Degraded Broadcast Channel with Side Information, Confidential Messages and Noiseless Feedback

TL;DR

This paper explores the capacity regions of degraded broadcast channels with side information, confidential messages, and noiseless feedback, providing bounds and demonstrating how feedback enhances secrecy and capacity.

Contribution

It extends existing models by incorporating noiseless feedback, deriving bounds, and showing feedback's role as a secret key to improve confidentiality and capacity.

Findings

Feedback enlarges capacity-equivocation bounds.

Feedback acts as a secret key for enhanced secrecy.

Bounds are established for both causal and noncausal cases.

Abstract

In this paper, first, we investigate the model of degraded broadcast channel with side information and confidential messages. This work is from Steinberg's work on the degraded broadcast channel with causal and noncausal side information, and Csisz$\acute{a}$r-K\"{o}rner's work on broadcast channel with confidential messages. Inner and outer bounds on the capacity-equivocation regions are provided for the noncausal and causal cases. Superposition coding and double-binning technique are used in the corresponding achievability proofs. Then, we investigate the degraded broadcast channel with side information, confidential messages and noiseless feedback. The noiseless feedback is from the non-degraded receiver to the channel encoder. Inner and outer bounds on the capacity-equivocation region are provided for the noncausal case, and the capacity-equivocation region is determined for the causal case. Compared with the model without feedback, we find that the noiseless feedback helps to enlarge the inner bounds for both causal and noncausal cases. In the achievability proof of the feedback model, the noiseless feedback is used as a secret key shared by the non-degraded receiver and the transmitter, and therefore, the code construction for the feedback model is a combination of superposition coding, Gel'fand-Pinsker's binning, block Markov coding and Ahlswede-Cai's secret key on the feedback system.