wireless ad hoc networking

592 Wireless Ad Hoc Networking
costs, and warranty exposure. Demonstrating a working RF mesh in test
rigs yields very different results from a trial in situ in a real environment.
The RF mesh sometimes is not simple for wide-scale deployment. The first
step is to carefully evaluate real-world communication range, battery life,
and life-cycle costs.
The data and information to be communicated within industrial environments
is usually the state information based on small packets associated
with insensitive environments and timing requirements. The data are usually
temperatures, humidity levels, vibrations, atmospheric pollution levels,
chemicals, and electromagnetic noise. The desired throughput of the network
is relatively low in contrast to the reliability requirements. Note that
wireless communication should be avoided if deterministic transmission
with latency under 10 ms is desirable.
In many situations, power-line signaling offers a viable alternative. Most
of the control devices in these applications require a connection to electric
power, be it AC or DC voltage, making power-line signaling an ideal
solution. For free topology, twisted pair wiring even offers proven reliability,
no without battery replacement issues, and with very low maintenance
costs. For overhead and emergency lighting devices, power line is a better
and more reliable alternative to RF. 29
We have no doubt that RF technology will improve over time; however,
we do not believe that manufacturers should be test vehicles for
untried technology. RF technology suppliers should continue developing
it until they can produce robust field-proven solutions. The value of RF
technology—if it can be made to work well at low cost—appears clear
for a range of battery-powered sensor-monitoring applications. The value
of mesh networking, on the other hand, has yet to be field-proven in
control applications in which its sole purpose today is to compensate for
poor-quality radios. 30
Sensor network influences many factors including fault tolerance, scalability,
production costs, operating environment, sensor network topology,
hardware constraints, transmission media, and power consumption. 31
References
1. Lawrenz, W., Worldwide status of CAN—Present and future, 2nd International
CAN Conference, ICC-95, London, 3–4 October 1995.
2. Foster, G.T., Glover, J.P., and Warwick, K., Successful LonWorks based
machines for PCB manufacture, Proceedings of the LonUsers International
Fall Conference, Germany, 17 June, 1996.
3. Ericssion, G., A comparison of three fieldbus protocol: FIP, Profibus, and
Masterfieldbus, Proceedings of the International Workshop on Mechatronical
Computer Systems for Perception and Action, Paris, 3–4 June, 1993.