Research On Message Correlation Technology Of MLAT Central Station

With the rapid development of airport construction and civil aviation industry,multilateration(MLAT),which is a new surveillance technology,has received more and more attention.An important factor affecting the accuracy of MLAT is the central processing station message correlation.The central station correlates the same message of the same aircraft in a large number of mixed messages sent by each receiving station,and then uses the timestamp information to obtain the value of time difference of arrival(TDOA)to achieve the position of the target.The central station message correlation technology is divided into two steps,the classification of the messages and the processing of non-line of sight(NLOS)messages.Firstly,lots of relevant literatures are reviewed,then domestic and international research status of the MLAT system and the research status of NLOS error processing are summarized.Then,the principle of MLAT system and the structure of MLAT system are summarized.The MLAT system mainly uses the TDOA positioning method.The basic positioning algorithm includes Taylor series expansion method and CHAN algorithm.At present,the hybrid positioning algorithm combining the above two algorithms is an efficient positioning solution method.Next,the central processing station messages classification of the MLAT system is discussed.The ground receiving station of the MLAT system sends all the messages received in this time period to the central processing station every fixed period of time.Each message contains the base station number,the aircraft address code,the message source code and the time stamp information.After receiving all the messages of each ground receiving station,the central processing station needs to use the information in the message to correlate the different arrival times(TOA)of the same aircraft with the same message,thereby realizing the correlation of the messages,and then calculating the time difference is reached and the aircraft is located using the TDOA positioning algorithm.The first step in efficient correlation of messages is to classify the messages in order to extract the same message from the same aircraft.The purpose of message classification is achieved by defining the maximum messages interval and the interval of reflected messages.It is the foundation work for the efficient correlation of messages.Then,the identification method of NLOS messages is studied.After the message classification is completed,there may still be NLOS messages in the remaining messages,so the NLOS messages need to be identified.Firstly,two kinds of residual methods for NLOS message identification are studied,and the first improvement method combining two residual methods is proposed.Then the disadvantages of the first improved method are analyzed.A NLOS identification method based on geometric dilution of precision(GDOP)selection is proposed.Finally,the simulation results show that the improved method can increase the identification rate without increasing the computational complexity.Finally,the work of this paper is summarized,the defects of this research are pointed out,and the future research is prospected.