Joint Source-Channel Coding under a Covertness Constraint

The paper shows that in general a separate source coding and channel coding architecture is not optimal in multi access scenarios even under a covertness constraint. This stands in contrast to the single-user scenario where source-channel separation is optimal. The paper further shows that separation is optimal also for sending fully-correlated Gaussian sources over a Gaussian multiple-access channel (MAC). In all these scenarios (single-user or MAC), the covertness constraint imposes that the number of source symbols cannot scale linearly in the blocklength n, but only as √nηn for ηn the vanishing covertness constraint and n the blocklength.