Integrity analysis of vector tracking architecture

This paper examines the issue of Receiver Autonomous Integrity Monitoring (RAIM) for GPS receivers using vector tracking loops. The RAIM algorithms for scalar architectures are not directly applicable to the vector architecture as the pseudorange measurements output from a vector tracking receiver are all affected by a failure in one channel. Thus, the basic single fault assumption of the traditional RAIM falls apart when implemented with the pseudorange measurements of the vector architecture. In this paper we develop an alternative way to apply the scalar loop RAIM to the vector architecture. This is accomplished by deriving the input to the RAIM algorithm from the correlator outputs. It is also shown that with proper design the vector loop RAIM offers performance comparable to the scalar loop RAIM in terms of the following metrics: Fault detection times since the onset of the fault and protection levels. Thus, it is demonstrated that it is possible to detect system faults using vector receiver architecture even though its pseudorange measurements do not comply with the single fault assumption of the traditional RAIM. The performance of the vector loop RAIM is confirmed using a series of simulation studies.