Rural areas in Africa often have poor telecommunication infrastructure. Mobile phones, if available, are frequently unaffordable to most users. Wireless mesh networks (WMNs) offer an alternative possibility of low cost voice and data communications. The focus of this research is a laboratory study of WMNs that mimic conditions found in rural areas. This work investigates routing strategies for the Mesh Potato (MP). The MP is an effective alternative communication technology that has minimal configuration requirements, low cost of deployment, low power consumption and resilience that make it an attractive choice for rural areas. The MP runs a new mesh networking algorithm called the better approach to mobile ad hoc networking (B.A.T.M.A.N or Batman). This allows a WMN to be established in which users can use plain old telephones to talk to each other using Voice over IP (VoIP). Batman daemon (Batmand) is the implementation of Batman algorithm used by the MP. Batmand is a minimalistic routing protocol which performs well in laboratory experiments. The question raised is whether adding more service specific routing metrics improve the quality of service (QoS) observed in Batmand network in practice. The research investigates delay, packet loss, throughput and jitter as performance parameters (metrics) that may serve as options to improve the simplistic Batman algorithms route selection process. These metrics are essential for QoS in voice- and data-sensitive networks. Specific focus was given to delay and it is the metric added to Batmand. In addition the research examines how well the different applications such as voice and data are supported on the Batmand network under different routing scenarios. The research approach adopted in this dissertation was experimental and an indoor testbed was created to replicate the basic scenarios encountered in the rural environment. The essential characteristics found in the Mdumbi region of the Eastern Cape, South Africa, were taken as a case study in this dissertation. The testbed was used to compare the original Batman algorithm implemented as Batmand, referred to here as O-Batmand, routing protocol and the resultant Batmand version obtained from the addition of the delay-routing metric called modified Batmand (M-Batmand). The research produced a number of findings. As the number of hops increased the per-formance of the network decreased for both protocols. O-Batmand is well suited for the task of routing packets inside a wireless network. It is designed and works for voice packets and supports data services. This is also true for the M-Batmand implementation. M-Batmand was developed as an improvement to the O-Batmand implementation at the cost of increased complexity, experienced by the protocol through modifications of its route selection process. The modification involved adding network delay values to its route selection process. This addition resulted in a protocol that is delay sensitive; however, the overall performance gains were inexistent. The main conclusions drawn from this study are that O-Batmand cannot be modified to include additional metrics and be expected to improve its performance. Second conclusion is that M-Batmand did not improve the overall performance of the O-Batmand protocol. The addition of the delay metric actually hindered O-Batmand's performance to the extent that no overall performance gains were realised. Sources of performance degradations are: increased overhead, from added delay data, in the network control packets called originator messages (OGMs). M-Batmand performs calculation which O-Batmand did not increasing CPU cycle needs. Lastly upon further internal protocol investigation it is seen that the rate of route delay data updates is slower than the original metric used by the protocol. This creates route fluctuations as route selection process will change when the updated delay values are added and change again when there are not as the network obtains the updated delay data. Both protocols support voice and data, however, the results show that the quality of the network deteriorates in the testbed with increasing hops. This affects voice more so then it does data as routes become more unstable with each increasing hop. Further Batmand is best at supporting voice and data as it outperforms M-Batmand in the laboratory experiments conducted. This dissertation argues that while there may exist one or a combination of metrics amongst the researched list (delay, packet loss, throughput and jitter) that may actually improve the performance of the protocol, it is extremely hard to realize such gains in practice.

The fields of Wireless sensor networks and RFID technology are two examples of the current move to ubiquitous computing. Wireless sensor networks has emerged as a tool for long term remote monitoring for applications ranging from agriculture to military. While in RFID we have already seen it being used in everyday life from access control to asset tracking. The integration of these two fields allows for a whole range of new applications, the focus of this dissertation is to present a wireless sensor network platform which incorporates a hybrid RFID sensor mote for the detection of environmental conditions and the locating of objects or personnel within an environment. The solution that is proposed comprises of both hardware and software but focuses on the design of the platforms’ prototype wireless sensor mote which provides object detection through the use of an RFID reader and environmental conditions by using low cost slave sensors. The solution was then applied to solving the problem of locating mining personnel and detecting hazardous levels of methane gas for use in underground mines.

ICT has furthered the social and economic development of societies but, rural African communities have lagged behind due to issues such as sparse population, low household income, a lack of electricity and other basic infrastructure that make it unattractive for telecommunication service providers to extend service provision. Where the service is available, ubiquitous service coverage has not translated into ubiquitous access for individuals because of the associated costs. A community-wide WMN offering VoIP using fixed telephone handsets has been deployed as a viable alternative to the cellular service provider. The effectiveness of this WMN VoIP service springs from the mobile phone usage statistics which showed that the majority of calls made are intra-community. This dissertation has been an effort towards improved communication and access to information for the under-served communities. Key contributions include, mobile VoIP support, translation gateway deployment to make textual information accessible in voice form via the phone, IP-based radio for community information dissemination. The lack of electricity has been mitigated by the use of low-power devices. In order to circumvent the computational challenges posed by the processing and storage limitations of these devices, a decentralised system architecture whereby the processing and storage load are distributed across the mesh nodes has been proposed. High-performance equipment can be stationed at the closest possible place with electricity in the area and connectivity extended to the non-electrified areas using low-power mesh networking devices. Implementation techniques were investigated and performance parameters measured. The quality of service experienced by the user was assessed using objective methods and QoS correlation models. A MOS value of 4.29, i.e. very good, was achieved for the mobile VoIP call quality, with the underlying hardware supporting up to 15 point-to-point simultaneous calls using SIP and the G.711 based codec. Using the PEAQ algorithm to evaluate the IP-based radio, a PEAQ value of 4.15, i.e. good, was achieved. Streaming audio across the network reduces the available bandwidth by 8Kbps per client due to the unicast nature of streaming. Therefore, a multicast approach has been proposed for efficient bandwidth utilization. The quality of the text-to-voice service rendered by the translation gateway had a PESQ score of 1.6 i.e. poor. The poor performance can be attributed to the TTS engine implementation and also to the lack of robustness in the time-alignment module of the PESQ algorithm. The dissertation also proposes the use of the WMN infrastructure as a back-haul to isles of WSNs deployed in areas of interest to provide access to information about environmental variables useful in decision making.

The emerging sensor networking applications are predicting the deployment of sensor devices in thousands of computing elements into multi-technology and multi-protocol platforms. Access to information will be available not only anytime and anywhere, but also using anything in a first-mile of the Internet referred to as the internet-of-things (IoT). The management of such a large-scale and heterogeneous network, would benefit from some of the traditional IP-based network management techniques such as load and energy balancing, which can be re-factored to achieve efficient routing of sensor network traffic. Research has shown that minimizing the path interference on nodes was necessary to improve traffic engineering in connection oriented networks. The same principle has been applied in past research in the context of the IoT to reveal that the least interference beaconing protocol (LIBP); a protocol derived from the least interference beaconing algorithm (LIBA) outperforms the Collection Tree Protocol (CTP) and Tiny OS Beaconing (ToB) protocol, in terms of energy efficiency and lifetime of the sensor network. However for the purpose of efficiency and accuracy, it is relevant, useful and critical to revisit or re-examine the LIBA algorithm in terms of correctness and investigate potential avenues for improvement. The main contributions of this research work are threefold. Firstly, we build upon formal methods to verify the correctness of the main principles underlying the LIBA, in terms of energy efficiency and interference minimization. The interference is here defined at each node by the number of routing paths carrying the sensor readings from the motes to the sink of the network that traverse the node. Our findings reveal the limitations in LIBA. Secondly, building upon these limitations, we propose two improvements to the algorithm: an algorithm called LIBA+ that improves the algorithm performance by keeping track of the energy usage of the sensor nodes, and a multi-sink version of the algorithm called LIBAMN that extends the algorithm to account for multiple sinks or gateways. These enhancements present preventive mechanisms to include in IoT platforms in order to improve traffic engineering, the security of network protocols and network stability. Lastly, we present analytical results, which reveal that the LIBA algorithm can be improved by more than 84% in terms of energy balancing. These results reveal that formal methods remain essential in the evaluation and performance improvement of wireless sensor network algorithms and protocols.

It is well discussed and understood that there is still a need for suitable security for the Internet of Things. It is however still not clear how existing or emerging security paradigms can be effectively applied to a network of constrained nodes in a lossy communications environment. This thesis provides a survey into what routing protocols can be used with network security in mind. What will also be discussed, is an implementation, that in conjunction which a robust routing protocol, can provide security for a network of constrained devices with a certain level of confidence. The implementation and design involves including communications encryption and centralized non-cryptographic methods for securing the network. This thesis basically explores the use of multiple security mechanisms in an Internet of Things environment by using Contiki OS as the platform of choice for simulations and testing.

This thesis work takes an investigative approach into developing a middleware solution for managing services in a community cloud computing infrastructure predominantly made of interconnected low power wireless devices. The thesis extends itself slightly outside of this acute framing to ensure heterogeneity is accounted for. The developed framework, in its draft implementation, provides networks with value added functionality in a way which minimally impacts nodes on the network. Two sub-protocols are developed and successfully implemented in order to achieve efficient discovery and allocation of the community cloud resources. First results are promising as the systems developed show both low resource consumption in its application, but also the ability to effectively transfer services through the network while evenly distributing load amongst computing resources on the network.

Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 237-254). Available also in a digital version from Dissertation Abstracts.

Memoria para optar al título de Ingeniero Civil Eléctrico / El paradigma de comunicación Internet of Things (IoT), el cual plantea la posibilidad de interconectar objetos cotidianos y toda clase de dispositivos convencionales a Internet, está actualmente en pleno desarrollo. El gran número de nodos que se espera conectar a Internet exige a su vez la implementación a gran escala de Internet Protocol versión 6 (IPv6). IoT busca el desarrollo de nuevas aplicaciones y ha impulsado la creación de nuevas arquitecturas de red y nuevas clases de dispositivos. Las redes Low Power Wide Area Networks (LPWAN) han surgido recientemente como una evolución natural del concepto Wireless Sensor Networks (WSN), redes de sensores in- terconectadas. A la luz del IoT, las nuevas redes LPWAN abren un nuevo campo de desarrollo, principalmente enfocado en servicios de monitoreo y afines que se desarrollen en áreas am- plias y no requieran grandes tasas de transferencia. Los dispositivos LPWAN se caracterizan por ser de bajo consumo energético y de bajo costo, facilitando su despliegue masivo por largos períodos sin necesidad de recargar sus baterías. Long Range Wide Area Network (LoRaWAN) es una de las primeras y principales tec- nologías LPWAN, y presenta una gran flexibilidad que la hace ideal para redes de diseño propio. En América funciona en la banda industrial, científica y médica (ISM) alrededor de los 915 MHz. Sin embargo, también existen muchas otras tecnologías LPWAN con arquitec- turas y protocolos propietarios, lo que dificulta alcanzar la interoperabilidad que se desea en el entorno IoT. El grupo de trabajo para la implementación de IPv6 sobre redes LPWAN (lpwan WG) perteneciente al Internet Engineering Task Force (IETF) se encuentra actualmente desarrol- lando un mecanismo de compresión y fragmentación de paquetes IPv6 para redes LPWAN denominado Static Context Header Compression (SCHC). El esquema de compresión se en- cuentra terminado, pero aún no ha sido implementado ni evaluado de manera oficial. En este trabajo se presenta una plataforma experimental para la implementación y eval- uación del mecanismo SCHC sobre una red LoRaWAN consistente en un nodo terminal Mi- crochip y un Radio Gateway (RG) de Everynet. En su desarrollo se han integrado múltiples y diversas herramientas del campo de las Telecomunicaciones y las Tecnologías de Información y Comunicación (ICT). La plataforma creada logra una implementación básica pero exitosa del esquema de com- presión de SCHC. Por medio de ella se ha llevado a cabo una evaluación preliminar del funcionamiento de SCHC, analizando el nivel de compresión logrado por el mecanismo para tres contextos de comunicación característicos de una red LPWAN. Los resultados obtenidos son positivos.

MA, Faculty of Humanities, University of the Witwatersrand, 2009 / Even though investigations of knowledge construction within CMC have been conducted (e.g. Gunawardena, Lowe and Anderson, 1997; Schellens & Valcke, 2004), no research has compared F2F communication and CMC in terms of the ability to solve complex tasks and to develop group cohesion. Group cohesion has been found to be vital for group cooperation and performance. Eight self-formed groups of 5 student participants each volunteered to participate in this study. Each group was required to solve two standardised, complex tasks in the same order. Student groups were randomly assigned to one of four medium combinations with two groups per combination. The combinations were: F2F communication for both tasks, CMC for both tasks, F2F communication for the first task and CMC for the second task, and CMC for the first task and F2F communication for the second task. Measures of knowledge construction were taken using the IAM (Gunawardena et al., 1997), group cohesion (assessed before and after the tasks) using the GAS (Evans & Jarvis, 1986), and a self-developed scale to assess satisfaction with the process and the outcome. The results showed that CMC groups produced significantly fewer contributions, and took a longer time to complete tasks, but there was no significant difference between the two mediums in terms of knowledge construction. The medium combination of F2F communication followed by CMC, achieved the least time to completion; the second most effective medium for knowledge construction, the greatest satisfaction with respect to group processes and the decision in the first task, and achieved a significantly higher level of post-manipulation group cohesion.

The growth of the World Wide Web has in large part been made possible by the technologies that power it. These are the Web servers and Web browsers that many take for granted. Each has evolved to support the changing needs of users of the WWW from simple static text to highly interactive and dynamic multimedia. The Web servers, in particular, have evolved into a spectrum of different technologies to support what are now known as Web applications. These are usually installed and accessed through a Web server. Security is a problem in Web server environments and therefore the Web servers are usually run as an un-privileged user. Performance is another problem as some of these technologies require re-initialization of the execution environment with every subsequent request. These security and performance shortcomings have been dealt with by numerous Web application technologies. Most of these technologies are language-centric and seek solutions to the security and performance shortcomings independently of each other. The universal Web application server is proposed as an alternative solution addressing the security, language dependence and performance shortcomings of existing technologies. It has support for multiple authors in a secure environment with support for multiple implementation technologies (languages) using persistent interpreters to enhance performance. Test results from the performance evaluation show that the introduction of the layers of processing contributes a small percentage to the total request processing time and that the universal Web application server can perform comparably to other Web application servers. Tests with twenty users also showed that packaging and deploying Web applications in the universal Web application server is an easy and viable approach. Moreover, the installation of PhpBB2 in the universal Web application server demonstrates that it can be used with realistic Web applications. A universal Web application server that provides an efficient, secure and language independent environment has been developed and thoroughly evaluated demonstrating that a Web application server that addresses the shortcomings of existing technologies is feasible.