The phenomenal emergence of several heterogeneous wireless networks and technologies has allowed users to have access IP services anywhere at anytime from any network with whatever terminal they use. This computing platform has also been driven by the rapid evolution of mobile devices that are equipped with multiple network interfaces and the development of IP based applications. One of the challenging tasks with this Next-Generation Networks (NGN) computing platform is service continuity when users roam around different wireless networks e.g. Wi-Fi, Bluetooth and Cellular networks. This challenge is elevated more when dealing with applications that distribute time continuous data with stringent Quality of Service (QoS) requirements. One of the adaptation methods to ensure service continuity by minimizing flow interruptions when users are mobile is session handoff. The main contribution of the thesis is to present a handoff support system which implements a handoff decision engine using a Multi-Criteria Decision Making (MCDM) method based on a Bayesian Belief Network (BBN) and a handoff execution procedure based on buffering and doublecasting techniques. The handoff support system is built around the following features: 1) It utilises a proxy-based middleware architecture, 2) It uses a BBN based MCDM for handoff decision, 3) It is able to represent the full context information which represents the execution environment, 4) It is able to perform decision making under both certainty and uncertainty, 5) It is able to decide correctly on the target network under dynamic context, 6) It performs decision making in the midst of conflicting, interdependent and constraint criteria, and 7) It uses a profile-based handoff decision to offer personalisation to users. The experimental results showed that when compared with Analytical Hierarchy Process (AHP), the handoff decision method based on BBN performs better on: 1) Modelling of the handoff decision problem and the full representation of the context information, 2) Decision making under uncertainty, 3) Modelling of constraints and interdependent criteria and 4) Support for user preferences. When evaluating the handoff execution, further results revealed that the underlying handoff management strategies provide service continuity by minimising handoff latency and packet losses.

The challenge of parking management has increasingly posed the need for smart solutions. Motorists in today’s busy world seek the best option in locating available parking points. The need for an efficient parking system stems from increased congestion, motor vehicle pollution, driver frustration and fatigue to mention but a few. This study was conducted at a time when the world was experiencing a financial crisis and more than ever motorists needed intelligent parking systems to reduce the cost of gas spent driving around to find parking. Indeed, the time spent driving around would be beneficial if used to do work that would put one at an advantage in the credit recession. The study was also conducted at a time when South Africa was preparing to host the 2010 soccer world cup. In the preparation to manage motor vehicle congestion, this study was a viable solution to manage the expected challenge of parking. This study presents the design and illustrates the performance of an intelligent parking system based on an integrated architecture where (1) Wireless Sensor networks (WSNs) using Small Programmable Object Technology (SPOT) motes are launched into parking places to monitor the activity of the parking area through light intensity sensing and (2) the sensed information is gathered and channeled through a gateway into databases used for parking space visualization and information dissemination over the World Wide Web technology and mobile devices via a Multi Protocol label Switching (MPLS) network. Using an illustrative simulation model of a small parking system built around a new generation of SUNspot motes, the study demonstrates how a real life smart parking system can be deployed to benefit motorists in today’s busy World and serves as a foundation to future work on how this emerging generation of motes can be used to provide better ways of finding parking.

IEEE 802.16 wireless metropolitan area network (WMAN) technology is an improvement on its wireless local area network (WLAN) counterpart, namely IEEE 802.11, in that it provides longer range and higher bandwidth capabilities. More importantly, it specifies a connection-oriented medium access control layer (MAC) and scheduling services to support quality of service (QoS) in IEEE 802.16 networks. However, in the standard, scheduling and connection admission control (CAC) mechanisms are left unspecified, leaving this for network operators to decide. This allows implementers to create market and performance advantages, making it a rich field of research and performance analysis. Typically, researchers studying scheduling and admission control in such wireless networks consider these resource and connection management (RaCM) algorithms in isolation: They investigate (1) schedulers while fixing the admission control processes or using static connection scenarios and (2) admission controllers while fixing the scheduling processes. We hypothesize that there exists an interdependent relationship between RaCM components which is an essential aspect to cross-layer inter-RaCM algorithm design. In order to prove our hypothesis that you cannot consider the scheduler and the CAC in isolation, where it involves the performance of IEEE 802.16 networks, we require a performance model: Analytic modelling is an ideal solution but the system is far too complex. Experimental test beds are expensive, making hardware experimentation another impractical solution. The only other feasible solution is simulation. General simulation environments, such as NS2 and OMNeT++, offer IEEE 802.16 libraries and some degree of development community support. However, for several reasons, as we shall discuss, we developed our own deep simulator – a discrete-event simulation model of an IEEE vertically integrated wireless Internet scenario. In particular, we concentrate our effort on the fixed IEEE 802.16 WMAN (802.16-2004), simulating admission control and scheduling processes exactly. Both the machine model and workload model play an integral part in obtaining useful performance data: Our machine model includes particular MAC and physical layer (PHY) functions of the standard, such as framing, adaptive modulation and coding, fragmentation, and so on, as well as the admission control and scheduling algorithms. For the workload model, we developed a Markov Modulated Arrival Process (MMAP) by combining existing traffic models of different Internet applications, such as VoIP, P2P, etc. Each application is associated with one of the IEEE 802.16 traffic categories (TCs). The MMAP generates both connection– and packet level data, maintaining traffic volume ratios, as reported by previous studies of Internet application traffic volumes. Performance metrics of delay and jitter are calculated per TC connection. This allows a comparison of the quality of experience (QoE) of an individual user for the duration of a connection. At the connection level, we report the blocking probability. By simulating the RaCM with various admission control and scheduling configurations, we were able to show that there is a significant difference in performance when using different CAC and scheduler combinations. Although hardly surprising, it is still proof that one cannot simply consider either in isolation, as is done in various performance studies reported in the literature. This interdependent relationship should be considered when designing complementary admission control and scheduling algorithms.

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.

No description available.

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.