Throughput-Optimal Broadcast on Directed Acyclic Graphs

TL;DR

This paper introduces a new dynamic broadcast algorithm for wireless networks with directed acyclic graph topologies that achieves capacity without relying on complex spanning trees, simplifying implementation and improving delay.

Contribution

The paper presents a throughput-optimal broadcast algorithm for DAGs that uses local information and in-order delivery, avoiding global topological structures.

Findings

Achieves broadcast capacity in DAGs

Simplifies algorithm design by avoiding spanning trees

Demonstrates superior delay performance in simulations

Abstract

We study the problem of broadcasting packets in wireless networks. At each time slot, a network controller activates non-interfering links and forwards packets to all nodes at a common rate; the maximum rate is referred to as the broadcast capacity of the wireless network. Existing policies achieve the broadcast capacity by balancing traffic over a set of spanning trees, which are difficult to maintain in a large and time-varying wireless network. We propose a new dynamic algorithm that achieves the broadcast capacity when the underlying network topology is a directed acyclic graph (DAG). This algorithm utilizes local queue-length information, does not use any global topological structures such as spanning trees, and uses the idea of in-order packet delivery to all network nodes. Although the in-order packet delivery constraint leads to degraded throughput in cyclic graphs, we show that it is throughput optimal in DAGs and can be exploited to simplify the design and analysis of optimal algorithms. Our simulation results show that the proposed algorithm has superior delay performance as compared to tree-based approaches.