Mobile phones are increasingly becoming tools for social interaction. As more phones come equipped with location tracking capabilities, capable of collecting and distributing personal information (including location) of their users, user control of location information and privacy for that matter, has become an important research issue. This research first explores various techniques of user control of location in location-based systems, and proposes the re-conceptualisation of deception (defined here as the deliberate withholding of location information) from information systems security to the field of location privacy. Previous work in this area considers techniques such as anonymisation, encryption, cloaking and blurring, among others. Since mobile devices have become social tools, this thesis takes a different approach by empirically investigating first the likelihood of the use of the proposed technique (deception) in protecting location privacy. We present empirical results (based on an online study) that show that people are willing to deliberately withhold their location information to protect their location privacy. However, our study shows that people feel uneasy in engaging in this type of deception if they believe this will be detected by their intended recipients. The results also suggest that the technique is popular in situations where it is very difficult to detect that there has been a deliberate withholding of location information during a location disclosure. Our findings are then presented in the form of initial design guidelines for the design of deception to control location privacy. Based on these initial guidelines, we propose and build a deception-based privacy control model. Two different evaluation approaches are employed in investigating the suitability of the model. These include; a field-based study of the techniques employed in the model and a laboratory-based usability study of the Mobile Client application upon which the DPC model is based, using HCI (Human Computer Interaction) professionals. Finally, we present guidelines for the design of deception in location disclosure, and lessons learned from the two evaluation approaches. We also propose a unified privacy preference framework implemented on the application layer of the mobile platform as a future direction of this thesis.

The infonnation' heterogeneity that arises from the autonomy of peers is a major problem for sharing infonnation in peer-to-peer (P2P) systems. This problem is hugely complicated by the dynamic and scalable natures of these systems. Many approaches have been proposed for infonnation sharing in P2P systems with heterogeneous p~ers. I have been particularly interested in dynamic ontology matching and integration in addressing this issue. However most ontology matching and integration approaches are either semi automatic, requiring final user judgement or not accurate enough to be used without human intervention. I am confident that in this research I have successfully addressed these issues.I have developed an integration model with layered structure for schema, ontologies and mal?pings/or Data. and Knowledge Sharing Peer to Peer (DAKSIP2P) systems. A representation scheme for ontologies has been presented with a set of rules to avoid conflicts that cannot be handled without human input. Within this representation scheme, a dynamic ontology matching and integration algorithm has been produced to match and integrate peer and coalition ontologies.

No description available.

No description available.

The aim of this research is to improve routing fault tolerance in Mobile Ad hoc Networks (MANETs) by optimising mUltipath routing in a well-studied reactive and single path routing protocol known as Ad hoc On-demand Distance Vector (AODV). The research also aims to prove the effect of varying waiting time of Route Reply (RREP) procedure and utilising the concept of efficient routes on the performance of multipath extensions to AODV. Two novel multipath routing approaches are developed in this thesis as new extensions to AODV to optimise routing overhead by improving Route Discovery Process (RDP) and Route Maintenance Process (RMP) of multipath AODV. The first approach is a Iinkdisjoint multipath extension called 'Thresho)d efficient Routes in multipath AODV' (TRAODV) that optimises routing packets ~verhead by improving the RDP of AODV which is achieved by detecting the waiting time required for RREP procedure to receive a threshold number of efficient routes. The second approach is also a link-disjoint mUltipath extension called 'On-demand Route maintenance in Multipath AoDv' (ORMAD) which is an extension to TRAODV that optimises routing packets and delay overhead by improving the RMP of TRAODV. ORMAD applies the concepts of threshold waiting time and efficient routes to both phases RDP and RMP. It also applies RMP only to efficient routes which are selected in the RDP and when a route fails, it invokes a local repair procedure between upstream and downstream nodes of the broken link. This mechanism produces a set of alternative subroutes with less number of hops which enhances route efficiency and consequently minimises the routing overhead. TRAODV and ORMAD are implemented and evaluated against two existing multipath extensions to,AODV protocol and two traditional multipath protocols. The existing extensions to AODV used in the evaluation are a well-known protocol called Ad hoc On-demand Multipath Distance Vector (AOMDV) and a recent extension called Multiple Route AODV (MRAODV) protocol which is extended in this thesis to the new approach TRAODV while the traditional multipath protocols used in the evaluation are Dynamic Source Routing (DSR) and Temporally Ordered Routing Algorithm (TORA). Protocols are implemented using NS2 and evaluated under the same simulation environment in terms of four performance metrics; packet delivery fraction, average end-to-end delay, routing packets overhead, and throughput. Simulation results of TRAODV evaluation show that the average number of routes stored in a routing table of MRAODV protocol is always larger than the average number of routes in TRAODV. Simulation results show that TRAODV reduces the overall routing packets overhead compared to both extensions AOMDV and MRAODV, especially for large network size and high mobility. A vital drawback of TRAODV is that its performance is reduced compared to AOMDV and MRAODV in terms of average end-to-end delay. Additionally, TORA still outperforms TRAODV and the other extensions to AODV in terms of routing packets overhead. In order to overcome the drawbacks of TRAODV, ORMAD is developed by improving the RDP of TRAODV. The performance of ORMAD is evaluated against RREP waiting time using the idea of utilising the efficient routes in both phases RDP and RMP. Simulation results of ORMAD show that the performance is affected by varying the two RREP waiting times of both RDP and RMP in different scenarios. As shown by the simulation results, applying the short and long waiting times in both phases tends to less performance in terms of routing packets overhead while applying the moderate waiting times tends to better performance. ORMAD enhances routing packets overhead and the average end-to-end delay compared to TRAODV, especially in high mobility scenarios. ORMAD has the closest performance to TORA protocol in terms of routing packets overhead compared to ~M~a~M~OW . Relevant concepts are formalised for ORMAD approach and conducted as an analytical model in this thesis involving the\vhole process of multipath routing in AODV extensions. ORMAD analytical model describes how the two phases RDP and RMP interact with each other with regard to two performance metrics; total number of detected routes and Route Efficiency.

Voice over Internet Protocol (VoIP) is an active area of research in the world of communication. The high revenue made by the telecommunication companies is a motivation to develop solutions that transmit voice over other media rather than the traditional, circuit switching network. However, while IP networks can carry data traffic very well due to their besteffort nature, they are not designed to carry real-time applications such as voice. As such several degradations can happen to the speech signal before it reaches its destination. Therefore, it is important for legal, commercial, and technical reasons to measure the quality of VoIP applications accurately and non-intrusively. Several methods were proposed to measure the speech quality: some of these methods are subjective, others are intrusive-based while others are non-intrusive. One of the non-intrusive methods for measuring the speech quality is the E-model standardised by the International Telecommunication Union-Telecommunication Standardisation Sector (ITU-T). Although the E-model is a non-intrusive method for measuring the speech quality, but it depends on the time-consuming, expensive and hard to conduct subjective tests to calibrate its parameters, consequently it is applicable to a limited number of conditions and speech coders. Also, it is less accurate than the intrusive methods such as Perceptual Evaluation of Speech Quality (PESQ) because it does not consider the contents of the received signal. In this thesis an approach to extend the E-model based on PESQ is proposed. Using this method the E-model can be extended to new network conditions and applied to new speech coders without the need for the subjective tests. The modified E-model calibrated using PESQ is compared with the E-model calibrated using i ii subjective tests to prove its effectiveness. During the above extension the relation between quality estimation using the E-model and PESQ is investigated and a correction formula is proposed to correct the deviation in speech quality estimation. Another extension to the E-model to improve its accuracy in comparison with the PESQ looks into the content of the degraded signal and classifies packet loss into either Voiced or Unvoiced based on the received surrounding packets. The accuracy of the proposed method is evaluated by comparing the estimation of the new method that takes packet class into consideration with the measurement provided by PESQ as a more accurate, intrusive method for measuring the speech quality. The above two extensions for quality estimation of the E-model are combined to offer a method for estimating the quality of VoIP applications accurately, nonintrusively without the need for the time-consuming, expensive, and hard to conduct subjective tests. Finally, the applicability of the E-model or the modified E-model in measuring the quality of services in Service Oriented Computing (SOC) is illustrated.

No description available.

In this thesis new methods are presented to achieve performance enhancement in wireless cooperative networks. In particular, techniques to improve transmission rate, mitigate asynchronous transmission and maximise end-to-end signal-to-noise ratio are described. An offset transmission scheme with full interference cancellation for a two-hop synchronous network with frequency flat links and four relays is introduced. This approach can asymptotically, as the symbol block size increases, achieve maximum transmission rate together with full cooperative diversity provided the destination node has multiple antennas. A novel full inter-relay interference cancellation method that also achieves asymptotically maximum rate and full cooperative diversity is then designed which only requires a single antenna at the destination node. Extension to asynchronous networks is then considered through the use of orthogonal frequency division multiplexing (OFDM) type transmission with a cyclic prefix, and interference cancellation techniques are designed for situations when synchronization errors are present in only the second hop or both the first and second hop. End-to-end bit error rate evaluations, with and without outer coding, are used to assess the performance of the various offset transmission schemes. Multi-relay selection methods for cooperative amplify and forward type networks are then studied in order to overcome the degradation of end-to-end bit error rate performance in single-relay selection networks when there are feedback errors in the destination to relay node links. Outage probability analysis for two and four relay selection is performed to show the advantage of multi-relay selection when no interference occurs and when adjacent cell interference is present both at the relay nodes and the destination node. Simulation studies are included which support the theoretical expressions. Finally, outage probability analysis of a cognitive amplify and forward type relay network with cooperation between certain secondary users, chosen by single and multi-relay (two and four) selection is presented. The cognitive relays are assumed to exploit an underlay approach, which requires adherence to an interference constraint on the primary user. The relay selection is performed either with a max-min strategy or one based on maximising exact end-to-end signal-to-noise ratio. The analyses are again confirmed by numerical evaluations.

Wireless Sensor Networks (WSNs) are expected to be a new, revolutionary technology in the same manner as the Internet. This is due to their special characteristics such as low power consumption, ad hoc operation, self-maintenance and many other features. These special characteristics help in reducing the costs of network manufacture and implementation which extends their applications in a number of areas such as health and military services. Unfortunately, network resources such as memory, power and processing capacity constitute a serious constraint. In addition, they reduce the immunity of the network against external and internal impacts (such as electromagnetic interference) which make sensor node operations frequently deviate from the norm, degrading the WSN's functionality. In some cases the data collected by the network becomes unreliable; the monitoring of the phenomenon may even fail. To ensure the reliability of the network, several tools have been proposed to detect and isolate these deviations but most use relatively high levels of resources. In certain circumstances these state-of-the-art tools are unable to avoid the instant impact of data deviations on the accuracy of the collected data and on the network's functionality. This thesis overcomes these drawbacks by proposing a new, real-time, low resources usage, distributed performance algorithm that will monitor the accuracy of collected data and network functionality in large scale dense deployed WSNs. In order to achieve this, we have used the spatio-temporal correlation between the measurements of the neighbour nodes in large scale dense deployed WSNs. This correlation arises due to near proximity (of the nodes) and/or the slow characteristics' change of monitored phenomenon. The proposed algorithm has been tested via simulation experiments using different simulated and real world application data sets. Moreover, it has been tested on a real network testbed with Mote sensors using continuous reporting and event-driven applications. The results from these experiments showed a high rate of detection of changes in the reliability levels of data and in network performance. They also showed a high level of accuracy in terms of the detection of sensor faults. This, however, comes alongside certain limitations because of the use of simple passive analysis with the proposed algorithm.

With the growth of wireless networks such as sensor networks and mesh networks, the challenges of sustaining higher data rates and coverage, coupled with requirement for high quality of services, need to be addressed. The use of spatial diversity proves to be an attractive option due to its ability to significantly enhance network performance without additional bandwidth or transmission power. This thesis proposes the use of cooperative wireless relays to improvise spatial diversity in wireless sensor networks and wireless mesh networks. Cooperation in this context implies that the signals are exchanged between relays for optimal performance. The network gains realised using the proposed cooperative relays for signal forwarding are significantly large, advocating the utilisation of cooperation amongst relays. The work begins with proposing a minimum mean square error (MMSE) based relaying strategy that provides improvement in bit error rate. A simplified algorithm has been developed to calculate the roots of a polynomial equation. Following this work, a novel signal forwarding technique based on convex optimisation techniques is proposed which attains specific quality of services for end users with minimal transmission power at the relays. Quantisation of signals passed between relays has been considered in the optimisation framework. Finally, a reduced complexity scheme together with a more realistic algorithm incorporating per relay node power constraints is proposed. This optimisation framework is extended to a cognitive radio environment where relays in a secondary network forward signals without causing harmful interferences to primary network users.