New technologies are expected to play a major role for wireless cellular systems beyond the existing 4G paradigm. The need for several orders of magnitude increase in system capacity has led to the proliferation of low-powered cellular layers overlaid on the existing macrocell layer. This type of network consisting of different cellular layers, each with their unique characteristics including transmission power and frequency of operation among others is termed as a heterogeneous network (HetNet). The emergence of HetNets leads to several research challenges and calls for a profound rethinking of several existing approaches for mobility management and interference management among other issues.

Yes / Exploring innovative cellular architectures to achieve enhanced system capacity and good coverage has become a critical issue towards realizing the next generation of wireless communications. In this context, this paper proposes a novel concept of Universal Intelligent Small Cell (UniSCell) for enabling the densification of the next generation of cellular networks. The main motivating factors behind the proposed small cell concept are the need of public infrastructure reengineering and the recent advances in several enabling technologies such as spectrum awareness, adaptive beamforming, source localization, new multiplexing schemes, etc. In this paper, first, we highlight the main concepts of the proposed small cell platform. Subsequently, we present two deployment scenarios taking into account of both technical and business aspects. Then, we describe the key future technologies for enabling the proposed UniScell Concept and present an use case example with the help of numerical results. Finally, we conclude this paper by providing some interesting future recommendations.

Future wireless networks are expected to be highly heterogeneous and ultra dense with different types of small cells underlaid with traditional macro cells. In the presence of hundreds of different types of small cells, centralized control and manual intervention in network management will be inefficient and expensive. In this case, self-organization has been proposed as a key feature in future wireless networks. In a self-organizing network, the nodes are expected to take individual decisions on their behavior. Therefore, individual decision making in resource allocation (i.e., Distributed Resource Allocation) is of vital important. The objective of this thesis is to develop a distributed resource allocation framework for self-organizing small cell networks. Game theory is a powerful mathematical tool which can model and analyze interactive decision making problems of the agents with conflicting interests. Therefore, it is a well-appropriate tool for modeling the distributed resource allocation problem of small cell networks. In this thesis, I consider three different scenarios of distributed resource allocation in self-organizing small cell networks i.e., i). Distributed downlink power and spectrum allocation to ensure fairness for a small cell network of base stations with bounded rationality, ii). Distributed downlink power control for an ultra dense small cell network of base stations with energy constraints, iii). Distributed joint uplink-downlink power control for a small cell network of possibly deceitful nodes with full-duplexing capabilities. Specifically, I utilize evolutionary games, mean field games, and repeated games to model and analyze the three aforementioned scenarios. I also use stochastic geometry, which is a very powerful mathematical tool that can model the characteristics of the networks with random topologies, to design the payoff functions for the formulated evolutionary game and the mean field game. / October 2016

Wireless backhaul communication and power transfer can make the deployment of outdoor small cells (SCs) more cost effective; thus, their rapid densification can be enabled. For the first time, solar cells can be leveraged for the two-fold function of energy harvesting (EH) and high speed optical wireless communication. In this thesis, two complementary concepts for power provision to SCs are researched using solar cells – the optical wireless power transfer (OWPT) in the nighttime and solar EH during daytime. A harvested power of 1W is considered to be required for an autonomous SC operation. The conditions of darkness – worst case scenario – are initially selected, because the SC needs to harvest power in the absence of ambient light. The best case scenario of daytime SC EH from sunlight is then explored to determine the required battery size and the additional power from optical sources. As a first approach, an indoor 5m experimental link is created using a white light-emitting diode for OWPT to an amorphous silicon (Si) solar panel. Despite the use of a large mirror for collimation, the harvested power and energy efficiency of the link are measured to be only 18:3mW and 0:1%, respectively. Up to five red laser diodes (LDs) with lenses and crystalline Si (c-Si) cells are used in a follow-up study to increase the link efficiency. A maximum power efficiency of 3:2% is measured for a link comprising two LDs and a mono-c-Si cell, and the efficiency of all of its components is determined. Also, the laser system is shown to achieve an improvement of the energy efficiency by 2:7 times compared with a state-of-the-art inductive power transfer system with dipole coils. Since the harvested power is only 25:7mW, an analytical model for an elliptical Gaussian beam is developed to determine the required number of LDs for harvesting 1W; this shows an estimated number of 61 red LDs with 50mW of output optical power per device. However, a beam enclosure of the developed Class 3B laser system of up to a 3:6m distance is required for eye safety. A simulation study is conducted in Zemax for the design of an outdoor 100m infrared wireless link able to harvest 1W under clear weather conditions. Harvesting 1:2W and meeting eye safety regulations for Class 1 are shown to be feasible by a 1550 nm laser link. The required number of laser power converters is estimated to be 47 with an area of 5 5mm2 per device. Also, the dimensions of the transmitter and receiver are considered to be acceptable for the practical application of SC EH. In the last part of this thesis, two multi-c-Si solar panels are initially used for EH in an outdoor environment during daytime. The power supply of at least 1W is shown to be achievable during hour periods under sunny and cloudy conditions. A maximum average power of 4:1W is measured in the partial presence of clouds using a 10W solar panel. Since the variability of weather conditions induces the harvested power to fluctuate with values of mW, the use of optical sources is required in periods of insufficient solar EH for SCs. Therefore, a hybrid solar/laser based EH design is proposed for a continuous annual SC provision of 1Win ‘darker’ places on earth such as Edinburgh, UK. The 10W multi-c-Si solar panel and the 1550 nm laser link are considered; thus, the feasibility of supplying the SC with at least 1Wper hour monthly using a battery with energy content of only 60Wh is shown through simulations. A maximum monthly average harvested power of 824mW is shown to be required by the 1550 nm laser system that has already been overachieved through simulations in Zemax.

There is a strong uptake of femtocell deployment as small cell application platforms in the upcoming LTE networks. In such two-tier networks of LTE-femtocell base stations, a large portion of the assigned spectrum is used sporadically leading to underutilisation of valuable frequency resources. Novel spectrum access techniques are necessary to solve these current spectrum inefficiency problems. Therefore, spectrum management solutions should have the features to improve spectrum access in both temporal and spatial manner. Cognitive Radio (CR) with the Dynamic Spectrum Access (DSA) is considered to be the key technology in this research in order to increase the spectrum efficiency. This is an effective solution to allow a group of Secondary Users (SUs) to share the radio spectrum initially allocated to the Primary User (PUs) at no interference. The core aim of this thesis is to develop new cognitive LTE-femtocell systems that offer a 4G vision, to facilitate the radio network management in order to increase the network capacity and further improve spectrum access probabilities. In this thesis, a new spectrum management model for cognitive radio networks is considered to enable a seamless integration of multi-access technology with existing networks. This involves the design of efficient resource allocation algorithms that are able to respond to the rapid changes in the dynamic wireless environment and primary users activities. Throughout this thesis a variety of network upgraded functions are developed using application simulation scenarios. Therefore, the proposed algorithms, mechanisms, methods, and system models are not restricted in the considered networks, but rather have a wider applicability to be used in other technologies. This thesis mainly investigates three aspects of research issues relating to the efficient management of cognitive networks: First, novel spectrum resource management modules are proposed to maximise the spectrum access by rapidly detecting the available transmission opportunities. Secondly, a developed pilot power controlling algorithm is introduced to minimise the power consumption by considering mobile position and application requirements. Also, there is investigation on the impact of deploying different numbers of femtocell base stations in LTE domain to identify the optimum cell size for future networks. Finally, a novel call admission control mechanism for mobility management is proposed to support seamless handover between LTE and femtocell domains. This is performed by assigning high speed mobile users to the LTE system to avoid unnecessary handovers. The proposed solutions were examined by simulation and numerical analysis to show the strength of cognitive femtocell deployment for the required applications. The results show that the new system design based on cognitive radio configuration enable an efficient resource management in terms of spectrum allocation, adaptive pilot power control, and mobile handover. The proposed framework and algorithms offer a novel spectrum management for self organised LTE-femtocell architecture. Eventually, this research shows that certain architectures fulfilling spectrum management requirements are implementable in practice and display good performance in dynamic wireless environments which recommends the consideration of CR systems in LTE and femtocell networks.

The rapid growth in wireless data traffic in recent years has placed a great strain on the wireless spectrum and the capacity of current wireless networks. In addition, the makeup of the typical wireless propagation environment is rapidly changing as a greater percentage of data traffic moves indoors, where the coverage of radio signals is poor. This dual fronted assault on coverage and capacity has meant that the tradition cellular model is no longer sustainable, as the gains from constructing new macrocells falls short of the increasing cost. The key emerging concept that can solve the aforementioned challenges is smaller base stations such as micro-, pico- and femto-cells collectively known as small cells. However with this solution come new challenges: while small cells are efficient at improving the indoor coverage and capacity; they compound the lack of spectrum even more and cause high levels of interference. Current channel models are not suited to characterise this interference as the small cells propagation environment is vast different. The result is that overall efficiency of the networks suffers. This thesis presents an investigation into the characteristics of the wireless propagation channel in small cell environments, including measurement, analysis, modelling, validation and extraction of channel data. Two comprehensive data collection campaigns were carried out, one of them employed a RUSK channel sounder and featured dual-polarised MIMO antennas. From the first dataset an empirical path loss model, adapted to typical indoor and outdoor scenarios found in small cell environments, was constructed using regression analysis and was validated using the second dataset. The model shows good accuracy for small cell environments and can be implemented in system level simulations quickly without much requirements.

No description available.

There is a prolific increase in the penetration of user devices such as smartphones and tablets. In addition, user expectations for higher Quality of Service (QoS), enhanced data rates and lower latencies are relentless. In this context, network densification through the dense deployment of small cell networks, underlaying the currently existing macrocell networks, is the most appealing approach to handle the aforementioned requirements. Small cell networks are capable of reusing the spectrum locally and providing most of the capacity while macrocell networks provide a blanket coverage for mobile user equipment (UEs). However, such setup imposes a lot of issues, among which, co-tier and cross-tier interference are the most challenging. To handle co-tier interference, I have proposed a semi-distributed (hierarchical) interference management scheme based on joint clustering and resource allocation (RA) for small cells. I have formulated the problem as a Mixed Integer Non-Linear Program (MINLP), whose solution was obtained by dividing the problem into two sub-problems, where the related tasks were shared between the Femto Gateway (FGW) and small cells. As for cross-tier interference, I have formulated RA problems for both the macrocell and small cells as optimization problems. In particular, I have introduced the idea of ``Tier-Awareness'' and studied the impact of the different RA policies in the macrocell tier on the small cells performance. I have shown that the RA policy in one tier should be carefully selected. In addition, I have formulated the RA problem for small cells as an optimization problem with an objective function that accounts for both RA and admission control (AC). Finally, I have studied cloud radio access network (C-RAN) of small cells which has been considered as a typical realization of a mobile network which is capable of supporting soft and green technologies in Fifth Generation (5G) networks, as well as a platform for the practical implementation of network multiple-input multiple-output (MIMO) and coordinated multi-point (CoMP) transmission concepts. / February 2016

Le déferlement mondial des services de télécommunications, impose, aux réseaux qui les supportent, d’augmenter de plus en plus leurs capacités afin de subvenir aux besoins de ses utilisateurs dont le nombre ne cesse de croître. Le spectre radio, ressource de base pour les communications sans fils, ne suit malheureusement pas cette croissance. Même si des marges réutilisables sont disponibles, leur accès est limité par des politiques strictes de gestion du spectre radio-fréquentiel. Pour remédier à cette situation, les organismes régulateurs des télécommunications se dirigent vers un paradigme de gestion plus flexible, en autorisant de nouvelles méthodes basées sur l’accès dynamique au spectre (DSA - dynamic spectrum access) et les radio cognitives (CR - cognitive radio). Dans ce travail doctoral, est proposée une nouvelle technique pour traiter la problématique de la disponibilité du spectre radio-fréquentiel. Appelée multiplexage fréquentiel par sous-espace de Vandermonde (VFDM -Vandermonde-subspace frequency division multiplexing), elle permet à deux technologies d’accès radio (RATs - radio access technologies) de fonctionner côte-a-côte dans un environnement de petites cellules CR. Ceci se fait en partageant la bande radio tout en protégeant des interférences les systèmes pour lesquels le spectre radio avait été originellement réservé. VFDM transmet les données pré-codées dans le noyau du canal interférant entre l’émetteur opportuniste et le récepteur originel en utilisant la sélectivité en fréquence des canaux et duplexage temporel (TDD - time division duplexing). Le travail de cette thèse propose une approche exhaustive du développement de la technologie VFDM, en allant des bases théoriques jusqu’à la démonstration de faisabilité. Ainsi, les bases théoriques proposées ont été en premier lieu analysées. Puis, en partant de ces bases théoriques, VFDM a été graduellement développé vers une chaîne émetteur-récepteur complète. Des résultats significatifs sont apparus à mi-chemin dans la phase de développement, comme par exemple, l’établissement de stratégies de précodage optimales ou la mise en évidence d‘aspects critiques lors de l’implémentation. Sous certaines conditions, VFDM permet aux réseaux secondaires opportunistes d’être utilisés en même temps que le réseau originel, aux seules contraintes de la connaissance des canaux et de l’accroissement de la complexité du système. Au travers des résultats obtenus en simulation, il a été démontré que des taux de transfert de données significatifs peuvent être atteints, et ce, malgré que les capacités de VFDM soient toujours limitées par la taille du sous-espace de Vandermonde du canal interfèrent primaire-secondaire. Finalement, la chaîne émetteur-récepteur développée démontre la faisabilité de cette méthode. / The global deployment of PCS is pushing for more and more network capacity to accommodate an exponentially growing user base. Radio spectrum, the basic resource in radio communications, unfortunately does not follow this growth. Even though the current spectrum usage leaves margins for re-use, it is limited by the current fixed spectrum management policies. To remediate this issue, spectrum regulators are switching to a flexible management paradigm, leveraging new DSA schemes based on CR. In this PhD work, a novel CR-DSA technology is introduced to address spectrum scarcity problem. Called VFDM, it allows two RAT to operate side-by-side in a small-cell CR setting, sharing the band while protecting the legacy system from interference. VFDM transmits data pre-coded on the null-space of the interfering cross channel (channel from the opportunistic transmitter to the legacy receiver), assuming frequency selectivity and TDD communications. This PhD work proposes a rather exhaustive approach to the development of VFDM: to go from the theoretical basis up to a proof-of-concept development. Initially the theoretical background, basis of the technique itself was introduced and analyzed. Then, VFDM was gradually developed from a pure mathematical concept up to a full transceiver. During this development, several important mid-way results were developed, such as the multi-user strategy for pre-coding and critical implementation aspects. VFDM, under certain constraints, has been shown to allow a secondary opportunistic network to successfully be installed along with a legacy primary one at merely the cost of channel knowledge and added complexity. By means of numerical examples, it has been shown that significative rates can be attained, even though VFDM's performance is constrained by the size of the Vandermonde-subspace of the interfering channel between the secondary transmitter and primary receiver. Finally, a working VFDM transceiver implementation is shown, providing a proof-of-concept of the technique.

CoordenaÃÃo de AperfeiÃoamento de NÃvel Superior / Os mÃtodos tradicionais de tratamento do cÃncer, como a quimioterapia e a radioterapia, embora sejam eficazes em vÃrios tipos de tumores, encontram freqÃentemente populaÃÃes de cÃlulas neoplÃsicas resistentes, alÃm de apresentarem uma baixa margem de seguranÃa para os pacientes. A utilizaÃÃo da hipertermia associada à quimioterapia e/ou radioterapia jà se encontra fartamente relatada como vantajosa na literatura especializada, principalmente em pacientes portadores de cÃncer em estÃdio avanÃado, submetidos previamente aos mÃtodos clÃssicos de tratamento. A aplicaÃÃo de calor nos tecidos atravÃs de ultrassom contÃnuo torna mais Ãgil Ãste procedimento e com eficÃcia comprovada. O uso dos antiangiogÃnicos tambÃm vem sendo relatado como eficaz na literatura especializada e atualmente, a lista destas substÃncias vem aumentando consideravelmente. O estudo da aÃÃo da hipertermia associada a alguns agentes antiangiogÃnicos tem sido sugerida uma vez que os vasos tumorais ao encontrarem-se dilatados, nÃo promoverÃo a diminuiÃÃo da temperatura no tecido tumoral e, consequentemente, os efeitos desta associaÃÃo serÃo mais intensos do que no tecido normal devendo contribuir para a morte celular. Objetiva-se neste trabalho, avaliar o efeito antitumoral e antiangiogÃnico da hipertermia induzida por US isolada e combinada com etoricoxibe e pegaptanibe,no carcinossarcoma de Walker 256 implantado na tela subcutÃnea do dorso de ratos por meio de utilizaÃÃo do modelo experimental de hipertermoterapia por US assim como o estudo dos efeitos da hipertermia por US isolada e em combinaÃÃo com etoricoxibe e pegaptanibe,na angiogÃnese tumoral.O mÃtodo utilizado para o estudo teve inÃcio com o implante de cÃlulas de tumor de Walker 256 no dorso de ratos Wistar machos. Os animais foram tratados com hipertermia aplicada atravÃs de aparelho de ultrassom, mantida a nÃvel de 45o C durante cinco minutos no terceiro dia apÃs a inoculaÃÃo e tambÃm tratados com etoricoxibe e pegaptanibe por via oral e intraperitoneal respectivamente a partir do dia da inoculaÃÃo. Cada grupo de animais foi submetido a medidas do crescimento tumoral durante o perÃodo de 30 dias, assim como tambÃm à avaliaÃÃo da microdensidade vascular atravÃs de estudo mesoscÃpico fotogrÃfico, validado pelo estudo microscÃpico. A aplicaÃÃo do calor atravÃs de aparelho de ultrasom demonstrou eficiÃncia e agilidade A hipertermia, o etoricoxibe e o pegaptanibe, apresentaram capacidade antiangiogÃnica, expressada tanto pela curva de sobrevida, como pela avaliaÃÃo da microdensidade vascular. Particularmente, a hipertermia isoladamente apresentou um efeito antiangiogÃnico significativo tanto na curva de crescimento tumoral como na diminuiÃÃo da densidade microvascular. A associaÃÃo da hipertermia com o pegaptanibe, demonstrou uma eficiÃncia na diminuiÃÃo da densidade microvascular significativamente maior do que os demais grupos. O modelo de aplicaÃÃo de hipertermia gerada por um aparelho de ultrassom na modalidade contÃnua foi satisfatÃria, demonstrando ter sido efetiva tanto na diminuiÃÃo do crescimento tumoral, como na diminuiÃÃo da densidade microvascular. / The traditional methods of cancer treatment, like the chemotherapy and radiotherapy, even though they are effective in many types of tumours, they find frequently resistant neoplasic cellsâ population, beyond presenting a low security margin to the patients. The hyperthermia use associated to the chemotherapy and radiotherapy are plenty mentioned as profitable in the specialist literature, especially in patients with cancer in advanced stage, submitted previously to the classic methods of the treatment. The tissuesâ heat insertion through the continuous ultrasound becomes the procedure faster and with proved efficacy. The antiangiogenic use also is being related like effective in the specialist literature and, at this moment, the substancesâ list has grown vastly. The study of the hyperthermia action associated to antiangiogenic agents has been suggested, once the tumour vessels are dilated, would not promote the temperature reduction in the tumour vessels and, therefore, the effects of this association would be more intense than in the normal tissue, what might contribute to the death cell. The study objective is to evaluate the antitumor and antiangiogenic effect of the hyperthermia induced by isolated ultrasound and combined with etoricoxibe and pegaptanibe in the 256 Walker carcinossarcoma implanted in the subcutaneous back screen of mouse by using the hyperthermia experimental model by ultrasound, like the hyperthermia effects study by isolated ultrasound and linked with etoricoxibe and pegaptanibe, in the tumour angiogenesis. The method used describes the insertion of 256 Walker Tumour cells in the back of male Wistar mouse. The animals were treated with hyperthermia applied through the ultrasound equipment, kept to a 45 C level during five minutes in the third day after the inoculation and also treated with etoricoxibe and pegaptanibe by oral and intraperitoneal respectively since the inoculation day. Each animal group was submitted to a tumour growth measurement during a period of 30 days, as well as also a vascular microdensity evaluation through a photographic mesoscopic study, validated by the microscopic study. The heat application through the ultrasound equipment demonstrated efficiency and agility. The hyperthermia, the etoricoxibe and the pegaptanibe showed antiangiogenic capacity, expressed by the over life curve, and also by the vascular microdensity evaluation. Particularly, the isolated hyperthermia showed a significative antiangiogenic effect in the tumour growth curve and also in the decreasing of the micro vascular density. The association between the hyperthermia and the pegaptanibe demonstrated a greater efficiency in the reducing of the micro vascular density than the other groups. The hyperthermia application model generated by the ultrasound equipment in the continuous modality was satisfactory, demonstrating by being effective as much in the reducing of the tumour growth as in the decreasing of the micro vascular density.