Research On Indoor Localization Algorithms Using Visible Light Communication Based On LEDs

Various indoor visible light positioning algorithms are analyzed in this thesis, including the Received Signal Strength (RSS), Time Difference of Arrival (TDOA), Time of Arrival (TOA), Angle of Arrival (AOA) and hybrid localization algorithm etc. Firstly, the fundalmental positioning principle of the various algorithms is given, especially the RSS and TDOA positioning algorithms based on LED visible lights are thoroughly investigated.Due to some limitations for the applicability, location area and low accuracy of the RSS positioning algorithm, a scheme utilizing multiple LED transmitters to achieve indoor positioning and four-LED weighted positioning algorithm is proposed in this paper. In the proposed multiple LED scheme, the basic principles of positioning unit selection is introduced with fully considering the impact of LED topology on positioning performance. It effectively solve the block or shadow effect existing in indoor visible location. Based on the feature that high positioning accuracy of short transmission distance, the transmission distance information as a weighted factor is introduced in the four-LED weighted positioning algorithm to improve the positioning accuracy and expands the location area. Furthermore, it effectively improve the universality of application.Aimed at some limitations of current TDOA localization algorithm with disconvergence, low accuracy and complex implementation, a nonlinear optimization algorithm using white lighting LEDs and areas cooperative indoor positioning algorithm is proposed in this paper. In the nonlinear optimization algorithm, the differences of transmission distance between the position terminal and LEDs are used to construct a distance estimate objective function. By utilizing a nonlinear programming algorithm with constraints, the position coordinates of the terminal can be obtained. It effectively solves the problem of divergence as well as large deviation in the case that conventional TDOA algorithm is used in indoor noisy environments. Meanwhile, the transmission distance information as a weighted factor is introduced in the positioning called centroid weighted localization algorithm in order to optimize the positioning results further. In the areas cooperative algorithm, Multi-areas illuminated joint localization idea is introduced in this algorithm with fully considering the influence of all kinds of noise in indoor optical channel. Transmission time differences between each LED and positioning node are obtained to construct an objective function of cooperative positioning in terms of distance estimation by the use of reference signal from different LEDs. Then, the target location is computed through nonlinear least squares algorithm. It improves the indoor positioning precision and universality of application as well as system robustness, furthermore, effectively solves the block or shadow effect existing in indoor visible location and also work on dynamic positioning and tracking.