There have been many large-scale accidents involving international maritime transportations causing environmental disasters. To prevent such terrible accidents on the sea, the International Maritime Organization has introduced Maritime Safety Management System. Today not only the concern for maritime safety but also the ever getting larger and faster ships to handle increasing volume of sea freight is posing more challenges for the navigation of the ships. To respond to this, 7 countries including the UK, the United States and Japan proposed development of strategic vision for e-Navigation with new technologies using the existing equipment and electronic means in the 81st meeting of the Maritime Safety Committee of IMO and the Committee decided to develop the strategy by 2008.
Top priority in developing such e-Navigation strategy is given to reducing maritime mistakes to prevent accidents and pollution on the sea and the communications work group is focusing on developing 3 core element technologies for the e-Navigation and those are building integrated bridge system, controlling ship traffic and providing comprehensive data from the shore, and enabling seamless authenticated information infrastructure for communications on the ships, between the ships, ships to shore, between parties on shore and between multiple related parties.
This paper is to summarize systematically the concept of `e-Navigation and the status of work that has been progressed up to now and propose a ship to shore communications network on the basis of the analysis of the issues found between the existing wireless communications system and e-Navigation` system for the purpose of developing the most crucial element in the e-Navigation, which is communications network covering both land and sea.
Strategic development of communications network technology for e-Navigation involves identifying various locational information required on shore and sea, conducting research on the way to collect and utilize the information, reviewing existing wireless cellular communications technology covering shore and sea, and determine the differences between shore communications and maritime communications. Through such study, we have identified the issues with satellite or radio systems which can handle very restrictive volume of communications and mobile wireless system, and looked into the possibility of applying Wibro system, developed in Korea and became one of the land cellular communications systems already adopted as a global standard, to ship to shore communications.
Current terrestrial Wibro system requires repeaters installed between the base stations and mobile stations, and handover technology for repeaters is used to overcome the problem of short coverage of the wavelengths. However on the sea, it is difficult to install repeaters, challenging the deployment of Wibro technology. This paper proposes a feasible solution to overcome the coverage limitations of Wibro technology through review on various technologies.
The biggest difficulty in using Wibro system on the ocean, which was developed by Korea and adopted as an international cellular communications standard, is to extend the coverage. On the ocean, unlike on the land, output of the base stations and mobile stations need to be enhanced and sensitivity of antennas should be amplified to improve the gains of the antennas and optimize the frame structure of Wibro system. Through the research efforts, we wanted to learn the maximum possible distance of coverage extension and usable coastal areas in Korea to verify the applicability of Wibro for e-Navigation system linking the ships to shore.
This paper studies Wibro frame structure to come up with the way to extend the maximum coverage area and learned that the maximum coverage can be increased up to 19.7Km on the sea. Based on this, limitations on mobile station battery life and output and antenna can be easily removed on the sea by growing output of mobile station and gains of antennas, from 0.2W to 1.0W and from 3dB to 9dB respectively to extend the coverage distance from 5.4Km to 17.1Km according to the analysis by Cost231-Walfisch-Ikegami interpretation model of radio propagation. Therefore it is demonstrated that coverage extension can be achieved if performance of mobile station is upgraded with the improved system design, and the elevated mobile station output and antenna gains.
The study result confirms that Wibro can be utilized for e-Navigation in coastal areas as maritime wireless communications technology to provide real time broadband information with satisfying level of reliability and security. It is also hoped that the paper paves the way for more brisk research and development activities in the field of required communications system to link the land and the sea and to make our Wibro technology to lead such field.