Monday, July 14, 2008

In Which We Consider the History of Unlicensed Wireless Broadband

In this post, we consider the history of unlicensed radio spectrum, sometimes known as Part 15 Spectrum. This is a radio service that most of us are familiar with, but perhaps few have appreciated what a significant paradigm shift it represents. Unlicensed Part 15 Spectrum is found in garage door openers, remote control toys, and WiFi Internet Access.

Traditionally, the FCC doles out the right to use radio spectrum through the use of licenses. These set forth who can use what frequencies, in what locations, at what power levels, and sometimes for what purposes. Yet Part 15 sets aside a portion of the radio spectrum where no license is needed. How did this come about?

Our story begins in 1894 with Guglielmo Marconi. While young Marconi was living in Italy, he read an article about the possibility of something beyond the imagination: electronic communications without wires! Marconi was mesmerized - and he engaged on a quest to transmit telegraphs without telegraph wires.

Unfortunately, his home of Italy expressed little interest in this innovation. Britain, and particularly British Navy with its need to communicate with its ships at sea – was another matter. Marconi moved his family to England where he received a patent for his wireless telegraphs in 1897. He set up the Wireless Telegraph and Signal Co., and sought to capitalize on his inventions during the Industrial era. Four years later Marconi successfully transmitted a wireless signal across the Atlantic Ocean. Marconi quickly built a radio empire, donating radios to ships in order to demonstrate their utility, and only allowing radio stations using Marconi radios to communicate with other radio stations that used Marconi radios (sounds a bit like Customer Premises Equipment and Hush-a-phone issues).

Governments took notice. Communications has always been of military strategic importance from Pheidippides’ marathon run to Athens, to modern day spread spectrum radio devices that can elude jamming. The ability of a government to communicate with its fleet at sea presented a clear military advantage. The US Navy Department constructed radio stations all along the coast of the United States and equipped Navy ships with radios. This meant that, at the turn of the century, the lead federal agency regulating spectrum and radio usage was the US Navy (not the FCC).

Radio technology was in its infancy. Transmitting and receiving radios were not necessarily tuned to the same frequencies – nor was their much agreement or standardization about what frequencies should be used, or by whom. As a result, radio operators followed the principle of brute force. Transmitters would crank the power up, blowing out all other radios in the area.

This was the original spread spectrum - signals were spread out all over the radio dial. This was unlicensed - no government authority engaged in frequency coordination and licensing.

The result was that radio stations caused interference with each other - only one radio in an area could transmit at a time - and more powerful stations would wipe out weaker stations. As more radio companies, amateurs, and governments took to the air, the cacophony grew worse.

The Titanic disaster demonstrated this reality in many ways. The passengers of the Titanic might have been saved by the California, a 6000 ton ship 20 miles away. However, just before the Titanic’s demise, the California radio man had tried to use his radio to send the daily messages that had been piling up. But when he tried to transmit, he caused interference to the Titanic radio operator, who rebuffed him saying "Shut up, I'm busy with Cape Race." The California radio operator, at the end of a 16 hour shift, gave up, turned off his radio, and went off-duty – putting the California in the position of being unable to hear the Titanic’s distress call several hours later.

The situation had to change. The golden age of radio innovation had led to - a babel of radio interference – incompatibilities between radio services – a land grab for radio frequencies – and inadequate standards for the use of radios on ships. While initially the task of radio coordination fell on the US Navy, eventually this task would fall upon on an independent civilian agency. In 1927, Congress passed the Federal Radio Act – and established the Federal Radio Commission. Seven years later, the responsibilities of the Federal Radio Commission would be assimilated by the new Federal Communications Commission. The mission of these agencies was to prevent interference between stations by awarding licenses to radio operators, designating who has permission to operate, and on what frequencies.

Then, for several decades, very little of interest happened. In 1939, Germany invaded Poland and in 1941, the United States was formally brought into World War II with the Japanese attack on Pearl Harbor. It was in the midst of World War II that unlicensed radio had its origin. The idea came from an unlikely source: a movie star.

Hedy Lamarr was once described as “the most beautiful woman in film.” Ms. Lamarr knew first hand the danger of the Nazis and their ability to intercept allied communications. Her first husband was Friedrich Mandl, and arms dealer and Nazi sympathizer. At dinners, Ms. Lamarr would hear about the Nazi’s ability to intercept allied communications and know where US and British forces were.

After Lamarr fled to the United States, she met George Antheil. Together, they attempted to devise a way of beating Nazi jamming of allied radio controlled torpedoes. Their idea was frequency hopping radio which would elude jamming frequencies. As Antheil was a musical composer, the mechanism for determining which frequencies to use greatly resembled a paper player piano roll. In 1942, Lamarr and Antheil received a patent for their Secret Communication System – which they gave to the US Navy in order to help fight the war effort.

The objective of frequency hopping is simple: avoid interference. With traditional radio use, the transmitting and receiving radios are tuned to one specific frequency. If the enemy knows what that frequency is, the enemy can also transmit on that frequency, causing interference, and effectively jamming the communication. That was the problem Lamarr and Antheil sought to overcome.

Frequency hopping breaks the transmission into pieces – and transmits those pieces over a series of different frequencies. Instead of giving the enemy jammers one target to hit, frequency hopping uses several different targets that keep moving, and turning on and off – making it very difficult for the enemy to know what frequencies will be used. It also makes it very difficult for the enemy to intercept the message. For it to work, the transmitting radio and the receiving radios must know which frequencies and in what order, otherwise the message will be nothing more than gibberish. Lamarr and Antheil’s solution was a roll of paper with holes punched in it, like a player piano roll – both radios would be controlled by the same pattern of holes on the paper.

After Hedy Lamarr’s patent, little was heard about frequency hopping. Frequency hopping was a part of military history – and as such was classified. Military history suggests that frequency hopping communications was used during the 1962 Cuban Missile Crisis. In addition, during the 1972 Mid East War, an “unexpected” amount of interference from jamming was encountered – leading the Department of Defense to have renewed interest in frequency hopping. At about this point, spread spectrum technology become more visible to the public through a series of publications.

A flurry of research and development work was initiated by private companies. They sought to develop radios that took advantage of spread spectrum’s advantages, including its ability to solve interference problems. These companies faced a problem, however. This type of radio service was not authorized pursuant to FCC rules. Therefore, in 1979, Del Norte Technology filed the first of what would be multiple petitions before the FCC. This led to a 1985 FCC order changing its Part 15 rules and, for the first time, authorizing unlicensed spread spectrum service.

This was a dramatic paradigm shift for the FCC which had for decades used licenses in order to demarcated who could use what frequencies. With the promise that spread spectrum would prevent harmful interference to other authorized users, the FCC could embark on an unlicensed experiment with the goal of stimulating innovation.

Although Part 15 radios operate without licenses, they do have Rules of the Road – both for the equipment, and for the operators. Part 15 equipment must be authorized by the FCC as complying with Part 15 rules. In particular, Part 15 equipment is generally limited to small power outputs – which generally means that it has a short transmission range. Part 15 equipment cannot cause interference to other radio – and they must accept any interference.

And those who operate part 15 radios have acquired no right to do so. There is no First Come First Serve. The first radio in to be transmitting in an area doesn’t own that frequency in that area. Instead, the frequency is – as Prof. Yochai Benkler called it – a commons: a place where all may come – where no one can exclude anyone else – and where no one has a superior right to anyone else’s use.

If you think about it – this is an important concept for those legal squabbles about teenagers - sitting in a coffee house parking lot,- stealing WiFi so that they can play World of War – or the priests sitting on park benches outside a library in Nantucket checking email. One problem –since no one owns Part 15 spectrum so it cannot be stolen – but this is a subject for a different blog post.

Part 15 unlicensed radio service was a wild success. In 1988, the IEEE established a committee to work on something called 802.11 standards. This would be a agreed upon set of rules for how something works. That something would be WiFi radio communications. What the committee was doing was hammering out the agreed upon protocol for how WiFi radios communicated with each other. A year later, the work was completed, the 802.11b standard was ratified and the WiFi Alliance was formed. The next year, the 802.11a standard was ratified.

Before long, Wifi would be embedded into essentially every laptop sold. Wifi started appearing in printers, cameras, music players, and weird alarm clock things. The number of applications the FCC received for approval of new Part 15 equipment exploded. Equipment using Wifi – just one of the Part 15 protocols – became all but ubiquitous.

Hedy Lamarr’s interference beating invention had come to fruition. Instead of using licenses to solve interference, technology, specifically spread spectrum could solve interference. Without licenses, barriers to innovation were lowered and the geeks came marching in with lots of new toys.


Photos: Federal Radio Commission, Wikipedia, Public Domain; Marconi Library of Congress, Public Domain; Titanic, NOAA, Public Domain; Lamarr, Wikipedia, Public Domain

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