## 4 Method for UAV Electromagnetic Interference Suppression
### Anti-Electromagnetic Interference Method of UAV Data Link
#### 4.1.2 Anti-Electromagnetic Interference Technology Based on Cooperative Communication  
In addition to improving the stability of the UAV network itself, there is also a class of anti-electromagnetic interference methods developed based on cooperative communication.  
One direction is single-machine multi-domain collaboration. Literature [52] proposes a cooperative communication method under the condition of multiple sources. The simulation results show that the scheme reduces the bit error rate of the received signal, and the transmission reliability is higher under the condition of the dynamic transmission rate. The research of multi-source cooperative communication has pointed out the direction for multi-link cooperative information transmission of the UAV data link. The literature [52; 53] proposed an asynchronous cooperative information transmission method on the basis of cooperative communication, from the physical layer (constructing the asynchronous cooperative transmission mode of three-dimensional space) and the link layer (through the multi-link cooperative forwarding protocol). Enhance the reliability of information  
\begin{table}
\begin{tabular}{p{142.3 pt} p{142.3 pt}} \hline \hline
**The Research Direction** & **Network Layer** \\ \hline Integration and performance evaluation of low-power MIMO systems [32; 33]. & Physical layer \\ \hline Research and application of anti-jamming technology represented by spread spectrum and frequency hopping technology [43; 44; 45; 46; 47]. & Link layer \\ \hline Under the limitation of limited spectrum resources, design high-throughput, high-reliability physical layer and MAC layer protocols and strategies [34; 35]. & Physical layer \\ \hline Integration of UAV data link system and satellite communication system, as well as other wireless communication systems [36; 37]. & Physical layer \\ \hline \hline \end{tabular}
\end{table}
Table 4: Some typical anti-electromagnetic interference research directions.  
transmission. The former makes full use of the three spatial diversity technologies at the physical layer to increase the diversity gain and greatly enhance the anti-interference ability. The latter at the link layer eliminates the impact of short-term changes in the link through single-transmit and multiple-receive and a bootstrap response algorithm based on a random synchronization contention window, resulting in better network arrival rate and energy efficiency, and enhanced transmission reliability. Improved anti-interference ability. Literature [54] proposes a cooperative communication relay selection method under the outdated channel state information generated by the relative movement of the receiver and transmitter or when the environment changes rapidly. Choosing the optimal relay can be resisted to a certain extent. Interference to cooperative communication systems. Literature [55] proposes a channel state information prediction technology based on MAP criteria to improve the anti-interference ability of cooperative communication systems.  
The other direction is multi-machine coordination. One of the advantages of Ad hoc networks commonly used in drone clusters is the system's robustness. The UAV cluster system will not be unable to operate normally due to communication interference of one or several UAVs. In addition, some researchers have further enhanced this property by improving the algorithm of Ad hoc networks. In reference to the problem of power optimization control in the multi-channel case, the literature [56] proposed a non-cooperative game distributed power control method based on the influence of the importance of multi-cluster network nodes of UAVs. Each node evaluates the importance factor of the entire network node based on the connectivity information. This algorithm can converge quickly and ensure the interference tolerance of important nodes such as cluster heads and core nodes.