Intra-Sector Firm Performance and its Determinants in the UK Construction Industry

This thesis is a detailed quantitative investigation of intra-sector firm performance in the UK construction industry. Using the value-based model and creating a conceptual tool of assessment from it comprising nine determinants, the research applies this tool to the industry. Over two decades of firm performance data in the key sectors are analysed to answer the firm’s performance question. By doing so, the thesis for the first time combines the disciplines of strategy, economics and finance to analyse the intrasector firm performance question in UK construction. A panel-based ordinary least squares (OLS) regression is the main approach. However, corrections and adjustments are made for a range of likely econometric issues including heteroscedasticity, autocorrelation, multicollinearity and cointegration. A suite of five different advanced regressions including GLS random effects and maximum likelihood estimations are implemented to validate and corroborate the OLS results. In addition, three different regressions are performed in the sample simultaneously namely in the overall industry, the three key sectors in it and in a time-based pre- and post-credit crisis splicing. Robust evidence is found for each of the nine determinants and their varied influences on profits in the UK construction industry. Among the important findings here are: evidence for a liquidity-orientated business model in large tracts of the industry; a negative leverage impact on profits only among building sector firms; and a purely positive profits function among civil engineering firms. Based on these findings, firm managers in each sector of the industry are given specific recommendations including: to avoid debt in the buildings sector; to invest systematically in technology and capital assets in the civil engineering sector; and to focus on cost leadership in the specialist trades sector. The analysis also yields important policy insights for regulators and policy think tanks. Noteworthy here are tax-based incentives for inventory management in all sectors of the industry, a technology development institute for the firms in the industry and sector-specific regulatory guidelines for the firms in the buildings sector. The thesis expands the repertoire of creative solutions for the difficult intra-sector firm performance questions of this industry

DC biased input stage with differential photocurrent sensing for VLC front-ends

The reverse bias voltage across the PIN photodiode is essential for the photodiode to operate in the photoconductive mode. This paper presents an input bias stage with differential photocurrent sensing for VLC front-ends. The bias voltage is provided from within the transimpedance amplifier’s (TIA) circuit eliminating the need of external bias voltage. The amount of bias voltage could be optimised according to the photodiode required sensitivity and capacitance. The differential configuration makes the TIA immune to any common mode noise. The proposed method is applied to a hypothetical TIA and results are compared with single ended structure. Simulation results showed that using this approach it is possible to achieve a transimpedance gain of 120 dBΩ over a maximum bandwidth of 14.5 MHz with a common mode rejection ratio of 61 dB while the circuit provides a controlled bias voltage of up to 6 V across the PIN photodiode eliminating the need for external bias voltage source

Design and implementation of a tuned Analog Front-End for extending VLC transmission range

Visible Light Communications (VLC) is currently considered one of the most promising Optical Wireless Communications (OWC) for commercial applications, due to the widespread deployment of Light Emitting Diodes (LEDs) for energy efficiency, durability and low cost. With the ability to provide several THz of bandwidth, VLC is expected to co-exist with legacy and future Radio Frequency (RF) media as a reliable solution to the rapid demand of high-speed wireless communication. Most current research on VLC is focused on achieving high data rates over short distances through various types of modulation schemes. Limited research work investigates long range VLC employing high power LEDs, while none of them employed analog filter design in the receiver side while using low power LED for transmission. This thesis work explores the design and easy implementation of a low cost visible light communication system for long-range applications. The main idea of the research is increasing the receiver sensitivity by employing an analog filtering stage within the receiver front-end while the transmission is carried out using a low-power commercial white light LED, enabling the system to provide both illumination and digital communication. The proposed VLC front-end employs a high gain, high Quality (Q) factor band pass filter with the Multiple Feed Back (MFB) topology, which operates at a defined centre frequency range. The proposed MFB active filter uses the gain of the operational amplifier at the defined transmission frequency maximizing the gain and therefore extending the transmission range. The band pass filter behaves as a resonant circuit which detects the desired signal at the transmitting centre frequency and rejects unwanted frequencies including ambient light noise frequencies. Two modulations schemes were used through this work On Off Keying (OOK) with Manchester encoding, and Pulse Width Modulation (PWM). To evaluate the viability of the proposed system several prototypes were designed, implemented and tested. Experimental results demonstrated that by employing the proposed front-end the transmission range could be extended up to 2m distance by Manchester coding and up to 5m by using PWM. Moreover, the proposed system showed robustness against ambient light interference under the indoor scenario. Another Arduino prototype was designed and implemented to test the ability of the system to transmit serial data between two PCs. Experimental results demonstrated that the filtering stage is able to improve the receiver sensitivity and extend the transmission distance however, only data rates below 1 kbps were read by the receiver Arduino due to low procession speed of the Arduino boards

Application of an Infinite Gain Multiple Feedback Filter in VLC Link Range Extension

This paper presents a visible light communication (VLC) link range extension, achieved by establishing a VLC system using simple, low-cost, and reliable electronic circuitry, and employing a design of a highly resonant frequency selective active band pass filter (infinite gain multiple feedback filter) at the receiver section of the system. The filter was designed for a specific center (resonant) frequency with high Quality factor and gain. An outline of the relationship between Signal-to-Noise ratio (SNR) and transmission distance for three different center frequencies was presented. Results show that by utilizing an IGMF filter at the receiver, a signal-to-noise ratio above 10dB at a distance beyond 1.5 meters can be achieved without any form of lensing at either the transmitter or receiver

Design and Implementation of a Long Range Indoor VLC System using PWM

Visible Light Communications (VLC) is currently considered one of the most promising Optical Wireless Communications (OWC) for commercial applications, due to the widespread deployment of Light Emitting Diodes (LEDs) for energy efficiency, durability and low cost. With the ability to provide several THz of bandwidth, VLC is expected to co-exist with legacy and future Radio Frequency (RF) media as a reliable solution to the rapid demand of high-speed wireless communication. VLC is challenged by two main drawbacks: ambient light interference and the transmission range. To overcome these drawbacks, we propose a tuned VLC Analog Front-End (AFE) using simple and low-cost electronic circuity. The proposed VLC receiver architecture consists of a transimpedance amplifier, a fourth order Multiple Feed Back (MFB) band pass filter and a comparator. Experimental results demonstrated that by employing the proposed front-end the VLC transmission range could be extended up to 4.7m by using Pulse Width Modulation (PWM). Moreover, the proposed system showed robustness against ambient light interference under the indoor scenario