Research On Key Dynamic Technologies For OCC Between Multiple Light Sources And A Rolling Shutter Camera

With the popularity of mobile communication terminals and the increasing demand of communication services,wireless communication networks have entered the era of big data.In order to solve the shortage of spectrum resources,Petahertz(PHz)commu-nication will become the key technology in the future.Optical camera communication(OCC)based on a rolling shutter camera is a kind of Petahertz communication,and its transmitter is composed of single light source or multiple light sources arranged in an array.Unlike the traditional Petahertz communication using PD(Photodiode)or APD(Avalanche Photodiode)as the receiver,there is no need for strict alignment between the transceiver in the OCC system based on the shutter camera,and the transmitter is a common commercial LED light source.This lays a solid foundation for the realization of near-field mobile communication.However,there are many problems such as frame structure design and demodula-tion algorithm,crosstalk suppression scheme between light sources and communication performance constraints in a dynamic environment in the dynamic OCC system between an array light source and rolling shutter camera.This paper mainly studies the technical difficulties existing in the following two parts:one is how to improve the data rate of the communication system;the other is how to analyze the maximum dynamic range.Firstly,the basic principle of OCC based on rolling shutter effect and the timing mechanism in imaging process is analyzed.Then the measurement method of inter-frame interval is proposed.A Beacon-based design and data splicing scheme is intro-duced to effectively extend the length of subframe and reduce the subframe retransmis-sion times.Next,the experimental platform of the OCC system from single light source to camera is established,and the synchronization algorithm and data splicing scheme are proposed.When the frame rate is 48 fps and the oversampling factor is 6,the data rate reaches 15.264 kbps.Such rate represents the highest among existing OCC systems from single LED to a rolling shutter camera under the condition of the same resolution and frame rate.Compared with the OCC system with single lamp,the system with a light source ar-ray can effectively utilize the information of image column therefore improve the trans-mission rate of the system effectively.The experimental platform is established,and the scheme of data splicing is improved.The channel matrix under different crosstalk con-ditions is measured by experiment when the separation distance of the transmitter light sources is changed.The scheme of applying symbol level precoding to OCC system is proposed to suppress crosstalk between light sources.Finally,the simulation results of the demodulation BER are given when the noise model parameters change.The results show that the precoding scheme can effectively improve the receiving range in the re-ceived image.The communication performance in the severely disturbed intermediate region is improved obviously.When the distance,deflection angle and azimuth angle of the receiving end change dynamically,the number of effective rows in the received image of the light source area will change.If the frame structure is not matched to the receiver,the synchronization head may be lost and causes failure of data transmission.How to transform the phys-ical parameters between the transceiver in space to the coordinate transformation of the receiving region in the image remains a difficult topic.We first study the effect of distance on the number of imaging rows according to the imaging model of camera.Following the simulated camera imaging process model,the effective receiving area of the light sources is derived under current deflection or azimuth angle settings.Finally,combining the aforementioned frame structure design and demodulation algorithm,the change of subframe retransmission times and total system transmission rate in the dy-namic model is analyzed and deduced.The results of the maximum dynamic range with data rate constraint are given,and they provide a reference for other rolling shutter based OCC system in dynamic scenes.