A new covert communication method based on spatial modulation

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This paper investigates a covert communication system that utilizes spatial modulation (SM) and employs multiple antennas at the transmitter to transmit artificial noise (AN) with the objective of concealing covert information transmission . Firstly, a portion of the covert information is mapped on the antenna index and the rest is transmitted by different antennas via SM technology, which enhances covertness by leveraging unequal priori information and improves covert capacity. Secondly, the covert performance of the proposed scheme is evaluated separately under the assumption that the covert information follows Gaussian distribution (GD) and discrete constellation points distribution (DCPD). The closed-form expressions for Willie’s detection error probability (PDE) and the covert capacity of Bob are derived under both distributions, respectively. Additionally, Alice optimizes power allocation between AN and covert information to achieve trade-off between effectiveness and covertness while effectively utilizing system resources. Simulation results indicate that increasing total transmit power enhances covert capacity when power allocation factor is low or increasing power allocation factor enhances it when total transmit power is low while ensuring compliance with covert constraint. It is also proved that under the same covert constraint, the covert performance and covert capacity of GD under the proposed covert method are better than that of DCPD. Meanwhile, it is shown that our proposed strategy has a remarkable advantage over the covert scheme without employing SM.