Derivation of Integrity Allocation for Satellite Based Augmentation System Ionosphere Monitors

Integrity design, including fault node design, node probability allocation and fault elimination method design, has been the focus of Satellite Based Augmentation System. At present, most of the researches on integrity allocation are aimed at the range error caused by satellite signal fault. In contrast, fault from delay measurement of the Ionosphere Pierce Point does not directly affect the range, but indirectly affects the delay of IGPs. This may lead to some difference in MERR calculations. In addition, the test statistics of ionosphere anomalies are usually in chi-square form, so the traditional linear hypothesis is no longer valid. In this paper, the above problems are analyzed and the ionosphere related integrity allocation is studied. Taking the Feared Event with a “shift” of the distribution as an example, we first analyze the relationship between protection level integrity risk and the “shift” amount with the concept of Maximum-allowable ERror in Range (MERR). Then according to the Minimum Detectable Error (MDE), the monitor threshold and the expression of missed detection risk are obtained for the chi-square detection. Finally, the relationship between integrity risk and variance is analyzed, and the general methods to be followed in integrity design are given. The conclusions given in this paper can guide the BD SBAS integrity design.