Multi-user Mimo Distributed Beam Forming Algorithm Research

Along with the development of wireless communication technology, the demand of spectral efficiency is increasing which promotes the research and application of new wireless transmission technologies. As a transmission technology, Beam-forming can effectively suppress the interference and enhance the capacity or BER performance of wireless communication system. Recently, beam-forming has been adopted by the3GPP standard and also included in IEEE802.16e.In fact, beam-forming can be seen as a spatial filtering technology based on multi-antenna, in which transmitter and receiver matrix are designed to suppress the interference and improve the power gain of the desired signal. The design of beam-forming in multi-user system not only needs to consider the main lobe direction of the desired signal at the desired user, but also need to avoid the desired signal to cause interference to other users as much as possible. So the design of beam-forning needs to comprehensively consider the following three factors which are interrelated and mutual restraint, and they are transmitter matrix, reciver matrix and the power allocation among different user and different data streams for the same user.In multi-user systems, the design of beam-forming often requires the interaction of large number of precision CSI between difference transmitters, but it is actually difficult to achieve in practical application. Secondly, when we use the multiplex gain of the MIMO system to transmit several data streams, the interference between data streams is tend to be ignored, and of couse, this will reduce the performance. Finally, Minimizing the total transmit power to improve the the power efficiency in ensuring the QoS of each user is also a worthwhile study.In this paper, we expand the following research for the problem in the design of beam-forming for the MIMO system involved above.Chapter1describes the significance of this study, analysises the existing beam-forming algorithms for the multi-user MIMO system, gives the mathematical models of the problems need to be resolved in the design of multi-user MIMO beam-forming.Chapter2proposes an iterative interference alignment algorithm based on space distance, derives the closed form solution of the transmitter and receiver matrix, proves the convergence of the iterative algorithm, analysises the performance and computational complexity of this algorithm, and at last makes the corresponding simulation.Combining with the practical application scenarios, Chapter3gives a distributed beam-forming algorithm based on the TD-LTE standard to increase the capacity of backhaul link in cellular relay network, analysises the transmission performance and the computational complexity and makes the system-level simulation using Wrap-around technology.Chapter4studies the feasibility of single-stream power allocation under the QoS constraints per user, gives the feasibility conditions of single-stream power allocation and the corresponding power allocation scheme, at last, compares the proposed power allocation scheme with the average power allocation scheme.Chapter5concludes this dissertation and discusses the future research work.