The blind periodic estimation of the pseudo noise sequence in multi-rate DS/CDMA transmissions

In this paper, we study on the blind periodic estimation of the pseudo-noise (PN) sequence in variable-spreading-length (VSL) multi-rate direct-sequence code division multiple access (DS/CDMA) systems. The reprocessing of the power spectrum method which is used to estimate the period of general direct-sequence spread spectrum signals is extended to solve the periodic estimation of the PN sequence in multi-rate DS/CDMA signals. We sample the received signals and estimate its power spectrum, then looks upon the estimated power spectrum as input signals and computes its power spectrum again. The derivation can prove that the power spectrum reprocessing of the multi-rate DS/CDMA signals will arise varied amplitude sharp pulse with intervals equaling to the period of these different rates users´ PN sequence, accordingly, we can acquire all the periods of the different rates users´ PN sequence. The computer simulation shows that the method is effective in low SNR.