Feedback Coding Schemes for the Broadcast Channel with Mutual Secrecy Requirement

TL;DR

This paper investigates how feedback can enhance physical layer security in broadcast channels with mutual secrecy, proposing new coding schemes and bounds to improve secrecy capacity in wireless communication systems.

Contribution

It introduces two novel feedback coding schemes and bounds for the broadcast channel with mutual secrecy, expanding understanding of feedback's role in physical layer security.

Findings

Proposed two inner bounds on secrecy capacity with feedback.

Derived an outer bound for the secrecy capacity region.

Demonstrated the effectiveness of schemes through examples.

Abstract

Recently, the physical layer security (PLS) of the communication systems has been shown to be enhanced by using legal receiver's feedback. The present secret key based feedback scheme mainly focuses on producing key from the feedback and using this key to protect part of the transmitted message. However, this feedback scheme has been proved only optimal for several degraded cases. The broadcast channel with mutual secrecy requirement (BC-MSR) is important as it constitutes the essence of physical layer security (PLS) in the down-link of the wireless communication systems. In this paper, we investigate the feedback effects on the BC-MSR, and propose two inner bounds and one outer bound on the secrecy capacity region of the BC-MSR with noiseless feedback. One inner bound is constructed according to the already existing secret key based feedback coding scheme for the wiretap channel, and the other is constructed by a hybrid coding scheme using feedback to generate not only keys protecting the transmitted messages but also cooperative messages helping the receivers to improve their decoding performance. The performance of the proposed feedback schemes and the gap between the inner and outer bounds are further explained via two examples.