Bidirectional Broadcast Channel Under Strong Secrecy and Cost Constraints

Ivana Marić, Shlomo Shitz Shamai, Osvaldo Simeone

Sara Al-Sayed, Aydin Sezgin

In this work, we investigate the Gaussian MIMO bidirectional broadcast wiretap channel, from the vantage point of optimal transmit strategy design, to fulfill a certain secrecy constraint. An achievable secrecy rate region is computed and the gap to the capacity region of the same channel without the secrecy constraint is upper-bounded. Moreover, for the case of single receive antennas at all terminals, beamforming optimality is proved for non-orthogonal channels to the legitimate receivers. Finally, a strategy to reduce the eavesdropper's rate without compromising the users' by artificial-noise transmission is proposed, and its optimization with respect to the quality of the relay's knowledge about the eavesdropper's channel is characterized.

Reihaneh Safavi–Naini, Huaxiong Wang

Ning Cai

Rafael F. Wyrembelski, Moritz Wiese, Holger Boche

To increase the spectral efficiency of future wireless networks, it is important to wisely integrate multiple services at the physical layer. Here the efficient integration of confidential services in the three-node bidirectional relay channel is studied. A relay node establishes a bidirectional communication between two other nodes using a decode-and-forward protocol, which is also known as two-way relaying. In the broadcast phase, the relay transmits not only the two bidirectional messages it received in the previous multiple access phase, but also an additional confidential message to one node while keeping the other node completely ignorant of it. The concept of strong information theoretic secrecy is used to ensure that the nonlegitimate node cannot decode the confidential message no matter what its computational resources are. Moreover, this implies that the average decoding error at the nonlegitimate node goes exponentially fast to one for any decoding strategy it may use. This results in the study of the bidirectional broadcast channel with confidential messages for which the strong secrecy capacity region is established. Furthermore, it is shown that the efficient integration of confidential messages with strong secrecy extends to such scenarios, where the relay further transmits an additional common message to both nodes.

Rafael F. Wyrembelski, Moritz Wiese, Holger Boche

To increase the spectral efficiency of future wireless networks, it is important to wisely integrate multiple services at the physical layer. Here we study the efficient integration of confidential services in bidirectional relay networks, where a relay node establishes a bidirectional communication between two other nodes using a decode-and-forward protocol. In the broadcast phase the relay transmits an additional confidential message to one node while keeping the other node completely ignorant of it. We use the concept of strong information theoretic security to ensure that the non-legitimate node cannot decode the confidential message no matter what its computational resources are. This results in the study of the bidirectional broadcast channel with confidential messages for which we establish the strong secrecy capacity region.