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The emergence of Bluetooth as a wireless network solution assists in bringing together multiple technologies in different sectors and provides rapid interconnections to form a network paradigm. Typically, up to 8 Bluetooth devices can form a centralized network, called a piconet, controlled by a master node, which allocates transmission slots to all other nodes (slaves) in the piconet. However, the structure of inter-piconet connection: called the scatternet is not defined in the Bluetooth Specification. To develop a new scatternet structure, many challenges such as topology formation, intra and inter-piconet scheduling and packet routing are considered. The thesis addresses these critical issues based on the scatternet formation using Bluetooth. The scatternet, presented in this thesis, employs a tree hierarchy structure formation with a Leader root of three hierarchies. Within the scatternet, the new concept exploits clock and frequency synchronization for all new piconets creation. This synchronization prevents interferences and the need for guard time while switching piconet. Thus enabling a device to switch from one piconet to another at every slot. Furthermore, an innovative intra-piconet design is proposed to improve QoS within Bluetooth piconet. By exploiting the device queue status, the scheme defines a predictable polled sequence, and an adaptive traffic allocation. This offers a better fairness, and a significant power reduction when compared to the conventional Round Robin scheme. Moreover, with the perfect scatternet synchronization, the devices switch to other piconets to transmit data and, within one slot time, return to the initial piconet before the next predicted poll time exchange occurs. This considerably improves the traffic data transfer, especially for a significant number of devices present within the area. In addition, a new routing process is developed in this thesis, which facilitates communication within the scatternet. From the scatternet tree hierarchy position, a new addressing node routing is proposed to keep the overhead network low, and guarantees that any packet forwarded reaches its destination. The performance of the new scatternet is evaluated for each scatternet phase, through a Matlab simulation program, and the significant improvement of Bluetooth QoS achieved through the proposed approach is fully demonstrated. This thesis also presents a primary implementation of the scatternet concept using a dedicated Bluetooth hardware system.

Electronic services are emerging as the de-facto enabler of interaction interoperability across organization boundaries. Cross-organizational interactions are often "choreographed", i.e. specified by a messaging protocol from a global point of view independent of the local view of each interacting organization. Local requirements motivating an interaction as well as the global contextual requirements governing the interaction inevitably evolve over time, requiring adaptation of the corresponding interaction protocol. Adaptation of an interaction protocol must ensure the satisfaction of both sets of interaction requirements while maintaining consistency between the global view and the local views of an interaction specification. Such adaptation is not possible with the current state-of-the-art representations of choreographed interactions, as they capture only operational messaging specifications detached from both local organizational requirements as well as global contextual requirements. This thesis presents three novel contributions that tackle adaptation of choreographed interaction protocols: an automated technique for deriving an interaction protocol from requirements, a formalization of consistency between local and global views, and a framework for guiding the adaptation of a choreographed interaction. A choreographed interaction is specified using models of organizational requirements motivating the interaction. We employ the formal semantics embedded in requirements models to automatically derive an interaction protocol. We propose a framework for relating the global and local views of interaction specification and maintaining consistency between them. We develop a metamodel for interaction specification, from which we enumerate adaptation operations. We build a catalogue that provides guidance on performing each operation and propagating changes between the global and local views. These contributions are evaluated using examples from the literature as well as a real-world case study.

The ever growing Internet Protocol (IP) traffic driven by both consumer and business applications pose a fundamental challenge for network operators. Optical networks offering terabyte capacity and advanced switching capability is at the forefront of transport technology. As optical networks and data traffic proliferate there is a growing need to scale cost effectively and allow for multiple switching technologies. Addressing this, the G.709 Optical Transport Network (OTN) combined with the intelligence of the Generalised Multi Protocol Label Switching (GMPLS) control plane is identified to reduce transport costs and deliver enhanced network and performance management functions. Connections are established using GMPLS suite of protocols namely routing, signaling and the Path Computation Element (PCE). The conventional wavelength resource reservation mechanism in the Optical Channel (OCh) layer is stud- ied and shortcomings identified. Two distributed wavelength resource reservation algorithms that improve end-to-end wavelength allocation are proposed and offer significant network blocking performance improvement. Further, the Resource Reservation Protocol with Traffic Engineering (RSVP- TE) / PCE wavelength reservation is extended to the newly defined Optical channel Data Unit (ODU) digital layer to provision at sub-wavelength granularity. Network blocking performance, rough estimates of unit cost and wavelength utilisation in comparison with OCh layer are analysed showing improved network blocking performance and wavelength utilisation at the expense of increased cost unit. Also at higher transmission bit rates of 40Gbps and beyond, it is inefficient to provision light paths without taking into consideration the optical performance requirements of the client signal. To demonstrate Impairment-Aware (lA) wavelength resource reservation, the conventional RSVP- TE and best performing proposed algorithm are adapted for 10/ 40 Gbps client signals and network blocking performance is observed. Further, hardware-accelerated control plane functions to overcome challenges posed by overhead processing for short-lived connections in dynamic high-speed networks is discussed.

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This thesis is concerned with the link layer design of indoor (IrDA) and outdoor infrared links, as well as the performance of the higher layers of two major Wireless Personal Area Network (WPAN) technologies: IrDA and Bluetooth. Recent advancesin wireless technology have made it possible to put networking technology into small portable devices. During the past few years, WPAN technologies have been the subject of a tremendous growth both in research and development. Although many studies have been conducted on wireless links to address different issues on physical and link layers, wireless communications are still characterised by high error rates becauseof the frequently changing medium. On the other hand, performance studies of the higher layers are also very important. In this thesis, for the first time, a comprehensivestudy of the interactions betweenthe higher and the lower protocol layers of IrDA and Bluetooth has been carried out to improve the overall system performance. Mathematical models for the link layers are introduced for the infrared systems: infrared data association (IrDA) and free space optics (FSO). A model for the IrDA (indoor infrared) link layer is developed by considering the presence of bit errors. Based on this model, the effect of propagation delay on the link through put is investigated. An optimization study is also carried out to maximize the link throughput. FSO (outdoor infrared) links are often characterized by high speed and long link distance. A mathematical model for the FSO link layer is also developed. Significant improvement of the link throughput is achieved by optimizing the link parameters. Based on the link layer model, the performance of the IrDA higher layers (transport, session and application layers) is investigated. First, a mathematical model of TinyTP (transport protocol) is elaborated and subsequently verified by simulations. The effects of multiple connections and available buffer size are investigated. The throughput at the TinyTP level is optimized for different buffer sizes. Subsequently, the session layer, including Object Exchange (OBEX) and IrDA Burst (IrBurst) protocols, is studied and modelled. The derived mathematical model is verified by simulation results. A set of protocol parameters and hardware selection guidelines is proposed to optimize the overall system performance while also keeping the hardware requirementto a minimum. Finally, two rapidly developing IrDA applications, IrDA financial messaging(IrFM) and IrDA simple connection (IrSC), are studied. IrFM is investigated by comparison to other digital payment technologies, while the performance of IrSC is compared in two different technical approaches. In order to improve the throughput and minimize the transmission delay for the Bluetooth data applications, a systematic analysis is carried out for the Bluetooth Logical Link Control and Adaptation Layer Protocol (L2CAP). L2CAP is layered above the Bluetooth link layer (Baseband) and is essential to Bluetooth data applications. A simple and intuitive mathematical model is developed to derive simple equations for the L2CAP throughput and the average packet delay. The derived throughput equation, which is validated by simulations, takes into account bit errors as well as packet retry limits. Finally, a number of easy-to-implement performance enhancement schemes are proposed, including the optimum use of the protocol parameters.

In recent years there has been a marked growth in the use of wireless cellular telephones, PCs and the Internet. This proliferation of information technology has hastened the advent of wireless networks which aim to increase the accessibility and reach of communications devices. Ambient Intelligence (Ami) is a vision of the future of computing in which all kinds of everyday objects will contain intelligence. To be effective, Ami requires Ubiquitous Computing and Communication, the latter being enabled by wireless networking. The IEEE's 802.11 task group has developed a series of radio based replacements for the familiar wired ethernet LAN. At the same time another IEEE standards task group, 802.15, together with a number of industry consortia, has introduced a new level of wireless networking based upon short range, ad-hoc connections. Currently, the most significant of these new Wireless Personal Area Network (WPAN) standards is Bluetooth, one of the first of the enabling technologies of Ami to be commercially available. Bluetooth operates in the internationally unlicensed Industrial, Scientific and Medical (ISM) band at 2.4 GHz. unfortunately, this spectrum is particularly crowded. It is also used by: WiFi (IEEE 802.11); a new WPAN standard called Zig- Bee; many types of simple devices such as garage door openers; and is polluted by unintentional radiators. The success of a radio specification for ubiquitous wireless communications is, therefore, dependant upon a robust tolerance to high levels of electromagnetic noise. This thesis addresses the optimisation of low power WPANs in this context, with particular reference to the physical layer radio specification of the Bluetooth system.

The initial rapid expansion of the Internet, in terms of complexity and number of hosts, was followed by an increased interest in its overall parameters and the quality the network offers. This growth has led, in the first instance, to extensive research in the area of network monitoring, in order to better understand the characteristics of the current Internet. In parallel, studies were made in the area of protocol performance modelling, aiming to estimate the performance of various Internet applications. A key goal of this research project was the analysis of current Internet traffic performance from a dual perspective: monitoring and prediction. In order to achieve this, the study has three main phases. It starts by describing the relationship between data transfer performance and network conditions, a relationship that proves to be critical when studying application performance. The next phase proposes a novel architecture of inferring network conditions and transfer parameters using captured traffic analysis. The final phase describes a novel alternative to current TCP (Transmission Control Protocol) models, which provides the relationship between network, data transfer, and client characteristics on one side, and the resulting TCP performance on the other, while accounting for the features of current Internet transfers. The proposed inference analysis method for network and transfer parameters uses online nonintrusive monitoring of captured traffic from a single point. This technique overcomes limitations of prior approaches that are typically geared towards intrusive and/or dual-point offline analysis. The method includes several novel aspects, such as TCP timestamp analysis, which allows bottleneck bandwidth inference and more accurate receiver-based parameter measurement, which are not possible using traditional acknowledgment-based inference. The the results of the traffic analysis determine the location of the eventual degradations in network conditions relative to the position of the monitoring point. The proposed monitoring framework infers the performance parameters of network paths conditions transited by the analysed traffic, subject to the position of the monitoring point, and it can be used as a starting point in pro-active network management. The TCP performance prediction model is based on the observation that current, potentially unknown, TCP implementations, as well as connection characteristics, are too complex for a mathematical model. The model proposed in this thesis uses an artificial intelligence-based analysis method to establish the relationship between the parameters that influence the evolution of the TCP transfers and the resulting performance of those transfers. Based on preliminary tests of classification and function approximation algorithms, a neural network analysis approach was preferred due to its prediction accuracy. Both the monitoring method and the prediction model are validated using a combination of traffic traces, ranging from synthetic transfers/environments, produced using a network simulator/emulator, to traces produced using a script-based, controlled client and uncontrolled traces, both using real Internet traffic. The validation tests indicate that the proposed approaches provide better accuracy in terms of inferring network conditions and predicting transfer performance in comparison with previous methods. The non-intrusive analysis of the real network traces provides comprehensive information on the current Internet characteristics, indicating low-loss, low-delay, and high-bottleneck bandwidth conditions for the majority of the studied paths. Overall, this study provides a method for inferring the characteristics of Internet paths based on traffic analysis, an efficient methodology for predicting TCP transfer performance, and a firm basis for future research in the areas of traffic analysis and performance modelling.

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