Data transport over optical fibre for ska using advanced modulation flexible spectrum technology
- Authors: Dlamini, Phumla Patience
- Date: 2020
- Subjects: Fiber optics
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/50666 , vital:42329
- Description: Flexible Spectrum Dense Wavelength Division Multiplexed (DWDM) optical fibre networks are next-generation technology for handling extremely high data rates of the kind produced by MeerKAT and SKA.We optimise the flexible spectrum for real-time dynamic channel wavelength assignment, to ensure optimum network performance. We needed to identify and develop novel hardware and dynamic algorithms for these networks to function optimally to perform critical tasks. Such tasks include wavelength assignment, signal routing, network restoration and network protection. The antennas of the Square Kilometre Array (SKA) network connect to the correlator and data processor in a simple point-to-point fixed configuration. The connection of the astronomer users to the data processor, however, requires a more complex network architecture. This is because the network has users scattered around South Africa, Africa and the whole world. This calls for upgrade of the classical fixed wavelength spectrum grids, to flexible spectrum grid that has improved capacity, reliable, simple and cost-effectiveness through sharing of network infrastructure. The exponential growth of data traffic in current optical communication networks requires higher capacity for the bandwidth demands at a reduced cost per bit. All-optical signal processing is a promising technique to improve network resource utilisation and resolve wavelength contention associated with the flexible spectrum. Flexible Spectrum Dense Wavelength Division Multiplexed (DWDM) optical fibre networks are next-generation technology for handling extremely high data rates of the kind produced by MeerKAT and SKA. Each DWDM channel is capable of 10 Gbps transmission rate, which is sliceable into finer flexible grid 12.5 GHz granularity to offer the network elastic spectrum and channel spacing capable of signal routing and wavelength switching for the scalability of aggregate bandwidth. The variable-sized portions of the flexible spectrum assignment to end users at different speeds depend on bandwidth demand, allowing efficient utilisation of the spectrum resources. The entire bandwidth of dynamic optical connections must be contiguously allocated. However, there is an introduction of spectrum fragmentation due to spectrum contiguity related to the optical channels having different width. Thus large traffic demands are likely to experience blocking regardless of available bandwidth. To minimise the congestion and cost-effectively obtain high performance, the optical network must be reconfigurable, achievable by adding wavelength as an extra degree of freedom for effectiveness. This can introduce colourless, directionless and contentionless reconfigurability to route individual wavelengths from fibre to fibre across multiple nodes to avoid wavelength blocking/collisions, increasing the flexibility and capacity of a network. For these networks to function optimally, novel hardware and dynamic algorithms identification and development is a critical task. Such tasks include wavelength assignment, signal routing, network restoration and network protection. In this work, we for the first time to our knowledge proposed a spectrum defragmentation technique through reallocation of the central frequency of the optical transmitter, to increase the probability of finding a sufficient continuous spectrum. This is to improve network resource utilisation, capacity and resolve wavelength contention associated with a flexible spectrum in optical communication networks. The following chapter provides details on a flexible spectrum in optical fibre networks utilising DWDM, optimising transmitter-receivers, advanced modulation formats, coherent detection, reconfigurable optical add and drop multiplexer (ROADM) technology to implement hardware and middleware platforms which address growing bandwidth demands for scalability, flexibility and cost-efficiency. A major attribute is tunable lasers, an essential component for future flexible spectrum with application to wavelength switching, routing, wavelength conversion and ROADM for the multi-node optical network through spectrum flexibility and cost-effective sharing of fibre links, transmitters and receivers. Spectrum slicing into fine granular sub-carriers and assigning several frequency slots to accommodate diverse traffic demands is a viable approach. This work experimentally presents a spectral efficient technique for bandwidth variability, wavelength allocation, routing, defragmentation and wavelength selective switches in the nodes of a network, capable of removing the fixed grid spacing using low cost, high bandwidth, power-efficient and wavelength-tunable vertical-cavity surface-emitting laser (VCSEL) transmitter directly modulated with 10 Gbps data. This to ensure that majority of the spectrum utilisation at finer channel spacing, wastage of the spectrum resource as caused by the wavelength continuity constraint reduction and it improves bandwidth utilisation. The technique is flexible in terms of modulation formats and accommodates various formats with spectrally continuous channels, fulfilling the future bandwidth demands with transmissions beyond 100 Gbps per channel while maintaining spectral efficiency.
- Full Text:
- Date Issued: 2020
- Authors: Dlamini, Phumla Patience
- Date: 2020
- Subjects: Fiber optics
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/50666 , vital:42329
- Description: Flexible Spectrum Dense Wavelength Division Multiplexed (DWDM) optical fibre networks are next-generation technology for handling extremely high data rates of the kind produced by MeerKAT and SKA.We optimise the flexible spectrum for real-time dynamic channel wavelength assignment, to ensure optimum network performance. We needed to identify and develop novel hardware and dynamic algorithms for these networks to function optimally to perform critical tasks. Such tasks include wavelength assignment, signal routing, network restoration and network protection. The antennas of the Square Kilometre Array (SKA) network connect to the correlator and data processor in a simple point-to-point fixed configuration. The connection of the astronomer users to the data processor, however, requires a more complex network architecture. This is because the network has users scattered around South Africa, Africa and the whole world. This calls for upgrade of the classical fixed wavelength spectrum grids, to flexible spectrum grid that has improved capacity, reliable, simple and cost-effectiveness through sharing of network infrastructure. The exponential growth of data traffic in current optical communication networks requires higher capacity for the bandwidth demands at a reduced cost per bit. All-optical signal processing is a promising technique to improve network resource utilisation and resolve wavelength contention associated with the flexible spectrum. Flexible Spectrum Dense Wavelength Division Multiplexed (DWDM) optical fibre networks are next-generation technology for handling extremely high data rates of the kind produced by MeerKAT and SKA. Each DWDM channel is capable of 10 Gbps transmission rate, which is sliceable into finer flexible grid 12.5 GHz granularity to offer the network elastic spectrum and channel spacing capable of signal routing and wavelength switching for the scalability of aggregate bandwidth. The variable-sized portions of the flexible spectrum assignment to end users at different speeds depend on bandwidth demand, allowing efficient utilisation of the spectrum resources. The entire bandwidth of dynamic optical connections must be contiguously allocated. However, there is an introduction of spectrum fragmentation due to spectrum contiguity related to the optical channels having different width. Thus large traffic demands are likely to experience blocking regardless of available bandwidth. To minimise the congestion and cost-effectively obtain high performance, the optical network must be reconfigurable, achievable by adding wavelength as an extra degree of freedom for effectiveness. This can introduce colourless, directionless and contentionless reconfigurability to route individual wavelengths from fibre to fibre across multiple nodes to avoid wavelength blocking/collisions, increasing the flexibility and capacity of a network. For these networks to function optimally, novel hardware and dynamic algorithms identification and development is a critical task. Such tasks include wavelength assignment, signal routing, network restoration and network protection. In this work, we for the first time to our knowledge proposed a spectrum defragmentation technique through reallocation of the central frequency of the optical transmitter, to increase the probability of finding a sufficient continuous spectrum. This is to improve network resource utilisation, capacity and resolve wavelength contention associated with a flexible spectrum in optical communication networks. The following chapter provides details on a flexible spectrum in optical fibre networks utilising DWDM, optimising transmitter-receivers, advanced modulation formats, coherent detection, reconfigurable optical add and drop multiplexer (ROADM) technology to implement hardware and middleware platforms which address growing bandwidth demands for scalability, flexibility and cost-efficiency. A major attribute is tunable lasers, an essential component for future flexible spectrum with application to wavelength switching, routing, wavelength conversion and ROADM for the multi-node optical network through spectrum flexibility and cost-effective sharing of fibre links, transmitters and receivers. Spectrum slicing into fine granular sub-carriers and assigning several frequency slots to accommodate diverse traffic demands is a viable approach. This work experimentally presents a spectral efficient technique for bandwidth variability, wavelength allocation, routing, defragmentation and wavelength selective switches in the nodes of a network, capable of removing the fixed grid spacing using low cost, high bandwidth, power-efficient and wavelength-tunable vertical-cavity surface-emitting laser (VCSEL) transmitter directly modulated with 10 Gbps data. This to ensure that majority of the spectrum utilisation at finer channel spacing, wastage of the spectrum resource as caused by the wavelength continuity constraint reduction and it improves bandwidth utilisation. The technique is flexible in terms of modulation formats and accommodates various formats with spectrally continuous channels, fulfilling the future bandwidth demands with transmissions beyond 100 Gbps per channel while maintaining spectral efficiency.
- Full Text:
- Date Issued: 2020
An analysis of systemic risk in the South African banking sector
- Authors: Johnson, Clifford
- Date: 2018
- Subjects: Risk assessment -- South Africa , Finance -- South Africa Banks and banking -- South Africa Financial risk management -- South Africa
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10948/30551 , vital:30959
- Description: The topic of systemic risk has gained prominence over the last three decades, however, renewed interest and discourse on the subject has increased significantly since the global financial crisis of 2007. This dissertation investigates the impact systemic risk has on the South African banking sector and the externalities borne amongst the largest constituent banks during periods of distress. By means of quantile regression, the delta conditional value at risk (ΔCoVaR) as introduced by Adrian and Brunnermeier (2008), banking institutions are ranked according to their systemic risk contributions at horizontal and vertical levels. Using weekly observations from 25 January 2008 until 28 July 2017, the empirical results reveal that a loose link exists between an individual bank’s risk and its systemic contribution. Furthermore, during periods of distress, larger banks contribute the most to systemic risk of the system. However, horizontally – amongst banks – size does not automatically imply systemic importance. The implications of the results, given the study, highlight that regulation of banks at an individual level does not imply that an institution is operating systemically prudent. Furthermore, regulation of banks is welcomed in order to address systemic risk of an institution; however, regulators should be mindful of the vertical and horizontal aspects of systemic externalities.
- Full Text:
- Date Issued: 2018
- Authors: Johnson, Clifford
- Date: 2018
- Subjects: Risk assessment -- South Africa , Finance -- South Africa Banks and banking -- South Africa Financial risk management -- South Africa
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10948/30551 , vital:30959
- Description: The topic of systemic risk has gained prominence over the last three decades, however, renewed interest and discourse on the subject has increased significantly since the global financial crisis of 2007. This dissertation investigates the impact systemic risk has on the South African banking sector and the externalities borne amongst the largest constituent banks during periods of distress. By means of quantile regression, the delta conditional value at risk (ΔCoVaR) as introduced by Adrian and Brunnermeier (2008), banking institutions are ranked according to their systemic risk contributions at horizontal and vertical levels. Using weekly observations from 25 January 2008 until 28 July 2017, the empirical results reveal that a loose link exists between an individual bank’s risk and its systemic contribution. Furthermore, during periods of distress, larger banks contribute the most to systemic risk of the system. However, horizontally – amongst banks – size does not automatically imply systemic importance. The implications of the results, given the study, highlight that regulation of banks at an individual level does not imply that an institution is operating systemically prudent. Furthermore, regulation of banks is welcomed in order to address systemic risk of an institution; however, regulators should be mindful of the vertical and horizontal aspects of systemic externalities.
- Full Text:
- Date Issued: 2018
An assessment of Organisational Culture at an Information and Technology Company during a period of change
- Authors: Nzimande, Prosper Thelumusa
- Date: 2018
- Subjects: Organizational change , Corporate culture Organization -- Research Customer relations
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/22935 , vital:30150
- Description: Orientation: Change is inevitable, yet many organisational change efforts are not successful due to the culture of the organisation not supporting change. As a result,change objectives are not met and employees are left with a poor change experience. Research objective: The main objective of the study was therefore to determine the extent to which the organisational culture of a selected South African Information, Communication and Technology (ICT) organisation was ready for change, and supported goal alignment, team work, a customer focus and employee talent optimisation to attain desired Change Outcomes. Research design: The study adopted a quantitative method using a random sample method and survey as the data collecting instrument, which was administered to employees at a selected ICT organisation. Factor analysis resulted in a refinement of the initial cultural elements investigated. Main findings/results: The results revealed that the ICT organisation did reflect a customer orientation, change readiness, collaboration for continuous improvement and an environment that enabled performance, but that there was room for improvement. The results indicated that the respondents had doubts about whether the Change Outcomes were attained. All the cultural factors correlated positively with each other and positively correlated with Change Outcomes. A significant positive link was found between Collaboration for Continuous Innovation and Change Outcomes. Practical/managerial implications: Organisational change requires much effort from senior leaders, managers and employees and it is therefore more likely that, during change, attention will be focused on operational changes rather than on organisational culture. However, the study demonstrated that culture in general is very important, as it influences behaviour and provides identity to employees, and that culture is especially important during a period of change. During a period of change, culture can either enhance or hinder change. In addition, change often implies a change in culture. The study showed that during a period of change, team work is very important and that opportunities must be created for sharing ideas, collaboration and stretching goals, thus for innovation, and for finding better ways to serve customers.
- Full Text:
- Date Issued: 2018
- Authors: Nzimande, Prosper Thelumusa
- Date: 2018
- Subjects: Organizational change , Corporate culture Organization -- Research Customer relations
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/22935 , vital:30150
- Description: Orientation: Change is inevitable, yet many organisational change efforts are not successful due to the culture of the organisation not supporting change. As a result,change objectives are not met and employees are left with a poor change experience. Research objective: The main objective of the study was therefore to determine the extent to which the organisational culture of a selected South African Information, Communication and Technology (ICT) organisation was ready for change, and supported goal alignment, team work, a customer focus and employee talent optimisation to attain desired Change Outcomes. Research design: The study adopted a quantitative method using a random sample method and survey as the data collecting instrument, which was administered to employees at a selected ICT organisation. Factor analysis resulted in a refinement of the initial cultural elements investigated. Main findings/results: The results revealed that the ICT organisation did reflect a customer orientation, change readiness, collaboration for continuous improvement and an environment that enabled performance, but that there was room for improvement. The results indicated that the respondents had doubts about whether the Change Outcomes were attained. All the cultural factors correlated positively with each other and positively correlated with Change Outcomes. A significant positive link was found between Collaboration for Continuous Innovation and Change Outcomes. Practical/managerial implications: Organisational change requires much effort from senior leaders, managers and employees and it is therefore more likely that, during change, attention will be focused on operational changes rather than on organisational culture. However, the study demonstrated that culture in general is very important, as it influences behaviour and provides identity to employees, and that culture is especially important during a period of change. During a period of change, culture can either enhance or hinder change. In addition, change often implies a change in culture. The study showed that during a period of change, team work is very important and that opportunities must be created for sharing ideas, collaboration and stretching goals, thus for innovation, and for finding better ways to serve customers.
- Full Text:
- Date Issued: 2018
The relationship between engagement strategies and intention-to-stay of engineering professionals
- Authors: Sibiya, Petros Mandla
- Date: 2016
- Subjects: Employee retention -- South Africa Engineering -- Employment -- South Africa , Electric power-plants -- Maintenance and repair
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/13028 , vital:27145
- Description: The focus of the study was on the relationship between employee engagement strategies and intention-to-stay of engineering professionals at a power station. The investigated engagement strategies or drivers in the model adopted for this study included: leadership style, remuneration structure, physical and emotional work climate, nature of work and career development opportunities. The purpose of the study was to investigate and contribute to a better understanding of a voluntary turnover problem of engineering professionals at a power station by considering the influence of engagement on intention-to-stay. The research was conducted on a sample of 65 engineering professionals employed at a power station. The findings of the study revealed that only one variable, namely nature of work, was significantly related to employee engagement. It was also established that of the five engagement strategies investigated, nature of work and leadership style (transformational) were significantly related to intention-to-stay. A positive relationship between employee engagement and intention-to-stay was proven in this study.
- Full Text:
- Date Issued: 2016
- Authors: Sibiya, Petros Mandla
- Date: 2016
- Subjects: Employee retention -- South Africa Engineering -- Employment -- South Africa , Electric power-plants -- Maintenance and repair
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/13028 , vital:27145
- Description: The focus of the study was on the relationship between employee engagement strategies and intention-to-stay of engineering professionals at a power station. The investigated engagement strategies or drivers in the model adopted for this study included: leadership style, remuneration structure, physical and emotional work climate, nature of work and career development opportunities. The purpose of the study was to investigate and contribute to a better understanding of a voluntary turnover problem of engineering professionals at a power station by considering the influence of engagement on intention-to-stay. The research was conducted on a sample of 65 engineering professionals employed at a power station. The findings of the study revealed that only one variable, namely nature of work, was significantly related to employee engagement. It was also established that of the five engagement strategies investigated, nature of work and leadership style (transformational) were significantly related to intention-to-stay. A positive relationship between employee engagement and intention-to-stay was proven in this study.
- Full Text:
- Date Issued: 2016
An investigation into whether total productive maintenance is effectively applied at an automotive plant
- Authors: Wentzel, Louis
- Date: 2012
- Subjects: Production management , Automobile industry and trade
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:8902 , http://hdl.handle.net/10948/d1020994
- Description: For many manufacturing companies, equipment is the largest capital investment andeffective maintenance of these assets can impact on profitability. It extends equipment life, improves equipment availability and retains equipment in proper condition. Conversely, poorly maintained equipment may lead to more frequent equipment failures, poor utilisation of equipment and delayed production schedules. Malfunctioning equipment may result in scrap or products of poor quality. Total productive maintenance (TPM) is one of the most popular concepts for improving process dependability (Nakajima 1988). It focuses on increasing the effectiveness of maintenance which is commonly measured by the overall equipment effectiveness (OEE). Ford Struandale Engine Plant (FSEP) applies lean manufacturing through its Ford Production System (FPS) which consists of twelve elements. One element of FPS is Ford Total Productive Maintenance (FTPM) with the objective to maximise the overall effectiveness of plant facilities, equipment, processes and tooling through the focused efforts of work groups and the elimination of the major losses associated with manufacturing equipment. The concern for FSEP management was that although FTPM is implemented, the OEE data revealed that equipment availability targets are not achieved. The researcher identified a gap to investigate the reasons for the poor performance. A literature study was conducted to search for relevant information on the subject. A questionnaire was constructed from the theoretical information and a survey was conducted. After data collection the results were captured and analysed. The researcher made conclusions based on the data and made recommendations. The main findings were that autonomous maintenance is not functioning well, spares management is not good and the Computerised Maintenance Management System is underutilised. The recommendations were that these issues must be addressed.
- Full Text:
- Date Issued: 2012
- Authors: Wentzel, Louis
- Date: 2012
- Subjects: Production management , Automobile industry and trade
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:8902 , http://hdl.handle.net/10948/d1020994
- Description: For many manufacturing companies, equipment is the largest capital investment andeffective maintenance of these assets can impact on profitability. It extends equipment life, improves equipment availability and retains equipment in proper condition. Conversely, poorly maintained equipment may lead to more frequent equipment failures, poor utilisation of equipment and delayed production schedules. Malfunctioning equipment may result in scrap or products of poor quality. Total productive maintenance (TPM) is one of the most popular concepts for improving process dependability (Nakajima 1988). It focuses on increasing the effectiveness of maintenance which is commonly measured by the overall equipment effectiveness (OEE). Ford Struandale Engine Plant (FSEP) applies lean manufacturing through its Ford Production System (FPS) which consists of twelve elements. One element of FPS is Ford Total Productive Maintenance (FTPM) with the objective to maximise the overall effectiveness of plant facilities, equipment, processes and tooling through the focused efforts of work groups and the elimination of the major losses associated with manufacturing equipment. The concern for FSEP management was that although FTPM is implemented, the OEE data revealed that equipment availability targets are not achieved. The researcher identified a gap to investigate the reasons for the poor performance. A literature study was conducted to search for relevant information on the subject. A questionnaire was constructed from the theoretical information and a survey was conducted. After data collection the results were captured and analysed. The researcher made conclusions based on the data and made recommendations. The main findings were that autonomous maintenance is not functioning well, spares management is not good and the Computerised Maintenance Management System is underutilised. The recommendations were that these issues must be addressed.
- Full Text:
- Date Issued: 2012
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