Adaptive Multi-hypothesis Vector Tracking System � Design and Implementation

Abstract

The demand for navigation devices is always high in environments where GPS signals can experience extreme conditions leading to lower carrier-to-noise ratio (C/No) levels or complete signal outages. Thus, more efficient and reliable signal tracking algorithms are always needed to attain signal availability. One important factor that can significantly affect efficiency of receivers in terms of complexity and speed is the receiver’s signal tracking system design. Conventionally receivers used scalar tracking loops in which signals from different satellites were assigned separate channels and hence tracked independently. This did not allow the receiver to benefit from information about its state and dynamics to facilitate and enhance the tracking process. Modern GPS receivers, however, process all the signals together within one loop for both tracking and navigation, which allows information exchange between the different channels. This latter type of tracking systems is known as vectortracking architecture. The objective of this paper is to introduce a novel adaptive multi-hypothesis vector-based receiver tracking system that enhances receiver’s tracking robustness and sensitivity in challenging scenarios and, consequently, improve navigation availability. Such filters generally pose the problem of increased computation loads; however, with the dramatic increase in the modern chip’s computation power, it is worth trying to apply this filtering technique in vector-based tracking loops to replace the currently used algorithms. This is possible particularly in applications where minimizing power consumption is not an issue. Accordingly, one method that has been selected in this work is the minimum variance resampling—a technique that minimizes the computations required for such filters. The software receivers approach has been adopted in this work as a platform for implementing the proposed design. However, the proposed methodology can be equally applied in conventional hardware receivers, as well. The effectiveness of the developed method is tested and verified against conventional scalar signal tracking systems. System performance has been tested using variety of simulation trajectory data analysis in various conditions and scenarios.