Techniques for signal to noise ratio adaptation in infared optical wireless for optimisation of receiver performance

The challenge of creating a new environment of links for wireless infrared and optical local area networks (LANs) is driving new innovations in the design of optical transceivers. This thesis is concerned with a systematic approach to the design of receivers for indoor optical wireless communication. In particular, it is concerned with how to offer bandwidth adjustment capability in a receiver according to the dynamic service quality of the incoming signals. Another part of the discussion of the thesis is how one can properly choose the front-end preamplifier and biasing circuitry for the photodetector. Also, comparison is made between different types of amplifier, and the methods of bandwidth enhancement. The designs of six different techniques of integrating transimpedance amplifiers, with photodetectors to adapt an adjustable bandwidth control receiver are discussed. The proposed topologies provide an adjustable range of bandwidths for different frequency ranges, typically between 52Hz to 115MHz. The composite technique designs were used to incorporate into a system with an automatic gain control to study its effect, on an optical wireless receiver which had bandwidth adjustment and automatic gain adjustment. Theoretical analysis of noise performance for all the designed circuits is also presented. The theory and design of obstacles of indoor optical wireless receiver delivery, in addition to techniques for mitigating these effects, are discussed. This shows that infrared is a viable alternative to ratio for certain applications

Optimization of received power and SNR for an indoor attocells network in visible light communication

White LEDs Visible Light Communication (VLC) is applied in communication and illumination simultaneously. It provides unrestrained frequency spectrum and a large bandwidth that produces a higher transmission rate and speed in short-range communication. Also, VLC was considered as a promising alternative technology to the radio frequency in the next generation of communication systems. In this paper, the optical attocells configuration and LEDs distribution are proposed for optimizing the received power and Signal-to-Noise Ratio (SNR) in the Line of Sight (LOS) propagation link. Besides that, the trade-off between minimum SNR and received power are investigated. The simulation results showed that the proposed model can save 6.25% of the total transmitted power, and the optical received power versus semi-angle and field of view have with about increased 16.5% and 27.54% respectively. Moreover, the SNR also has 7.4% improvement. Hence, the proposed configuration model has improved the performance of VLC systems and has widen the window for future improvement

Performance evaluation of optical attocells configuration in an indoor visible light communication

Visible light communication VLC is deemed as futuristic technology applied for both illumination and data communication due to the low-cost energy consumption, long life expectancy, huge bandwidth, and high security compared to radio frequency RF. Uncovered area, minimum signal-to-noise ratio (SNR) and received power results from the non-uniform distribution of small base stations (i.e. Optical attocells) in the room. In this paper, the researchers propose a new LEDs distribution of five optical attocells configuration model in order to optimize the received power distribution and SNR at the center of the room for indoor VLC system. The optical attocells configuration in terms of received power to fill the uncovered area at the center of the room has been investigated. The simulation results showed that the proposed attocells configuration saved 24.9% of the transmitted power. Besides that, the whole room was covered uniformly. As a result, the received power and SNR are improved

Techniques for signal to noise ratio adaptation in infared optical wireless for optimisation of receiver performance

The challenge of creating a new environment of links for wireless infrared and optical local area networks CLANs) is driving new innovations in the design of optical transceivers. This thesis is concemed with a systematic approach to the design of receivers for indoor optical wireless communication. In particular, it is concemed with how to offer bandwidth adjustment capability in a receiver according to the dynamic service quality of the incoming signals. Another part of the discussion of the thesis is how one can properly choose the front-end preamplifier and biasing circuitry for the photodetector. Also, comparison is made between different types of amplifier, and the methods of bandwidth enhancement. The designs of six different teclmiques of integrating transimpedance amplifiers, with photo detectors to adapt an adjustable bandwidth control receiver are discussed. The proposed topologies provide an adjustable range of bandwidths for different frequency ranges, typically between 52Hz to 115MHz. The composite technique designs were used to incorporate into a system with an automatic gain control to study its effect, on an optical wireless receiver which had bandwidth adjustment and automatic gain adjustment. Theoretical analysis of noise perfom1ance for all the designed circuits is also presented. The theory and design of obstacles of indoor optical wireless receiver delivery, in addition to techniques for mitigating these effects, are discussed. This shows that infrared is a viable altemative to radio for certain applications

Enhancement of graphite functionality in renewable polymer composite properties

The preparation and characterization of composite thin films of renewable polymer graphite (PG) is disclosed. Thin films ~ 0.1 mm thick are prepared using a simple solution mixing with mass proportion of 2/1 (renewable monomer/ Methylene Diphenyl Diisocyanate, MDI), upon differ graphite content (PG0 , PG5 , PG10, PG15, PG20, PG25 and PG30) and drop casting at room temperature. The morphology-structure relations of renewable PG composites with respect to electrical conductivity were diagnosed using Optical microscope (OM), Fourier transform infra-red spectroscopy (FTIR) and Thermogravimetric analysis (TGA). The homogeneous random dispersion and strong interface between the graphite in the classical insulating renewable polymer matrix were observed. Thus resulting of enhancements in thermal stability with slight shift of decomposition temperature and better mechanical properties through the modulus and tensile strength increment up to ~440% and ~100% respectively. The result shows that it can simultaneously leads to renewable PG conductivity (σ) where the percolation threshold occurs at higher graphite content (PG20, PG25 and PG30) of 103 - 104 S/m. Thus, this non-petroleum based renewable polymer graphite composites have remarkably more to offer as conducting polymer composites material in multidisciplinary applications

Design of cyclic prefix characteristic-based OFDM system for WiMAX technology

Worldwide interoperability for microwave access (WiMAX) offers the wireless connectivity using orthogonal frequency division multiplexing (OFDM) modulation is a proficient wireless technology that capacities high-speed data transmission facilities. The existing WiMAX techniques have the problem of increase in inter-symbol interference (ISI) and bit error rate (BER) at reduced power spectrum that degrades the performance of WiMAX system due to high data rate transmission. The utilization of different adaptive modulation techniques seen as a potential solution to reduce the ISI and BER for high data rate transmission. In this paper, OFDM is adapted using advanced modulation technique for WiMAX system. The technique proposes the cyclic prefix (CP) is utilized that include supplementary bits at the stage of the transmitter. The proposed technique offers minimization of ISI and improvement in BER. It is defined that performance of the existing CP system is equated with the designed single cyclic prefix (SCP) and double cyclic prefix (DCP) and non-cyclic prefix (NCP). BER, probability of error, and power spectral density are utilized to analyse the performance of the designed system. The OFDM based SCP and DCP and NCP for WiMAX are demonstrated for modulation techniques such as; QPSK, BPSK, and QAM. It is determined that BPSK has the smallest BER when compared to QPSK, 16-QAM, and 64-QAM modulations. It is also demonstrated that QPSK is also very competent, however, it has a higher BER as compared to BPSK modulation. It is also observed that 16-QAM and 64-QAM are less efficient in terms of BER compared to QPSK and BPKS modulations. 64-QAM offers the high data rates, and due to high SNR ratio. The designed system is tested for under AWGN and Rayleigh fading channel, and effect power spectral density of signal to noise ratio on OFDM for rayleigh fading channel are demonstrated for SCP and DCP and NCP. It is determined that the OFDM transmitter with proposed DCP for random signals is efficiently reducing the BER and ISI for WiMAX system

The effect of haze attenuation on Free Space Optics Communication (FSO) at two wavelengths under Malaysia weather

Free Space Optical FSO is a promising optical technology that has a great chance of complementing the traditional wireless communication. It offers unlicensed, higher speed, broader, unlimited bandwidth and excellent security. However, the quality of FSO links is greatly affected by weather conditions and link distance. In the tropical regions, the quality of the FSO links is affected mainly by rain attenuation while the air quality is presumed to have little or no impact. However, a state of emergency has consecutively been declared in some part of Malaysia during the past three years due to high air pollution index (API). Since the range of FSO link is limited by air pollution, haze attenuation must be considered as one of the important factors in FSO link design. The aim of this paper is to provide an analysis and simulation of the FSO link with real data from Meteorological Malaysia department (MMD) on haze weather under two different wavelengths 850nm and 1550nm. This paper will discuss the different rate of attenuation operating in the medium between transmitter and receiver and their impact on the link margin calculation. In addition, it will evaluate the maximum distance link for wavelengths and consider the different visibility under the attenuated weather

A New All-Optical Signal Regeneration Technique for 10 GB/S DPSK Transmission System

The transmission of high power inside the optical fiber, produce amplitude noise, phase noise and other transmission impairments that degrade the performance of optical communication system. The signal regeneration techniques are used to mitigate these nonlinear impairments in the electrical or in the optical domain. All-optical signal regeneration techniques are one of the solutions to mitigate these nonlinear transmission impairments in the optical domain without converting the signal from optical to electrical domain. The existing techniques are not capable enough to attain the Bit Error Rate (BER) less than 10-10 with the power penalty less than – 9dBm. In this paper, a new all-optical signal regeneration technique is developed that mitigate amplitude and phase noises in the optical domain. The new optical signal regeneration technique is developed by combining the two existing technique one is 3R (Reshaping, Reamplification and Retiming) regeneration and other is Phase Sensitive Amplification (PSA). The 10Gb/s Differential Phase shift Keying (DPSK) noisy transmission system is used to verify the features of developed technique. The developed technique successfully mitigates the nonlinear impairments from the noisy DPSK system with significant improvement in BER at low power penalty with the additional feature of high Q-factor and an eye open response for the regenerated signal. It is determined that BER of 10-12 is achieved at the power penalty of -14 dBm with Q-factor of 42 and an eye opened response. The developed technique in the DPSK system is realized using commercial software package Optisystem. The designed technique will be helpful to enhance the performance existing high-speed optical communication by achieving the minimum BER at low power penalty

Quantitative infrared thermography resolved leakage current problem in cathodic protection system

Leakage current problem can happen in Cathodic Protection (CP) system installation. It could affect the performance of underground facilities such as piping, building structure, and earthing system. Worse can happen is rapid corrosion where disturbance to plant operation plus expensive maintenance cost. Occasionally, if it seems, tracing its root cause could be tedious. The traditional method called line current measurement is still valid effective. It involves isolating one by one of the affected underground structures. The recent methods are Close Interval Potential Survey and Pipeline Current Mapper were better and faster. On top of the mentioned method, there is a need to enhance further by synthesizing with the latest visual methods. Therefore, this paper describes research works on Infrared Thermography Quantitative (IRTQ) method as resolution of leakage current problem in CP system. The scope of study merely focuses on tracing the root cause of leakage current occurring at the CP system lube base oil plant. The results of experiment adherence to the hypothesis drawn. Consequently, res

Comparison of Cap and QAM-DMT Modulation Format for In-Home Network Environment

Carrierless amplitude phase (CAP) modulation format has appeared as a potential advanced modulation format candidate for spectrally efficient single-carrier modulation type due to less complexity and has competitive performance. In this paper, the comparison between 2D-CAP-4 and 4-QAM-DMT modulation format over 3 km single mode fiber (SMF) transmission link using 1310 nm vertical cavity surface emitting laser (VCSEL) has been performed for inhome network environment. The net bit rates of 625 Mb/s and 454.6 Mb/s are achieved for 2D-CAP-4 and 4-QAM-DMT, respectively. Spectral efficiencies of 1.89 b/s/Hz for 2D-CAP-4 and 1.43 b/s/Hz for 4-QAM-DMT are reported. It is observed that 2D-CAP-4 outperforms 4-QAM-DMT with 1.14 dB better receiver sensitivity. These results indicate that the privilege properties of CAP modulation format can be an attractive prospect for in-home network environment