Bounds on the secrecy capacity region of the degraded multiple-access relay wiretap channel

In this paper, we investigate the effects of an additional trusted relay node on the secrecy of the degraded multiple-access wiretap channel (DMAC-WT) by considering the model of the degraded multiple-access relay wiretap channel (DMARC-WT). Inner and outer bounds on the secrecy capacity regions of the DMARC-WT are provided for both the discrete memoryless and the Gaussian cases. For the Gaussian DMARC-WT, we find that in some particular cases, Tekin-Yener´s achievable secrecy rate region of the Gaussian DMAC-WT is enhanced by using this trusted relay node.