Time-Frequency Based Two-LED Positioning In Visible Light Communication

Traditional indoor visible light positioning usually uses three light sources for location estimation.However,in practical scenarios,if the distance between the LED and receiver is too far or if the direct signal of the LED is blocked by furniture or other objects,it may result in a situation where the conditions for three-LED positioning are not satisfied within the field of view of the receiver.Therefore,research on two-LED positioning is urgently needed.This thesis first analyzes the existing research on two-LED positioning and single-LED positioning.Considering the problems of complex equipment and complicated algorithms,this thesis proposes a two-LED positioning scheme that integrates mirrors,based on the widespread use of mirror materials in daily life and the higher reflection efficiency of Mirror Reflection Communication.Furthermore,this thesis discusses the specific implementation plan of the time-frequency combination-based two-LED positioning approach.Namely,it takes the mirror-reflected power of a virtual light and adds it to the effective positioning power of its corresponding real light.It also separates the other virtual light to make it an independent third light source for positioning,thereby achieving a simpler two-LED positioning.Traditional visible light positioning usually uses multiplexing to achieve signal separation at the receiving end,while this thesis uses the time-frequency combination method to separate virtual and real signals based on their different distances to the receiver,leading to different time-of-arrival of their respective pulse signals.Finally,this thesis conducts simulations on the proposed positioning scheme.The results show that the distribution trend of the positioning errors of the two-LED model presents a slope shape,where positioning error increases with the distance between the test point and the mirror.The area close to the mirror can achieve centimeter-level accurate positioning.Based on this characteristic,this thesis proposes a room model suitable for two-LED positioning,namely the long corridor model,and further optimizes the positioning effect by adjusting the position of the LEDs.Research results show that the two-LED positioning method can achieve relatively accurate positioning in scenarios such as long corridors.When the distance between LEDs and mirrors is0.5m,the average positioning error is 8cm.The area with positioning error less than 5cm accounts for less than 50% of all test points,while the area with positioning error less than 10 cm accounts for approximately 67%.Due to the requirement of non-overlapping pulse signals of virtual and real lamps for signal separation using the time-frequency combination method,some areas in the room cannot meet this condition and cannot further realize positioning.This thesis applies the above conditional equation and mathematical models to make inference on the movable range of the receiver based on time-frequency combined approach.