Interferences in Safety Critical Land Transport Application: Notch Filtering vs Wavelet Transform, an Experimental Analysis

In safety-critical applications, the vulnerability of the Global Navigation Satellite System (GNSS) to radio frequency interferences (RFIs) is a major concern. The development of a fail-safe and robust localization system now necessarily requires detection and mitigation of such interferences, which has increased with the proliferation of wireless systems and easy access to personal privacy devices (PPD) also known as jammers. Moreover, the advent of software-defined radio (SDR) permitting the transmission of customized and more complex signals has further complicated this problem. This paper provides an in-depth comparison of interference mitigation techniques at multiple levels primarily focusing on the safety perspective at the position level. For this purpose, the classical adaptive notch filter (ANF) and the wavelet packet decomposition method are applied to mitigate the effects of interference. This comparative study aims to assess the performance of these mitigation techniques at multiple levels (frequency estimation, acquisition, tracking and position). However, the main goal for the final user is to study the impact on key performance indicators (KPIs) such as accuracy, availability, and safety. Furthermore, two cases are considered: 1): interference in the absence of any mitigation strategy and after applying interference mitigation technique at the pre-correlation level. The complete study is presented for two different types of time-varying continuous wave (CW) interference signals namely frequency hopping and the chirp signal.