## 7 Conclusions  
Exploring the spectrum emerges as a vital avenue for governments to generate revenue, which can subsequently be allocated to social programs or infrastructure, thus incentivizing a wider population coverage. Selecting the optimal format for auctioning spectrum licenses is essential for the auctioneer to maximize efficiency and revenue. Furthermore, a thorough examination of participants' strategies may help mitigate the adoption and prevalence of detrimental behaviors during an auction through the implementation of carefully designed regulations. Examples noted in the writing of this article include the activity rule, AUSM, spectrum cap, bidding credits, and coverage obligations, among others.  
Throughout this article, we evaluated and compared the performance of the primary auction structures, both in terms of theoretical efficiency and in a real-world comparison of revenues stratified by country and format.  
Auctions, including English auctions, sealed bids, and second-price auctions, have been found to be inadequate because they do not consider the complementarities between the auctioned goods.  
The Simultaneous Multiple-Round Auction addresses these limitations by allowing the auctioneer to assess and extract the relative value of the license synergies as perceived by the participants. However, it is constrained by the computational power needed to accurately evaluate all offered offers, which hinders the effective price discovery between the parties involved.  
Finally, the Combinatorial Clock Auction emerges as an alternative to the Simultaneous Multiple-Round Auction (SMRA), aiming to address this specific issue by incorporating a stage specifically designed to facilitate price discovery. Simultaneously, it offers the auctioneer a broader range of options to consider for resource allocation.  
The level of adoption demonstrated by developed economies in North America, along with the higher revenues generated from spectrum auctions, appears to support the theoretical analysis presented by [22], suggesting that the CCA format tends to outperform other formats in terms of allocation efficiency. (It is worth noting that the North American spectrum market is highly competitive, among other factors, which may, in turn, influence prices in the US and Canada.).  
Additional studies are necessary to understand the unique characteristics of each country and the specific nuances of each dispute to generate revenue from spectrum licenses. The regulatory frameworks must also be evaluated to determine whether aparticular rule has a positive or negative impact, as well as to understand the requirements of each regulatory body when considering spectrum auctions.  
A continuous review of the intricacies of the primary auction structures is essential for projecting structural changes and adapting auction formats to meet the needs of the regulatory authorities in each country and their specific objectives.  
Conceptualization, X.L.T.J.; Investigation, R.T.R.d.S. and D.d.S.V.; Supervision, D.d.S.V. and X.L.T.J.; Project administration, X.L.T.J. All authors have read and agreed to the published version of the manuscript.  
This research was funded by ANATEL grant number 02-2023.  
The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.  
This work was supported by the National Telecommunications Agency [TED No 2-2023].  
The authors declare no conflicts of interest.