Research On Multi-dimensional CAP Based Indoor Visible Light Communication Techniques

Visible light communication(VLC)using white light emitting diode(LED)allows the combination of lighting and data transmission,and is becoming an emerging wireless communication technology.VLC is gaining constantly increasing research in the field of indoor high-speed short-range wireless communication because of the advantages of huge unregulated bandwidth resource,high security,low power consumption and cost effectiveness.However,the rather narrow bandwidth of LEDs could potentially limits the throughput of VLC systems,therefore this thesis centered on a spectrally efficient and low complexity modulation format named carrierless amplitude and phase(CAP)is analyzed.For the design of CAP filter banks,two types of traditional two dimensional CAP modulation based on Hilbert transform are introduced,and two types of multi dimensional CAP is designed by solving a minimax optimization problem so that the overall transfer matrix maintains perfect reconstruction of the transmitted information.For the design of CAP VLC schemes,DCO-CAP,Flip-CAP and U-CAP modulation schemes based on multi dimensional CAP are proposed in this thesis.According to CAP signal model and considering line of sight link,the theoretical symbol error rate(SER)of the above mentioned schemes are derived and corroborated by Monte Carlo simulations.Meanwhile,the power efficiency,the spectrum efficiency and the SER performance of three kinds of CAP VLC systems are analyzed and compared.For improving the efficiency of communication,SM-CAP and CAP-OFDM transmission technology schemes are proposed in this thesis,meanwhile the theoretical derivation of the error performance of SM-CAP and CAP-OFDM are deduced.The bit sequence is divided for two parts in SM-CAP system,a part is modulated to represent the spatial information,and another part is modulated by CAP.The simulation results show that SM-CAP could improve spectrum efficiency.In addition,increasing the number of the receiver,enlarging the separation distance between two LEDs,decreasing the distance between the transmitter and receiver,and using something to block the transmission link,can improve the SM-CAP system reliability.In CAP-OFDM scheme,orthogonal CAP filters are used to generate the baseband real signals,and the signal is then loaded into orthogonal carriers by a Hartley transform.Researches demonstrate that CAP-OFDM has advantages on spectral efficiency and SER performance.For improving the reliability of communication,a CAP VLC transmission technology scheme based on turbo code is proposed in this thesis.The structure of parallel concatenated covolutional turbo encoder and decoder and the iterative decoding principle based on the maximum posterior probability algorithm are introduced in detail.Monte Carlo simulation results are provided to demonstrate that turbo code could significantly enhance the system reliability.