qr48 07 04 25

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Information about qr48 07 04 25

Published on January 31, 2008

Author: Davidino

Source: authorstream.com

Spread Spectrum:  Spread Spectrum Technology is forever Shannon-Hartley, once again:  Shannon-Hartley, once again C = B lg (1+S/N) where C = channel capacity B = bandwidth S = signal power N = noise power What happens to C if B = 0? What happens to C if S = 0? What happens to C if S = N? Noise is Inevitable:  Noise is Inevitable C = B lg (1+S/N): What happens if N = 0? Infinite channel capacity!!! Noise is like friction: it’s always going to be with us Or sin! Wonderful things would happen without it E.g. moving any amount of information in fixed time Spread Spectrum Tradeoff: Lower Power <==> Larger Bandwidth:  Spread Spectrum Tradeoff: Lower Power <==> Larger Bandwidth C = B lg (1+S/N) http://sss-mag.com/primer.html#ds How to Use Bandwidth?:  How to Use Bandwidth? Simple idea: Treat multiple frequencies as multiple Shannon channels, like radio stations. More bandwidth <=> More channels <=> More information flow 103.3MHz 96.9 MHz freq1 freq2 Spread Spectrum I: Frequency Division Multiple Access (FDMA):  Spread Spectrum I: Frequency Division Multiple Access (FDMA) Several communications in the same bandwidth range, each in a separate “channel” If phones are spatially far enough apart, signals fade and frequencies can be re-used Old analog cell phones used this technology Handoffs awkward when moving from cell to adjacent cell if same frequency channel is in use Security Issue:  Security Issue Big risk: Eavesdropper can just tune in the right frequency and listen Spread Spectrum II: Code Division Multiple Access (CDMA):  Spread Spectrum II: Code Division Multiple Access (CDMA) Have all communications share the same bandwidth but give data from each a unique key so that it can be disentangled from the others Divide the bandwidth into channels but have each conversation jump rapidly between frequencies according to a unique sequence known only to the tower and cell phone This is Frequency Hopping Spread Spectrum (FH/SS) Smoother handoffs since key can be maintained across cells Spread Spectrum for Security:  Spread Spectrum for Security Instead of using just one frequency, hop rapidly from one frequency to another The source and the destination must agree on the values and sequencing of frequencies The sequence is an encryption key Must appear random and unpredictable to an eavesdropper: pseudo-noise Eavesdropper on any one frequency hears only “noise” 1 2 3 4 5 6 4,2,5,6,1,3,4,5,2,… 4,2,5,6,1,3,4,5,2,… The Strange History of Frequency Hopping:  The Strange History of Frequency Hopping World War II: Torpedoes could be guided by radio control, but the radio transmission could also be jammed by the enemy, confusing the torpedo Torpedoes caused enormous losses to both Allied and Axis fleets Hedy Lamarr:  Hedy Lamarr Hedy Lamarr:  Hedy Lamarr ~1914: Born Hedwig Eva Maria Kiesler in Vienna First woman to appear nude in a feature film, Ecstasy (1933), when she was age 19 After release of film, married wealthy industrialist Fritz Mandl, who tried to buy up and burn all the prints Hedy Lamarr:  Hedy Lamarr Hostess for Mandl’s parties in Vienna, where they entertained his business friends “Any girl can be glamorous. All she has to do is stand still and look stupid.” Louis Mayer and America:  Louis Mayer and America Kiesler became increasingly hostile both to the Nazis and to her husband Mandl In 1937 she hired a maid who looked like her, then drugged the maid and escaped to Paris in the maid’s uniform She met movie mogul Louis Mayer, who gave her a movie contract and the name Hedy Lamarr Divorced Mandl on grounds of desertion Emigrated to America and settled in Hollywood George Antheil:  George Antheil Born 1900 in New Jersey, of Prussian parents Studied music in Philadelphia, became concert pianist in Berlin and Paris Avant-garde composer of “mechanistic” pieces such as Airplane Sonata and Death of Machines Ballet Mécanique was scored for 16 player pianos, xylophone, and percussion; one production had electric bells, airplane propellers, and siren Ezra Pound: “Antheil is supremely sensitive to the existence of music in time-space” Antheil in the US:  Antheil in the US By 1933, Antheil’s music was out of fashion and he was broke and moved to California Invented the “See Note” system of musical notation, read down the page with each column representing one note, like a player piano roll - also a commercial failure Man Ray photo Antheil and Endocrinology:  Antheil and Endocrinology 1936, Esquire: Glandbook for the Questing Male and The Glandbook for Practical Use Slide20:  The Glandbook in Practical Use (Esquire, June 1936) Lamarr and Antheil :  Lamarr and Antheil In 1940 Lamarr arranges to meet Antheil in Hollywood She knows about Antheil’s applied endocrinology and wants to know how to enlarge her nnnnnnn The next night they talk again and Lamarr says she is thinking of quitting MGM and offering her services to the National Inventor’s Council “They could just have me around, and ask me questions” What Hedy Lamarr Knew:  What Hedy Lamarr Knew Lamarr learned a lot while standing around and looking stupid at parties Fritz Mandl was a munitions maker and his regular dinner guests included: The Invention:  The Invention Lamarr understands major problems in weapons design She has some ideas about unjammable torpedo guidance systems She explains to Antheil the idea of spread spectrum frequency hopping to prevent interception and jamming She does not know how to control the sequencing of frequencies Antheil: “With a Player Piano Roll!”:  Antheil: “With a Player Piano Roll!” The Fate of the Invention:  The Fate of the Invention Out of patriotism, Lamarr and Antheil give the patent to the Navy and never receive any royalties She helps the war effort by selling kisses at $50,000 each, raising $7M in War Bonds in one night The Navy classifies but does not implement the invention, reluctant to put player pianos into torpedoes In the 1950s electronic control became possible, and frequency hopping became the basis for all secret military communications First heavily used for secret communications in the Cuban Missile Crisis in 1962 The Curious End of Hedy Lamarr:  The Curious End of Hedy Lamarr Antheil dies in 1959, never seeing the fruit of his labors Lamarr runs through six husbands, several fortunes, and two shoplifting arrests She develops a habit of suing almost anyone who mentions her name in public, but wins few of the lawsuits In 1997, with spread spectrum technology now being used to secure millions of cell phone conversations, Lamarr, 84, is awarded the Electronic Frontier Foundation Pioneers Award “It’s About Time” Lamarr on Telephone with her Son at the EFF Award Ceremony:  Lamarr on Telephone with her Son at the EFF Award Ceremony The Broadcast Spectrum is Not a Limited Resource!:  The Broadcast Spectrum is Not a Limited Resource! Spread spectrum passed from military to commercial use Spread spectrum makes it possible to have essentially unlimited numbers of cell phone calls Spread spectrum makes possible multiple low power, spatially limited, encrypted digital signals If radio stations can broadcast and rebroadcast at low power over limited areas using spread spectrum, there can be essentially unlimited numbers of stations The legal justification for FCC control of content has been rendered irrelevant by technological advances that started with Lamarr and Antheil! Slide31:  The most beautiful woman in the world - Louis Mayer Coda:  Coda In 1996, Corel Corporation, producer of drawing software Corel Draw8, awards a prize to the draftsman of this image of Lamarr as the best picture drawn using their program Thinking Lamarr is dead, Corel puts the image on its box and startup screen Lamarr sues Corel for $15M, eventually settles, and lives out her last years in comfort 1999: “Films have a certain place in a certain time period. Technology is forever.” Hedy Lamarr died January 19, 2000, at the age of 86

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