Positioning with medium frequency R‐Mode

Grundhöfer, Lars; Rizzi, Filippo Giacomo; Gewies, Stefan; Hoppe, Michael; Bäckstedt, Jesper; Dziewicki, Marek; Galdo, Giovanni Del

doi:10.1002/navi.450

Cited by 11 publications

(17 citation statements)

References 17 publications

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“…A 1 and A 2 were chosen differently to reflect possible imperfections of the R-Mode signals. In general, the amplitudes match our observation in the testbed [19]. The results of this comparison are shown in Fig.…”

Section: Efficient Estimatorsupporting

confidence: 85%

“…1. These signals are already available in the R-Mode Baltic testbed [22] and were used for initial positioning in the Baltic Sea, using the Fast Fourier Transform (FFT) as the maximum likelihood estimator for the different phases [19].…”

Section: Signal Descriptionmentioning

confidence: 99%

“…Extending the observation time to achieve the best performance is not always possible. However, the current R-Mode receiver implementation relies on the fast Fourier transform [19] as an estimator, due to its computational efficiency. To further improve this suboptimal approach while retaining its benefit of computational efficiency, we suggest using windowing to decrease the variance for short observation times.…”

Section: Windowingmentioning

confidence: 99%

“…For R-Mode as an application, this can be neglected, since the bias caused by different effects is determined after the phase estimation. The overall bias of DSP and hardware delays will be estimated during the receiver calibration and subtracted for ranging [19].…”

Section: Prefilteringmentioning

confidence: 99%

“…The paper starts with a short description of the signal in Section II. We show in section III that the recently used maximum likelihood estimator [19] is an efficient estimator for our problem. In Section IV, we further investigate how we can improve the estimator with windowing for short observation times.…”

Section: Introductionmentioning

confidence: 99%

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Phase Estimation of Single Tones Next to Modulated Signals in the Medium Frequency R-Mode System

et al. 2022

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Position, navigation, and timing information are critical to today's infrastructures; as a result, the possibility of estimating ranges is being explored in more and more radio systems. One way to achieve this is to extend the modulation with time-synchronised aiding carriers and to estimate their phase at the receiver side. In this paper, we present two ways to minimise the negative influence of the modulation on the phase estimation. We show that the classical maximum likelihood estimator is still an efficient estimator for our problem, using a medium-frequency R-Mode signal as an example, and is therefore used in receiver designs. We then describe two possible ways to precondition the signal to increase the accuracy for short observations. As a first approach, we describe how window functions can positively change the signal-tonoise ratio for our estimation. As a second approach, we show the use of a narrowband bandpass filter. Finally, we show that these approaches, applied to real measurements, improve the variance of the estimate by up to two orders of magnitude.

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Section: Efficient Estimatorsupporting

confidence: 85%

Section: Signal Descriptionmentioning

confidence: 99%

Section: Windowingmentioning

confidence: 99%

Section: Prefilteringmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Phase Estimation of Single Tones Next to Modulated Signals in the Medium Frequency R-Mode System

et al. 2022

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Enhancement of MF R-Mode ranging accuracy by exploiting measurement-based error mitigation techniques

Rizzi¹,

Hehenkamp²,

Grundhöfer³

et al. 2022

WMU J Marit Affairs

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Nowadays, the maritime sector strongly relies on global navigation satellite systems (GNSS) for the provision of position, navigation, and timing (PNT) information. The standard functionality of several ships’ bridge instruments depends on such information, which becomes critical to have a safe and reliable navigation. Nevertheless, the possibility of GNSS outages combined with unintentional and intentional interference to GNSS signals, which have been increasing over the last years, can severely threaten the nominal activity of the crew onboard of vessels. For these reasons, alternative position, navigation, and timing (APNT) systems become fundamental in order to provide operational continuity. R(anging)-Mode is a terrestrial alternative system to GNSS for the maritime domain. In one of its possible implementation, it exploits synchronized medium frequency (MF) signals transmitted by maritime radio beacons. In the MF band, the radio waves are attenuated and distorted by the change of electrical properties of the ground along the propagation path. Moreover, these signals are affected by terrain elevation changes and large metallic infrastructures which induce an overall loss in the accuracy of the system. In this paper, we propose a mitigation technique based on the estimation of these additional error sources by using in-field range measurements. The theoretical details are explained in depth and the technique is validated with real data gathered on a measurement campaign. A clear and significant performance improvement is achieved on the range accuracy when the proposed approach is applied.

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A Software Framework for the Parallel Computation of Ground Wave Propagation Delay and Attenuation

Hehenkamp,

Rizzi,

Grundhöfer

et al. 2023

2023 24th International Conference on the Computation of Electromagnetic Fields (COMPUMAG)

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Positioning with medium frequency R‐Mode

Cited by 11 publications

References 17 publications

Phase Estimation of Single Tones Next to Modulated Signals in the Medium Frequency R-Mode System

Phase Estimation of Single Tones Next to Modulated Signals in the Medium Frequency R-Mode System

Enhancement of MF R-Mode ranging accuracy by exploiting measurement-based error mitigation techniques

A Software Framework for the Parallel Computation of Ground Wave Propagation Delay and Attenuation

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