Relay-Assisted Uplink Covert Communication in the Presence of Multi-Antenna Warden and Uninformed Jamming

Covert wireless communication intends to prevent hostile surveillance but is threatened by the powerful multi-antenna detection technique. In this paper, we investigate finite blocklength covert communication assisted by a multi-antenna relay station and a multi-antenna destination to fight against hostile detection from a warden also equipped with multiple antennas and interference from an uninformed jammer. In order to achieve optimal covert communication performance, we formulate the optimization problems in the single-user and the frequency division multiple access (FDMA) multi-user scenarios separately. In the single-user scenario, we design a cooperative beamforming strategy for the relay and the destination to maximize their received signal-to-interference-plus-noise (SINR). Then in the multi-user scenario, we utilize the above beamforming strategy and propose a majorization-minimization-based relay's power allocation algorithm to maximize the total covert throughput rate. The numerical results are provided to depict the effectiveness of the proposed scheme, and we address how the jamming power and the numbers of antennas affect covert communication based on these numerical results and theoretical analysis.