## 2 Related Works
### Signal Processing Approach to Mitigate ADI  
[PERSON] et al. [10] have developed an atmospheric duct interference mitigation system for the 5G New Radio mobile networks. The 5G New Radio mobile network uses an orthogonal frequency division multiplication scheme to multiplex the information-bearing signals in the carrier signals. The mitigation scheme uses remote interference management-based reference signal design to recognize and mitigate the atmospheric duct interference in 5G New Radio mobile networks. The reference signals are placed in two carrier types: Additive White Gaussian Noise (AWGN) and tapped-delay line (TDL-E). The false alarm rate and detection probabilities are plotted with different Signal-to-Noise ratios in the experiments.  
Also, [PERSON] et al. [8] published another article, which also used remote interference reference signal sequences to detect atmospheric duct interference in the 5G New Radio networks. They designed the 5G New Radio system in AWGN and TDL-E channels. The comb 1 and 2 systems achieved an 18 dB Signal-to-Noise Ratio (SNR), and the comb 4 system achieved a 13 dB SNR.  
[PERSON] et al. [11] developed an ADI mitigation system that can adjust the guard period based on the remote interference reference signal in 5G New Radio. They have obtained a 5-7 dB SNR reduction in 5G New Radio networks.  
[PERSON] et al. [12] used the ADI mitigation systems in TD-LTE networks. The mitigation approaches were developed based on the decisions of the TD-LTE reference signals. They used three different ADI mitigation approaches. The first approach was developed by controlling the signal power of the antenna. The second approach was developed by controlling the elevation angle of the antenna. The third approach controlled the antenna height.  
The referenced studies highlight that atmospheric ducting significantly exacerbates interference, particularly in lower frequency bands (sub-6 GHz) due to their superior long-distance propagation characteristics. Consequently, the majority of the literature on 5G New Radio (NR) focuses on Frequency Range 1 (FR1, 410 MHz-7.125 GHz) compared to Frequency Range 2 (FR2, 24.25-71 GHz), as FR1 bands are more susceptible to such interference phenomena.  
A summary of the digital signal processing-based mitigation schemes is given in Table 1.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Approach** & **Year** & **Detection Methodology** & **Accuracy** & **Network** \\ \hline \multirow{2}{*}{[PERSON] et al. [10]} & \multirow{2}{*}{2019} & \multirow{2}{*}{Fast Fourier transform} & Detection probability: 0.900 & \multirow{2}{*}{5G New Radio (FR1)} \\  & & & False alarm probability: 0.002 & \\ \hline \multirow{2}{*}{[PERSON] et al. [8]} & \multirow{2}{*}{2021} & Remote interference & \multirow{2}{*}{18 dB SNR for comb 1 and 2, 13 dB SNR for comb 4.} & \multirow{2}{*}{5G New Radio (FR1 and FR2)} \\  & & reference signal design & & \\ \hline \multirow{2}{*}{[PERSON] et al. [11]} & \multirow{2}{*}{2024} & Guard period & \multirow{2}{*}{5–7 dB SNR reduction} & \multirow{2}{*}{5G New Radio (FR1 and FR2)} \\  & & adjustment based on & & \\ \multicolumn{4}{c}{remote interference} & & \\ \hline \multirow{3}{*}{[PERSON] et al. [12]} & \multirow{3}{*}{2017} & ADI mitigation systems & Power: 1–2 dB SNR reduction, & \multirow{3}{*}{TD-LTE Networks} \\  & & based on the TD-LTE & Elevation angle: 5–10 dB SNR reduction, & \\ \multicolumn{4}{c}{reference signals} & & Antenna height: 3–4 dB SNR reduction & \\ \hline \hline \end{tabular}
\end{table}
Table 1: Digital signal processing-based mitigation approaches.