Frequency hopping spread spectrum is a method of transmitting radio signals by rapidly changing the carrier frequency among many distinct frequencies occupying a large spectral band. The changes are controlled by a code known to both transmitter and receiver. The data signal is modulated with a narrow-band carrier signal that "hops" in a random but predictable sequence form frequency to frequency as a function of time over a wide band of frequencies. FHSS is used to avoid interference, and to prevent eavesdropping, and to enable code-division multiple access (CDMA) communications. It was invented and patented in 1942 by the actress Hedy Lamarr and paintist George Antheill. Principle of frequency hopping spread spectrum FHSS has a very simple and interesting principle : a wide frequency band is divided into multiple channels and communications are hopping sequentially from one channel to another in a sequence and a rate agreed to advance between the trans...