# Dispensing with Noise Forward in the "Weak" Relay-Eavesdropper Channel

## TL;DR

This paper introduces a new decoding scheme for the weak relay-eavesdropper channel that reduces delay and simplifies analysis by eliminating noise forwarding, while optimizing secrecy rates through tailored codebook and bin size choices.

## Contribution

It proposes a novel sliding window decoding method with reduced delay that does not rely on noise forwarding, enhancing practical applicability and analytical tractability.

## Key findings

- Reduced decoding delay with sliding window scheme
- Maximized secrecy rate through optimized codebook and bin sizes
- Multiblock equivocation calculations for security analysis

## Abstract

The "weak" relay-eavesdropper channel was first studied by Lai and El Gamal, whose achievable scheme introduced noise forwarding (NF) and used backward decoding. We suggest a novel sliding window decoding scheme with a two block decoding delay, where the relay uses compress-forward with Wyner-Ziv (WZ) binning but does not use NF. Wireless engineers will welcome the reduced decoding delay. Sliding window decoding mandates multiblock equivocation calculations; dispensing with NF enables it. We identify nine regimes and develop a case-by-case choice of relay channel codebook and WZ bin sizes to maximize the secrecy rate. The multiblock equivocation calculations may be of independent interest.