Seamless roaming between UMTS and IEEE 802.11 networks, Journal of Telecommunications and Information Technology, 2004, nr 4

Mobile Internet access is currently available mainly using 2G/3G cellular telecommunication networks and wireless local area networks. WLANs are perceived as a local complement to slower, but widely available cellular networks, such as existing GSM/GPRS or future UMTS networks. To benefit from the advantages offered by both radio access networks, a mobile user should be able to seamlessly roam between them without the need to terminate already established Internet connections. The goal of this paper is to present an overview of the profitability of performing vertical handovers between UMTS and IEEE 802.11b using Mobile IP. Several simulations have been carried out using NS-2, which prove that handovers from IEEE 802.11b to UMTS can, under certain circumstances, be profitable not only when there is no more IEEE 802.11b coverage. Simulation results show that a mobile user should be able to roam between these networks depending on the current available channel bandwidth and quality, generated traffic type and number of users in both of them

Queueing Networks for Vertical Handover

PhDIt is widely expected that next-generation wireless communication systems will be heterogeneous, integrating a wide variety of wireless access networks. Of particular interest recently is a mix of cellular networks (GSM/GPRS and WCDMA) and wireless local area networks (WLANs) to provide complementary features in terms of coverage, capacity and mobility support. If cellular/ WLAN interworking is to be the basis for a heterogeneous network then the analysis of complex handover traffic rates in the system (especially vertical handover) is one of the most essential issues to be considered. This thesis describes the application of queueing-network theory to the modelling of this heterogeneous wireless overlay system. A network of queues (or queueing network) is a powerful mathematical tool in the performance evaluation of many large-scale engineering systems. It has been used in the modelling of hierarchically structured cellular wireless networks with much success, including queueing network modelling in the study of cellular/ WLAN interworking systems. In the process of queueing network modelling, obtaining the network topology of a system is usually the first step in the construction of a good model, but this topology analysis has never before been used in the handover traffic study in heterogeneous overlay wireless networks. In this thesis, a new topology scheme to facilitate the analysis of handover traffic is proposed. The structural similarity between hierarchical cellular structure and heterogeneous wireless overlay networks is also compared. By replacing the microcells with WLANs in a hierarchical structure, the interworking system is modelled as an open network of Erlang loss systems and with the new topology, the performance measures of blocking probabilities and dropping probabilities can be determined. Both homogeneous and non-homogeneous traffic have been considered, circuit switched and packet-switched. Example scenarios have been used to validate the models, the numerical results showing clear agreement with the known validation scenarios

Journal of Telecommunications and Information Technology, 2004, nr 4

kwartalni

Load balancing in heterogeneous wireless communications networks. Optimized load aware vertical handovers in satellite-terrestrial hybrid networks incorporating IEEE 802.21 media independent handover and cognitive algorithms.

Heterogeneous wireless networking technologies such as satellite, UMTS, WiMax and WLAN are being used to provide network access for both voice and data services. In big cities, the densely populated areas like town centres, shopping centres and train stations may have coverage of multiple wireless networks. Traditional Radio Access Technology (RAT) selection algorithms are mainly based on the ¿Always Best Connected¿ paradigm whereby the mobile nodes are always directed towards the available network which has the strongest and fastest link. Hence a large number of mobile users may be connected to the more common UMTS while the other networks like WiMax and WLAN would be underutilised, thereby creating an unbalanced load across these different wireless networks. This high variation among the load across different co-located networks may cause congestion on overloaded network leading to high call blocking and call dropping probabilities. This can be alleviated by moving mobile users from heavily loaded networks to least loaded networks. This thesis presents a novel framework for load balancing in heterogeneous wireless networks incorporating the IEEE 802.21 Media Independent Handover (MIH). The framework comprises of novel load-aware RAT selection techniques and novel network load balancing mechanism. Three new different load balancing algorithms i.e. baseline, fuzzy and neural-fuzzy algorithms have also been presented in this thesis that are used by the framework for efficient load balancing across the different co-located wireless networks. A simulation model developed in NS2 validates the performance of the proposed load balancing framework. Different attributes like load distribution in all wireless networks, handover latencies, packet drops, throughput at mobile nodes and network utilization have been observed to evaluate the effects of load balancing using different scenarios. The simulation results indicate that with load balancing the performance efficiency improves as the overloaded situation is avoided by load balancing

Soluções de broadcast para redes 4G

Mestrado em Engenharia Electrónica e de TelecomunicaçõesA primeira difusão de conteúdos video e audio teve um forte impacto no quotidiano da população que assistiu a uma revolução nos modelos de transmissão de informação e de entretenimento. A evolução desde então foi significativa, e já na era digital, encontramo-nos face a uma nova sub-elevação da metodologia e do conceito subjacentes à transmissão de conteudos multimédia. O mundo actual apresenta, contudo, diferentes requisitos, de entre os quais se destacam a procura pela alta definição e mobilidade. A mobilidade tem sido um particular foco de atenção por parte dos operadores que exploram agora modelos para entregar uma vasta gama de serviços que sejam atractivos para os utilizadores. Esta dissertação apresenta um sumário das tecnologias emergentes de broadcast que se distinguem nas várias partes do mundo com a sua particular incidência geográfica, características e cenários de aplicação. É ainda apresentada uma arquitectura 4G abordando assuntos inerentes à mobilidade e qualidade de serviço com particular incidência nos aspectos relacionados com a integração de uma tecnologia de broadcast particular. Para avaliação da arquitectura proposta foram efectuados estudos com base num equipamento de broadcast na sua versão comercial, permitindo desta forma obter uma análise que ilustra o que os operadores podem esperar do estado actual dos dispositivos. Os resultados permitiram retirar ilações sobre o comportamento de um equipamento considerado como um produto final a disponibilizar aos operadores, quando integrado num ambiente 4G com suporte de mobilidade e QoS. Nomeadamente é discutida a sua aplicabildiade tendo em linha de conta as desvantagens introduzidas pelas características inerentes à própria tecnologia.Broadcast of video and audio through analogical television completely changed the paradigm of information and entertainment divulgation. Today, in the “digital era”, the Analogue Switch Off revolution is being held. Manufacturers and operators already show concerns regarding the support of mobility, quality of experience and of service. Delivering competitive High Definition contents and providing solutions for the average “on-the-move” user are two of the most important issues to be dealt by the service providers, which are also within the analysis scope of this work. This dissertation presents an overview on the most relevant broadcast technologies which are assumed to be of relative acceptance in their respective target market. It presents their main characteristics and applicability. 4G architectural concepts are also analyzed, closely dealing with mobility and quality of service provisioning, with particular focus on the seamless integration of broadcast technologies. As a mean to evaluate the feasibility of integrating broadcast technologies with 4G architectures, a performance evaluation study was performed using commercial equipment. In this way a several set of considerations constructed illustrating the features and functionalities which operators can expect or disregard from professional commercial broadcasting devices. Results allow the withdrawing of conclusions concerning the integration of a final broadcasting solution when incorporated within a 4G environment with QoS and mobility support. Its applicability is evaluated having in mind the performance drawbacks introduced by the specific technology, and generalized towards the gathering of more general conclusions which consider the main characteristics of the commercial broadcasting devices

Radio Communications

In the last decades the restless evolution of information and communication technologies (ICT) brought to a deep transformation of our habits. The growth of the Internet and the advances in hardware and software implementations modified our way to communicate and to share information. In this book, an overview of the major issues faced today by researchers in the field of radio communications is given through 35 high quality chapters written by specialists working in universities and research centers all over the world. Various aspects will be deeply discussed: channel modeling, beamforming, multiple antennas, cooperative networks, opportunistic scheduling, advanced admission control, handover management, systems performance assessment, routing issues in mobility conditions, localization, web security. Advanced techniques for the radio resource management will be discussed both in single and multiple radio technologies; either in infrastructure, mesh or ad hoc networks

Mobile Offloading in Residential Wireless Access Markets

The growth of mobile data traffic has been increasing at a tremendous pace. Currently, mobile broadband is mostly served by macro base stations. Strong attenuation occurs when the signals penetrate through buildings affecting the quality of service. Hence, mobile operators need to enhance the capacity to minimise congestion problems and improve the coverage on their macro networks for better network operation. As most of the mobile traffic occurs indoors, there is a need for indoor network deployments. A qualitative analysis employing the combination of various research methods (value network configuration, system dynamics, expert interviews) has been carried out to investigate various factors besides mobile offloading, which could lead to a large-scale deployment of femtocells in homes with the focus on Finland. This study also discusses several options to cope with the mobile traffic growth and examines different indoor network deployment scenarios. Furthermore, the scenarios of Femtocell-as-a-Service are highlighted and its possible impacts on mobile operators’ business are covered as well. The analysis is also conducted to illustrate how different actors are interrelated in the home network business. The analysis reveals that the primary factor that will contribute to the success of femtocell deployment in homes is the need for future mobile offloading. However, many other factors have important implications which require careful consideration by mobile operators. With the presence of good macro network capacity like in Finland, new services and partnership with third party providers has been identified as the most important factor. Mobile operators need to offer an incentive to attract end-users to adopt a femtocell service due to the strong positioning of WiFi in homes. Therefore, new services would also enable the penetration of femtocells into homes to compete with WiFi access points. Three factors (interference mitigation and interoperability, femtocell management system, backhaul) are also important as these are needed to ensure the femtocell networks operate reliably. As lowering the cost is essential for building scale, the model of Femtocell-as-a-Service is useful as it reduces capital investments for mobile operators. Interviews with the experts found that major mobile operators are less likely to adopt this model. This is better suited for smaller mobile operators that want to quickly enter the femtocell business

Techno-economic valuation of mobile communications scenarios

Valuation of large projects on new communications technologies is a challenging task. Major investments are required to spread out technology and services, the characteristics of which are still largely unknown. A balanced view is needed on capabilities of the technologies, market demand, and relevant value network actors and their economies. In this dissertation, comprehensive techno-economic modelling of these aspects will be introduced for valuation of selected business scenarios. The research framework is mobile data services and business architectures in the advent of new technologies, like UMTS (Universal Mobile Telecommunications System), WLAN (Wireless Local Area Network) and WiMAX (Worldwide Interoperability for Microwave Access). The techno-economic method in this context comprises the modelling of a large set of technology, market and other factors in relation to the business operations of the analysed market actors. The many uncertainties concerning future service innovations and market development set demands on scenario creation and parameter estimation. Traditional techno-economic investment project calculation is not enough. This study gives devices for strategic decision making by analysing three different technology transitions: The modelling of Western-European incumbent operator business starting from the early 2000's indicated that the UMTS deployment should be started without delay to maximise the long-term profits from the acquired licenses, contrary to looking for short-term investment payoffs that was prevalent after the telecommunications downturn. Results also show that the emerging WLAN technology would not become a substitute for UMTS, but the public WLAN will complement the UMTS based business architecture. Modelling of the upcoming mobile WiMAX in comparison to UMTS path indicated that the mobile WiMAX cannot challenge the UMTS, as the latter one offers a better business case for the key actors. In the last transition, techno-economic delta analysis was used to quantify the benefits from the fixed-mobile convergence. The main enhancements to the techno-economic method are first the extensive classification of advanced mobile services and related modelling of service diffusion, usage patterns, capacity requirements and revenues. The second contribution is to improve the analysis of service usage in relation to technology characteristics by integrating an end-user model that gives the demand and revenue potential of each service type, per user segment and utilised technology. A novelty is also the separation of network provisioning and service provisioning part of the business architecture into separate but interlinked models. The fourth contribution to the method is the application of real options method on large communications technology deployment projects, solving option modelling problems due to the complex dependencies of the project value on the investment timing. The introduced method starts from ordinary expected cash flow valuation, but adds to that the option value related to specific flexibility in the project