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

LTE RSRP, RSRQ, RSSNR and local topography profile data for RF propagation planning and network optimization in an urban propagation environment

In the design of 5G cellular communication to guarantee quality signal reception at every point within a coverage area, fundamental knowledge of the channel propagation characteristics is vital. A correct knowledge of electromagnetic wave propagation is required for efficient radio network planning and optimization. Propagation data are used extensively in network planning, particularly for conducting feasibility studies. Hence, measurement of accurate propagation models that predict how the channel varies as people move about is crucial. However, these measured data are often not widely available for channel characterization and propagation model development. In this data article, the Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ) and Reference Signal Signal to Noise Ratio (RSSNR) at various points in space which is covered by a Long-Term Evolution (LTE) marco base station operating at 2100 MHz located in Hatfield, Hertfordshire, United Kingdom were measured. Further, local topography profile data of the study area were extracted from a digital elevation model (DEM) to account for the features of the propagation environment. Correlation matrix and descriptive statistics of the measured LTE data along different routes are analyzed. The RSRP, RSRQ and RSSNR variation with transmitter (Tx) – receiver (Rx) separation distance along the routes are presented. The probability distribution and the DEM of LTE data measurement are likewise presented. The data provided in this article will facilitate research advancement in wireless channel characterization that accounts for local topography features in an urban propagation environment. Moreover, the data sets provided in this article can be extended using simulation-based analysis to extract spatial and temporal channel model parameters in urban cellular environments in the development of 5G channel propagation models.Peer reviewedFinal Published versio

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

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

Morphology and Properties of Zn-Al-TiO2 Composite on Mild Steel

The influence of TiO2 composite and dispersed pure Al particle on zinc alloy electrodeposited on mild steel was studied from chloride bath solution.Microstructural and mechanical properties of the alloy were investigated. The structure, surface morphology, and surface topography of the deposited alloys were characterized by scanning electron microscopy (SEM) and atomic force microscope (AFM).In addition, hardness of the coated alloys was measured. It was found that the obtained Zn-Al-TiO2 alloyexhibited more preferred surface morphology and mechanical strength compared tothe substrate. The result shows the existence of interaction between TiO2 compounds and zinc alloy particulate. It also exhibited well bright dominate zinc coating on steel surface

BPSK subcarrier intensity modulated free-space optical communications in atmospheric turbulence

Free-space optical communications (FSO) propagated over a clear atmosphere suffers from irradiance fluctuation caused by small but random atmospheric temperature fluctuations. This results in decreased signal-to-noise ratio (SNR) and consequently impaired performance. In this paper, the error performance of the FSO using a subcarrier intensity modulation (SIM) based on a binary phase shift keying (BPSK) scheme in a clear but turbulent atmosphere is presented. To evaluate the system error performance in turbulence regimes from weak to strong, the probability density function (pdf) of the received irradiance after traversing the atmosphere is modelled using the gamma-gamma distribution while the negative exponential distribution is used to model turbulence in the saturation region and beyond. The effect of turbulence induced irradiance fluctuation is mitigated using spatial diversity at the receiver. With reference to the single photodetector case, up to 12 dB gain in the electrical SNR is predicted with two direct detection PIN photodetectors in strong atmospheric turbulence

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

Enhanced vermiremediation of hydrocarbon contaminated land using biosurfactant: an integrated approach

Polycyclic aromatic hydrocarbon (PAH) contamination in soil continues to be one of the biggest environmental challenges because of the persistence and carcinogenicities of the contaminants. There is a need to seek updated environmental friendly ways to remediate these pollutants and vermiremediation provides a promising solution. Earthworms, because of their burrowing activity result in the accumulation of several lipophilic organic pollutants from their surrounding environment via the absorption of the contaminant through their body wall and also through intestinal uptake when soil passes through the gut. This makes them suitable model organisms in the remediation of PAHs from contaminated land. Biosurfactant produced by bacteria is known to aid mobility and bioavailability of contaminants which enhances bioremediation of hydrocarbons. The toxicity of these hydrocarbon compounds are yet to be fully understood. This research investigates the effect of biosurfactant on vermiremediation using anecic earthworm species (Lumbricus terrestris) and epigeic species (Eisenia hortensis) and studies the joint impact of PAHs and biosurfactant on the biochemical processes in both species by examining the monooxygenase activities (EROD and MROD activity of cytochrome P450 [CYP1A1 and CYP1A2]) and the antioxidase activity (GST activity). A 28-day experiment was conducted by exposing the two species of earthworms in soil spiked with selected 3, 4 and 5 ringed hydrocarbons [phenanthrene (PH), fluoranthene (FL) and benzo(a)pyrene (BAP) at 180 mg Kg-1 combined (60 mg Kg-1 each) and BAP alone at 60 mg Kg-1 under the same conditions. A time response relationship was established between the concentration of the three PAHs and length of exposure. In the presence of biosurfactant (0.1 g L-1), E. hortensis removed on average (mean ± stdev) 91% ± 5.2% PH, 70% ± 8.4% FL and 27% ± 4% BAP after 7 days whereas L. terrestris removed approximately 89% ± 0.5%, 67% ± 6.4% FL and 30% ± 1.4% BAP. These values were significantly higher than the control without the addition of biosurfactant (p = <0.05), E. hortensis removed only 26% ± 1.7% PH, 17% ± 6.2% FL and 8.4% ± 0.7% and L. terrestris 25% ± 4.5% PH 24% ± 8.8% FL and 6.4% ± 3% BAP. A one-way ANOVA analysis showed that there was a significant difference in the degradation of FL and PH in control soils in the presence of biosurfactant compared to the control soils without biosurfactant. Also, a significant difference between degradation of PH, FL and BAP by E. hortensis in the presence of biosurfactant, compared to its control (absence of biosurfactant, degradation by L. terrestris with biosurfactant was observed compared to the control (without biosurfactant). In the presence of biosurfactant (0.1 g L-1), the degradation was similar in both types of hydrocarbons with R-sq values of 85.6%, 85.9% and 94.1% for removal of PH, FL and BAP. This shows that the integration of vermiremediation and biosurfactant hold a promising approach to optimized and accelerated biodegradation of heavy molecular weight (HMW) PAHs in soil. Further investigation of enzymatic activities in a time response relationship over a 28-day period was conducted. Ultra-performance liquid chromatography (UPLC) analysis showed that both EROD and MROD activities were induced between days 0 and 2 of exposure. The level of increase in enzymatic activities were similar in both genera (between 2 and 2.5-fold higher in EROD and between 2 and 2.5-fold increase in MROD activity). Enzymatic activities decreased by day 7, with complete mortality of L. terrestris by day 28, indicating the presence of monooxygenases in earthworms further indicating the potential in degrading PAHs. Results obtained indicate that an epigeic species when used with biosurfactant performed slightly (≤5%) better because of their tolerance limits than anecic species which are more sensitive to several parameters such as temperature, moisture content, contaminants. Vermiremediation (using either species) was enhanced with biosurfactant. It is a promising, sustainable and quick technique to remediate PAH contaminants when compared to some of the other conventional approaches such as land filling, soil vitrification or incineration that could be expensive or pose some negative effects in the environment over a period of time. Overall the integrated approach of vermiremediation with biosurfactant completely removed 3 and 4 ringed hydrocarbons and 80% of 5-ringed hydrocarbons as stated earlier, where the application of rhamnolipid biosurfactant (0.1 mg Kg-1) posed no deleterious effect in either specie of earthworms, thus indicating that this could be a promising technique in remediating organic pollutants such as PAHs