Дисертації з теми "Mobile broadband network"

Satellites will play an indispensable role in the deployment of commercial networks to meet an increasing demand for supporting multimedia services at high data rates. Next generation satellite systems, operating at high frequency bands offer large bandwidth and are able to provide broadband services. To interface satellite links with existing terrestrial networks for providing communication access to a variety of users directly, several performance issues need to be addressed. Current thesis presents a technically viable satellite-integrated network model that is efficient in carrying broadband services to users over a wide scattered area. Accurate prediction of attenuation level is necessary for a reliable network model to operate with required service availability. Long term rainfall data has been analysed to characterise attenuation level at a selected region such as Dhaka. It is shown that rainfall is highly seasonal and attenuation level is quite high during monsoon. However, the seasonal behaviour of rainfall can be exploited to improve the link availability. Radar and rain gauge measurements at Sparsholt are also used to find rain cell size distribution, which is an important factor in site diversity implementation to combat severe rain fade. It is found that convective rain cell has extension in the region of 10 km. The network model is designed with dimensioning the effective bandwidth to support a number of users over the satellite link by taking into account the multimedia traffic characteristics. Concatenated coding, a robust coding scheme is implemented to improve the link quality at a level required to deliver broadband services. The ITU-T performance objectives of 7.5×10 for CLR and 1.4×10 for CER over satellite links are met at a required Eb/No of 2.95 dB and 2.88 dB respectively. Different enhancement mechanisms for optimum TCP performance are implemented to combat the large propagation delay associated with a satellite link. It is revealed through the simulation that TCP performance over a satellite link is as efficient as terrestrial links with these enhancement mechanisms Finally, the overall performance of the designed network is evaluated through link budget analysis and simulation. An innovative downlink power control strategy has been implemented to maintain the link during the rainiest months. The interference level due to high power satellite transmission in the designed system is also calculated to protect other existing communication links sharing the same frequency bands. A feasible broadband network designed with characterising propagation as well as networking issues will efficiently deliver broadband communication services to a large population promptly and in a cost-effective manner. Such a network solution will be in the realm of current R & D towards broadband satellite networks.

“Connected society” where everything and everyone are connected at any time and on any location brings new challenges for the network operators. This leads to the need of upgrading the transport networks as the segment of Internet infrastructure connecting the fixed users and mobile base stations to the core/aggregation in order to provide high sustainable bandwidth, as well as supporting a massive number of connected devices. To do this, operators need to change the way that access networks are currently deployed. The future access network technologies will need to support very high capacity and very long distances, which are the inherited characteristics of optical transmission. Hence, optical fiber technology is recognized as the only future proof technology for broadband access. Capacity upgrade in the access networks can lead to a huge capacity demand in the backbone network. One promising solution to address this problem, is to keep the local traffic close to the end users as much as possible, and prevent unnecessary propagation of this type of traffic through the backbone. In this way, operators would be able to expand their access network without the significant capacity upgrade in the higher aggregation layers. Motivated by this need, a comprehensive evaluation of optical access networks is carried out in this thesis regarding ability of accommodating local traffic and amount of possible saving in the backbone by implementing locality awareness schemes. Meanwhile, next generation optical access (NGOA) networks have to provide high capacity at low cost while fulfilling the increasing reliability requirements of future services and customers. Therefore, finding cost-efficient and reliable alternative for future broadband access is one of the most important contributions of this thesis. We analyzed the tradeoff between the cost needed to deploy backup resources and the reliability performance improvement obtained by the proposed protection mechanism. Among different NGOA architectures, hybrid time and wavelength division multiplexing passive optical network (TWDM PON) is considered as a proper candidate providing high capacity and large coverage. Therefore, this approach is further analyzed and several tailored protection schemes with high flexibility are proposed to statisfy different requirements from the residential and business users in the same PON.  The work carried out in the thesis has proved that TWDM PON can also offer high reliability performance while keeping the network expenditures at an acceptable level. Considering some other advantages such as low power consumption and high flexibility in resource allocation of this architecture, it has high potential to be the best candidate for NGOA networks.  Moreover, new deployments of radio access networks supporting the increasing capacity demand of mobile users lead to the upgrade of the backhaul segment as a part of broadband access infrastructure. Hence, this thesis also contributes with a comprehensive techno-economic evaluation methodology for mobile backhaul. Several technologies are investigated in order to find the most cost-efficient solution for backhauling the high capacity mobile networks.  Finally, a PON-based mobile backhaul with high capacity and low latency has been proposed for handling coordinated multipoint transmission systems in order to achieve high quality of experience for mobile users.

QC 20150320

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CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico
Esta tese se concentra na avaliação técnico econômica de soluções de transporte para acesso banda larga fixa e móvel. Para futuras redes de acesso móvel, propõem-se arquiteturas de backhaul usando fibra e microondas baseado no desenvolvimento de redes de acesso wireless verde e infraestruturas legadas de backhaul baseada em cobre para migração Brownfield, ou seja, usando infraestrutura existente até o limite de capacidade suportada, enquanto para redes de banda larga fixa são propostas implantações de proteção baseadas em esquemas híbridos, ou seja, fiber+wireless. As principais contribuições desta tese estão relacionadas ao campo de pesquisa do custo total de investimento em infraestrutura de transporte banda larga. Em termos de custo total de investimento, são propostos dois conjuntos de modelos para avaliar as despesas de capital e de operação, CAPEX e OPEX respectivamente, de operadoras de redes de acesso banda larga fixa e móvel. Primeiramente, para banda larga móvel, é apresentado um conjunto de modelos condensado em uma metodologia geral que visa fornecer: previsão de tráfego, implantação de rede sem fio, implantação de backhaul móvel e avaliação do custo total. É mostrado que o backhaul baseado em fibra considerando acesso sem fio verde é a opção mais eficiente em termos de energia. Além disso, Brownfield mostra que o backhaul baseado em cobre ainda pode desempenhar um grande papel se utilizado até a exaustão de sua capacidade e reduz drasticamente os custos de investimentos em infraestrutura. Adicionalmente, são apresentadas as principais diferenças de custos e valores de energia entre redes de acesso sem fio verde e Brownfield. Finalmente, para banda larga fixa, é proposta uma metodologia baseada em dimensionamento de rede, custos associados à falha e avaliação do custo total por assinante. Os modelos são utilizados para avaliar cinco modelos que representam diferentes esquemas de proteção para arquiteturas de banda larga fixa. Esta pesquisa revela os benefícios econômicos do uso de esquema de proteção híbrido baseado em arquitetura fiber+wireless comparado com a opção de proteção baseada totalmente em fibra e é também apresentada uma análise de sensibilidade para provar que o investimento adicional em CAPEX para proteger a infraestrutura pode ser recuperado em alguns anos através da economia em OPEX.
This thesis undertakes a techno-economic evaluation of transport solutions for fixed and mobile broadband access. In the case of future mobile access networks, it is proposed to make use of backhaul architectures using fiber and microwave applied to Greenfield deployments and a copper-legacy backhaul infrastructure based on Brownfield migration, i.e. finding a way of using a legacy infrastructure to its full capacity. At the same time, protection deployments based on fiber-wireless schemes are recommended for future fixed broadband. The main contribution made by this thesis is to carry out a research investigation into the total investment cost of the broadband transport infrastructure. This will be determined by employing two sets of models to assess the capital and operational expenditures, (CAPEX and OPEX respectively), of mobile and fixed broadband access network operators. First, this involves a set of models for mobile broadband that are summarized in a general methodology that aims at providing: traffic forecasting, wireless deployment, mobile backhaul deployment and total cost assessment. It was found that, fiber-based backhaul through a Greenfield deployment is the most energy-efficient option. Furthermore, Brownfield reveals that copper-based backhaul can still play a key role if used up to its full capacity and sharply reduces the investment costs in infrastructure. Additionally, there is an examination of the main differences in cost and energy values between Greenfield and Brownfield. Finally, a methodology is employed for fixed broadband based on network dimensioning, failure costs and an assessment of the total cost of ownership. The models are used to assess five architectures that represent different protection schemes for fixed broadband. This research shows the economic benefits of using a hybrid protection scheme based on fiber-wireless architecture rather than fiber-based protection options and a sensitivity analysis is conducted to show that the extra CAPEX invested to protect the infrastructure might be recovered through the OPEX after a number of years. The results obtained in the thesis should be useful for network operators to plan both their fixed and mobile broadband access network infrastructure in the future.

The rapid evolution of mobile communication technologies is making mobile broadband a reality. With over 6 billion cellular connections and the booming of mobile data, mobile broadband leads the technology and service innovation within the domain of information and communication technologies. The thesis deals with performance engineering of mobile broadband. The problems investigated range from fundamental capacity analysis, resource planning and optimization of broadband cellular networks, to design of in-building solutions based on distributed antenna systems. Mathematical modeling and optimization methods have been used to approach the problems. The first three papers address capacity analysis in wireless communications, where the establishment of any communication link is subject to the Signal to Interference plus Noise Ratio (SINR) threshold. Paper I addresses the maximum link activation problem. The paper introduces a new exact algorithm by reformulating the SINR constraints with equivalent but numerically more effective inequalities, leading to an approach performing significantly better in proving optimality in comparison to the conventional algorithm. Paper II explores the notion of collaborative rate selection for Interference Cancellation (IC) to maximize the transmission rate in wireless networks. The paper analyzes the problem complexity and develops integer programming models for both single stage single-link IC and single stage parallel IC. Paper III studies the performance gain of single-stage and multi-stage IC to optimal link activation. Compact integer programming formulations have been developed and a thorough numerical study is performed. The next three papers are devoted to planning and optimization of radio resources in cellular mobile broadband networks. Paper IV considers a minimum-power coverage problem with overlap requirements between cell pairs. The paper develops two integer programming models and compares their strength in approaching global optimality. A tabu search algorithm has been developed for large-scale networks. Paper V deals with transmission power planning and optimization in High Speed Downlink Packet Access (HSDPA) networks. A method for enhancing the HSDPA performance by minimizing the power for coverage and reallocating the power to data transmission has been considered. A mathematical model targeting cell-edge HDSPA performance and accounting for soft handover in Universal Mobile Telecommunications System (UMTS) has been developed. In addition, heuristic algorithms based on local search and repeated local search are developed. Paper VI focuses on frequency planning for inter-cell interference mitigation in Orthogonal Frequency Division Multiple Access (OFDMA) networks. The paper generalizes the standard Fractional Frequency Reuse (FFR) concept and addresses its performance for networks with irregular topology. Optimization algorithms using local search have been proposed to find the frequency reuse pattern of generalized FFR for maximizing the edge-user performance. The investigations in Papers IV-VI base the experiments on data sets representing realistic planning scenarios to demonstrate the effectiveness of the proposed approaches. To face the challenge of in-building mobile broadband service, In-Building Distributed Antennas Systems (IB-DAS) has been proposed. Paper VII tackles the problem of optimal topology design of IB-DAS systems, where a number of in-building distributed antennas are connected to a base station via coaxial cables and power equipments. The paper develops efficient mathematical models for topology design as well as equipment selection, and presents case studies of realistic IB-DAS deployment scenarios.

Exponential growth in the volume of wireless data, boosted by the growing popularity of mobile devices such as smart phones and tablets, is forcing telecommunication industries to rethink network design, and focus on developing high capacity mobile broadband networks. Accordingly, researchers have undertaken developmental work for an integrated wireless-optical broadband access network (WOBAN). Passive optical networks (PONs) and fourth generation (4G) wireless networks are two major candidate technologies for the WOBAN. PON is a wired access technology, well-known for its high capacity, whereas 4G is a wireless broadband access technology, popular for its ease of deployment and ability to offer mobility. Integration of PON and 4G technologies, as a wireless-optical broadband access network, offers advantages such as extension of networks in rural areas, support for mobile broadband services, and rapid deployment of broadband networks. However, these two technologies have different design architectures for handling broadband services which require Quality of Service (QoS), for example, 4G networks use traffic classification for supporting different QoS demands whereas PON does not differentiate between traffic types. This integrated network must also be energy efficient, as a green broadband access network, without hindering QoS. While these technologies both use sleep mode, they differ in their power saving mechanisms. This thesis first addresses a QoS solution for the incompatibility between these technologies. Service class mapping is proposed in Chapter 3 for the integrated WOBAN, based on the M/G/1 queuing model supported by an innovative priority scheduler. Once class mapping is deployed, a power saving mechanism can be devised by exploiting traffic differentiation. Specifically, a class-based strategy is proposed which helps optimise the sleep period for the terminal units of the optical network, without compromising QoS. Since the optical network involves control and terminal nodes, both of which consume power, this thesis proposes an energy efficient mechanism that involves both components. In contrast, other published strategies (Chapter 2) have only considered the terminal units. Chapter 4 presents the mechanism for enabling global sleep (control and terminal nodes) and local sleep (terminal nodes), based on the available traffic's class structure. This mechanism enables sleep for different components within the bandwidth allocation by adapting the switching between predefined polling cycle lengths. As the WOBAN is comprised of both wireless and optical parts, a dynamic resource management mechanism is needed which responds to changing daily traffic patterns across a green integrated network. Consequently, Chapter 5 proposes a mechanism which dynamically adapts the polling cycles, of the optical and wireless parts of the network, to the changing traffic volume and class composition. Tailored sleep durations for the components of the WOBAN are facilitated within the resource management regime, as these components differ in their ability to function efficiently if management of the sleep periods is not responsive to the changing traffic volumes and class composition. This dissertation creates new knowledge by seamlessly integrating the two parts of WOBAN and introducing differentiated, class-based sleep for the components of the hybrid network to help realise a green WOBAN.

The objective of this research is to investigate how mobile cellular network operators can increase the average revenue per user by stimulating the usage of mobile broadband services. There is a general consensus that the revenue from voice calls is slowly reaching saturation; hence, mobile cellular operators, service providers and content providers are looking for other sources of revenue from their new and existing customers. They are therefore beginning to focus more intensively on customer retention and on developing new strategies that will stimulate the usage of high speed mobile data services. The research shows that most people are aware of many of the mobile data services offered by operators, but that they thought that they were unreliable, slow, difficult to use and expensive. By and large, people signed up for mobile data services because they wanted a mobile always-on connection anytime, anywhere, with faster speed when accessing e-mail and other services or when downloading data from the Internet. The majority of people would use mobile broadband internet service if it cost less to use; if the speed were faster and the service were easy to use; if the cellular phone had a larger screen and used less battery power; and if the keyboard were larger. The relationship between Network operators, WASPs and content providers was found to be good, even though at times it is strained by the increased competition between them; this forces them not to cooperate on some issues for fear of compromising their competitive advantage.

This thesis studies intelligent spectrum and topology management through transfer learning in mobile broadband networks, to improve the capacity density and Quality of Service (QoS) as well as to reduce the cooperation overhead and energy consumption. The dense deployment of small cell base stations (BSs) is an effective approach to provide high capacity density access. In the meantime, multi-hop wireless backhaul networks enable highly flexible deployment and self-organization of small cell BSs. A heterogeneous small cell access and multi-hop backhaul network is studied in this thesis as mobile broadband system architecture. Transfer learning is applied to Radio Resource Management (RRM) as an intelligent algorithm to improve the performance of conventional reinforcement learning. In transfer learning, a BS trains its knowledge base relying on knowledge transferred from other related BSs, who are selected using an interference coordination strategy. In a network with static topology, cooperation management is developed to identify the maturity of the knowledge base and control the coordination overhead. It is demonstrated in a multi-hop backhaul network that transfer learning delivers a QoS level that is as high as achieved by a fully coordinated algorithm, but with a very low level of information exchange which is close to a fully distributed algorithm. Transfer learning is also studied in rapidly changeable network architectures to provide reliable communication. It is carried out during the changes of network topology, through mapping the learner’s knowledge base to a prioritized action space with Pareto efficiency. This process assists the BSs to quickly identify and adapt to environment changes, and makes effective decisions. Results show that transfer learning significantly reduces QoS fluctuation during traffic variation and topology changes in a highly dynamic network. Furthermore, a dynamic topology management algorithm is developed to intelligently control the working modes of BSs, based on traffic load and capacity in multiple cells. Topology management is demonstrated to reduce the number of activated BSs with adequate QoS performance provided. Dynamic capacity provision between multiple cells is achieved from transfer learning, which significantly improves QoS and reduces energy consumption.

Multiple-Input Multiple-Output (MIMO) techniques are widely touted as the technology that will enable the high wireless cellular network capacities demanded by the huge growth in demand for the 'triple play' of voice, data and media. Without suitable interference management, however, multi-billion dollar MIMO Mobile Wireless Broadband Networks (MWBNs) can collapse under the strain of heavy traffic loads. Fully loaded interference studies cannot be performed on the network until it has been fully deployed. As such, interference characterisation and mitigation must be accurately performed pre-deployment using detailed network simulators. The development of a detailed MWBN simulator is investigated in this thesis. The model includes an extremely Uplink (UL) and Downlink (DL) Mobile WiMAX system-level simulator with full support for a wide range of MIMO technologies. The impact of inter-cell interference is characterised and results show that it is the fluctuation in interference power, rather than signal power, that dominates the inaccuracies seen in the link adaptation algorithm. These error lead to reduced system throughput. It is found that the Modulation and Coding Scheme (MCS) errors increase with Channel State Information (CSI) delay and that the effect is exacerbated by high mobile velocity. With a 3-frame delay at vehicular speeds the CSI delay causes an average 31 % loss in DL throughput. It is found that 2 x 2 closed-loop MIMO systems can double the system capacity in high interference conditions but the MIMO techniques in high interference are used to exploit diversity, and not multiplexing, gain. The gains provided by closed-loop MIMO are only available to slow moving or stationary users. Interference management techniques can be divided into: interference randomisation, interference cancellation and interference mitigation. It is shown that the use of interference randomisation reduces MCS error and improves user throughput. Significant performance gains are achieved in this work using higher order MIMO configurations and interference cancellation schemes. The gains are particularly significant at the cell edge on the DL. They are also effective on the UL, where unlike the DL they are robust to delayed CSI at the transmitter. A 5-fold increase over the single antenna case is obtained using a 2 x 8 MIMO system with interference cancellation. The use of interference coordination combined with interference cancellation further enhances performance, particularly on the DL. Adding the " combined mitigation scheme to the 4 x 2 MIMO case improves the average cell throughput by 70% and the cell edge throughput by 370%. This rigorous study has shown that to perform effectively in interference-limited scenarios, future MWBNs should employ 8x 2 MIMO with interference cancellation and interference coordination. This can provide Base Station (BS) throughput gains of up to 4-fold on the DL and 5-fold on the UL over a single antenna implementation.

This thesis presents an investigation of the impact of indoor small-cells. It is expected that small-cells will be able to increase the throughput and capacity for the existing networks. A deployment algorithm is presented with focus on offloading traffic from the macro layer. The performance of the deployments created with the proposed algorithm, is compared with a reference deployment. The different deployments are then simulated in a real network simulator, which performs static simulations in 3 dimension using the theory of multiple knife-edge diffraction. The small-cells increased the throughput and capacity remarkably and additional gains were obtained with the proposed algorithm. The thesis also includes strategies for small-cell deployment.

One of the challenges of the mobile industry is to cope with the growth of mobile traffic demand expected for the next years, primarily driven by the increasing usage of mobile video services. Indeed, the existence of increasingly powerful terminals is encouraging the consumption of high-quality video content. Usually, video services are identified with linear Television (TV) and scheduled broadcast (point-to-multipoint (p-t-m)) distribution. However, the consumption of video content over mobile networks is different from traditional fixed TV because contents are mainly consumed on-demand with unicast point-to-point (p-t-p) connections. Then, the convergence of linear TV and on-demand content delivery represents a challenge that requires a combined broadcast/unicast transmission model. This dissertation addresses the use of broadcasting technologies for the provision of mobile multimedia services in Fourth Generation (4G) mobile broadband networks and beyond. Specifically, the dissertation focuses on the broadcast technology included in 4G Long Term Evolution (LTE) and LTE Advanced (LTE-A) networks, known as Enhanced Multicast Broadcast Multimedia Services (eMBMS). It analyses the benefits of the eMBMS physical layer aspects regarding Multimedia Broadcast Multicast Services over a Single Frequency Network (MBSFN) deployments and identifies the current limitations of eMBMS at physical layer by comparing with the broadcast technology of the other 4G mobile system, the Institute of Electrical and Electronics Engineers (IEEE) 802.16m standard. Those limitations are the use of a dedicated carrier and Multiple-Input Multiple-Output (MIMO) techniques for broadcast transmissions. Our investigations employ a complete simulation platform including link-level and system-level simulations to evaluate the performance of broadcast transmissions in these real technologies. The research on eMBMS services is aimed at finding the optimum delivery of streaming and file download services focusing on the Radio Resource Management (RRM) problem and trade-off between Physical layer – Forward Error Correction (PHY-FEC) and Application Layer - Forward Error Correction (AL-FEC). Concerning streaming services, results show that the use of AL-FEC increases the coverage level and, then, the maximum service data rate. The gain due to AL-FEC is greater in scenarios with high mobility users, although, this gain is limited if low zapping times are desired. Regarding file delivery services, this dissertation analyses the duration of the transmission required to guarantee the correct file reception and the reduction in the mean throughput of unicast users with different delivery modes. They are the unicast delivery, the eMBMS delivery and a hybrid approach, which combines a first eMBMS delivery with a postdelivery error repair phase with unicast transmissions. Our results show that the hybrid delivery is the most efficient configuration in terms of file download time, although it further reduces unicast performance.
Calabuig Gaspar, J. (2015). Broadcasting in 4G mobile broadband networks and its evolution towards 5G [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/48561
TESIS

When looking towards the deployment of 5G network architectures, mobile network operators will continue to face many challenges. The number of customers is approaching maximum market penetration, the number of devices per customer is increasing, and the number of non-human operated devices estimated to approach towards the tens of billions, network operators have a formidable task ahead of them. The proliferation of cloud computing techniques has created a multitude of applications for network services deployments, and at the forefront is the adoption of Software-Defined Networking (SDN) and Network Functions Virtualisation (NFV). Mobile network operators (MNO) have the opportunity to leverage these technologies so that they can enable the delivery of traditional networking functionality in cloud environments. The benefit of this is reductions seen in the capital and operational expenditures of network infrastructure. When going for NFV, how a Virtualised Network Function (VNF) is designed, implemented, and placed over physical infrastructure can play a vital role on the performance metrics achieved by the network function. Not paying careful attention to this aspect could lead to the drastically reduced performance of network functions thus defeating the purpose of going for virtualisation solutions. The success of mobile network operators in the 5G arena will depend heavily on their ability to shift from their old operational models and embrace new technologies, design principles and innovation in both the business and technical aspects of the environment. The primary goal of this thesis is to design, implement and evaluate the viability of data centre and cloud network infrastructure sharing use case. More specifically, the core question addressed by this thesis is how virtualisation of network functions in a shared infrastructure environment can be achieved without adverse performance degradation. 5G should be operational with high penetration beyond the year 2020 with data traffic rates increasing exponentially and the number of connected devices expected to surpass tens of billions. Requirements for 5G mobile networks include higher flexibility, scalability, cost effectiveness and energy efficiency. Towards these goals, Software Defined Networking (SDN) and Network Functions Virtualisation have been adopted in recent proposals for future mobile networks architectures because they are considered critical technologies for 5G. A Shared Infrastructure Management Framework was designed and implemented for this purpose. This framework was further enhanced for performance optimisation of network functions and underlying physical infrastructure. The objective achieved was the identification of requirements for the design and development of an experimental testbed for future 5G mobile networks. This testbed deploys high performance virtualised network functions (VNFs) while catering for the infrastructure sharing use case of multiple network operators. The management and orchestration of the VNFs allow for automation, scalability, fault recovery, and security to be evaluated. The testbed developed is readily re-creatable and based on open-source software.

Computer networks are in the scope of the IEEE organization normalized by the 802 board which currently comprises six working groups for wireless communications. IEEE 802.11 for wireless local area networks, IEEE  802.15 for wireless personal area networks, IEEE 802.16 for wireless metropolitan area networks, IEEE 802.20 for mobile broadband wireless access, IEEE 802.21 for media independent handover and IEEE 802.22 for wireless regional area networks. This master's thesis focuses on a security analysis of particular standards, describes threats, vulnerabilities, current security measures and mutually compares wireless specifications from a security point of view. The conclusion is devoted to overall evaluation of the project, to its contributions, possible enhancements and continuation in the form of consequential studies.

Abstract Sharing is emerging as one of the megatrends influencing future business opportunities, and wireless communications is no exception to this development. Future mobile broadband networks will operate on different types of spectrum bands including shared spectrum, which calls for changes in the operation and management of the networks. The creation and capture of value by the different players in the mobile broadband ecosystem is expected to change due to regulation, technology, and business landscape related drivers that concern not only spectrum sharing, but also sharing of other resources such as infrastructure, technologies, or data. This thesis examines the key business and technology enablers needed to exploit spectrum sharing in mobile broadband networks, and presents the business model characteristics and strategic choices that spectrum sharing concepts support. Action research and integral scenarios methodologies were applied for strategic and business analysis utilizing the capacity and expertise of the policy, business and technology research communities. The thesis introduces a new approach to analyze the scalability of the spectrum sharing concepts and their business model elements utilizing sharing economy antecedent factors. The results indicate that all analyzed sharing concepts meet basic requirements to scale. The Licensed Shared Access (LSA) leverages existing assets and capabilities of the mobile network operator domain, the Citizens Broadband Radio Service (CBRS) extends the business model dynamics from connectivity to content, context and commerce, and the hybrid usage of Ultra High Frequency (UHF) band by Digital Terrestrial TV (DTT) and downlink Long Term Evolution (LTE) (HUHF) enables new collaborative opportunities between converging communication, Internet and media domains. The thesis validates the feasibility of spectrum sharing between mobile broadband networks and other types of incumbent spectrum users utilizing Finnish cognitive radio field trial environment (CORE), and expands the notion of spectrum sharing beyond the mobile broadband domain to be applied to other wireless systems including the media and broadcasting. The presented results can be used in developing the future mobile broadband systems enhanced with innovative spectrum sharing enabled business models to cope with the growing demand for capacity and new services by humans and machines
Tiivistelmä Jakamistalous on yksi suurista tulevaisuuden liiketoimintamahdollisuuksiin vaikuttavista trendeistä, eikä langaton tietoliikenne ole tässä poikkeus. Tulevaisuuden laajakaistaiset matkapuhelinverkot tulevat hyödyntämään erityyppisiä radiotaajuuksia, kuten jaettuja taajuuskaistoja, mikä vaatii muutoksia verkkojen toimintoihin ja hallintaan. Eri toimijoiden arvonluonti- ja ansaintamahdollisuuksien odotetaan muuttuvan näissä liikkuvan laajakaistan ekosysteemeissä regulaation, teknologian ja liiketoimintaympäristön kehittyessä, ei vain taajuuksien jakamisessa, vaan myös kun kyseessä on muiden resurssien kuten infrastruktuurin, teknologioiden tai tiedon jakaminen. Väitöskirja tutkii teknologia- ja liiketoimintaedellytyksiä taajuusjakomenetelmille matkapuhelinverkoissa, sekä esittelee ja analysoi menetelmien mahdollistamia liiketoimintamalleja ja strategisia valintoja. Strategia- ja liiketoiminta-analyyseissä käytettiin toimintatutkimus- ja skenaariomenetelmiä poikkitieteellisissä tutkimusprojekteissa yhteistyössä reguloinnin, liiketoiminnan ja tekniikan tutkimusyhteisöjen kanssa. Tutkimus esittelee uuden lähestymistavan taajuusjakotekniikoiden liiketoimintamallien skaalautuvuuden analysointiin jakamistalouden määritelmiä hyödyntäen. Tulokset osoittavat, että kaikki tutkitut tekniikat täyttävät perusedellytykset skaalautuvuudelle; Licensed Shared Access (LSA) hyödyntäen matkapuhelinoperaattorin olemassa olevia resursseja ja kyvykkyyksiä, Citizens Broadband Radio Service (CBRS) laajentaen liiketoimintamalleja tietoliikenteestä sisältöön, kontekstiin ja kaupankäyntialustoihin, sekä digitaalitelevision ja langattoman LTE-tekniikan hybridikäyttö UHF-taajuuskaistalla (HUHF) mahdollistaen uusia liiketoimintamahdollisuuksia lähentyvien tietoliikenne-, Internet- ja mediaekosysteemien välillä. Väitöskirja tulokset vahvistivat taajuuden jakamisen soveltuvuuden liikkuvan laajakaistaverkon ja saman taajuusalueen eri teollisuudenalan haltijan välillä suomalaisessa CORE kenttätestausympäristössä, ja laajensivat taajuusjakotekniikan sovellettavuutta myös muihin langattomiin järjestelmiin sisältö- ja mediajakelussa. Esitettyjä tuloksia voidaan hyödyntää tulevaisuuden langattomien laajakaistaverkkojen kehitystyössä vastaamaan ihmisten ja koneiden kasvaviin tietoliikennepalveluiden ja -kapasiteetin tarpeisiin hyödyntäen tehokkaita taajuusjakotekniikoita ja niiden mahdollistamia innovatiivisia liiketoimintamalleja

This Thesis is an embodiment of some research work carried out towards achieving faster and more reliable handover techniques in a Mobile WiMAX (Worldwide Interoperability for Microwave Access) network. Handover, also called handoff, is the critical mechanism that allows an ongoing session in a cellular mobile network like WiMAX to be seamlessly maintained without any call drop as the Mobile Station (MS) moves out of the coverage area of one base station (BS) to that of another. Mobile WiMAX supports three different types of handover mechanisms, namely, the hard handover, the Fast Base Station Switching (FBSS) and the Micro-Diversity Handover (MDHO). Out of these, the hard handover is the default handover mechanism whereas the other two are the optional schemes. Also, FBSS and MDHO provide better performance in comparison to hard handover, when it comes to dealing with the high-speed multimedia applications. However, they require a complex architecture and are very expensive to implement. So, hard handover is the commonly used technique accepted by the mobile broadband wireless user community including Mobile WiMAX users. The existing Mobile WiMAX hard handover mechanism suffers from multiple shortcomings when it comes to providing fast and reliable handovers. These shortcomings include lengthy handover decision process, lengthy and unreliable procedure of selecting the next BS, i.e., the target BS (TBS) for handover, occurrence of frequent and unwanted handovers, long connection disruption times (CDT), wastage of channel resources, etc. Out of these, reducing the handover latency and improving the handover reliability are the two issues that our present work has focused on. While the process of selecting the TBS for handover adds to the overall delay in completing the process of handover, choosing a wrong TBS for handover increases the chance of further unwanted handovers to occur or even a call drop to occur. The latter greatly hampers the reliability of a handover. In order to contribute to the solution of the above two problems of slow handover and unreliable handover, this Thesis proposes and investigates three handover techniques, which have been called Handover Techniques 1, 2 and 3, respectively. Out of these three techniques, the first two are fully MS-controlled while the third one is a dominantly serving BS-controlled. In Handover Techniques 1 and 2, which share between them some amount of commonness of ideas, the MS not only itself determines the need for a handover but also self-tracks its own independent movement with respect to the location of the (static) neighboring BSs (NBS). N both these handover techniques, the MS performs distance estimation of the NBSs from the signal strength received from the NBSs. But they (the two handover techniques) employ different kinds of “lookahead” techniques to independently choose, as the TBS, that NBS to which the MS is most likely to come nearest in the future. Being MS-controlled, both Handover Technique 1 and Handover Technique 2 put minimal handover-related workload on their respective SBSs who thus remain free to offer services to many more MSs. This interesting capability of the two handover techniques can increase the scalability of the WiMAX network considerably. In Handover Technique 3, which is a BS-controlled one with some assistance received from the MS, the SBS employs three different criteria or parameters to select the TBS. The first criterion, a novel one, is the orientation matching between the MS’s direction of motion and the geolocation of each NBS. The other two criteria are the current load of each NBS (the load provides an indication of a BS’s current QoS capabilities) and the signal strength received by the MS from each NBS. The BS assigns scores to each NBS against each of the three independent parameters and selects the TBS, which obtains the highest weighted average score among the NBSs. All three handover techniques are validated using simulation methods. While Handover Techniques 1 and 2 are simulated using Qualnet network simulator, for Handover Technique 3, we had to design, with barest minimum capability, our own simulation environment, using Python. Results of simulation showed that for Handover Techniques 1 and 2, it is possible to achieve around 45% improvement (approx) in the overall handover time by using the two proposed handover techniques. The emphasis in the simulation of the Handover Technique 3 was on studying its reliability in producing correct handovers rather than how fast handovers are. Five different arbitrary pre-defined movement paths of the MS were studied. Results showed that with orientation matching or orientation matching together with signal strength, reliability was extremely good, provided the pre-defined paths were reasonably linear. But reliability fell considerably when relatively large loads were also considered along with orientation matching and signal strength. Finally, the comparison between the proposed handover techniques in this Thesis and few other similar techniques in Mobile WiMAX proposed by other researchers showed that our techniques are better in terms providing fast, reliable and intelligent handovers in Mobile WiMAX networks, with scalability being an added feature.

La quinta generación de redes móviles (5G) se encuentra a la vuelta de la esquina. Se espera provea de beneficios extraordinarios a la población y que resuelva la mayoría de los problemas de las redes 4G actuales. El éxito de 5G, cuya primera fase de estandarización ha sido completada, depende de tres pilares: comunicaciones tipo-máquina masivas, banda ancha móvil mejorada y comunicaciones ultra fiables y de baja latencia (mMTC, eMBB y URLLC, respectivamente). En esta tesis nos enfocamos en el primer pilar de 5G, mMTC, pero también proveemos una solución para lograr eMBB en escenarios de distribución masiva de contenidos. Específicamente, las principales contribuciones son en las áreas de: 1) soporte eficiente de mMTC en redes celulares; 2) acceso aleatorio para el reporte de eventos en redes inalámbricas de sensores (WSNs); y 3) cooperación para la distribución masiva de contenidos en redes celulares. En el apartado de mMTC en redes celulares, esta tesis provee un análisis profundo del desempeño del procedimiento de acceso aleatorio, que es la forma mediante la cual los dispositivos móviles acceden a la red. Estos análisis fueron inicialmente llevados a cabo por simulaciones y, posteriormente, por medio de un modelo analítico. Ambos modelos fueron desarrollados específicamente para este propósito e incluyen uno de los esquemas de control de acceso más prometedores: access class barring (ACB). Nuestro modelo es uno de los más precisos que se pueden encontrar en la literatura y el único que incorpora el esquema de ACB. Los resultados obtenidos por medio de este modelo y por simulación son claros: los accesos altamente sincronizados que ocurren en aplicaciones de mMTC pueden causar congestión severa en el canal de acceso. Por otro lado, también son claros en que esta congestión se puede prevenir con una adecuada configuración del ACB. Sin embargo, los parámetros de configuración del ACB deben ser continuamente adaptados a la intensidad de accesos para poder obtener un desempeño óptimo. En la tesis se propone una solución práctica a este problema en la forma de un esquema de configuración automática para el ACB; lo llamamos ACBC. Los resultados muestran que nuestro esquema puede lograr un desempeño muy cercano al óptimo sin importar la intensidad de los accesos. Asimismo, puede ser directamente implementado en redes celulares para soportar el tráfico mMTC, ya que ha sido diseñado teniendo en cuenta los estándares del 3GPP. Además de los análisis descritos anteriormente para redes celulares, se realiza un análisis general para aplicaciones de contadores inteligentes. Es decir, estudiamos un escenario de mMTC desde la perspectiva de las WSNs. Específicamente, desarrollamos un modelo híbrido para el análisis de desempeño y la optimización de protocolos de WSNs de acceso aleatorio y basados en cluster. Los resultados muestran la utilidad de escuchar el medio inalámbrico para minimizar el número de transmisiones y también de modificar las probabilidades de transmisión después de una colisión. En lo que respecta a eMBB, nos enfocamos en un escenario de distribución masiva de contenidos, en el que un mismo contenido es enviado de forma simultánea a un gran número de usuarios móviles. Este escenario es problemático, ya que las estaciones base de la red celular no cuentan con mecanismos eficientes de multicast o broadcast. Por lo tanto, la solución que se adopta comúnmente es la de replicar e contenido para cada uno de los usuarios que lo soliciten; está claro que esto es altamente ineficiente. Para resolver este problema, proponemos el uso de esquemas de network coding y de arquitecturas cooperativas llamadas nubes móviles. En concreto, desarrollamos un protocolo para la distribución masiva de contenidos, junto con un modelo analítico para su optimización. Los resultados demuestran que el modelo propuesto es simple y preciso, y que el protocolo puede reducir el con
La cinquena generació de xarxes mòbils (5G) es troba molt a la vora. S'espera que proveïsca de beneficis extraordinaris a la població i que resolga la majoria dels problemes de les xarxes 4G actuals. L'èxit de 5G, per a la qual ja ha sigut completada la primera fase del qual d'estandardització, depén de tres pilars: comunicacions tipus-màquina massives, banda ampla mòbil millorada, i comunicacions ultra fiables i de baixa latència (mMTC, eMBB i URLLC, respectivament, per les seues sigles en anglés). En aquesta tesi ens enfoquem en el primer pilar de 5G, mMTC, però també proveïm una solució per a aconseguir eMBB en escenaris de distribució massiva de continguts. Específicament, les principals contribucions són en les àrees de: 1) suport eficient de mMTC en xarxes cel·lulars; 2) accés aleatori per al report d'esdeveniments en xarxes sense fils de sensors (WSNs); i 3) cooperació per a la distribució massiva de continguts en xarxes cel·lulars. En l'apartat de mMTC en xarxes cel·lulars, aquesta tesi realitza una anàlisi profunda de l'acompliment del procediment d'accés aleatori, que és la forma mitjançant la qual els dispositius mòbils accedeixen a la xarxa. Aquestes anàlisis van ser inicialment dutes per mitjà de simulacions i, posteriorment, per mitjà d'un model analític. Els models van ser desenvolupats específicament per a aquest propòsit i inclouen un dels esquemes de control d'accés més prometedors: el access class barring (ACB). El nostre model és un dels més precisos que es poden trobar i l'únic que incorpora l'esquema d'ACB. Els resultats obtinguts per mitjà d'aquest model i per simulació són clars: els accessos altament sincronitzats que ocorren en aplicacions de mMTC poden causar congestió severa en el canal d'accés. D'altra banda, també són clars en què aquesta congestió es pot previndre amb una adequada configuració de l'ACB. No obstant això, els paràmetres de configuració de l'ACB han de ser contínuament adaptats a la intensitat d'accessos per a poder obtindre unes prestacions òptimes. En la tesi es proposa una solució pràctica a aquest problema en la forma d'un esquema de configuració automàtica per a l'ACB; l'anomenem ACBC. Els resultats mostren que el nostre esquema pot aconseguir un acompliment molt proper a l'òptim sense importar la intensitat dels accessos. Així mateix, pot ser directament implementat en xarxes cel·lulars per a suportar el trànsit mMTC, ja que ha sigut dissenyat tenint en compte els estàndards del 3GPP. A més de les anàlisis descrites anteriorment per a xarxes cel·lulars, es realitza una anàlisi general per a aplicacions de comptadors intel·ligents. És a dir, estudiem un escenari de mMTC des de la perspectiva de les WSNs. Específicament, desenvolupem un model híbrid per a l'anàlisi de prestacions i l'optimització de protocols de WSNs d'accés aleatori i basats en clúster. Els resultats mostren la utilitat d'escoltar el mitjà sense fil per a minimitzar el nombre de transmissions i també de modificar les probabilitats de transmissió després d'una col·lisió. Pel que fa a eMBB, ens enfoquem en un escenari de distribució massiva de continguts, en el qual un mateix contingut és enviat de forma simultània a un gran nombre d'usuaris mòbils. Aquest escenari és problemàtic, ja que les estacions base de la xarxa cel·lular no compten amb mecanismes eficients de multicast o broadcast. Per tant, la solució que s'adopta comunament és la de replicar el contingut per a cadascun dels usuaris que ho sol·liciten; és clar que això és altament ineficient. Per a resoldre aquest problema, proposem l'ús d'esquemes de network coding i d'arquitectures cooperatives anomenades núvols mòbils. En concret, desenvolupem un protocol per a realitzar la distribució massiva de continguts de forma eficient, juntament amb un model analític per a la seua optimització. Els resultats demostren que el model proposat és simple i precís
The 5th generation (5G) of mobile networks is just around the corner. It is expected to bring extraordinary benefits to the population and to solve the majority of the problems of current 4th generation (4G) systems. The success of 5G, whose first phase of standardization has concluded, relies in three pillars that correspond to its main use cases: massive machine-type communication (mMTC), enhanced mobile broadband (eMBB), and ultra-reliable low latency communication (URLLC). This thesis mainly focuses on the first pillar of 5G: mMTC, but also provides a solution for the eMBB in massive content delivery scenarios. Specifically, its main contributions are in the areas of: 1) efficient support of mMTC in cellular networks; 2) random access (RA) event-reporting in wireless sensor networks (WSNs); and 3) cooperative massive content delivery in cellular networks. Regarding mMTC in cellular networks, this thesis provides a thorough performance analysis of the RA procedure (RAP), used by the mobile devices to switch from idle to connected mode. These analyses were first conducted by simulation and then by an analytical model; both of these were developed with this specific purpose and include one of the most promising access control schemes: the access class barring (ACB). To the best of our knowledge, this is one of the most accurate analytical models reported in the literature and the only one that incorporates the ACB scheme. Our results clearly show that the highly-synchronized accesses that occur in mMTC applications can lead to severe congestion. On the other hand, it is also clear that congestion can be prevented with an adequate configuration of the ACB scheme. However, the configuration parameters of the ACB scheme must be continuously adapted to the intensity of access attempts if an optimal performance is to be obtained. We developed a practical solution to this problem in the form of a scheme to automatically configure the ACB; we call it access class barring configuration (ACBC) scheme. The results show that our ACBC scheme leads to a near-optimal performance regardless of the intensity of access attempts. Furthermore, it can be directly implemented in 3rd Generation Partnership Project (3GPP) cellular systems to efficiently handle mMTC because it has been designed to comply with the 3GPP standards. In addition to the analyses described above for cellular networks, a general analysis for smart metering applications is performed. That is, we study an mMTC scenario from the perspective of event detection and reporting WSNs. Specifically, we provide a hybrid model for the performance analysis and optimization of cluster-based RA WSN protocols. Results showcase the utility of overhearing to minimize the number of packet transmissions, but also of the adaptation of transmission parameters after a collision occurs. Building on this, we are able to provide some guidelines that can drastically increase the performance of a wide range of RA protocols and systems in event reporting applications. Regarding eMBB, we focus on a massive content delivery scenario in which the exact same content is transmitted to a large number of mobile users simultaneously. Such a scenario may arise, for example, with video streaming services that offer a particularly popular content. This is a problematic scenario because cellular base stations have no efficient multicast or broadcast mechanisms. Hence, the traditional solution is to replicate the content for each requesting user, which is highly inefficient. To solve this problem, we propose the use of network coding (NC) schemes in combination with cooperative architectures named mobile clouds (MCs). Specifically, we develop a protocol for efficient massive content delivery, along with the analytical model for its optimization. Results show the proposed model is simple and accurate, and the protocol can lead to energy savings of up to 37 percent when compared to the traditional approach.
Leyva Mayorga, I. (2018). On reliable and energy efficient massive wireless communications: the road to 5G [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/115484
TESIS

Orientador: Varese Salvador Timóteo
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Tecnologia
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Resumo: Este projeto consiste no desenvolvimento de um modelo de simulação para serviços multimídia em redes móveis de terceira geração. Inicialmente foram simulados serviços de voz com diferentes cenários de tráfego e posteriormente serviços de dados e vídeo. Para o trabalho foi considerado que o núcleo da rede atende à demanda de acesso, de modo que é necessário modelar apenas a interação entre os terminais móveis e a rede de acesso por rádio. A validação do modelo de simulação foi feita tentando descrever o acesso em redes reais, por exemplo, usando como referência valores estimados para o número de tentativas de chamadas no cenário de pior caso (Busy Hour Call Attempts). As simulações foram realizadas por eventos discretos, baseadas em variáveis aleatórias e métodos de Monte Carlo. O software ARENA, projetado exatamente para este tipo de modelo, foi utilizado nas simulações, já que o sistema em questão tem sua operação baseada em serviços cujos intervalos de requisição e durações podem ser representadas por distribuições conhecidas
Abstract: This project develops a simulation model for multimedia services of the third generation mobile network. Initially it was simulated voice services with different traffic scenarios and later video and data services. For this assignment was considered that the core of the network achieves the access demands, thus it is only necessary to model the interaction between the mobile terminal and the radio access network. The validation of the simulation model was done in order to describe the real network access, e.g., estimated values were used as reference for the number of call attempts in the worst case scenario (Busy Hour Call Attempts). The simulations were carried out by discrete events based on random variables and Monte Carlo methods. The ARENA software, designed exactly for this type of model, was used in the simulations because this system has its operation based on services whose request intervals and durations of the system can be represented by known distributions
Mestrado
Tecnologia e Inovação
Mestre em Tecnologia

This work deals with provisioning of communication services via satellites for collectively mobile user groups in a heterogeneous network with several radio access technologies. The extended use of personalised user equipment beyond the coverage of one single terrestrial network by means of a satellite transport link, represents an increasingly important trend in mobile satellite communication. This trend is confirmed by the commercial introduction of broadband satellite communication to mobile terminals mounted on vehicles, trains, ships or aircraft. This work provides a consequent and structured approach for provisioning of services to broadband satellite terminals for mobile user groups and addresses: -- a systematic satellite communication system design process for collective mobile terminals; -- mobile satellite modelling at a wide range of frequencies, including current and potential frequencies; -- an optimised Pointing Acquisition and Tracking (PAT) system design including characterisation of moments for vehicle types of all mobile scenarios; -- a general hierarchical multi-service dimensioning methodology for collectively mobile user groups, including voice, data, and multimedia services; -- an aeronautical system dimensioning scheme with (capacity and handover) requirements analysis and evaluation of results for different satellite scenarios.

Abstact 1 - Over the past few years, mobile broadband technologies and speeds have greatly increased in the European Union, reaching an ever larger share of broadband consumers. These changes have implications for broadband market competition. In the past, mobile services offered slow but mobile internet whereas fixed services offered faster but fixed internet. Fixed and mobile broad-band were therefore obviously complementary services. While mobile broadband speeds have significantly increased over the latest years, fixed broadband is remaining rather a fixed technol-ogy. Consequently, if mobile broadband becomes fast enough considering some consumers’ needs, we believe that the same consumers will choose to use only the mobile broadband tech-nology (who by itself offers high-speed and mobility) instead of both fixed and mobile broad-band technologies. As a result, we may observe an increasing trend towards fixed to mobile substitution. Our study investigates empirically this trend. More specifically, it analyzes the im-pact of mobile broadband technology evolution - through 4G adoption - on fixed to mobile sub-stitution in the 28 European countries from 2009 until 2015. The few studies examining this sub-ject show that fixed to mobile substitution exists although none of these studies analyze the evo-lution of this substitution. The results confirm a significant existence of a fixed to mobile substi-tution in the EU, and show that this substitution is more than doubled when a country adopts 4G. The growing competitive pressure from mobile operators also provides fixed operators with incentives to acquire – or merge with – mobile operators. This fact should be a concern for policy makers as it could have harmful consequences for competition and investment on the broad-band market.
Abstract 2 - Whereas open science – i.e. publishing articles in scientific journals – had been largely studied on the academic side, there is still a need to explore the subject on the industry side. This study spe-cifically analyzes the role of academic institutions in firms’ scientific publications and uses a novel approach to explore the subject. Publications issued from collaborations with academic institutions are indeed differentiated from other publications. The first type of publications is considered as an indicator of firms’ collaborative activities with academic institutions whereas the second type of publications is considered as the result of firms’ strategies and/or firms’ capa-bilities to publish. This study provides evidence that industry publications are a valuable signal to attract academic partners. In addition, this study provides evidence that potential academic partners are more willing to team up with firms’ researchers who have proven their ability to achieve high-quality research/publications without the help of academic partners. Finally, the study provides evidence that past successful collaborations with academic partners lead the firm to reiterate such collaborations in the short term (2 years max.).
Abstract 3 - The objective of this study is twofold. First, it provides further knowledge on the subject of prof-itability of industry science/publications as it is not clear yet whether industry sci-ence/publications are profitable to firms. Second, it considers the central role of academic part-ners in the profitability of firms’ scientific publications as previous empirical studies do not con-sider such role. To investigate the subject, we perform several regressions with firms profits as dependent variable. The results provide evidence that the publication of scientific articles is not a profitable activity in itself (as it was demonstrated in two previous studies). Collaborations with academic institutions are the real basis of profitable results; the production of scientific publica-tions is only one of the consequences of these collaborations. This study also shows that not all collaborations are profitable, only collaborations in high-tech sectors that lead to high-quality publications lead to larger profits. Indeed, in their quest for survival and profitability, companies competing in high-tech sectors often need the help of academic partners to exploit scientific knowledge. On average, a rise of about 7% in successful collaborations (leading to high-quality publications) raises the profit of high-tech firms by about 1%. -
Abstract 4 - This chapter analyzes the factors influencing the quality of the output of I-A collaborations ap-proximated by the quality of the I-A co-publications. More specifically it analyzes two subjects that are typically complicated to study empirically because of a lack of available data: (1) it compares US and EU I-A partnerships and (2) it discusses if and how internet is a useful tool in I-A collaborations. The results empirically confirm that EU universities are less efficient partners than US universities when collaborating with the private sector. This study also demonstrates a much larger gap between EU and US academic partners in high-tech sectors. Finally, the results provide evidence that broadband is a useful tool for international I-A collaborations although broadband is less important in the success of I-A international collaborations in high-tech sectors compared to lower-tech sectors.
Doctorat en Sciences économiques et de gestion
info:eu-repo/semantics/nonPublished

Rapid convergence of heterogeneous wireless communication technologies such as Wireless Local Area Networks (WLAN), 4G: LTE/LTE-Advanced Mobile Broadband, 5G and Worldwide Interoperability for Microwave Access (WiMAX), attract new opportunities for ubiquitous connectivity enabling collaborative usage. Hence, it is predicted that the ever-increasing use of wireless Internet demands a significant increase in wireless broadband throughput. However, to maintain reliable and seamless connectivity wireless devices entail simultaneous multi-gateway connections. Therefore, emerging technologies should be capable of performing secure roaming between the diverse wireless networks. Nevertheless, vertical handover (roaming) and seamless connectivity involve overcoming not only the incompatibility issues between the different wireless technologies but also the incompatibility issues amongst the authentication mechanisms used in the various wireless networks. For seamless connectivity, wireless devices need to authenticate in a timely fashion with the different types of wireless networks. However, the authentication mechanisms used in these wireless networks can be specific and fitting only to those wireless technologies. Hence, roaming becomes a major challenge due to the incompatible authentication mechanisms, parameters and credentials. Further, users demand a single but unique set of credentials to authenticate the wireless devices in the heterogeneous wireless environment. In other words, future heterogeneous networks demand a coordinated authentication mechanism for vertical handover with the ability to use a single but unique set of credentials enabling secure and fast roaming.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Information and Communication Technology
Science, Environment, Engineering and Technology
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Over the last few years, there has been a signifi cant rise in the mobile broadband users worldwide. Recently, operators around the world have been improving the 3G networks by providing Dual Carrier-High Speed Packet Access+ (DC-HSPA+) services in both uplink and downlink to the users. However, the delay performance of the operational DC-HSPA+ networks is not focused. Firstly, we investigate and analyze the e ffect of operator service on One-Way Delay (OWD) and Jitter. Secondly, we investigate the treatment of protocols by 3G network for random packet sizes and random Inter Packet Duration (IPD). Thirdly, we investigate the eff ect of background load on OWD for packets generated at very low rate. Fourthly, we investigate the impact of constant IPD and streaming. Fifthly, we investigate the effects of shrinking the interval of IPD on OWD in 3G networks. Lastly, we investigate the OWD for Constant-Bit-Rate (CBR) and Variable-Bit-Rate (VBR) transmission patterns. Firstly, results show that OWD in the DC-HSPA+ networks is lower compared to the OWD in the preceding HSUPA networks and OWD strongly depends on packet-size at lower rates. Secondly, the 3G networks treat User Datagram Protocol (UDP), Transmission Control Protocol (TCP) and Internet Control Message Protocol (ICMP) protocols similarly for random packet size and random IPD. Thirdly, at high rates OWD depends on E-TFCE-DCH Transport Format Combination (ETFC) grants. Thirdly, the results also indicate that background load has a signi ficant impact on the end-to-end OWD. Fourthly, for low rates, OWD depends on packet sizes and for high rates OWD depends on IPD and for higher rates, OWD depends on E-TFC grants. Fifthly, we also observe: Shrinking the interval of IPD does not necessarily improve the OWD performance. Lastly, results also indicate that the VBR pattern has a better OWD performance than the CBR pattern for low transmission rates.

Secure information exchanges over cyberspace is on the increase due to the convergence of wireless and mobile access technologies in all businesses. Accordingly, with the proliferation of diverse multicast group service subscriptions that are possible to co-exist within a single broadband network, there is also huge demand by the mobile subscribers to ubiquitously access these services over high speed broadband using their portable devices. Likewise, the Network Providers (NPs) invest hugely in infrastructure deployment to disseminate these services efficiently and concomitantly. Therefore, cyber security in any business is obligatory to restrict access of disseminated services to only authorised personnel. This becomes a vital requirement for a successful commercialisation of exchanged group services. The standard way to achieve cyber security in a wireless mobile multicast communication environment is through confidentiality using Group Key Management (GKM).The existing GKM schemes for secure wireless multicast from literature only target single group service confidentiality; however, the adoption of multiple group service confidentiality in them involve inefficient management of keys that induce huge performance overheads unbearable for real time computing. Therefore, a novel authenticated GKM scheme for multiple multicast group subscriptions known as slot based multiple group key management (SMGKM) is proposed. In the SMGKM, the handovers move across diverse decentralised clusters of homogeneous or heterogeneous wireless access network technologies while participating in multiple group service subscriptions. Unlike the conventional art, the SMGKM advances its security by integrating location based authentication and GKM functions. Both functions are securely offloaded from the Domain Key Distributor (DKD) to the intermediate cluster controllers, Area Key Distributors (AKDs), in a distributed fashion, using the proposed location based authenticated membership list (SKDL). A significant upgrade of fast handoff performance with reduced performance overheads of the SMGKM scheme is achieved. The developed numerical analysis and the simulation results display significant resource economy in terms of reduced rekeying transmission, communication bandwidth and storage overheads while providing enhanced security. The performance of the SMGKM in a high speed environment is also evaluated and has demonstrated that SMGKM outperforms the previous work. Finally, the SMGKM correctness against various attacks is verified using BAN logic, the eminent tool for analysing the widely deployed security protocols. The security analysis demonstrates that SMGKM can counteract the security flaws and redundancies identified in the chosen related art.

1. Rohling H. (2011). OFDM Concepts of Future Communication Systems. Springer. doi: 10.1007/978-3-642-17496-42. 2. Chiueh Tzi-Dar. Baseband Receiver Design for Wireless MIMO-OFDM Communications / Tzi-Dar Chiueh, Pei-Yun Tsai, I-Wei Lai 2nd ed. John Wiley & Sons Singapore Pte. Ltd., 2012. 3. Myronchuk, O., Shpylka, O., & Zhuk, S. (2020). Two-stage Channel Frequency Response Estimation in OFDM Systems. Path of Science, 6(2), 1001-1007. doi: http://dx.doi.org/10.22178/pos.55-1 4. Myronchuk O. Algorithm Of Channel Frequency Response Estimation In Orthogonal Frequency Division Multiplexing Systems Based On Kalman Filter / O. Myronchuk, O. Shpylka, S. Zhuk // 2020 IEEE 15th International Conference on Advanced Trends in Radioelectronics, Telecommunications and Computer Engineering (TCSET), Lviv-Slavske, Ukraine, 2020, pp. 31-34, doi: 10.1109/TCSET49122.2020.235385. 5. Мирончук А. Ю. Метод оценивания частотной характеристики канала в OFDM системах на основе фильтрации и экстраполяции пилот-сигналов / А.Ю. Мирончук, А.А. Шпилька, С.Я. Жук // Вестник НТУУ "КПИ". Серия Радиотехника. Радиоаппаратостроение. – 2019. №78. – С. 36 42. doi: 10.20535/RADAP.2019.78.36-42. 6. Шпилька, А. А., & Жук, С. Я. (2010). Совместная интерполяция данных и фильтрация параметров многолучевого канала связи. Известия высших учебных заведений. Радиоэлектроника, 53(1), 26–30. https://doi.org/10.20535/S0021347010010048 7. Shpylka, A.A., Zhuk, S.Y. Decoding of convolutional codes on a sliding window during signal propagation in a multipath communications channel. Radioelectron.Commun.Syst. 53, 497–501 (2010). https://doi.org/10.3103/S0735272710090086 8. Myronchuk O. Yu. Two-Stage Method for Joint Estimation of Information Symbols and Channel Frequency Response in OFDM Communication Systems / O. Yu. Myronchuk, A. A. Shpylka, S. Ya. Zhuk // Radioelectronics and Communications Systems. – 2020. Vol. 63. – No. 8, pp. 418 429. doi: 10.3103/S073527272008004X 9.Луцький М.Г., Корченко О.Г., Горніцька Д.А., Ярмошевич І.М. Модель оцінки якості експерта для підвищення об’єктивності експертиз у сфері інформаційної безпеки. Захист інформації. 2011. Том 13. Вип. 2(51). DOI: 10.18372/2410-7840.13.2022
Orthogonal frequency division multiplexing (OFDM) is widely used in modern digital communication systems such as digital video and audio broadcasting (ISDB-T, DVB-T, DVB-T2, DRM, DAB), wireless broadband networks (IEEE 802.16), local area networks (IEEE 802.11a, g, n), mobile communication systems (LTE, LTE Advanced) and other. The main advantages of OFDM are high spectrum efficiency and possibility to provide high data transmitting speeds.
Мультиплексування з ортогональним частотним поділом (OFDM) широко використовується в сучасних цифрових системах зв'язку, таких як цифрове відео- та аудіомовлення (ISDB-T, DVB-T, DVB-T2, DRM, DAB), бездротових широкосмугових мережах (IEEE 802.16), локальній мережі мережі (IEEE 802.11a, g, n), системи мобільного зв'язку (LTE, LTE Advanced) та інші. Основними перевагами OFDM є висока ефективність спектру та можливість забезпечити високі швидкості передачі даних.

This work concentrates on the application of diversity techniques and space time block coding for future mobile wireless communications. The initial system analysis employs a space-time coded OFDM transmitter over a multipath Rayleigh channel, and a receiver which uses a selection combining diversity technique. The performance of this combined scenario is characterised in terms of the bit error rate and throughput. A novel four element QOSTBC scheme is introduced, it is created by reforming the detection matrix of the original QOSTBC scheme, for which an orthogonal channel matrix is derived. This results in a computationally less complex linear decoding scheme as compared with the original QOSTBC. Space time coding schemes for three, four and eight transmitters were also derived using a Hadamard matrix. The practical optimization of multi-antenna networks is studied for realistic indoor and mixed propagation scenarios. The starting point is a detailed analysis of the throughput and field strength distributions for a commercial dual band 802.11n MIMO radio operating indoors in a variety of line of sight and non-line of sight scenarios. The physical model of the space is based on architectural schematics, and realistic propagation data for the construction materials. The modelling is then extended and generalized to a multi-storey indoor environment, and a large mixed site for indoor and outdoor channels based on the Bradford University campus. The implications for the physical layer are also explored through the specification of antenna envelope correlation coefficients. Initially this is for an antenna module configuration with two independent antennas in close proximity. An operational method is proposed using the scattering parameters of the system and which incorporates the intrinsic power losses of the radiating elements. The method is extended to estimate the envelope correlation coefficient for any two elements in a general (N,N) MIMO antenna array. Three examples are presented to validate this technique, and very close agreement is shown to exist between this method and the full electromagnetic analysis using the far field antenna radiation patterns.

This work concentrates on the application of diversity techniques and space time block coding for future mobile wireless communications. The initial system analysis employs a space-time coded OFDM transmitter over a multipath Rayleigh channel, and a receiver which uses a selection combining diversity technique. The performance of this combined scenario is characterised in terms of the bit error rate and throughput. A novel four element QOSTBC scheme is introduced, it is created by reforming the detection matrix of the original QOSTBC scheme, for which an orthogonal channel matrix is derived. This results in a computationally less complex linear decoding scheme as compared with the original QOSTBC. Space time coding schemes for three, four and eight transmitters were also derived using a Hadamard matrix. The practical optimization of multi-antenna networks is studied for realistic indoor and mixed propagation scenarios. The starting point is a detailed analysis of the throughput and field strength distributions for a commercial dual band 802.11n MIMO radio operating indoors in a variety of line of sight and non-line of sight scenarios. The physical model of the space is based on architectural schematics, and realistic propagation data for the construction materials. The modelling is then extended and generalized to a multi-storey indoor environment, and a large mixed site for indoor and outdoor channels based on the Bradford University campus. The implications for the physical layer are also explored through the specification of antenna envelope correlation coefficients. Initially this is for an antenna module configuration with two independent antennas in close proximity. An operational method is proposed using the scattering parameters of the system and which incorporates the intrinsic power losses of the radiating elements. The method is extended to estimate the envelope correlation coefficient for any two elements in a general (N,N) MIMO antenna array. Three examples are presented to validate this technique, and very close agreement is shown to exist between this method and the full electromagnetic analysis using the far field antenna radiation patterns.

Communication tools such as text-based instant messaging, voice and video relay services, real-time video chat and mobile SMS and MMS have successfully been used among Deaf people. Several years of field research with a local Deaf community revealed that disadvantaged South African Deaf 
people preferred to communicate with both Deaf and hearing peers in South African Sign Language as opposed to text. Synchronous video chat and video 
relay services provided such opportunities. Both types of services are commonly available in developed regions, but not in developing countries like South 
Africa. This thesis reports on a workaround approach to design and develop an asynchronous video communication tool that adapted synchronous video 
 
codecs to store-and-forward video delivery. This novel asynchronous video tool provided high quality South African Sign Language video chat at the 
expense of some additional latency. Synchronous video codec adaptation consisted of comparing codecs, and choosing one to optimise in order to 
minimise latency and preserve video quality. Traditional quality of service metrics only addressed real-time video quality and related services. There was no 
uch standard for asynchronous video communication. Therefore, we also enhanced traditional objective video quality metrics with subjective 
assessment metrics conducted with the local Deaf community.

博士
國立中央大學
通訊工程學系
103
In recent years, because of the increased prevalence of mobile broadband network and the rapid development of social network service (SNS) and emerging services, it attracts numerous users to access the services through various types of smart devices at any location. However, due to the diverse smart devices and emerging mobile services, different types of devices and services have different requirements of mobile broadband network and quality of service. Due to limitation of mobile broadband spectrum resources, network component capability, and battery lifetime, how to balance resource scheduling, power consumption, and user experience will become more challenging. In this dissertation, we discuss signaling in 3G Environment for SNS first. To save power, a smart device was designed to release a data path immediately or to follow standards for transitioning to a power saving state. To provide better interaction, SNS was relevant power design Stay connected with the mechanism, the mechanism described above will produce a large number of signaling burden. To examine the signaling effects, this study analyzed measurements of signaling introduced by diverse smart devices when these devices run SNS in a real operator environment. The measurement results indicated that a high number of RRC related signaling messages are produced when a smart device runs a SNS, and the generated signaling messages introduce a heavy computational burden on the control plane. A possible enhancement approach is proposed and we expect the approach can reduce the signaling storm. The signaling fingerprints can be applied to establish signaling models for analyzing the performance of control planes. In downlink long-term evolution, we propose quality of service (QoS) aware scheme (QAS) and buffer aware scheme (BAS) scheduling consider the QoS with user channel conditions and buffer of user equipment (UE) with the user channel status, respectively. And determines the scheduling priority based on a designed heuristic weighting function. In proposed QAS, the simulation results show the proposed scheme improves power consumption in the case of video-streaming service but not HTTP service. The simulation results show that the proposed scheme allocates resources more fairly than other schemes used for comparison. To avoid too many UEs contending the limited radio resources and reduce power consumption, the proposed BAS estimates the allowable maximum number of UE. The simulation results show the proposed BAS achieve achieves less streaming delivery time and generates less signaling overhead than the best CQI scheme when the traffic load is heavy and high resolution video streaming sources.

碩士
國立交通大學
資訊科學與工程研究所
103
A system is defined to monitor and manage mobile broadband 4G LTE network. Network failure detection is the main function of this system. The network failures in mobile broadband network impact telecom services. It causes great loss to business. The current management systems used in the LTE network mostly deal with problems located in local domains. There are few systems used for monitoring the whole LTE network and evaluating network performance comprehensively. With the fast development of mobile broadband network and the increase of user requirements, the data transmission abilities and the capacities of network equipment are under great demand. Hence the comprehensive monitoring of LTE network is important to detect network failures and locate the fault node in a timely manner. This thesis research is based on the LTE network environment supported by Mobile Broadband Laboratory (BML) of National Chiao Tung University (NCTU). We designed and realized a system for LTE network failure detection. The system integrates traditional network management technology with LTE system architecture. It takes the network resources allocation into consideration to detect failure caused by unbalanced resource allocation and resource preemption.

碩士
國立彰化師範大學
資訊管理學系所
95
In recent years, Internet network technology and application have been developing rapidly. Each advanced nation proactively goes planning perspective information communication policies, so as to expect to drive the information communication related technological industry, and to grow up with perfect broadband network infrastructure and application service, then upgrade the national competitiveness. Among them, wireless network should have become the focal point of Internet City development, with the characteristics of no restriction of time and place. Establishing in a wide range of and Access Point (AP) and other wireless devices in the city, the wireless network that to provide to urban citizen for use is named the Public Wireless Local Area Network (PWLAN). The growth rate of utilization in service market of PWLAN is not as good as expectancy in recent years. This research expects to be able to find out the influence factors of will of using the Public Wireless Local Area Network, let government understand what are the influence factors, also share to Wireless Internet Service Providers (WISP) for reference, so as to design the PWLAN infrastructure and relevant service that could meet the demands of citizen who use them. This research adopt model by Venkatesh et al., 2003, Unified Theory of Acceptance and Use of Technology (UTAUT) in ' Policy Executor ' positions to design a new questionnaire according to finds out of internet users’ influence factors from their behavioral intention, then analyze according to the structure after verifying and data collected, in order to learn that influences factors of will of using 'Mobile Taichung Wireless Broadband Network '. Then offer ' Policy Executor ' to revise the foundation of the operational model. This research carried on the convenience sample survey to those who use ‘ e-Taichung Website’ access and Taichung City government ‘Mobile Taichung Wireless Broadband Network’(Asia Pacific Broadband Telecom constructed) on-line area, and with the statistical analysis of SPSS software. The result of study shows: (1) The factor influencing of will of using ‘Mobile Taichung Wireless Broadband Network’ can be summed up for ' Performance Expectancy’ and 'Effort Expectancy '; (2) 'Behavioral Intention' is the only influence factor for the Use Behavior; (3) In the moderators’ analysis, only ‘Offer Expectancy’vs.’Behavioral Intention’ path analysis got significant positive influence on usage by: a. the users’ gender and b.the using experience. That is, they are significant moderators of these models and the others are not significant. In the management implication, in order to improve users’ behavioral intention to the PWLAN, and then raise benefit of PWLAN, the responsible institution which is in the progress of the PWLAN construction, should offer the citizen free on-line learning course. Not only offering full and clear course, but also let the user understand the benefit PWLAN will bring us. Besides, offer more opportunities for practice. All above action could improve the consciousness to the PWLAN such as users’ ‘Performance Expectancy’ and ‘Offer Expectancy’, etc. Secondly, to those WLAN users and the male, their behavioral intention is significant influenced by ‘Offer Expectancy’. Therefore, the responsible institution should design more training courses and promotion programs for these two kinds of users, in order to improve the PWLAN benefit.

碩士
龍華科技大學
企業管理系碩士班
107
In response to the changes of consumers’ demand, the growth of technology applications rapidly keeps up with time. This revolution speeds up the development of mobile devices and e-commerce that further influence consumers on their need of wireless networks. However, does it influence consumers’ demand for landline due to the rapid development of wireless networks? This is the topic that the study attempts to explore. Based on the theories of the technology acceptance model, this study targeted broadband users and optical fiber network and ADSL users in the urban environment where there are high density of population and mobile broadband base stations. The stratified sampling method was used in the study, and 269 valid copies of the questionnaire were collected. The results of data analysis show that perceived usefulness, perceived ease, and 5G service cognition have a positive influence on the satisfaction of optical fiber network and ADSL users. The satisfaction of optical fiber network and ADSL users also has a positive influence on repurchase intention. In addition, consumers’ satisfaction has a mediating effect among perceived usefulness, perceived ease, 5G service cognition, and repurchase intentions. Based on the results of the data analyses, this study proposes relevant suggestion and implication for the telecom industry, technology and new ventures, traditional industries, and the government.

Indiana University-Purdue University Indianapolis (IUPUI)
With the rapid growth in wireless mobile communication technology, Vehicular Ad-hoc Network (VANET) has emerged as a promising method to effectively solve transportation-related issues. So far, most of researches on VANETs have been conducted with simulations as the real-world experiment is expensive. A core problem affecting the fidelity of simulation is the mobility model employed. In this thesis, a sophisticated traffic simulator capable of generating realistic vehicle traces is introduced. Combined with network simulator NS-2, we used this tool to evaluate the general performance of several routing protocols and studied the impact of intersections on simulation results. We show that static nodes near the intersection tend to become more active in packet delivery with higher transferred throughput.

碩士
國立中正大學
資訊工程研究所
107
Long Term Evolution (LTE) is the current mobile network technology. However, the network functions serving LTE are mostly implemented as dedicated hardwares, which leads to poor flexibility to module network functions and makes current LTE networks unable to meet the requirements of future mobile networks. Therefore, network function virtualization is considered one of the key technologies for developing future mobile networks. The functions, which are virtualized, can run on universal servers instead of conventional hardware-dedicated entities. For operators, it is important for efficient deploying virtualization network functions into mobile networks because not all applications need to use all the functions. For example, the typical scenarios defined in the 5G can be divided into enhanced mobile broadband (eMBB), massive machine type of communication (mMTC), and ultra-reliable and low latency communication (URLLC). However, their characteristics are different, so the functions will be used according to the requirements of each service. In this paper, we mainly refactor the network functions for the eMBB service. We proposed a method with quantitative analysis for refactoring the current control plane and user plane separation of evolved packet core nodes (CUPS EPC) architecture and 5G Core (5GC) network. We indicated the functions of the entities in CUPS EPC and 5GC, and listed corresponding strings according to the procedures in each architecture; then, we used two indicators and 2-means clustering to determine whether the functions, which in the corresponding strings, are merged. After performing the above method, we derived the refactored architectures. Additionally, we designed the procedures to verify the feasibility of the refactored architectures. To compare the performance of refactored CUPS EPC with CUPS EPC architecture and refactored 5GC with 5GC architecture, we evaluated them in terms of signaling cost, queueing delay time, and resource allocation cost. The results show that our refactored architectures have lower latency and more efficient resource utilization than original architectures. Furthermore, we conducted a simulation test with OMNET++ to validate the correctness of the derived formulas.

Unlike traditional cellular networks, where voice calls dominate the network traffic, modern mobile traffic is created by of a mixture of both voice and broadband data services. The heterogeneous mixture of voice and data services in mobile broadband networks includes voice calls, web browsing, file transfers, video streaming, and social media applications. Consequently, network planning and radio resource management strategies must be aware of the quality of experience perceived by the users using various types of applications. In this report, we explore the traffic characteristics, scheduling and resource allocation strategies, and user experience models in mobile broadband networks.
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博士
國立交通大學
資訊科學與工程研究所
98
In the recent years, wireless broadband access is gaining more popularity. Among all wireless data access technologies, the IEEE 802.11 WLANs (wireless local area networks) provide an easy and low cost solution for users to build their own local area networks while the IEEE 802.16 WMANs (wireless metropolitan area networks) provide a wireless solution to substitute the wire line last-mile Internet access. For mobile wireless users, high data rate, QoS (quality of service) guaranteed and continuous access, and long device operation time are always important issues for wireless networks. In this dissertation, we study the power and resource management in mobile broadband networks, which is composed of three major works. In the ‾rst work, we propose a mobile broadband network architecture which provides a group of mobile users broadband wireless access by attaching multiple wireless interfaces on the mobile gateway. In the second work, we discuss the resource management issue over the mobile broadband networks which considers how to manage wireless resource distribution and user mobility such that an on-going call can have guaranteed QoS and continuous connectivity. Finally, in the third work, we discuss the power management issue over the mobile broadband networks which studies the power saving class (PSC) management problem for the mobile gateway and mobile users which are equipped with IEEE 802.16e interfaces. In the first work, we develop a mobile broadband network architecture to provide broadband wireless access and support network mobility for a group of mobile users inside the network, where the mobility management is maintained by SIP (session initiation protocol). We propose to form a mobile ad hoc network (MANET) by a group of mobile stations (MSs). The MANET is connected to the outside world via a mobile gateway, which connects to the intra MANET by some IEEE 802.11 interfaces and attaches to the Internet through more external wireless interfaces (such as IEEE 802.11, WiMAX, PHS, and 3/3.5G interfaces). By aggregating multiple external interfaces of different wireless technologies in the gateway, mobile users are allowed to have a broadband wireless access. In the second work, we propose to design resource management mechanism by exploiting the session information carried by the SIP messages. Then, considering handoff and physical rate adaptation issues caused by mobility and wireless channel variation, we further enhance the resource management mechanism. Observing that current wireless MAC protocols all support QoS and CAC (call admission control), it is attractive to us to design a cross-layer resource management mechanism by integrating the QoS information from the application layer and the QoS mechanisms supported by the MAC layer. The proposed cross-layer scheme takes handoff and multi-rate environment into consideration. When wireless resource is stringent, we can dynamically adjust the resource distribution among existing calls by controlling their supporting codecs and frame rates. This not only takes care of calls in bad channel conditions, but also can accept more calls. In addition, to maintain continuous network continuity during handoff, we also develop a seamless post-handoff mechanism for secured wireless networks. In the last work, we focus on the PSC management problem for IEEE 802.16e interfaces. This issue happens to the mobile broadband networks when the mobile gateway acts as an IEEE 802.16 relay and the mobile users are equipped with IEEE 802.16e interfaces to access the Internet via the gateway. In this part, we propose four PSC management algorithms for IEEE 802.16e wireless networks. In the four schemes, three consider a base station (BS)-MS pair, one refers to multiple MSs under a BS. For each individual MS, IEEE 802.16e defines PSCs to manage its sleep. However, the standard does not describe how to define and manage PSCs for flows. Existing works all consider only the strictest delay bound among flows to control the sleep of single or multiple MSs. Therefore, for single MS, we propose to use multiple PSCs to schedule the sleep of the MS such that the sleep schedule can more accurately capture the QoS of flows and make the MS sleep more. Based on the same motivation, for multiple MSs, we also propose to schedule each MS's sleep according to each of their QoS characteristics. These lead to less energy consumption, more efficient use of bandwidth, and more compact listening windows.

博士
國立交通大學
電信工程系所
98
The growing demand for mobile Internet and wireless multimedia applications has motivated the development of broadband wireless-access technologies in recent years. While various broadband wireless-access technologies are under development at this time, mobile WiMAX based on IEEE 802.16 standards is the leading technology already in service today. This dissertation deals with some problems regarding IEEE 802.16-based mobile broadband wireless networks. Specifically, four topics are investigated: an adaptively direct communication approach for subscriber stations (SSs) in an IEEE 802.16 point-to-multipoint (PMP) network, a predictive motion and interference-based scheduling algorithm for mobile stations (MSs) with direct communication, a flexible listening window adjustment approach, and a statistical sleep window control approach for IEEE 802.16m sleep mode operations. A flexible and contention-free communication approach is proposed to support direct communication between SSs in an IEEE 802.16 PMP network. The base station (BS) is coordinating and arranging specific time periods for the two SSs that are actively involved in packet transmission. According to the channel conditions among the BS and SSs, the packet transmission operation is switched between the direct link and indirect links in the proposed approach, which improves the bandwidth utilization and consequently increases the user throughput. Based on the procedures mentioned above, a scheduling algorithm for each pair of MSs that is expected to conduct direct communication is presented. Both the interference region and feasible region for the pair of MSs to perform direct communication are studied and calculated. Based on these two types of information, the algorithm properly arranges the MSs to conduct direct communication in either downlink subframe or uplink subframe, or to communicate with the conventional communication manner, i.e., via the BS. Furthermore, by incorporating the motion prediction mechanism with the scheduling algorithm, the control overheads regarding the updates of MSs positions can be efficiently reduced. On the other hand, in order to enhance the efficiency of energy conservation, a flexible listening window adjustment approach for an MS in the sleep mode with real-time traffic is present. Instead of window-based operation specified in the IEEE Std. 802.16e-2005, a cycle-based mechanism is considered in the proposed approach. With the consideration of tolerable delay constraint, the approach dynamically adjusts the ratio of listening window to sleep window for each sleep cycle based on the number of both buffered and retransmitted packets. It is worthwhile to mention that the concept of flexible listening window adjustment approach has been proposed by the author and is adopted in the IEEE 802.16m standard draft. For an MS in the sleep mode with non-real-time downlink traffic, a statistical sleep window control approach is provided based on the concepts of IEEE 802.16m sleep mode operation. The proposed approach constructs a discrete-time Markov-modulated Poisson process for representing the states of non-real-time traffic. Furthermore, a partially observable Markov decision process is exploited to conjecture the present traffic state. Based on the estimated traffic state and the considerations of tolerable delay and/or queue size, two suboptimal policies for maximizing energy conservation are proposed within the approach.

碩士
元智大學
資訊工程學系
96
In this paper, we develop two generalized analytical models which were basic on two-dimensional Markov chain model to investigate the performance of two proposed scheme and compared them with each other. Another contribution of this paper is to propose two Multi-Guard Channel Schemes (MGCS) for multi-threshold and multi-rate services. The purpose of MGCS is proposed to guarantee the quality of service for multimedia wireless cellular networks. We can adaptively adjust the threshold of MGCS according to the current network traffic situation and QoS status, and performance measurements can help for improving the blocking and dropping probabilities. The analytical results show that MGCS 2 achieves better results on the call dropping probability and call blocking probability.

博士
國立臺灣大學
電子工程學研究所
107
The focus of this thesis is to develop algorithmic approaches to resolve challenges of supporting eMBB in cooperative networks. Specifically, we resolve the challenges of network densification, self-interference cancellation, and maintaining profitability. For the challenge of network densification, we consider employing widely linear precoding to mitigate the interference-limited performance issue in wireless cooperative networks. For rate optimization in interference limited network, improper Gaussian signaling has shown its capability to outperform the conventional proper Gaussian signaling. In the first part of this thesis, we study a weighted sum-rate maximization problem with improper Gaussian signaling for the multiple-input multiple-output interference broadcast channel (MIMO-IBC). To solve this nonconvex and NP-hard problem, we propose an effective separate covariance and pseudo-covariance matrices optimization algorithm. In the covariance optimization, a weighted minimum mean square error (WMMSE) algorithm is adopted, and, in the pseudo-covariance optimization, an alternating optimization (AO) algorithm is proposed, which guarantees convergence to a stationary solution and ensures a sum-rate improvement over proper Gaussian signaling. An alternating direction method of multipliers (ADMM)-based multi-agent distributed algorithm is proposed to solve an AO subproblem with the globally optimal solution in a parallel and scalable fashion. The proposed scheme exhibits favorable convergence, optimality, and complexity properties for future large-scale networks. Simulation results demonstrate the superior sum-rate performance of the proposed algorithm as compared to existing schemes with proper as well as improper Gaussian signaling under various network configurations. Recently, cooperative transmission with full-duplex (FD) relays has gained lots of attention because it can extend service coverage and improve network capacity. However, the self-interference of the FD relay greatly degrade the end-to-end system throughput. As a result, we propose using improper Gaussian signaling (IGS) in joint source and relay transmission to achieve a better LI resistance and, as a result, a better end-to-end system throughput in energy harvesting (EH) enabled FD relaying systems. An alternating optimization (AO) algorithm is proposed to solve the challenging design problem of finding the optimal transmission with IGS at both the source and relay, as well as the optimal power-splitting (PS) factor at the EH-enabled relay. The relationship between the PS factor and the optimal pseudo-variances is derived in closed form. Numerical results demonstrate the superior throughput performance yielded by IGS at the same LI level, and suggest the possibility of employing IGS as a replacement of a sophisticated LI canceller in practical FD relaying systems. Since mobile network operators not only need to satisfy user needs but also have to reduce operating cost (mainly electricity cost) to maintain long-term profitability under strict market competition, energy efficiency (EE), defined as capacity per energy cost, becomes a popular metric for designing mobile networks. For user-centric services, however, the metric of quality of experience (QoE) is more suitable than the metric of capacity or data rate. Therefore, in the third part of this thesis, we consider a novel network design metric quality-energy efficiency (QEE), defined as the quality of experience achieved per energy consumed. By using QEE as the performance objective, we propose a framework to design user-centric green cloud-based radio access network (C-RAN). In particular, the issues of fairness and fronthaul power consumption in C-RAN are taken into account. An efficient approach to solving the non-convex max-min optimization problem for the design of user-centric green C-RAN is proposed. Simulation results validate the near-optimal performance of the proposed algorithm and demonstrate the value of the proposed QEE metric for the design of energy-efficient user-centric C-RAN.

This thesis analyzes the Bit Error Rate (BER) performance of Orthogonal Frequency Division Multiplexing (OFDM) systems in mobile multi-hop relaying channels. We consider the uplink scenario and quantify the effects of mobile channel impairments such as Doppler Shift due to user mobility per hop, high-power amplifier distortions when amplifying the transmitted/relayed OFDM symbol per hop, as well as the cumulative effects of these impairments over multi-hop relaying channels. It is shown that the resulting inter-carrier interference (ICI) due to the cumulative effects of the phase noise generated by these impairments per hop becomes very significant in a multi-hop relaying communication system, and severely degrades the BER performance of the system. Simulation results agree well with, and validate the analysis.
Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2011-05-05 15:15:39.576

碩士
大同大學
資訊經營學系(所)
95
The IEEE 802.16e is an emerging standard for mobile wireless broadband access systems that provides flexible sleep-mode operations for mobile subscriber stations (MSSs) to conserve energy consumption. In this paper, we proposed an algorithm to schedule packets for power saving with quality of service (QoS) based on IEEE 802.16e. Due to the popularization of multimedia services such as Voice over IP (VoIP) and MPEG video, the different types of QoS coexist in one MSS. Thus, we consider that different types of QoS should be scheduled in the same time and integrate the sleep duration in one MSS. The packets would be scheduled successively to reduce the number of status transitions under QoS requirements of delay and jitter. The scheduling algorithm provides the guarantee of QoS for the connections in the MSSs and minimizes the energy consumption of the MSSs. Simulation results show that our proposed power saving scheduling algorithm can reduce the energy consumption and prolong lifetime of the MSSs.

碩士
國立中央大學
通訊工程研究所
94
This paper proposes a new mechanism of setting up QoS connection – RSVP and 802.16 operating integrated procedure, it can work in the IEEE 802.16 and IEEE 802.11e hybrid network, and how to transfer QoS link from the serving SS to target SS when the mobile node moved from serving SS to the target SS. Furthermore, we propose a mechanism of dynamic bandwidth management, it make the real-time services get high priority to acquire bandwidth when the real-time services do the handoff procedure and reduce handoff call blocking probability when the resource is insufficient. Simulation results show the mechanism of dynamic bandwidth management can meet the handoff call blocking probability is reduced when the real-time services do the handoff procedure if the parameters are configured appropriately.

A research report submitted to the Faculty of Humanities, University of the Witwatersrand, in partial fulfilment of the requirements for the degree of Master of Arts (in the field of ICT Policy and Regulation), October 2017
Spectrum management reforms involve a departure from state-commanded administrative methods to market-driven property rights and or technology-enabled spectrum commons. This study explores spectrum management reforms that have been undertaken in the last decade, between 2006 and 2016, in the Southern African Development Community (SADC) region, with specific focus on the mobile broadband (MBB) industry. As a result, only spectrum bands allocated to terrestrial mobile and identified for International Mobile Telecommunications (IMT) by the International Telecommunication Union (ITU) in ITU Region 1 (Europe, Middle East and Africa) were considered. The purpose was to firstly analyse the progress thus far in reforming spectrum management practice in the region and secondly to critically analyse the effects of these reforms on the MBB industry in SADC within the framework of high demand for more spectrum as the cornerstone for rapid diffusion of MBB. Using a constructivist case study methodology, qualitative research was conducted in three SADC countries, namely, Botswana, Zambia and South Africa, representing small, medium and large markets respectively. The study draws on published documents such as policies, legislation, regulations and directly from individuals tasked with spectrum management in public and private sector organisations in these countries. The findings reveal that several market-driven reforms such as technology and service neutrality, spectrum re-farming and administrative incentive pricing (AIP), together with technology-enabled reforms such as commons or license-exempt spectrum for MBB technologies are all becoming widespread in the region. However, secondary trading and auctions have been stillborn concepts, partly due to market concentration concerns and appropriateness issues. The artificial scarcity of MBB spectrum supply in SADC is laid bare against a backdrop of general scarcity for demand and a discord over how this spectrum should be assigned and to whom. Vast amounts of allocated mobile spectrum in SADC lie fallow or are encumbered by other services such as broadcasting or at times are historically assigned to Fixed Wireless Access (FWA) applications. Analysis of the data from these three country case study provides insights that may be relevant to many other countries in the region. In conclusion, the study advances that the implementation of spectrum management reforms should be nuanced as these can impact, positively or negatively, on the distributive agenda of government. This research further advances knowledge by positing a novel conceptual framework for spectrum management reform based on the finding that the latter is not a binary exercise of a departure from administrative approach to either a market-driven or a technology-enabled one. However, spectrum management reform can be a continuum on which different elements of administrative, market-driven and technology-enabled approaches can be applied to varying degrees, depending on the respective country’s context.
XL2019