Reasearch On Performance Of Precoded Multi-user MIMO Indoor Visible Light Communication System

Visible light communication(VLC)can be used to surf the Internet when it emits light,which has the advantages of abundant spectrum resources and wide coverage.Aiming at the multi-user interference and block diagonalization(BD)algorithm existing in the multi-user multi-input multiple-output(MIMO)VLC system,the problem of unbalanced sub-channel strength caused by multi-user interference can be solved,this thesis explores the performance of a multi-user MIMO VLC with substream selected BD algorithm.The specific research contents are as follows:1.In view of the high complexity of the BD algorithm and after the singular value decomposition(SVD)of the equivalent channel matrix,the singular value corresponding to each substream channel is obviously different,the substream selected BD algorithm is proposed,compared and analyzed the complexity and sum capacity of the system of the two algorithms.2.We established a multi-user MIMO VLC system model based on the substream selected BD algorithm,and compared and analyzed the relationship between the system's single LED transmission power and bit error rate performance of this system;by changing the field of view of the receiver,the user's MIMO channel matrix similarity is reduced,the system's signal-to-noise ratio and bit error rate performance is analyzed,and the effectiveness of the scheme is verified;an indoor walking model is established,and the signal-to-noise ratio performance of the mobile terminal is simulated and analyzed,and the optimal receiving position of indoor users is determined.3.The control variable method is introduced to set up the two different indoor models of MIMO channel correlation,by changing the position parameters of LED and photodetectors,and combining with the substream selected BD algorithm multi-user MIMO VLC system,analyzed the correlation of different channel matrix condition number,the system capacity and bit error rate performance,in order to get a reasonable indoor lighting layout and reduce multi-user MIMO VLC channel correlation.The research results show that:(1)Substream selected BD technology has the advantages of low calculation complexity and maintain the capacity of the original BD technology system.(2)Compared with the multi-user MIMO VLC system of BD technology,the substream selected BD technology reduces the LED transmission power requirements and decreases the impact of the receiving field of view on the bit error rate of the receiver;according to the relationship between terminal mobility and signal to noise ratio of system,determined the indoor best reception position and the signal to noise ratio of 34.7%is higher than 40dB.(3)With the continuous enhancement of spatial channels correlation,the bit error rate performance of decreasing,and the substream selected BD algorithm can bring gain of more than 4dB compared with BD algorithm system.