Study On Smart Antenna Technology In Software Wireless Communication

The smart antenna system can form spatial oriented beam by means of digital signal processing, orienting the main beam in the direction of arrival of desired signal and putting nulis in the direction of interferences,and then lead to increase in both the SIR of the desired signal and the system capacity ,which has been one the present focuses in array signal processing field.the smart antenna based on software radio with open construction and configurable system can exploit the information of interest contained in the signal more effectively by processing signal samples both in time and space.In this dissertation,the smart antenna based on software tadio technology is studied.A series of theoretical models together with the detailed algorithms for smart antenna in wireless communication are proposed,including the algorithms used to dliminate multi-path interference,to reduce multiple access interference and to estimate the parameter of the uplink signals . The main xontributions of the dissertation are as follows:The smart antenna construction based on the software radio technology is studied , the realization schemes of the smart antennas for both soft-capacity enhancement and hard-capacity enhancement are given and the idea of introducing algorithm pool in smart antenna systems based on software radio is suggested. Then the smart antenna systems in software base station is studied,the RF and system configuration of the software base station introduced and the experimental scheme of the smart antenna in software base stations given.With the discussion about influences of multi-path effects on wireless channels,the multi-path channel model based on partial scattering theories is proposed and the mathematical expressions of this model in each special electromagnetic environment are analyzed.At last,the transmission property of partial scattering model is studied and the frequency-selective characteristics of wireless channels relative to the code length of signals and time delay of delayed signals given.We also proposed a spatial-temporal combined method,which first estimate the direction vector of the desired signals and then adjust the array weights by constrained LMS algorithm to reduce multiple access interference.In this method SMG-algorithm is used for higher computer speed.The capacity of CDMAsystem with the smart antenna is analyzed and a computer simulation given by a real system as an example.