Research On Key Techniques Based On MIMO For The Future Wideband Communication Systems

The MIMO systems offer a new dimension of freedom,which makes higher data rate transmission and higher reliability possible.Therefore,MIMO techniques draw tremendous attention and are taken as one of the key technologies for future commu-nication systems.To optimize the freedom,it is necessary to identify the gains one can obtain from MIMO links.Holding such objective in mind,this thesis will focus on MIMO and its relative topics.This thesis attempts to be self-contained.As a resuits, it covers a wide range of material from MIMO channels,space time coding up to multi-user multi-stream transmission.The mentioned techniques are well analyzed and possible solutions resolving existed problems are provided based on the theoretical analysis.The results and conclusions obtained in this thesis can be partial theoretical and technical bases for the future wireless communication systems.The major contributions of this thesis are as the following:·The development of One-Ring based wideband frequency selective fading channel model.The space time frequency correlation functions of this model are fully analyzed and compared with those of the reference model.Finally,the correctness and usability are proved by a practical example.·The low complex decoding algorithm which is specially proposed for Quasi-Orthogonal space time block codes based on array processing.The performance of the proposed algorithm is investigated in the case of perfect and imperfect channel state information.·Based on the proposed channel model,impact of antenna geometric parameters on the performance of MIMO downlink transmission is investigated.We conclude that enlarging the antenna spacings at the transmitter can bring more diversity gain compared with doing that at the receiver.In such a system,we also modified the decoding method of space time block codes(STBC),which makes it possible for STBC to be employed in fast fading channels. ·Establishment of a multi-user MIMO multi-streams transmission link.Covariante based precoding design concept is adopted by using a user based joint equalizer at the user equipment.·Finally,considering the channel vector of different streams of a user may have the same covariance matrices thus leading to bad system performance,two novel algorithms are proposed to help on this situation.One is based the modified covariance matrices,the other is based on the modified pilot beamforming vectors chosen according to secondary common pilot channel(SCPICH).The numerical results proved the usefulness of them.