# Characterization of Carrier Phase-Based Positioning in Real-World Jamming Conditions
## 1 Introduction  
Today, global navigation satellite systems (GNSSs) are widely used for their capabilities within positioning, navigation, and timing (PNT) for civilian and commercial as well as military purposes. This includes many critical purposes such as search and rescue (SAR), aviation, and autonomous vehicles. Especially with more and more autonomous systems relying on GNSS-based PNT, the consequences of an outage or denial of GNSS data will also become more severe. Furthermore, it was estimated by London Economics (in 2017 and 2019, respectively) that a five-day outage in GNSS would amount to losses of \(\ell\)5.2 bn (\(\sim\)57.2 bn) in the United Kingdom [1] and 4.9 bn DKR (\(\sim\)50.8 bn) in Denmark [2]. Therefore, GNSS availability should in general be a major concern, especially because GNSS signals arriving at the surface of the earth are weak, and thus easily susceptible to interference and jamming. During the last decade, small jammers, often referred to as personal privacy devices (PPDs), have received increased focus. They appear to be widely used [3], and while meant to only block reception of the users' own personal GNSS equipment, their range is often far longer than the users realize. PPDs of various kinds have been extensively analyzed in both [4, 5]. These extensive surveys have looked at signal characteristics in both the time and frequency domain, as well as transmit power and an estimation of the range of denial of GNSS service. Several incidents have already shown how vulnerable GNSSs may be in the presence of such PPDs. Incidents at Newark airport following the implementation of a local area augmentation system (LAAS) in 2009 are well described in [6], but similar incidents are alsoseen elsewhere, for instance, in Norway, where the ambulance helicopter, \"luftambulansen\", has seen several GNSS outages due to PPDs [7]. Many other studies [8; 9; 10; 11] suggest that these incidents are not unique or coincidental. All of these studies confirm that, in areas with human activity and especially near major roads, a lot of interference may be detected. Similar events have also been seen in harbors. An international measurement campaign studied radio frequency interference (RFI) in both the L1/E1 and the L5/E5a bands from aboard a container ship travelling between Europe and Asia [12; 13]. They recorded several incidents of jamming and interference in both ports and heavily trafficked sea routes all around the world. The impact of jamming on GNSS receivers has previously been investigated by several authors. Most use actual PPD jammers or a similar synthesized signal. In [14], a lab setup was used in order to investigate the impact of both single- and dual-frequency PPDs on the code-based positioning accuracy of a consumer-grade GNSS receiver. In [15], a similar setup was used in order to evaluate the performance of a multi-constellation, multi-frequency receiver in the presence of a GPS L1 jammer. Both papers reported large positioning errors during heavy jamming and a decreased position availability. Lab tests were also done by [16], where real-world jamming data registered on monitoring stations as part of the STRIKE3 project (www.gnss-strike3.eu) were used in evaluating code-based receiver performance in a standardized test. This showed some difference between mass-market and professional grade receivers, especially in the prioritization of accuracy versus availability. Several real-world tests have also been conducted to demonstrate the possible impact of GNSS jamming. Investigations into the marine environment have been conducted by [17], in which a setup with a GPS jammer at a lighthouse made passing vessels report their position as much as 22 km off the true position. The authors of [18] further examined marine navigation.