Multi-Frequency (L1/L2/L5) Algorithms for Satellite Failure Isolation

Yi-Hsueh Tsai, Fan-Ren Chang, Wen-Chieh Yang and He-Sheng Wang

Abstract:	In this paper, a multi-frequency algorithm based on the parity vector method is proposed to exclude the failed satellite in Receiver Autonomous Integrity Monitoring (RAIM). In satellite failure isolation, the resulting parity vector of the multi-frequency algorithm is compared with the channel vectors to identify the failed satellite. The conventional isolation algorithm processes only single frequency L1. However, after the L2 and L5 frequencies are available in the near future, the additional information will help reduce the incorrect exclusion rate of satellite failure. Because the error due to the ionospheric delay is highly related to frequency, so it can be removed by using dual frequency or multi-frequency signals. Furthermore, more available measurements will increase the dimension of the parity space under a fixed number of visible satellites. The minimum angle between two channel vectors will thus be increased. This paper provides a systematic algorithm to obtain the optimal channel vectors of multi-frequency. In the simulation, a 24-satellite constellation with perfectly circular orbits is assumed. A total of 1152 space-time sample points can be produced according to the RTCA DO-208. For each point, the exclusion of satellite failure can be examined. Two types of satellite malfunction are applied. One is all frequencies of one satellite are failed with same bias, which means the satellite atomic clock system is failed. The other one is one frequency (L1, L2 or L5) of one satellite are failed, which means the circuit of one frequency in satellite is failed. Simulation results show that, after the detection of satellite failure, the successful rate of isolation of using the multi-frequency algorithm is better than that of using the conventional algorithms.
Published in:	Proceedings of the 58th Annual Meeting of The Institute of Navigation and CIGTF 21st Guidance Test Symposium (2002) June 24 - 26, 2002 Hyatt Regency Hotel Albuquerque, NM
Pages:	250 - 260
Cite this article:	Tsai, Yi-Hsueh, Chang, Fan-Ren, Yang, Wen-Chieh, Wang, He-Sheng, "Multi-Frequency (L1/L2/L5) Algorithms for Satellite Failure Isolation," Proceedings of the 58th Annual Meeting of The Institute of Navigation and CIGTF 21st Guidance Test Symposium (2002), Albuquerque, NM, June 2002, pp. 250-260.
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