Research And Application Of Key Technologies In Optical Camera Communication

Visible light communication(VLC)system transmits information through high-speed bright and dark visible light signals emitted by LED,and realizes high-speed wireless data transmission while meeting the daily lighting requirements.VLC system has the advantages of green,low-carbon,wide spectrum bandwidth,high communication rate,free from electromagnetic interference,and can be used in restricted areas of radio frequency communication.There are two main types of VLC systems.The VLC system based on photodetector(PD)has a high speed,owing to the change of environment and driving voltage,the optical power intensity of the receiving end is unstable,which affects the communication performance.The VLC based on image sensor(i.e.Optical Camera Communication,OCC)has the ability to separate and receive optical signals in the space and color fields,and has a high signal-to-noise ratio.OCC has broad prospects in the future wireless optical communication environment,is one of the key technologies of the Internet of Things,and has become a hot research topic.In this dissertation,the modulation technology of camera communication is studied on the existing theoretical basis,and the built communication system is verified by experimental method.The main contents of this dissertation are as follows:(1)Currently,the main modulation modes of OCC are screen-based modulation,oversampled modulation and undersampled modulation.Firstly,this dissertation introduces the modulation principles of these three OCC systems using low frame rate camera detectors,briefly analyses the signal coding methods and their respective advantages and disadvantages,and gives the processing methods of digital image signals received by different modulation methods.(2)In order to evaluate the performance of these modulation schemes,three different modulation schemes are experimentally analyzed,and the measured transmission rate or bit error rate are given respectively.For undersampled modulation OCC,an optimization method of undersampled modulation scheme is proposed under the condition of current rate-constrained signal coding.Multi-order brightness and multi-LED modulation scheme is used to reduce the influence of non-linearity of LED,so as to achieve a higher spectral efficiency of non-flickering OCC.Compared with the traditional encoding method,the proposed scheme has better transmission performance by comparing the bit error rates at different distances.(3)At the end of this dissertation,the current research status of indoor visible light location methods at home and abroad is analyzed.The camera communication combined with backward transmission neural network algorithm is applied to indoor visible light location,and an indoor visible light location method based on camera communication is proposed.Through the validation of the built experimental system,the average positioning error of the system can reach 1.52 cm in the designated area,which fully meets the positioning requirements.