Hedy Lamarr and the Secret History of Spread-Spectrum Technology
Posted on Fri, Apr 15, 2011 @ 07:16 AM
The recent death of Elizabeth Taylor caused a spate of tributes and reminiscences about her movies, husbands, divorces, scandals and more. I didn’t see any articles about her contributions to technology, but that isn’t surprising. We don’t typically equate celebrities with major technological advances.
Imagine a press conference held by Cisco to announce a technology breakthrough so important that it will influence technology for the next sixty years or more. Now, imagine that they bring the people responsible for this new technology out on stage – Snookie and The Situation. It sounds implausible, but there is a historical precedent for just such an announcement…
The Most Beautiful Technology Innovator in the World
Radio stations are assigned a frequency by the government. Each station pays for its own frequency, and no one else is allowed to use it. Because the number of frequencies is very limited, prices tend to be high — most of us couldn’t afford to buy our own frequency. That’s where the work of Hedy Lamarr comes in.
In the late 1930s and through the ‘40s, movie star Hedy Lamarr was advertised as “The Most Beautiful Woman in the World.” There were those who would have argued for Taylor, but no one disputed that Lamarr’s looks were stunning.
There were some dramatic differences between the two women: Elizabeth Taylor became the most famous movie star in the world. Hedy Lamarr had a largely undistinguished film career and is mainly remembered for being lampooned by Harvey Korman, who played “Headley Lamarr” in Blazing Saddles.
There is at least one other difference: Hedy Lamarr changed the course of telecommunications history.
Lamarr’s Contributions to Telecommunications
Lamarr was born in Austria but immigrated to the United States, in part, to escape Nazi rule. Her first husband was a munitions supplier to the German government. She saw the destruction they were creating and fled to divorce him, but through their relationship she learned about military technology.
Her ex-husband’s firm had been supplying the Nazis with torpedoes and focusing on how to control them. Some torpedoes were aimed at targets ten miles away or more, so putting a wire on them wasn’t practical. A better approach, they learned, was radio frequency (RF) waves. However, these had problems as well because an enemy could intercept the broadcast and use the same RF frequency to jam the torpedo.
In America and remarried, Lamarr, with help from avant garde composer George Antheil, came up with a solution inspired by Antheil’s experiments with automatically controlled musical instruments: send messages between a transmitter and a receiver, but keep changing frequencies among 88 she designated, using random patterns. Because radio waves move so quickly, it would be almost impossible for anyone to intercept even a single communication.
The remaining problem was how to keep the transmitter and receiver in synch. Lamarr solved this be creating paper cylinders, similar to those on player pianos, that had identical perforations in a pattern to delineate the frequency path. Rolls with the same pattern were installed in both the transmitter and receiver, and when started at the same time they would remain in synch until the torpedo reached its target.
The Navy, unfortunately, saw too many failure points in Lamarr’s design, and her patented Secret Communications System never played a role in the fight against Hitler. The idea, however, didn’t go away.
Mass Adoption of Spread-Spectrum Technology
In the 1950s, Sylvania engineers started using the Secret Communications System, now renamed spread-spectrum with digital media rather than paper rolls. Presidents Kennedy and Johnson used it for their secure communications.
For the next twenty years, spread-spectrum remained a military-communications technology, but by the mid-80s it had been declassified and was now known as frequency hopping because the transmission jumps from frequency to frequency. As commercial developers began to incorporate spread-spectrum technology, it evolved to become an integral element of CDMA (Code Division Multiple Access), the dominant standard for cellphones in North America.
It’s a critical part of the standard because as people buy more cellphones there is a great need for efficiency in using radio waves. Spread-spectrum allows us to simultaneously communicate over the same bands of spectrum without appreciable interference. It also provides encryption possibilities for enhanced security.
So, there will be books and documentaries celebrating the life and accomplishments of Elizabeth Taylor, and Hedy Lamarr won’t be much more than a footnote in some of these books. But this increasingly obscure beauty made a significant technological contribution that continues to resonate in our lives today.
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Bill Cannon is Vice President of Business Development at MCPc, and an IT industry veteran with expertise in networking and telecommunications technology. Connect with Bill on LinkedIn.
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Image credit: Marxchivist