## 1 Introduction
Instead of the aforementioned mathematical model-centric approaches [2], this study aims at identifying the best initial price of the auction using the simulation-based optimization approach. To this end, this study adopts agent-based simulation (ABS), which enables the behavior of telecommunications companies (or bidders) in the IMT spectrum auction to be mimicked. ABS is a well-known modeling and simulation (M&S) technique to evaluate the performance of a new policy or system based on the responses of multiple agents, who have their own decision-making processes under a dynamic environment [15; 16]. The proposed ABS consists of three major agent types: (1) the Aggressive bidder, (2) the Moderate bidder, and (3) the Conservative bidder. These agents are classified based on the competitive advantages (e.g., buying power) of the auction buyers (see Section 2.3 for more detail). The proposed simulation approach is implemented using AnyLogic 8.6.0 simulation softwareand calibrated with data of the IMT spectrum auction in South Korea. The differences between the proposed approach and existing studies are as follows. * It is the first method to implement the IMT spectrum auction process under the CA based on agent-based simulation. Unlike the macroscopic and top-down approaches of existing mathematical models, the decision-making process of individual agents, such as individual auction participants, is implemented, and a bottom-up approach is proposed by modeling the interrelationships between auction components. * Exponential utility is used to model the decision-making behavior of auction participants. Exponential utility is a well-known theory that describes the economic choice process of individuals. In conventional mathematical economics, it is expressed in a macroscopic way for predicting the decision-making results of a group (top-down approach), but in this study, it is used as a theory that describes the choice process of individual bidders (bottom-up approach). * The proposed approach is the first to apply the simulation-based optimization method to an IMT spectrum auction and analyze the optimal auction initial price; the proposed methodology is calibrated using actual IMT auction data from 2018 in Korea. As a result, this novel approach will contribute to the precise design of the clock auction (CA) with an ascending rule in the IMT spectrum, and it will be beneficial to the government agency that has to identify the appropriate value of the spectrum without causing harmful influence on fair competition in the IMT market for the public, as well as for existing service providers. Moreover, it will extend the applications of ABS in telecommunications and economics. The organization of the paper is as follows: Section 2 explains major approaches to the spectrum auction, and the price selection behavior of bidders in the auction. The ABS modeling approach in AnyLogic 8.5.0 and identification model of the best initial price of the auction are also introduced. Section 3 demonstrates the proposed approach with data of the IMT spectrum auction in South Korea in 2018. Section 4 discusses the theoretical and managerial implications of the proposed approach. Section 5 concludes this study and addresses future work.