# Resilience of LTE-A/5G-NR Links Against Transient Electromagnetic Interference
## 3 Materials and Methods  
This experiment evaluated the impact of transient EMI on a controlled communication link established using commercial off-the-shelf (COTS) software-defined radios from National Instruments. This study utilized the National Instruments USRP-2943R (Europe), which is functionally equivalent to the Ettus Research X310 USRP, along with a Ettus Research CBX-40 RF daughterboard (Europe) card providing full-duplex operation with a 40 MHz bandwidth.  
The experimental setup comprised three NI USRPs equipped with Ettus Research CBX-40 RF daughterboard (Europe) RF cards. Two USRPs were used to establish the  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Citation** & **Key Idea** & **Impact** \\ \hline
[3] & Jamming attacks in electrified railway environments. & Narrowband jammers have lethal and prolonged effects on communication links compared to UWB jammers. \\ \hline
[4] & Leveraging Bidirectional Long Short-Term Memory (BiLSTM) networks for sequential pattern learning and interference mitigation. & The BiLSTM-based model efficiently processes time-series signals, enabling real-time detection and classification with a 93.4\% accuracy, surpassing previous approaches. \\ \hline
[5,6] & Analysed OFDM signal vulnerability and the impact of interference parameters on communication degradation, considering reception-stage signal processing. & The study showed that interference depends on the sweep period and receiver’s time window. A longer observation window reduces the impact, affecting fewer subcarriers. Adjusting the window minimises interference. \\ \hline
[7,8] & Transient EMI generated by catenary and pantograph contact impacts the LTE link. & The peak-to-average power ratio (PAPR) evaluation metric is proposed instead of the EVM because the EVM breaks down when the value exceeds 17.5\%. \\ \hline
[9] & Susceptibility study of an IEEE 802.11n network in a railway electromagnetic (EM) environment. & There is a direct relationship between the interference power, its duration, and the highest average power measured by the Clear Channel Assessment (CCA), which affects the BER. \\ \hline
[10] & Analysed antenna performance for four railway communication systems (TETRA at 380 MHz, GSM-R at 900 MHz, LTE-R at 2.6 GHz, and BBRS at 5.9 GHz) under the influence of the pantograph and catenary. \\ \hline
[11,12] & Developed a test system for EMI caused by high-voltage discharge in a pantograph–catenary system. & Electromagnetic disturbances from loose catenary– pantograph contact increase with higher voltage, intensifying impulse radiation. \\ \hline This article & Developed a system to test interference in LTE-A/5G-NR systems using USRPs. & 5G-NR is susceptible to interference from transient EMI. \\ \hline \hline \end{tabular}
\end{table}
Table 1: Summary of literature review.  
primary communication link by transmitting and receiving standardized LTE and 5G-NR waveforms, ensuring repeatable BER and EVM performance. The LTE Toolbox and 5G Toolbox were employed for waveform generation and processing, while MATLAB version R2024b Wireless Testbench facilitated high-speed transmission and reception of complex waveforms without dropped samples.  
A third National Instruments USRP (Europe), with identical RF and digital specifications, was used to generate RF interference signals at various centre frequencies. A Rohde & Schwarz spectrum analyser monitored the power spectral density (PSD) of the received signal in the presence of interference. Frequency scanning between 2.194 and 2.2045 GHz identified the most EMI-sensitive centre frequencies, with interference gains set at 12 dB, 15 dB, and 18 dB.  
The findings from the experiment highlighted a significant impact at an 18 dB gain, which effectively disrupted communication, underscoring the potential severity of transient EMI at higher interference gains. This effect of the 18 dB gain on signal degradation is discussed in detail in this paper, revealing critical insights into EMI resilience and vulnerability in different frequencies and gain settings.