| Visible light communication(VLC)technology,as a new wireless communication technology,can not only provide free spectrum resource,but also realize the dual functions of lighting and communication,which has gradually become one of the research hotspots of academic and scientific researchers.Light-emitting diode(LED)has been widely used in our daily life.It can be used as the light source of VLC,where the baseband signal is modulated to the LED visible light for data transmission.In this way,information can be transmitted at a high speed without being detected by human eyes.In addition,VLC technology also has the advantages of high bandwidth,low power consumption,low cost,and high confidentiality,compared with the traditional radio frequency(RF)communicationSpatial modulation(SM)technology as a simple multiple input multiple output(MIMO)technology,can effectively avoid inter-antenna synchronization(IAS)and inter-channel interference(ICI),and has low signal detection complexity.In this thesis,the high efficient multi-dimensional modulation scheme in VLC system is studied,which guarantees the system reliability and efficiency simultaneously.The main research work of this paper is as followsFirst,in order to improve the spectrum efficiency and performance of the system,a generalized spatial modulation(GSM)scheme based on color shift keying(CSK)modulation by considering the advantages of GSM and CSK modulation is proposed in VLC system.Compared with SM scheme,it can simultaneously activate several Triple-color LEDs(TLEDs)to transmit information at the transmitter,which effectively improves the system spectrum efficiency and space resource utilization.The theoretical bit error rate(BER)performance is derived based on Euclidean distance method and analyzed in detail.In addition,the influence of elevation angle of photoelectric detector(PD)on the system performance is also provided.Finally,the simulation results verify the correctness of the theoretical derivation and the superiority of the system performance.Secondly,a color space and multi-stream spatial modulation(MSM)based indoor visible light communication scheme from the perspective of increasing color selection and reducing channel correlation.The scheme uses the color selection of transmitted quad-LED(QLED)as a new bit mapping method,which extends the dimension of signal modulation and effectively improves the spectral efficiency of VLC system.In addition,by comparing the channel correlation of all possible activated QLED groups,the scheme selects the combination with less channel correlation for information transmission,which effectively improves the reliability of system transmission.According to the theoretical performance analysis of the system,the expression of the theoretical upper bound of the system's symbol error rate(SER)is given.Finally,the simulation results verify the correctness of the theoretical value derivation.At the same time,the simulation results show that the system performance of the proposed scheme is obviously better than other VLC schemes based on SMFinally,a cooperative SM VLC scheme based on CSK modulation is proposed by combining VLC technology with communication technology,this scheme utilizes the advantages of CSK modulation,cooperative spatial modulation and relay with decode forward(DF)protocol,which effectively avoids the object block,the effects of the channel fading and shadow effect,so as to improve the transmission reliability and communication range.The simulation results show that the performance of cooperative SM scheme based on CSK modulation in VLC is better than that of traditional cooperative VLC spatial modulation system and spatial modulation system based on CSK modulation. |
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