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How Wifi happened overnight: the history of Part 15

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By Mia Kiesman

This device complies with part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) This device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation.

This incantation has been repeated billions of times: embossed into the injection molded cases of cheap toys, printed on stickers slapped on the bottom of WiFi routers, and tattooed on the back of your local hacker 1. But what the hell does it actually mean? In short, it’s the regulation that allows unlicensed use of certain types of radio transmittors on certain frequencies. To get that far however, three elements had to come together:

  1. The Federal Communications Commission regulates the use of the electromagnetic spectrum in the United States of America2. This is necessary since the spectrum is a public and limited resource, with little marginal cost for overuse. Most of the FCC’s power is exerted through issuing licenses to individual broadcasters, such as terrestrial radio stations (anyone with a WKRP-esque callsign). However, the original legislation didn’t consider that almost all electrical devices, especially radio receivers due to heterodyning, emit some radio energy. So, legislation was amended in 1938 to allow low power, unlicensed transmissions: “What we are concerned with immediately is the problem of interference. If certain low power devices can be used without interfering with radio communications, there would appear to be no engineering reason for suppressing their use”3 - FCC chief engineer Ewell Jett, 19384. This exception came to be known as Part 15, continuing America’s annoying tradition of naming incredibly important policies after random numbers. They were added on and amended to in an ad-hoc manner from the 1930s through the end of the 1970s as manufacturers realized these non-interfering transmissions could be used for things like RC toys and cordless phones. The regulations became a labyrinthian mess of obsolete rules, one off exceptions, and inaccessibility, so a push was started in the early 80s to revamp them. Meanwhile, in the Commonwealth…

  2. Percy Spencer was a Mainer who, like many of us, left his rural home to get an engineering job in suburban Boston5. In his case, he was working for the large defense contractor Raytheon testing their newly invented magnetrons6. He notices that the candy bar in his pocket has melted: this is of course, the invention of the microwave oven7. One of the first uses of so called Radar Ranges were on ships and jets, as their fast heating time and lack of combustable fuel made them a natural fit. Because they would be moving between countries, the International Telecommunication Union reserved 2.4GHz for Industrial, Scientific, and Medical use, as the resonant frequency of water mandated the use of this specific band8. This meant that no device would broadcast on that frequency, due leaky microwaves causing interference, creating one of the few globally empty radio bands.

  3. In the 1960s through the 70s, due to miniaturization of technology, two-way radios had become small, efficient, and cheap enough to be installed into cars, a practice pioneered by Motorola9. If you want to speak with someone without a radio, the telephone network was the natural way to accomplish this, so by the 1970s most American cities had mobile phone service. This is NOT cell phone service, as frequency bands were shared across entire cities and so were often congested. This prompted research into how to more efficiently use spectrum, and in 1978 a paper suggested using “spread-spectrum” radio, which uses a wider bandwidth signal at lower power to achieve the same data rate10. This reduces the power use of the transmitter, and makes it more immune to interference and eavesdropping. This helps the implementation of smaller-area frequency “cells”, which allows for reuse of a given frequency within a metro area, ultimately greatly increasing capacity.

Since the FCC was essentially overhauling Part 15 regulations, it provided an opportunity for officials to get their pet projects into law. Michael Marcus11 had seen spread spectrum radio was in the academic zeitgeist due to the 1978 paper, and his time in the military proved how useful it was. However, it wasn’t established enough to give an entire spectrum to. Luckily there was this huge band of “junk” spectrum around 2.4 GHz which was unused worldwide due to microwave interference, a type of interference spread spectrum radio is almost immune to. So, a MITRE study was commissioned, the public was consulted, and finally in 1985, spread spectrum communications in the 2.4 Ghz bands were established, along with 5, 6, and 0.9 Ghz 12.

This law created a bit of a land rush13 for start-ups creating spread spectrum radios. Like many standards, the first customers were specialized corporate users who could justify the cost and had the power to outfit an area with all compatible hardware. The product line certified for use of this new spectrum was the Telxon Aironet, essentially a wireless serial cable replacement meant for PoS and warehouse use14. This serial functionally was repeated with early Bluetooth devices, as it’s a useful way to shoehorn in new standards into existing products.

1989 brought clarification to what qualified a device as spread spectrum, and further emboldened development in the space. A 1984 startup named Proxim released RangeLAN in 1991, an early popular wireless LAN standard. This became a somewhat de-facto standard in corporate campus environments. Along with selling complete solutions, they also sold their wireless chipsets to other manufacturers.

The IEEE committee on LANs (802) worked from 1994 to 199715 to produce a spread-spectrum LAN, and ended up issuing 3 standards, which is not a fucking standard at all! In parallel, two private standards were developing16. One was HomeRF, made by a consortium of who else but Microsoft, Intel, Compaq, IBM, HP, et al, to make a standard with the home PC as the center17. This is a similar strategy to Apple’s 2001 Digital Hub strategy, yet Apple would quite influentially not take this strategy (more on that later). It also incorporated DECT18. In parallel, since many vendors were releasing products based on Proxim chips, Proxim themselves created an interoperability forum to make these devices compatible19. Since many HomeRF devices had those same chipsets, they could also roam onto those networks, which were more common in corporate environments.

Those scamps at the IEEE hadn’t given up the ghost though, and had the benefit of waiting a few years to create their 4th attempt at a standard. It was clear before launch that HomeRF and RangeLAN speeds weren’t suitable for life in the new millennium. The FCC changed the rules on symbol use, which allowed 802.11b to reach the blistering speed of 11 MBps with minor changes20.

Apple was in the midst of their reinvention, and jumped at the opportunity to include wireless in their internet appliance strategy. The release of the Airport line in 1999 and integration into the incredibly popular iMac and iBook lines essentially instantly killed HomeRF and RangeLAN21. The use of an open standard, mature chipsets from many manufacturers, and blistering consumer demand made 802.11b a stunningly quick success. In less than a decade, WiFi went from a niche corporate standard, to a technology that had complete consumer knowledge and had been deployed in a broad swath of public places and houses22. Even Nintendo, famous for their use of “withered technology” included WiFi in the DS, which started development a mere 7 years after the standard was published.

P.S. I tried to separate out the footnotes from the citations but it didn’t work, sorry!

  1. Citation: this awesome dream I had ↩︎

  2. As of the time of publication ↩︎

  3. K. R. Carter, “Unlicensed to kill: a brief history of the Part 15 rules,” INFO, vol. 11, no. 5, pp. 8–18, Aug. 2009, doi: 10.1108/14636690910989306.’ ↩︎

  4. Some sources remark that “certain medical devices” were already using short distance radio transmissions, and I would love to know what the hell that would be in 1938, but it cites an FCC docket that’s unavailable to me. Also Ewell Jett is a kickass name ↩︎

  5. D. Murray, “Percy Spencer and His Itch to Know,” Reader’s Digest, Sep. 1958. https://web.archive.org/web/20050306112532/http://members.aol.com/spencerlab/history/readdig.htm ↩︎

  6. Percy Spencer has a truly harrowing life story. He is the only person I’ve written about who is a double orphan, and got his electrical engineering skills through being randomly selected to wire the sawmill he worked at which like…woof. ↩︎

  7. The fact that he was standing close enough to one where it melted that is terrifying, but probably didn’t break Spencer’s top 20 ↩︎

  8. “Documents of the International Radio Conference - Doc. No. 1-100 - No. 28 R-E.” ITU, 1947. http://handle.itu.int/11.1004/020.1000/4.62.51.en.101 ↩︎

  9. A combination of Motor and Ola, which was apparently a trendy suffix for companies having to do with sound since the pianola was so popular. what. ↩︎

  10. G. R. Cooper and R. W. Nettleton, “A spread-spectrum technique for high-capacity mobile communications,” IEEE Trans. Veh. Technol., vol. 27, no. 4, pp. 264–275, Nov. 1978, doi: 10.1109/T-VT.1978.23758. ↩︎

  11. Many of the sources around this topic come from his consulting site, and he still seems to have a bit of an axe to grind about his treatment by the FCC. ↩︎

  12. “Wi-Fi/Bluetooth/CDMA History,” Marcus Spectrum Solutions LLC. https://www.marcus-spectrum.com/page4/SSHist.html ↩︎

  13. Minus the genocide ↩︎

  14. M. Brown, “Using Wi-Fi? Thank a 35 year-old FCC decision which laid the path for today’s age of connectivity,” Cisco Blogs. https://blogs.cisco.com/gov/using-wi-fi-thank-a-35-year-old-fcc-decision-which-laid-the-path-for-todays-age-of-connectivity ↩︎

  15. “IEEE 802.11 ARCHIVE DOCUMENTATION.” https://www.ieee802.org/11/Documents/DocumentArchives/ ↩︎

  16. I reckon we got ourselves a good old-fashioned format war! ↩︎

  17. E. Myers, “HomeRF Overview and Market Positioning.” PaloWireless.com, 1999ish. https://www.cazitech.com/HomeRF_Overview+Mkt_Posn.htm ↩︎

  18. WOOOOO DECT, LET’S GO DECT, LOVE DECT BABY!!! ↩︎

  19. “Mobile data network industry leaders form Wireless LAN Interoperability Forum,” WLIF, San Francisco, May 1996. https://web.archive.org/web/19990427031011/http://www.wlif.com/press/52096.html ↩︎

  20. ET Docket No. 99-231 https://docs.fcc.gov/public/attachments/FCC-02-151A1.pdf ↩︎

  21. The original AirPort basestation ran on a goddamned 486 of all things, making it Apple’s first exclusively x86 product ↩︎

  22. Citation: I was a very nerdy child armed with a Dell Inspiron ↩︎

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