Direct sequence spread spectrum
The accompanying visual shows the emissions stack of three traditional unspread radio signals and the signal that results after the spreading of the three signals. The spread signal is a low-power signal that creates little self interference and for all practical purposes looks like noise. Some will refer to direct sequence spread spectrum (DSSS) as noise modulation. The mathematics of DSSS show that each user has its own unique contribution to the spread signal and, since the uniqueness is created by orthogonal spreading codes, each user's signal can be retrieved from the noise.