| Recent years, multi-antenna technology has got great attention because of the advantage of enhancing system capacity and spectral efficiencies. It can also improve system reliability. Research domain has also changed from frequence, time, and code to spatial domain. Multi-antenna technology has the ability to cope with the spatial character of space-time channel.Smart antenna technology has become the key point in the third generation communication especially in TD-SCDMA because of the spatial distinguish ability. Beamforming from smart antenna, which increasing desire signal and suppressing interference, can achieve spatial divided multiple accessing (SDMA). With the developting of smart antenna, it begins entering the wildband wireless communication area.Multiple input and multiple output (MIMO) technology has get great development. The research about MIMO has increased from single user to multiuser MIMO system. The application environment has changed from the indoor rich scattering uncorrelated channel to outdoor correlated channel. Because of the advantage in the spectral efficiencies and transmitting ability, it has become the key point in LTE and 4G.But the channel correlation under space-time wireless environment will bring influence to the system capacity and reliability when MIMO technology has applied from indoor to outdoor. In the same time, the distance demand between antenna elements will bring the difficulty to engineering application. So MIMO technology is developing from opened loop to self adapted closed loop system relying on the feedback of channel information. How to depress the influence of channel correlation and how to decrease the feedback load and operation complication are the key points for the application of MIMO technology.This dissertation starts from the research of space time channel. The correlation coefficient is derived under statistical channel model in LTE. It gives the influence measurement of different spatial coefficients to channel correlation. The relationship of angle spread and the correlation between different multipaths is analysed for the next chapters'research. Supposing the independence between multipaths, two kind of beamforming spatial multiplex schemes for single user are proposed in the dissertation. The first scheme can get the multiplex and diversity plus together through self adaptation transmitting beamfroming and switch receiving beamforming. When the multipaths are not enough for spatial multiplex and spatial diversity at same time, the second secheme is proposed that combines the beamforming multiplex and dual polarized diversity to leave more multipaths for the spatial multiplex. Through the associated optimization between transmitting and receiving, the system capacity can get increase under strong correlated channel. The feedback load and operation complication can get decrease together.Beamforming is combined into multiple users systems. The ability to depress interference between users is enhanced. Comparing with other multiple users MIMO systems such as zeroforcing, the scheme proposed in this dissertation does not need to feedback full CSI information because the spatial characters of multiplex users are completely used.The capacity and reliability of multiple users system are affected by the correlation between multiplex users which include the spatial location, angle spread and multipath DOA. Also considering the number of active users usually large than the multiplex serving users, multiuser diversity is combined. An interference parameter is used for multiuser scheduling. Because of the multiuser diversity, the sum capacity can get improved.Considering the frame structure of LTE, a downlink slot divided Multiuser scheduling scheme is proposed at last. The relationship between average system capacity and the number of slots is analysed. It can give a reference for the configuration of active users and slots.
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