# Covert Surveillance Video Transmission with QAM Constellations Modulation
## 5 Conclusions  
In this paper, we delved into the intricacies of optimization techniques for the covert transmission of surveillance videos. Our primary focus centered on a meticulous exploration of the optimal probability of covert surveillance video transmission within the framework of QAM modulation. We employed mutual information as a metric for assessing covert transmission rate, leveraging its ability to quantify information shared between transmitted signals and the corresponding received signals. Simultaneously, we employed KL divergence as a measure to evaluate the covertness performance of transmitted signals. Based on the Taylor series expansion theory, we systematically conducted a thorough analysis, encompassing both the transmission rate and covertness aspects. In the considered  
Figure 7: Transmission rates using the different methods.  
scenarios, the fitting accuracy reached \(10^{-5}\), fully satisfying the precision requirements for our experimental objectives.  
Our investigation resulted in theoretical insights into the requisite conditions governing the optimal modulation probability of constellation points under QAM modulation. The covert transmission rate is \(\mathcal{O}(\sqrt{n})\) when our proposed theoretical conditions are satisfied; otherwise, it is \(\mathcal{O}(1)\), representing a significant disparity. Subsequent to this theoretical groundwork, we embarked on a series of experimental simulations, which were designed to rigorously validate our derived conclusions. Notably, our approach exhibited a commendable performance, showcasing superior transmission rates and increased covertness compared to existing methodologies. This success underscores the efficacy of our optimized strategy for the covert transmission of surveillance videos.  
In future work, our research trajectory includes an expansion of our focus beyond QAM modulation to encompass diverse transmission protocols for surveillance videos. This extension aims to develop additional covert transmission strategies and methodologies, contributing to the broader advancement of covert communication in surveillance scenarios.  
Conceptualization, S.Q. and G.L.; methodology, S.Q. and G.L.; software, J.Z. and X.J.; validation, S.Q. and X.J.; writing--original draft preparation, H.D. and G.L.; writing--review and editing, J.Z. and H.D.; visualization, H.D. and X.J.; supervision, S.Q. and J.Z.; funding acquisition, G.L. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Natural Science Foundation of China (grant numbers U1836104, 61801073, 61931004, and 62072250), the National Key Research and Development Program of China (grant number 2021 QY0700), and The Startup Foundation for Introducing Talent of NUIST (grant number 2021r039).  
Not applicable.  
The data presented in this study are available in article.  
The authors declare no conflicts of interest. The funders had no role in the design of the study, the collection, analyses, or interpretation of the data, the writing of the manuscript, or the decision to publish the results.  
The following abbreviations are used in this manuscript:  
\begin{tabular}{l l} HEVC & High-efficiency video coding \\ AV1 & AOMedia Video 1 \\ QAM & Quadrature amplitude modulation \\ AWGN & Additive white Gaussian noise \\ AVC & Advanced video coding \\ \end{tabular}