# Cooperative Multi-Sender Index Coding

## TL;DR

This paper introduces a novel cooperative coding scheme for multi-sender index coding, improving capacity bounds and surpassing previous methods through new coding components and strategic sender cooperation.

## Contribution

It proposes the Cooperative Composite Coding (CCC) scheme, addressing limitations of existing methods and achieving optimality in certain index-coding scenarios.

## Key findings

- CCC can strictly outperform partitioned DCC.
- Capacity regions are established for specific examples.
- CCC demonstrates advantages over non-cooperative schemes.

## Abstract

In this paper, we propose a new coding scheme and establish new bounds on the capacity region for the multi-sender unicast index-coding problem. We revisit existing partitioned Distributed Composite Coding (DCC) proposed by Sadeghi et al. and identify its limitations in the implementation of multi-sender composite coding and in the strategy of sender partitioning. We then propose two new coding components to overcome these limitations and develop a multi-sender Cooperative Composite Coding (CCC). We show that CCC can strictly improve upon partitioned DCC, and is the key to achieve optimality for a number of index-coding instances. The usefulness of CCC and its special cases is illuminated via non-trivial examples, and the capacity region is established for each example. Comparisons between CCC and other non-cooperative schemes in recent works are also provided to further demonstrate the advantage of CCC.