| Visible Light Communication(VLC)uses white Light Emitting Diode(LED)as the light source,which has the advantages of low energy consumption,rich spectrum resources,and good confidentiality,etc.It is widely accepted as an effective supplement for indoor wireless communication.Due to the limited modulation bandwidth of white LED sources,which limits the increase of the transmission capacity of indoor VLC systems,the introduction of Multiple Input Multiple Output(MIMO)technology can be a good solution.In practical indoor MIMO VLC environment,the interference and the correlation between different channels are the main factors affecting its communication quality.Some key technologies such as channel correlation and inter-channel interference have been thoroughly studied in this thesis via heoretical analysis and experimental simulation methods.Firstly,this thesis briefly introduced the development and research status of indoor MIMO VLC system,and describes the model and related characteristics of indoor VLC systems.Then the key technologies in MIMO are discussed along with the related analysis of characteristics in indoor MIMO VLC systems,and the influencing factors or general solutions to the communication quality,respectively.Aiming at the problem of inter-channel interference and inter-channel correlation,this thesis proposes an optimization method of indoor MIMO VLC system based on the selection of the transmitters.The singular value decomposition of the channel matrix is used to determine the actual effective transmitters in the proposed method.Considering both the system capacity and the bit error rate performance of the receivers,the corresponding power will be allocated on the transmitters with the best performance.Theoretical analysis and experimental simulations show that compared with the traditional singular value precoding algorithm,the system capacity of the algorithm can be increased by up to 80%.The Bit Error Ratio(BER)also can be reduced to the system requirements no more than 15 d B.Aiming on the optimization of the receivers mainly involved with the Space Division Multiplexing(SMP),this thesis proposes a method for optimizing the receiving positions of an indoor MIMO VLC system based on spatial modulation(SM).By optimizing the particle swarm optimization(PSO)algorithm,the system modeling and experimental simulation were performed to obtain the best receiving positions of the indoor receivers for the room with different shapes in the case of spatial modulation,and the convergence speed of the algorithm is accelerated. |
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