Note to readers - I'm having surgery this week and in my absence, I'm featuring some of my favorite articles and columns from my decade of writing about Broadband Wireless Internet Access. This feature article from the short-lived CLEC Magazine was my favorite piece for them. It was little-noticed because the circulation of CLEC Magazine never really took off. The article was wonderfully complemented by a stunning full-page photo of Lamarr at her prime (not the one on the right) - she truly was a beautiful woman.
Hedy Lamarr Article
Special to CLEC Magazine, January, 2000
Approximately 1500 words
- The best picture of Hedy Lamarr at the peak of her beauty that I've seen is at http://wireless.oldcolo.com/course/hedy.jpg.
- The "CB Radio" explanation in the 5th paragraph may be more effective as a sidebar rather than having it in the body of the text - Editor's call on this.
- Although this article was requested at 750-1500 words, it was tough to make the article relevant to the target audience without explaining Lamarr's idea and exactly WHY it's so profound. Again, Editor's call on whether to cut sections, or not.
Spread Spectrum Patent Co-Creator, Hedy Lamarr, died January 18, 2000
Actress Hedy Lamarr died on January 18, 2000. Although her loss was felt by fans of the 1940's movie era, where she was declared at the peak of her career to be "The Most Beautiful Woman In The World", her loss was also felt deeply by wireless techies who considered her one of their own.
Hedy Lamarr co-invented, with composer George Antheil, one of the fundamental technologies in use today in wireless communications. On August 11, 1942, Antheil and Lamarr (under her married name - Hedy Keisler Markey) were awarded U.S. Patent Number 2,292,387 for a "Secret Communications System". The communications technique they described is now known broadly as Frequency Hopping Spread Spectrum Communications. Because of the secrecy demands of World War II, the patent was immediately classified, and remained so for the duration of its 17-year effective lifetime, and beyond. Antheil never received any financial reward for Patent 2,292,387 by the time of his death in 1959, but Hedy finally did in 1998, when Wi-LAN, Inc. acquired a 49 percent claim to Patent 2,292,387 for an undisclosed amount of Wi-LAN stock.
Antheil and Lamarr originally conceived the "Secret Communications System" for use in guiding torpedoes. Lamarr had overhead many technical conversations during her brief marriage to Fritz Mandl, an Austrian industrialist and supplier to wartime Germany. Lamarr had learned that accurate torpedo and missile guidance was a vital wartime issue and that radio control signals for torpedoes were easily jammed. The idea for their system came to them while they were playing the piano together and "communicating", even though the keys they were using changed constantly. They developed the idea to make use of 88 different channels (the same number of keys on a piano). In an inspired bit of practicality, they described not only how to use commonly available player piano mechanisms to provide the required synchronization between transmitter and receiver, but some of the practical issues involved in doing so, such as insuring that the remote and the base units were synchronous. Player piano mechanisms were in wide use, easily manufactured, and relatively inexpensive.
The effect of Antheil and Lamarr's idea would be to rapidly, but synchronously, change frequencies of a particular radio transmitter and receiver pair so that the communication from the transmitter to the receiver would be seem to be uninterrupted. However, another receiver (or someone using a transmitter to intentionally "jam" a communication) that did not know what "frequency changing" pattern was being used, would be unable to receive (or "jam") the entire communication.
Imagine a Private Conversation- On CB Radio?
To explain Antheil and Lamarr's idea in a modern context, imagine having a conversation on a CB radio that you wanted to keep reasonably private. Most channels on CB radio are like a big party line - lots of people talking, and many, many people listening. To implement Antheil and Lamarr's idea with CB radios, only a relatively simple electronic modification is required to make two CB radios automatically change channels (Frequency Hopping) on an agreed-upon schedule (synchronization). For purposes of explanation, let's say change three channels Up every second. The first second of the conversation occurs on channel 1, the second on channel 4, the third on channel 7, etc. Eventually the pattern reaches Channel 39, and the next channel in the pattern is Channel 2. To the party transmitting, and the party receiving, the conversation would sound relatively normal. Anyone casually listening to, say, CB Channel 16 would only hear the one second of conversation that occurred on Channel 16. Anyone attempting to use a typical radio scanner to follow the conversation would be unlikely to hear much more than a few snippets. Anyone who figured out the "3 channels Up per second" pattern would be able to listen in on the conversation. However, the simple "+3 ch/S" pattern was chosen only for ease of explanation - a real "hopping pattern" is much more random-like, say a predetermined pattern of Channel 33, then 9, then 17, then 28, then 1, etc. Also, the channel changes would happen more rapidly than once per second. The practical effect is that the conversation is, for all intents and purposes private, even though it is being transmitted in the very public medium of CB radio.
It appears that the U.S. Government never made use of Patent 2,292,387 as originally proposed, using mechanical means of synchronization. In the early 1960's (after the patent had expired, but was still classified), electronic methods of synchronization were applied to Antheil and Lamarr's ideas, resulting in a practical "Secret Communication System", the successors of which are today's highly-classified LPI (Low Probability of Intercept) military communications systems.
Spread Spectrum Communications became truly practical, useful, and affordable to society as a whole when Digital Signal Processor chips came into widespread use in the 1990's, spurred on by such high-volume uses as modems and cellular telephones.
Why Antheil and Lamarr's Idea Is So Profound
Frequency Hopping Spread Spectrum Communications offers a way for many communications users to share a band of frequencies in an "ad-hoc" manner, without requiring the use of channelization and extensive coordination of frequencies, as is the case with conventional two-way radio used by law enforcement, utility companies, taxicabs, etc. With a randomized hopping pattern, the chance of two transmitters occupying the same frequency at the same moment is low. If this situation does occur - a "collision", hopping patterns are automatically changed.
When Antheil and Lamarr's patent was eventually declassified, the Federal Communications Commission recognized the potential of Spread Spectrum Communications. In 1995, the FCC decided to use this new technology to make unlicensed, high speed wireless data communications available to the computer industry. The FCC chose to first implement Spread Spectrum in areas of the radio frequency (RF) spectrum that had previously been considered useless - the "junk bands", formally known as the Industrial, Scientific, and Medical bands at 902-928 MHz and 2.4 GHz. The ISM bands (also known as "Part 15 bands - the relevant regulations are found in Part 15.247 of the FCC Regulations) are used for non-communications use for microwave ovens, industrial plywood dryers, and medical diathermy (radio-induced heating of tissues). Conventional communications of the time could not operate in the presence of such "interference" as microwave ovens. The "carrot" for the computing industry to rise to the considerable challenge of developing Spread Spectrum Communications in the ISM bands was that a license would not be required to operate equipment based on Spread Spectrum technology.
Because no license is required to operate the equipment, and the technologies are now well understood and economical to manufacture, countless wireless devices, including many wireless Internet access systems, are now being manufactured. Many wireless Internet access systems are now in use overseas and in rural areas of the U.S. to provide Internet access to schools that otherwise could not afford the cost of conventional "wired" Internet access. Many new, if not most computing devices will soon be equipped with a "Bluetooth" chip to enable easy, inexpensive wireless communications between simple devices. Numerous wireless devices based on spread spectrum communications are now in common use in the home.
Hedy Lamarr's ideas fundamentally altered the way in which we are able to communicate. Although conceived to offer a secret method of communications, her system's most lasting legacy is that it evolved to allow thousands, perhaps millions of times more efficient use of radio spectrum, which in turn has allowed human beings to simply communicate better with each other. Only those few of us in the business of supplying communications services to the public could understand some of the satisfaction that Hedy Lamarr must have ultimately felt.
Lamarr Awarded a Special EFF Pioneer Award
On March 12, 1997, Hedy Lamarr and George Antheil (posthumously) were given a special Pioneer Award from the Electronic Frontiers Foundation. The Pioneer Awards were started in 1991 in order to recognize individuals who have made significant and influential contributions to the development of computer-based communications or to the empowerment of individuals in using computers.
For additional reading:
Dave Hughes' Old Colorado City Wireless Field Tests; The First Frequency Hopping Inventor - http://wireless.oldcolo.com/course/hedy.htm
Wi-LAN Inc.'s Hedy Lamarr page - http://www.wi-lan.com/news/hedy.html [link no longer valid]
Press Release announcing the 1997 Special Pioneer Award being given to Hedy Lamarr by the Electronic Frontiers Foundation - http://www.ncafe.com/chris/pat2/pioneer.html
An excellent article describing the background of Antheil and Lamarr's patent is an article - "I guess they just take and forget about a person", by Fleming Meeks, Forbes Magazine, May 14, 1990.
By Steve Stroh
This article is Copyright © 2000, 2007 by Steve Stroh.
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