Research On Key Technologies Of Wireless Covert Communication

Nowadays,the human society is increasingly relying on wireless communication for information exchange,which makes the security and privacy of wireless communication being of growing importance.Covert communication,which ensures that the transmitter can transmit confidential message(CM)to the legitimate receiver without being detected by the warden,and also can hide the position information of the legitimate transmitter,is a new kind of secure communication with higher security level.In recent years,wireless covert communication is achieving an increasing attention in academia and industry.This paper focuses on wireless covert communication,and the main contributions are as follows:1)In order to analyze the influence of channel estimation on covert communication performance and warden's detection performance,applying the traditional channel estimation method to covert communication,a pilot and data symbol resource allocation method of maximizing signal-to-interference-plus-noise ratio(SINR)criterion is proposed.Firstly,it is proved that the transmission of pilot and data symbols with equal power(EP)can minimize the warden's detection performance,and then the numbers of pilot and data symbols are optimized.This EP scheme cannot guarantee the optimal communication performance between the receiver and transmitter,then a joint optimization algorithm of power and symbol number is proposed.The simulation results show that the proposed joint method of maximizing SINR(Max-SINR)is better than the EP method,but the latter can minimize the warden's detection performance.However,considering its low complexity,it can strike a good balance between performance and complexity.2)To explore the impact of a full-duplex receiver sending artificial noise(AN)on the covert communication with low-latency constraint,we maximize the throughput under constraint of the KL divergence,and yield the two following optimization problems:(1)For a given transmit power at Alice,how to optimize Bob's AN power allocation(PA);(2)How to jointly optimize the AN PA at Bob and the CM PA at Alice.Simulation and analysis show that with low-latency constraint,the optimal AN PA of the proposed joint method is derived to be a fixed value without requiring random choice.Besides,only when the receiver noise power at Bob is equal to or larger than the product of the noise power of Willie and the self-interference elimination coefficient of Bob,transmitting AN can improve the covert transmission performance.3)Since it is very difficult to obtain perfect channel state information(CSI)in practical applications,the transmit power at Alice and AN power at Bob are optimized to minimize the outage probability of Bob to achieve covert communication when the channel distribution information(CDI)is known.Simulation results show that when the CDI from Alice to Willie is available,there is an optimal AN PA strategy of minimizing Bob's outage probability,and the performance of covert communication is significantly better than that with perfect CSI available at Willie.