Research On Visible Light Communication,Positioning And Joint Layout Under Indoor Dense Coverage

With the increase of carrier frequency,optical wireless communication(OWC)technology in the Petahertz frequency band has received extensive interests from both academia and industrial fields in recent years.With the advancement of the national green lighting project and the rapid development of high-power light-emitting diodes(LEDs),OWC technology of visible light frequency band-visible light communication(VLC)was born,which has the advantages of no radio frequency(RF)electromagnetic interference,no need for spectrum certification,low device cost,high data rate,and potentially wide application.On the other hand,indoor visible light positioning(VLP)technology makes up for the problems of WiFi,Bluetooth,and infrared,such as low accuracy,complex implementation and high cost of positioning technologies.In recent years,it has attracted extensive attention by academia and industry,which is regarded as a promising solution with high positioning accuracy,high energy efficiency and long duration.Due to the surge in data traffic and the wide use of mobile terminal devices,wireless local area network is facing problems such as limited bandwidth of short-distance access and limited communication rate per unit area.Due to limited transmission and interference,the deployment of indoor dense optical cells can be realized in VLC,which can satisfy the needs of massive access and high communication rates for indoor user terminals.Practical system design will be addressed in the future,and in-depth research on VLC,VLP and the design of joint layout under indoor dense coverage will be conducted to provide guidance for system parameter and joint layout scheme,which is crucial to practical application of VLC and VLP.This work studies the user transmission rate per unit area under indoor dense coverage,the 2D VLP algorithm and system implementation based on mobile phone camera,3D positioning error metric analysis and the joint layout of VLP and VLC.Through theoretical modeling derivation,experimental methods and simulation analysis,the performance of VLC and VLP systems under dense coverage is explored,and the optimization criteria for system parameters under indoor dense coverage is given.The centimeterlevel high-precision VLP system based on commercial camera is realized,and the reference criteria and theoretical basis for indoor dense LED layout are provided.For the user transmission rate per unit area under indoor dense coverage,which is modeled based on LED Lambertian radiation model and the signal-to-interferencenoise ratio(SINR)of densely receiving users.The transmission protocol based on the division of the central and boundary area is designed to optimize the half-power angle,and further to reduce the inter-cell interference and maximize the user transmission rate per unit area.The comprehensive effects of different central and boundary area,time slot,LED half-power angle,user rate fairness in different areas,and lighting uniformity constraints on system performance are discussed.Combined with the analysis of parameter optimization results and the comparison of system performance,the selection critetion of combined optimization parameter under different actual scene requirements are given.For the 2D VLP based on mobile phone camera,through the modeling of indoor VLP system and the analysis of the factors affecting the positioning accuracy,the algorithm based on avalanche photo diode(APD)and camera receiving using received signal strength(RSS)with known LED coordinates,as well as the algorithm based on the translation and rotation model of camera imaging using image Hough processing with unknown LED coordinates,are proposed.Model parameter estimation,initial reference point and rotation center calibration methods are explored to weaken the positioning error.The VLP systems with 3 indoor LEDs in the two cases are realized with centimeter-level high positioning accuracy in a typical indoor 2D application scenario,where the transceiver height is greater than 2 m.For the exploration of 3D positioning error metric and VLP layout under indoor dense coverage,the positioning scheme based on the transformation of different coordinate systems in the translation and rotation model is proposed,based on the corresponding relationship between the 3D LED coordinate in the world coordinate system and the 2D coordinate projected on the pixel plane.The positioning error metric is obtained by analyzing the partial derivation of the position to be estimated in the pixel domain.Furthermore,the rotation performance in the 2D plane and 3D space is simulated.The inverse approximation between the positioning error metric and the number of captured LEDs under different dense layouts in the parallel transceiver plane scene is validated.Then,non-uniform but symmetrical structure LED layout is optimized for the dense LED square layout in VLP.For the joint layout of VLP and VLC under indoor dense coverage,based on the optimization results of LED square layout in VLP,the joint layout optimization of VLP and VLC is considered.For different dense LED layouts,the effect of positioning error metric and the average transmission rate are investigated under the consideration of user rate fairness in different areas and uniform lighting.The utility function is proposed to characterize the joint performance of VLP and VLC,and the optimal values of certain LED layout parameters under different utility functions is addressed.The layout optimization criterion with dense LED in central area,sparse LED in boundary area,and a more uniform overall LED distribution is provided.