The Gaussian diamond-wiretap channel with conferencing relays

Abstract

In this letter, we consider the Gaussian diamond-wiretap channel with conferencing links between relays for the following three cases: 1) both conferencing links are confidential; 2) both conferencing links are public; and 3) one conferencing link is confidential, the other link is public, and the legitimate parties do not know which link is confidential or public. For all the cases, we establish the exact secure degrees of freedom (d.o.f.). Our results show that if at least one of conferencing links is confidential, the secure d.o.f. improves upon the case of no conferencing. In these cases of fully and partially confidential conferencing, it is shown to be sufficient to use the conferencing links only for transmitting noise symbols. On the other hand, if conferencing information is fully revealed to the eavesdropper, it is shown that there is no gain in secure d.o.f. due to conferencing, even if the conferencing information is also known to the legitimate destination.