Detection of multiple users of direct sequence spread spectrum signals by cyclic spectral analysis

The spectral correlation of direct sequence spread spectrum (DSSS) signals in the bi-frequency plane is exploited for detection of users in a fading multipath channel. Unlike conventional code division multiple access (CDMA), the length of code for each user is different, while the processing gain and the carrier frequency are the same. This gives rise to a unique set of cycle frequencies for each user. Assuming low cross-correlation between the codes, these sets of cycle frequencies can be used to identify the presence of user(s) in a highly noisy environment