- Prof. Ghassemlooy: Fellow, SOA, Fellow, IET, SM IEEEedit
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In this paper, we study the design aspects of an indoor visible light positioning (VLP) system that uses an artificial neural network (ANN) for positioning estimation by considering a multipath channel. Previous results usually rely on... more
In this paper, we study the design aspects of an indoor visible light positioning (VLP) system that uses an artificial neural network (ANN) for positioning estimation by considering a multipath channel. Previous results usually rely on the simplistic line of sight model with limited validity. The study considers the influence of noise as a performance indicator for the comparison between different design approaches. Three different ANN algorithms are considered, including Levenberg–Marquardt, Bayesian regularization, and scaled conjugate gradient algorithms, to minimize the positioning error (εp) in the VLP system. The ANN design is optimized based on the number of neurons in the hidden layers, the number of training epochs, and the size of the training set. It is shown that, the ANN with Bayesian regularization outperforms the traditional received signal strength (RSS) technique using the non-linear least square estimation for all values of signal to noise ratio (SNR). Furthermore,...
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This paper present simulation-based results on the impact of transmitter (Tx) position and orientation uncertainty on the accuracy of the visible light positioning (VLP) system based on the received signal strength (RSS). There are... more
This paper present simulation-based results on the impact of transmitter (Tx) position and orientation uncertainty on the accuracy of the visible light positioning (VLP) system based on the received signal strength (RSS). There are several constraining factors for RSS-based algorithms, particularly due to multipath channel characteristics and set-up uncertainties. The impact of Tx uncertainties on positioning error performance is studied, assuming a statistical modelling of the uncertainties. Simulation results show that the Tx uncertainties have a severe impact on the positioning error, which can be leveraged through the usage of more transmitters. Concerning a smaller Tx’s position uncertainty of 5 cm, the average positioning errors are 23.3, 15.1, and 13.2 cm with the standard deviation values of 6.4, 4.1, and 2.7 cm for 4-, 9-, and 16-Tx cases, respectively. While for a smaller Tx’ orientation uncertainty of 5°, the average positioning errors are 31.9, 20.6, and 17 cm with stand...
Research Interests: Computer Science, Analytical Chemistry, Medicine, RSS, Sensors, and 10 moreStandard Deviation, INDOOR POSITIONING SYSTEM, Vlc, Transmitter, Electrical And Electronic Engineering, Measurement Uncertainty, Positioning System, Multipath Propagation, Received Signal Strength, and visible light positioning
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The accuracy of the received signal strength-based visible light positioning (VLP) system in indoor applications is constrained by the tilt angles of transmitters (Txs) and receivers as well as multipath reflections. In this paper, for... more
The accuracy of the received signal strength-based visible light positioning (VLP) system in indoor applications is constrained by the tilt angles of transmitters (Txs) and receivers as well as multipath reflections. In this paper, for the first time, we show that tilting the Tx can be beneficial in VLP systems considering both line of sight (LoS) and non-line of sight transmission paths. With the Txs oriented towards the center of the receiving plane (i.e., the pointing center F), the received power level is maximized due to the LoS components on F. We also show that the proposed scheme offers a significant accuracy improvement of up to ~66% compared with a typical non-tilted Tx VLP at a dedicated location within a room using a low complex linear least square algorithm with polynomial regression. The effect of tilting the Tx on the lighting uniformity is also investigated and results proved that the uniformity achieved complies with the European Standard EN 12464-1. Furthermore, we...
Research Interests: Computer Science, Artificial Intelligence, Analytical Chemistry, Computer Vision, Medicine, and 12 moreSensors, Visible Light Communication, INDOOR POSITIONING SYSTEM, Polynomial Regression, H, Artificial Neural Network, Electrical And Electronic Engineering, Positioning System, Light Emitting Diode, Multipath Propagation, Received Signal Strength, and visible light positioning
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Research Interests: Computer Science, Physics, Optics, Modulation, Free Space Optics, and 13 moreFREE SPACE OPTICAL COMMUNICATION, IEEE, Atmospheric Turbulence, Bit Error Rate, Polarisation, Communication Channels, MRC, Maximum Ratio Combining, Digital signal, Signal to Noise Ratio, H, Spatial Diversity, and Amplitude shift keying
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This paper presents a real-time 106 Mbit/s visible light communication (VLC) system using only non-return-to-zero on-off keying (OOK-NRZ) modulation and general lighting LED. With a pre-emphasis module based LED driver, the 3-dB... more
This paper presents a real-time 106 Mbit/s visible light communication (VLC) system using only non-return-to-zero on-off keying (OOK-NRZ) modulation and general lighting LED. With a pre-emphasis module based LED driver, the 3-dB modulation bandwidth of VLC link is extended from 4 to 106 MHz. Given the BER upper Limit was 1.3 × 10−3, the highest bit rates achieved through the designed system were 106 and 98 Mbit/s at the distances of 60 and 70 cm, respectively.
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Research Interests: Engineering, Cognitive Science, Computer Science, Distributed Computing, Turbulence, and 14 moreFree Space Optics, FREE SPACE OPTICAL COMMUNICATION, Atmospheric Turbulence, Long Range, Outage Probability, Bit error probability, Exponential distribution, H, F, Spatial Diversity, Exponential Function, PSK, Access Network, and Phase shift keying
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This article presents a study of digital pulse interval modulation (DPIM) for optical wireless communications using intensity modulation with direct detection. The DPIM code properties are discussed, and expressions for the transmission... more
This article presents a study of digital pulse interval modulation (DPIM) for optical wireless communications using intensity modulation with direct detection. The DPIM code properties are discussed, and expressions for the transmission capacity, power spectrum, and error probability are presented. We show that for a given number of bits per symbol, DPIM has a higher transmission capacity, a similar spectral
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A novel ultra-fast optical router using time-slot switching ... CK Yow, R. McDougall, YJ Chai, RV Penty, I. H, White Centre for Photonic Systems, Engineering Department, Cambridge University, William Gates Building, 15 JJ Thomson Avenue,... more
A novel ultra-fast optical router using time-slot switching ... CK Yow, R. McDougall, YJ Chai, RV Penty, I. H, White Centre for Photonic Systems, Engineering Department, Cambridge University, William Gates Building, 15 JJ Thomson Avenue, Cambridge, CB3 0FD, U. K ...
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International audienceThe growing demand for high speed indoor wireless connectivity is among the driving forces for data transmission based on visible-light communications (VLC). For relatively large-space indoor scenarios, the... more
International audienceThe growing demand for high speed indoor wireless connectivity is among the driving forces for data transmission based on visible-light communications (VLC). For relatively large-space indoor scenarios, the development of appropriate spectrally-efficient multiple-access (MA) techniques enables efficient handling of multiple users, in particular, in dealing with the limited modulation bandwidth of the light-emitting diodes. In this paper, we present a comparative study between different MA techniques proposed in the recent literature for VLC networks. The most appropriate schemes for large-scale network deployments are further investigated in different scenarios to contrast their performance in terms of the achievable throughput
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Turbulence is due to the random variations of the refractive index of the medium (in this case water), which leads to fluctuation or fading of the received light intensity. In wireless communications including underwater optical wireless... more
Turbulence is due to the random variations of the refractive index of the medium (in this case water), which leads to fluctuation or fading of the received light intensity. In wireless communications including underwater optical wireless communications the link performance is greatly affected. In this paper, we investigate the effect of turbulence on the probability density function (PDF) of the received light intensity. We show that lognormal and negative exponential distributions are fitted well with the PDFs of the received light intensity in weak-to-strong and saturated turbulence regimes. The goodness of fit test is performed to validate the conformity of these two distributions with the simulation results. Furthermore, we investigate the effect of the divergence angle of the Gaussian beam transmitter, the receiver’s aperture diameter and field of view on the scintillation index.
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The wireless information carrier shift from the radio frequencies to optical frequencies has been studied in increasing detail since the invention of the laser in the 1960s [...]
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Artificial neural network (ANN) can be an attractive alternative for adaptive equalization especially while channel is nonlinear or non-stationary. Pulse position modulation (PPM) requires the least average optical power compared to other... more
Artificial neural network (ANN) can be an attractive alternative for adaptive equalization especially while channel is nonlinear or non-stationary. Pulse position modulation (PPM) requires the least average optical power compared to other modulation schemes in line-of-sight links but suffer severely in diffused links. The performance of PPM in a diffused channel can be improved by using different equalization techniques. In
Research Interests: Engineering, Computer Science, Optical Fiber Communications, Nonlinear Optics, Channel Coding, and 15 moreNeural Networks, Optical Communication, Neural Network, Artificial Neural Networks, Digital Modulation, Optical computing, Decoding, Fuzzy Adaptive Equalizer, Adaptive Equalization, H, Artificial Neural Network, Optical Wireless, Neural nets, Line of sight, and Adaptive Equalizer
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ABSTRACT In this paper we present the experimental work on object detection in the Smartphone visible light communications (SVLC) system. In SVLC, the Smartphone emits encoded images using its panel light under different conditions (link... more
ABSTRACT In this paper we present the experimental work on object detection in the Smartphone visible light communications (SVLC) system. In SVLC, the Smartphone emits encoded images using its panel light under different conditions (link range and angles) and the transmitted data is captured by a receiving phone. The captured image is processed using the Speeded Up Robust Features (SURF) technique, which enables the frame detection and subsequently bit stream recovery. The success rate of the bit stream transmission is measured for the above test conditions. The obtained results show that 93% of successful data recovery is achieved under the normal user's working environment. In addition tests carried out also show the possibility of fast data rate communications.
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Research Interests: Computer Science, Optics, Medical Imaging, Fiber Optics, Digital Signal Processing, and 15 morePhotonics, Optical Communication, Neural Network, Communication System, Noise reduction, Optical, Light, Optical physics, Discrete wavelet transform, Optical Filters, Discrete Wavelet Transforms, Artificial Neural Network, Electrical And Electronic Engineering, Optical Wireless, and Neural nets
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Abstract In this letter the performance of a free space optical (FSO) communication link in the presence of fog is experimentally investigated in an indoor environment. A dedicated indoor atmospheric chamber, replicating the outdoor... more
Abstract In this letter the performance of a free space optical (FSO) communication link in the presence of fog is experimentally investigated in an indoor environment. A dedicated indoor atmospheric chamber, replicating the outdoor environment, is being used to evaluate the FSO link performance under the fog condition. Theoretical analysis supported by the experimental evaluation has been carried out for the intensity modulation/direct detection on-off keying non-return-to-zero (OOK-NRZ), OOK return-to-zero (OOK-RZ) and four pulse ...
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There is a growing demand for high mobility and ultrafast internet/data services which drives the motivation for free space optical (FSO) communications for high speed trains. Here we present an FSO link for the ground-to-train... more
There is a growing demand for high mobility and ultrafast internet/data services which drives the motivation for free space optical (FSO) communications for high speed trains. Here we present an FSO link for the ground-to-train communications, which consists of optical transceivers positioned alongside the track and on the roof of the train. When the train moves at a high speed, the airwave induced turbulence degrades the FSO link performance. In this paper the effect of turbulence is experimentally investigated and ...
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Abstract: In this paper we evaluate the performance of digital pulse interval modulation (DPIM) with convolutional coding for different values of bit resolution and different sizes of guard bands. We show that convolutional coding is an... more
Abstract: In this paper we evaluate the performance of digital pulse interval modulation (DPIM) with convolutional coding for different values of bit resolution and different sizes of guard bands. We show that convolutional coding is an effective method of improving the error performance of DPIM over optical wireless links. The convolutional coded DPIM with a guard band of 2 slots has the advantage of fixed header pattern so that decoding is simple with no need for Viterbi decoding. It also achieves a code gain of more than 4 dB ...
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The paper reports the development and experimental results of our laboratory for atmospheric turbulence and variable fog conditions in free space optics (FSO) communications link with different modulation techniques. The controlled fog is... more
The paper reports the development and experimental results of our laboratory for atmospheric turbulence and variable fog conditions in free space optics (FSO) communications link with different modulation techniques. The controlled fog is generated inside a glass chamber of 5.5 m ...
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ABSTRACT The cursive and ligature nature of the Arabic language make the segmentation of words into individual characters a dif-ficult task. Despite attempts to apply methods for cursive Latin and other languages to Arabic, it is... more
ABSTRACT The cursive and ligature nature of the Arabic language make the segmentation of words into individual characters a dif-ficult task. Despite attempts to apply methods for cursive Latin and other languages to Arabic, it is generally insuffi-cient to segment Arabic text. This paper proposes a new seg-mentation algorithm for handwritten Arabic text and the main idea consist of segmenting the word into sub-words and then computing the baseline of each sub-word. Using the descen-ders of sub-words of each sub-word and the baseline, can-didate points are then calculated using a vertical projection. The algorithm has been tested using 800 handwritten Arabic words taken from IFN/ENIT database and a comparison made against against some existing methods with promising results obtained.