FHSS - frequency hopping spread spectrum 


frequency hopping is a spread spectrum technique in which 
the transmitter transmits at varying frequencies for very 
small periods of time say milli or nano sec. these 
frequencies are choosen in random among the frequency band 
available. the reciever and tansmitter both are aware of 
the sequence of the frequencies going to be used.
if some other agent tries to break the system and suppose 
tunes to a particular frequency then he'll be able to get 
that small part of the msg only because from next milli 
sec, the frequency is going to change