Research And Design Of A New-Style AIS

The Universal Ship-borne Automation Identification System (AIS) has been developing rapidly since it has been invented. Especially, after being formulated with norms by International Maritime Organization, International Telecommunications Union, International Association of Lighthouse Authorities, and International Electro-technical Commission, the Universal Ship-borne Automation Identification System has been one of the essential equipments of digitalized navigation.But the Ship-borne Universal Automation Identification cannot meet need of some vessels. These vessels cannot exchange messages between universal vessels via the Universal Ship-borne Automation Identification System, and compared with ordinary vessels they voyages on a more complex environment. For this, a new Ship-borne Automation Identification System which can achieve the goal of Anti-jamming communications, data encryption and flexible communication control is researched and designed in this dissertation.With the modulation and demodulation of the Direct-Sequence Spread Spectrum, the new AIS can extend spectrum spread of the signal to a wider band, which ensures anti-jamming efficiently. Meanwhile enough Spread Spectrum Sequence is needed to achieve the aim of flexible anti-jamming capacity. The acquisition of the Spread Spectrum Code adopts the way of Matched Filter with comparatively high speed to realize quick acquisition.The communication management of the new AIS is more flexible. It extends the scope of the message report rate via the LIDMA; enhances the ability of allocation by base station via the two ways of slot allocation and reporting rate assignment; and the new AIS still reduce the category of messages. The new AIS consists of four access protocols:RATDMA, ITDMA, LITDMA, and SOTDMA. Working modes for Transceiver are made up of Monitor data link, network entry, first frame, slot allocation mode, reporting rate assigned mode, autonomous and continuous mode, mode of reporting rate transmission, enquiry mode, and message mode.The new AIS not only applies the modulation and demodulation of Direct-Sequence Spread Spectrum to keeping secrets on information transmission, but also resorts to encryption and decryption of stream cipher to keep secrets on information source. In the new AIS, the stream cipher builder produces key stream by nonlinear combination of the three LFSRs that produce pseudo-random sequence.The new AIS can apply to the severe condition with heavy electromagnetic interference and assure successful transmission of information. Even though the illegal receivers can intercept the information, they can not decode the primary statistics. Therefore, the AIS has an extensive application prospect.