Research On Key Technologies Of Single Photon Detection Visible Light Communications

Visible Light Communication(VLC)technology is a new green information technology that does not occupy the traditional radio spectrum resources.VLC system uses Intensity Modulation/Direct Detection(IM/DD)and uses photo diode(PD)to achieve photoelectric conversion.Due to the low reception sensitivity of PD,VLC has poor performance in low light environments such as underwater,darkroom and long pipes.Single photon detection VLC system uses single photon avalanche diode(SPAD)as the receiver.SPAD has an avalanche effect in Geiger mode,depending on the output of large current as a count,which not only uses the sensitivity of the avalanche effect,but also protects the original information on the optical power not to be destroyed by avalanche effect.Based on single photon detection VLC system model,combined with SPAD working principle and Poisson channel characteristics,the maximum likelihood detection algorithm for single photon detection VLC system and the design of the transmitter are proposed.The main works are as follows:1.Aiming at the problem that the poor performance of the single LED single photon detection VLC detection algorithm,the maximum likelihood detection algorithm with better performance is proposed.According to single photon detection VLC system model,single LED single photon detection VLC is studied with On-Off Keying(OOK)modulation as an example.The bit error rate(BER)of maximum likelihood detection algorithm is deduced and analyzed.Finally,the simulation proves the factors that affect the BER of the system.2.In order to further improve the link quality and transmission rate of the single photon detection VLC,this dissertation combines the Space Modulation technology and the single photon detection VLC for the first time.Multiple LED single photon detection VLC is studied with Space Shift Keying(SSK)modulation as an example and the corresponding maximum likelihood detection algorithm is proposed.According to single photon detection VLC system model,combining with the SSK modulation principle,the maximum likelihood detection algorithm of single photon detection VLC SSK modulation is deduced.The factors influencing the BER of single photon detection VLC SSK modulation are analyzed by simulation.3.As the signals aliasing at receiver caused by multi-user transmit signals in the single photon detection VLC system,a design scheme of additively uniquely decomposable constellation group(AUDCG)was proposed combining the constellation design criteria based on Hellinger distance.Combining with constellation design criteria based on the Hellinger distance,the additive unique decomposable constellation of the transmitter is designed.Then a set of feasible AUDCG constellation and corresponding maximum likelihood detection algorithms are given.The simulation results show that the performance of the AUDCG is better than the common constellation.4.In order to verify the feasibility of single photon detection VLC,A single photon detection VLC experiment system is designed and system tests were performed under different channel conditions.The experimental system is designed according to the principle of single photon detection VLC.The system is measured in the darkroom,long distance and Non-line of sight conditions respectively,the feasibility of single photon detection VLC is obtained by the experimental results.