A radio technique that continuously alters its transmission
pattern either by constantly changing carrier frequencies or by
constantly changing the data pattern.| Direct Sequence Spread
Spectrum (DSSS) DSSS multiplies the data bits by a very fast
pseudo-random bit pattern (PN sequence) that "spreads" the data
into a large coded stream that takes the full bandwidth of the
channel. DSSS is the basis for CDMA cellphones and 802.11 Wi-Fi
wireless transmission. For a technical example of DSSS
technology, see CDMA. Frequency Hopping Spread Spectrum (FHSS)
FHSS continuously changes the center frequency of a conventional
carrier several times per second according to a pseudo-random
set of channels, while chirp spread spectrum changes the carrier
frequency. Because a fixed frequency is not used, illegal
monitoring of spread spectrum signals is extremely difficult, if
not downright impossible depending on the particular method.
FHSS is the transmission technology in Bluetooth. See 802.11,
Wi-Fi and Bluetooth. Invented