## 4 Discussion  
The proposed approach is devised for the IMT spectrum auction under the CA with an ascending rule, which consists of seven processes including collecting applications, scheduling the auction, conducting the auction, allocating spectrum blocks, payment, cancellation, and documentation. In South Korea, due to the importance of the IMT spectrum management in terms of development in the telecommunication field and its high correlation with the tax-paying budget of the people, the government and related agencies always consider how to design the IMT spectrum auction so that it can provide appropriate benefits to both the participants and the people. This study presents an IMT spectrum auction methodology that utilizes agent-based simulation for the first time. In particular, this study designs three types of auction bidder agents (the Aggressive bidder, the Moderate bidder, and the Conservative bidder) in Section 2.3.1 and the decision-making model of individual agents using the exponential utility theory, as shown in Equation (5). The actual agent demand (see Equation (6)) plays an important role in the auction process, which reflects the main characteristics of the CA determined by the available (or investment) budget, the price sensitivity of each agent, and the suggested price. Figure 4 shows that three types of bidder agents can express the demand for spectrum blocks depending on individual parameters. This shows that modeling or calibration that considers the intention of participants is possible by changing parameters in other IMT auctions. In order to accurately and easily model users' tendencies during the model usage process, a calibration model is presented in Section 2.3.3. It is important to model such diverse decision-making tendencies in auctions, as decision criteria may differ depending on the risk propensity of auction participants [32] and may also change depending on auction policies or participation conditions [33]. In fact, modeling decision-making behavior is a difficult problem, but this study utilizes the exponential utility theory which may simplify a very complex decision-making process relatively through several parameters, as in the model presented in Section 2.3.1. However, the exponential utility theory has been widely used because it is an analytical approach that can accurately analyze given results [34]. In addition, considering that the exponential utility theory has been utilized in modeling studies on existing auction participants [35; 36], this study selects the academically proven approach methodology called the exponential utility theory for decision-making behavior modeling. The performance of the proposed approach is verified through three cases to investigate why the initial bid price setting is important in the spectrum auction and how it can affect the auction results. First, the proposed calibration model (see Section 2.3.3) accurately calibrates the decision-making model with an R\({}^{2}\) of 96.38%, and simulations for three scenarios are performed; the results are analyzed in Section 3.3. In the low price case (5% of total annual revenue), due to the low initial price, all bidder agents want to purchase 10 spectrum blocks, which is the maximum number of spectrum blocks that can be bid for, and this high demand for spectrum blocks results in the auction not being able to be concluded within the limited number of bidding rounds of 50. This can be judged as an overheated auction that cannot be arbitrated [37], and such failure to bid can lead to a decrease in participants, including the waste of design costs for the auction, as all participants distrust the government-led IMT spectrum auction system [33]. In addition, the subsequent hypothetical analysis (see Figures 11 and 12) also shows that a higher initial price setting is needed to conclude the auction within 50 rounds.