Research Of Adaptive Algorithm For Smart Antenna In TD-SCDMA System

Smart antenna,which is widely researched in the field of mobile communication,has been successfully applied in TD-SCDMA communication system,and will play an important role in next generation mobile communication. Adaptive beamforming algorithm is the key technique of smart antenna.It could adaptively steer the array directional pattern to form the narrow main beam with high gain in the direction of the users' signal while deeply null-steering the interference signals.It is an effective way to realize the optimal receiving of the interesting signal.The thesis begins with the explanation of the fundamentals of smart antenna. Both the non-blind adaptive algorithms(LMS and RLS) and the blind adaptive algorithms(SG-CMA and LS-CMA) applied in smart antenna system are explored. Secondly,vector channel model is analyzed,and the GBSBEM model under wireless multipath propagation channel for TD-SCDMA system is illustrated.This thesis focuses on the research and analysis of constant modulus algorithm and de-spread re-spread technology that used in the blind adaptive beamforming algorithm for TD-SCDMA systems Based on the analysis of least squares de-spread re-spread multi-target algorithm(LS-DRMTA) and least-squares de-spread re-spread multi-target constant modulus algorithm(LS-DRMTCMA), two improved algorithms(Block RLS-DRMTCMA and Block AP-DRMTCMA) are proposed,and the detailed derivation is expatiated.Block RLS-DRMTCMA makes use of the information carried by previous data,it can achieve better performance in time-invariable channel.Block AP-DRMTCMA makes use of de-spread re-spread technology and constant modulus algorithm to generate a referenced signal,then creats the weight vector by the block affine projection algorithm(Block APA),it can achieve excellent performance in both static and dynamic channel conditions. Simulation results show that the improved algorithms get excellent performance of the accuracy of beamforming,the output signal to noise ratio and bit error rates in multi-user multi-path channel,and the dynamic tracking performance in dynamic channel environment is also improved.Beamforming technology based on the improved algorithm can effectively reduce or even eliminate multi-user interference and multipath interference in TD-SCDMA system,and effectively improve the system BER performance and expand system capacity.Consequently,the reaserch of this thesis dose not only have theoretical significance,but also greater practical value.