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An Overview About the Physical Layer of the VHF Data Exchange System (VDES)
Abstract
The AIS (Automatic Identification System) has become one of the most popular maritime communications systems in the world, allowing the data exchange and identification among vessels to avoid collisions at sea. In spite of the uncountable virtues of this system, security and channel saturation challenges have motivated the development of a new version of the AIS, called VDES (VHF Data Exchange System). This system improves the AIS robustness and includes additional services for a wider range of applications. In this paper, a description of the physical layer of the VDES is presented and the most relevant differences between the AIS and VDES are analysed. Moreover, the main challenges that the VDES has to face in the next years are also described and analysed, including a vision about the future applications that will be supported by this system.
... Thus, the International Association of Lighthouse Authorities (IALA) and its members started developing the VHF Data Exchange System (VDES) to offload the data traffic of the AIS and to provide new capabilities, such as ship-to-ship messaging [8] and distribution of ice charts to aid navigation [9]. The VDES standard was approved in 2015 and is formed by three services: AIS, Application Specific Messages (ASM) and VHF Data Exchange (VDE) [10], [11]. The ASM channels are used to send predefined messages to report weather conditions, safety and navigational purposes [12]. ...
Maritime activity in the Arctic is increasing, triggering a need for better communication infrastructure. With limited terrestrial infrastructure available, satellite services are essential for distributing maritime safety information, such as ice and weather information, navigational augmentation data, and basic communication to vessels operating in the vulnerable Arctic environment. The VHF Data Exchange System (VDES) is a new communication system for ships, extending the successful Automatic Identification System (AIS). VDES has a satellite component (VDE-SAT) which will extend the terrestrial-based coastal coverage to global coverage. Measurements and analysis of the in-orbit radio environment are needed to improve the robustness and reliability of the VDE-SAT system. Knowledge and understanding of the in-orbit interference will allow the development of appropriate interference mitigation techniques. This paper presents preliminary in-orbit measurement results and analysis of the radio environment in the VDE-SAT frequencies in the 157.2875 - 157.3375 MHz band. The measurements were carried out using the VDE-SAT payload on-board the Norwegian NorSat-2 satellite. We analyze the time-frequency characteristics of interference by studying two types of statistics on the raw in-phase and quadrature samples: the general temporal dynamic of the interference, characterised using the Local Mean Envelope (LME) for different averaging window lengths; and the interference duration and periodicity. Both these views play a role when choosing suitable countermeasures to get robust communications. The coefficient of variation on the LME is used to study the dispersion. Data from two measurement campaigns over the Arctic area from May 2021 are analysed using these two methods, and the initial results are presented.
... In addition, the LR-AIS uses the same modulation scheme as the AIS (GMSK), the ASM uses a π/4-QPSK scheme, the VDE-TER can use π/4-QPSK, 8PSK or 16QAM schemes, and the VDE-SAT uses BPSK, QPSK or 8PSK modulation (in downlink) and QPSK, OQPSK and 16APSK (in uplinks) [9]. The VDE-TER service can achieve transmission rates 32 times higher than the AIS [10]. Despite the positive aspects offered by the VDES, there are still some technical issues to be resolved. ...
With the development of science and technology, traffic perception, communication, information processing, artificial intelligence and the shipping information system have become important in supporting the realization of intelligent shipping transportation. Against this background, the Internet of Vessels (IoV) is proposed to integrate all these advanced technologies into a platform to meet the requirements of international and regional transportations. The purpose of this paper is to analyze how to benefit from the Internet of Vessels to improve the efficiency and safety of shipping, and promote the development of world transportation. In this paper, the IoV is introduced and its main architectures are outlined. Furthermore, the characteristics of the Internet of Vessels are described. Several important applications that illustrate the interaction of the Internet of Vessels’ components are proposed. Due to the development of the Internet of Vessels still being in its primary stage, challenges and prospects are identified and addressed. Finally, the main conclusions are drawn and future research priorities are provided for reference and as professional suggestions for future researchers in this field.
This work presents an overview of the radio interface of VHF Data Exchange System (VDES), which is currently on its way to become an ITU standard supported by International Association of Marine Aids to Navigation and Lighthouse Authorities (IALA). VDES includes the already existing collision avoidance tracking system Automatic Identification System (AIS) and the messaging system Application Specific Messages (ASM). Additionally, a new third component for digital maritime communications of any kind, named VHF Data Exchange (VDE) is included. On the one hand, there is a traditional terrestrial component, on the other hand, a satellite communication link is also envisioned partly by the same spectrum usage. In this article, focus is given towards the technical design aspects and challenges of this hybrid communications transmission scheme.
The Automatic Identification System (AIS) is the emerging system for automatic traffic control and collision avoidance services in the maritime transportation sector. It is one of the cornerstone systems for improved marine domain awareness and is embedded in e-navigation, e-bridging, and autonomous ships proposals. However, AIS has some security vulnerabilities that can be exploited to invade privacy of passengers, to launch intentional collision attacks by pirates and terrorists, etc. In this work, we explore how Identity-Based Public Cryptography and Symmetric Cryptography may enhance the security properties of the AIS.
We live in an ever-changing environment where there is a vital need for persistent monitoring of human activities; whether it is for security, safety, economic or environmental purposes. Our oceans are no exception and may even be the region of our globe that is most at risk. Unbeknownst to many, there is limited visibility and awareness of maritime activity beyond 40-50 nautical miles from our coastline. Shore-based technologies have limited range, space-based radar and other sensors have limited coverage, and marine patrol and synthetic aperture radar (SAR) assets are too costly to deploy over a wide area. Nevertheless, the ability to know the who, what and when of any transiting vessel near our coastline or in the open ocean is a critical piece of intelligence - whether it is to counter piracy, prevent illegal drug smuggling, reduce response time for search and rescue operations, combat illegal fishing, monitor marine protected areas (MPAs), etc.
The Automatic Identification System (AIS) standard is encompassed within the Global Maritime Distress and Safety System (GMDSS), in force since 1999. The GMDSS is a set of procedures, equipment and communication protocols designed with the aim of increasing the safety of sea crossings, facilitating navigation and the rescue of vessels in danger. The use of this system is increasingly attractive not only to security issues but to potentially create intelligence products throughout the added-value information that this network can transmit from ships on real time (identification, position, course, speed, dimensions and flag among others). Within the marine electronics market, commercial receivers implement this standard, and allow users to access vessel-broadcasted information if in the range of coverage. In addition to satellite services, users may request actionable information from private or public AIS terrestrial networks where real-time feed or historical data be accessed from its nodes. This paper describes the configuration of an AIS receiver based on a modular design. This modular design facilitates the evaluation of specific modules. Also, a better understanding of the standard and the possibility of changing hardware modules to improve the performance of the prototype. Thus, the aim of this paper is to describe the system's specifications, its main hardware components, and to present educational didactics on the set-up and use of a modular and terrestrial AIS receiver. The latter for academic purposes and in undergraduate studies such as electrical engineering, telecommunications and maritime studies.
Vessel-source air pollution may have a major impact on the marine environment and ecosystem. In this study, a method based on vessel activity intensity was adopted to estimate the emission of air pollutants generated by the consumption of fuel oils from merchant vessels in the Port of Kaohsiung in 2013. The vessel activities were determined by using the vessel automatic identification system (AIS) to track vessel traffic and position and to calculate the corresponding emission of air pollutants based on three types of vessel activities: sailing, maneuvering, and hotelling. The results were then used to explore management strategies for controlling vessel-source emissions of air pollutants.
Demands on security, safety, and environmental protection in worldwide shipping are steadily increasing. Shipboard broadcast transponders based on the Automatic Identification System (AIS) can be easily detected close to coastal or waterway areas. Satellite-based AIS receivers detect globally but are limited in high-density traffic areas. This paper investigates the challenges and performance of AIS detection on aircraft at altitudes between 8 500 m and 10 000 m. During flight trials over sea and land, AIS signals were recorded. Post-processing of the recorded data allows the evaluation but also faces challenges due to the nature of overlapping AIS signals at the aircraft. A comparison of detected signals at the aircraft with received AIS signals on the ground is given, including the evaluation of the reception footprint of the aircraft. Finally, a concept for worldwide AIS detection via airliners is presented. The study shows the potential for global complementary surveillance coverage via airliner-based AIS detection.
Exhaust emissions cause air pollution and climate change. The exhausts of shipboard fuel combustion are equally damaging particularly, so close to the environmentally sensitive mainland and island coasts, as well as at ports due to their urbanized character. This paper estimates, for the first time, exhaust pollutants related to cruise and ferry operations in Las Palmas Port and, in an island context. Emission assessment is based on a full bottom-up model and messages transmitted by the Automatic Identification System during 2011. Results are described as a breakdown of NOx, SOx, PM2.5, CO and CO2, according to ship classes, operative type and time, providing valuable information to environmental policy makers in port-city areas and islands under similar conditions. It is generally concluded that vessel traffic and passenger shipping in particular are a source of air pollution in Las Palmas Port. Emission maps confirm location of hot spots in quays assigned for cruise and ferry operations. Policy recommendations encourage regular monitoring of exhaust emissions and market-based incentives supported by details on polluting and operative profiles. On the other hand, feasibility studies are suggested for automated mooring, LNG bunkering facilities and also shore-side energy services, prioritizing berthing of shipping sectors (or sub-sectors) with the highest share of exhaust emissions once their local effects have been confirmed by a dispersion, exposure and impact assessment.
The AIS(Automatic Identification System) has been widely used for ship safety at sea over the last 10 years. The AIS traffic load at VDL(VHF Data Link) has been continuously increased. As the traffic load at VDL increases, the quality of AIS service may be deteriorated. In the previous research, the AIS traffic has been analyzed in the major ports of Korea, and its problem due to traffic overload has been suggested. However, no solutions has been given so far. In this paper, the method of autimatically controlling the VDL traffic at AIS base station is represented.
This paper presents the performance analysis and system trade-offs of a satellite-based AIS (Automatic Identification System) system. Such a system represents a global monitoring extension of the current terrestrial AIS for ship identification and localization and is being currently investigated by several commercial and governmental entities. Operation of a constellation of LEO satellites targeting AIS detection is currently foreseen to be started within the next few years. In this paper, the feasibility of the concept is proven by deriving the probability of ship detection over key geographical areas like the North Atlantic Ocean. Key system and sub-system parameters and components are analyzed including the satellite orbit, the satellite antenna design and the on-board receiver. Their impact to the overall system performance is presented.
Adaptive coded modulation (ACM) is a promising tool for increasing the spectral efficiency of time-varying mobile channels while maintaining a predictable bit-error rate (BER). An important restriction in systems with such a transmission scheme is that the transmitter needs to have accurate channel-state information (CSI). Earlier analysis of ACM systems usually assumes that the transmitter has perfect knowledge of the channel or that the CSI is accurate but outdated. In this paper, we investigate the effects of predicting the CSI using a linear fading-envelope predictor in order to enhance the performance of an ACM system. For the case in which multidimensional trellis codes are used on Rayleigh-fading channels, we obtain approximative closed-form expressions for BER and average spectral efficiency. Numerical examples are given for the case of Jakes correlation profile and maximum a posteriori-optimal predictor coefficients.
VDESAT-A new maritime communications system
- T Eriksen
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e-Navigation and future trend in navigation
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