Estimation of DS/CDMA Code Length in multipath Channel

This paper deals with the problem of blind multiuser detection in variable processing gain direct-sequence code division multipleaccess(VPGDS-CDMA). Direct-Sequence Spread Spectrum (DSSS)signals are well-known for their low probability of interception. Furthermore, they are usually transmitted below the noise level. Here, the method is based on the fluctuations of autocorrelation estimators. By using the variable spreading length technique, we show an increase of the periodical fluctuations and consequently an average relationship between their peak amplitudes and sequence lengths. A theoretical analysis illustrate that detection possible, even with a very low signal-to-noise ratio (SNR) at the detector input.