Blind Estimation of Long and Short PN Code in LSC-DSSS Signals

The LSC-DSSS signal can be regarded as special long code DSSS signal, taking the short spreading code and the long scrambling code together as the composite code. Firstly, the composite code can be estimated blindly by using the eigenvector decomposition and the unitary matrix method of eliminating fuzzy relations. And then the type of short code can be identified by using properties of the triple correlation function(TCF) of m sequence. Finally, according to the results of identification, the long and short PN codes are blindly estimated by using TCF method or delayed TCF method. Simulations show that the bit error rate of composite code sequence is below 1% when the signal-to-noise ratio(SNR) is greater than -7.5dB. The correct rate of the primitive polynomial of long and short code can reach to 90% when the TCF method is used and the SNR is above -6dB. The bit error rate of long and short code sequence can be reduced to 1% when the delayed TCF method is used and the SNR is above -4dB.