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Wednesday, March 10, 2010

Spread Spectrum Communications

I teach a course in Data Communications (aka Network Standards and Protocols). I enjoy providing a little history when the course gets to the unit covering Spread Spectrum (SS) technology, which has evolved today into Wi-Fi (IEEE 802.11).

Spread Spectrum communications uses wide band, noise-like signals. It's been a favorite technology for the military, since SS signals are hard to detect, hard to intercept, hard to jam, and hard to demodulate.

Students love their Wi-Fi, and look a little puzzled when I explain how that technology was invented by a famous movie actress and an avant-garde composer.

Yeap, that's right.

The story is amazing. If you made it into a movie, nobody would believe it.

Austrian-born actress Hedy Lamarr (born Hedwig Eva Maria Kiesler) and composer George Antheil are universally credited for discovering and patenting this communications technology.

Hedy Lamarr (1914 - 2000), is better known for the many movies she made at MGM Studios in Hollywood. Lamarr was born to Jewish parents in Vienna, and studied ballet and piano at an early age. She later worked with Max Reinhardt in Berlin, who called her the "most beautiful woman in Europe." Later Lamarr would end up marrying a controlling and wealthy Vienna arms manufacturer who was 13 years her senior. He'd lock her up in the residence, known has"Castle Schwarzenau." Lamarr objected to her husbands' support of Hitler's war machine, but both Hitler and Mussolini were frequent guests at their lavish parties in the castle. It is said that Lamaar dressed as one of her maids and fled to Paris. In 1933 Lamarr created a scandal when she appeared nude for an extended period in the movie "Ecstasy."

George Antheil (1900 - 1959) is know primarily as a daring modernist composer who's music shocked audiences on both sides of the Atlantic. His most famous piece Ballet Mécanique was originally conceived in the 1920s for 16 synchronized player pianos, two grand pianos, electronic bells, xylophones, bass drums, a siren and three airplane propellers. It's often performed today in a scaled down version for percussion, four pianos, and a recording of an airplane motor.

Well-known in both America and in Europe as being an "ultra-modern pianist/composer," Antheil influenced many avant-garde composers, including Edgard Varèse and John Cage. He held wide interests such as publishing articles and books on female endocrinology, and in his spare time wrote a mystery novel (blogs didn't exist yet).

It was Antheil's interest in female endocrinology that brought him and Lamarr together. Antheil had a theory about how men could tell the availability of women based on the glandular effects of their appearance. He consulted with Lamarr on this, and the result of this research was published in his book, "The Glandbook for the Questing Male."

Their research broadened, and after much joint discussion they devised a secret communication system that is now regarded as the predecessor of the today's Spread Specturm "frequency hopping" technology used in communications systems all around the world. Antheil had already applied this technique to control the 88 keys of player pianos in his strange musical compositions.

Lamarr and Antheil submitted their idea to the US Patent office in June of 1941 and were granted a Patent (US Patent # 2,292,387). One of the figures for the patent is show below.

It was clear that they believed their technique could be applied to radio-guided torpedoes and aid the war effort. The US Military took notice, but in 1942 it did not possess the technology to implement Spread Spectrum-based control systems to guide their torpedoes. However, in 1962 during the US blockade of Cuba during the infamous "Cuban Missile Crisis." Lamarr and Antheil's technology was deployed and proven to work (although their Patent had long expired).

Here is a very short YouTube clip about Hedy Lamarr. (Feel free to explore the others posted on YouTube)....

And here is the beginning of George Antheil's Ballet Mécanique in a recent performance by the New Jersey Percussion Ensemble (Peter Jarvis conducting)...