Research on an Outer Bound of Achievable Secrecy Rate Region for BCE

The security performance problems of broadcast channel with an eavesdropper (BCE) have been studied for many years in the field of communication. Many articles have given the meaningful results. However, almost no consequent of an outer bound on BCE has been given by previous work, especially, no significant results has been given. So this paper proposes and proves an outer bound of BCE by using information entropy, and further proves this outer bound is tight in the cut-set bound by max-flow min-cut theorem. It illustrates the outer bound is meaningful. Finally, by contrasting a variety of existing results, we can get that the outer bound in this paper include (tight) in the existing outer bound of BCE in the case of not considering the eavesdropper.