Narrowband jamming mitigation in vector-based GPS software defined receiver

Abstract

The last decade has witnessed a growing demand for reliable, continuous and accurate positioning and navigation with the growth of a wide range of new applications that rely predominately on Global Navigation Satellite System (GNSS), including Global Positioning System (GPS). The widespread of these applications and their integration in many aspects in our day-to-day activities made GNSS receivers appealing targets for disruption or jamming. Although, GPS signals employ direct sequence spread spectrum (DSSS) modulation that provides some level of robustness to intentional and unintentional radio frequency (RF) interference; GPS signals are vulnerable to interference and jamming as they reach the receiver antenna below the noise floor. A jamming signal can degrade the signal-to-noise ratio (SNR) which results in deterioration in the acquisition, tracking and navigation stages within the receiver. The resultant degradation or interruption of the GPS service due to signal jamming could lead to significant consequences and risks. Loss of time synchronization, disruption of communication and network operations, and potential loss of life are examples of these consequences, to name a few. The primary objective of this thesis is to provide a GPS-based reliable and uninterrupted positioning solution in the presence of interference signals, particularly continuous wave (CW) and swept continuous wave (SCW) signals. To tackle this challenge, first, a robust vector-based software defined receiver has been implemented, and its performance was assessed in degraded signal conditions including the presence of interference. Second, two pre-correlation jamming mitigation techniques are proposed. The first technique is based on transforming the incoming signal into time-scale domain using wavelet packet transform (WPT), in which the jamming signal can be better identified and isolated. The second is a high-resolution spectral analysis technique that is based on fast orthogonal search (FOS), in which the jamming signal is modeled using a set of candidate functions and then suppressed from the received signal. These two techniques were augmented with the vector-based software receiver and their performance was assessed using various static and dynamic scenarios.