A study of mobile VoIP performance in wireless broadband networks

Voice service is to date still the killer mobile service and the main source for operator revenue for years to come. Additionally, voice service will evolve from circuit switched technologies towards packet based Voice over IP (VoIP). However, using VoIP over wireless networks different from 3GPP cellular technologies makes it also a disruptive technology in the traditional telecommunication sector. The focus of this dissertation is on determining mobile VoIP performance in different wireless broadband systems with current state of the art networks, as well as the potential disruption to cellular operators when mobile VoIP is deployed over different access networks. The research method is based on an empirical model. The model and experiments are well documented and based on industry standards for voice quality evaluation. The evaluation provides results from both experiments in a controlled laboratory setup as well as from live scenarios. The research scope is first, evaluate each network technology independently; second, investigate vertical handover mobility cases; third, determine other aspects directly affecting end user experience (e.g., call setup delay and battery lifetime). The main contribution of this work is a systematic examination of mobile VoIP performance and end user experience. The research results point out the main challenges for achieving call toll quality, and how derive the required changes and technological performance roadmap for improved VoIP service. That is, investigate how the performance and usability of mobile VoIP can eventually be improved to be a suitable substitute for circuit switched voice. In addition, we evaluate the potential disruption to cellular operators that mobile VoIP brings when deployed over other access networks. This research extends the available knowledge from simulations and provides an insight into actual end user experience, as well as the challenges of using embedded clients in handheld devices. In addition, we find several issues that are not visible or accounted for in simulations in regard to network parameters, required retransmissions and decreased battery lifetime. The conclusion is that although the network performance of several wireless networks is good enough for near toll quality voice in static scenarios, there are still a number of problems which make it currently unfeasible to use as a primary voice service. Moreover, under mobility scenarios performance is degraded. Finally, there are other issues apart from network performance such as energy consumption, hardware limitations and lack of supporting business models (e.g., for WiFi mesh) that further limit the possibility of rolling out mobile VoIP services

Range estimation using phase difference of arrival technique

The principle of positioning is a technology of identification that enables object, people and/or assets to be tracked. This is basically to allow objects to be found for the purpose of rendering/obtaining services. Ranging technique therefore is an important part in anchor nodes location vis-à-vis the distance between anchors to the blind node. Integration of location capability into Wireless Sensor Network provides enablement in the location of network devices anywhere in the area of deployment, thereby making the network more valuable from the point of view of the application. Currently, there are several techniques which have been used to estimate ranges, most of the approaches which are dependent on a single frequency technique and those techniques are inaccurate in estimating the range, particularly in a multipath environment. The proposed work was to employ a dual-frequency phase difference of arrival technique for one-way propagation to capture ranges. Phase Difference of Arrival technique is a dual-frequency technique of ranging that offers better solution than already available single frequency ranging techniques. The technique has previously been used for radar application. Having evaluated the performance of this new technique for different frequency pairs with different frequency separation in different noise variance level, proof of the concept is provided using simulated data. The obtained results show that the proposed dual-frequency Phase-Difference of Arrival system is able to correctly find the location of, and track objects. Ranging simulation results show that frequency separation of 50MHz is best suited for one-way short-range application

A corporate social responsibility (CSR) analysis of the transformation of the mobile telephone industry of South Africa

Corporate Social Responsibility (CSR) requires companies to fulfil certain responsibilities in society that are outside of the core operational activities of the company. The socio-economic dynamics of the region or country that the company operates from, as well as the pressures those stakeholders tend to apply, have a bearing on the direction that the CSR development takes. Mirvis and Googins (2006) described the CSR developmental path followed by international companies. Before that Carroll (1991) had suggested a developmental pyramid that suggested that philanthropy represented the highest level of CSR development. This pyramid was later revised by Visser (2005) in order to suit the African environment. In South Africa CSR development is mainly driven by legislation through the BEE Act of 2003. This has resulted in the birth of industry charters that guide the development of CSR in different industries. To fulfil the requirements of the charter and score vital B-BBEE points, companies have to engage with both internal and external stakeholders, holistically. One such industry is the telecommunications industry, which formed the basis for this research, with special emphasis on the mobile telecommunications industry. The research set out to explore how the industry charter and company practices compared with the existing literature on CSR. The aim of this research was therefore to analyse the existing CSR practices in the mobile telecommunication industry in South Africa, where the B-BBEE Act plays a pivotal role in influencing practice. Using publically available documents, this research conducted an analysis of the B-BBEE components in the telecommunications charter as the catalyst to development of CSR in the South African mobile telecommunications industry, with the three dominant companies, - MTN, Vodacom and Cell C – being utilised as case studies. Key research findings were that transformation is still low in terms of equitable gender and racial representation at the top management level. The industry charter attempts to address these and other social challenges and economic problems. However, it does not address ecological issues that may emanate from the industry operations. Therefore, a CSR assessment framework that addresses all stakeholders for sustainable economic development is proposed

Bounds Computation for Symmetric Nets

Monotonicity in Markov chains is the starting point for quantitative abstraction of complex probabilistic systems leading to (upper or lower) bounds for probabilities and mean values relevant to their analysis. While numerous case studies exist in the literature, there is no generic model for which monotonicity is directly derived from its structure. Here we propose such a model and formalize it as a subclass of Stochastic Symmetric (Petri) Nets (SSNs) called Stochastic Monotonic SNs (SMSNs). On this subclass the monotonicity is proven by coupling arguments that can be applied on an abstract description of the state (symbolic marking). Our class includes both process synchronizations and resource sharings and can be extended to model open or cyclic closed systems. Automatic methods for transforming a non monotonic system into a monotonic one matching the MSN pattern, or for transforming a monotonic system with large state space into one with reduced state space are presented. We illustrate the interest of the proposed method by expressing standard monotonic models and modelling a flexible manufacturing system case study

Modelling and coverage improvement of DVB-T networks

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonThe necessity of accurate point-to-area and point-to-point prediction tools arises from the enormous demand in designing broadcasting systems for digital TV and cellular communications. Up to now, a considerable number of coverage prediction models for radio coverage has been developed. In electromagnetic wave propagation theory, there are three types of propagation models. Empirical models that are based on a large quantity of measurement data are elementary but not very accurate. Semi-deterministic models that are based on measurement data and electromagnetic theory of propagation, which are more precise. Finally, deterministic models based on theoretical physics, like diffraction theory and Fresnel theory, that require a significant amount of geometrical data about the propagation terrain profile but are the most accurate. The primary outcomes of this research are the comparative study and improvement of several propagation models, using a significant quantity of measurements and simulations and the deduction of useful conclusions to be used by engineers to improve propagation predictions further. In this research, the Longley-Rice (ITM) Irregular Terrain Model model was used, a classic model used for TV coverage prediction, which model is to date the preferred model of the FCC (Federal Communications Commission) in the US for FM-TV coverage calculations. To run the model, the Radio Mobile program (Radio Propagation and Virtual Mapping Freeware) was used based on the Longley-Rice Model ITM, including the 3-arc-second Satellite Radar Terrain Mission (SRTM) maps and the SPLAT! program (an RF Signal Propagation, Loss, And Terrain analysis tool), which also relies on the Longley-Rice ITM model and makes use of SRTM maps. Both programs work in Windows operating system (Windows7 Professional, 64 bits). Another model used in this research was SPLAT! with ITWOM (Irregular Terrain with Obstructions Model) which combines empirical data from the ITU-R P.1546 model and other ITU recommendations in conjunction with Beer's and Snell's laws. The ITU-R Recommendation P.1546 model and the empirical Hata-Davidson model using HAAT were also utilized in this research. The Single Knife-Edge (SKE) model was coded in MATLAB and utilized in this research as a simple reference model, where only one main obstacle is considered. Other well-known multiple knife-edge diffraction models employed in this study are the Epstein-Peterson, Deygout, and Giovaneli models. For these deterministic models, individual MATLAB programs were written. Simulations produced by the models were limited to the main two knife-edges of the propagation path for immediate comparison with the Longley-Rice model which uses the “double knife-edge” approach. All measurement campaigns took place in Northern Greece and Southern (F.Y.R.O.M) Former Yugoslav Republic of Macedonia using a Rohde & Schwarz FSH-3 portable spectrum analyser and precision calibrated antennas

Adoption and utilisation of e-government systems by citizens in SADC: the case of Zambia and Zimbabwe.

Doctoral degree. University of KwaZulu-Natal, Durban.Electronic government (e-Government) offers great opportunities for transforming the public service delivery systems by providing an effective, efficient and transparent tool for facilitating the active participation of citizens in government decision making processes and for achieving good governance. However, the success of e-government is not entirely dependent on the provision of excellent e-government systems (supply-driven), but also on other factors like system acceptance and utilisation by citizens. Whilst the United Nations e-Government Surveys have demonstrated the proliferation of e-government initiatives in both developed and developing countries, the implementation, adoption and utilisation of such systems in developing nations is constantly affected by many challenges. Many citizens are hesitant to adopt and use e-government systems for various reasons and in some cases, such decisions are indeed merited. Citizens’ awareness, technical aptitude, confidence and trust in the government and its e-government systems are salient factors that are impacting the acceptance and utilisation of such systems. Similarly, practitioners (decision and policy makers, designers and implementers) of e-government have noted that most of the challenges being encountered by citizens are distinctively pertinent to national and regional socio-economic, cultural, political, and technological circumstances, and thus require a contextual and holistic approach for solutions. This study is driven by the quest to examine and establish the fundamental factors that are affecting citizens’ capacity, effort and behavioural intentions to adopt and continue using egovernment systems in the Southern African Development Community (SADC) region; using Zimbabwe and Zambia as a case study. Thus, this study focuses on the government to citizen (G2C) domain with particular emphasis on the citizen-side. Currently, there are no holistic, people-driven models that could be used to assist and guide practitioners on e-government maters (including guiding citizen-informed designs and implementation, predicting and stimulating adoption and utilisation) for the SADC region and other developing nations with similar socio-economic and technological settings. This study aims to develop a people-driven e-government adoption and utilisation model (PDEGAUM), build upon two long-established theoretical frameworks; the Extended Unified Theory of Acceptance and Use of Technology (UTAUT2) (focused on understanding the demand-side) and the ITU E-Government Implementation Toolkit (focused on understanding how the supply-side could be aligned with, and be informed by, the demand-side). An explanatory sequential mixed methods approach was considered most appropriate for testing the PDEGAUM conceptual model. Multistage sampling techniques were used to select the 800 respondents (drawn from Zimbabwe and Zambia) for the survey method (selfadministered questionnaires were used). After the pre-analysis screening of the quantitative data, only 736 questionnaires were used for data analysis (comprised of 489 citizens who have used e-government systems and 247 have not used). Explanatory Factor Analysis (EFA) and regression analysis (using IBM Statistical Package for the Social Sciences (SPSS)); and structural equation modelling (SEM) and Confirmatory Factor Analysis (CFA) (using IBM Analysis of Moment Structures (AMOS)) were selected for testing the model fit of the proposed model. All but one of the hypotheses was confirmed by this study. Semi-structured interviews (serving a confirmatory role) were pursued with 8 purposively selected interviewees from the respondents who had participated earlier on in the survey. The Total Quality Framework (TQF) was adopted as the most suitable theoretical lens for guiding the analysis of the qualitative data; thematically using the Nvivo Plus qualitative data analysis software (QDAS). The qualitative results confirmed the quantitative results. Findings of this study confirm the proposed PDEGAUM model as being suitable for the SADC region. The PDEGAUM model is novel in that it places citizens’ demands and input at the centre stage of spearheading e-government initiatives, which in turn informs e-government implementation. This approach contradicts the supply-driven approach by being contextuallyaware of citizens’ concerns in-line with e-government initiatives. Such a holistic gesture by the government is believed to go a long way in fostering and stimulating the adoption and utilisation of e-government systems. Decisively, the findings of this study have demonstrated that a people-driven approach constitutes the basis for rolling-out successful e-government systems, particularly in the context of the SADC region and other developing countries that are plagued by complicated socio-economic and political dynamics

The New Politics of Patronage: The Arms Trade and Clientelism in the Arab World

In states without robust democratic institutions, public resources are often allocated on the basis of patronage. This distribution of patronage, along with the manipulation of official institutions (such as electoral systems and the judiciary) and the deployment of the coercive arms of the state provided the formula for authoritarian longevity in the Arab World. However, much regional scholarship continues to focus on the process through which patronage is distributed with little reference to how the underlying resources accrue to Arab regimes in the first place. Such studies fail to interrogate the organizational and financial interests of the external institutions (such as oil markets and aid organizations) that mediate this transfer of resources, and how those interests shape methods and patterns of resource distribution within Arab States. This paper is an attempt to identify some of these institutions and patterns by focusing on the array of patronage resources made available through the arms purchases executed by regional governments. The specific class of resources examined here is reciprocal investment contracts that U.S. defense firms negotiate with procuring country governments in order to facilitate arms sales, known in industry parlance as `defense offsets.' Procuring states design their own offset policies, including the amount of investment that foreign arms manufacturers are required to make and the domestic enterprises where those funds must be allocated. The procuring state's discretion over the process allows us to draw some conclusions about how these governments distribute offset investment to strengthen incumbents' patronage-based support networks. This analysis also reveals how U.S. defense firms are able to influence the negotiation process in order to secure their own financial benefits. By examining how defense firms and their customers in the Middle East collude to structure weapons contracts in order to generate offset agreements that are mutually beneficial, we gain a better understanding of how patronage politics operates in the contemporary regional context. We are likewise alerted to the subtle ways in which influential external actors can insinuate their own interests into the process, and how the interactions between these groups create ever-evolving new opportunities for patronage politics

Telecommunication Systems

This book is based on both industrial and academic research efforts in which a number of recent advancements and rare insights into telecommunication systems are well presented. The volume is organized into four parts: "Telecommunication Protocol, Optimization, and Security Frameworks", "Next-Generation Optical Access Technologies", "Convergence of Wireless-Optical Networks" and "Advanced Relay and Antenna Systems for Smart Networks." Chapters within these parts are self-contained and cross-referenced to facilitate further study