Study On Blind Estimation Of The Pseudo Noise Sequence For LC-DSSS And Multi-Antenna LC-DS-CDMA Signals

Direct Sequence Spread Spectrum(DSSS),as an important modulation technology,is widely used in electronic countermeasures,aerospace,communication monitoring,and other military or civilian communications because of its advantages such as strong anti-interference ability,security performance,and low probability of interception.Direct Sequence Code Division Multiple Access(DS-CDMA)uses multiple pseudo code sequences to modulate the information codes of multiple users,so that each user's spectrum is broadened.It is widely used in GPS positioning systems.Wireless LAN and other fields.Among them,the Long Code-Direct Sequence Spread Spectrum(LC-DSSS)signal and the Long Code-Direct Sequence Code Division Multiple Access(LC-DSCDMA)signal use a period of pseudo noise sequence to modulate multiple information symbols,and the periodicity of the pseudo noise sequence is seriously damaged.What's more,in the non-cooperative communication,it is necessary to know the pseudo noise sequence used for spreading to realize the blind despreading of the intercepted signal.Therefore,the blind estimation of the pseudo noise sequence for LC-DSSS and LC-DSCDMA signals has become a research hotspot in DSSS communication system parameter estimation.In this thesis,blind estimation of the pseudo noise sequence for LC-DSSS and LCDS-CDMA signals is studied.The main work includes the following aspects:Therefore,a blind estimation method of NPLC-DSSS signal pseudo-code sequence based on piecewise eigenvalue decomposition and Messi algorithm is studied.1.Aiming at the problem of blind estimation of Non-Periodical LC-DSSS(NPLCDSSS)signal pseudo-code sequence,a blind estimation method of the pseudo noise sequence is studied based on piecewise eigenvalue decomposition and massey algorithm.Firstly,the received signal is divided into several non-overlapping segments according to the spread spectrum modulation ratio in the pseudo-codes period.Secondly,segmented eigenvalue decomposition is used to estimate the pseudo noise sequence fragments and stitch these fragments.Finally,the massey algorithm is used to obtain the pseudo noise sequence generator polynomial for eliminating the phase blur generated during the stitching by sliding the search window.And the m sequence and Gold sequence is correctly estimated in the end.2.For the problem that the pseudo noise sequence for Periodic Long Code-direct sequence spread spectrum(PLC-DSSS)signal with residual carrier after down-conversion is difficult to estimate,a blind estimation method of the pseudo noise sequence is studied based on eigenvalue decomposition and digital phase locked loop(DPLL).Firstly,the PLC-DSSS signal with residual carrier is equivalently modeled as a virtual multi-user short code-direct sequence spread spectrum(SC-DSSS)signal model.The pseudo noise sequence with residual carrier can be estimated by the matrix eigenvalue decomposition and fuzzy unitary matrix methods.Secondly,the DPLL is used to track and estimate the frequency and phase of the residual carrier,and remove the carrier frequency in the end.Finally,the pseudo noise sequence can be estimated by removing its segmentation phase ambiguity with the condition of the specific constraint.3.For the problem that the pseudo noise sequence for Long Code-Direct Sequence Code Division Multiple Access(LC-DS-CDMA)signal is difficult to estimate,a blind estimation method of the pseudo noise sequence is studied based on tensor decomposition and polynomial library search by using multi-antenna.Firstly,the received signals are modeled as a third-order tensor model and the tensor is divided into multiple sub-tensors according to the spreading gain.Secondly,the pseudo noise code fragment factor matrixs and the receiver gain factor matrixs are obtained from the subtensors by CP(Canonical Polyadic)decomposition which using the Alternating Least Squares Projection(ALSP)algorithm,and then the pseudo noise sequence of each user is obtained by selecting pseudo noise code fragment combination sequence according to the cross-correlation of the receiver gain factor matrixs.Finally,the polynomial library search method is applied to identify the generator polynomial of the pseudo noise sequence in order to further improve the accuracy of the pseudo noise sequence blind estimation.