# On the Capacity Region of Optical Intensity Broadcast Channels

## TL;DR

This paper characterizes the capacity region of optical intensity broadcast channels under various constraints, providing tight bounds and asymptotic results at high SNR for multi-user scenarios.

## Contribution

It derives inner and outer bounds for the capacity region of OI-BCs using superposition coding and entropy power inequality, including high-SNR asymptotic capacity characterization.

## Key findings

- Inner and outer bounds match at high SNR
- Capacity region characterized for multi-user channels
- Bounds extend to general K-user broadcast channels

## Abstract

This paper investigates the capacity region of the optical intensity broadcast channels (OI-BCs), where the input is subject to a peak-intensity constraint, an average-intensity constraint, or both. By leveraging the decomposition results of several random variables, i.e., uniform, exponential, and truncated exponential random variables, and adopting a superposition coding (SC) scheme, the inner bound on the capacity region is derived. Then, the outer bound is derived by applying the conditional entropy power inequality (EPI). In the high signal-to-noise ratio (SNR) regime, the inner bound asymptotically matches the outer bound, thus characterizing the high-SNR asymptotic capacity region. The bounds are also extended to the general K-user BCs without loss of high-SNR asymptotic optimality.