MIMO-OFDM Visible Light Communication System Design

Compared with the traditional radio communication,visible light communication has many advantages such as ample spectrum resources,no harm of electromagnetic radiation,high signal to noise ratio,so it becomes one of the hot spots in the field of wireless communications.OFDM technology has the advantages of simple balance,high spectral efficiency and effective resistance to frequency selective fading,and combined with visible light communication technology,it can achieve higher rate of data transmission.However,the limited modulation bandwidth of the LED becomes one of the bottlenecks in the SISO system to further increase the rate.At the same time,a number of LED arrays are usually arranged to meet the lighting requirements,which is also possible for the application of MIMO technology.This paper mainly studies the design of SISO-OFDM and MIMO-OFDM systems.The main contents of this paper are as follows:Firstly,parameter selection of ADO-OFDM is studied,and the receiver scheme of ADO-OFDM is improved.Based on the study of ACO-OFDM frequency domain diversity,noise reduction receiver improvement scheme and ADO-OFDM system principle,the following research is doing:On the one hand,the parameters of the ADO-OFDM system,including the constellation combination of the two signals,the power allocation and the DC bias size of the DCO-OFDM signal are analyzed theoretically and empirically.On the other hand,the improvement schemes of ACO-OFDM receiver are applied to ADO-OFDM system to improve the receiver scheme of ADO-OFDM by improving the bit error rate performance of the system.Secondly,for the MIMO-ADO-OFDM system,the OSIC algorithm is improved.The ADO-OFDM dual carrier signal is composed of ACO-OFDM cutting noise and DCO-OFDM signal superposition,so the OSIC algorithm is improved to making it suitable for MIMO-ADO-OFDM systems,based on the introduction of the MIMO-ADO-OFDM system model and the traditional OSIC algorithm.The simulation results show that the OSIC algorithm significantly reduces the bit error rate of the system compared with the linear detection algorithm in the case of large channel correlation.Thirdly,the pre-coding scheme in the context of PAM modulation is expanded to O-OFDM system for high-speed data transmission.When the transmitter knows the channel state information,the transmitter can be pre-coded to further improve the bit error rate performance of the system.Based on the characteristics of ACO-OFDM and DCO-OFDM and the analysis of the principle of pre-coding scheme with single carrier modulation,the above-mentioned pre-coding scheme is expanded to realize high-rate transmission and improve bit error rate performance of optical MIMO-OFDM Systems.The simulation results show that the pre-coding scheme for O-OFDM modulation can improve the bit error rate of the system compared with the equal power distribution of the transmitter.Fourthly,for the I-MIMO system,the signal recognition and merging scheme is proposed,and the EGC merging algorithm is improved.To begin with,the signal recognition scheme is presented on the basis of the visible light I-MIMO channel model,and then the SC,EGC,MRC and other merging algorithms are introduced.The EGC algorithm is improved based on the channel characteristics of the visible light I-MIMO by selecting the communication quality of the better subset of the channel to merge to further improve the performance of the algorithm.The simulation results show that the signal merging scheme proposed in this paper can distinguish the imaging of different LED lamps well;among the above-mentioned merging algorithms,the performance of MRC algorithm is the best and the SC algorithm is the worst.Moreover,compared with the traditional EGC algorithm,the improved EGC algorithm significantly reduces the system error rate.