LED-based indoor positioning system using novel optical pixelation technique

At present, about 47 million people worldwide have Alzheimer's disease (AD), and because there is no treatment currently available to cure AD, people with AD (PWAD) are cared for. The estimated cost of care for PWAD in 2016 alone is about $236 billion, which puts a huge burden on relatives of PWAD. This work aims to reduce this burden by proposing an inexpensive indoor positioning system that can be used to monitor PWAD. For the positioning, freeform lenses are used to enable a novel optically pixeled LED luminaire (OPLL) that focuses beams from LEDs to various parts of a room, thereby creating uniquely identifiable regions which are used to improve positioning accuracy. Monte Carlo simulation with the designed OPLL in a room with dimensions 5m × 5m × 3m is used to compute the positioning error and theoretical analysis and experiments are used to validate the time for positioning. Results show that by appropriate LED beam design, OPLL has a positioning error and time for positioning of 0.735 m and 187 ms which is 55.1% lower and 1.2 times faster than existing multiple LED estimation model proximity systems

Design of improved IR protocol for LED indoor positioning system

In this work, we design an infrared protocol (IRP) for light emitting diode (LED) based indoor positioning. The designed IRP compensates for the shortcomings of other existing protocols when applied to the multiple LED estimation indoor positioning model (MLEM). MLEM uses overlap of LED beams to increase accuracy of positioning. The overlap sets up a multipoint-to-point optical communication channel. The existing protocols which are designed for point-to-point links, when modified to suit the MLEM overlapping region, show a high positioning time between 3 s and 4.5 s. These values are not desirable for real time tracking. A new protocol is therefore designed to reduce the positioning time. The protocol is implemented in an experimental MLEM design using ATmega 328 microcontroller hardware. The experimental results show the new protocol reduces the positioning time to 0.5 s

Optical boundaries for LED-based indoor positioning system

Overlap of footprints of light emitting diodes (LEDs) increases the positioning accuracy of wearable LED indoor positioning systems (IPS) but such an approach assumes that the footprint boundaries are defined. In this work, we develop a mathematical model for defining the footprint boundaries of an LED in terms of a threshold angle instead of the conventional half or full angle. To show the effect of the threshold angle, we compare how overlaps and receiver tilts affect the performance of an LED-based IPS when the optical boundary is defined at the threshold angle and at the full angle. Using experimental measurements, simulations, and theoretical analysis, the effect of the defined threshold angle is estimated. The results show that the positional time when using the newly defined threshold angle is 12 times shorter than the time when the full angle is used. When the effect of tilt is considered, the threshold angle time is 22 times shorter than the full angle positioning time. Regarding accuracy, it is shown in this work that a positioning error as low as 230 mm can be obtained. Consequently, while the IPS gives a very low positioning error, a defined threshold angle reduces delays in an overlap-based LED IPS

Mobility management in multi-tier LiFi networks

Mobility management is an important part of the analysis and design of ultra-dense LiFi networks. This paper presents a two-tier LiFi network and analyses the cross-tier handover rate between the primary and secondary cells. For different conditions of semiangle at half illuminance of the primary and secondary cells, we propose three different coverage models for the secondary cells. Using stochastic geometry, closed-form expressions are derived for the cross-tier handover rate, ping-pong rate and sojourn time in terms of the received optical signal intensity, time-to-trigger and user mobility. The analytical models are validated with simulation results

Indoor localization based on multiple LEDs position estimation

This paper describes the simulation results and hardware implementation of an inexpensive, low-complexity LED based indoor positioning system. Localization by multiple LEDs estimation model (MLEM) approximates position of a mobile receiver by the acquisition of positional information from LED transmitters. Multiple LED orientation can either be with or without overlap. Receivers in a no-overlap LED orientation experience only single access while multiple access receivers are designed for orientations with overlaps. Single and multiple access systems were developed and implemented by the use of low cost ATMEG 328 microcontroller. Since multiple LEDs transmit data at the same wavelength and are asynchronous, overlap in multiple access system causes interference. The possibility of this interference is reduced by packet based pulse duration multiplexing (PDM) and a low duty cycle transmission protocol. By the use of MLEM, root mean square error in position estimation is reduced to about 1 percent of the length an indoor location. Experimental results show that overlap increases positional accuracy over a wider coverage region and that the multiple access system allows for a more reliable positioning