# A Review of Counter-UAS Technologies for Cooperative Defensive Teams of Drones
## 5 Command and Control Systems  
The command-and-control system (C2) is one of the sub-systems of a CUS and it is an essential part for the implementation of the automated decision-making feature, which has been addressed in Section 2. Indeed, it is in charge of (possibly automated) high-level decision-making operations, such as:  
* Providing a classification of the attack scenario to assess its threat level, based on the feedbacks coming from the sensing system;
* Granting permission to fly over a specific protected area (for non-malicious drones);
* Selecting the proper mitigation techniques to be used based on the attack scenario and its threat level;
* Planning CUS operations and monitoring their execution. By means of the previous capabilities, the C2 system may aid the operator in facilitating the automated decision-making for mitigation actions. It can also perform the supervision and the management of the other sub-systems in a CUS. However, it may be convenient to distribute these functions by deploying them in dedicated systems, especially in the case of a cooperative drone-based CUS. In other words, the C2 system may be implemented not as a single centralized decision-making entity, but as a coordinated set of distributed decision-making entities. The rationale behind this assumption is as follows: a single management system could not be feasible in a complex application, such as a CUS with a higher number of platforms, in which some of the operations to be performed require a high degree of autonomy. A single decision-making entity would not be able to provide complete control of all the platforms, but it would have, at most, partial control over the operations performed by the individual platforms, despite having an overview of the threat represented by the malicious drone(s). A centralized decision-making system \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Neutralizers** & **Features** & **Limitations** & **Pros and Cons with Drones** \\ \hline Collision UAVs & \(\bullet\) & Require detection and tracking capabilities of the malicious drone to be impacted & \(\bullet\) & Require capabilities of tracking and approach to the malicious drone to be impacted & \(\bullet\) & The drone itself is a neutralizer \\  & \(\bullet\) & Are a hybrid system between a projectile and a small UAV & \(\bullet\) & The crash following the impact can cause collateral damage & \\  & \(\bullet\) & Effective for small drones & \(\bullet\) & Not appropriate at airports as they can cause side effects to other aircrafts & \(\bullet\) & Small distance from the malicious drone to neutralize can be obtained thanks to the mobility of mini drones \\  & \(\bullet\) & Can be projected from cannors or from flying platforms (included mini drones) & \(\bullet\) & The ready small distances from the malicious drone to have an effective neutralization & \(\bullet\) & The defensive drone must track and pursue the malicious one \\ Nets & \(\bullet\) & Nets equipped with parachutes allow a safe landing of the malicious drone & \(\bullet\) & Accuracy can depend on the surrounding environmental conditions & \(\bullet\) & Another approach is based on a team of drones forming a three-dimensional cluster around the malicious drone in order to limit or force its movement possibilities. The team of drones can be seen as a “net”. \\  & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 6: _Cont._would be extremely complex, both for the required computational capacity and for the communication network to be used to connect the various platforms. The latter, in fact, should be able to convey all the raw data collected by the platforms to the C2 system and to spread all the commands given by this latter system to the platforms of the CUS. Clearly, one of the most critical design aspects of the C2 system is related to its planning capability, which has to guarantee an automated execution and has to affect the defensive team as a whole. Indeed, this capability represents the key enabler for the automated decision-making feature of the system.