The wireless revolution
We are living in what is rapidly becoming a wireless world. Many years ago, I was interviewed and impetuously stated that, in the future, everything would be wirelessly connected to everything else. This was during a time when the industry was just switching over from 10BASE2 cabling to what was then known as 10BASET, now known as CAT6. I got a lot of flak over that statement, but here we are—on the verge of the Internet of Things. Many of you reading this have never known a world without Bluetooth, or computers, for that matter.
In the beginning, Ethernet was wireless; Messrs. Metcalf and Boggs coined the phrase "Ethernet" because the original transmission medium for the shared communication channel was by radio. The system was not reliable and subject to interference and frequent disruptions. Subsequent work by DARPA and Xerox on cabled networking systems spawned many different flavors of wired data communications; all of those have fallen away with the exception of what became the de facto networking standard, IEEE 802.3.
Not to say that other forms of networking are not used. RS-485 is alive and well and doing yeoman service in thousands of Modbus networks. There are still MAP systems out there, so I am told, using token-bus. But the vast majority of data communication done over wired systems is accomplished using Ethernet and the TCP/IP protocol suite.
The origin of the term "Wi-Fi" is clouded. It was allegedly coined from a contraction of the words "Wireless Fidelity," but according to a Wikipedia entry, this misconception stems from the advertising slogan "The Standard for Wireless Fidelity." The same entry states the name was a play on the term "Hi-Fi."
Throughout this series of articles, I will use the terms Wi-Fi and WLAN (wireless local area network) interchangeably to describe the technology.
Beginnings of Wi-Fi
Wi-Fi had its beginnings with the 1985 FCC ruling that released the 2.4 GHz Industrial, Scientific, and Medical (ISM) band for unlicensed use. This was followed in 2008 by the release of the 5 GHz U-NII band. These decisions allowed the use of 11 and 23 channels, respectively.
The IEEE 802.11 working group standardized Wi-Fi technology. The first standard to hit the street was the 802.11 "prime" standard, which allowed for a maximum data rate of 2 Mbps. Adoption of the technology was slow, owing to expensive access points, slow transmission rates, propagation and medium arbitration issues, and, most significantly, the lack of adequate security.
Shift to wireless
It is estimated that by 2015, 80% of all data communication will be wireless. It is essential for any control systems practitioner to be well versed in the state of the art. Presently, wireless speeds of 1 Gbps are theoretically possible with the newly ratified 802.11ac standard. As of April 1, 2014, the FCC has expanded the U-NII band by 100 Mhz of bandwidth, and is considering making another 150 MHz available for WLAN service.
Finally, to put a fine point on it, the economic value of unlicensed spectrum in the United States is estimated at $228 billion. This alone will continue to drive the technology to eventually replace most wired communication.
– Daniel E. Capano, owner and president, Diversified Technical Services Inc. of Stamford, Conn., is a certified wireless network administrator (CWNA). Edited by Mark T. Hoske, content manager, CFE Media, Control Engineering, email@example.com.
www.controleng.com/blogs will have additional wireless tutorials.
www.controleng.com/webcasts has wireless webcasts, some for PDH credit, including one featuring Capano as featured speaker, live June 10 at 1 p.m., CDT, and archived thereafter.
Control Engineering has a wireless page.