Research On O-OFDM Symbolic Decomposition MIMO System For Indoor Visible Light Communication

Visible light communication(VLC),as a complementary technology of radio frequency communication and a green communication method,selects visible light spectrum with a high frequency band as the transmission medium.VLC technology solves the problems of spectrum resource shortage and ’ last mile ’ in the RF field.The advantages of VLC and the development needs of the current communication field make it a research hotspot.However,the high peakto-average power ratio(PAPR)of the optical orthogonal frequency division multiplexing(OOFDM)system makes the VLC system face the challenge of nonlinear distortion,which seriously deteriorates the system performance.On the other hand,due to the relatively narrow modulation bandwidth of light emitting diode(LED),the bandwidth utilization and system capacity of VLC system are limited.Therefore,achieving higher data transmission rate,larger system capacity,and effectively suppressing the nonlinear distortion of LED have become important issues that must be solved in the field of wireless communications.Based on this,based on the suppression of LED nonlinear distortion in visible light communication O-OFDM system,this paper combines symbolic decomposition serial transmission(SDST)and multiple-input multiple-output(MIMO)technology to study the problems of LED modulation bandwidth limiting the band utilization and communication rate of indoor VLC,and theoretically derive and briefly analyze the channel capacity boundary of the system.At the same time,adaptive symbolic decomposition(ASDST)technology is introduced to establish an adaptive symbolic decomposition MIMO system.Comparative analysis of performance indicators such as bit error rate(BER)is carried out.The specific research content is as follows:1.Aiming at the problems of greatly reduced communication rate caused by serial transmission in SDST system and poor practicability of single LED lamp.An indoor visible light communication O-OFDM symbol decomposition MIMO system(SDO-OFDM-MIMO)is proposed,and the channel capacity of the system is analyzed.The O-OFDM symbols with large PAPR are decomposed to drive multiple LED lights to realize VLC-MIMO communication.The results show that the SDO-OFDM-MIMO system improves the system information rate on the basis of suppressing the nonlinear distortion of LED,and the BER performance of the system is optimized.The problem of poor system performance caused by nonlinear distortion of LED at the transmitter of the original VLC-MIMO system is improved.In addition,the theoretical derivation and analysis of the channel capacity of the system are carried out.Based on the theoretical basis of ’ entropy power inequality ’ and ’ variational method ’,the upper bound of channel capacity is derived.2.Aiming at the problem of all-zero sign due to fixed number of limits in SDO-OFDMMIMO.The Adaptive O-OFDM Symbolic Decomposition MIMO System for Indoor Visible Light Communication(ASDO-OFDM-MIMO)was proposed.According to the adaptive technology,the all-zero sign in the system is eliminated,and the linear detection algorithm of zero forcing(ZF)and minimum mean square error(MMSE)is used at the receiving end to detect and recover the information sequence.The results show that the ASDO-OFDM-MIMO system improves the traditional iterative signal limiting(ISC)and adaptive iterative signal limiting(AISC)when the simple multiplexed signals at the receiving end are combined and processed,ignoring the channel gain difference problem of multiple optical signals.And compared with SDO-OFDM-MIMO,optical power is saved and system performance is further improved.