GNSS Interference Simulator Design for RFI Impact Assessment and Detection Algorithm Development

Abstract

Global Navigation Satellite System (GNSS) is an essential system for land, maritime, and air navigation. GNSS is also used as main source for time synchronization in financial transaction and electrical grid. In addition, location based service based on GNSS is commonly used for general population. GNSS-based applications are proliferating due to its accuracy, convenience and low cost. However, most people do not realize how vulnerable GNSS is and its vulnerability problem has not resolved even though dependency on GNSS is rapidly increasing. The motivation of this thesis is to find a possible solution for GNSS vulnerability, especially for aviation applications. A Ground Based Augmentation System (GBAS) is an enabling technology for aircrafts GNSS based precision approach by enhancing GNSS navigation performance. The GBAS is well designed to ensure navigation systems accuracy, integrity, availability, and continuity in normal radio frequency environment. However, its use is limited when radio frequency interference (RFI) is present. Some of potential RFI sources can be mitigated or eliminated by controlling unintentional RFI sources around airport and by enforcing law to prevent sales and use of commercial privacy jammers. However, RFI detection, mitigation and characterization system is still required for contingency. In this thesis, research is carried out to examine interference detection parameters and to propose applicable detection algorithm for aviation application. After analyzing pre-correlation and post-correlation detection parameters characteristics, an interference detection algorithm is developed utilizing AGC gain and adaptive lattice IIR notch filter parameters considering these parameters strengths and weaknesses. The proposed interference detection and characterization algorithm is designed to be used even in excessive RFI environment which prevent GNSS signal acquisition and tracking. The proposed algorithm can detect and classify various interference signals and estimate their signal power. The performance of the algorithm was verified by Monte-Carlo simulation. In addition, MATLAB SIMULINK GNSS interference simulator was designed to assess interference impact on GNSS receiver performance and to characterize interference detection parameters. The designed GNSS interference simulator is a flexible simulation platform to generate GNSS signal data in various types of interference environment according to users needs. Therefore, the GNSS interference simulator acted as an essential tool for interference detection and characterization algorithm development. The proposed detection and characterization algorithm and the GNSS interference simulator will be used for interference mitigation and location algorithm research.