Research On Adaptive Beamforming Algorithm Of Smart Antenna

As a hot topic research of communication fields, smart antenna is now used in wireless communication systems successfully. The technology of Space Division Multiple Access (SDMA) is introduced to smart antenna, so the smart antenna can combine with other multiple access technologies and communication resource expands to space region. As the result of the technology of smart antenna utilized, the capacity of communication system increase remarkably, and limited frequency spectrum resource will be utilized sufficiently.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.Firstly, a survey on current research status of smart antenna and adaptive beamforming algorithm is given, and the adding power rules in beamforming are introduced.Secondly, the simulation and performance analysis of NLMS algorithm and RLS algorithm are given. For RLS algorithm has the disadvantages of large steady-state error, an improved IQR-RLS algorithm based on QR decomposition is proposed. Through defining new data matrix, the improved algorithm solves the coefficient matrix and the right vector of data field in the formal equation, thus, the computational efficiency is increased and the steady-state error is decreased. The results of simulation show the effectiveness of the proposed algorithm.Thirdly, for circular array have the problems of high side-lobe (relative to main-lobe) and the lower depth of nulls, this thesis studies Gram-Schmidt (G-S) beamforming algorithm for circular array. Then, an improved algorithm is proposed which can remove the target signal from the received signal and just leaves the interference to be orthogonalized, so the target signal is prevented to treat as interference. The simulation results prove that the improved G-S algorithm can form deeper nulls and has better performance in adaptive beamforming.Finally, the summary and the prospect on this research are given.