17020370s17020370CSAC Characterization and Its Impact on GNSS Clock Augmentation PerformanceEnric Fernández0David Calero1M. Eulàlia Parés2Centre Tecnològic de Telecomunicacions de Catalunya (CTTC/CERCA), Parc Mediterrani de la Tecnologia (PMT), Building B4, Av. Carl Friedrich Gauss 7, 08860 Castelldefels, SpainCentre Tecnològic de Telecomunicacions de Catalunya (CTTC/CERCA), Parc Mediterrani de la Tecnologia (PMT), Building B4, Av. Carl Friedrich Gauss 7, 08860 Castelldefels, SpainCentre Tecnològic de Telecomunicacions de Catalunya (CTTC/CERCA), Parc Mediterrani de la Tecnologia (PMT), Building B4, Av. Carl Friedrich Gauss 7, 08860 Castelldefels, SpainChip Scale Atomic Clocks (CSAC) are recently-developed electronic instruments that, when used together with a Global Navigation Satellite Systems (GNSS) receiver, help improve the performance of GNSS navigation solutions in certain conditions (i.e., low satellite visibility). Current GNSS receivers include a Temperature Compensated Cristal Oscillator (TCXO) clock characterized by a short-term stability (τ = 1 s) of 10−9 s that leads to an error of 0.3 m in pseudorange measurements. The CSAC can achieve a short-term stability of 2.5 × 10−12 s, which implies a range error of 0.075 m, making for an 87.5% improvement over TCXO. Replacing the internal TCXO clock of GNSS receivers with a higher frequency stability clock such as a CSAC oscillator improves the navigation solution in terms of low satellite visibility positioning accuracy, solution availability, signal recovery (holdover), multipath and jamming mitigation and spoofing attack detection. However, CSAC suffers from internal systematic instabilities and errors that should be minimized if optimal performance is desired. Hence, for operating CSAC at its best, the deterministic errors from the CSAC need to be properly modelled. Currently, this modelling is done by determining and predicting the clock frequency stability (i.e., clock bias and bias rate) within the positioning estimation process. The research presented in this paper aims to go a step further, analysing the correlation between temperature and clock stability noise and the impact of its proper modelling in the holdover recovery time and in the positioning performance. Moreover, it shows the potential of fine clock coasting modelling. With the proposed model, an improvement in vertical positioning precision of around 50% with only three satellites can be achieved. Moreover, an increase in the navigation solution availability is also observed, a reduction of holdover recovery time from dozens of seconds to only a few can be achieved.http://www.mdpi.com/1424-8220/17/2/370CSACcalibrationclock augmentationGNSSatomic clocknavigationsteering
collection DOAJ
language English
format Article
sources DOAJ
author Enric Fernández
David Calero
M. Eulàlia Parés
spellingShingle Enric Fernández
David Calero
M. Eulàlia Parés
CSAC Characterization and Its Impact on GNSS Clock Augmentation Performance
Sensors
CSAC
calibration
clock augmentation
GNSS
atomic clock
navigation
steering
author_facet Enric Fernández
David Calero
M. Eulàlia Parés
author_sort Enric Fernández
title CSAC Characterization and Its Impact on GNSS Clock Augmentation Performance
title_short CSAC Characterization and Its Impact on GNSS Clock Augmentation Performance
title_full CSAC Characterization and Its Impact on GNSS Clock Augmentation Performance
title_fullStr CSAC Characterization and Its Impact on GNSS Clock Augmentation Performance
title_full_unstemmed CSAC Characterization and Its Impact on GNSS Clock Augmentation Performance
title_sort csac characterization and its impact on gnss clock augmentation performance
publisher MDPI AG
series Sensors
issn 1424-8220
publishDate 2017-02-01
description Chip Scale Atomic Clocks (CSAC) are recently-developed electronic instruments that, when used together with a Global Navigation Satellite Systems (GNSS) receiver, help improve the performance of GNSS navigation solutions in certain conditions (i.e., low satellite visibility). Current GNSS receivers include a Temperature Compensated Cristal Oscillator (TCXO) clock characterized by a short-term stability (τ = 1 s) of 10−9 s that leads to an error of 0.3 m in pseudorange measurements. The CSAC can achieve a short-term stability of 2.5 × 10−12 s, which implies a range error of 0.075 m, making for an 87.5% improvement over TCXO. Replacing the internal TCXO clock of GNSS receivers with a higher frequency stability clock such as a CSAC oscillator improves the navigation solution in terms of low satellite visibility positioning accuracy, solution availability, signal recovery (holdover), multipath and jamming mitigation and spoofing attack detection. However, CSAC suffers from internal systematic instabilities and errors that should be minimized if optimal performance is desired. Hence, for operating CSAC at its best, the deterministic errors from the CSAC need to be properly modelled. Currently, this modelling is done by determining and predicting the clock frequency stability (i.e., clock bias and bias rate) within the positioning estimation process. The research presented in this paper aims to go a step further, analysing the correlation between temperature and clock stability noise and the impact of its proper modelling in the holdover recovery time and in the positioning performance. Moreover, it shows the potential of fine clock coasting modelling. With the proposed model, an improvement in vertical positioning precision of around 50% with only three satellites can be achieved. Moreover, an increase in the navigation solution availability is also observed, a reduction of holdover recovery time from dozens of seconds to only a few can be achieved.
topic CSAC
calibration
clock augmentation
GNSS
atomic clock
navigation
steering
url http://www.mdpi.com/1424-8220/17/2/370
work_keys_str_mv AT enricfernandez csaccharacterizationanditsimpactongnssclockaugmentationperformance
AT davidcalero csaccharacterizationanditsimpactongnssclockaugmentationperformance
AT meulaliapares csaccharacterizationanditsimpactongnssclockaugmentationperformance
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