| It is expected that a Multiple-Input Multiple-Output (MIMO) system can provide a hightransmission rate and satisfy the high-speed transmission requirement of various application. As thecore technology of the mobile communication in future, MIMO has been paid much attention onacademia and industry. It has been applied to the third generation mobile communication systemstandard. In the research of the third generation partnership and long-term Evolution advanced(3GPP) standard technology, uplink and downlink MIMO technology, especially the multi-userMIMO technology and multi-cell of MIMO technology are more extensively researched and paidattention. In fact, it has been shown that, from an information theoretic point of view, the maximalachievable rate region or capacity region of a multiuser MIMO downlink system can offersubstantial spatial diversity gain as well as significant multi-user diversity gain under assumptionthat the perfect channel state information (CSI) is available both at the transmitter and the receivers.In Multi-antenna systems, without taking up the extra spectrum resource and time resource,multi-antenna technology can achieve higher speeds transmission and better communication qualitywith its unique spatial degrees of freedom. We study the multi-antenna downlink MIMO systemfrom the perspective of higher speeds transmission and better communication quality in the futuremobile communication.In this thesis, we mainly introduce the communication between users, mainly studies themulti-user downlink MIMO system transmission technology and some methods to eliminate thechannel interference. A new method to deal with the interference, named as affine projectiondecoder, will be proposed.Firstly, we introduce the channel model of multi-user MIMO system and the theory ofinformation capacity, multi-user precoding and space-time code technique, and so on. Precodingtechnique is heavily based on instant CSI at the transmitter, when the condition is removed,precoding techniques can not be applied.Secondly, we introduce the basics concepts of affine projections. We will use the Alamoutischeme which is extensively adopted in IEEE Standards, to illustrate our proposed affine projectiondecoders. It should be notice that our decoders differ from the methods based on the orthogonalprojection, where the wanted signal is damaged when the interference is canceled.Finally, technique of affine projection will be applied in to space-time codes, and we give the performance. This method can be extended to general situation. |
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