Spread spectrum technology is a technique for better utilization of an available frequency band. Instead of transmitting the signals in frequency division multiplex or time division multiplex, they can also be transmitted with code spreading over the radio frequencies.
There are various mobile radio technologies in which the spread spectrum technique is used. For example, in Wideband Code Division Multiple Access(WCDMA) and in 802.11, but also in the GPS system and in the uplink channels ofUMTS.
The spreading code is a spreading sequence that is generated by a special code generator and consists of a high-bit-rate code sequence. For this purpose, the bit sequence to be transmitted is combined with the spreading sequence during spreading. This combination produces the chip sequence.Chips" are the smallest information units within the code sequence; used to distinguish them from bits. The transmission rate is specified in chips per second (c/s). The spreading codes themselves are generated as pseudorandom codes or pseudorandom noise( PRN).