Research On VLC-Based Indoor Positioning System

Location-based services(LBs)are becoming more and more important in our daily life.Knowing the position of an object or person is an essential and basic technique for developing multitude LBs applications.For the outdoor scenario,the global positioning system(GPS)is widely used and has a good performance in many cases.But for the indoor environment,it fails for the walls and tall buildings blocked the signals from GPS satellites and its positioning error can,at times,at the range of several meters,which is not acceptable for indoor environment.Under such circumstance,many alternatives have been proposed for indoor positioning in the published works.These positioning systems are based on radiofrequency identification(RFID),infrared(IR),Wi-Fi,ultrasonic,wireless local area network(WLAN)and image sensing.But these systems each have their own defects,such as,additional infrastructure,low positioning accuracy,electromagnetic interference,low security,high implementation cost and long response time.In recent years,positioning systems based on visible light communication(VLC)have gained popularity as effective alternatives for indoor positioning.The VLC-based systems have such advantages as the LED sources without producing EM interference,and thus can be used in RF sensitive environments.Moreover,LEDs are currently being installed in many modern buildings to replace the conventional fluorescent lamps for its energy efficiency and durability.So,considering its wide availability,durability,and can be used for uniform illumination and communication simultaneously,VLC-based positioning systems are the ideal choices for indoor positioning.There are different distance estimation algorithms that have been used in published papers about the VLC-based positioning system.These mainly include received signal strength(RSS),time difference of arrival(TDOA),and phase difference of arrival(PDOA).Most systems in the previous papers are worked in very specific idealized circumstances in which parameters such as the luminous power of the LEDs,the radiation pattern of each LED and the modulation depth are precisely known.For these idealized cases,high positioning accuracy goal is achievable.But the determination of how these parameters affect the positioning accuracy will help to optimize the system parameters that affect the positioning accuracy and to achieve higher accuracy.In this paper,the main research works are as following:1.The simulation platforn is designed considering the VLC system's illumination requirement,communication needs and positioning requiement.In considering the needs of the lighting system,after the communication needs and location requirements for system simulation platform was designed.The whole intersection centroid algorithm is proposed based on the traditional centroid algorithm.In order to achieve better positioning performance,we use some statistical methods and adopt the least squares filtering algorithm and the maximum likelihood filtering algorithm into the RSS-based VLC indoor positioning system.The simulation results show it improved the positioning accuracy.2.The factors to positioning accuracy like Lambertian parameter m,the receive height,the incidence angle and the optical power are analyzed by deriving the Cramer-Rao bound(CRB),which is a widely used method to analyze the theoretical accuracy in estimation.And to make the simulation results more closer to the real environment,both direct and indirect sunlight exposure scenarios is considered.To simplify the analysis,we assume that both the receiver axis and the transmitter axis to be parallel.