Research On Key Technology Of Non-contact Detection Of AIS Equipment

The Automatic Identification System(AIS)is a new navigation aid system that integrates the automatic identification,communication and navigation functions of the ship.It is promoted by the International Maritime Organization,the International Telecommunication Union and the International Atomic Energy Association in 2000.The AIS system guarantees the safety of shipping and the communication between ship and ship,ship and shore.The IMO mandates that all international voyages and Non-international vessels must install AIS equipment by July 1,2008.At present in the AIS system,the AIS equipment accounts for more than 95%,so the performance of the AIS equipment is critical to the safety of shipping and the proper operation of the AIS system.At present,there are some technical indicators in the international standards for ship-loaded AIS berths,which restrict the generality of the berth,but lack effective testing methods.And the state department has not set up perfect equipment monitoring system,regulation of AIS berth cannot penetrate.According the current status of AIS detection,the thesis conducts the following research:(1)The thesis studies the AIS detection index.The basic functional requirements for normal operation of AIS equipment include: AIS equipment receiving messages correctly according to regulations,and the contents of messages are not missing.The basic communication performance index of AIS is determined based on AIS protocol and communication protocol layer.Basic communication performance indicators of AIS include autonomous mode emission,static data normalization,static message reporting rate,location message reporting rate,and location update rate.The basic physical requirement for normal communication of AIS equipment is that the performance of electromagnetic wave transmission.One example is carrier frequency deviation.The communication performance indexes are: signal to noise ratio,carrier frequency deviation,the time and frequency characteristics of modulation signal.(2)For signal-to-noise ratio detection,the thesis proposed an algorithm。The algorithm can estimate the signal-to-noise ratio of AIS equipment under contactless conditions.Based on the AIS frame structure,the auxiliary symbol element is constructed,and then the signal power and noise power are estimated,and then calculate the signal-to-noise ratio.Simulation results show that the detection error of this method is small,and the anti-frequency deviation,antidelay and anti-initial phase performance is batter.This method has a great significance to reflect transmitter performance and channel quality.(3)A method for carrier frequency deviation index detection is presented.This method can detect carrier frequency deviation of AIS equipment under non-contact mode.This method includes constructing auxiliary symbols and auxiliary signals based on the AIS frame structure,determining the positive and negative signs of frequency deviation and calculating the frequency deviation.This method reduces the computational complexity and improves the estimation accuracy.The estimation range is large and the anti-delay and initial phase performance is batter.This method has a great significance to reflect the performance of transmitter physical layer.(4)The thesis proposed some methods to the indexes of AIS on basic operational performance and indexes on communication performance.Finally,the thesis proposes a system design on non-contact detection of AIS equipment,focusing on the design of the processor,and the static timing sequence simulation is carried out.