Spatial Modulation Covert Communication Assisted By Artificial Noise

Covert communication often used to confuse Willie by using the environment background signals or forging similar signals, which uses environment as a cover to increase the covertness of transmission signal. In this article, a spatial modulation (SM) covert communication system using a multi-antenna transmitter that transmits artificial noise (AN) to cover covert information transmission is considered. First, we hide some covert information in the antenna index by SM, which can improve covertness by using the unequal priori information, as well as improve the covert capacity. The achievable covert capacity is derived from the mutual information knowledge of information theory. Second, Alice transmits both covert information and AN with random power. In this case, Willie cannot make a correct judgement even if Alice generates very power fluctuations, which ensure the security of the communication process. Additionally, the power of AN and covert information is allocated and optimized by Alice, which can make better use of system resources and achieve the trade-off between covertness and effectiveness. The simulation results show that when the total transmit power of Alice exceeds −5dBw, the variation of power has no significant effect on covertness. Therefore, the covert capacity can be improved by increasing the transmit power while maintaining the covertness.