The popularity of IP services is increasing and the demand for managing traffic with different QoS classes has become more challenging. The stability of the system is affected by the rate of voice traffic. Mobility allows users to be connected at all time where handover may occur as it is not always possible to be connected to the same base station. Mobility and handover cause severe interference, which affects overall throughput and capacity of the system. The system requires greater capacity with more coverage area. This study deals with the impact of user mobility on voice quality in IP based application in a 3G Network. The aim is to improve the system performance in mixed traffic environment. A mathematical model is used to analyse the impact of using different type of coder on packet end-to-end delay and packet loss. The simulation results indicate that types of coder affect the system performance. Application of scheduling based on weight and load balancing technique can improve the system performance. The deployment of scheduling based on weight and a load balancing technique have been investigated to reduce the end-to-end delay and to improve overall performance in mixed traffic environment. The results under different conditions are analysed and it is found that by applying scheduling scheme, the quality of voice communication can be improved. In addition, load balancing technique can be used to improve the performance of the system. Apart from the decrease in delay, the technique can increase the capacity of the system and the overall stability of the system can be further improved. Finally, network security is another important aspect of network administration. Security policies have to be defined and implemented so that critical sections of the network are protected against unwarranted traffic or unauthorized personnel. The impact of implementing IPSec has been tested for voice communication over IP in a 3G network. Implementing the security protocol does not significantly degrade the performance of the system.

The research community has produced a great deal of work in recent years in the areas of IP, layer 2 and connection-chain traceback. We collectively designate these as message traceback systems which, invariably aim to locate the origin of network data, in spite of any alterations effected to that data (whether legitimately or fraudulently). This thesis provides a unifying definition of spoofing and a classification based on this which aims to encompass all streams of message traceback research. The feasibility of this classification is established through its application to our literature review of the numerous known message traceback systems. We propose two layer 2 (L2) traceback systems, switch-SPIE and COTraSE, which adopt different approaches to logging based L2 traceback for switched ethernet. Whilst message traceback in spite of spoofing is interesting and perhaps more challenging than at first seems, one might say that it is rather academic. Logging of network data is a controversial and unpopular notion and network administrators don't want the added installation and maintenance costs. However, European Parliament Directive 2006/24/EC requires that providers of publicly available electronic communications networks retain data in a form similar to mobile telephony call records, from April 2009 and for periods of up to 2 years. This thesis identifies the relevance of work in all areas of message traceback to the European data retention legislation. In the final part of this thesis we apply our experiences with L2 traceback, together with our definitions and classification of spoofing to discuss the issues that EU data retention implementations should consider. It is possible to 'do logging right' and even safeguard user privacy. However this can only occur if we fully understand the technical challenges, requiring much further work in all areas of logging based, message traceback systems. We have no choice but to dance with the devil.

Web services encapsulate some well-defined functionality such as data storage, computation or a business process. An organization can delegate responsibility for the provision of a Web service to another organization with the formation of a Service Provisioning Relationship (SPR). Such relationships enable organizations to specialize in the provision of those Web services for which they have a comparative advantage, and to outsource responsibility for any other functionality on which they are dependent to the Web services provided by other organizations. This specialization can lead to significant increases in organizational efficiency. The scale of such increases is determined by the extent to which the presence of uncertainty in the Quality of Service (QoS) can be addressed by the organizations in the SPR. The requester of a Web service can be uncertain of the willingness and ability of the provider to provision a Web service with a certain QoS. The provider of a Web service can be uncertain of his ability to provision a Web service to each requester with a certain QoS. These uncertainties can endanger the economic viability of such relationships, and mitigate any increases in organizational efficiency. This thesis provides a number of key contributions to address these uncertainties in order to retain the economic viability of these relationships for both organizations. The key contributions are: an institutional framework for trust in SPRs, a structured language for the representation of a Service Level Agreement (SLA) as a contingent contract, and a theoretical and practical methodology for the creation of SLAs which are optimal with regard to the objectives of an organization.

Mobile Ad-hoc Networks (MANETs) allow deployment of mobile wireless devices or nodes in a range of environments without any fixed infrastructure and hence at a minimal setup cost. Broadcast support that assures a high coverage (i.e., a large fraction of nodes receiving a broadcast) is essential for hosting user applications, and is also non-trivial to achieve due to the nature of devices and mobility. We propose Encounter Gossip, a novel broadcast protocol, which holds minimal state and is unaware of network topology. Coverage obtained can be made arbitrarily close to 1 at a moderate cost of extra message tra c, even in partition-prone networks. Under certain simplifying assumptions, it is shown that a high coverage is achieved by making a total of O(n ln n) broadcasts, where n is the number of nodes, and the time to propagate a message is O(ln n). The e ect of various network parameters on the protocol performance is examined. We then propose modifications to minimise the number of redundant transmissions without compromising the achieved coverage. Two approaches are pursued: timer based and history based. The e ectiveness of each of these approaches is assessed through an extensive set of simulation experiments in the context of two mobility models. Specifically, we introduce a new heuristic alpha policy which achieves significant reduction in redundancy with negligible reduction in coverage. A generalisation to multiple broadcasts proceeding in parallel is proposed and the protocol is refined to reduce problems that can occur due to the effects of high mobility when transmitting a large number of messages. Finally, we implement and validate Encounter Gossip in the context of a real-life mobile ad-hoc network. All these investigations suggest that the protocol, together with the proposed modifications and re nements, is suited to MANETs of varying degrees of node densities and speeds.

This thesis presents the detailed investigation of the Ultra- Wideband (UWB) high speed short-range wireless communications. The research has thoroughly examined many unexplored sensitive issues such as waveform design, i.e., using high derivatives Gaussian functions to control the power spectral density (PSD) to avoid the interference, changeable pulse duration to meet the bandwidth requirements and anti-interference ability with both high Gaussian derivatives and M-band modulation of UWB systems. A general UWB channel model has been examined to analyze the sensitive parameters such as the signal synchronization, channel estimation and detection using simulation methods. This carried out a deep investigation of the correlation of the noise in the captured multi-path energy and then provided an improved maximal ratio (IMR) algorithm to evaluate the weights of the rake combiner in a dense multi-path indoor UWB channel. The simulation results shown IMR combine (when used with equalizer) may be considered better than others while using for UWB channel model (CM-l and CM-2), and has the similar performance as Minimum Mean Square Error (MMSE). MMSE is one of the well- performed algorithms but on the other hands it requires a complicated hardware design. In order to overcome the interference in multi-user UWB communication system, the multiple users UWB system model based-on the packets collision was tested using simulation of ad-hoc networks. It proved that the effects of varied users numbers and multiple user interference (MUI) processing are the key factors to overcome the system performance and suggested for use to guide the designers and planners of the UWB Ad-hoc networks. Also, the adverse effects of the synthesis interference of UWB devices on the other mobile and wireless communication systems and vice versa hav~~¥n explored while examining the existing UWB emission mask standards. The bit error ratio (BER) formula for the interfered UWB system was derived to demonstrate the relationship between the UWB anti-interference ability and its parameters. This examination revealed that adjusting the signal gain can improve the performance in terms of anti-interference capability. Finally, the results of all the above-mentioned investigations are presented and discussed to prove that emerging the high speed UWB Systems in the 4th G mobile systems and also their coexistence alongside the present and future wireless and mobile communication systems are possible in practice and also very advantageous.

With the ever-increasing complexity of sound synthesisers, there is a growing demand for automated parameter estimation and sound space navigation techniques. This thesis explores the potential for evolutionary computation to automatically map known sound qualities onto the parameters of frequency modulation synthesis. Within this exploration are original contributions in the domain of synthesis parameter estimation and, within the developed system, evolutionary computation, in the form of the evolutionary algorithms that drive the underlying optimisation process. Based upon the requirement for the parameter estimation system to deliver multiple search space solutions, existing evolutionary algorithmic architectures are augmented to enable niching, while maintaining the strengths of the original algorithms. Two novel evolutionary algorithms are proposed in which cluster analysis is used to identify and maintain species within the evolving populations. A conventional evolution strategy and cooperative coevolution strategy are defined, with cluster-orientated operators that enable the simultaneous optimisation of multiple search space solutions at distinct optima. A test methodology is developed that enables components of the synthesis matching problem to be identified and isolated, enabling the performance of different optimisation techniques to be compared quantitatively. A system is consequently developed that evolves sound matches using conventional frequency modulation synthesis models, and the effectiveness of different evolutionary algorithms is assessed and compared in application to both static and timevarying sound matching problems. Performance of the system is then evaluated by interview with expert listeners. The thesis is closed with a reflection on the algorithms and systems which have been developed, discussing possibilities for the future of automated synthesis parameter estimation techniques, and how they might be employed.

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The purpose of this research is to improve the performance of Mobile Ad hoc NETworks (MANET) by using simulation. A new self-positioning algorithm was proposed by which the mobile nodes can obtain their locations with and without the existence of Global Positioning System (GPS). This algorithm was integrated into a new routing protocol Location-Label Based Routing (LLBR) protocols. Unlike other location-based routing protocol, LLBR makes it possible to enhance without the aid of GPS, the routing performance using the local coordinates system. It was noticed that the mobility of mobile nodes could have significant influence on the performance of a network and the environment also must be considered carefully as MANET can be deployed anywhere. The need for a framework to better study MANET was identified. The research then moved on to develop an Environment-Aware Framework for the research of MANET. A new Environment-Aware Mobility (EAM) model in which the mobility of mobile nodes can be impacted by the environment was proposed, and two particular sub-models: the Route Mobility Model and the Hotspot Mobility Model targeted at road and hotspot environment, respectively were also proposed to show the flexibility of EAM. Two special mobile ad hoc networks, the RoadLamp-aided Inter-Vehicle Communication (IVC) system and the Bus-aided IVC system are proposed to help improve the performance of the deployed networks in city environments. A set of tools were developed to construct the environment, model the mobility of mobile nodes, visualise the movements and evaluate the performance of the network. The simulation results have shown that network performance can be enhanced by taking advantage of the self-positioning algorithm, the framework which takes the environment into account in simulation, enables more realistic MANET to be studied and evaluated and also proves that the environment must be carefully considered together with the mobility of mobile nodes in the research of MANET. To show the expandability of the framework, a mobility-concerned emulator was also introduced.

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