Reserch On Efficient Coding And Modulation Algorithm For Hybrid FSO/RF Channel

Free-space optical(FSO)communication has received considerable attention due to its various characteristics including high data rates comparable to fiber optics,license-free and easy installation.However,FSO communication is susceptible to atmospheric conditions with drawbacks in reliability and availability.Radio frequency(RF)communication system has high reliability.So,combining the advantages and avoiding the disadvantages of either FSO or RF alone,hybrid FSO/RF networks has a great significance to improve the reliability of free space optical system.The research on hybrid FSO/RF communication include the switching mechanism between FSO link and RF link,hybrid channel coding and hybrid modulation scheme.In this master thesis,we investigated the bit error rate of hybrid FSO/RF system with LDPC hybrid channel coding and different hybrid modulation schemes under various channel conditions.The main work of this paper is as follows:(1)Firstly,the influence factors of FSO and RF communication are introduced.Then the Gamma-Gamma model and the Rician model are selected as the channel model of FSO and RF link respectively.Finally,the correctness of the model is verified by simulation.(2)The switching scheme of hybrid FSO/RF system is discussed.And the influence of different switching mechanism was analyzed for FSO/RF hybrid communication system.(3)The principle of LDPC hybrid channel coding and hybrid modulation scheme are firstly depicted in detail.Then their bit error rate performence are simulated with the SNR of FSO link under different channel conditions.Finally,five different hybrid modulation schemes are simulated and analyzed in detail for hybrid FSO/RF communication system.The results show that the hybrid coding and modulation schemes investigated in this paper can improve the performance of hybrid FSO/RF system by changing the transmission ratio between RF link and FSO link.Simultaneously transmission between FSO and RF link can improve the bandwidth utilization of the hybrid system,reducing the waste of system resources.