Contention Resolution for Coded Radio Networks

TL;DR

This paper introduces a new backoff protocol for coded radio networks that leverages simultaneous transmissions and interference cancellation, achieving near-optimal throughput and surpassing traditional bounds.

Contribution

It proposes the Decodable Backoff Algorithm, a novel randomized protocol that exploits modern radio capabilities to improve throughput beyond traditional limits.

Findings

Achieves near-1 throughput in coded radio networks.

Breaks the constant throughput lower bound of traditional radio protocols.

Demonstrates the power of interference cancellation in protocol design.

Abstract

Randomized backoff protocols, such as exponential backoff, are a powerful tool for managing access to a shared resource, often a wireless communication channel (e.g., [1]). For a wireless device to transmit successfully, it uses a backoff protocol to ensure exclusive access to the channel. Modern radios, however, do not need exclusive access to the channel to communicate; in particular, they have the ability to receive useful information even when more than one device transmits at the same time. These capabilities have now been exploited for many years by systems that rely on interference cancellation, physical layer network coding and analog network coding to improve efficiency. For example, Zigzag decoding [56] demonstrated how a base station can decode messages sent by multiple devices simultaneously. In this paper, we address the following question: Can we design a backoff protocol that is better than exponential backoff when exclusive channel access is not required. We define the Coded Radio Network Model, which generalizes traditional radio network models (e.g., [30]). We then introduce the Decodable Backoff Algorithm, a randomized backoff protocol that achieves an optimal throughput of $1-o(1)$. (Throughput $1$ is optimal, as simultaneous reception does not increase the channel capacity.) The algorithm breaks the constant throughput lower bound for traditional radio networks [47-49], showing the power of these new hardware capabilities.