On the Distributed Construction of a Collision-Free Schedule in Multi-Hop Packet Radio Networks

TL;DR

This paper presents a distributed protocol for multi-hop packet radio networks that constructs collision-free schedules, improving network efficiency by reducing collisions and channel fragmentation through a combination of deterministic and random backoffs.

Contribution

It introduces a novel distributed scheduling protocol that handles hidden terminals and uses delayed acknowledgements to enhance performance in multi-hop radio networks.

Findings

Collision-free protocol outperforms Aloha in efficiency.

Use of delayed acknowledgements reduces channel fragmentation.

Network converges to collision-free schedule within acceptable time.

Abstract

This paper introduces a protocol that distributively constructs a collision-free schedule for multi-hop packet radio networks in the presence of hidden terminals. As a preliminary step, each wireless station computes the schedule length after gathering information about the number of flows in its neighbourhood. Then, a combination of deterministic and random backoffs are used to reach a collision-free schedule. A deterministic backoff is used after successful transmissions and a random backoff is used otherwise. It is explained that the short acknowledgement control packets can easily result in channel time fragmentation and, to avoid this, the use of link layer delayed acknowledgements is advocated and implemented. The performance results show that a collision-free protocol easily outperforms a collision-prone protocol such as Aloha. The time that is required for the network to converge to a collision-free schedule is assessed by means of simulation.