Research On Receiver Autonomous Integrity Monitoirng And The Simulation System

Global Positioning System (GPS) has been widely used in various fields. With the aidingof GPS, people have more stringent requirement of the system security in the field ofsafety-critical applications. The navigation system is not only capable of providingpositioning、navigation、timeing services, but also could alarm the user in time in the case ofsystem faulty and unable to provide users with the right navigation information. This ability iscalled the integrity, which in essence is the confidence of the information of system. Receiverautonomous integrity monitoring has been used as one of the integrity monitoring methods,which detect the satellite fault quickly and embed with the receiver, while independent ofexternal augment system. RAIM have wide range of applications because of the excellentperformances such as low-costing and flexibility.The traditional RAIM algorithm requires at least five satellites in view in terms ofsatellite fault detection, while at least six satellites in view in terms of satellite faultidentification. It’s too strict to implement the integrity monitoring under the extremecondition of unsatisfying satellite redundancy. Meanwhile, the statistics in the traditionalRAIM algorithm are independent of history code measurements, which pay less attention totime-domain information during the fault detection. So the fault detection efficiency isunsatisfying in the case of for the small fault and slow growth fault, which is unable to meetthe required navigation performance for high precision navigation. So the enhancement oftraditional integrity monitoring algorithm is necessary.The traditional RAIM algorithm is firstly analyzed in detail, and then a new receiverautonomous integrity monitoring approach was proposed for detecting and identifyingsatellites fault. The proposed approach improves the performance of fault detection by usingtime-domain information, i.e., the Kalman innovation covariance. Furthermore, the proposedapproach can efficiently unleash the requirement for the number of visible satellites.Computer simulation results indicate that in the extreme condition of not enough satelliteredundancy, whichlead the traditional algorithm not to work normally, the proposed algorithmcan also detect the fault satellite effectively. The fault detection rates arrive ninety persentunder the condition of insert seventy-eight meters fault error. Compareed with the traditionalsnapshot RAIM, the new algorithm has a significant improvement in performance of integritymonitoring. As the satellite fault cases in the real world are rare, it is difficult to verify the algorithmof integrity monitoring. So the Windows operating system is utilized as a platform with theaim of developing a simulation software about RAIM based on VC++6.0. The user canproduce ephemeris and observation accordingly. Meanwhile, the user also can insert anysimulated fault information into the measurements at any epoch. It is can be concluded that itis truly convenient for the following research about receiver autonomous integritymonitoring.