Experiences in Deploying a Wireless Mesh Network Testbed for Traffic Control

By: 
Kun-chan Lan, Zhe Wang, Mahbub Hassan, Tim Moors, Rodney Berriman, Lavy Libman, Maximilian Ott, Bjorn Landfeldt, and Zainab Zaidi
Appears in: 
CCR October 2007

Wireless mesh networks (WMN) have attracted considerable interest in recent years as a convenient, flexible and low-cost alternative to wired communication infrastructures in many contexts. However, the great majority of research on metropolitan-scale WMN has been centered around maximization of available bandwidth, suitable for non-real-time applications such as Internet access for the general public. On the other hand, the suitability of WMN for missioncritical infrastructure applications remains by and large unknown, as protocols typically employed in WMN are, for the most part, not designed for real-time communications. In this paper, we describe the Smart Transport and Roads Communications (STaRComm) project at National ICT Australia (NICTA), which sets a goal of designing a wireless mesh network architecture to solve the communication needs of the traffic control system in Sydney, Australia. This system, known as SCATS (Sydney Coordinated Adaptive Traffic System) and used in over 100 cities around the world, connects a hierarchy of several thousand devices — from individual traffic light controllers to regional computers and the central Traffic Management Centre (TMC) - and places stringent requirements on the reliability and latency of the data exchanges. We discuss our experience in the deployment of an initial testbed consisting of 7 mesh nodes placed at intersections with traffic lights, and share the results and insights learned from our measurements and initial trials in the process.

Public Review By: 
Kevin Almeroth (University of California, Santa Barbara)

This paper talks about relaying messages to traffic signals using a wireless mesh network. Such a mesh network helps avoid the inconvenience of laying cables between traffic signals. This is a very appropriate application of multihop wireless mesh networks. The authors have done a good job in deploying a sample network as a first step towards creating a fully functional wireless mesh network-based traffic control system. The paper evaluates the packet losses, throughput, and round-trip latency observed in the sample network. While these are good metrics to evaluate, their preliminary evaluation is not yet sufficient to reveal the impact they will have on a real traffic control system.
There are some clear ways in which the paper can be extended and all of the reviewers thought this paper was a good first step. One future goal would be how the results generated can be used to explain how a mesh network can be constructed for the successful operation of the traffic control system. A future contribution of the paper could be to evaluate the feasibility of using wireless mesh networks for traffic control, by answering questions like: Can a wireless mesh network satisfy the delay and reliability requirements for a traffic control system (if one can define such requirements)? Does destructive interference become a bottleneck – and can it be avoided? Do the problems in keeping a wireless mesh working surpass the advantages one will receive over digging the roads to lay wired cables?