Detection and characterisation of DS/SS signals using higher-order correlation

Conventional linear and nonlinear intercept receivers are ineffective in detecting direct-sequence spread spectrum (DS/SS) signals if the transmissions are designed to be covert and the chip code sequences are unavailable. The detection problems are exacerbated if the users operate within a code-division multiple access (CDMA) environment with dynamic power control. Higher-order moment (HOM) and/or spectral (HOS) processing techniques should be better able to exploit the non-gaussian cyclostationarity of the DS/SS signal structure versus the channel noise. Results are given of a feasibility study into using triple correlation HOM/HOS techniques for DS/SS detection taking into account the discrete polynomial structure of the chip code sequences involved; it is possible under certain conditions to estimate the DS/SS chip code generator(s).