Application Of Digital Beamforming Technology In MIMO Systems

Multiple-input multiple-output(MIMO)technology sets multiple antennas at both the transmitting and receiving ends,while digital beamforming(DBF)technology is a beamforming technology which transmits antennas with the same data is regarded as one antenna.All of them are vital technologies that promote the development of modern mobile communications.This thesis proposes an innovative idea that a linear or area array is equivalent to a single antenna in MIMO system.Combined with digital beamforming technology,the system can effectively reduce interference and improve signal quality.At the same time,it can reduce channel error rate as well as increase the system capacity.This thesis mainly discusses the adaptive digital beamforming algorithms applied to MIMO systems.The main work has done for the thesis as follows:Firstly,the thesis introduces the principles of MIMO technology and some related theoretical knowledge including varied channel models and different system models.Also,some commonly used criteria in adaptive digital beamforming technology are introduced clearly.There are some comparison and analytic are also done on these mentioned criteria.Then,a variety of different adaptive digital beamforming algorithms are discussed.There are some typical blind adaptive algorithms and non-blind adaptive algorithms that have theoretical analysis and comparative simulation.All of the analysis is aiming at determining which algorithm is the relatively better adaptive digital beamforming algorithm for MIMO systems.The simulation results show that low sidelobe minimum variance distortion-free(MVDR)algorithm has a better suppress interference effection and better convergence characteristics compared with the least mean square(LMS)algorithm.So,it can be learned that MVDR algorithm is a relatively superior adaptive digital beamforming algorithm.At last,based on the above results,the thesis puts up with a improved algorithm named MVDR algorithm based on oblique projection with low sidelobe interference.And the algorithm is also applied to MIMO systems.After doing the corresponding system simulations,the results shows that the algorithm can effectively suppress interference and obtain a robust beam pattern with good beamforming effect when it is applied in the MIMO system.The combination of digital beamforming technology and MIMO technology has distinctive characteristics,it can definitely meet the requirements of mobile communications and it will shine inthe future development of mobile communications.