Research On Indoor Visible Light Positioning System Based On LED

With the rapid development of the technology,people's demand for wireless positioning is increasing.GPS is very difficult to locate accurately in indoor environment.Although radio frequency and WLAN positioning methods can achieve indoor positioning,they are limited by the need for additional infrastructure,non-electromagnetic interference and low scalability.Recently,visible indoor positioning has attracted much attention due to its advantages of anti-electromagnetic interference and no need for additional infrastructure.However,because most positioning algorithms need more than one LED to achieve positioning,coding and distinguishing the light signals emitted by different LEDs becomes an indispensable step,which undoubtedly increases the complexity of positioning.In this paper,two kinds of visible indoor location algorithms are proposed.In these two algorithms,only one lamp is needed to locate,and no coding processing is needed for the LED,which reduces the complexity of location and improves the accuracy of location.In addition,if we want to further study the indoor location of visible light in the experiment,it is indispensable to build a visible light communication system.In order to solve the problem that there is only downlink and no uplink in the visible communication system,this paper proposes a two-way visible communication system with LED as both the transmitter and the receiver.The main work and achievements of this paper are as follows:1.After reading a lot of literature to analyze the status of location algorithm,combined with fingerprint location method,a single-shot multi-receive indoor location algorithm is designed.The transmitter of the algorithm is an LED,and the receiver is composed of three receivers with different angles.Before locating,fingerprint database needs to be established:uniformly select points in the locating area,measure the three light intensity values received by three receivers at every point,and the difference of the light intensity received by the receiver at all points constitutes the fingerprint library.When positioning,the difference of three light intensity values received by the receiver is compared with that in the fingerprint database,and the contour of the light intensity difference is drawn.The intersection point of the contour is the location point.Finally,the coordinate of the intersection point can be obtained to realize the positioning.The simulation experiment is carried out in the environment of 5m × 5m × 3m and the average positioning error is 5.829cm.2.When using single-shot and multi-receive location algorithm to locate,it is necessary to compare with all the data in fingerprint database,which has a huge amount of computation.For this reason,a two-step localization method is obtained by combining geometric ranging method with fingerprint localization method,which further reduces the localization complexity.In this method,the approximate range is estimated by RSS,and then compared with the fingerprint in this range to achieve location.This method can further reduce the location complexity and computing time.3.Aiming at the problem of lack of uplink in visible light communication system,we propose and implement a real-time bi-directional visible-light communication system with light-emitting diodes as both optical signal transmitter and receiver.We also design the mechanism of controlling LED bi-directional work by the way of time-division multiplexing to achieve a bi-directional visible light communication.The real-time two-way communication system experiments are done under the different transmitter and receiver elevation angle,the results show that the system scheme can realize real-time bi-directional visible light communication in more than 2m and 8Mbit/s only with LED as optical transmitter and receiver,without strict alignment and relaying amplification.