The Application Of Wireless Network Technology In Ships Navigation System

As the requirements of the qualities of ships navigation system in China has increasedgradually, the traditional ships Ethernet communication technology cannot satisfy thediversity and reliability of the navigation device data transmission. When ships navigationsystem data transmission lines are broken or large management of lines are not needed,normal connection of the ships network and the reliable transmission of the data are expectedto be realized by other means. By the submerge of IEEE802.11, wireless local area network(WLAN) has developed adversely in the past ten years. Based on the wide applications ofwireless terminal device in IEEE802.11g criterion in various fields, some military institutionsand commercial consumers are worried about the products for the openness of wirelesschannel. This thesis takes ships navigation system as background, based on WLANtechnology, deeply studies the feasibility, reliability, security of applications of WLANtechnology in ships navigation system.Firstly, this thesis systematically introduces the relative techniques of WLAN, mainlyincluding the composition, standards, physical layer principle and the interference types of theWLAN, and the classification of wireless network card. Then the working mechanism and thepotential security risks of the encryption standards of three wireless security－WEP, WPA,and IEEE802.11i is studied. It mainly elaborates the working mechanism of WEP, TKIP, andCCMP agreement and analyzes the RC4encryption algorithm, the potential security risks ofthe Initialization vector, and the safety of TKIP and CCMP. It takes the CCMP agreement ofthe high encryption standard–AES as the encryption method of ships navigation system datatransmission and takes various encryption mechanisms into network throughput test. Itsresults show that applying the CCMP agreement of the high encryption standard–AES notonly ensures the security of ships navigation system data transmission, but also meets therequirements of ships navigation system for real-time data transmission.Secondly, it studies the WLAN’s physical layer principle based on IEEE802.11g criterion,models the OFDM system based on802.11g and simulates it by MATLAB. Simulation resultsnot only analyze the bit error rate performance of the system under the different modulationmethods, but also prove that this system has strong anti-multipath interference capability.According to the research, when the data interference between WLAN and ships navigationsystem is not serious, in order to satisfy the needs of ships navigation system under differentcircumstances, two WLAN programs are designed. Finally, the thesis studies the network device drivers under VxWorks, carefully designsthe complete process of wireless network card driver module，including the initialization ofPCI wireless network card, the load of wireless network card driver and the receive andsending of data frame. Based on all of these, dual NIC redundancy switch of the navigationsystem is designed from three aspects–card configuration, detection, and switch, whichincrease the reliability. The tests results show the correctness of the ships navigation systemwireless data transmission in this thesis, and that it meets the requirements of the system forreliability and timliness.