History of Spread Spectrum
In March 1903 an inventor called Nikola Tesla’s U.S patent was granted for his “Method of Signalling”, within the patent the system is described to allow radio communications “without any danger of the signals or messages being disturbed, intercepted, interfered with in any way”. The system described in the patent would allow the transmitter and receiver, once synchronised, to hop between channels in order to avoid interference. This would be done by changing the carrier frequency. Although it does not state the words “frequency hopping” it is a very similar device.
The first Frequency-Hopper Spread Spectrum was patented by a famous Hollywood actress, Hedy Lamarr, in August 1942. Together with her co-inventor George Antheil, they designed a system for radio control of torpedoes. Although this was not the first time this type of system had been developed, the concept of frequency hopping was. Using frequency hopping it would be possible to prevent the proposed target from blocking the controller’s signal.
This concept was not used by the military for radio-controlled torpedoes, however, was eventually used by the military in the 1960’s to allow secure communications.
Overview of Spread Spectrum
Spread Spectrum techniques are used within telecommunication and radio communications to spread the generated signal with a specific bandwidth, within the frequency domain. This will produce a signal with a wider bandwidth. There are many reasons for using this technique some of which are: to create secure communications, prevent detection, and to add resistance to interference.
There are various different types of Spread Spectrum:
• Frequency-Hopping Spread Spectrum (FHSS)
• Direct-Sequence Spread Spectrum (DSSS)
• Time-Hopping Spread Spectrum (THSS)
• Chirp Spread Spectrum (CSS)
In order to control and determine the spreading patter that each of these methods uses within the specific bandwidth of the signal, pseudorandom...