Research On Nonideal Transmission Characteristics Of High-speed Visible Light Communication Systems

Visible light communication(VLC)technology has played key roles in op-tical communication research fields.With traditional fluorescent lamps and in-candescents are replaced by light emitting diode(LED)which is more efficient,the VLC technology has an opportunity to become the dominant technology of next generation indoor communication technology.Because of VLC technol-ogy using LEDs to transfer information,it has the characteristics of both com-munication and illumination.Compared with traditional wireless communica-tion technology,VLC technology has the advantages of high-capacity,high-efficiency and high-security.Moreover,VLC technology is more cost-efficient in infrastructure,because LEDs are widely used in indoor lighting.However,there are deep and challenging questions in VLC fields.The nonideal trans-mission characteristics of high-speed VLC systems is often considered as the crucial and decisive factor in restricting the development of VLC technology.In high-speed VLC systems,nonideal transmission characteristics are caused by the limited bandwidth of LEDs and nonlinear effect of systems.So two improving nonideal transmission characteristics of VLC systems schemes are present in this paper:· Hybrid run length limited(RLL)code and pre-emphasis technique to re-duce wander and jitter on on-off keying nonreturn-to-zero(OOK-NRZ)VLC systems is proposed for improving nonideal transmission characteristics of high-speed VLC systems.On OOK-NRZ VLC systems,the nonideal transmission characteristics re-sult in baseline wander(BLW)and data-dependent jitter(DDJ)phenomenons.And BLW and DDJ phenomenons affect the performance of communication rate and reliability.This scheme utilizes RLL code and pre-emphasis techniques to depress the influence of BLW and DDJ.In the experiment,hybrid RLL code and pre-emphasis technique can improve the performance of OOK-NRZ VLC system up to 130Mb/s with a phosphor-converted white LED.Hybrid circuit equalizer and digital equalization algorithms to reduce in-tersymbol interference(ISI)on OOK-NRZ VLC systems is proposed for im-proving nonideal transmission characteristics of VLC systems.For a single equalization scheme,the contribution to reduce the influence of nonideal transmission characteristics is limited,because both circuit equal-izer and digital equalizer orders are limited.This scheme can improve the VLC system performance by mixing circuit equalizer and decision-feedback-equalizer(DFE)based on least mean square(LMS)algorithm.