Carrier‐phase ranging measurements from Global Positioning System (GPS) and low‐Earth‐orbiting Iridium telecommunication satellites are integrated in a precision navigation system named iGPS. The basic goal of the system is to enhance GPS positioning and timing performance, especially under jamming. In addition, large satellite geometry variations generated by fast‐moving Iridium spacecraft enable rapid estimation of floating cycle ambiguities. Augmentation of GPS with Iridium satellites also guarantees signal redundancy, which enables Receiver Autonomous Integrity Monitoring (RAIM). In this work, parametric models are developed for iGPS measurement error sources and for wide‐area corrections from an assumed network of ground reference stations. A fixed‐interval positioning and cycle ambiguity estimation algorithm is derived and a residual‐based carrier‐phase RAIM detection method is investigated for integrity against single‐satellite step and ramp‐type faults of all magnitudes and start‐times. Predicted overall performance is quantified for various ground, space, and user segment configurations.

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The concept of Relative Receiver Autonomous Integrity Monitoring (RRAIM) using time differential carrier phase measurements is investigated in this paper. The precision of carrier phase measurements allows for mitigation of integrity hazards by implementing RRAIM monitors with tight thresholds without significantly affecting continuity. In order to avoid the need for cycle ambiguity resolution, time differences in carrier phase measurements are used as the basis for detection. In this work, we examine RRAIM within the context of the GNSS Evolutionary Architecture Study (GEAS), which explores potential architectures for aircraft navigation utilizing the satellite signals available in the mid-term future with GPS III. The objectives of the GEAS are focused on system implementations providing worldwide coverage to satisfy LPV-200 operations, and potentially beyond. In this work, we study two different GEAS implementations of RRAIM. General formulas are derived for positioning, fault detection, and protection level generation to meet a given set of integrity and continuity requirements.2. GEAS. 3. GPS III. I N T R O D U C T I O N. Carrier phase differential RAIM implementations have been investigated in prior work to help detect specific navigation threats, including ephemeris broadcast anomalies [1] and ionospheric storm fronts [2]. The great precision of carrier phase measurements allowed for tight detection thresholds without significantly affecting continuity. It also provided the sensitivity to detect a much larger range of failure magnitudes than was possible using traditional code-based RAIM. The need for cycle ambiguity estimation was eliminated by differencing measurements in time, creating spatial baselines associated with the user's translation over the time-difference interval. We refer globally to these time-differenced carrier phase RAIM implementations as Relative RAIM (RRAIM) functions. The results in [1,2] showed that many troublesome ionospheric and ephemeris threats could be detected with carrier phase RRAIM implementations, even for applications where positioning was based on code phase [2]. The current process of modernization of Global Navigation Satellite Systems (GNSS) will improve navigation user capabilities in many ways. There will be

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