## 3 Materials and Methods
### Cross-Domain Redundancy for Reliable ATM Communication with RED/BLACK Domains  
The typical architecture of air traffic management communication with RED/BLACK domains is shown in Figure 1, focusing on the segregation between RED and BLACK domains. In this context, \"RED\" would represent secure, sensitive, or classified networks, while \"BLACK\" refers to unclassified or less secure networks. There are two separate local area networks (LAN), one marked in black and the other in red, indicating the unclassified and classified domains, respectively. Each domain has its own set of local radios and remote radios, with the classified domain's elements marked in red, and the unclassified in black. The controller manages the interactions between these two domains. The two domains are kept separate to ensure that classified information remains secure and that there are clear distinctions between the types of information transmitted or received across these networks. The robustness of ATM systems is a critical factor in ensuring the safety of air navigation. A lapse in the efficacy of communication between air traffic controllers and pilots is not just problematic but potentially hazardous as a significant contributor to aviation accidents. The ATM system employs a variety of air traffic controllers--tower, approach, and departure, and route controllers--each reliant on independent communication channels operating at specific radio frequencies. These frequencies facilitate the uninterrupted interaction with aircraft across different phases of flight. In the complex environment of air traffic control centers, the communication network is dual-layered, comprising RED and BLACK domains to handle secure and non-secure information, respectively. Each air traffic controller is supported by two independent sets of radio stations (RS). The local set is within the air traffic control center for immediate access, while the remote set, consisting of more powerful RS, is typically housed at a distance located, as a rule, several kilometers from the airport, within a remote radio center. In this  
Figure 1: Architecture of air traffic management communication with RED/BLACK domains. case, the approach to ensuring the reliability of each of the radio centers, local and remote, is implemented in the same way, which allows them to be considered independently on the basis of the same model. The most effective method for increased reliability of communication in ATC multi-channel systems is to use \(N=k+n\) RS, where \(k\) is the number of ATM channels provided by a similar number of main radio stations (MRS) and \(n\) denotes a set of universal standby radios [31]. The voice communication system is the core component of this architecture, facilitating all necessary switching operations and frequency restructuring within the reserve. For RED domain controllers, who carry out highly responsible missions, it is imperative to ensure even greater reliability of their communication channels. One of the approaches to bolstering this reliability is the strategic utilization of the BLACK domain resources in contingency scenarios. If all backup RS in the RED domain were to fail, a pre-determined number of RS from the BLACK domain could be requisitioned as an additional reserve for domain RED. The reliability enhancement from this method is multi-fold. First, it provides an extra layer of fail-safes beyond the conventional redundancy already in place. Second, it introduces a level of flexibility in resource allocation that is uncommon in standard communication system designs. Third, the approach optimizes the utilization of available resources, effectively increasing the operational resilience of the system without necessitating the procurement of additional dedicated hardware. This paper aims to analyze the degree to which this innovative redundancy strategy improves the reliability of RED domain communication channels (CC).