| Visible Light Communication(VLC)has become a very potential networking Communication technology due to the development of low carbon cycle characterized by "double carbon" and the sharp increase of people’s demand for Communication.VLC utilizes existing LED lighting fixtures as infrastructure.Its significant advantages are rich bandwidth resources,reuse of lighting power,no electromagnetic interference,no radiation leakage.It becomes one of the communication technologies with the most potential application for indoor hot spots in the future by virtue of its advantages of green environmental protection,safety and high speed,which are difficult to take into account at the same time.However,compared with the communication systems that use microwave antennas and low-noise amplifiers as signal sensing and receiving links,the noise power of the photoelectric conversion devices included in the VLC receiving link is significantly higher,which makes the existing VLC usually use limited lenses.The light power is constrained to a predetermined range to improve the communication rate or communication distance.This approach negatively affects the uniformity of indoor illumination and the mobility of communication terminals,resulting in the inability of VLC to be reused with the existing lighting infrastructure,thus limiting the application of VLC.This thesis focuses on the study and verification of the downlink visible light communication and networking in the conventional LED lighting power and open light field,for the downlink flow is significantly higher than the upstream application.It mainly conducts theoretical research and design demonstration on the multiple access,frame structure,master-slave node physical layer transmission protocol of VLC networking,and builds a video transmission system based on VLC networking.The main research contents of this thesis are as follows:1.Firstly,this thesis systematically summarizes the transmission characteristics of visible light communication system,including the analysis of LED front-end,photoelectric conversion front-end,visible light indoor channel,etc.,and on this basis,a VLC networking system design method based on TDMA is proposed.2.Then,this thesis designs the physical layer(Physical Layer,PHY)layer protocol and the media access control sublayer(Media Access Control,MAC)protocol in detail,including the master-slave node access protocol,frame structure,synchronization algorithm,etc.In particular,this thesis uses time correction time slot to extract the time error of each node and maintain the network time synchronization,which improves the transmission efficiency and reliability of visible light link and ensures the orderly and conflict-free service information transmission of multi-user terminals in the system.3.Based on the above work,using the development environment of System Generator,the MAC and PHY protocol models are implemented,and the fixed-point simulation verification of each module in the model is carried out.Then,based on the VLC system with four receivers and four transmitters designed by the research group with ZYNQ as the core,the experimental verification was completed in an indoor environment of 3×3×3 meters.Under the condition of 3 watts of light power,the system can smoothly transmit 720 p multimedia broadcasting services.During the 7th International "Internet +" period,as a typical achievement of the new engineering construction of the Ministry of Education of Nanchang University,this system was displayed in the new engineering practice base,and received the attention and guidance of many experts. |
PDF Full Text Request