Research On The Key Technologies Of Multiuser Diversity In Multiple Antenna System

Various high-speed multimedia services, such as video and data services, have becoming significant demands for the next generation of wireless communication systems, as the development of wireless multimedia communication network and the growing number of mobile users. The improvement of spectral efficiency and data transmission rate is one of the key challenges which must be solved for the B3G/4G systems. Multiple-input multiple-output (MIMO) technology has been proposed and studied by more and more researchers as its outstanding performance in increasing the capacity of system obviously without additional power and bandwidth, and improving the spectral efficiency as well as the link reliability. Meanwhile, multiuser diversity, which is the inherent in multi-user wireless communication systems, could improve the performance of the system efficiently if used properly. Therefore, the proper use and choosing of multiuser diversity gain in MIMO systems is momentous in practical. This paper is supported by the research of radio transmission technologies for the next generation of cellular mobile communication system (FuTURE), one of the National High Technology Research and Development Programs of China with Grant (No. 2003AA12331005), and the WiMAX Test Network System of Wuhan National Laboratory for Optoelectronics (WNLO), focusing on the researches of the key technologies of multiuser diversity in multiple antenna systems and the related performances of different multiuser diversity schemes.The downlink of MIMO system is the key point in this paper due to the asymmetry of broadband multimedia services, where downlink channel is always the bottleneck. Firstly, a brief description of the related theories of MIMO communication system is presented, emphasizing on the concepts and the tradeoff of spatial diversity and spatial multiplexing, and then two different multiuser diversity schemes in MISO system from different aspects. For the multiuser diversity with transmit antenna selection scheme, after reviewing the results of other researches, a Maximum Ratio Transmitting Multiuser Diversity (MRT-MD) technique is suggested, reaching the tradeoff between system capacity and transmission performance. For the multiuser diversity with beamforming scheme, a Multi-beam selection with Orthogonal Random Beamforming (ORBF) algorithm, a partial Feedback Beamforming (FBF) algorithm and a partial Feedback Orthogonal Beamforming (FOBF) algorithm are proposed, using spatial multiplexing gain properly and improving the transmission of system. Simulations compare our algorithms with existing algorithms, and analyze the effect of the system performances. The results have provided crucial references for the selecting multiuser diversity schemes in multiuser communication systems. At last, summaries and suggestions are presented for further studies.