Friday, 21 December 2012

Frequency-hopping spread-spectrum invention

                           Frequency-Hopping Spread Spectrum (FHSS)

Frequency-Hopping Spread-Spectrum (FHSS) is a spread spectrum modulation scheme that uses a narrowband carrier that changes frequency in a pattern known to both transmitter and receiver. Properly synchronized, they maintain a single logical channel. To an unintended receiver, FHSS appears as short-duration impulse noise. More simply, the data is broken down into packets and transmitted to the receiver of other devices over numerous “hop frequencies” (79 total) in a pseudo random pattern. Only transmitters and receivers that are synchronized on the same hop frequency pattern will have access to the transmitted data. The transmitter switches hop frequencies 1,600 times per second to assure a high degree of data security

Hedy Lamarr  & George Antheil are often credited and holds original patent for Frequency-Hopping Spread Spectrum (FHSS)


Hedy Lamarr (9th November 1913 – 19th January 2000) was an Austrian-American actress , Inventor and mathematician, celebrated for her great beauty, who was a major contract star of MGM's "Golden Age." When she worked with Max Reinhardt in Berlin, he called her the "most beautiful woman in Europe" due to her "strikingly dark exotic looks," a sentiment widely shared by her audiences and critics. She gained fame after starring in Gustav Machatý's Ecstasy, a film which featured close-ups of her character during orgasm in one scene, as well as full frontal nude shots of her in another scene, both very unusual for the socially conservative period in which the bulk of her career took place.

Mathematically talented, Lamarr also co-invented—with composer George Antheil—an early technique for spread spectrum communications and frequency hopping, necessary for wireless communication from the pre-computer age to the present day.

Hers & George Antheil system of radio selective switching as it is called now as Frequncy hopping is used in CDMA mobile Telephony systems.

Code division multiple access (CDMA) is a channel access method used by various radio communication technologies. It should not be confused with the mobile phone standards called cdmaOne, CDMA2000 (the 3G evolution of cdmaOne) and WCDMA (the 3G standard used by GSM carriers), which are often referred to as simply CDMA, and use CDMA as an underlying channel access method.

One of the concepts in data communication is the idea of allowing several transmitters to send information simultaneously over a single communication channel. This allows several users to share a band of frequencies (see bandwidth). This concept is called multiple access. CDMA employs spread-spectrum technology and a special coding scheme (where each transmitter is assigned a code) to allow multiple users to be multiplexed over the same physical channel. By contrast, time division multiple access (TDMA) divides access by time, while frequency-division multiple access (FDMA) divides it by frequency. CDMA is a form of spread-spectrum signalling, since the modulated coded signal has a much higher data bandwidth than the data being communicated.

Avant garde composer George Antheil, a son of German immigrants and neighbor of Lamarr, had experimented with automated control of musical instruments, including his music for Ballet Mécanique, originally written for Fernand Léger's 1924 abstract film. This score involved multiple player pianos playing simultaneously. 


Antheil wrote a nationally syndicated newspaper relationship advice column, as well as regular columns in magazines such as Esquire and Coronet. He considered himself an expert on female endocrinology, and wrote a series of articles about how to determine the availability of women based on glandular effects on their appearance, with titles such as "The Glandbook for the Questing Male".

Antheil's interest in this area brought him into contact with the actress Hedy Lamarr. Lamarr had fled her Austrian munitions-making husband, and coming to the US had become fiercely pro-American. As a result of a chance conversation, they conceived and patented a frequency-hopping torpedo guidance system. Lamarr contributed the knowledge of torpedo control gained from her husband and Antheil a method of controlling the spread spectrum sequences using a player-piano mechanism similar to those used in Ballet Mécanique. Despite the initial enthusiasm of the U.S. Navy, the importance of the Antheil-Lamarr discovery was only acknowledged in the 1990s.The creation of the device designed by Lamarr and Antheil was not implemented until 1962, when it was used by the U.S. military in Cuba. Later it served as a basis for modern communication technology, such as CDMA transmission protocol for cellular telephones.

During World War II, he participated in the "Hollywood Anti-Nazi League for the Defence of American Democracy" with Oscar Hammerstein and others, putting on exhibits of artworks banned in Nazi Germany such as those by Käthe Kollwitz. He also published a book of war predictions, entitled The Shape of the War to Come.

Lamarr took her idea to Antheil and together, Antheil and Lamarr submitted the idea of a secret communication system in June 1941. On August 11, 1942, US Patent 2292387 was granted to Antheil and "Hedy Kiesler Markey," Lamarr's married name at the time. This early version of frequency hopping used a piano roll to change between 88 frequencies and was intended to make radio-guided torpedoes harder for enemies to detect or jam. Although a presentation of the technique was soon made to the U.S. Navy, it met with opposition and was not adopted.

The idea was not implemented in the USA until 1962, when it was used by U.S. military ships during a blockade of Cuba after the patent had expired. Perhaps owing to this lag in development, the patent was little-known until 1997, when the Electronic Frontier Foundation gave Lamarr an award for this contribution. It is reported that, in 1998, Ottawa wireless technology developer Wi-LAN, Inc. "acquired a 49 percent claim to the patent from Lamarr for an undisclosed amount of stock" (Eliza Schmidkunz, Inside GNSS), although expired patents have no economic value. Antheil had died in 1959.

Lamarr's and Antheil's frequency-hopping idea serves as a basis for modern spread-spectrum communication technology, such as Bluetooth, COFDM used in Wi-Fi network connections, and CDMA used in some cordless and wireless telephones. Blackwell, Martin, and Vernam's 1920 patent Secrecy Communication System (1598673) seems to lay the communications groundwork for Kiesler and Antheil's patent, which employed the techniques in the autonomous control of torpedoes.

Lamarr wanted to join the National Inventors Council, but was reportedly told by NIC member Charles F. Kettering and others that she could better help the war effort by using her celebrity status to sell War Bonds.

Lamarr died in Casselberry, Florida, on January 19, 2000, aged 86, from natural causes. Her son Anthony Loder took her ashes to Austria and spread them in the Vienna Woods, in accordance with her last wishes while Antheil died of a heart attack in the New York City borough of Manhattan. His legacy included two accomplished students, Henry Brant and Benjamin Lees. He is buried in Riverview Cemetery, in Trenton, New Jersey.

Key Words:  Frequency-hopping  George Antheil Hedy Lamarr  Hedy Kiesler Markey  Code division multiple access (CDMA) Frequency-hopping spread-spectrum invention

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