R-Mode – terrestrial navigation for maritime users

Transport of passengers as well as cargo has become a key-issue for our modern economy. Especially the management of cargo traffic has become a fragile backbone for an economy that is based on “just-in-time” delivery and closely linked manufacturing processes. The International Maritime Organization (IMO) identified a gap in the provision of resilient navigation data for safe navigation of vessels sailing the world’s seas. Maritime transport has increased to an extent, where traffic regulations and restrictions have become essential to provide safe voyage on the “highways of the seas”. High traffic densities in demanding waters, like the narrow straits and vessel traffic separation schemes in shallow waters raise a demand and an increase in the requirements on reliable navigation data on-board of vessels for safe navigation. Furthermore, today’s world is facing acts of cybercrime on a daily basis and terrorism as well as growing tensions between states. All this is resulting in potential harmful threats against human life, the economy and for environmental pollution as well, when tempering with navigation systems is not detected or prevented. Current reports on Global Navigation Satellite System (GNSS) disturbances in the eastern Baltic and Skagen show the vulnerability of transport modes that rely solely on GNSS. To increase the resilience of the maritime transport and reduce the risk of using misleading information, national maritime administrations and service providers in the Baltic Sea region and worldwide are looking for solutions to identify and mitigate GNSS disruptions or deceptions. Following the IMO International Convention for the Safety of Life at Sea (SOLAS), national maritime administrations are requested to investigate and in future provide means to ensure provision of resilient Position, Navigation and Timing (PNT). An opportunity is to use alternative navigation systems in conjunction with GNSS to achieve that. The Baltic Sea is a test area for a terrestrial navigation system, known as R-Mode, which reuses maritime shore infrastructure for the synchronized transmission of ranging signals. They are implemented as two additional carrier signals to the continuous medium frequency broadcast of maritime radio beacons and as new designed R-Mode one slot message broadcast of the Very high frequency Data Exchange System (VDES) base stations which will replace base stations of the Automatic Identification System (AIS) in the future. Since 2017, two projects implemented an R-Mode test bed in the southern Baltic Sea. Eight maritime radio beacons were equipped with R-Mode ready signal modulators and accurate clocks. This enabled R-Mode signal reception in a wide area of the southern Baltic Sea. Static and dynamic position experiments showed in agreement with the theory that accuracies of 10 to 30 m can be achieved at day-time or when stations in close distance are used. The performance at night-time is especially dependent on the distance of the receiver to the transmitter. The ranging performance is significantly reduced for larger distances due to interference of the main propagation path as ground wave with the sky wave. As an indicator for sky-wave induced signal degradation a change of the probability density function from Gauss to Laplace tape for the range estimation was observed. This might be usable for the design of future positioning algorithms. Beside the permanent R-Mode radio beacon implementation also experiment with VDES were conducted in two location at the Baltic Sea and on a lake in Germany. It shows the feasibility of that approach and the usability of the standardized R-Mode message for ranging and positioning. The experiments suggest that positioning with VDES R-Mode can be achieved with accuracies of 10 m in areas with good reception conditions. The maritime infrastructure which is used for the transmission of R-Mode ranging signals was optimized to provide differential GNSS data within an average radius of 250 km to the GNSS onboard receiver or to exchange data between ship and shore over distances of about 20 nm (varies very much) using AIS/VDES. Therefore, the geometry is usually not optimized for R-Mode. But it can be compensated by an increasing number of transmitters or preferably use VDES and radio beacon R-Mode transmitters at the same time. International cooperation between the Baltic Sea states can enable terrestrial navigation for maritime users in coastal waters for manageable costs

Taxation and market power

"We analyze the incidence and welfare effects of unit sales taxes in experimental monopoly and Bertrand markets. We find, in line with economic theory, that firms with no market power are able to shift a high share of a tax burden on to consumers, independent of whether buyers are automated or human players. In monopoly markets, a monopolist bears a large share of the burden of a tax increase. With human buyers, however, this share is smaller than with automated buyers as the presence of human buyers constrains the pricing behavior of a monopolist." (author's abstract)"Dieser Artikel untersucht Inzidenz- und Wohlfahrtseffekte einer Mengensteuer in experimentellen Monopol- und Bertrand-Märkten. Im Einklang mit der ökonomischen Theorie sind Firmen ohne Marktmacht in der Lage, einen großen Anteil der Last einer Steuererhöhung an die Konsumenten weiterzugeben. Dies gilt unabhängig davon, ob die Käufer simuliert sind oder die Kaufentscheidungen durch reale Käufer getroffen werden. In Monopolmärkten trägt der Monopolist einen großen Anteil der Last einer Steuererhöhung. Werden die Kaufentscheidungen durch reale Käufer getroffen, ist dieser Anteil jedoch kleiner als mit simulierten Käufern, da reale Käufer im Experiment das Preissetzungsverhalten des Monopolisten einschränken." (Autorenreferat

Characterization of a Transmitter in a Medium Frequency Maritime Terrestrial Navigation System

Due to the worldwide recognition of increased jamming and spoofing events, which threaten the usability of global navigation satellite systems (GNSS), positioning systems using signals of opportunity are gaining importance as backup systems. Especially for maritime usage, a terrestrial system called Ranging-Mode (R-Mode) is under development. Among other signals, it utilizes the maritime medium frequency broadcasts of the differential GNSS (DGNSS) service. Currently, the estimation of phase in a time continuous medium frequency signal is used to determine the distance between transmitter and receiver. Here, the delay of a transmitter on the signal phase is of great interest, since it directly affects the performance of the R-Mode system. In this paper, the influence of a medium frequency power amplifier is characterized as part of the transmitter chain. The aim is to give the operators of DGNSS stations the possibility to characterize their station themselves when the R-Mode system is operational. Therefore, widely used measuring instruments are utilized, rather than using well-known cost-intensive techniques like phase delay measurements. A simple setup with different evaluation methods that fit this requirement is presented. Furthermore, it is capable of measuring the absolute time delay. The presented workflow was tested on an amplifier with output power of 100W at the transmitter station near Koblenz, Germany

Anti-Mullerian hormone as a predictor of IVF outcome

Serum anti-Müllerian hormone (AMH) concentration and antral follicle count (AFC) are two increasingly popular static measures used to predict ovarian reserve prior to IVF treatment. While they have been shown to be good predictors of oocyte yield during ovarian stimulation, their status as indicators of oocyte quality and pregnancy rates is currently uncertain. The present study measured baseline concentrations of serum AMH and FSH, and AFC from 126 women undergoing IVF treatment. These data were then related to IVF outcomes. As expected, patients with lower serum AMH and AFC produced a significantly (P < 0.001) lower number of oocytes compared with patients with higher serum AMH/AFC. Fertilization rates in patients with lower serum AMH were significantly inferior compared with patients with higher serum AMH, irrespective of whether IVF (P = 0.043) or intracytoplasmic sperm injection (P = 0.006) was used to achieve fertilization. These low AMH patients yielded fewer oocytes, had lower fertilization rates, generated fewer embryos, and had a higher incidence of miscarriage during fresh transfers, ultimately culminating in a halving of the pregnancy rate per IVF cycle compared with the high AMH group.Dharmawijaya N Lekamge, Michael Barry, Michele Kolo, Michelle Lane, Robert B Gilchrist, Kelton P Tremelle