Finite Blocklength Covert Communications With Random Selection of Channel Use

This letter investigates the finite blocklength covert communications where transmitter Alice randomly chooses channel use according to probability
$\rho $
in the transmission block. To minimize the decoding error probability of a receiver Bob subject to the covert constraint on a detector Willie, we consider a new scheme that is changing the selection probability
$\rho $
. A proof is given for the first time that although Alice randomly chooses channel use for transmission, the received signal of each channel use at Willie in the transmission block satisfies the condition of independent and identical distribution (i.i.d). Subsequently, we examine the effect of channel use selection probability
$\rho $
on decoding error probability of Bob. By adjusting
$\rho $
, the decoding error probability can be decreased without changing the covert constraints.