Asynchronous WCDMA Signal User Number Blind Estimation And Signal Reconnaissance

Wideband code division multiple access(WCDMA)is the most widely used third generation mobile communication technology in the world.The signal power spectral density of WCDMA is very low,and it is usually overwhelmed by noise,so it has good confidentiality,anti-interception and anti-interference ability.It is widely used in military communications,civil communications and commercial communications.WCDMA enables multiple users to work simultaneously in the same frequency band by using codeword correlation to distinguish different traffic channels.In communication countermeasures,estimating the number of users,distinguishing and identifying scrambling sequence and source information of different users in WCDMA signal are very important for signal monitoring and recognition.The WCDMA signal includes a plurality of pseudo-random(PN)sequences,and the scrambling code is a truncated Gold sequence,which has a long period and a complicated structure.Therefore,it is difficult to estimate the number of users and pseudo-codes in the asynchronous WCDMA signal in non-cooperative communication.Based on the above background,the user number,the estimation of scrambling code and the blind decoding in WCDMA signals is studied in this paper under the circumstances of multi-user and unknown carrier frequencies.Firstly the current method of direct sequence spread spectrum(DSSS)signals is introduced,and the WCDMA uplink dedicated physical channel is analyzed,involving PN sequence and its production method,long scrambling code and the generation of upstream signal.Based on this,the generation of WCDMA uplink signals and mathematical model of asynchronous WCDMA signals are introduced.Aiming at the problem that the estimation method of DS signal user number is few and does not apply to the WCDMA signal structure,a method for estimating the number of users of asynchronous WCDMA uplink signals is proposed.Then,to solve the problem in blind reconnaissance of asynchronous WCDMA signals,a scrambling code estimation and blind decoding algorithm for asynchronous WCDMA upstream links under single channel is proposed.The WCDMA signal can be equivalent to a virtual multi-user DS-CDMA signal,and its structure is relatively complicated.The researches for estimating the number of its users is difficult and few.Correctly estimating the number of users in the WCDMA signal is the basis for effective blind decoding,so the research on the estimation of the number of users is of great significance.In this paper,an asynchronous WCDMA uplink user number estimation algorithm based on carrier modulation hybrid matrix model is proposed.The algorithm firstly mathematically models the asynchronous WCDMA uplink signal,and according to the frame repeatability of WCDMA signals,sampling each frame signal at equal intervals by the period of spread spectrum code,then dimension reduction of long PN code WCDMA signal is modeled as a hybrid matrix model of short PN code carrier modulation.The frame is equally spaced and sampled,and the long PN code WCDMA signal.Then,the relationship between the number of signal eigenvalues and the number of users of the asynchronous WCDMA signal covariance matrix is derived.Finally,the decision condition is set to determine the number of signal eigenvalues in the signal covariance matrix,and then the number of users in the signal is obtained.Aiming at the WCDMA uplink scrambling code estimation and blind decoding problem,a multi-user superimposed carrier modulation asynchronous WCDMA signal scrambling algorithm blind estimation algorithm is proposed,based on blind source separation,phase-locked loop technology and m-sequence generator polynomial.The algorithm firstly samples the frames according to the frame repeatability of the WCDMA signal by the spreading code period,and then separates the WCDMA signal by the ICA algorithm to obtain the carrier-modulated scrambling code sequence,and then the scrambling sequence of the period length of a spread spectrum code can be estimated by de-frequency offset of the phase-locked loop.Estimation of the signal delay,partial scrambling code error correction and complete scrambling code are completed,according to the scrambling code generation principle in WCDMA protocol and the generating polynomial of M sequence.Then,the original signal is descrambled by using the estimated scrambling code,and the descrambled signal is despread by using the correlation characteristic of the spreading code,and last the despread signal is accumulated according to the spreading code period to estimate the source information.Theoretical analysis and simulation results of Unicom WCDMA mobile phone signal show that the proposed method can accurately estimate the scrambling code and source information in multi-user asynchronous WCDMA signals.Finally,the paper summarizes the content of the full text,and expounds the shortcomings of the algorithm and the future research direction.