Jamming Aided Covert Communication With Multiple Receivers

We consider that a transmitter covertly communicates with multiple receivers under the help of friendly jammer. The messages intended for different are transmitted in mutually orthogonal frequency bands. An adversary observes all these bands aiming at detecting whether or not communication occurs, while jammer broadcasts jamming signals to degrade detection performance adversary. block Rayleigh fading channel model and evaluate covert two situations: 1) wireless channels vary slowly such transmission ends within one coherent time block, 2) fast have changed several times before whole is finished. In former case, subject covertness constraint, we maximize sum effective rates by optimizing transmit power allocation rate each receiver. latter take training process into consideration, ergodic pilot length. Though both optimization problems non-convex, presented methods find their global optimal solutions. Besides, also present sub-optimal solutions lower computational complexities. Numerical results situations.