Though not shown in Figure 1, in addition to the different protocols, there are also a number of different license-free frequencies, such as 900 MHz, 2.4 GHz and 5.8 Ghz, used as the carriers for these signals. Each frequency has its advantages and challenges regarding distance and bandwidth, but that is a topic we will cover in more detail in future columns. It is the frequency or carrier that is the physical layer in the wireless world that is equivalent to the cable, and it is the protocol that determines the handshaking and composition of the packet.
As shown in Figure 1, each protocol is targeted at different types of applications. These different needs dictate different technologies and they're not necessarily interchangeable. The majority are targeted at the consumer market, though some may only be suited to a relatively small niche, such as ZigBee and the industrial field sensor network protocols like WirelessHART.
Despite WirelessHART being perceived as the market leader among the non-proprietary protocols, recent statistics demonstrate that its adoption is a slow process. The HART Communications Foundation says 8000 to 10,000 systems are installed, which to me says the majority of these users are "tire kickers," installing small systems to see how the technology works, and that most of these systems are from a single manufacturer, who announced it also has approximately 8000 to 10,000 systems installed.
These numbers confirm what I have observed as the technology adoption cycle for industrial applications: it takes 10 to 15 years before a technology is considered "mainstream." The first five years are "tire kickers," the next five see the technology start to be included in specifications of large projects, and then once these plants have been installed and proven to work, 5+ years later, the technology is considered useable. Industrial wireless is presently in the first part of the cycle.
As we go forward with this column, we will talk about the different ways in which wireless can and will change our approach to automation and control and give you some thoughts on why or why not and where wireless could be applicable to solving your process connection problems. One thing is certain: Restricting your thought processes to the idea that wireless is the same as wire without the copper will not be what we discuss here.
Wireless opens an entirely new spectrum of opportunities from field sensors through backhaul networks to data integration. It's my intention to challenge the tradition and in doing so we will enjoy the benefits of technology as a means to increased productivity, as well as a safer and more environmentally responsible future.