Research On Communication And Localization In Indoor Visible Light System

With the extensive development of the wireless communication technology,smart lighting has attracted much attention,along with some functions based on it.Thus,this thesis focuses on the researches on the communication and localization in indoor visible light system.First,for visible light communication(VLC)system,we explored the transmission performance of VLC system under different modulation formats.Considering the condition that the modulation bandwidth of VLC is limited,we developed two methods with high spectrum efficiency(SE)to make full use of the bandwith in VLC system.The first is asymmetrically clipped direct current biased optical orthogonal frequency division multiplexing(ADO-OFDM)and the second is Nyquist-shaped single-carrier(N-shaped SC),and we compared them with asymmetrically clipped optical OFDM(ACO-OFDM)and direct current biased optical OFDM(DCO-OFDM)in VLC system.The bit error ratio(BER)and SE performance are analyzed according to the simulation results,we find that the N-shaped SC-based VLC system is superior to other three forms of OFDM-based VLC systems on both SE and BER performance.In addition,the SE of ADO-OFDM is better than that of ACO-OFDM and the power utilization of ADO-OFDM is better than that of DCO-OFDM.Moreover,it is shown that by varying the proportion of optical power on the ACO-OFDM component and the DC bias level of DCO-OFDM,the transmission performance of ADO-OFDM can be significantly improved.In addition,for the localization in VLC system,we considered three localization algorithms based on the received signal strength(RSS),including trilateration localization algorithm,triangular weighted centroid locatlization algorithm and difference correction localization algorithm.The simulation studies and experimental results indicate that the difference correction localization algorithm can achieve the lowest localization error,traditional trilateration localization algorithm shows the highest localization error,while triangular weighted centroid locatlization algorithm falls between the previous two.