Enhanced carrierless amplitude and phase modulation for optical communication systems

This thesis develops and investigates enhanced techniques for carrierless amplitude and phase modulation (CAP) in optical communication systems. The CAP scheme is studied as the physical layer modulation technique due to its implementation simplicity and versatility, that enables its implementation as a single carrier (CAP) or multi-carrier technique (m-CAP). The effect of timing jitter on the error performance of CAP is first investigated. The investigation indicates that synchronization is a critical requirement for CAP receiver and as a result, a novel low-complexity synchronization algorithm is developed with experimental demonstration for CAP-based visible light communication (VLC) systems. To further reduce the overall link complexity, a fractionally-spaced equalizer (FSE) is considered to mitigate the effects of inter-symbol interference (ISI) and timing jitter. The FSE implementation, which eliminates the need for a separate synchronization block, is shown through simulation and VLC experimental demonstration to outperform symbol-spaced equalizers (SSE) that are reported in literature for CAP-based VLC systems. Furthermore, in this thesis, spectrally-efficient index modulation techniques are developed for CAP. The proposed techniques can be divided into two broad groups, namely spatial index CAP (S-CAP) and subband index CAP (SI-CAP). The proposed spatial index techniques leverage the fact that in VLC, multiple optical sources are often required. The spatial CAP (S-CAP) transmits CAP signal through one of Nt available LEDs. It is developed to reduce equalization requirement and improve the spectral efficiency of the conventional CAP. In addition to the bits transmitted through the CAP symbol, the S-CAP encodes additional bits on the indexing/spatial location of the LEDs. The generalised S-CAP (GS-CAP) is further developed to relax the S-CAP limitation of using a single LED per symbol duration. In addition to the S-CAP scheme, multiple-input multiple-output (MIMO) techniques of repetitive-coded CAP (RC-CAP) and spatial multiplexing CAP (SMux-CAP) are investigated for CAP. Low-complexity detectors are also developed for the MIMO schemes. A key challenge of the MIMO schemes is that they suffer power penalty when channel gains are similar, which occur when the optical sources are closely located. The use of multiple receivers and power factor imbalance (PFI) techniques are proposed to mitigate this power penalty. The techniques result in significant improvement in the power efficiency of the MIMO schemes and ensure that the spectral efficiency gain is obtained with little power penalty. Finally, subband index CAP (SI-CAP) is developed to improve the spectral efficiency of m-CAP and reduce its peak-to-average power ratio (PAPR). The SI-CAP encodes additional information bits on the selection of ‘active’ subbands of m-CAP and only modulate data symbols on these ‘active’ subbands. The error performance of the proposed SI-CAP is evaluated analytically and verified with computer-based simulations. The SI-CAP technique is also experimented for both VLC and step-index plastic optical fibre (SI-POF) communication links. The experimental results show that for a fixed power efficiency, SI-CAP achieves higher data rate compared tom-CAP. For example, at a representative bit error rate (BER) of 10-5, the SI-CAP achieves a data rate and power efficiency gain of 26:5 Mb/s and 2:5 dB, respectively when compared to m-CAP. In addition, an enhanced SI-CAP (eSI-CAP) is developed to address the complexity that arises in SI-CAP at higher modulation order. The results of the experimental demonstrations in VLC and 10 m SI-POF link shows that when compared with m-CAP, eSI-CAP consistently yields a data rate improvement of between 7% and 13% for varying values of the SNR

Prediction of Superconducting Transition Temperatures for Fe- Based Superconductors using Support Vector Machine

Quench for materials that can persistently carry electrical current without loss of power is confined to low temperatures. The future dream of room temperature superconductors is hampered by the absence of unique theory that fully explains superconductivity as well as high cost of the equipment involved in the characterization of the potential samples. Support vector machine (SVM) is hereby proposed to predict the superconducting transition temperature of any family of iron-based superconductors at ambient pressure using lattice parameters of the samples. Accuracy of over 99% obtained in our developed model is not only creating an efficient and low cost way of predicting transition temperature but also  makes lattice parameter a premise through which full understanding of superconductivity can be grown. Keywords: Iron-based superconductor, Support vector machine, correlation coefficient and superconducting transition temperatur

GPT Models in Construction Industry: Opportunities, Limitations, and a Use Case Validation

Large Language Models(LLMs) trained on large data sets came into prominence in 2018 after Google introduced BERT. Subsequently, different LLMs such as GPT models from OpenAI have been released. These models perform well on diverse tasks and have been gaining widespread applications in fields such as business and education. However, little is known about the opportunities and challenges of using LLMs in the construction industry. Thus, this study aims to assess GPT models in the construction industry. A critical review, expert discussion and case study validation are employed to achieve the study objectives. The findings revealed opportunities for GPT models throughout the project lifecycle. The challenges of leveraging GPT models are highlighted and a use case prototype is developed for materials selection and optimization. The findings of the study would be of benefit to researchers, practitioners and stakeholders, as it presents research vistas for LLMs in the construction industry.Comment: 58 pages, 20 figure

Experimental demonstration of subband index techniques for m-CAP in short-range SI-POF links

In this letter, novel spectrally efficient subband index (SI) techniques have been developed for multiband carrierless amplitude and phase modulation ( m -CAP). The SI techniques transmit additional information bit on the index of the conventional m -CAP subbands. Experimental demonstrations are performed in a short-range optical data link using step-index plastic optical fiber. The demonstrations show that the proposed techniques enable flexibility in design and significantly improve the power/spectral efficiency of the conventional m -CAP

Subband index carrierless amplitude and phase modulation for optical communications

Subband index carrierless amplitude and phase modulation (SI-CAP) is proposed and investigated in this paper to improve the performance of multi-band CAP (m -CAP). The bit-error-rate (BER) analysis of the proposed SI-CAP is derived and verified through computer simulations. A detection scheme is also developed for SI-CAP, which achieves maximum likelihood performance at a significantly lower complexity. In addition, an experimental demonstration of the proposed SI-CAP is carried out for optical communication systems. Furthermore, an adaptive equalization technique is implemented to further enhance the performance gain of SI-CAP. It is shown that for the same order of complexity, the SI-CAP exhibits higher spectral and energy efficiency in comparison to m-CAP. Therefore, the performance gain of SI-CAP along with its design flexibility make it a suitable candidate for optical communication systems

MIMO techniques for carrierless amplitude and phase modulation in visible light communication

In this letter, multiple-input multiple-output (MIMO) techniques are proposed to improve the spectral efficiency and bit error rate (BER) performance of the conventional carrierless amplitude and phase modulation (CAP) in visible light communication. Analytic frameworks for both multiplexing and diversity MIMO techniques are developed for CAP. The analytical expressions in line-of-sight (LOS) propagation are validated via simulation. A precoding technique is further applied to improve the power efficiency of the multiplexing scheme resulting in a signal-to-noise ratio (SNR) gain of 28.5 dB

The ameliorative effects of glutathione on biochemical indices of goats exposed to lead

Poisoning with lead is rampant in goats and it is a crucial threat to their economic and nutritional worth. Lead exerts deleterious impacts on the bodies of human beings and animals. Glutathione possesses antioxidant and decontamination characteristics in living systems. It is opined that glutathione might abrogate lead toxicity through its beneficial mechanisms of action. The purpose of this study was to find out the influence of glutathione on biochemical indices in goats exposed to lead. Twenty bucks were included in the research and were distributed into five groups (four animals/group) as follows: Control (CONT group, administered with distilled water); Lead (10 mg kg-1) group; Lead (10 mg kg-1)+Glutathione (50 mg kg-1) group; Lead (10 mg kg-1)+Glutathione (100 mg kg-1) group and Lead (10 mg kg-1)+Glutathione (200 mg kg-1) group. The animals received lead and glutathione daily per os for 21 days. The biochemical indices were estimated with a Clinical Chemistry Analyzer. Lead evoked considerable elevations in the activities of some of the serum enzymes and levels of urea, triglycerides and thyroid stimulating hormone. Also, the levels of albumin, triiodothyronine and thyroxine were decreased appreciably in the lead group. Glutathione ameliorated the undesirable effects of lead in the goats. The advantageous effects of glutathione in this research may be attributed to its bioprotective impacts. Therefore glutathione may be a valuable agent for the amelioration of lead intoxication in goats