Research Of Smart Antenna DBF Algorithms For DS-CDMA Systems

The demands for the number of mobile users and the wireless multimedia communications service have been increased rapidly; higher system capacities and better the quality of service are required for the mobile user. The smart antenna is one of the advanced techniques which could be implemented in the mobile telecommunications systems to achieve high system capacity. This thesis places emphasis on one of the key techniques of smart antenna - adaptive digital beam forming (DBF) algorithm and its applications in the DS-CDMA mobile telecommunications systems.The first step is reviewing conventional methods of digital beam forming, including WINER method, Steepest-Descent method, LMS, RLS etc. Then , recent digital beam forming methods in the DS-CDMA mobile telecommunications systems are studied, including the algorithm based on least-squares despread respread Multi-Target array (LS-DRMTA), least-squares Despread Respread Multi-Target Constant Modulus Array (LS-DRMTCMA) , Pilot bit LMS-DRMTA algorithm etc. Finally, results of computer simulation are given, theoretic analysis is also provided in this thesis.A new DBF algorithm (LMS-DRMTCMA) and a new user signal direction of arrival (DOA) estimation algorithms (Max value Searched DOA estimation algorithm) are proposed in this thesis.These beam forming algorithm have be used the signal characteristics, such as constant modulus, PN spread codes, or spread gain. The new algorithms are proposed in this thesis all base on the characteristics of constant modulus and PN spread codes.Theoretic analysis also shows the new algorithms are characterized by low computation and easy real time implementation. The number of activist users is not limited by the number of antenna elements in the new algorithms.The simulation experiments show that the new DBF algorithm can perform at much lower BER than the other DBF algorithm and can work in very low SNR situation.The simulation experiments show the new DOA estimation algorithm can provide exact and stabilization DOA estimation.