Analysis Of Parameters Influencing Weak Gnss Signal Processing

Indoor navigation and positioning methods are continuously evolving as a result of the diversity of applications. In some wireless high channel traffic areas, indoor navigation is facilitated by various wireless technologies such as Wi-Fi hotspots, Bluetooth beacons and other special signal transmitters. In addition to the use of these technologies, significant performance improvements can be achieved by integrating these systems with data obtained with GNSS receivers. Furthermore, standalone GNSS based indoor positioning is essential for low channel traffic areas like isolated residential complexes and houses where deploying dedicated infrastructure might not be viable. Therefore, regardless of the recent evolution of non-GNSS approaches, there is a need to exploit weak GNSS signals and characterize their behavior in indoor environments. The research presented in this paper focuses on assessing different factors that contribute towards GNSS weak signal detection. There are three main factors that have a major impact on weak signal processing using long term integration, namely short term stability of the receiver clock, accuracy of the estimated trajectory used during integration, and changes in the channel model during integration. Individual contributions due to each one of these are analyzed. Indoor GPS data was collected in different indoor environments, namely commercial concrete building and townhouse with brick walls for the characterization process. Effect of the indoor channel behavior is characterized for a static user and for a moving antenna placed on a linear motion table. Additionally, spatial domain characteristics for two closely placed antennas are analyzed. Finally, data samples are collected for a short period every 30 minutes over a seven-hour window and position estimates are compared to study time domain dependencies. Analyses are supported with measurement and position domain results.