Since 2004, when the Long Term Evolution (LTE) was first proposed to be publicly available in the year 2009, a plethora of new characteristics, techniques and applications have been constantly enhancing it since its first release, over the past decade. As a result, the research aims for LTE-Advanced (LTE-A) have been released to create a ubiquitous and supportive network for mobile users. The incorporation of heterogeneous networks (HetNets) has been proposed as one of the main enhancements of LTE-A systems over the existing LTE releases, by proposing the deployment of small-cell applications, such as femtocells, to provide more coverage and quality of service (QoS) within the network, whilst also reducing capital expenditure. These principal advantages can be obtained at the cost of new challenges such as inter-cell interference, which occurs when different network applications share the same frequency channel in the network. In this thesis, the main challenges of HetNets in LTE-A platform have been addressed and novel solutions are proposed by using self-organising network (SON) management approaches, which allows the cooperative cellular systems to observe, decide and amend their ongoing operation based on network conditions. The novel SON algorithms are modelled and simulated in OPNET modeler simulation software for the three processes of resource allocation, mobility management and interference coordination in multi-tier macro-femto networks. Different channel allocation methods based on cooperative transmission, frequency reuse and dynamic spectrum access are investigated and a novel SON sub-channel allocation method is proposed based on hybrid fractional frequency reuse (HFFR) scheme to provide dynamic resource allocation between macrocells and femtocells, while avoiding co-tier and cross-tier interference. Mobility management is also addressed as another important issue in HetNets, especially in hand-ins from macrocell to femtocell base stations. The existing research considers a limited number of methods for handover optimisation, such as signal strength and call admission control (CAC) to avoid unnecessary handovers, while our novel SON handover management method implements a comprehensive algorithm that performs sensing process, as well as resource availability and user residence checks to initiate the handover process at the optimal time. In addition to this, the novel femto over macro priority (FoMP) check in this process also gives the femtocell target nodes priority over the congested macrocells in order to improve the QoS at both the network tiers. Inter-cell interference, as the key challenge of HetNets, is also investigated by research on the existing time-domain, frequency-domain and power control methods. A novel SON interference mitigation algorithm is proposed, which is based on enhanced inter-cell interference coordination (eICIC) with power control process. The 3-phase power control algorithm contains signal to interference plus noise ratio (SINR) measurements, channel quality indicator (CQI) mapping and transmission power amendments to avoid the occurrence of interference due to the effects of high transmission power. The results of this research confirm that if heterogeneous systems are backed-up with SON management strategies, not only can improve the network capacity and QoS, but also the new network challenges such as inter-cell interference can also be mitigated in new releases of LTE-A network.

O segmento das comunicações, já há alguns anos, vem passando por significativas transformações exigindo a interação entre ambientes tecnológicos convergentes heterogêneos, com qualidade na continuidade de serviços, para se manter competitivo, pois é este mercado que exige, constantemente, que mais recursos tecnológicos lhe sejam colocados à disposição. O ineditismo da proposta desenvolvida neste trabalho é a elaboração de um modelo para assegurar a continuidade da qualidade de serviço percebida pelo usuário final através de handover (ou handoff) vertical, o que caracteriza-se como uma necessidade de solução global, isto é, o modelo é genérico e independente da tecnologia, o que permite sua adoção em qualquer ambiente de rede existente aproveitando a capilaridade já disponível das redes legadas. É analisada também a situação na qual um usuário final esteja acessando simultaneamente serviços gerenciados por Provedores de Serviço distintos, o que conduz a duas situações possíveis: a) o usuário está acessando serviços distintos contratados a Provedores de Serviço diferentes; b) o usuário está acessando o mesmo serviço contratado a Provedores de Serviço distintos. Nesta última situação pode surgir a necessidade de disparar um processo de handover exigindo a decisão de qual dos Provedores o executará, de acordo com o SPHDA Service Providers Handover Decision Agreement. A metodologia adotada para o desenvolvido do modelo foi a RM-ODP - Reference Model for Open Distributed Processing, por abranger todos os aspectos técnicos e comerciais necessários à sua construção. / The sector of communications, for some years, has undergone significant changes requiring interaction between converging heterogeneous technology environments, with quality and continuity of services to stay competitive, because this market is that requires constantly more technological resources available. The novelty of the proposal developed in this work is the development of a model to ensure the continued quality of service perceived by end users via vertical handover (or handoff), which characterizes itself as a need for a global solution, i.e., the model is generic and technology independent, allowing its adoption in any network environment taking advantage of the capillary already available from legacy networks. It is also analyzed the situation in which an end user is simultaneously accessing services managed by different Service Providers, which leads to two possible situations: a) the user is accessing different services contracted to different Service Providers; b) the user is accessing the same service contracted to different Service Providers. In this last situation may be necessary to trigger a handover process requiring the decision of which the Providers shall execute it in accordance with the SPHDA - Service Providers Handover Decision Agreement. The methodology adopted for the model development was the RM-ODP - Reference Model for Open Distributed Processing, as it includes all technical and commercial aspects necessary for its construction.

With advances in wireless technology and mobile devices, the number of mobile users using multimedia services has increased significantly in recent years. Mobile devices can be connected and roam on heterogeneous wireless networks. The IEEE 802.21 group has designed a Media Independent Handover (MIH) standard to ensure seamless Vertical Handover (VHO) in heterogeneous networks. However, the standard currently depends on features of the network (e.g. the type of network and available bandwidth) to achieve seamless VHO. This approach is limited, as it does not consider how a Quality of Experience (QoE) can be provided and maintained for customers when delivering multimedia services in heterogeneous wireless networks. The aim of the project is to develop a novel QoE-driven VHO management framework for providing and maintaining an appropriate level of QoE of multimedia services as the mobile user’s actual requirements in heterogeneous wireless networks. A QoE-driven VHO algorithm is more efficient for maintaining this acceptable QoE of multimedia services than traditional network-based or QoS-based VHO algorithms. There are three main contributions during this project. Firstly, A thorough evaluation of the performance of voice and video services via Skype was carried out in terms of the QoE metric (i.e. MOS). This work identified the impact of video content and packet loss on the QoE metric for voice and video communication services over wireless networks. Secondly, a QoE-driven VHO algorithm was developed to provide and maintain an acceptable QoE of mobile video services for mobile users. Compared to a traditional network-based VHO algorithm, this algorithm can provide better QoE and maintain acceptable QoE. Lastly, the User-centric QoE-driven (UCQoE) VHO framework to provide satisfactory QoE of multimedia services according to the mobile user’s requirements. The framework allows users to set their own preferences (e.g. quality-guarantee or cost-free) and carry out VHO operations accordingly. The evaluation showed that the proposed framework can provide a better QoE for delivered video services than QoS-based and network-based VHO algorithms. Furthermore, the proposed framework can be used to avoid unnecessary cost of mobile data when the option of cost-free is preferred by the user. During this project, three international conference papers had been published and a journal paper has been submitted to IEEE Transactions on Mobile Computing. The main contribution-UCQoE VHO management framework can be developed to maintain QoE of all mobile services in the future.

The provision of ultra-safe healthcare relies upon investment in robust systems of work. The transition of care between healthcare providers has been shown to contribute significant risk to patients, so much so that the improvement in handover was listed as one of the top five priorities for the World Health Organisation in 2014. Current handover practices have been evaluated in medicine using numerous techniques on the qualitative – quantitative continuum. The systematic evaluation of published literature revealed a paucity of evidence in relation to the optimal transfer of patient care. As a consequence, the post-operative handover was evaluated by first undertaking semi-structured interviews of anaesthetic, recovery and surgical staff. Differences of opinion were discovered between professional groups involved in the post-operative handover. These differences have the potential to fuel inter-professional conflict. The handover process was seen as being vulnerable to the effects of outside agencies, with time pressure being most to blame. The post-operative handover was observed and a novel handover intervention was introduced, with the primary objective of reducing multi-tasking and improving information accuracy. The intervention combined education of handover error alongside standardisation of the process. The introduction of a bed-side aide memoire to separate the transfer of equipment from standardised information transfer was introduced with staff involvement. Prior to the introduction of the handover intervention, core information points such as the patient’s name and allergies were frequently omitted and the process was often beset with distraction from concomitant activities. Both of these factors improved following the introduction of the intervention. These findings support previous revelations in handover that transitions are frequently not optimised to reduce risk in the patient pathway. However, it is feasible to ameliorate this risk by introducing a low cost quality improvement intervention which aims to standardise what can otherwise be haphazard working practice.

O segmento das comunicações, já há alguns anos, vem passando por significativas transformações exigindo a interação entre ambientes tecnológicos convergentes heterogêneos, com qualidade na continuidade de serviços, para se manter competitivo, pois é este mercado que exige, constantemente, que mais recursos tecnológicos lhe sejam colocados à disposição. O ineditismo da proposta desenvolvida neste trabalho é a elaboração de um modelo para assegurar a continuidade da qualidade de serviço percebida pelo usuário final através de handover (ou handoff) vertical, o que caracteriza-se como uma necessidade de solução global, isto é, o modelo é genérico e independente da tecnologia, o que permite sua adoção em qualquer ambiente de rede existente aproveitando a capilaridade já disponível das redes legadas. É analisada também a situação na qual um usuário final esteja acessando simultaneamente serviços gerenciados por Provedores de Serviço distintos, o que conduz a duas situações possíveis: a) o usuário está acessando serviços distintos contratados a Provedores de Serviço diferentes; b) o usuário está acessando o mesmo serviço contratado a Provedores de Serviço distintos. Nesta última situação pode surgir a necessidade de disparar um processo de handover exigindo a decisão de qual dos Provedores o executará, de acordo com o SPHDA Service Providers Handover Decision Agreement. A metodologia adotada para o desenvolvido do modelo foi a RM-ODP - Reference Model for Open Distributed Processing, por abranger todos os aspectos técnicos e comerciais necessários à sua construção. / The sector of communications, for some years, has undergone significant changes requiring interaction between converging heterogeneous technology environments, with quality and continuity of services to stay competitive, because this market is that requires constantly more technological resources available. The novelty of the proposal developed in this work is the development of a model to ensure the continued quality of service perceived by end users via vertical handover (or handoff), which characterizes itself as a need for a global solution, i.e., the model is generic and technology independent, allowing its adoption in any network environment taking advantage of the capillary already available from legacy networks. It is also analyzed the situation in which an end user is simultaneously accessing services managed by different Service Providers, which leads to two possible situations: a) the user is accessing different services contracted to different Service Providers; b) the user is accessing the same service contracted to different Service Providers. In this last situation may be necessary to trigger a handover process requiring the decision of which the Providers shall execute it in accordance with the SPHDA - Service Providers Handover Decision Agreement. The methodology adopted for the model development was the RM-ODP - Reference Model for Open Distributed Processing, as it includes all technical and commercial aspects necessary for its construction.

With the upcoming of the fifth generation of cellular networks there are several perfor- mance requirements that need to be satisfied. This thesis focuses on the topic of mobility which allows users to move through the network using the concept of handovers to switch between base stations. However, the thesis also keeps the energy efficiency in mind and investigates a strategy of reducing the energy consumption. Moving across base stations will inevitably lead to some handover failures, a goal of the system developers is to reduce these, but there exists a tradeoff between too early and too late handover failures. This thesis investigates two approaches of lowering the number of failures by letting the net- work self-optimize parameters in the handover procedure based upon the tradeoff. The first approach includes a parameter adaption to an estimated velocity of the users and the second one making a parameter more granular. Simulating different scenarios in a detailed network simulator shows performance gain by adapting handover parameters to the esti- mated velocity, but gathering more data regarding failures is needed before generalizing the conclusions.

Due to terminal mobility and change of service area, efficient IP mobility support is an important aspect in UMTS networks in order to provide mobile users negligible packet loss rate and low handover latency, and thus some level of guaranteed quality-ofservice (QoS) to support real-time applications. 3G/UMTS has been specified and implemented as an end-to-end mobile communications system. The underlying WCDMA access systems manage radio access handover (layer 1) and provide linklayer mobility (layer 2) in terms of connection setup and resource management. For the UMTS nodes to have seamless connectivity with the Internet, the UMTS core networks need to be able to support continuous and no network service session handover (layer 3 and above). A long IP handover latency results in high packet loss rate and severely degrades its end-to-end transport level performance. Network-layer handover latency has therefore been regarded as one of the fundamental limitations in IP-based UMTS networks. Therefore, it is crucial to provide efficient network-layer mobility management in UMTS/WCDMA networks for seamless end-to-end TCP connection with the global Internet. Mobility of UMTS nodes necessitates extra functionalities such as user location tracking, address registration and handover related mechanisms. The challenge to provide seamless mobility in UMTS requires localised location management and efficient IP handover management. Mobile IPv6 protocol offers a better mobility support as the extended IPv6 features with mobility mechanism are integrated to the mobile nodes. To mitigate the effect of lengthy IP handover latency, two well-known handover reducing mechanisms based on Mobile IPv6 support have been proposed in the literature. They are designed with hierarchical network management and address pre-configuration mechanism. Hierarchical management aims to reduce the network registration time, and fast-handover attempts to minimise the address resolution delay. S-MIP (Seamless Mobile IP) integrates the key benefits of the above IP mobility mechanisms coupled with local retransmission scheme to achieve packet lossless and extremely low handover latency, operating in WLAN environments. In this thesis, we explore the possible Mobile IP solutions and various IP handover optimisation schemes in IPv6 to provide seamless mobility in UMTS with the global Internet. It aims at developing an optimised handover scheme that encompasses the packet lossless and extremely low handover latency scheme in S-MIP, and applying it into the UMTS/WCDMA packet data domain. Therefore, the hybrid UMTS-SMIP architecture is able to meet the requirements of delay sensitive real-time applications requiring strict delay bound, packet lossless and low handover latency performance for end-to-end TCP connection during a UMTS IP-based handover. The overall seamless handover architecture in UMTS facilitates integrated, scalable and flexible global IP handover solution enabling new services, assuring service quality and meeting the user???s expectations in future all-IP UMTS deployment. The viability of the seamless mobility scheme in UMTS is reflected through and validated in our design model, network protocol implementation, and service architecture. We illustrate the performance gained in QoS parameters, as a result of converged UMTS-SMIP framework compared to other Mobile IPv6 variants. The simulation results show such a viable and promising seamless handover scheme in UMTS on IP handover latency reduction on its end-to-end TCP connection.

Due to terminal mobility and change of service area, efficient IP mobility support is an important aspect in UMTS networks in order to provide mobile users negligible packet loss rate and low handover latency, and thus some level of guaranteed quality-ofservice (QoS) to support real-time applications. 3G/UMTS has been specified and implemented as an end-to-end mobile communications system. The underlying WCDMA access systems manage radio access handover (layer 1) and provide linklayer mobility (layer 2) in terms of connection setup and resource management. For the UMTS nodes to have seamless connectivity with the Internet, the UMTS core networks need to be able to support continuous and no network service session handover (layer 3 and above). A long IP handover latency results in high packet loss rate and severely degrades its end-to-end transport level performance. Network-layer handover latency has therefore been regarded as one of the fundamental limitations in IP-based UMTS networks. Therefore, it is crucial to provide efficient network-layer mobility management in UMTS/WCDMA networks for seamless end-to-end TCP connection with the global Internet. Mobility of UMTS nodes necessitates extra functionalities such as user location tracking, address registration and handover related mechanisms. The challenge to provide seamless mobility in UMTS requires localised location management and efficient IP handover management. Mobile IPv6 protocol offers a better mobility support as the extended IPv6 features with mobility mechanism are integrated to the mobile nodes. To mitigate the effect of lengthy IP handover latency, two well-known handover reducing mechanisms based on Mobile IPv6 support have been proposed in the literature. They are designed with hierarchical network management and address pre-configuration mechanism. Hierarchical management aims to reduce the network registration time, and fast-handover attempts to minimise the address resolution delay. S-MIP (Seamless Mobile IP) integrates the key benefits of the above IP mobility mechanisms coupled with local retransmission scheme to achieve packet lossless and extremely low handover latency, operating in WLAN environments. In this thesis, we explore the possible Mobile IP solutions and various IP handover optimisation schemes in IPv6 to provide seamless mobility in UMTS with the global Internet. It aims at developing an optimised handover scheme that encompasses the packet lossless and extremely low handover latency scheme in S-MIP, and applying it into the UMTS/WCDMA packet data domain. Therefore, the hybrid UMTS-SMIP architecture is able to meet the requirements of delay sensitive real-time applications requiring strict delay bound, packet lossless and low handover latency performance for end-to-end TCP connection during a UMTS IP-based handover. The overall seamless handover architecture in UMTS facilitates integrated, scalable and flexible global IP handover solution enabling new services, assuring service quality and meeting the user???s expectations in future all-IP UMTS deployment. The viability of the seamless mobility scheme in UMTS is reflected through and validated in our design model, network protocol implementation, and service architecture. We illustrate the performance gained in QoS parameters, as a result of converged UMTS-SMIP framework compared to other Mobile IPv6 variants. The simulation results show such a viable and promising seamless handover scheme in UMTS on IP handover latency reduction on its end-to-end TCP connection.

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¡@¡@In recent years, the trends in network communication towards mobile network .Traditional network cannot meet the need of new communication challenge. The 802.11 outperforms other new wireless network technique ¡@¡@In this paper, we assume user have wireless NIC devices with Mobile IPv6 protocol module. We use this model to build an environment and use this environment to design our Mobile IPv6 multicast simulation. We do these for two reasons, (1)To analyze how to use multicast over Mobile IPv6 wireless network. (2)To design an experimentation for multicast over wireless LAN. After we get results of the experimentation, we could know why wireless network does not have better quality than wired LAN. ¡@¡@During our implementation, we have a high latency problem and try to solve it by our program. After our improvement, average latency reduces to 27.77% and miss rate reduces to 33.07%. ¡@¡@Our implementation not only provide some useful information when some one need to build Mobile IPv6 environment but also give a solution for solving handover latency problem.