Wired vs. Wireless: Cost and ReliabilityNovember 1, 2005 By: Wise Guy Sensors
What's Wrong With Wires?
What's all this fuss about wireless communications? What's wrong with using wires, just as we've always done?
Signed, Jack Plugg
There's nothing wrong with wired communications, such as Ethernet, ModBus, or the perennial favorite, RS-232. And there will always be situations where a wired link makes more sense than a wireless link. It's just that wireless systems are continually becoming less expensive and more dependable, making them the better choice in more and more applications.
Here's why. The cost of wired communications—the cost of the wire, the connectors, and the labor needed to connect point A to point B—has remained constant or has increased slightly over the years. By contrast, the cost of wireless communications has dropped dramatically. High-speed wireless radio chips that cost $27 each just three years ago are now available for around $4. This is largely due to the phenomenon called "Moore's Law", which can be roughly paraphrased as "Anything built using silicon chips will become exponentially less expensive over time." And this trend will continue.
At the same time, wireless modems are becoming more reliable. Advanced signal-processing techniques and new network architectures that were merely an academic curiosity a few years ago are now practical to implement in wireless systems. In turn, these advances are finding their way into new standards and new products.
Wireless More Reliable Than Wired?
A friend of mine claims that wireless communications are sometimes more reliable than wired communications. He's crazy, right?
Signed, Knott Krazie
I wouldn't commit your friend to the loony bin just yet: wireless systems can be more reliable than wired systems in specific applications. Here are just a few examples:
"Chainsaw-resistant" connections. Before some evildoer can cut a connection, they have to know it is there. Unlike wired connections, wireless connections are invisible, which offers significant protection against malicious attacks. An intruder could launch an attack with a radio-frequency jammer, but advanced radios, such as spread spectrum (SS) and ultra-wideband (UWB), coupled with advanced network designs—such as redundant mesh architectures—work together to create communications networks that are extremely difficult to disrupt, whether deliberately or by accident.
Fire-and backhoe-proof connections. Wired connections can be broken by fires and backhoes; wireless connections can't. Consider an office building with smoke detectors that use "home-run" wiring to a central control panel. In addition to being expensive, home-run wiring is prone to massive failure because a fire can burn through all the connections in one place. By contrast, wireless mesh networking can provide redundant, fail-safe monitoring of all of the smoke detectors in a building.
Avoiding slip rings. Any time you need to make a measurement on a rotating object, you should consider a wireless link. Short-range, low-cost radio transmitters are being put into commercial use for measuring tire pressure from inside the tires of light vehicles manufactured in the U.S. For example, in addition to satisfying the mandates of the National Highway Traffic Safety Administration for tire pressure monitoring systems, this approach avoids the cost and complexity of connections made using mechanical slip rings.