The aim of this paper is to discuss a connection between the geometric configuration and positioning accuracy in wireless networks exploiting the TDOA technique. At the beginning, a simulation model of TDOA localization technique is described. We use the Taylor series expansion and least square fit method to estimate the terminal's position. In this part we also derive a statistical model for calculating the geometric dilution of precision (GDOP), which is here a variable reflecting geometric quality with respect to the hyperbolic lateration. The two dimensional root mean square (RMS) error metric is also presented in order to make necessary accuracy calculations. We then describe an impact of the bad configuration of measurement units on the positioning accuracy. Basing on simulation results, the TDOA efficiency for different time errors and geometric circumstances is presented. Finally, we show an empirical solution for decreasing the bad geometry effect. The accuracy is improved thanks to the additional measurement units placed in the good geometry conditions.

This article presents the work conducted in the R-Mode Baltic project, which aims to launch the R-Mode demonstrator in the Baltic Sea area. The article describes the concept of the Automatic Identification System (AIS) infrastructure and VHF Data Exchange System (VDES) signal utilization with respect to their potential role in the future R-Mode System. It also contains the analysis of the distance determination accuracy in the designed system based on calculation of the correlation between the received signal and the known transmitted signal, as well as the achievable ranges for various system configurations. Additionally, the paper discusses the implementation of the test-bed transmitter and receiver, the methodology of measurement campaigns carried out in the Baltic Sea on the Gdynia-Karlskrona route, as well as the obtained results. The collected measurement results were thoroughly analyzed and compared with theoretical values. The summary contains conclusions, as well as the plans for the next phase of measurement research.

In the paper, the measurement and simulation results of the VDES (VHF Data Exchange System) terrestrial component are discussed. It is anticipated that VDES will be one of the major solutions for maritime communications in the VHF band and its performance will be sufficient to fulfill the requirements of the e-navigation applications. The process of the VDES standardization (ITU R, IALA) has not been officially completed yet, but substantial amount of technical information about the future system’s terrestrial component (VDE-TER) is already available. The paper is divided into three general parts: (a) theoretical presentation of the system’s physical layer and the radio channels applicable to VDES, (b) simulation results (BER, BLER, channel delay between two propagation paths and its influence on bit rates) and (c) measurement results (useful ranges, BER). It turned out that in real maritime conditions, the VDES system can offer ranges between 25 and 38 km for the configurations assumed during the measurement campaign. Those results are generally compliant with the theoretical data in the line-of-sight conditions. In the NLOS scenarios, where fading becomes the dominant phenomenon, the discrepancies between the measurements and the theoretical results were more significant. The obtained results confirmed that VDES provides a large coding gain, which significantly improves the performance of data transmission and increases the bit rate compared to the existing maritime radiocommunication solutions. It should be noted that the results presented in the article were used by the IALA while developing the current version of the VDES specification.

This article discusses several aspects related to the modeling of the radio channel in the wind farm propagation environment. The first part of the article is filled with the analysis of the ITU-R BT.1893-1 model, which—as will be shown—is also applicable to systems operating in the VHF and UHF bands. The conducted measurement campaign makes it possible to model a radio channel for VHF operating systems in the wind farm propagation environment. Thanks to the obtained results, the authors propose the VHF radio channel model for that environment. Using the software implementation of this model, the authors carry out a detailed simulation analysis of the impact of wind turbines on radio systems operating in the VHF band. The main motivation for this work is the growing importance of the offshore wind energy in general, numerous investments in that area in Poland, and the lack of existing mathematical models regarding the wind farms’ impact on the VHF systems. The VHF band is of special interest here, as this part of the spectrum is utilized by numerous marine administration and border protection radio systems, which can be adversely affected by the wind turbines (due to interference and/or radio shadowing).

The following paper discusses several aspects connected with the wind farms’ impact on radiocommunication systems. The first part of this article is filled with the analysis of the ITU-R BT.1893 model, which was originally created for the analysis of the interaction between the wind turbines and digital TV receivers in the UHF band. A measurement campaign carried out by the authors confirmed that this model is also applicable for the lower, maritime VHF band. Utilizing the software implementation of this model, the authors conducted a thorough simulation analysis of the wind turbines’ influence on radio systems working in both VHF and UHF bands. The results of these simulations are presented and discussed in the second part of the paper.

Technical Notes - The article presents the concept of the hybrid communication system for the purpose of maritime applications. The main idea of this system is that it will utilize the seamless roaming concept, which means the communication link at sea will be established automatically (and seamlessly for the user), using many possible communication techniques (cellular, LTE, Wi-Fi, VDES, etc.) which will be selected depending on the current conditions of the radio channel and the requirements and preferences of the user. The paper will introduce the general architecture of the system, the concept of the maritime cloud and the seamless roaming, including the way the latter will be implemented in the system. The authors will also briefly introduce the proposed test-bed of the system’s on-board device. The system presented in the article is one of the major topics of the EfficienSea 2 project (co-funded from the ‘Horizon 2020’ programme) in which the authors of the paper participate.