## 1 Introduction
were the first to use complex network theory in the field of ATC, and constructed a complex network model for the problem of airspace complexity evaluation [11]. Then, [PERSON] chose to use the looming effect between aircraft for the description of the airspace complexity problem [12; 13; 14; 15]. [PERSON] discussed the relationship between controller brain workload and air traffic dynamic complexity [16]. [PERSON] performed the evaluation of air traffic complexity by constructing a flight state network and used it to evaluate flight safety and quality accordingly [17; 18]. [PERSON] proposed to construct a complex network using the velocity barrier method to explain the air traffic complexity, performed conflict identification and detection, and proposed a resolution strategy based on the optimal dominating set [19; 20]. Since the above studies mainly carry out the construction and analysis of network models from the two-dimensional level, which is partially different from the real situation, they cannot effectively analyze the relationship between the effects of different altitude layers. Therefore, this paper proposes the application of the velocity barrier method from a three-dimensional perspective, combining the aircraft position, velocity and heading information as well as the flight protection zone information to be satisfied during flight for the construction of a single-layer flight conflict complex network. However, in practice, a completely independent single-layer complex network is almost non-existent. The vast majority of systems are formed by several or even more networks coupled and interdependent on each other, and ATC systems are no exception. The concept of interdependent networks was first introduced by [PERSON] in 2010, which considered that each layer of the network has the same number of nodes and only one-to-one correspondence [21]. Subsequently, [PERSON] modified this restriction by proposing that only a random number of nodes in each layer of the network are one-to-one inter dependent on nodes in another layer of the network [22]. Finally, the basic theory of interdependent networks was finally refined by [PERSON], who proposed that nodes in a certain layer of the network form connected edges with nodes between other networks according to a certain probability [23]. [PERSON] was the first to introduce the theory of interdependent networks in the field of civil aviation and constructed the interdependent networks using airports, control sectors and flight paths [24; 25]. [PERSON] constructed a control-flight state interdependent network and analyzed the network characteristics and evolution process [26; 27]. Based on the analysis of the above-mentioned studies, it can be found that, as a part of modern ATC system, controllers are responsible for the control of aircraft in their control sectors, and at the same time there are control work handover relationships with the surrounding controllers and their control sectors. The control network with controllers as nodes and the flight conflict network with aircraft as nodes satisfy the conditions for the construction of interdependent networks. At the same time, the relevant indexes of the complex network can make a reasonable prediction and assessment of the air situation and make a prediction and assessment of the controller workload. Therefore, this paper constructs an interdependent network model by combining the control network and the flight conflict network, and analyzes and studies the indicators of the network on this basis to make a reasonable prediction and assessment of the controller workload.