Research On Indoor Positioning Technology Based On LED Visible Light Communication

Indoor positioning technology has important application prospect in shopping mall, large-scale public building, hospital, high-risk industry area, nursing homes, etc., but the research on improving location accuracy and speed is still difficult point. So, the research on indoor positioning technology has important theoretical significance and application value. Through modifying the driver of the LED lamp and using the camera of mobile terminal as receiving device, mobile terminal gets location information based on LED visible light communication(VLC) indoor positioning technology. Compared with other positioning technologies, LED VLC indoor positioning technology has higher accuracy, stronger portability and simpler implementation. Nowadays, more and more scholars attach great importance to the study of this technology.Based on the analysis of existing LED VLC indoor positioning technologies, this thesis launches the research from the following problems, the problem of coding efficiency, the problem of inaccuracy caused by poor lamp layout, the problem of Inaccurate positioning formulas and the failure of tracking, etc. And by building a LED VLC indoor positioning system verifies the proposed the research content.The main innovation and research results are as follows:1) In order to achieve the general lighting compatible with VLC, the new type LED down light is designed based on color mixing theory. Further, LED color mixing optimization algorithm is proposed based on the improved artificial fish swarm algorithm(AFSA). Opposition-based reinforcement learning, Normal and Cauchy distribution function are adopted to improve the convergence rate and accuracy of AFSA. LED proportions among those LEDs are optimized by AFSA and improved AFSA in the Matlab. Results indicate that improved AFSA has the higher convergence rate and accuracy. After LED lamps are tested by integrating sphere, the results demonstrate that the new method achieves higher luminous efficacy and higher color rendering index for lamps than traditional methods.2) For unevenness of illumination has a strong effect on positioning accuracy, improved AFSA is adopted to optimize indoor lighting layout. AFSA has a slow convergence rate in the later phase of iterations, multi-parent crossover operator, Cauchy mutation operator and modified minimal generation gap model are adopted to improve AFSA. Results indicate that improved AFSA has the higher convergence rate and accuracy, and illumination uniformity increases by 53% after optimization. Further, the results are proved in Dialux.3) For existing coding methods have low coding efficiency in the LED VLC indoor positioning system, variable length color coding(VLCC) technique is proposed in this thesis. New coding and decoding rules are designed and several properties are discussed for the VLCC. The VLCC has been applied to practice and obtained good results.Compared with the existing several encoding methods, the VLCC has the highest coding efficiency.4) Methods that how to get location information of a stationary target from LED beacons are proposed. Existing 3D measurement formulas with monocular camera are derived from the pinhole camera model, without considering the size of the lamps. According to the imaging principle of an ordinary camera, new positioning formulas are deduced based on geometrical optics. Morphologic filter and contour search operation are implemented to find out the lamp image. Color, black and white stripes are extracted from the lamp image and decoded based on the VLCC decoding rules. The camera location information is obtained by new positioning formulas. The experiments indicate that the positioning error between the model calculation and practical measure is less than 5cm.5) The Particle target tracking algorithm(PTTA) is proposed based on the target geometry feature and the VLCC. Color feature and heuristic search method are employed in the PTTA. On the contrary, target feature is one fixed color histogram both in particle filter algorithm and Mean-shift algorithm. So, the PTTA can save a lot of computing time. The positioning error between estimated values which are obtained from the LED VLC positioning system(based on the PTTA) and experimental values are less than 5cm.The PTTA is characterized for its simple, reliable, fast real-time performance and tolerance.