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Frequency Hopping

The main advantages of the system are that though it can transmit a large amount of information over a wide spectrum of frequencies, anyone evesdropping on a specific frequency will hear only a short blip of information. This spreading of the system over such a range of frequencies, also makes it impossible to jam the signal. Jamming a signal in this instance means that only a small amount of data will be lost. Additionally, because the signal is thinly spread across such a great range of frequencies, this means that many more users are able to access the same range of frequencies. Because the devices are hopping so quickly from one frequency to the other, it is statistically unlikely that many data "collisions" will occur. As with evesdropping or jamming, even if a collision were to occur, it would likely not greatly effect the data transfer, as only a small amount would be lost. Frequency hopping is sometimes abbreviated as: FHSS (Frequency Hopping Spread Spectrum.)

The Inventors Assistance League (http://www.inventions.org/) explains frequency hopping as follows:

Frequency hopping, which today is used extensively in military communications, means broadcasting a signal (which might carry commands for directing a torpedo) over a seemingly random series of radio frequencies, switching from frequency to frequency at split-second intervals. A receiver hopping between frequencies in sync with the transmitter can pick up the message, while any eavesdroppers will only hear random blips. An attempt to jam such a signal—jamming was and remains a drawback to radio control—will knock out only bits of it, often leaving enough untouched to do no harm at all.

Lamarr and Antheil never profitted from this invention as it didn't gain interest from the military until the 1960's, when it was used in military communications to resist opposing forces trying to jam military frequencies. According to a Wireless Systems Lecture Dr.Fitzek of the FUTURE Group, during the 1950's and 1960's, wireless systems began to be used increasingly in public communications systems, beginning with lower frequencies at first (156MHz - 174MHz) , and gradually increasing the upper frequency range. A brief explanation of frequencies and frequency regulations follows.

(View the Frequency Hopping patent by searching for Patent Number 2,292,387 at the USPTO - United States Patent and Trademark Office. The entire Patent has also been made into a PDF on this GTONS site and is available here: LamarrPatent-2292387.pdf (812kb PDF download).

Much more wireless information is available on the Internet. The FUTURE Group site is one particularily good place to start if more in-depth information on wireless history is desired. Wireless technology, like other contemporary technologies, is in a continual state of flux, with new developments often changing the face of the industry. As such, it should be noted that frequency hopping as explained here is just one common method for transferring data via wireless technology - other methods are also used, and can also be read about on the FUTURE group site and other wireless information sites.

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