# Study and Analysis of Interference Signals of the LTE System of the GNSS Receiver
## 1 Introduction  
GNSS system interference can be divided into two types: intentional and unintentional interference. Multipath interference refers to interference signals created by the reflected GNSS system signals from objects around the receiver antenna. It is one of the common sources of errors in this system. Multipath noise can alter the phase characteristics of the receiver tracking loop, leading to tracking and measurement errors. Research has shown that the resulting pseudo-range errors can range from a few to several hundred meters [1, 2, 3, 4, 5, 6, 7, 8], which are sufficient to deteriorate the operational reliability of the system and positioning accuracy. However, since the effect of multipath interference shows significant differences for different observation times and station surroundings, there is currently no general and accurate mathematical model for correcting multipath errors. Therefore, suppression of multipath interference is always a hot topic of research in the field of GNSS receiver design [9, 10, 11]. Current multipath interference suppression technologies are developing primarily through the use of two approaches: receiver antenna design and signal processing. Antenna improvement technologies, from the antenna design point of view, include activities such as drawing a diagram of the multipath environment around the antenna, using special types of antennas, and selecting the appropriate locations to position the antenna [12, 13, 14, 15]. Multipath interference suppression technologies based on signal processing fall into two main categories: time domain signal processing and spatial domain signal processing. Commonly used processing methods in the time domain include enhanced correlator techniques represented by the narrow correlator technique [16; 17] and parameter estimation methods represented by the MEDLL technique (Multipath Estimate Delay Lock Loop) [18; 19]. The process of spatial signal processing is mainly based on the fact that the LOS (line of sight) signal and multipath noise reach the receiver from different spatial directions; therefore, multipath interference suppression can be achieved using adaptive signal processing with multiple antennas [20; 21; 22; 23; 24; 25; 26; 27; 28]. Focusing on the problem of multipath interference suppression for the GNSS system, this article presents a model of the signal received in the event of interference from the LTE (Long-Term Evolution) system, and the impact of interference on GNSS receivers was analyzed [29]. An effective way of detecting irregularities in the received GPS signal can be the comparison of the determined position of the receiver with the position determined based on data from another location system, e.g., ground-based eLoran [30] or inertial systems [31; 32]. The disadvantage of this solution is the higher cost (two receivers or an integrated receiver). Furthermore, the use of other navigation systems comes with limitations. The signals of terrestrial radionavigation systems may only be received within a certain area. On the other hand, in inertial systems, the problem is the accumulation of position estimation error [33]. The analysis of the available literature shows that currently conducted studies of this type are generally carried out under fairly favorable and established conditions, which are often manifested by the unlimited visibility of the celestial sphere. The main analysis parameter is the BER (Bit Error Rate) parameter evaluating the ratio of the correct signal to the interference signal [34; 35]. Signals with a spread spectrum have greater resistance to fading and interference than narrowband signals with the same utility data rate. While the spectrum of the usable signal is focused in the GNSS receiver, i.e., when the signal is converted from broadband to narrowband form, the spectra of narrowband interference and selective fading are dispersed so that the signal degradation caused by them is significantly reduced.