This bachelor thesis explores the threat of Stingrays, fake cell towers, to the mobile network. The increasing availability of open-source technology and hardware has made it easier to build Stingrays. Stingrays can threaten the privacy and security of individuals and their devices, making it critical to understand the effectiveness and practicalities of the attack. This study evaluates the feasibility and the practical danger of Stingrays using open-source software and available hardware, filling a gap in research on the subject. First, a literature study was made to understand the mobile network, security vulnerabilities and existing countermeasures to achieve this. Thereon, a Stingray was constructed, and attacks were simulated with different settings and scenarios to determine their practical and effective use. The results show the possibility of Stingray attacks with the mentioned equipment, but underline the need for a more advanced system for real-world attacks. / Denna kandidatuppsats utforskar hotet från Stingrays, falska mobiltorn, på mobilnätet. Den ökande tillgängligheten av öppen-källkod teknologi och hårdvara har gjort det lättare att bygga Stingrays. Stingrays kan hota integriteten och säkerheten av individer och deras enheter, vilket gör det avgörande att förstå effektiviteten och praktikaliteter av attacken. Studiens mål är att utvärdera möjligheten och den praktiska faran med Stingrays genom att använda programvara med öppen källkod och tillgänglig hårdvara, vilket fyller en lucka i forskning inom ämnet. Först gjordes en litteraturstudie för att förstå mobila nätverket, säkerhetssårbarheter och befintliga motåtgärder för att uppnå detta. Därefter konstruerade vi en Stingray och simulerade attacker med olika inställningar och i olika scenarier för att avgöra deras praktiska och effektiva användning. Resultaten visar möjligheten av Stingray-attacker med den nämnda utrustningen men understryker behovet av ett mer advancerat system för verkliga attacker.

The usage of UAVs (Unmanned Aircraft Vehicle) is soaring, not just for hobbyists but increasingly for a range of professional and civil applications. Some of the more sophisticated applications that have high data usage and long-range flight requirements are being developed now. The range and capability of typical wireless connectivity technologies are not enough for such applications. Connecting UAVs to the mobile network is a solution. There are lots of benefits which mobile network can provide for UAVs and UTM (Unmanned Aircraft System Traffic Management). However, the anticipation of UAVs was not considered at first in network planning, which creates unexpected coverage conditions. The introduction of UAVs impacts LTE (Long Term Evolution) network in several ways and the network coverage and capacity of UAVs at low altitude is significantly different from that of terrestrial UEs. The thesis work includes investigation about how UAVs impact LTE network and how mobile network coverage and capacity for UAVs change when other factor changes. The impact of methods to enhance the mobile network for UAVs would also part of the research. In this work, a successful simulation in order to investigate UAV’s situation while using 4G LTE cellular networks is developed. In order to properly test the developed framework for a range of different inputs, various generic scenarios were successfully developed and executed. Using this simulation, we have shown that UAV’s network situation is affected by 2 parameters: the height of UAV and the load of the eNodeBs (Evolved Node B). We have successfully demonstrated that UAV at higher attitude may cause more serious network condition in the suburban area compared with the case in the urban area. Finally, an interference mitigation technique: antenna beam selection is applied and tested. We show that it can improve the network condition for UAV at a higher altitude. Some improvements to the model could be a modeling of inter-cell interference and multipath effects. Models of weather condition in UAV’s flying space would also greatly improve the framework. Besides a scheme for modulation and bit error calculation could be used to build a more generic model. In the thesis, antenna propagation and gain models are not perfect, so more accurate model would also be a great improvement. Only antenna beam selection is tested in this thesis and the implementation does not include antenna mechanical design and model building. For further research, more methods like interference cancellation, power control and inter-cell interference coordination can be tested in both simulation and hardware. / Användningen av UAV(Unmanned Aircraft Vehicle): er är stigande, inte bara för hobbyister utan allt mer för en rad professionella och civila applikationer. Några av de mer sofistikerade applikationerna som har hög dataanvändning och krav på lång räckvidd utvecklas nu. Räckvidden och kapaciteten för typiska trådlösa anslutningstekniker räcker inte för sådana applikationer. Att ansluta UAV: er till mobilnätet är en lösning. Det finns många fördelar som mobilnätet kan ge för UAV: er och UTM (Unmanned Aircraft System Traffic Management). Förväntningen på UAV: er beaktades dock inte först i nätverksplanering, vilket skapar oväntade täckningsförhållanden.Införandet av UAV: er påverkar LTE-nätverk (Long Term Evolution) på flera sätt och nätverkets täckning och kapacitet för UAV: er på låg höjd skiljer sig väsentligt från markbundna UE: er.Examensarbetet inkluderar utredning om hur UAV: er påverkar LTE-nätverk och hur mobilnätstäckning och kapacitet för UAV: er förändras när andra faktorer ändras. Effekten av metoder för att förbättra mobilnätverket för UAV: er skulle också vara en del av forskningen. I detta arbete utvecklas en framgångsrik simulering för att undersöka UAV: s situation med användning av 4G LTE-mobilnät. För att korrekt testa det utvecklade ramverket för en rad olika ingångar, utvecklades och genomfördes olika generiska scenarier. Med denna simulering har vi visat att UAVs nätverkssituation påverkas av två parametrar: UAV: s höjd och belastningen på eNodeBs (Evolved Node B). Vi har framgångsrikt visat att UAV vid högre inställning kan orsaka allvarligare nätverkstillstånd i förortsområdet jämfört med fallet i stadsområdet. Slutligen tillämpas och testas en interferensbegränsande teknik: val av antennstråle. Vi visar att det kan förbättra nätverksvillkoret för UAV på högre höjd. Några förbättringar av modellen kan vara modellering av inter-cellstörningar och flervägseffekter. Modeller av väderförhållanden i UAV: s flygutrymme skulle också förbättra ramverket kraftigt. Förutom ett schema för modulering och beräkning av bitfel skulle kunna användas för att bygga en mer generisk modell. I avhandlingen är antennutbredningsoch förstärkningsmodeller inte perfekta, så en mer exakt modell skulle också vara en stor förbättring. Endast val av antennstråle testas i denna avhandling och implementeringen inkluderar inte antennmekanisk design och modellbyggnad. För ytterligare forskning kan fler metoder som interferensavbrott, effektkontroll och inter-cell-interferenskoordination testas i både simulering och hårdvara.

D. Tech. (Department of Process Control and Computer Systems, Faculty of Engineering and Technology), Vaal University of Technology. / In this research study, a scheme to minimise interference in converged mobile cellular networks (MCNs) and wireless sensor networks (WSNs) was designed and implemented. The focus was the mitigation of interference that arises when proximity service (ProSe)-enabled sensors engage in a device-to device (D2D) communication to alert smartphone users upon the detection of explosives at highly crowded areas like shopping malls. D2D is a technology that academia and industry experts believe will play a prominent role in the implementation of the next generation of mobile networks, specifically, the fifth generation (5G). However, the full roll out of D2D is being impeded by the interference that the technology introduces to the cellular network. D2D devices cause a significant amount of interference to the primary cellular network especially when radio resources are shared. In the downlink phase, primary user equipment is likely to suffer from interference emanating from a D2D transmitter. On the other hand, the immobile base station is affected by interference caused by the D2D transmitter in the uplink phase. This type of interference can be avoided or reduced if radio resources are allocated intelligently under strict coordination of the base station. An NP-hard optimisation problem was formulated and finding a solution to this problem in 1 ms is not possible. 5G has a frame structure duration of 10 ms with 10 subframes of 1 ms each. Heuristic algorithms were then developed to mitigate the interference affecting the primary network that could carry out resource allocation within the fast-scheduling period of 1 ms. Smartphones have progressed into devices capable of generating massive volumes of data. The challenge is that battery technology is not keeping up with the pace of smartphone technology, so any additional feature that designers want to add, is met with a lot of contempt from customers who are concerned about their smartphone batteries depleting rapidly. In this context, the strategy must be energy-efficient for smartphone users to embrace it. A system level simulator was developed using MATLAB to evaluate the efficacy of the proposed design. Extensive simulation results showed that ProSe-enabled sensors can safely be integrated into cellular networks participating in D2D communication with smart phones, without introducing significant harm to the primary cellular network. The results showed that after implementing the proposed strategy, overall user throughput decreased by 3.63 %. In cellular networks, this is a modest figure since a reduction of up to 5% is acceptable to both users and network providers. The figure generally capped in service level agreements signed between network providers and users is 5%. The proposed technique also resulted in a 0 % reduction in SINR of CUEs in a cellular network, according to the findings. In terms of D2D link throughput for different D2D transmit levels, the method proposed in this research work surpassed a similar scheme proposed in literature by an average of 18.3%.

This thesis presents the results of the development of a user-friendly computer code (in MATLAB) that can be used to calculate co-channel interferences, both in the downlink and in the uplink of a single satellite/space-based mobile communications system, due to the reuse of frequencies in spot beams or coverage cells. The analysis and computer code can be applied to any type of satellite or platform elevated at any height above earth. The cells or beams are defined in the angular domain, as measured from the satellite or the elevated platform, and cell centers are arranged in a hexagonal lattice. The calculation is only for a given instant of time for which the system parameters are input into the program. The results obtained in one program run are for the overall carrier to interference ratio (CIR) along with CIR for both the uplink and downlink paths. An overall carrier to noise plus interference ratio (CNIR) is also calculated, which exemplifies the degradation in the carrier to noise ratio (CNR) of the system. Comparisons for systems with differing system scenarios are also made. For example, overall CIRs are compared for different reuse numbers (3, 4, 7, and 13) in LEO and GEO satellite systems. In conclusion, as expected, it is observed that the co-channel interference generally increases as we decrease the reuse number employed for the frequency reuse in the cells. It is also observed that co-channel interference can cause substantial degradation to the overall CNR of a system. / Master of Science

當發生大規模的地震或強烈的颱風等重大天然災害時，通訊系統常常隨著電力與交通系統的損毀而癱瘓。由歷年大型災變中多數災區內之行動通訊系統全面中斷即可印證行動通訊系統其實是極為脆弱的，然而有效運作的通訊系統卻是災情傳遞、資源調度及救災是否順利的關鍵因素。本文所探討的應急通訊系統利用倖存的連通基地台和斷訊卻沒有損毀的基地台，以無線電連接起來建構一個臨時性的通訊系統，稱為應急蜂巢式行動通訊網路(Contingency Cellular Network，CCN)。由於各地災情狀況不完全相同，CCN的建構順序必須考慮災區的輕重緩急、時間的急迫等因素依序建構。因此當CCN拓樸規劃完成後，根據CCN拓樸、各地災情嚴重程度以及拓樸中基地台間的相對距離(運輸時間)進行基地台建構排程規劃，以達到最大的總救災效益。 本文考慮各基地台所能發揮的救災效益、所需建構時間、以及運輸工具從任一基地台到另一基地台所需運輸時間，提出兩個適合CCN拓樸樹狀結構的考慮資源運輸路徑之最佳化排程模型CCNDS-AC和CCNDS-UC。CCNDS-AC限制建構順序必須從連網台往下循序建構，但CCN-UC則否。因發生突發性大型天然災害時，可容許的計算時間相當短暫，因此提出了兩個快速的啟發式演算法DS-ACG與DS-UCB，可在短時間內求出一組相當逼近於最佳解的建構排程順序，與DS-UCB相互比較。本文以電腦模擬的方式進行小規模實驗與大規模實驗評估，並且用Genetic Algorithm來比較啟發式演算法的效能。結果顯示DS-UCB明顯優於DS-ACG及Genetic Algorithm。在小規模實驗中DS-UCB可求得與最佳解的總救災效益誤差平均約0.9%的近似最佳解建構順序。而在大規模實驗下， DS-UCB與十萬個解中的最佳解─pseudo optimal solution相較，總救災效益平均高出約16.7%，而總救災時間平均約少了19.4%。 / When stricken by a large-scale disaster, the efficiency of disaster response operation is very critical to life saving. However, cellular networks were usually crashed in earthquake, typhoons or other natural disasters due to power outage or backhaul breakage. Unfortunately, the efficiency of communication system is a critical factor to the success of disaster response operation. We designed a contingency cellular network (CCN) by connecting physically intact but service-disrupted base stations together with wireless links. Since the transportation capacity may be very limited, scheduling of CCN deployment order according to the demand of disaster operation and traveling time between base stations becomes an important issue. We propose two optimization models: CCN Deployment Scheduling Antecessor Constrained Problem (CCNDS-AC) and CCN Deployment Scheduling Unconstrained Problem (CCNDS-UC), aiming to maximize the efficiency of disaster response operation. Both problems are proven to be NP Hard. We also designed two rapid heuristic algorithms, DS-ASG and DS-UCB to solve the problems respectively when it is needed in urgent. Finally, we evaluated the proposed algorithms against optimal solutions (in small cases only) as well as genetic algorithm by simulation. The experimental results show that DS-UCB outperforms all other algorithms. In small scale cases, the profit obtained by DS-UCB is only 0.9% smaller than what the optimum solution can get. In large scale cases, as compared to the pseudo optimum solution, which is the best solution among 100,000 solutions, DS-UCB outperforms pseudo optimum solutions in profit by 16.7%, and in traveling time by 19.4%, both in average.

The next generation wireless networks i.e. 5G aim to provide multi-Gbps data traffic, in order to satisfy the increasing demand for high-definition video, among other high data rate services, as well as the exponential growth in mobile subscribers. To achieve this dramatic increase in data rates, current research is focused on improving the capacity of current 4G network standards, based on Long Term Evolution (LTE), before radical changes are exploited which could include acquiring additional/new spectrum. The LTE network has a reuse factor of one; hence neighbouring cells/sectors use the same spectrum, therefore making the cell edge users vulnerable to inter-cell interference. In addition, wireless transmission is commonly hindered by fading and pathloss. In this direction, this thesis focuses on improving the performance of cell edge users in LTE and LTE-Advanced (LTE-A) networks by initially implementing a new Coordinated Multi-Point (CoMP) algorithm to mitigate cell edge user interference. Subsequently Device-to-Device (D2D) communication is investigated as the enabling technology for maximising Resource Block (RB) utilisation in current 4G and emerging 5G networks. It is demonstrated that the application, as an extension to the above, of novel power control algorithms, to reduce the required D2D TX power, and multihop transmission for relaying D2D traffic, can further enhance network performance. To be able to develop the aforementioned technologies and evaluate the performance of new algorithms in emerging network scenarios, a beyond-the-state-of-the-art LTE system-level simulator (SLS) was implemented. The new simulator includes Multiple-Input Multiple-Output (MIMO) antenna functionalities, comprehensive channel models (such as Wireless World initiative New Radio II i.e. WINNER II) and adaptive modulation and coding schemes to accurately emulate the LTE and LTE-A network standards. Additionally, a novel interference modelling scheme using the 'wrap around' technique was proposed and implemented that maintained the topology of flat surfaced maps, allowing for use with cell planning tools while obtaining accurate and timely results in the SLS compared to the few existing platforms. For the proposed CoMP algorithm, the adaptive beamforming technique was employed to reduce interference on the cell edge UEs by applying Coordinated Scheduling (CoSH) between cooperating cells. Simulation results show up to 2-fold improvement in terms of throughput, and also shows SINR gain for the cell edge UEs in the cooperating cells. Furthermore, D2D communication underlaying the LTE network (and future generation of wireless networks) was investigated. The technology exploits the proximity of users in a network to achieve higher data rates with maximum RB utilisation (as the technology reuses the cellular RB simultaneously), while taking some load off the Evolved Node B (eNB) i.e. by direct communication between User Equipment (UE). Simulation results show that the proximity and transmission power of D2D transmission yields high performance gains for a D2D receiver, which was demonstrated to be better than that of cellular UEs with better channel conditions or in close proximity to the eNB in the network. The impact of interference from the simultaneous transmission however impedes the achievable data rates of cellular UEs in the network, especially at the cell edge. Thus, a power control algorithm was proposed to mitigate the impact of interference in the hybrid network (network consisting of both cellular and D2D UEs). It was implemented by setting a minimum SINR threshold so that the cellular UEs achieve a minimum performance, and equally a maximum SINR threshold to establish fairness for the D2D transmission as well. Simulation results show an increase in the cell edge throughput and notable improvement in the overall SINR distribution of UEs in the hybrid network. Additionally, multihop transmission for D2D UEs was investigated in the hybrid network: traditionally, the scheme is implemented to relay cellular traffic in a homogenous network. Contrary to most current studies where D2D UEs are employed to relay cellular traffic, the use of idle nodes to relay D2D traffic was implemented uniquely in this thesis. Simulation results show improvement in D2D receiver throughput with multihop transmission, which was significantly better than that of the same UEs performance with equivalent distance between the D2D pair when using single hop transmission.

Face à l'explosion du trafic mobile entraînée par le succès des smartphones, les opérateurs de réseaux mobiles (MNOs) densifient leurs réseaux à travers le déploiement massif des stations de base à faible portée (SBS), capable d’offrir des services très haut débit et de remplir les exigences de capacité et de couverture. Cette nouvelle infrastructure, appelée réseau cellulaire hétérogène (HetNet), utilise un mix de stations de base hiérarchisées, comprenant des macro-cellule à forte puissance et des SBS à faible puissance.La prolifération des HetNets soulève une nouvelle préoccupation concernant leur consommation d'énergie et empreinte carbone. Dans ce contexte, l'utilisation de technologies de production d'énergie dans les réseaux mobiles a suscité un intérêt particulier. Les sources d'énergie respectueuses de l'environnement couplées à un système de stockage d'énergie ont le potentiel de réduire les émissions carbone ainsi que le coût opérationnel énergétique des MNOs.L'intégration des énergies renouvelables (panneau solaire) et du stockage d'énergie (batterie) dans un SBS gagne en efficacité grâce aux leviers technologiques et économiques apportés par le smart grid (SG). Cependant, l'architecture résultante, que nous appelons Green Small-Cell Base station (GSBS), est complexe. Premièrement, la multitude de sources d'énergie, le phénomène de viellissement du système et le prix dynamique de l'électricité dans le SG sont des facteurs qui nécessitent planification et gestion pour un fonctionnement plus efficace du GSBS. Deuxièmement, il existe une étroite dépendance entre le dimensionnement et le contrôle en temps réel du système, qui nécessite une approche commune capable de résoudre conjointement ces deux problèmes. Enfin, la gestion holistique d’un HetNet nécessite un schéma de contrôle à grande échelle pour optimiser simultanément les ressources énergétiques locales et la collaboration radio entre les SBSs.Par conséquent, nous avons élaboré un cadre d'optimisation pour le pré-déploiement et le post-déploiement du GSBS, afin de permettre aux MNOs de réduire conjointement leurs dépenses d'électricité et le vieillissement de leurs équipements. L'optimisation pré-déploiement consiste en un dimensionnement du GSBS qui tient compte du vieillissement de la batterie et de la stratégie de gestion des ressources énergétiques. Le problème associé est formulé et le dimensionnement optimal est approché en s'appuyant des profils moyens (production, consommation et prix de l'électricité) à travers une méthode itérative basée sur le solveur non-linéaire “fmincon”. Le schéma de post-déploiement repose sur des capacités d'apprentissage permettant d'ajuster dynamiquement la gestion énergétique du GSBS à son environnement (conditions météorologiques, charge de trafic et coût de l'électricité). La solution s'appuie sur le fuzzy Q-learning qui consiste à combiner le système d'inférence floue avec l'algorithme Q-learning. Ensuite, nous formalisons un système d'équilibrage de charge capable d'étendre la gestion énergétique locale à une collaboration à l'échelle réseau. Nous proposons à ce titre un algorithme en deux étapes, combinant des contrôleurs hiérarchiques au niveau du GSBS et au niveau du réseau. Les deux étapes s'alternent pour continuellement planifier et adapter la gestion de l'énergie à la collaboration radio dans le HetNet.Les résultats de la simulation montrent que, en considérant le vieillissement de la batterie et l'impact mutuel de la conception du système sur la stratégie énergétique (et vice-versa), le dimensionnement optimal du GSBS est capable de maximiser le retour sur investissement. En outre, grâce à ses capacités d'apprentissage, le GSBS peut être déployé de manière plug-and-play, avec la possibilité de s'auto-organiser, d'améliorer le coût énergétique du système et de préserver la durée de vie de la batterie. / Pushed by an unprecedented increase in data traffic, Mobile Network Operators (MNOs) are densifying their networks through the deployment of Small-cell Base Stations (SBS), low-range radio-access transceivers that offer enhanced capacity and improved coverage. This new infrastructure – Heterogeneous cellular Network (HetNet) -- uses a hierarchy of high-power Macro-cell Base Stations overlaid with several low-power (SBSs).The augmenting deployment and operation of the HetNets raise a new crucial concern regarding their energy consumption and carbon footprint. In this context, the use of energy-harvesting technologies in mobile networks have gained particular interest. The environment-friendly power sources coupled with energy storage capabilities have the potential to reduce the carbon emissions as well as the electricity operating expenditures of MNOs.The integration of renewable energy (solar panel) and energy storage capability (battery) in SBSs gain in efficiency thanks to the technological and economic enablers brought by the Smart Grid (SG). However, the obtained architecture, which we call Green Small-Cell Base Station (GSBS), is complex. First, the multitude of power sources, the system aging, and the dynamic electricity price in the (SG) are factors that require design and management to enable the (GSBS) to efficiently operate. Second, there is a close dependence between the system sizing and control, which requires an approach to address these problems simultaneously. Finally, the achievement of a holistic management in a (HetNet) requires a network-level energy-aware scheme that jointly optimizes the local energy resources and radio collaboration between the SBSs.Accordingly, we have elaborated pre-deployment and post-deployment optimization frameworks for GSBSs that allow the MNOs to jointly reduce their electricity expenses and the equipment degradation. The pre-deployment optimization consists in an effective sizing of the GSBS that accounts for the battery aging and the associated management of the energy resources. The problem is formulated and the optimal sizing is approximated using average profiles, through an iterative method based on the non-linear solver “fmincon”. The post-deployment scheme relies on learning capabilities to dynamically adjust the GSBS energy management to its environment (weather conditions, traffic load, and electricity cost). The solution is based on the fuzzy Q-learning that consists in tuning a fuzzy inference system (which represents the energy arbitrage in the system) with the Q-learning algorithm. Then, we formalize an energy-aware load-balancing scheme to extend the local energy management to a network-level collaboration. We propose a two-stage algorithm to solve the formulated problem by combining hierarchical controllers at the GSBS-level and at the network-level. The two stages are alternated to continuously plan and adapt the energy management to the radio collaboration in the HetNet.Simulation results show that, by considering the battery aging and the impact of the system design and the energy strategy on each other, the optimal sizing of the GSBS is able to maximize the return on investment with respect to the technical and economic conditions of the deployment. Also, thanks to its learning capabilities, the GSBSs can be deployed in a plug-and-play fashion, with the ability to self-organize, improve the operating energy cost of the system, and preserves the battery lifespan.

Les systèmes embarqués tels que les téléphones portables ou les lecteurs multimédia intègrent de plus en plus de fonctions consommatrices d'énergie ce qui a pour conséquence directe une diminution de leurs autonomies. Les applications audio dans les téléphones cellulaires et en particulier l'application casque font partie des fonctions les plus consommatrices d'énergie. Après un état de l'art des solutions permettant l'amplification de signaux audio, l'amplificateur de classe G à été identifié comme étant le meilleur candidat pour obtenir une amélioration du rendement tout en fournissant une bonne qualité de reproduction sonore. Nos travaux se sont plus particulièrement focalisés sur la détection d'enveloppe de ces architectures qui est un facteur clé dans la maximisation du rendement. Une étude des propriétés temporelles, fréquentielles et statistiques des signaux présents en entrée de l'amplificateur a ainsi été menée pour mettre en évidence les différences entre les signaux classiquement utilisés (signal sinusoïdal) et les signaux réellement écoutés par les utilisateurs (musique). Après avoir effectué une sélection de signaux pour la suite de notre étude, nous avons également caractérisé la puissance correspondant à des conditions normales d'écoute afin d'obtenir par la suite un environnement de test proche des conditions réelles de fonctionnement. Un modèle simplifié et rapide d'amplificateur hybride permettant d'obtenir en quelques dizaines de secondes, l'évaluation du rendement, de la consommation et de la qualité sonore dans des conditions réelles de fonctionnement a été développé. Notre modèle, entièrement configurable et réadaptable à d'autres types de circuits a été validé par mesures pratiques des performances d'un amplificateur existant. Les paramètres de la détection d'enveloppe de ce modèle ont fait l'objet d'une optimisation basée sur le couplage séquentiel de deux algorithmes d'optimisation, permettant ainsi dans un temps limité d'obtenir une solution optimale sans solution de départ sous des conditions réelles d'utilisation. La suite de notre étude nous a conduit à étudier, modéliser, optimiser et comparer des amplificateurs de classe G possédant un nombre de tensions d'alimentation supérieur (3, 4) ainsi que des amplificateurs de classe H (alimentations continues) afin d'améliorer encore le rendement. Enfin, nous avons proposé une nouvelle détection d'enveloppe permettant d'améliorer le rendement à faible puissance. Cette nouvelle détection d'enveloppe permet à l'amplificateur de classe G un fonctionnement en « multi niveau » et d'être auto adaptatif au signal audio présent en entrée de l'amplificateur. Après avoir développé des méta-modèles pour optimiser les paramètres de la détection d'enveloppe, cette détection d'enveloppe a été implémentée au niveau transistor en technologie 0.25μm de ST Microelectronics. / Embedded systems such as mobile phones, tablets and GPS incorporate an increasing number of electronic functions that generate a decrease in battery life. The aim of this work is to propose new solutions for audio amplifiers for the headphone application because this application has a large impact on battery autonomy. To improve the efficiency of actual amplifiers, a behavioral model of this kind of amplifier has been developed and validated by practical measures. This model, fast, accurate and reconfigurable allows in few seconds to evaluate the efficiency, consumption and quality of sound reproduction in real conditions of operation. Through the use of this model coupled with an optimizing method based on two algorithms, several architectures of level detector were studied and compared allowing to define the best compromise. A new architecture is then proposed, simulated and optimized in a 0.25μm technology from ST Microelectronics to demonstrate the feasibility of the solution.

大型自然災害會癱瘓通訊系統嚴重影響到救災效率，本論文旨在快速提出一個建構排程供應急通訊系統佈建。無線通訊系統的成熟極大的為使用者帶來便利性，但當發生大規模的地震或強烈颱風等重大天然災害時，通訊系統卻常常因架構原因，隨著電力與交通系統的損毀而癱瘓。由歷年大型災變中多數災區內之行動通訊系統全面中斷即可印證行動通訊系統其實是極為脆弱，而有效運作的通訊系統卻是災情傳遞、資源調度以及互助協調是否順利的關鍵因素。 本篇論文所探討的應急通訊系統是利用僅存的連通基地台和斷訊卻沒有損毀的基地台建構一個臨時性的網路，稱為應急蜂巢式行動網路(contingency cellular network，CCN)。由於災區的交通系統可能癱瘓，因此CCN的建構需視各種運輸能力而規劃，而各個地方受災情況不盡相同，CCN的建構順序也須辨明輕重緩急依序建構，網路拓樸的規劃是本研究團隊的另一研究主題，本文主在探討如何在網路拓樸已知情況下進行CCN建構排程以達到最大的救災效益，因此我們提出一適合CCN樹狀結構的最佳化排程模型，以追求救災效益的最大化，這些模型可供使用者(救災指揮單位)系統化的解決CCN建構排程問題。 模型包含CCN樹狀拓樸、基地台數目、基地台建構時間、基地台重要度、拓樸連線集合和建構工作組數。在此模型下提出一個考慮各基地台的時效性以及重要性而進行快速排程的演算法，此演算法透過計算排程總救災效益決定優劣。分三階段實驗。三階段實驗皆可在數秒內得出接近最佳解的排程。 / When stricken by a large-scale disaster, the efficiency of disaster response operation is very critical to life saving. We propose to build a contingency cellular network to support emergency communication in large scale natural disasters by connecting disconnected base stations. This paper addresses the deployment scheduling problem. The advance of mobile communication technologies has brought great convenience to users. Cellular phone becomes the first communication tool most people would use in emergency. However, cellular networks were usually crashed due to earthquake, typhoons or other natural disasters due to power outage or backhaul broken. Unfortunately, the efficiency of communication system is a critical factor to the success of disaster response operation such as resource allocation as well as coordination of rescue and relief operations. We designed a contingency cellular network (CCN) by connecting physically intact but service-disrupted base stations together with wireless links. As the disaster area's transport system may be paralyzed, the construction of CCN may have to rely on air transportation such as helicopter or even airdrop. Since the transportation capacity may be very limited, scheduling of CCN deployment order according to the demand of disaster operation becomes an important issue. We model the CCN Deployment Scheduling Problem into a combinatorics optimization problem aiming to maximize disaster operation efficiency. The problem is proven NP Hard. Thus, we design an efficient heuristic algorithm to solve the problem when it is needed in urgent.

歷年發生的大型天然災害中，行動通訊系統常常會因為道路、橋樑、電力的損毀而導致嚴重癱瘓，進而影響災後救援工作的進行，行動通訊系統其實是不可靠且極為脆弱的。為使災區能夠快速地恢復通訊，本研究提出一種應急通訊系統，利用無線通訊，將這些無連線能力的基地台連接起來，並利用存活可連至核心通訊網路的基地台，建構成為一個臨時性的通訊系統，稱為應急蜂巢式行動通訊網路(Contingency Cellular Network，CCN)，供使用者在災區內進行通訊。由於資料庫的可靠度在行動通訊網路中具有舉足輕重之地位，本論文旨在利用分散式架構提高CCN網路資料庫的可靠度，進而提高系統可靠度。我們先分析資料表的特性，並依據各資料表的特性以及資源之多寡，設計相應的分散式架構。 我們利用樹狀拓樸的簡單特性，提出三種分散式架構：(1)用於群組資料表的階層備援式架構、(2)用於HLR資料表的階層備援式架構，以及(3)用於HLR資料表的鄰近階層備援式架構。這三種架構都利用了樹狀拓樸的簡單特性，大幅簡化了資料庫的查詢及更新程序。我們以可用度及平均總成本，以評估各架構在不同的情形下之最合適架構，並觀察在各架構下，其系統可用度與平均總成本之間的關係，由結果可知，在群組資料表儲存架構中，若追求高系統可用度，可選擇高儲存密度之架構，反之，若追求較低的成本，可選擇低儲存密度之架構。而在HLR資料表儲存架構中，階層備援式的系統可用度與平均總成本比鄰近階層備援式來得高，表示階層備援式耗費較多成本，但可用度也較高，故在建置時可依實際情況來選擇合適的架構儲存。 最後，為驗證分散式資料庫架構之可行性，我們利用數部筆記型電腦及Android平台手機來建置階層備援式及鄰近階層備援式架構，並測量在此二種架構下於通話建立時所耗費的時間，從模擬結果可知，此二種架構皆可快速建置並可立即通訊，惟鄰近階層備援式所耗費的通話建立時間略長，但仍在可容許範圍之內。 / When stricken by a catastrophic natural disaster, the efficiency of disaster response operation is very critical to life saving. The efficiency of disaster response operation is greatly depending on communication systems. However, they were usually not dependable, including cellular networks, and often crashed due to power outage and backhaul link breakage. The failure of communication systems caused a big coordination problem to many disaster response operations. This thesis proposes a Contingency Cellular Network (CCN) by connecting isolated base stations to survival base stations using long-range wireless links to recover part of cellular network functionality. People can use their own cell phones for emergency communication in the disaster areas. CCN will be able to support a large number of disaster responders with limited resources in the early hours of disasters, thus to save many lives. Because the reliability of database plays a very important role in the CCN, this thesis proposes a distributed database architecture to improve the reliability of database so as the reliability of CCN. We take advantage of the simplicity of CCN tree topology to design three distributed database architectures: (1) Hierarchical Redundancy Architecture for “Group_Member ” table, (2) Hierarchical Redundancy Architecture for “HLR” table, and (3) Hierarchical Neighboring Redundancy Architecture for “HLR” table. The tree topology greatly simplified the query and update procedures. We use availability and average total cost to analytically evaluate all three architectures trying to identify the most appropriate architecture under different circumstances. Based on our evaluation results, CCN operators can choose the most appropriate architecture according to their realistic circumstances. Finally, in order to verify the feasibility of the proposed architectures, we implemented a simplified prototype using several laptops and Android mobile phones. The Hierarchical Redundancy Architecture and the Neighboring Redundancy Architecture were implemented. The results show that both architectures can be functional with reasonable performance except that Hierarchical Neighboring Redundancy Architecture may take longer time, but in a tolerable range, to setup a call.