Key Techniques Of Wcdma Same Frequency Interference Suppression

With the rapid development of mobile services, GSM system is evolving towardsthird generation (3G), especially the WCDMA as the representative of the3G system,and wil coexist with3G system and LTE for a long time.In order to save spectrum resources and reduce the cost of investment, mobilecommunications sector proposed the idea of same-frequency transmission, such asWCDMA and GSM transmit in the same frequence bands.However, when WCDMA and GSM transmitted in the same frequency band, the twosystems interfere with each other. Although in theory WCDMA signals, using spreadspectrum technology, can suppress the interference equivalent to the spreading gain, inthe practical application subject to the fact that different interferences have differentstatistical properties, relying on the interference suppression capacity of itself is notenough. We must take necessary interference suppression receiver to reduce BER andimprove the interference suppression performance.Thus, accordding to GSM signal in WCDMA band with the same-frequencytransmission, this paper proposes the study of interference suppression of WCDMA andGSM, and mainly focuses on the resarch of the overlay GSM interference suppressionin WCDMA signals.First, an enhanced code-aided interference suppression method based onRLS(Recursive Least Square) is proposed by code-aided interference suppression,which put the thought of MUD into digital NBI suppression with DSSS system. Theoriginal code-aided interference suppression method needs a64×64matrix inversionand four matrix multipplications, meanwhile enhanced code-aided interferencesuppression method only needs a8×8matrix inversion and a matrix multiplication.So, the enhanced code-aided interference suppression method this paper proposed cansimplify the receiving calculation and apply to WCDMA physical layer; by measuringand comparing the BER and BLER, complete demonstration on MATLAB.Second, based on interference detection with SVD, we integrate the interferencedetection and interference suppression. By detecting interference, we can simplify theWCDMA physical layer and improve the efficiency of information transmission.The research in this paper explores the problem of same-frequence transmissionabout WCDMA and GSM, which extends the existing researches and has sometheoretical and practical values. The research results can achieve that WCDMA signal iscompatible with GSM in the same frequence band so as to solve the spectrumcontradiction in the process of transition from GSM to WCDMA, and significantlyreduce the operator’s spectrum costs and operational risk.