# Study and Analysis of Interference Signals of the LTE System of the GNSS Receiver
## 4 Simulation Studies
### Noise in the GNSS Receiver--Identification
The research described in [34; 35] indicate that a transmitter transmitting an interfering signal with a power of 244 mW, in a bandwidth of 2 MHz, is sufficient to prevent the reception of GPS signals within a radius of more than 6 km when the receiver is tuned to signals from satellites and within a radius of more than 8 km when the receiver is not yet synchronized with them. The effectiveness of the interfering signal of GNSS signals does not only depend on the power of the received interfering signal but also on its frequency characteristics. The spectrum of [PERSON]'s string pulses is stripe-like, where the striations are spaced from each other and from the carrier frequency by a multiple of 1 kHz, which is the reciprocal of the period of a 1 ms pseudorandom sequence. The publication [42] shows that high-interference efficiency is obtained by transmitting signals whose power spectral density is high at these frequencies (e.g., mono- and polyharmonic signals). The only difficulty in implementing the interference in this case is that the carrier frequency of the GNSS signal is shifted by the Doppler frequency, one component of which depends on the--generally unknown--velocity of the satellite relative to the receiver. The research described in [34; 35] has also shown that strong interference outside the GNSS systems band may also have a negative impact on the quality of reception of navigation signals. The algorithms that are used to calculate the ratio of the carrier wave power to the spectral power density of the noise make it possible to make a measurable assessment of the quality of the received signals. Correct estimation of signal quality is essential to obtain system or interference signal performance characteristics. It should be noted that calculations of the \(C/N_{0}\) ratio using different methods give similar but non-identical results. In this article, it is assumed that the estimated \(C/N_{0}\) values should deviate as little as possible from the real ones in the range of 35 to 60 dBHz, because such values are observed in real conditions. Simulations were performed to calculate \(C/N_{0}\) using the variance summation method, the Beaulieu method, and the moment method. The obtained results are presented in the figure above (Figure 7). As can be seen, for values not lower than 40 dBHz, the absolute error for all three methods does not exceed 0.5 dB. The variance summation method slightly underestimates the result, and the method of moments similarly overestimates it. The smallest error is obtained in the Beaulieu method; however, for values less than 40 dBHz, it exceeds \(-2\) dB. Taking into account the entire considered range from 35 to 60 dBHz, the smallest mean error is obtained when using the variance summation method. Therefore, this method was chosen for the estimation \(C/N_{0}\) in this paper. From the results obtained, it can be estimated that the improvement is about 2 dBHz, which translates into an improvement in the obtained positioning accuracy of the GNSS receiver. The figure below (Figure 8) shows a part of the correlation results when searching for the location of the satellite preamble 15 in one channel. It is seen from the figures that there are some high peaks that can go up to 160 or a little less. For a 37 s long signal, six preamble patterns should be found, and each of them has 6 s distances from adjacent patterns. Figure 7: The course of the \(C/N_{0}\) ratio for the GNSS system with the presence of LTE system interference signals. Figure 10: Signal processing in the GPS receiver working on the L1 frequency; on the left side, the signal waveform in color without the noise suppression system applied; on the right side, the working system operating in the LTE system signal elimination for the reception of signals from four satellites. The presented results confirm the effectiveness of the developed method of noise elimination in the form of interference signals.