# Capacity Region of Gaussian Multiple-Access Channels with Energy Harvesting and Energy Cooperation

## TL;DR

This paper characterizes the capacity region of a Gaussian multiple-access channel with energy harvesting and cooperation, showing it matches traditional models with equivalent average power constraints and proposing practical power control policies.

## Contribution

It derives the capacity region for energy harvesting MACs with cooperation and demonstrates achievable policies for boundary points.

## Key findings

- Capacity region matches that of traditional Gaussian MAC with equivalent average power.
- Achievable boundary rates using save-and-forward power control and fixed energy cooperation.
- Energy cooperation effectively replaces average power constraints in energy harvesting scenarios.

## Abstract

We consider the capacity region of a $K$-user multiple access channel (MAC) with energy harvesting transmitters. Each user stores and schedules the randomly arriving energy using an energy buffer. Users can also perform energy cooperation by transmitting energy to other users or receiving energy from them. We derive the capacity region of this channel and show that 1) the capacity region coincides with that of a traditional $K$-user Gaussian MAC with energy cooperation, where the average power constraints are equal to the battery recharging rates of the energy harvesting case; 2) each rate on the capacity region boundary can be achieved using the save-and-forward power control and a fixed energy cooperation policy.