Research On O-OFDM Technology For Indoor Visible Light Communication Systems

Visible light communication(VLC)is gaining constantly increasing research in wireless transmission,short distance transmission and high speed access technology because of the enormous spectrum resources.In this paper,the modulation technologies in high-speed VLC are thoroughly studied,and the researches focus on optical OFDM(Optical OFDM,O-OFDM)approaches which suitable for indoor optical channel.Several spectrum efficient and low complexity O-OFDM schemes are introduced and presented,the OFDM signals generation of these solutions is based on Fast Fourier or Hartley transform.For FFT-based O-OFDM schemes,HACO-OFDM,AP-OFDM and PF-OFDM are mainly introduced.The unipolar process of HACO-OFDM and PF-OFDM can be performed in Cartesian coordinate,and AP-OFDM in Polar Coordinate.This paper discussed the principle of modulation/demodulation process and spectrum utilization improvement by constructing system model.Researches show that all three approaches double the spectral efficiency of ACO-OFDM and achieve better performance in terms of power efficiency over DCO-OFDM.In addition,the simulation results demonstrate significant BER and PAPR performance advantages.Therefore,the three methods are appropriate for reliable high-speed indoor VLC system.For FHT-based O-OFDM schemes,HP-OFDM,HPF-OFDM and MU-OFDM are proposed.The application of fast Hartley transform in O-OFDM systems can reduce computation complexity and spectrum consumption.The HP-OFDM and MU-OFDM offer twice as much spectral efficiency as ACO-OFDM,HPF-OFDM offers twice data rate of DCO-OFDM.The above solutions still maintain high energy efficiency.Furthermore,HP-OFDM adjusts PAPR and BER performance by varying the power allocated to time domain signals,getting the best communication performance based on optimal energy allocation.HPF-OFDM transmits multiple parallel information streams to possess better effectiveness and PAPR performance.MU-OFDM is introduced into dimming control system for its advantages in effectiveness and reliability.Simulation results show that the MU-OFDM dimming control system can achieve better communication performance in the mean time without sacrificing illuminating quality.In conclusion,the best O-OFDM scheme in VLC system is to achive a good compromise performance of power/spectral efficiency,BER/PAPR performance and implementation complexity based on practical application requirements.