# Centralized Coded Caching with User Cooperation

## TL;DR

This paper introduces a centralized coded caching scheme with user cooperation that optimally balances server and user transmissions, significantly reducing delay and proving order optimality.

## Contribution

A new deterministic placement and parallel delivery strategy for coded caching with user cooperation, achieving optimal load allocation and order optimality.

## Key findings

- Scheme reduces transmission delay significantly.
- Optimal load allocation between server and users.
- Proven order optimality with constant gap.

## Abstract

In this paper, we consider the coded-caching broadcast network with user cooperation, where a server connects with multiple users and the users can cooperate with each other through a cooperation network. We propose a centralized coded caching scheme based on a new deterministic placement strategy and a parallel delivery strategy. It is shown that the new scheme optimally allocate the communication loads on the server and users, obtaining cooperation gain and parallel gain that greatly reduces the transmission delay. Furthermore, we show that the number of users who parallelly send information should decrease when the users' caching size increases. In other words, letting more users parallelly send information could be harmful. Finally, we derive a constant multiplicative gap between the lower bound and upper bound on the transmission delay, which proves that our scheme is order optimal.