Advances in security, data-transmission reliability, and environmental packaging have readied wireless Ethernet for demanding industrial applications.
As Ethernet and Internet Protocol (IP) connectivity quickly become the “serial port” of the future, it is clear wireless technology trends will closely follow, providing ever-greater network and data access.
Wireless Ethernet capabilities via technology based on public standard IEEE 802.11 has gained commercial success. A quick look at available wireless networks from your laptop in virtually any public place or even your residential neighborhood is sure to find few.
However, just because a technology is approaching critical mass in the commercial world, does that mean it is ready for use in industrial applications?
While industry asked this question and answered regarding wired Ethernet (yes), it still remains a viable query regarding wireless applications. In addition to providing a broad comparison of different spread spectrum wireless technologies currently deployed in industrial automation applications, this article will explore the industrial use of public standard IEEE 802.11 technology.
Three Modulation Techniques
Wireless is a shared medium; therefore, different techniques are necessary to assure multiple signals can coexist in the same frequency range. The allocation of frequency for different uses is typically the role of government agencies.
In the U.S., this agency is the Federal Communication Commission (FCC). Typically, government agencies set aside some spectrum for public use. Different users and applications must share this public use; therefore for unlicensed applications, there is typically a limit set for the power that can be transmitted, and additionally some type of spectrum spreading technique is necessary. The allocation of frequencies requires sharing of frequencies when at all possible.
The requirement for spread spectrum in unlicensed applications is a good thing in terms of robustness and reliability for industrial applications. Spreading the communication over a wider frequency range means the signal transmission more readily overcomes EMI or RFI…