Research On Covert Wireless Communication Technology-Analysis Of Covert Communication Performance With Node Assistance

Due to the broadcast characteristics of wireless communication,the transmission content has the risk of being intercepted by a third party.With the gradual promotion of the 5G and IOT's applications,wireless communication security will face greater challenges in the future.In recent years,a new theory called covert communication or low detection probability communication has been proposed,and some breakthrough results have been achieved,which has aroused widespread concern among scholars in the field of wireless communication security.Different from the traditional encryption technology to protect the integrity of the transmission content,covert communication emphasizes the protection of the transmission process itself,that is,reduces the detection probability of the eavesdropper,which will provide the most direct and effective security protection strategy.Since the time covert communication theory was individually proposed and analyzed is a little late,the domestic attention to this hot spot is not enough.Therefore,it is imperative to increase the investment in the study of covert communication theory and win the commanding heights in information confrontation.This thesis studies the construction and performance analysis of covert communication.This thesis first introduces the development of covert communication theory in recent years,and analyzes the basic problem of the covert capacity indicated by the square root law in covert communication.The basic assumptions and analysis methods in covert communication are described,and the rationality of the Gaussian distribution signal in the covert communication is proved analytically.At the same time,the limiting factors affecting the performance of covert communication are analyzed under the finite block length,and the progressive rate of capacity under the square root law is verified by numerical simulation.In order to address the theoretical limit that the covert communication capacity is zero,this thesis proposes a model that uses the artificial noise generated by the interfering node to assist in the implementation of covert communication.It is proved by the mathematical derivation that whether the transmit power of the interfering node is constant or uniform distributed can both achieve the covert communication with non-zero capacity.At the same time,the communication concealment and transmission validity are analyzed separately and compared by numerical result simulation.The results show that under a given covert restriction,uniformly varying interference power is more conducive to reducing power constraints and improving transmission efficiency.Furthermore,under the covert communication model composed of full-duplex receivers,two transmission strategies using channel feedback information are proposed: selecting the transmission timing and using power control,and analyzing and comparing the covert communication performance under the two strategies.The numerical results show that the optimal covert communication rate can be further improved by parameter optimization under both strategies,which provides a certain reference value for the theory to guide practice.