Note: Frequency hopping, direct sequence PN spreading, time scrambling, chirp, and combinations of these techniques are forms of spread spectrum. Ultra Wideband (UWB) is another modulation technique that accomplishes much the same purpose, based on transmitting short duration pulses.
2. A signal structuring technique that employs direct sequence, frequency hopping or a hybrid of these, which can be used for multiple access and/or multiple functions. This technique decreases the potential interference to other receivers while achieving privacy and increasing the immunity of spread spectrum receivers to noise and interference. Spread spectrum generally makes use of a sequential noise-like signal structure to spread the normally narrowband information signal over a relatively wide band of frequencies. The receiver correlates the signals to retrieve the original information signal.
Source: from Federal Standard 1037C and from the NTIA Manual of Regulations and Procedures for Federal Radio Frequency Management and from MIL-STD-188 and from the National Information Systems Security Glossary
See also: open spectrum