Multiple resource reuse for device-to-device communication in future cellular networks

Aufgrund der stärkeren Verbreitung neuer mobiler Anwendungen, z.B. Autonomes Fahren, automatisierte Prozesssteuerung, intelligente Städte / Wohnen und taktiles Internet, nimmt - die Anzahl und Dichte von Geräten, die drahtlose Verbindungen erfordern, immer weiter zu. Dies erfordert effizientere Verfahren zur Nutzung des verfügbaren Frequenzspektrums für zellulare Netze. Um dieser Herausforderung zu begegnen, wurden Ansätze, wie die gemeinsame Nutzung von Frequenzen, vorgeschlagen, um die gesamte spektrale Effizienz zu verbessern. Die Device-to-Device Kommunikation (D2D) mit paralleler Übertragung zu einem zellularen Netz bietet eine Verbesserung der spektralen Effizienz durch die verstärkte gemeinsame Nutzung des verfügbaren zellularen Spektrums. Mit D2D kommunizieren Geräte in unmittelbarer Nähe direkt miteinander ohne oder mit nur einer minimalen Kontrolle über das Mobilfunknetz. Das 3rd Generation Partnership Project (3GPP) unterstützt durch Standardisierung die Integration von D2D in Mobilfunknetze, um die spektralen Effizienzgewinne bei der gemeinsamen Nutzung von Frequenzen unter Gewährleistung der Quality of Service (QoS) zu realisieren. Die Interferenzen zwischen D2D und zellularen Benutzern müssen jedoch während der gemeinsamen Nutzung des Spektrums kontrolliert werden, um diese Gewinne im Netzwerk zu erhalten. Die vorliegende Arbeit untersucht Lösungen, mit denen das Frequenzspektrum des Mobilfunknetzes mit D2D-Benutzern geteilt werden kann, welche sowohl die spektrale Effizienz maximieren als auch die QoS-Anforderungen aller Benutzer erfüllen (in Bezug auf das Signal-zu-Rausch-plus-Interferenz Verhältnis (SINR)). Die vorliegende Arbeit gliedert sich in zwei Teile: eine analytische und eine algorithmische Studie. Zunächst untersucht die analytische Studie den Ansatz für ein Interferenzmanagement, in welchem mehrere D2D-Benutzer das zellulare Spektrum gemeinsam nutzen. Dabei wird die Zuteilung einer einheitlichen Interferenzleistung (UIP) vorgeschlagen - ein Verfahren, bei dem alle D2D-Benutzer mit gleicher Interferenz an der Basisstation (BS) beitragen. Dieses Schema wird auf ein Szenario einer einzelnen Zelle angewendet, welches sehr positive Ergebnisse bei der Verbesserung der spektralen Effizienz erzielt, obwohl einige D2D-Benutzer ihre SINR-Schwellenwerte nicht erreichen können. Eine wesentliche Erkenntnis aus der analytischen Studie ist, dass eine räumliche Trennung zwischen Benutzern, die das Spektrum gemeinsam nutzen, wichtig ist, um ihre gegenseitige Beeinflussung zu minimieren. Die algorithmische Studie konzentriert sich daher auf die Auswahl geeigneter D2D-Benutzern. Zunächst werden räumliche Auswahlkriterien formuliert mit dem Ziel, mehrere D2D-Benutzer zu identifizieren, die das Spektrum eines bestimmten Mobilfunkbenutzers gemeinsam nutzen können, um die spektrale Effizienz zu maximieren, während alle Benutzer ihre SINR-Schwellenwerte erreichen. Danach werden basierend auf diesen Kriterien zwei Auswahlalgorithmen entwickelt. Der erste Algorithmus wählt opportunistisch D2D-Benutzer aus, die bei bestimmten Auswahlinstanzen die geringste Störung für andere das Spektrum gemeinsam nutzende Benutzer verursachen. Der zweite Algorithmus wählt zufällig alle D2D-Benutzer aus, die räumliche von anderen Benutzern getrennt sind, jedoch das Spektrum gemeinsam nutzen. Beide Algorithmen werden mit sehr positiven Ergebnissen durch Simulationen in einem Szenario einer einzelnen Zelle mit einer unterschiedlichen Anzahl von Benutzern vorgestellt. In einem Szenario mit mehreren Zellen, in welchem die Interferenz zwischen den Zellen die Leistungsfähigkeit beeinträchtigt, werden Verbesserungen an beiden Algorithmen vorgestellt, um die festgelegten Ziele zu erreichen. Diese Verbesserungen passen die Auswahlkriterien an, um: 1) keine D2D-Benutzer mit Zellenkante auszuwählen und 2) die Auswirkungen der gemeinsamen Nutzung des Frequenzspektrums zwischen benachbarten Zellen zu berücksichtigen. Die Arbeit zeigt deutlich, dass mithilfe eines geeigneten Auswahlkriteriums mehrere D2D Nutzer in der Lage sind, die gemeinsame Frequenzressource mit zellularen Nutzern zu teilen mit Erhöhung der gesamten spektralen Effizienz und Beibehaltung der QoS Anforderungen aller Nutzer. Die hierbei erbrachten Erkenntnisse können zusammen mit den vorhandenen Ergebnissen als Ausgangspunkt für weitere akademische Forschung sowie einer praktischen Anwendung dienen.Owing to the further proliferation of new mobile applications, e.g. autonomous driving, automated process control, smart cities/homes, and tactile internet, the number and density of devices requiring wireless connectivity continue to increase. This demands ever more efficient methods for utilizing the available frequency spectrum for cellular networks. To counter this challenge, approaches like spectrum sharing have been proposed as enablers to improve the overall spectral efficiency. Device to device communication (D2D) as an underlaying transmission to the cellular network presents spectral efficiency improvements through the increased sharing of the available cellular spectrum. In D2D, devices in close proximity communicate directly with each other having either minimal or no control from the cellular network. The third generation partnership project (3GPP) supports, through standardization, the integration of D2D within cellular networks in order to realize the spectral efficiency gains during spectrum sharing and user quality of service (QoS) guarantees. However, the interference between D2D and cellular users during spectrum sharing must be controlled to get these gains in the network. This thesis studies the solutions through which the cellular network's frequency spectrum can be shared with D2D users to concurrently maximize the spectral efficiency and achieve all users' QoS requirements (in terms of threshold signal-to-interference-plus-noise ratio (SINR)). The thesis is divided into two parts: an analytical study and an algorithmic study. First, the analytical study evaluates the framework for interference management when several D2D users share the cellular network's spectrum. Therein, uniform interference power (UIP) allocation -- a scheme where all D2D users contribute equal interference at the base station (BS), is proposed. This scheme is applied to a single-cell scenario with very positive results in improving spectral efficiency although some D2D users are unable to achieve their threshold SINRs. The main lesson from the analytical study is that spatial separation between users sharing spectrum is important to minimize their mutual interference. So the algorithmic study focuses on D2D-users selection. First, spatial selection criteria are formulated with the objective of identifying multiple D2D users that can share a given cellular user's spectrum to maximize spectral efficiency while all users achieve their threshold SINRs. Thereafter, based on these criteria, two selection algorithms are developed. The first algorithm opportunistically selects D2D users causing the least interference, at given selection instances, to other users sharing the spectrum. The second algorithm randomly selects any D2D users meeting the minimal required spatial separation from other users sharing the spectrum. Both algorithms are presented with very positive results in simulations that consider a single-cell scenario with varying number of users. In a multi-cell scenario, where the experienced inter-cell interference degrades performance, enhancements to both algorithms are applied to achieve the set objectives. These enhancements adapt the selection criteria to: $1$) not select cell-edge D2D users and $2$) take into account the effects of spectrum sharing between neighbouring cells. The thesis studies clearly showed that, using appropriate selection criteria, multiple D2D users can share a specific cellular user's spectrum resources to improve the network's spectral efficiency and achieve all users' QoS requirements. These findings together with other existing results on D2D spectrum resource reuse can be the starting point for further academic research and practical implementation

Implementação e avaliação no system generator de um sistema cooperativo para os futuros sistemas 5G

With the arrival of 5G it is expected the proliferation of services in the different fields such as healthcare, utility applications, industrial automation, 4K streaming, that the former networks can not provide. Additionally, the total number of wireless communication devices will escalate in such a manner that the already scarce available frequency bandwidth won’t be enough to pack the intended objectives. Cisco’s Annual Internet Report from 2018 predicts that by 2023 there will be nearly 30 billion devices capable of wireless communication. Due to the exponential expiation of both services and devices, the challenges upon both network data capacity and efficient radio resourse use will be greater than ever, thus the urgency for solutions is grand. Both the capacity for wireless communications and spectral efficiency are related to cell size and its users proximity to the access point. Thus, shortening the distance between the transmitter and the receiver improves both aspects of the network. This concept is what motivates the implementation of heterogeneous networks, HetNets, that are composed of many different small-cells, SCs, overlaid across the same coexisting area of a conventional macro-cell, shortening the distance between the cell users and its access point transceivers, granting a better coverage and higher data rates. However, the HetNets potential does not come without any challenges, as these networks suffer considerably from communication interference between cells. Although some interference management algorithms that allow coexistence between cells have been proposed in recent years, most of them were evaluated by software simulations and not implemented in real-time platforms. Therefore, this master thesis aims to give the first step on the implementation and evaluation of an interference mitigation technique in hardware. Specifically, it is assumed a downlink scenario composed by a macro-cell base station, a macro-cell primary user and a small cell user, with the aim of implementing an algorithm that eliminates the downlink interference that the base station may cause to the secondary users. The study was carried out using the System Generator DSP tool, which is a tool that generates code for hardware from schematics created in it. This tool also offers a wide range of blocks that help the creation, and fundamentally, the simulation and study of the system to be implemented, before being translated into hardware. The results obtained in this work are a faithful representation of the behavior of the implemented system, which can be used for a future application for FPGA.Com a chegada do 5G, espera-se a proliferação de serviços nas mais diversas áreas tal como assistência médica, automação industrial, transmissão em 4k, que não eram possíveis nas redes das gerações anteriores. Além deste fenómeno, o número total de dispositivos capazes de conexões wireless aumentará de tal maneira que a escassa largura de banda disponível não será suficiente para abranger os objetivos pretendidos. O Relatório Anual de 2018 sobre a Internet da Cisco prevê que até 2023 haverá quase 30 bilhões de dispositivos capazes de comunicação sem fio. Devido ao aumento exponencial de serviços e dispositivos, os desafios sobre a capacidade de dados da rede e o udo eficiente dos recursos de rádio serão maiores que nunca. Por estes motivos, a necessidade de soluções para estas lacunas é enorme. Tanto a capacidade da rede e o uso eficiente do espectro de frequências estão relacionados ao tamanho da célula e à proximidade dos usuários com o ponto de acesso da célula. Ao encurtar a distância entre o transmissor e o recetor ocorre um melhoramento destes dois aspetos da rede. Este é o principal conceito na implementação de redes heterogéneas, HetNets, que são compostas por diversas células pequenas que coexistem na área de uma macro célula convencional, diminuído a distância entre os utilizadores da célula e os pontos de acesso, garantindo uma melhor cobertura e taxa de dados mais elevadas. No entanto, o potencial das HatNets não vem sem nenhum custo, pois estas redes sofrem consideravelmente de interferência entre as células. Embora nos últimos anos foram propostos alguns algoritmos que permitem a coexistência das células, a maioria destes foi só testado em simulações de software e não em plataformas em tempo real. Por esse motivo, esta dissertação de mestrado visa dar o primeiro passo na implementação e a avaliação de uma técnica de mitigação de interferência em hardware. Mais especificamente no cenário de downlink entre uma estação base de uma macro célula, um utilizador primário da macro célula e um utilizador secundário de uma célula pequena, com o principal objetivo de cancelar a interferência que a estação base possa fazer ao utilizador secundário. O estudo foi realizado utilizando a ferramenta System Generator DSP, que é uma ferramenta que gera código para hardware a partir de esquemáticos criados na mesma. Esta ferramenta também oferece uma vasta gama de blocos que ajudam a criação, e fundamentalmente, a simulação e o estudo do sistema a implementar antes de ser traduzido para hardware. Os resultados obtidos neste trabalho são uma fiel representação do comportamento do sistema implementado. O quais podem ser utilizados para uma futura aplicação para FPGA.Mestrado em Engenharia Eletrónica e Telecomunicaçõe

Interference Aware Cognitive Femtocell Networks

Femtocells Access Points (FAP) are low power, plug and play home base stations which are designed to extend the cellular radio range in indoor environments where macrocell coverage is generally poor. They offer significant increases in data rates over a short range, enabling high speed wireless and mobile broadband services, with the femtocell network overlaid onto the macrocell in a dual-tier arrangement. In contrast to conventional cellular systems which are well planned, FAP are arbitrarily installed by the end users and this can create harmful interference to both collocated femtocell and macrocell users. The interference becomes particularly serious in high FAP density scenarios and compromises the ensuing data rate. Consequently, effective management of both cross and co-tier interference is a major design challenge in dual-tier networks. Since traditional radio resource management techniques and architectures for single-tier systems are either not applicable or operate inefficiently, innovative dual-tier approaches to intelligently manage interference are required. This thesis presents a number of original contributions to fulfill this objective including, a new hybrid cross-tier spectrum sharing model which builds upon an existing fractional frequency reuse technique to ensure minimal impact on the macro-tier resource allocation. A new flexible and adaptive virtual clustering framework is then formulated to alleviate co-tier interference in high FAP densities situations and finally, an intelligent coverage extension algorithm is developed to mitigate excessive femto-macrocell handovers, while upholding the required quality of service provision. This thesis contends that to exploit the undoubted potential of dual-tier, macro-femtocell architectures an interference awareness solution is necessary. Rigorous evidence confirms that noteworthy performance improvements can be achieved in the quality of the received signal and throughput by applying cognitive methods to manage interference

Study and Development of Power Control Schemes within a Cognitive Radio-based Game Theoretic Framework

Projecte final de carrera fet en col.laboració amb Nokia Siemens NetworksThe requirements of the International Telecommunication Union (ITU) for the 4th generation of mobile devices raised up to 100 Mbps for high and 1Gbps for low mobility conditions. Reaching such challenging targets requires the deployment of picocells and femtocells. These techniques permit to achieve large cell capacity but also lead to di culties in terms of interference. The GRACE algorithm, based on Cognitive Radio and Game Theory, has shown a fair balance between cell capacity and outage as well as short convergence time, low complexity and easy scalability. The aim of this work is to find an e cient power control algorithm that fits GRACE these goals. Therefore, a study of Cognitive Radio, Game Theory and Power Control algorithms is developed and a new power control algorithm is proposed. The simulation results show that the Fractional Power Control can increase notably the outage performance and the energy saving to the mobile devices