The Research Of Interference Suppression In Td-scdma System

The title selection is mainly originated from Tianjin science and technology innovation special funds project.The name of the project is "the research and development, demonstration and application of new generation mobile communication network coverage key technology". The paper researches the interference in TD-SCDMA system and mutual interference between TD-SCDMA and WCDMA systems and further provides guidance to the implementation of the project.Since the TD-SCDMA license is granted, various cities open of TD-SCDMA continually. With the development and construction of TD-SCDMA system wireless network, TD wireless network optimization become increasingly important.The interference problem is one of the key issues in wireless network optimization. It includes the interference between TD-SCDMA and other 3G systems, the interference between TD-SCDMA and the second-generation mobile communication (2G), the interference in TD-SCDMA system. The existence of these interferences seriously lead to dropped calls, system capacity loss, reduced coverage area and other issues. It is necessary to study the problem of interference co-existence which is complied with the characteristics of China's mobile communication system.The research works of the paper are as follows:First, the paper mostly researches the interference in TD-SCDMA system, smart antenna technology is an effective measure to suppress the interference in TD-SCDMA system. The intelligence of smart antennas are mainly embodied in the antenna array weighting vector can be based on the user's needs and the changes of antenna propagation environment and adaptively adjust. That it can make main beam directs at the direction of desired user, the side beams directing at the direction of interference, thus suppressing or canceling the interfering signals. And this adaptive process is controlled by the adaptive algorithm, the adaptive algorithm is the core of smart antenna technology. The size of computation and convergence of the algorithm and other factors directly affect the overall system performance and the complexity to realize the circuit. Therefore, seeking less computation and simple structure to achieve adaptive algorithm has great significance.Second, we research the smart antenna beam-forming algorithms, including:least mean square algorithm, normalized LMS algorithm, recursive least squares algorithm, sampled matrix invert algorithm. Then in the MATLAB platform, simulate adaptive algorithm using software, verify the result that the smart antenna can suppress interference signal. Then analysis and compare of the simulation results, obtained the advantages and disadvantages of each algorithm. Finally based FPGA in the ISE platform provided by Xilinx the thesis achieve TD-SCDMA system smart antenna beam-forming network, the beam-forming module can be used in smart antenna development system.The design enhance the system flexibility,it is a simple realization method. Lastly, the thesis researches the interference between TD-SCDMA system and WCDMA systems which used by the two operators, China Mobile and China Unicom, then use deterministic method and obtain the isolation needed between the two systems, and then guide implementation of the project. The results provide a certain reference value for different systems of network optimization.