Achieving Positive Covert Rate in Distributed Antenna System

Distributed antenna system attracts a lot of attentions due to its flexibility and high coverage. In this paper, covert communications in the distributed antenna system are considered, where multiple random located source nodes aim to communicate with a destination node without being detected by an eavesdropper. The sum of probabilities of detection errors is taken as the covertness metric. To exploit the space diversity, the equal gain transmission (EGT) strategy is employed. Then, the detection performance is analyzed and a tight upper bound of ergodic capacity is provided. It is found that a positive covert rate is achievable with $O(\sqrt{n})$ source nodes. Numerical results verify the correctness of the ergodic capacity and demonstrate the tightness of the proposed upper bound.