In periodic wireless broadcasting, air behaves like a storage medium requiring new data organization and access methods.Due to power limit for the portable units (ex. the palmtop), how to design an energy-saving organization is a key issue.Imielinski et al. have proposed the hashing based schemes, including the Hashing A and Hashing B schemes, to save energy in the progress of getting data of interest. The Hashing B scheme improves the directory miss phenomenon in the Hashing A scheme, where the directory miss is that the client's initial probe comes before the bucket containing his key but after the bucket which contains a proper offset. However, based on these two schemes, if the differences between the minimum overflow and the other overflows are large extremely or the small overflows appear near the rear part of the broadcast file, both schemes have a poor performance. Therefore, in this thesis, we propose four multiple-hashing-functions-based schemes, including the FirstR, FirstL, AvgK and TopK schemes, to overcome such the situations. The basic idea is to use cutlines to divide the broadcast file with N logical buckets into several regions, and then each region may have the different minimum overflow. Since the minimum overflow in each region can be different, we can have different hashing functions for those regions to determine the positions of the designated buckets. Among the proposed schemes, the difference is how to determine the positions of the cutlines. The FirstR scheme finds those cutlines from the right end to the left whenever the difference of overflows of two adjacent logical buckets is greater than or equal to 1. The FirstL scheme finds those cutlines from the left end to the right whenever the difference of overflows of two adjacent logical buckets is greater than or equal to 1. In the AvgK scheme, we first calculate AvgD, the average of the differences of two consecutive overflows whose values are large than or equal to 1. Then we find cutlines from the left end to the right whenever the difference of two adjacent logical buckets is greater than or equal to AvgD. The TopK determines the cutlines by considering the descending order of the differences of overflows. From our performance analysis and simulation study, the performance of the TopK scheme is the best among the proposed schemes. Therefore, we then make a comparison between the TopK scheme and the Hashing B scheme. Since the number of the hashing functions in the TopK scheme is larger than those in the Hashing B, the physical bucket in the TopK scheme is somewhat bigger than that in the m Hashing B scheme. In our simulation, we have considered this factor as well. From our performance analysis and simulation study, we show that the performance of the TopK scheme performs better than that of the Hashing B scheme, even though the above factor about the storage size is considered. The TopK scheme improves the directory miss in the Hashing B scheme; therefore, the average access time is improved excellently.

<p>This thesis is a study of a new specification for end user interactivity developed by the Open Mobile Alliance, the specification is called OMA BCAST Service Interaction Function. The specification is one part of the OMA BCAST Service Enabler, which enables service delivery to mobile devices, where the most common service is mobile television. The Service Interaction Function enables end user interactivity related to a service, this could be a poll about the current television program or a chat where every message is presented to the users that are watching the same channel.</p><p>The specification is still of draft version and the scope of this thesis has been to investigate the Service Interaction Function and implement a PC prototype.</p>

Wireless data broadcast is an efficient way to disseminate digital information to clients equipped with mobile devices. It allows a huge number of the mobile clients simultaneously access data at anytime and anywhere in the wireless environments. Applications using wireless data broadcast to disseminate information include accessing stock activities and traffic conditions. Using index technologies on the broadcast file, i.e., selective tuning, can reduce a lot of energy consumption of the mobile devices without significantly increasing client waiting time. Most of the research work for selective tuning assumes that each data item broadcast on the wireless channel is fairly evenly accessed by mobile clients. In real-life applications, more popular data may be frequently accessed by clients than less popular ones, i.e., skewed access patterns. In this dissertation, to support efficiently selective tuning with skewed access patterns in the single-channel wireless environments, we first propose a skewed distributed index, SDI, on the uniform data broadcast, on which each data item is broadcast once in a broadcast cycle. Second, we propose a skewed index, SI, on the nonuniform data broadcast, on which a few popular data items are broadcast more frequently in a broadcast cycle than the others. The first proposed algorithm, SDI, considers the access probabilities of data items and the replication of index nodes. The proposed algorithm traverses a balanced tree to determine whether an index node should be replicated by considering the access probability of its child node. In our performance analysis and simulation results, we have shown that our proposed algorithm outperforms the variant-fanout tree index and the distributed index. The second proposed algorithm, SI, applies Acharya et al.'s Broadcast Disks to generate a broadcast program, in which the popular data items are broadcast more times than the others, in order to reduce client waiting time. Moreover, the proposed algorithm builds a skewed tree for these data items and allocates index nodes for the popular data items more times than those for the less popular ones in a broadcast cycle. From our performance analysis and simulation results, we have shown that our proposed SI outperforms the flexible index and the flexible distributed index.

This thesis is a study of a new specification for end user interactivity developed by the Open Mobile Alliance, the specification is called OMA BCAST Service Interaction Function. The specification is one part of the OMA BCAST Service Enabler, which enables service delivery to mobile devices, where the most common service is mobile television. The Service Interaction Function enables end user interactivity related to a service, this could be a poll about the current television program or a chat where every message is presented to the users that are watching the same channel. The specification is still of draft version and the scope of this thesis has been to investigate the Service Interaction Function and implement a PC prototype.

Africa’s rapid adoption of the mobile phone is quickly closing the digital divide in voice services. But, just as one divide is closing, another one is widening. Consumers almost everywhere are demanding more services and higher Internet access data rates. In the developing world the knowledge gained through access to information is creating unprecedented opportunities and is having a dramatic impact on the way people live and work. Africa, however, has been largely left behind in the shift to broadband. Increasing the availability and affordability of broadband services is thus high on the agenda for policy makers in Africa, though it will require major efforts from both government and the private sector. Fundamental to the all efforts to close the “digital divide” is the need to provide a ubiquitous and affordable access network that will enable distribution of broadband services to anywhere, and anytime throughout Africa. While many kinds of broadband services are being offered to the African population, the currently available services have failed to reach the majority of Africans living in rural areas. This poses a very pertinent question that justifies further investigations: why have the existing broadband services failed to satisfy Africa’s need for a ubiquitous digital communication service. The lack of penetration of the existing services makes it clear that a different technology and service offering is needed, a service offering that is affordable to the large consumer market segment and which can complement the mobile and ADSL broadband networks to provide services to all of Africa on a cost effective basis. This research work investigates the current business and technology domains and develops new knowledge and the insights that are required firstly to understand why existing broadband services are failing to reach rural Africa and secondly to understand what criteria must be satisfied to deliver broadband access services to the mass consumer Africa market. The research work focuses on the interrelationships between markets, technology and business of the consumer broadband market and defines new thinking as reference to provide guidance to the future development of more suitable broadband offerings for the rural African market. The study centres around three principal areas of knowledge contribution. Analysis of the primary factors impacting the delivery of broadband services Firstly the study addresses the current market dynamics and technology realities to determine two critical aspects: 1) Can the mass market afford broadband services or will it remain the privilege of the higher income groups? And, 2) Can existing mobile broadband , ADSL and satellite access services meet the demands to service the mass market or is an alternative technology option required? Through analytical review the study determined that there is a large, and growing, middle class market that can afford broadband access services. This market sector is quantified in terms of consumer income levels and demographic user data. The study formulates the commercial and service criteria applicable to a broadband access service on servicing this target market. The study further investigates the availability, affordability and market penetration of the current mobile and ADSL broadband services and found that the available service options cannot effectively meet the current and future demand. The limitation in meeting the current market demand leads to a large under serviced consumer market in Africa. The study proposes a unique approach to quantify the specific under-serviced gap, which will not be met by currently available broadband technologies. The technology comparative study provides new insight into the limitations of mobile 3G broadband services and why this technology will not be able to meet the future demand for consumer broadband services in Africa. The technology study furthermore quantifies the advantages of using satellite technology to implement a mass consumer broadband service in Africa. The study proves that the ubiquitous nature and rapid deployment capabilities of satellite access networks provides distinct benefits when deploying a mass consumer network which makes satellite the technology of choice for consumer broadband services. We then continue to assess the ability of existing satellite broadband offerings to satisfy the needs of African end-users, and find that those offerings have been optimized for the needs and affordability levels of customers from the develop world. The result is that satellite broadband services aimed at the African end-user is primarily used by corporate and institutional customers, with little penetration of the consumer market. This finding provides the motivation for developing a business model that can leverage available technology to effectively service the African consumer market. Innovation of new concepts to support a viable broadband business strategy The mobile prepay model as well as the DStv pay-TV subscription services have demonstrated the need for a specific business innovation to ensure successful market adoption of new technologies. Both these industries have demonstrated that innovative approaches in the commercialization of technology solutions are critical to ensure the mass adoption thereof. The second section of the study therefore focuses on the innovations that are required to overcome the obstacles as identified in section 1 in order to arrive at a business strategy and business model that will prove to be viable in the delivery of broadband services to the rural African consumer market. The first challenge is the selection of the most appropriate technology platforms and the architectural design of the delivery systems to effectively service the mass consumer market. In order to adapt the business models employed by existing satellite broadband service providers the study defines the following two specific business innovation concepts that contribute to a new business paradigm for mass market broadband access services: 1) Through applied billing model innovation the study defines a new billing structure for broadband services and set a completely new paradigm for users to influence the cost of the service. The new billing model provides end-user the capability to adapt their broadband usage patterns to meet their budget constraints. 2) To successfully deliver a technology service to an emerging market requires a very specific organisational structure that effectively integrates knowledge, capability and funding while minimizing risk and uncertainty. The study proposes a new symbiotic organisational structure that elegantly combines capability and knowledge while minimizing funding requirements to ensure the acceptable market development risk. Development of a business model simulator for satellite broadband service delivery The deployment of a new type of satellite broadband service to rural Africa on an experimental basis is too expensive to be conducted for research purposes. A more practical approach that is also widely used in other domains of engineering is to construct a simulated model of the system being studied. The third knowledge contribution area of the study therefore focuses on constructing a mathematical model of the expected behavior of a business operation that provides satellite based broadband services to the African market. This simulator can be applied to quantitatively analyze various existing or proposed new business strategies. The business model simulation integrates all the business, market, technology and commercial relationships that impacts on the expected behavior of such an operation and provides a quantified model of expected business behavior based on the underlying dynamics of the satellite broadband industry. The development and validation of the business model simulator represents a unique contribution to this industry as no results of a similar model that represents the operations of a satellite broadband access service provider has been published before. The model empowers Service Providers and industry stakeholders to analyze different business strategies and to quantify the impact of various business decisions. In general it can be stated that this research work adds knowledge and insight to the field of applied business strategy as applicable to providing advanced technology-based services for emerging markets. The final outcome of this research study is the business model simulator. It integrates various market and business elements as well as satellite network engineering practises into an integrated financial cost modelling, business scenario planning and engineering network design tool. Through this integration of known disciplines the study provides an additional extension to the field of satellite business engineering. / PhD (Electronic Engineering), North-West University, Potchefstroom Campus, 2013

Africa’s rapid adoption of the mobile phone is quickly closing the digital divide in voice services. But, just as one divide is closing, another one is widening. Consumers almost everywhere are demanding more services and higher Internet access data rates. In the developing world the knowledge gained through access to information is creating unprecedented opportunities and is having a dramatic impact on the way people live and work. Africa, however, has been largely left behind in the shift to broadband. Increasing the availability and affordability of broadband services is thus high on the agenda for policy makers in Africa, though it will require major efforts from both government and the private sector. Fundamental to the all efforts to close the “digital divide” is the need to provide a ubiquitous and affordable access network that will enable distribution of broadband services to anywhere, and anytime throughout Africa. While many kinds of broadband services are being offered to the African population, the currently available services have failed to reach the majority of Africans living in rural areas. This poses a very pertinent question that justifies further investigations: why have the existing broadband services failed to satisfy Africa’s need for a ubiquitous digital communication service. The lack of penetration of the existing services makes it clear that a different technology and service offering is needed, a service offering that is affordable to the large consumer market segment and which can complement the mobile and ADSL broadband networks to provide services to all of Africa on a cost effective basis. This research work investigates the current business and technology domains and develops new knowledge and the insights that are required firstly to understand why existing broadband services are failing to reach rural Africa and secondly to understand what criteria must be satisfied to deliver broadband access services to the mass consumer Africa market. The research work focuses on the interrelationships between markets, technology and business of the consumer broadband market and defines new thinking as reference to provide guidance to the future development of more suitable broadband offerings for the rural African market. The study centres around three principal areas of knowledge contribution. Analysis of the primary factors impacting the delivery of broadband services Firstly the study addresses the current market dynamics and technology realities to determine two critical aspects: 1) Can the mass market afford broadband services or will it remain the privilege of the higher income groups? And, 2) Can existing mobile broadband , ADSL and satellite access services meet the demands to service the mass market or is an alternative technology option required? Through analytical review the study determined that there is a large, and growing, middle class market that can afford broadband access services. This market sector is quantified in terms of consumer income levels and demographic user data. The study formulates the commercial and service criteria applicable to a broadband access service on servicing this target market. The study further investigates the availability, affordability and market penetration of the current mobile and ADSL broadband services and found that the available service options cannot effectively meet the current and future demand. The limitation in meeting the current market demand leads to a large under serviced consumer market in Africa. The study proposes a unique approach to quantify the specific under-serviced gap, which will not be met by currently available broadband technologies. The technology comparative study provides new insight into the limitations of mobile 3G broadband services and why this technology will not be able to meet the future demand for consumer broadband services in Africa. The technology study furthermore quantifies the advantages of using satellite technology to implement a mass consumer broadband service in Africa. The study proves that the ubiquitous nature and rapid deployment capabilities of satellite access networks provides distinct benefits when deploying a mass consumer network which makes satellite the technology of choice for consumer broadband services. We then continue to assess the ability of existing satellite broadband offerings to satisfy the needs of African end-users, and find that those offerings have been optimized for the needs and affordability levels of customers from the develop world. The result is that satellite broadband services aimed at the African end-user is primarily used by corporate and institutional customers, with little penetration of the consumer market. This finding provides the motivation for developing a business model that can leverage available technology to effectively service the African consumer market. Innovation of new concepts to support a viable broadband business strategy The mobile prepay model as well as the DStv pay-TV subscription services have demonstrated the need for a specific business innovation to ensure successful market adoption of new technologies. Both these industries have demonstrated that innovative approaches in the commercialization of technology solutions are critical to ensure the mass adoption thereof. The second section of the study therefore focuses on the innovations that are required to overcome the obstacles as identified in section 1 in order to arrive at a business strategy and business model that will prove to be viable in the delivery of broadband services to the rural African consumer market. The first challenge is the selection of the most appropriate technology platforms and the architectural design of the delivery systems to effectively service the mass consumer market. In order to adapt the business models employed by existing satellite broadband service providers the study defines the following two specific business innovation concepts that contribute to a new business paradigm for mass market broadband access services: 1) Through applied billing model innovation the study defines a new billing structure for broadband services and set a completely new paradigm for users to influence the cost of the service. The new billing model provides end-user the capability to adapt their broadband usage patterns to meet their budget constraints. 2) To successfully deliver a technology service to an emerging market requires a very specific organisational structure that effectively integrates knowledge, capability and funding while minimizing risk and uncertainty. The study proposes a new symbiotic organisational structure that elegantly combines capability and knowledge while minimizing funding requirements to ensure the acceptable market development risk. Development of a business model simulator for satellite broadband service delivery The deployment of a new type of satellite broadband service to rural Africa on an experimental basis is too expensive to be conducted for research purposes. A more practical approach that is also widely used in other domains of engineering is to construct a simulated model of the system being studied. The third knowledge contribution area of the study therefore focuses on constructing a mathematical model of the expected behavior of a business operation that provides satellite based broadband services to the African market. This simulator can be applied to quantitatively analyze various existing or proposed new business strategies. The business model simulation integrates all the business, market, technology and commercial relationships that impacts on the expected behavior of such an operation and provides a quantified model of expected business behavior based on the underlying dynamics of the satellite broadband industry. The development and validation of the business model simulator represents a unique contribution to this industry as no results of a similar model that represents the operations of a satellite broadband access service provider has been published before. The model empowers Service Providers and industry stakeholders to analyze different business strategies and to quantify the impact of various business decisions. In general it can be stated that this research work adds knowledge and insight to the field of applied business strategy as applicable to providing advanced technology-based services for emerging markets. The final outcome of this research study is the business model simulator. It integrates various market and business elements as well as satellite network engineering practises into an integrated financial cost modelling, business scenario planning and engineering network design tool. Through this integration of known disciplines the study provides an additional extension to the field of satellite business engineering. / PhD (Electronic Engineering), North-West University, Potchefstroom Campus, 2013