spread spectrum - Computer Definition
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.