Small cells are deployed in a crowded areas with a high demand for both coverage and capacity. It is hard to address both of these requirements simultaneous with a conventional mobile network architecture based on macro cells. In many case a wire is not available to connect the small cell to the core of the mobile network. Under these circumstances a wireless link could be a convenient solution for the backhaul. In this master’s thesis IEEE 802.11n technology was evaluated to assess its suitability for backhaul from a small wireless cell. The performance of wireless equipment manufactured by several vendors has been measured. The results of these measurements were analyzed and compared to a set of requirements established for small cell backhaul. The analysis has affirmed that IEEE 802.11n is capable of providing sufficient performance to be used for small cell backhaul in various deployment scenarios. Note that in this thesis we include femtocells, picocells, wireless LAN access points, and other technologies in the category of "small cells". Another research questions of this master’s thesis is security of small cell backhaul. In addition to protecting the backhaul link itself, the security research investigated the safety of the whole mobile network architecture remodeled with the introduction of small cells. A mechanism to integrate secure small cells into a mobile network was developed. The results obtained during the project will be used as an input for product development activities in the company hosting the project. The resulting product could become the target of future wireless system performance measurements. / Små celler sätts ut i områden med höga krav på täckning och kapacitet. Det är svårt att adressera båda dessa krav samtidigt med en konventionell mobil nätverksarkitektur baserad på makro-celler. I många fall finns ingen kabel tillgänglig att koppla den lilla cellen till kärnan i det mobila nätverket. Under dessa omständigheter kan en trådlös länk vara en lämplig lösning för backhaul. I denna avhandling utvärderas IEEE 802.11n-teknikens lämplighet för backhaul av små celler. Prestandan hos trådlös utrustning tillverkad av flera olika tillverkare har mätts. Resultaten av dessa mätningar analyserades och jämfördes med en mängd krav uppsatta för backhaul av små celler. Analysen har förankrat att IEEE 802.11n är kapabel till att tillhandahålla tillräcklig prestanda för backhaul av små celler i diverse miljöer. Notera att i denna avhandling så inkluderas femto-celler, pico-celler, Wireless LAN-åtkomstpunkter, och andra teknologier i kategorin små celler". Andra forskningsfrågor berörda i avhandlingen är säkerhet vid backhaul av små celler. Utöver att skydda backhaul-länken själv så undersökte säkerhetsforskningen säkerheten av hela mobilnätsarkitekturen när små celler används i arkitekturen. En mekanism för att integrera säkra små celler i ett mobilnät utvecklades. De resultat som införskaffades under projektets genomförande kommer att användas som input till produktutvecklingsaktiviteter hos företaget som sponsrade projektet. Den resulterande produkten skulle kunna bli mål för framtida prestandamätningar av trådlösa system.

Face à la croissance exponentielle des réseaux mobiles très haut débit, les opérateurs de téléphonie mobile se sont lancé dans le déploiement des réseaux dits hiérarchiques (HetNet), composés par des sous-réseaux avec des caractéristiques divergentes en termes de type des cellules déployées et des technologies d’accès radio utilisées. Avec ce caractère hétérogène des réseaux cellulaire, l’exploitation de ces derniers devienne de plus en plus compliquée et coûteuse impliquant le déploiement, la configuration et la reconfiguration de stations de base et d’équipements de différentes caractéristiques. Ainsi, l’intégration dans les réseaux HetNet de fonctionnalités d’auto-configuration automatisant et simplifiant l’exploitation des réseaux deviennent une demande forte des opérateurs. Cette thèse a pour objectif l’étude et le développement de solutions de gestion dynamique de l’équilibrage de charges entre les différentes couches composant un même HetNet, pour une expérience utilisateur (QoE) améliorée. Dans ce contexte, une classe des algorithmes d’équilibrage de charges dite ‘équilibrage de charges par adaptation dynamique des paramètres de la procédure de handover’ est étudiée. Pour commencer, nous développons un modèle théorique basé sur des solutions et des outils de la géométrie stochastique et incorporant le caractère hétérogène des réseaux cellulaires. Ensuite nous exploitons ce modèle pour introduire des algorithmes d’adaptation des paramètres de handover basés sur la maximisation de la puissance reçue et du rapport signal/brouillage plus bruit (SINR). Nous exploitons ces résultats pour implémenter et étudier, par simulation à évènements discrets, des algorithmes d’équilibrage de charges dans le contexte des réseaux LTE HetNet auto-organisés basés sur les spécifications 3GPP. Ces travaux soulignent l’importance de l’équilibrage de charges afin de booster les performances des réseaux cellulaires en termes de débit global transmis, perte de paquets de données et utilisation optimisée des ressources radio. / High demands on mobile networks provide a fresh opportunity to migrate towardsmulti-tier deployments, denoted as heterogeneous network (HetNet), involving a mix of cell types and radio access technologies working together seamlessly. In this context, network optimisation functionalities such as load balancing have to be properly engineered so that HetNet benefit are fully exploited. This dissertation aims to develop tractable frameworks to model and analyze load balancing dynamics while incorporating the heterogeneous nature of cellular networks. In this context we investigate and analyze a class of load balancingstrategies, namely adaptive handover based load balancing strategies. These latter were firstly studied under the general heading of stochastic networks using independent and homogeneous Poisson point processes based network model. We propose a baseline model to characterize rate coverage and handover signalling in K-tier HetNet with a general maximum power based cell association and adaptive handover strategies. Tiers differ in terms of deployment density and cells characteristics (i.e. transmit power, bandwidth, and path loss exponent). One of the main outcomes is demonstrating the impact of offloading traffic from macro- to small-tier. This impact was studied in terms of rate coverage and HO signalling. Results show that enhancement in rate coverage is penalized by HO signalling overhead. Then appropriate algorithms of LB based adaptive HO are designed and their performance is evaluated by means of extensive system level simulations. These latter are conducted in 3GPP defined scenarios, including representation of mobility procedures in both connectedstate. Simulation results show that the proposed LB algorithms ensure performance enhancement in terms of network throughput, packet loss ratio, fairness and HO signalling.

With the continuous progress on autonomous vehicle and remote drivingtechniques, connection quality demands are changing compared withconventional quality of service. Vehicle to everything communication, asthe connectivity basis for these applications, has been built up on LongTerm Evolution basis, but due to various ethical and environmental issues,few implementations have been made in reality. Therefore simulation approachesare believed to provide valuable insights.To fully model an LTE vehicular network, in this work we first providea comparison study to select the preferable LTE simulator. Aimingto integrate communication nodes with mobility, a solution for simulationframework is developed based on a state-of-art comparison study on theexisting simulator frameworks. We then further develop the network simulator,and complement it with hybrid wireless channel modeling, channeland quality of service aware scheduler, and admission control strategies. Interms of instant optimization of the network, real-time access is emulatedfor external devices to communicate with the simulator. In this thesis,the evaluation of the framework performance considers two aspects: theperformance of the simulator in LTE V2X use case and the feasibility ofthe service, specifically, remote driving, under realistic network capacity.For our framework, the results indicate that it is feasible to realize remotedriving in an LTE urban scenario, but, as an example, we show that foran area of Kista, five vehicles could be hold by a base-station with guaranteedservice at most. / Med kontinuerliga framstegen p°a autonomt fordon och fj¨arrkontrollteknikf¨or¨andras kravet p°a anslutningskvalitet i j¨amf¨orelse med konventionell servicekvalitet.Fordon till allting (V2X) kommunikation, som anslutningsgrundf¨or dessa applikationer, har byggts upp p°a basis av Long TermEvolution (LTE) system, men p°a grund av olika etiska och milj¨om¨assigaproblem har f°a implementeringar gjorts i verkligheten. D¨arf¨or antas simuleringsmetoderge v¨ardefulla insikter.Att fullt ut modellera ett LTE-fordon n¨atverk, i det h¨ar arbetet ger vif¨orst en j¨amf¨orelsestudie f¨or att v¨alja den f¨oredragna LTE-simulatorn.I syfte att integrera kommunikationsnoder med r¨orlighet utvecklas enl¨osning f¨or ett simuleringsramverk baserat p°a en j¨amf¨orelsestudie p°a befintligasimulatorramar. Vi utvecklar sedan n¨atverkssimulatorn ytterligare,och kompletterar den med hybrid tr°adl¨os kanalmodellering, kanal ochservicekvalitetmedvetna schemal¨aggning och antagningskontrollstrategier.N¨ar det g¨aller direkt n¨atverksoptimering, emuleras realtidsanslutningav externa enheter f¨or att kommunicera med simulatorn. I denna avhandlingutv¨arderas ramverken i tv°a aspekter: simulatorns prestanda i LTEV2X-anv¨andningsomr°adet och genomf¨orbarheten av tj¨ansten, s¨arskilt fj¨arrk¨orning,under realistisk n¨atkapacitet. In v°ara ramverk visar resultaten att det ¨arm¨ojligt att realisera fj¨arrk¨orning i ett LTE-urbana scenario, men som exempelvisar vi att f¨or ett omr°ade i Kista skulle som mest fem fordon kunnask¨otas av en basstation med garanterad service.

[pt] O presente trabalho apresenta os resultados obtidos com simulações computacionais de interferência entre sistemas LTE e TV Digital na faixa de 700 MHz e de medições de campo. Os resultados da campanha de medições foram usados para validar uma ferramenta de simulação que permite a avaliação de interferência entre os sistemas SBTVD e LTE em diferentes cenários. A ferramenta foi, então, utilizada para analisar a probabilidade de interferência que depende da distância entre os sistemas, da potência de transmissão, do número de interferentes e outros parâmetros que permitem definir as condições para a coexistência harmoniosa dos sistemas. A partir da validação da ferramenta, cenários de interferência com múltiplos receptores LTE e DTV foram simulados, com o propósito de reproduzir problemas mais realistas. Na última etapa do trabalho, como estudo de caso, foi realizada uma avaliação de interferência do sistema LTE nos receptores de TV Digital em cenário representativo da região da zona sul do município do Rio de Janeiro. / [en] This work presents the results of computer simulations of the interference between LTE system and ISDB-TB Digital TV system in the 700 MHz band and field measurements. The results of the measurement campaign were used to validate a simulation tool that runs different scenarios between the SBTVD systems and LTE. The software tool was used to analyze the probability of interference and its dependence on the distance between systems, transmission power, number of interferers and other parameters, aiming to estimate the conditions for the coexistence of the systems. Once the software tool was validated, different interference scenarios with multiple LTE and DTV receivers were analyzed, in order to reproduce more realistic problems. In the last part of this study, an interference evaluation from LTE system on Digital TV receivers was performed in the scenario which represents a region within the South Zone of the city of Rio de Janeiro.

With increasing technological advancements more sophisticated mobile devices are being used by end-users. Third generation (3G) mobile communication systems such as Universal Mobile Telecommunication System (UMTS) are not able to satisfy the rising demand for higher throughputs and low latencies. New standards based on Orthogonal Frequency Division Multiplexing (OFDM), such as Long Term Evolution (LTE) and Worldwide Interoperability for Microwave Access (WiMAX), have been proposed and are currently being integrated into existing mobile networks all over the world. LTE specifications are being finalized within the 3rd Generation Partnership Project (3GPP) with the ambitious goals of increased spectral efficiency and end user throughput. Despite the introduction of several high data rate services, voice communication is still an essential part of the overall wireless wide area cellular communication market. In LTE, the core network is purely packet switched, thus voice is transmitted entirely using a Voice over Internet Protocol (VoIP). Like its predecessor standards it is desired that a large number of simultaneous VoIP calls be supported in LTE, while satisfying the desired Quality of Service (QoS) demands. This thesis examines issues related to VoIP capacity for LTE. One of the key challenges is the limited number of schedulable voice packets per sub frame. The main goal of this thesis is to quantify the impact of this limitation. After describing basic LTE concepts, a detailed description of the control channel resource limitations for the scheduling of voice packets is presented. Consequences of these limitations are explained systematically by presenting the problem in a wider context. Simulation results were obtained using the openWNS Simulator, an event driven system level simulation platform developed at the Communication Networks Research Group (ComNets), RWTH Aachen University Germany. Results are presented showing the impact of different scheduling strategies on VoIP capacity. These results illustrate how the limited control channel resources, specifically the Physical Downlink Control Channel (PDCCH) resources, affect the total number of schedulable VoIP user audio media streams. / Med ökande tekniska framsteg mer avancerade mobila enheter som används av slutanv ändarna. Tredje generationens (3G) mobila kommunikationssystem såsom Universal Mobile Telecommunication System (UMTS) inte kan tillgodose den ökande efterfrågan på högre genomströmning och låga latenser. Nya standarder som bygger på Orthogonal Frequency Division Multiplexing (OFDM), såsom Long Term Evolution (LTE) och Worldwide Interoperability för Microwave Access (WiMAX), har föreslagits och håller på att integreras I befintliga mobilnät över hela världen. LTE specifikationer håller på att färdigställas inom 3rd Generation Partnership Project (3GPP) med de ambitiösa målen om ökad spektral effektivitet och slutanvändare genomstr ömning. Trots införandet av flera tjänster av hög datahastighet, är röstkommunikation fortfarande en väsentlig del av den totala Wireless Wide Area cellulär kommunikation marknaden. I LTE är kärnnätet rent paketförmedlande därmed röst överförs helt och hållet med hjälp av en Voice over Internet Protocol (VoIP). Precis som sina föregångare standarder är det önskvärt att ett stort antal samtidiga VoIP samtal få stöd i LTE, samtidigt som det uppfyller önskade Quality of Service (QoS) krav. Denna avhandling undersöker frågor relaterade till VoIP kapacitet för LTE. En av de viktigaste utmaningarna är det begränsade antalet schemaläggningsbart röst paket per sub ram. Det huvudsakliga målet med denna avhandling är att kvantifiera effekterna av denna begränsning. Efter att ha beskrivit de grundläggande LTE begrepp, är en detaljerad beskrivning av de resurser kontroll kanal begränsningar för schemaläggning av röst paket presenteras. Konsekvenser av dessa begränsningar förklaras systematiskt genom att presentera problemet i ett större sammanhang. Simulering resultat erhölls med hjälp av openWNS Simulator, en händelse driven systemnivå simulering som utvecklats vid Communication Networks Research Group (ComNets), RWTH Aachen University Tyskland. Resultat presenteras som visar effekterna av olika schemaläggning strategier för VoIP kapacitet. Dessa resultat illustrerar hur de begränsade kontroll kanalresurser, särskilt fysiskt Downlink (PDCCH) resurser, påverkar det totala antalet schemaläggningsbart VoIP användare ljud mediaströmmar.

<p>Next-generation (Next-Gen) mobile applications, Extended Reality (XR), which encompasses Virtual/Augmented/Mixed Reality (VR/AR/MR), promise to revolutionize how people interact with technology and the world, ushering in a new era of immersive experiences. However, the hardware capacity of mobile devices will not grow proportionally with the escalating resource demands of the mobile apps due to their battery constraint. To bridge the gap, edge computing has emerged as a promising approach. It is further boosted by emerging 5G cellular networks, which promise low latency and high bandwidth. However, realizing the full potential of edge computing faces several fundamental challenges.</p> <p><br></p> <p>In this thesis, we first discuss a set of fundamental design challenges in supporting Next-Gen mobile applications via edge computing. These challenges extend across the three key system components involved — mobile clients, edge servers, and cellular networks. We then present how we address several of these challenges, including (1) how to coordinate mobile clients and edge servers to achieve stringent QoE requirements for Next-Gen apps; (2) how to optimize energy consumption of running Next-Gen apps on mobile devices to ensure long-lasting user experience; and (3) how to model and generate control-plane traffic of cellular networks to enable innovation on mobile network architectural design to support Next-Gen apps not only over 4G but also over 5G and beyond.</p> <p><br></p> <p>First, we present how to optimize the latency in edge-assisted XR system via the mobile-client and edge-server co-design. Specifically, we exploit key insights about frame similarity in VR to build the first multiplayer edge-assisted VR design, Coterie. We demonstrate that compared with the prior work on single-player VR, Coterie reduces the per-player network load by 10.6X−25.7X, and can easily support 4 players for high-quality VR apps on Pixel 2 over 802.11ac running at 60 FPS and under 16ms responsiveness without exhausting the finite wireless bandwidth.</p> <p><br></p> <p>Second, we focus on the energy perspective of running Next-Gen apps on mobile devices. We study a major limitation of a classic and de facto app energy management technique, reactive energy-aware app adaptation, which was first proposed two decades ago. We propose, design, and validate a new solution, the first proactive energy-aware app adaptation, that effectively tackles the limitation and achieves higher app QoE while meeting a given energy drain target. Compared with traditional approaches, our proactive solution improves the QoE by 44.8% (Pixel 2) and 19.2% (Moto Z3) under low power budget.</p> <p><br></p> <p>Finally, we delve into the third system component, cellular networks. To facilitate innovation in mobile network architecture to better support Next-Gen apps, we characterize and model the control-plane traffic of cellular networks, which has been mostly overlooked by prior work. To model the control-plane traffic, we first prove that traditional probability distributions that have been widely used for modeling Internet traffic (e.g., Poisson, Pareto, and Weibull) cannot model the control-plane traffic due to the much higher burstiness and longer tails in the cumulative distributions of the control-plane traffic. We then propose a two-level state-machine-based traffic model based on the Semi-Markov model. We finally validate that the synthesized traces by using our model achieve small differences compared with the real traces, i.e., within 1.7%, 4.9% and 0.8%, for phones, connected cars, and tablets, respectively. We also show that our model can be easily adjusted from LTE to 5G, enabling further research on control-plane design and optimization for 4G/5G and beyond.</p>

Open Radio Access Networks (Open RANs) enable flexible cellular network deployments by adopting open-source software and white-box hardware to build reference architectures customizable to innovative target use cases. The Open Radio Access Network (O-RAN) Alliance defines specifications introducing new Radio Access Network (RAN) Intelligent Controller (RIC) functions that leverage open interfaces between disaggregated RAN elements to provide precise RAN control and monitoring capabilities using applications called xApps and rApps. Multiple xApps targeting novel use cases have been developed by the O-RAN Software Community (OSC) and incubated on the Near-Real-Time RIC (Near-RT RIC) platform. However, the Near-RT RIC has, so far, been demonstrated to support only a single xApp capable of controlling the RAN elements. This work studies the scalability of the OSC Near-RT RIC to support simultaneous control signaling by multiple xApps targeting the RAN element. We particularly analyze its internal message routing mechanism and experimentally expose the design limitations of the OSC Near-RT RIC in supporting simultaneous xApp control. To this end, we extend an existing open-source RAN slicing xApp and prototype a slice-aware User Equipment (UE) admission control xApp implementing the RAN Control E2 Service Model (E2SM) to demonstrate a multi-xApp control signaling use case and assess the control routing capability of the Near-RT RIC through an end-to-end O-RAN experiment using the OSC Near-RT RIC platform and an open-source Software Defined Radio (SDR) stack. We also propose and implement a tag-based message routing strategy for disambiguating multiple xApps to enable simultaneous xApp control. Our experimental results prove that our routing strategy ensures 100% delivery of control messages between multiple xApps and E2 Nodes while guaranteeing control scalability and xApp non-repudiation. Using the improved Near-RT RIC platform, we assess the security posture and resiliency of the OSC Near-RT RIC in the event of volumetric application layer Denial of Service (DoS) attacks exploiting the E2 interface and the E2 Application Protocol (E2AP). We design a DoS attack agent capable of orchestrating a signaling storm attack and a high-intensity resource exhaustion DoS attack on the Near-RT RIC platform components. Additionally, we develop a latency monitoring xApp solution to detect application layer signaling storm attacks. The experimental results indicate that signaling storm attacks targeting the E2 Terminator on the Near-RT RIC cause control loop violations over the E2 interface affecting service delivery and optimization for benign E2 Nodes. We also observe that a high-intensity E2 Setup DoS attack results in unbridled memory resource consumption leading to service interruption and application crash. Our results also show that the E2 interface at the Near-RT RIC is vulnerable to volumetric application layer DoS attacks, and robust monitoring, load-balancing, and DoS mitigation strategies must be incorporated to guarantee resiliency and high reliability of the Near-RT RIC. / Master of Science / Telecommunication networks need sophisticated controllers to support novel use cases and applications. Cellular base stations can be managed and optimized for better user experience through an intelligent radio controller called the Near-Real-Time Radio Access Network (RAN) Intelligent Controller (RIC) (Near-RT RIC), defined by the Open Radio Access Network (O-RAN) Alliance. This controller supports simultaneous connections to multiple base stations through the E2 interface and allows simple radio applications called xApps to control the behavior of those base stations. In this research work, we study the performance and behavior of the Near-RT RIC when a malicious or compromised base station tries to overwhelm the controller through a Denial of Service (DoS) attack. We develop a solution to determine the application layer communication delay between the controller and the base station to detect potential attacks trying to compromise the functionality and availability of the controller. To implement this solution, we also upgrade the controller to support multiple radio applications to interact and control one or more base stations simultaneously. Through the developed solution, we prove that the O-RAN Software Community (OSC) Near-RT RIC is highly vulnerable to DoS attacks from malicious base stations targeting the controller over the E2 interface.

The proliferation of modern wireless networks increases demand for high capacity and throughput in order to provide faster, more robust, efficient and broadband services to end users. Mobile WiMAX and LTE are examples of such networks in which for some cases they have exposed limited connectivity due to harsh environment. Relay stations are preferred to overcome problems of weak or no access for such network devices, that are placed in specific positions to maintain high quality of data transfer at low cost and provide the required connectivity anywhere anytime. These stations should be equipped with an antenna system capable of establishing communication between base station (backhaul link) and end users (access link). This thesis focuses on the design and development of a new antenna system that is suitable for a relay-based wireless network. Planar geometries of microstrip patch antennas are utilized. The antenna system comprises two antenna modules: a new design of a single antenna for access link and a new design of an antenna array for backhaul link realization. Both antenna specifications are compatible with the IEEE802.16j protocol standard. Hence, relay station should be capable of pointing its radiation pattern to the base station antenna, thus to achieve the desired radiation pattern of the relay station, a new beam-forming module is proposed, designed and developed to generate the proper radiation pattern. The beam-forming module incorporating digital phase shifters and attenuator chips is fabricated and tested. The optimization process using the Least Mean Square (LMS) algorithm is considered in this study to assign the proper phase and amplitude that is necessary to each radiation element excitation current, to produce the desired steered radiation pattern. A comprehensive study on the coupling effects for several relative positions between two new backhaul and access link antenna elements is performed. Two new antenna configurations for coupling reduction are tested and the simulated and measured results in terms of antenna radiation performances were compared and commented.

Several UE energy consumption optimization techniques have been proposed for Machine Type Communication (MTC) devices. Extended Discontinuous Reception (eDRX) in idle mode is one such technique wherein an UE in idle mode wakes up only during its Paging Occasion (PO) to monitor paging messages from eNodeB (eNB). The PO is located within a Paging frame (PF). The PF is a function of System Frame Number (SFN) cycle of eNB. The paging messages may be sent asynchronously from multiple eNBs to a UE. Due to asynchronous operation of eNBs, SFN takes on different values at a given point in time and therefore a paging message is transmitted at different points in time from different eNBs. Due to this SFN misalignment between eNBs, an idle mode UE might receive and respond to the same paging message from different eNBs and/or miss a PO and thus the paging message. Due to this spread in time of SFN and PO, the actual handling of paging message by the UE becomes inefficient leading to increased UE energy consumption and decreased reachability. These issues, resulting from paging handling, will get amplified further if DRX period is extended longer (eDRX). In this study, we investigate the impact of eDRX cycles and mobility related parameters such as UE speed, cell size and size of SFN misalignment between eNBs on UE energy consumption, use of network resources and UE reachability. Receiving and responding to the same paging message results in increased energy consumption for UE and increased signaling between UE and the network. Missing a PO results in delayed paging reception and hence decreases UE reachability. As the DRX cycle lengths are increased from existing maximum of 2.56 seconds to 10.24 seconds and beyond, we see a reduction in UE energy consumption by more than 90%, but the network signaling and the delay to reach the UE increases linearly as a function of the DRX cycle length. We observe that the number of duplicate paging message receptions/missed POs is minuscule for DRX cycle lengths below 10.24 sec. At DRX cycle length of 10.24 seconds, UEs travelling across 500 m cell radius at speeds of 3, 50, 100 km/h the percentage of duplicate paging receptions are 0.07, 0.11, and 0.15 respectively. This duplicate paging message reception increases the UE energy consumption by 2.31, 6.15 and 12 percent of the total energy units respectively. Similarly, UE misses nearly 0.34, 0.39, and 0.405 percent of the total POs respectively. Depending on the number of consecutive PO misses, the UE reachability decreases. But by reducing the size of SFN misalignment between eNBs, we see that it’s possible to increase the reachability for UEs in eDRX. Further we have proposed solutions based on our analytical study to avoid duplicate paging message reception by UE, increase UE reachability and also reduce UE energy consumption using a windowing technique. We conclude that when a UE is configured with eDRX cycles, the tradeoff between battery lifetimes and UE reachability is based on mobility characteristics and service requirements.

Sharing a band of frequencies in the radio spectrum among multiple wireless systems has emerged as a viable solution for alleviating the severe capacity crunch in next-generation wireless mobile networks such as 5th generation mobile networks (5G). Spectrum sharing can be achieved by enabling multiple wireless systems to coexist in a single spectrum band. In this dissertation, we discuss the following coexistence problems in spectrum bands that have recently been raising notable research interest: 5G and Fixed Satellite Service (FSS) at 27.5-28.35 GHz (28 GHz); 5G and Fixed Service (FS) at 71-76 GHz (70 GHz); vehicular communications and Wi-Fi at 5.85-5.925 GHz (5.9 GHz); and mobile broadband communications and radar at 3.55-3.7 GHz (3.5 GHz). The results presented in each of the aforementioned parts show comprehensively that the coexistence methods help achieve spectrum sharing in each of the bands, and therefore contribute to achieve appreciable increase of bandwidth efficiency. The proposed techniques can contribute to making spectrum sharing a viable solution for the ever evolving capacity demands in the wireless communications landscape. / Ph. D. / Sharing a band of frequencies in the radio spectrum among multiple wireless systems has emerged as a viable solution for alleviating the severe capacity crunch in next-generation wireless mobile networks such as 5th generation mobile networks (5G). Spectrum sharing can be achieved by enabling multiple wireless systems to coexist in a single spectrum band. In this dissertation, we discuss the following coexistence problems in spectrum bands that have recently been raising notable research interest: 5G and Fixed Satellite Service (FSS) at 27.5-28.35 GHz (28 GHz); 5G and Fixed Service (FS) at 71-76 GHz (70 GHz); vehicular communications and Wi-Fi at 5.85-5.925 GHz (5.9 GHz); and mobile broadband communications and radar at 3.55-3.7 GHz (3.5 GHz). The results presented in each of the aforementioned parts show comprehensively that the coexistence methods help achieve spectrum sharing in each of the bands, and therefore contribute to achieve appreciable increase of bandwidth efficiency. The proposed techniques can contribute to making spectrum sharing a viable solution for the ever evolving capacity demands in the wireless communications landscape.